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Question about LIM Porting by zkhennings
Started on: 03-01-2014 02:27 PM
Replies: 13 (398 views)
Last post by: zkhennings on 03-04-2014 09:21 PM
zkhennings
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Report this Post03-01-2014 02:27 PM Click Here to See the Profile for zkhenningsSend a Private Message to zkhenningsEdit/Delete MessageReply w/QuoteDirect Link to This Post
When I ported my lower intake manifold, I really hogged it out around the injector area where it necks like crazy right where the injector sprays. I opened it up to the same size as the port size in the gasket, which is huge.



Here is what mine looks like.

I just had my car dyno'd on a Mustang Dyno, and with all my modifications I hit around 135hp at the wheels which I am happy about, especially because Mustang Dynos are known to dyno low. I got around 150 ftlbs of torque though, which is less than I was expecting, and my gas mileage has been terrible, yet my AFR was 12.2 the whole run, and much higher than that under other conditions. So I am wondering if by opening the ports up that much I have altered the flow to the heads negatively, and caused the fuel air mixture to mix poorly because the air velocity is now lower at that point than stock. I have another LIM I could port and just keep the general cross section but blend it a little.

Let me know what you think, it is really hard to predict what goes on in the runners.

Mods are as follows:

Compcams 260H camshaft
Ported Intakes and Exhaust manifolds
Ported heads: Intake and Exhaust and ported bowls
Custom high flow Y pipe and 2.5 inch exhaust through Borla XR-1 Muffler, no Cat

Thanks
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Report this Post03-01-2014 02:59 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you didn't do anything to the upper intake I would expect porting the lower to gain you nothing at all. Larry
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Report this Post03-01-2014 04:01 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
The modification you made to the LIM is probably hurting fuel atomization. You could swap in a stock LIM and see how that effects things. Then you'd know for sure.

That said, if you do decide to port another LIM, you may get better results from profiling the port floor around the injector hump. There's a pretty sharp drop there.
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zkhennings
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Report this Post03-01-2014 04:32 PM Click Here to See the Profile for zkhenningsSend a Private Message to zkhenningsEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

If you didn't do anything to the upper intake I would expect porting the lower to gain you nothing at all. Larry


The whole intake is ported, and I am getting rid of the neck restriction and boring out my throttle body as well. I know the lower flows the worst of the 3, just from Bruce's flow test data.

 
quote
Originally posted by Blacktree:

The modification you made to the LIM is probably hurting fuel atomization. You could swap in a stock LIM and see how that effects things. Then you'd know for sure.

That said, if you do decide to port another LIM, you may get better results from profiling the port floor around the injector hump. There's a pretty sharp drop there.


I did do this, they are really smooth now with no drops. I think it is hurting fuel atomization too, also if you look at the shape of the port, it directs the flow into the heads down towards the vane. I bet this is critical to the vane functioning properly to increase flow, and probably helps the atomization and causes extra turbulence.

Just for kicks I am going to cut shallow curved grooves into my unported LIM to cause a rifling effect to aid in atomization. I can't see it hurting, more just maybe doing nothing.


Also here is my Dyno from today



The black line is AFR, and where it dips, that value is 11.9 and the line it is the most on is 13, with the next line up being 13.4

132HP at 5500rpms

142T at 4250rpms

I am going to change some things in the upcoming weeks and will probably go back at some point to the same place.

[This message has been edited by zkhennings (edited 03-01-2014).]

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Brucepts
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Report this Post03-02-2014 10:19 AM Click Here to See the Profile for BruceptsClick Here to visit Brucepts's HomePageClick Here to Email BruceptsSend a Private Message to BruceptsEdit/Delete MessageReply w/QuoteDirect Link to This Post
My post is not meant to be a head porting pi$&ing contest from me, I know there are others who have a differing opinion and I am not a porting Guru but I also have not just stayed at a "Holiday Inn Express" either;

I know nobody here really wants to hear this but without the proper tools to know what you are doing when grinding away you are . . . well just grinding away! You really need to get in there with a velocity probe on a flowbench to see what is happening with the local velocity. I know most do not have access to those tools and it's simply read about on the net and applied to a given application but once you have the tools in hand you will think otherwise We can see this from prior flowbench testing I have done on the stock parts and myths that were disproved on areas that are thought to be bad for flow.

Each application will require it's own velocity profiles, there are "target" ranges to keep in mind ie velocity should never exceed test pressure, but you might only be a lot lower or higher feet per second (FPS) for different heads. I know this from feedback from different heads my customers work on which range from motor cycles to Pro Stock heads.

Opening up an area will drop velocity all one has to do is look at a creek or stream to see that happen in nature, (the wide areas flow slow and the narrow areas fast) same happens in a port not as large a range and we might only be looking at 50-100 FPS. Gasket matching is one of the worst things you can do in a long runner like a Fiero. You are not maintaining a consistent cross sectional area and that is the key to making velocity which in turn makes power. To much concern is had on CFM and not velocity of the CFM. On a running engine that flow is stopping and starting so the faster you can get that CFM flowing the more you get into the cylinder at a given piston speed. If you slow the flow to much before the valve you will not get the flow around the valve you need to setup a throat area prior to the valve to maximize the velocity around the valve head.

Calculated cross sectional areas for your given target power range and maximize the velocity for that area without losing CFM is the key. It comes down the the quality of flow and how the engine receives it.

I really wish I had time to sit down and do a detailed porting project on the stock Fiero parts! My business has expanded over the past year or two and I find myself not being able to put the parts up on the bench and start working on them as my flowbench gets used daily for customer flowbench parts testing prior to shipping. I'm working on a second flowbench that will allow me to keep my own parts setup for testing for a longer period of time so, I might be able to get some feedback at some point again.

Keep this in mind . . . you do not torque a bolt that requires a torque value without using a torque wrench so, why would you port a head without the proper tools to know what your outcome will be? A flowbench doesn't have to be some magical thing and a pretty simple one will show you results . . .

------------------
"There is no more formidable adversary than one who perceives he has nothing to lose." - Gen. George S. Patton
http://www.flowbenchtech.com

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Report this Post03-02-2014 12:16 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Zkhennings: I think I may have misread your original post. I originally read it using my cell phone, which for some reason wouldn't display the photo. I assumed, based on the wording, that you dug out the port wall opposite the injector hump to make the port taller in that area.

But now that I'm viewing the photo on a computer, it looks like you removed all that extra material just downstream of the injector. I did something similar with my old 2.8 V6 LIM, although not as aggressive. It didn't seem to hurt anything, and fuel economy was decent (mid 20s around town, low 30s on the highway). But then again, the LIM port work was part of a rebuild project that involved a bunch of other mods. So I don't know exactly how the LIM porting factored into the end result.

That said, I still think it would be a good idea to dyno or flow bench test your ported LIM versus a stock one, if you have the time and resources.
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zkhennings
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Report this Post03-02-2014 09:45 PM Click Here to See the Profile for zkhenningsSend a Private Message to zkhenningsEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Brucepts:

My post is not meant to be a head porting pi$&ing contest from me, I know there are others who have a differing opinion and I am not a porting Guru but I also have not just stayed at a "Holiday Inn Express" either;

I know nobody here really wants to hear this but without the proper tools to know what you are doing when grinding away you are . . . well just grinding away! You really need to get in there with a velocity probe on a flowbench to see what is happening with the local velocity. I know most do not have access to those tools and it's simply read about on the net and applied to a given application but once you have the tools in hand you will think otherwise We can see this from prior flowbench testing I have done on the stock parts and myths that were disproved on areas that are thought to be bad for flow.

Each application will require it's own velocity profiles, there are "target" ranges to keep in mind ie velocity should never exceed test pressure, but you might only be a lot lower or higher feet per second (FPS) for different heads. I know this from feedback from different heads my customers work on which range from motor cycles to Pro Stock heads.

Opening up an area will drop velocity all one has to do is look at a creek or stream to see that happen in nature, (the wide areas flow slow and the narrow areas fast) same happens in a port not as large a range and we might only be looking at 50-100 FPS. Gasket matching is one of the worst things you can do in a long runner like a Fiero. You are not maintaining a consistent cross sectional area and that is the key to making velocity which in turn makes power. To much concern is had on CFM and not velocity of the CFM. On a running engine that flow is stopping and starting so the faster you can get that CFM flowing the more you get into the cylinder at a given piston speed. If you slow the flow to much before the valve you will not get the flow around the valve you need to setup a throat area prior to the valve to maximize the velocity around the valve head.

Calculated cross sectional areas for your given target power range and maximize the velocity for that area without losing CFM is the key. It comes down the the quality of flow and how the engine receives it.

I really wish I had time to sit down and do a detailed porting project on the stock Fiero parts! My business has expanded over the past year or two and I find myself not being able to put the parts up on the bench and start working on them as my flowbench gets used daily for customer flowbench parts testing prior to shipping. I'm working on a second flowbench that will allow me to keep my own parts setup for testing for a longer period of time so, I might be able to get some feedback at some point again.

Keep this in mind . . . you do not torque a bolt that requires a torque value without using a torque wrench so, why would you port a head without the proper tools to know what your outcome will be? A flowbench doesn't have to be some magical thing and a pretty simple one will show you results . . .



I was in no way trashing you or anything Bruce!

I understood from the very beginning that I was taking a gamble opening it up like that. Everywhere else in the intake I did mild work, same in the head, I only feathered it in around an inch and took out casting irregularities. On the exhaust side I didn't even open it up, I just got rid of the spark plug humps and polished it. I smoothed the intake and exhaust bowls as well.

My reasoning for opening it up and changing the factory shape of the intake was as follows-

The intake was the one thing I got a little experimental on, I guessed my mileage would suffer if I got rid of it, but I figured I could possibly make more power. I took a gamble that the feature was solely to increase gas mileage and consequently hurt power. I assumed by causing a restriction (that hurt power), it increased air velocity around injection site causing better mixing of the fuel, and having a sharp drop into the head creates turbulence and helped mix it more before it entered the cylinders. There are plenty of features to improve emissions that hurt power so I figured it was not a super crazy theory. This was all speculation, and that is why I have 2 LIMs. For example, the falconer heads do not have the vanes, but they make a lot of low end power. I figured I might as well try it out and see what happens.

On the other hand I figured I might loose power for the reasons listed in my previous posts.

I am going to port my other LIM in the same manner as this one, but leave the injection site feature alone, but I will gasket match the 3 edges (where they would normally meet the head).

I will also see if I can get back on the same dyno and I will post results if I do!

I have taken some advanced fluid dynamics classes and understand that I can't just change cross sections and other features without pressure and velocity changes as well as all the other subtle changes that are so hard to predict when dealing with fluid flow.

Edit to say I also totally forgot I chose to go that route because I was planning on turbocharging it so I figured intake velocities would be high enough without it, and it would be better not to have the restriction!

[This message has been edited by zkhennings (edited 03-02-2014).]

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zkhennings
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Report this Post03-02-2014 09:56 PM Click Here to See the Profile for zkhenningsSend a Private Message to zkhenningsEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Blacktree:

Zkhennings: I think I may have misread your original post. I originally read it using my cell phone, which for some reason wouldn't display the photo. I assumed, based on the wording, that you dug out the port wall opposite the injector hump to make the port taller in that area.

But now that I'm viewing the photo on a computer, it looks like you removed all that extra material just downstream of the injector. I did something similar with my old 2.8 V6 LIM, although not as aggressive. It didn't seem to hurt anything, and fuel economy was decent (mid 20s around town, low 30s on the highway). But then again, the LIM port work was part of a rebuild project that involved a bunch of other mods. So I don't know exactly how the LIM porting factored into the end result.

That said, I still think it would be a good idea to dyno or flow bench test your ported LIM versus a stock one, if you have the time and resources.


I just went through your thread again and found a picture of your lower intake, and I can see only the shape of the port which is opened up as big as mine, but I cannot see how much you removed directly around the injection site. I might just have crappy injectors too, but about a year ago I cleaned them all out with pressurized injector cleaner and tapped leads from a battery to the terminals to get the injector to spray bursts of the fluid through. They all sprayed pretty well by the end, but that is extremely subjective. Maybe maybe maybe (because I am going 3800 asap but that might mean a year from now) I will upgrade to disk type injectors instead of the pintle ones I have.
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Report this Post03-03-2014 07:10 AM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
First...
Is this a 3.4? or a 2.8?
Those are great numbers for a 2.8. Typical of what I saw with a 3.4, that didn't have the upper intake modded.
I can't say that I found anything to fault with your intake porting.

This is what mine looked like. (porting by Darrell Morse)


Top side of LIM.


This is what my head ports looked like.
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Report this Post03-03-2014 09:22 AM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
Knowing what size engine you have would help a lot. 150 ft*lbs on a 2.8 on a Mustang dyno sounds reasonable...however, on two separate Mustang dynos with my 3.4 I've done 164 ft*lbs on one known to be extremely low (engine running bad) and 249 then 203 ft*lbs on one calibrated to within 5% of a dynojet when my motor was running good, then bad.

You should also shoot for a 13.0:1 a/f ratio.

[This message has been edited by lou_dias (edited 03-03-2014).]

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zkhennings
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Report this Post03-03-2014 01:54 PM Click Here to See the Profile for zkhenningsSend a Private Message to zkhenningsEdit/Delete MessageReply w/QuoteDirect Link to This Post
It is indeed a 2.8, I think I am still going to attempt to put that factory feature back in, because there must have been a good reason for having it to begin with, it only complicated the casting. My gas mileage is very Ok on the highway, I average around 26 mpg driving around 75. In the city however, I averaged around 12 mpg on my last tank. It was purely backroads driving, half short hops (but I always let my car warm up first because its usually like 20-35 degrees at the moment). I do drive at WOT often though, because I am at school and don't really need to leave for much, so usually when I am driving it is just for fun in deserted backroads.

But when I put it back in, I will also have a larger TB and the restriction removed from the intake/ plenum volume increased. Depending on how much the dyno will cost me (last one was free through the motorsports club) maybe I will get a student discount, I could dyno just the intake difference.


Here's A link to my build, I built the engine myself

http://www.fiero.nl/forum/Forum2/HTML/123796.html

[This message has been edited by zkhennings (edited 03-03-2014).]

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Report this Post03-03-2014 10:29 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
I also think your performance numbers look pretty good. But it looks like you're going really rich when you first hit the throttle. Some tuning should help with that, and will probably improve your fuel economy too.
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zkhennings
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Report this Post03-04-2014 12:25 AM Click Here to See the Profile for zkhenningsSend a Private Message to zkhenningsEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Blacktree:

I also think your performance numbers look pretty good. But it looks like you're going really rich when you first hit the throttle. Some tuning should help with that, and will probably improve your fuel economy too.


Yea it dips pretty low, into the 11s. I wish I had the means to tune it, I have everything I need to do it but the actual Eprom eraser and the flasher itself. But I have datalogging software and tuning software. I have looked briefly into the moates products, but I have realized if I really want to tune it that I need to upgrade to 7730. I will have to decide whether it is worth it financially with how long it will have the 2.8
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Report this Post03-04-2014 09:21 PM Click Here to See the Profile for zkhenningsSend a Private Message to zkhenningsEdit/Delete MessageReply w/QuoteDirect Link to This Post
So it is 60 bucks for 3 dyno pulls, or 100 for an hour... Which actually is not that bad.
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