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Advice needed on an Engine/Transmission swap. by Murcie-Me
Started on: 01-27-2025 12:02 AM
Replies: 40 (521 views)
Last post by: 1985 Fiero GT on 02-08-2025 12:11 AM
Murcie-Me
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Report this Post01-27-2025 12:02 AM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hello forum, my name is Michael and am new to this forum. I have been on other forums for many years (Mad Mechanics, Lamboclone, Kitcarhub) and have built many Lamborghini replicas using Fiero's as a base.
I built my (Murcielago) more than 14 years ago and it is still the most advanced replica to date. I have always loved Fieros. but back when they were in production I was just a poor college student and could never afford one.
I have always said I would NEVER do an engine swap in my build (86 SE 2.8L AT) unless I could do a swap that would make it sound more exotic. Without spending a fortune I know that will never happen, and I'm ok with it.
I would like to do a swap now though, and I need your advice on a few things. I'm thinking of going with an LZ9 engine from an '06 pontiac G6 or Chevrolet Impala. I see most people recommend using the Microsquirt engine management unless someone can point me to a better option.
Here are my questions:
1) will the LZ9 bolt up to my TH125, and will it handle the additional power (240HP)
2) Should i swap out the TH125 for a 4T60, and if so will my existing axels from the TH125 plug into the 4T60?
3) Will the Microsquirt also control the lockup function on the converter clutch?
4) If I go with a 4T65E instead (more readily available), what compatibility problems will I face?
I have a thousand more questions, but these are the ones I can't seem to find any info on.
I'm sorry if I posted this in the wrong topic, but i'm not sure where to post it. I realize there are many threads on engine swaps with 3800 and 3400 engines, but I can seem to find any of these questions addressed and advised.
Thank you in advance for any help you guys can offer.

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Report this Post01-27-2025 02:21 AM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm doing a 3400 turbo with f23 5 speed manual trans, with mega squirt 3 pro mini ECM, I wouldn't get micro squirt unless you only want very basic stuff, the 3 pro mini is not nearly as expensive as a full mega squirt, but has much more functionality than the micro squirt. These do not come pre programmed, however the basic get it running info is easy enough, download app, plug it into computer, enter engine parameters (size, cylinder numbers, firing order, ignition system type, what sensors are hooked up to what wires, etc.), and it will have basic example tables that can be changed to get what you need.

Micro squirt will be no easier to tune, and you can't run sequential fuel injection (each injector firing one at a time, in time with its cylinder) only batch/bank fire (all at same time, or each "bank" of 3 together), which makes it drive better at low rpms, but no effect on high rpms. Also more flexibility on the io with the mega squirt 3 pro mini.

(Disclaimer: I have not yet even installed my mega squirt, just played around in the software, and seen what other people say and do, it is going to be a lot of fiddling with numbers until it "feels" right, but there are instruction manuals for each of the ECU products, they describe things well, and seeing what other people have done makes everything easy enough to understand)
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Report this Post01-27-2025 03:08 AM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thank you for that info! I think I would want the sequential firing as opposed to the bank firing as long as its possible on the LZ9 engine. I will be doing the cam swap to eliminate the VVT, seems like it would be better that way.
So now I have to figure out the compatibility issues as far as mating the new LZ9 to the existing TH125. I feel the existing trans will handle the added H.P (somebody correct me if i'm wrong), and it would eliminate the possibility of having to have new axels made if I have to upgrade to a 4T60 (non "E") transmission. The reason I would go with the non-E version of the trans is because the only electric connection to it would be the TCC, the TV cable would control the shift timing just like the TH125. I could be wrong about that also, maybe the mega squirt can control the shift points of the 4T60"E" as well?
Like I said, this is all new to me and I am grateful for any insight and advice you guys can offer.
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Report this Post01-27-2025 07:39 AM Click Here to See the Profile for 82-T/A [At Work]Send a Private Message to 82-T/A [At Work]Edit/Delete MessageReply w/QuoteDirect Link to This Post
Are you telling me that the car in those pictures is a Fiero? That's amazing... the fit and finish is spectacular on that car! I've not spent a whole lot of time looking at that model, but I think unless I owned one, I would never be able to tell the difference. I've seen some pretty decent Fiero kit cars (looking like Ferraris or Lambos), and this is definitely right up there at the top. I am very impressed.


As for the swap, I'd basically echo everything that 1985 Fiero GT said about going with the 3400 series motor, of which the LZ9 is a member of. I'd personally shy away from the LZ9 simply because the VVT makes it a bit more complicated, and likely means you'd need to re-use the factory ECM. I'd probably go with the 3500 motor (the LZ4). These motors are AWESOME... they are also all 60 degree, which is considered to be a very optimal design for high-revving engines, even if GM didn't fully take advantage of it. You're not going to get insane / sick power from the LZ4 in a Fiero... but I don't think 260hp is unreasonable (with a LZ4) with a shorter exhaust, shorty headers, and using a much more direct cold-air intake that the Fiero has. Plus some mild port-matching. Here's a nice article on the LZ9 and LZ4: https://www.autoweek.com/ca...240-horse-cimarrons/

These engines won't have the V10 sound you're looking for... but they definitely sound really nice at higher RPMs.

I would also definitely get rid of the Th-125. It was a nice transmission for the time, but it does not do the engine justice, and isn't great on the highway if you want to cruise. I would go with either a 4T60 or 4T65E. You can purchase separate controllers for both of them from Summit Racing. Here's a great article from Sinister Performance on the transmission models: http://www.gmtuners.com/tech/440_4T60E_4T65E.htm


One other thing I want to mention... these engines were designed as Sequential-port Fuel Injection motors (SFI), as compared to our stock V6 motors, which are Multi-Port Fuel Injection. The difference of course is that SFI fires the injector for each specific cyl (just before valve opening), where as the MPFI motors dump fuel in a batch... meaning three injectors fire and the fuel may pool at the top of the valve while it's closed for half a second (or whatever it is). SFI is significantly more efficient than MPFI... and I recommend keeping SFI if you can.

At wide open throttle, there is essentially no difference because the valves are opening and closing so fast that it really doesn't make any perceivable difference. But in the lower RPMs (EDIT: lower to mid-rpms), SFI really shines. You'll get better low-end performance and around-town driving with SFI than you will with MPFI. Keep in mind, all of these engines switched to SFI back in 1993... so they were all designed with SFI in mind, and are rated based on an SFI configuration. It makes the car a better-driving car in around-town driving, and makes it a bit more responsive. You also get better fuel economy and emissions for whatever that's worth.

There are a couple of aftermarket systems that support SFI, but if you're going to go with the Microsquirt/Megasquirt, you'll want to go with the MegaSquirt 3 Pro... as it's one of the only ones that supports SFI.

[This message has been edited by 82-T/A [At Work] (edited 01-27-2025).]

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Report this Post01-27-2025 10:31 AM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 82-T/A [At Work]:

There are a couple of aftermarket systems that support SFI, but if you're going to go with the Microsquirt/Megasquirt, you'll want to go with the MegaSquirt 3 Pro... as it's one of the only ones that supports SFI.



Yeah micro squirt only has 2 injector outputs, but it does cost $300, the mega squirt 3 pro mini has 8 injector outputs (the 2 unused ones can be used for anything, turbo wastegate control, air conditioning, TCC lockup, etc.), it costs $600:
https://www.diyautotune.com/product/ms3pro-mini
It also claims vvt control, so you should look into what that would require, and how that would work in your specific application. One thing to make sure of, this ECM will only work with PWM IAC valves, I don't know what the lz9 has, but if it is a 4 wire stepper motor (like Fiero) then you'll have to get it working with a seperate PWM IAC valve.
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Report this Post01-27-2025 01:01 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 82-T/A [At Work]:

Are you telling me that the car in those pictures is a Fiero? That's amazing... the fit and finish is spectacular on that car! I've not spent a whole lot of time looking at that model, but I think unless I owned one, I would never be able to tell the difference. I've seen some pretty decent Fiero kit cars (looking like Ferraris or Lambos), and this is definitely right up there at the top. I am very impressed.




Thank you 82-T/A, yes its actually an '86 SE Fiero. The entire Fiero body was removed, the chassis was stretched at the engine cradle mounts, and then a new body frame applied to mount all the panels to. I was a lot of work, took me 14 months and $38k from start to finish.

Yes the LZ9 is a VVT engine, but that can be eliminated with a different cam which I intend to do.
Do you know if the 4T60 trans is the same size as the TH125? When I did the Lamborghini build I put wide track suspension on the car, which meant I had to have custom HD axels built to be longer and adapt the TH125 to corvette C4 hubs. Since it was $1200 for the pair, i'd like to not have to do that again. If the 4T60 is the same dimension as the 125 and accepts the same CV joints it'll save a lot of headaches and money.

So when the mega is installed, do I no longer need the original ECU from the Fiero?
From what i've read in other articles, it doesn't seem to be a big deal to wire the mega squirt to the engine, but do I have to make my own harness?

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Report this Post01-27-2025 01:28 PM Click Here to See the Profile for 82-T/A [At Work]Send a Private Message to 82-T/A [At Work]Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:
Thank you 82-T/A, yes its actually an '86 SE Fiero. The entire Fiero body was removed, the chassis was stretched at the engine cradle mounts, and then a new body frame applied to mount all the panels to. I was a lot of work, took me 14 months and $38k from start to finish.

Yes the LZ9 is a VVT engine, but that can be eliminated with a different cam which I intend to do.
Do you know if the 4T60 trans is the same size as the TH125? When I did the Lamborghini build I put wide track suspension on the car, which meant I had to have custom HD axels built to be longer and adapt the TH125 to corvette C4 hubs. Since it was $1200 for the pair, i'd like to not have to do that again. If the 4T60 is the same dimension as the 125 and accepts the same CV joints it'll save a lot of headaches and money.


So, the swap is easy, and the 4T60 will mate up directly to the engine no problem... it's the same bell housing. Here's an article (I stole from someone else) and posted on my old website from the 90s: https://www.pontiacperforma...es/4_Speed_Swap.html


Here's the part about the axles though, which is less than ideal:

"The stock Fiero axles cannot be used with the four speed automatic. For a 4T60 you can use right and left axle assemblies for a '89 Pontiac 6000 with 4T60 and light duty brakes. The correct part numbers are A1 Cardone P/Ns are 60-1115 and 60-1078 or CCT 8471 left and 8430 right."

Also... the stuff in the link above about notching the subframe, that's ONLY if you have an 88... you won't have to worry about any of that.

But yeah, looks like you'll need new axles.


 
quote
Originally posted by Murcie-Me:
So when the mega is installed, do I no longer need the original ECU from the Fiero?
From what i've read in other articles, it doesn't seem to be a big deal to wire the mega squirt to the engine, but do I have to make my own harness?


No, if you install a MegaSquirt or something else... you basically replace the Fiero's factory ECU. You would have to make your own harness, but honestly... I'll tell you, it's really not that hard. Just make the harness with the engine sitting on the cradle OUT of the car, or on the engine stand. You don't want to have to build it with the engine already in the car. But it's not hard at all. I remade one for my daughter's 85 Fiero 2m4 SE, and it went perfectly except I managed to screw up the wires leading to the temperature gauge, haha... everything else is great.

There are plenty of options outside of the Mega/Micro Squirt too... just depends on what you want to use. Some of them are self-learning, like the Fast EZ-EFI 2.0, etc. But go with what you think has the best support for the motor (as in... what other people have already used, that you're also looking to do).
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Report this Post01-27-2025 01:33 PM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:


So when the mega is installed, do I no longer need the original ECU from the Fiero?
From what i've read in other articles, it doesn't seem to be a big deal to wire the mega squirt to the engine, but do I have to make my own harness?


Yeah, try to get the harness (or at least all of the electrical connectors on each sensor etc.) with the new engine, get the 8ft flying lead harness with the mega squirt, then splice all 3 together, using the connector ends/pigtails from the new engine, the body wiring (VSS, reverse switch, things like that) from the Fiero harness, and the majority of the wiring will be from the mega squirt harness, which is just a bunch of 8ft cables, route everything as nice as you can/want, and that should be it.
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Report this Post01-27-2025 02:54 PM Click Here to See the Profile for Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Nice job on the kit car. It sounds as though you're on your way to a very very nice engine swap. Good choice as the LZ9 is the most powerful of the high value GM engine family. An aftermarket cam cam will eliminate the VVT and can significantly boost horsepower. IIRC the engine weight will be close to the 2.8L V6. While the 4T60 4T60E and 4T65E HD will bolt up to the LZ9, The strongest easiest to fit transmission would be the 4T65eHD. If you use that box you will need an independent transmission controller.
A number of LZ9 3900 swaps have been done and there is a ton of info out there.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 01-28-2025).]

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Report this Post01-27-2025 04:51 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thank you Dennis, it was definitely a labor of love build, something I can hang onto and pass down to my kids.
I do Special Effects and props for the studios here in southern California, and everything I build eventually gets thrown in the trash after its shot, or disassembled for the parts. It was nice to build something knowing it won't be discarded in a few months lol.
Correct me if I'm wrong, but the 4T60 (non "E") is basically a 4 speed TH125 (stronger though) and the only electrical would be the TCC control. Shift timing is provided by the TV cable (like the TH125). Is it possible to control the TCC with the megasquirt, or would i need a separate control unit to plug into the megasquirt? What else would be required in order to electronically control the shift points on the "E" transmissions?
I'm not opposed to using the 4T60E or the 4T65E, I just don't know what all would be necessary to control the electronic requirements of those transmissions.
My donor car will most likely be a 2006 Chevrolet Impala, they have the LZ9 and a 4T65EHD transmission.
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Report this Post01-27-2025 07:34 PM Click Here to See the Profile for pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
Many folks suggest the MegaSquirt type stuff, but you are in California.

If you want this project to be street-legal, then you should probably stay away from MegaSquirt...
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Report this Post01-27-2025 08:45 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by pmbrunelle:

Many folks suggest the MegaSquirt type stuff, but you are in California.

If you want this project to be street-legal, then you should probably stay away from MegaSquirt...


All my cars and boat are registered under my L.L.C. in Montana, I paid a one time registration fee for each and have never had to pay again.
This is the car now, my son and I decided to try our hands at doing a satin purple wrap. It actually came out really nice.
I was also wondering about the fuel pump pressure. Does the stock Fiero fuel pump put out enough pressure for the LZ9 injectors?.


[This message has been edited by Murcie-Me (edited 01-27-2025).]

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Report this Post01-28-2025 08:30 AM Click Here to See the Profile for 82-T/A [At Work]Send a Private Message to 82-T/A [At Work]Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:
I was also wondering about the fuel pump pressure. Does the stock Fiero fuel pump put out enough pressure for the LZ9 injectors?.




I am still so amazed at the fit and finish of that car. Obviously a lot of work had to be done, because the windshield is different too. Most people change out the panels, but leave the windshield and A-pillars, which makes it a dead give-away... but you updated all of that too. It looks amazing.


Short answer is yes (I'm 95% sure). The fuel pump in the V6s goes up to 45psi or higher, which is basically what's required for all of those motors ~42psi.

But with all the work you've done to the car, I'd highly recommend replacing the fuel pump with a newer one (high quality), simply because you'll already have the engine out, and then you can also swap out the rubber fuel lines and rubber filler neck too.
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Report this Post01-28-2025 10:34 AM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 82-T/A [At Work]:


I am still so amazed at the fit and finish of that car. Obviously a lot of work had to be done, because the windshield is different too. Most people change out the panels, but leave the windshield and A-pillars, which makes it a dead give-away... but you updated all of that too. It looks amazing.


Short answer is yes (I'm 95% sure). The fuel pump in the V6s goes up to 45psi or higher, which is basically what's required for all of those motors ~42psi.

But with all the work you've done to the car, I'd highly recommend replacing the fuel pump with a newer one (high quality), simply because you'll already have the engine out, and then you can also swap out the rubber fuel lines and rubber filler neck too.


Yeah I've heard differing opinions, the pump can definitely go up to the pressures, but I don't know if it has the flow rate. It seems it's the same pump as is used on some V8 Corvette (plastic instead of metal intervals though) so it should be able to. I have a Rodney Dickman fuel pump (60psi max) and I don't know if it will be enough for the turbo 3400, but I will monitor the fuel pressure, and see if it is, it should be though. It's a cheap, high quality pump made by someone you can trust, so if it can handle it, I'm definitely keeping it.
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Report this Post01-28-2025 12:17 PM Click Here to See the Profile for Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:


All my cars and boat are registered under my L.L.C. in Montana, I paid a one time registration fee for each and have never had to pay again.
This is the car now, my son and I decided to try our hands at doing a satin purple wrap. It actually came out really nice.
I was also wondering about the fuel pump pressure. Does the stock Fiero fuel pump put out enough pressure for the LZ9 injectors?


I would not use an aftermarket ECM. The in tank fuel pump used by the LZ9 feeds a returnless fuel system that requires a pulse width modulated voltage signal.l. You may be able to use a stock style fuel pump if you add a regulator to the single feed line. Then if you go to an electric shifted trans the megasquirt won't be able to shift it..

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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Report this Post01-29-2025 12:17 AM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
I think im sold on the non electrically controlled 4T60, I want to make this as simple as possible. For the fuel pump, I'll either modify one from the 2006 Impala or buy something aftermarket. The fiero fuel pump puts out between 34-46 P.S.I., while the required pressure for the LZ9 injectors is 55-62.
I went to the local junkyard today and pulled all the wiring plugs off an Impala they had there. I think the only ones I'll need is for the oil pressure sender, coil pack, TPS, IAC (I will probably use a different throttle body though), and the temperature sensor.

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Report this Post02-01-2025 11:13 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
I went to the junkyard today and picked up an LZ4 intake manifold, and a 75mm throttle body from a 1998 chevy pickup. I took the throttle body apart and soaked in in parts cleaner for an hour and then washed the manifold with simple green and a pressure washer.
Does anybody know if the throttle position sensor and the idle air control on this throttle body is compatible with the megasquirt mini pro3 ECM?
I'm still looking for a 4T60 transaxel on Ebay, they seem to be few and far between.
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Report this Post02-02-2025 10:05 AM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:

I went to the junkyard today and picked up an LZ4 intake manifold, and a 75mm throttle body from a 1998 chevy pickup. I took the throttle body apart and soaked in in parts cleaner for an hour and then washed the manifold with simple green and a pressure washer.
Does anybody know if the throttle position sensor and the idle air control on this throttle body is compatible with the megasquirt mini pro3 ECM?
I'm still looking for a 4T60 transaxel on Ebay, they seem to be few and far between.


TPS should be, as far as I know basically everything "normal" is supported, the IAC won't be, that's a 4 wire IAC, it has 2 coils that are pulsed back and forth against each other to achieve a position, the megasquirt 3 pro mini only supports 2 wire PWM iacs, using an electromagnet pulsed against a spring to hooks position, I don't know of any throttle bodies with that type, haven't really looked into it, I'll be using a hose input output IAC, I can hook it up into the original IAC tube going from the throttle body to the lower intake, some BMW's have them, some Volkswagen's, mine came from a Porsche 911 from some year, maybe some Mustangs as well.

[This message has been edited by 1985 Fiero GT (edited 02-02-2025).]

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Report this Post02-02-2025 11:52 AM Click Here to See the Profile for BillSSend a Private Message to BillSEdit/Delete MessageReply w/QuoteDirect Link to This Post
Not sure how much power you are after, but you can get reasonable power using the V6. I have a 3.4 V6 in one of my cars that puts out in the 190-200 bhp range using conventional tuning methods.

My old 88 Fiero had around 300 bhp using a 3.2 displacement with 10 psi of turbo. Ran really well without issue for the 19 years I owned it.

Either of those avoids changing the engine to a V8 and avoids a fair bit of work.
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Report this Post02-02-2025 03:59 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 1985 Fiero GT:


TPS should be, as far as I know basically everything "normal" is supported, the IAC won't be, that's a 4 wire IAC, it has 2 coils that are pulsed back and forth against each other to achieve a position, the megasquirt 3 pro mini only supports 2 wire PWM iacs, using an electromagnet pulsed against a spring to hooks position, I don't know of any throttle bodies with that type, haven't really looked into it, I'll be using a hose input output IAC, I can hook it up into the original IAC tube going from the throttle body to the lower intake, some BMW's have them, some Volkswagen's, mine came from a Porsche 911 from some year, maybe some Mustangs as well.



I was wondering if it was possible to do something like you mentioned, maybe milling a port in the intake where the IAC can be mounted and not on the throttle body. I'm sure a plate can be made to seal the opening where the IAC mounts to the throttle body. Is there any reason the IAC needs to be on the throttle body???
Do you know it the IAC on the Fiero 2.8 is a 2 wire, and if so would that be compatible with the megasquirt?

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Report this Post02-02-2025 04:12 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post

Murcie-Me

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quote
Originally posted by BillS:

Not sure how much power you are after, but you can get reasonable power using the V6. I have a 3.4 V6 in one of my cars that puts out in the 190-200 bhp range using conventional tuning methods.

My old 88 Fiero had around 300 bhp using a 3.2 displacement with 10 psi of turbo. Ran really well without issue for the 19 years I owned it.

Either of those avoids changing the engine to a V8 and avoids a fair bit of work.


Hey Bill! Its not a horsepower thing with me, the stock 2.8 thats in the car right now is way underpowered though, it would be nice to have the additional 100H.P. that the LZ9 puts out.
I definitely want to stay with a V6, not only for space allowance but also since it will bolt right up to the TH125C if I want. I want to upgrade to a 440-T4 (4T60) , the LZ9 will bolt directly to that but they seem to be very difficult to find.
I'm trying to get everything sorted out prior to removing the engine that I have, I'm allowing a 2 week timeframe to take the old running engine out and put in the new engine and have it running and ready to drive.
While I have the LZ9 on the stand, I will be making a custom stainless steel exhaust for it with a specially designed long tube resonator to remove the low notes from the exhaust and give it a more exotic sound. Since the car is registered in Montana I dont have to be California compliant for smog, so i'm going to go extreme on the exhaust system.
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Report this Post02-02-2025 10:17 PM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:


I was wondering if it was possible to do something like you mentioned, maybe milling a port in the intake where the IAC can be mounted and not on the throttle body. I'm sure a plate can be made to seal the opening where the IAC mounts to the throttle body. Is there any reason the IAC needs to be on the throttle body???
Do you know it the IAC on the Fiero 2.8 is a 2 wire, and if so would that be compatible with the megasquirt?


Fiero IAC is a 4 wire unfortunately, and no it doesn't have to be on the throttle body, the stock Fiero one takes air from before the throttle body and sends it through a tube directly to the lower intake manifold, if you removed any stock IAC, make sure to plug up the air passages as well as blocking the hole it was in, otherwise you'd have a vacuum leak.
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Report this Post02-02-2025 10:27 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 1985 Fiero GT:


Fiero IAC is a 4 wire unfortunately, and no it doesn't have to be on the throttle body, the stock Fiero one takes air from before the throttle body and sends it through a tube directly to the lower intake manifold, if you removed any stock IAC, make sure to plug up the air passages as well as blocking the hole it was in, otherwise you'd have a vacuum leak.


I appreciate the info! Yes I would block off the IAC port on the throttle body, but am not 100% sure how I would have to hook up an independent valve. You mentioned that you are using something from a Porsche? Do you have a picture you can post here to give me an idea of what needs to be done?

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Report this Post02-03-2025 10:46 AM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:


I appreciate the info! Yes I would block off the IAC port on the throttle body, but am not 100% sure how I would have to hook up an independent valve. You mentioned that you are using something from a Porsche? Do you have a picture you can post here to give me an idea of what needs to be done?


Yes, it looks like this, mine is from a 1989-90 Porsche 911, got it for 27 bucks on eBay:

And I will simply put it in the large tube that already goes from the throttle body to the lower intake manifold on the field stock IAC, without having that on a different engine, maybe you could add a large vacuum port or something else, I'm not sure what would be easiest.
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Report this Post02-03-2025 01:20 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thats exactly what i am looking for! That unit is a 3 wire IAC though, is one wire not used?
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Report this Post02-03-2025 04:05 PM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:

Thats exactly what i am looking for! That unit is a 3 wire IAC though, is one wire not used?


Nope, 2 wire, there are several 3 wire ones, the 2 wire ones are harder to find, 3 wire can work, it's more complicated and I'm not sure how exactly, but there should be something in the mega squirt instructions about it.


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Report this Post02-03-2025 04:22 PM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post

1985 Fiero GT

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Somewhere on your intake you'd probably have an EGR input, that would likely be big enough to use for the IAC, and megasquirt doesn't control EGR anyhow.
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Report this Post02-03-2025 08:06 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
After doing a better search, I found this 2 wire IAC on Amazon, Not bad at $43 !
So, is the EGR valve even necessary? I don't intend to have the vehicle smogged after this install, so do I even need to worry if it doesn't have an EGR valve on it?
I was able to track down a 4T60 transmission today, so that's one less thing to worry about. Do you know if there are inputs on the megasquirt for a crank position sensor and a camshaft position sensor, or are those unnecessary as well?
I want to set it up to do the sequential injection, but does the ECU also control the spark in the same fashion?

[This message has been edited by Murcie-Me (edited 02-03-2025).]

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Report this Post02-03-2025 08:56 PM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:

After doing a better search, I found this 2 wire IAC on Amazon, Not bad at $43 !
So, is the EGR valve even necessary? I don't intend to have the vehicle smogged after this install, so do I even need to worry if it doesn't have an EGR valve on it?
I was able to track down a 4T60 transmission today, so that's one less thing to worry about. Do you know if there are inputs on the megasquirt for a crank position sensor and a camshaft position sensor, or are those unnecessary as well?
I want to set it up to do the sequential injection, but does the ECU also control the spark in the same fashion?



Yeah, that should work, EGR is a gas saver/emissions thing, it isn't necessary, and if you don't need inspections/smog/whatever, then yes, you can remove it, the megasquirt has no tables or options to control it, do it would be sitting there didn't nothing anyway, might as well use the port for IAC, the megasquirt 3 pro mini has cam/crank inputs, 3 digital inputs, 4 analog inputs, coolant and intake temp inputs, TPS input, 4 spark outputs (can use unused spark outputs as 5v logic level outputs), 8 injector outputs (can use unused injector outputs as general outputs, turbo boost solenoid, etc.), fuel pump relay output, and an IAC PWM output.

You can find the manual for the 3 pro mini ECM Here.

The ECM needs the crank and cam sensors to do sequential fuel injection, the spark distribution should be handled by the dis board (with the 3 coil packs on it) that gm uses, but the ECM controls the timing that sparks fire at.
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Report this Post02-03-2025 10:13 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Wow this is complicated, but I love it lol!
Thank you for your knowledge and advice, I really appreciate it!
Are you on any other forums?
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Report this Post02-03-2025 11:53 PM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:

Wow this is complicated, but I love it lol!
Thank you for your knowledge and advice, I really appreciate it!
Are you on any other forums?


Nope, just Pennock's, this megasquirt stuff is new for me to, but I've done a lot of research, so read the manuals, etc. get the theoretical down and everything planned out in advance.
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Report this Post02-04-2025 12:23 AM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 1985 Fiero GT:


Nope, just Pennock's, this megasquirt stuff is new for me to, but I've done a lot of research, so read the manuals, etc. get the theoretical down and everything planned out in advance.



Yeah that's exactly what I'm trying to do. I want to have everything figured out beforehand so the install goes as quick and smoothly as possible, and not waste time by having to stop progress because i've come to a fork in the road.
I used to have a build diary on the old "Mad Mechanics" site when I was building my replica. I had 75% of it figured out before I started by looking at other peoples build diaries and figuring it how I would do something better or more efficiently. I got my car done in 14 months, it took the other builders 5-8 years to do theirs. I want this engine changeover to be started and completed in 2 weeks, I dont want this to drag into months.
I will probably buy the Megasquirt next week, and like you say read the manual and get familiar with everything beforehand. Once again, thank you for all your help.

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Report this Post02-04-2025 10:43 AM Click Here to See the Profile for TheMoist1Send a Private Message to TheMoist1Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Murcie-Me:


I appreciate the info! Yes I would block off the IAC port on the throttle body, but am not 100% sure how I would have to hook up an independent valve. You mentioned that you are using something from a Porsche? Do you have a picture you can post here to give me an idea of what needs to be done?


In the MS3Pro mini user manual, in section 5.4. it says you can choose between 2-3 wire pwm or 4-6 wire stepper IAC. you may not be able to do a 4 wire pwm but that is fine since the one built into the throttle body is a stepper.
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Report this Post02-04-2025 05:28 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by TheMoist1:


In the MS3Pro mini user manual, in section 5.4. it says you can choose between 2-3 wire pwm or 4-6 wire stepper IAC. you may not be able to do a 4 wire pwm but that is fine since the one built into the throttle body is a stepper.



Wow that's good to know, thank you for that information!
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Report this Post02-05-2025 01:33 AM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by TheMoist1:


In the MS3Pro mini user manual, in section 5.4. it says you can choose between 2-3 wire pwm or 4-6 wire stepper IAC. you may not be able to do a 4 wire pwm but that is fine since the one built into the throttle body is a stepper.


That's specifically taking about the software setup, which uses the same options between many different products, whether they are available or not, the actual 3 pro mini does not support stepper IAC valves as it says in section 4.7.1, there literally are no additional wires to use.
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Report this Post02-05-2025 09:01 AM Click Here to See the Profile for I LeanSend a Private Message to I LeanEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 1985 Fiero GT:


That's specifically taking about the software setup, which uses the same options between many different products, whether they are available or not, the actual 3 pro mini does not support stepper IAC valves as it says in section 4.7.1, there literally are no additional wires to use.


So this will be the way:

https://www.efisource.com/w...iac-stepper-adapter/



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Report this Post02-05-2025 09:37 AM Click Here to See the Profile for 1985 Fiero GTSend a Private Message to 1985 Fiero GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by I Lean:


So this will be the way:

https://www.efisource.com/w...iac-stepper-adapter/




Even with that, it requires 3 wires coming from the microsquirt, 2 of which don't exist in the same way in the megasquirt, maybe you could reassign some other outputs, I don't know.

The microsquirt manual talks about those add ons specifically, using the 2 spare analog inputs as stepper outputs, the megasquirt 3 pro mini doesn't mention stepper add on boards (it specifically says it is not compatible with stepper motors), and nowhere do I see that the analog inputs can be used as outputs in any way.

In the megasquirt 3 pro mini software there are no options for the stepper motor using other pins, just as pictured, with the microsquirt they have the option of stepper motor, using the extra pins.

[This message has been edited by 1985 Fiero GT (edited 02-05-2025).]

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Report this Post02-05-2025 04:49 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post

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Report this Post02-06-2025 11:40 PM Click Here to See the Profile for Murcie-MeSend a Private Message to Murcie-MeEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'll order the Megasquirt next week, whether I can use the IAC that's already in the throttle body or use the Porsche one from Amazon, i'll have both covered!
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