3.6 liter High Feature I a Fiero (Page 6/15)
Chris Eddy SEP 17, 11:11 AM

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In my build, I'm doing exactly the opposite of what most of these people do with VVT. I'm retrofitting it into an engine which didn't come with it.


Well don't leave us in suspense.. how are you controlling the VVT in your franken-cam?
Joseph Upson SEP 17, 12:09 PM

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Originally posted by dobey:


If I did state this, I'm pretty sure I would have qualified that as "they are doing it because they believe it will make more power" rather than because it's an absolute fact that it does. Non-VVT camshafts can only be used to make power in a certain range. As most people installing camshafts in LSx motors tend to install big cams with wider LSAs, they might see a decently large enough peak number in the high end, but are sacrificing the low end to get it. Because of the wide LSAs and large durations these cams have, VVT would be somewhat problematic for many of these very large cams. However, these tend to also introduce other expenses such as needing clutches or torque converters which also sacrifice driveability. If they would cut back on the LSA and duration a bit, an LSx could easily make near the same peak numbers, but have a much wider powerband, and remain driveable on the street, as well as getting better MPG with lower emissions.

In my build, I'm doing exactly the opposite of what most of these people do with VVT. I'm retrofitting it into an engine which didn't come with it. I found a decent cam, but it was only in non-VVT form, so I took the numbers and had a custom grind made on a VVT core. My goal is to get at least 400 HP/400 lbs-ft at the crank, and 40 MPG highway, as well as being able to meet CA's SULEV standard.




Thanks for the clarification. I was only focusing on the Fiero Forum and 60 degree exploits. The VVT delete conversation I'm referencing was also toggling dyno test results and the conversation was more along the lines of anti VVT as it was suggesting that VVT was more a means to eliminate EGR valves which is probably the case in cam in block engines. DOHC motors on the other hand stand to gain a lot more versatility with the ability to independently change intake and exhaust timing and I'd certainly prefer it to get the most in performance and fuel efficiency.
dobey SEP 17, 12:30 PM

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Originally posted by Chris Eddy:

Well don't leave us in suspense.. how are you controlling the VVT in your franken-cam?



GM e38 ECM
dobey SEP 17, 12:48 PM

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Originally posted by Joseph Upson:
Thanks for the clarification. I was only focusing on the Fiero Forum and 60 degree exploits. The VVT delete conversation I'm referencing was also toggling dyno test results and the conversation was more along the lines of anti VVT as it was suggesting that VVT was more a means to eliminate EGR valves which is probably the case in cam in block engines. DOHC motors on the other hand stand to gain a lot more versatility with the ability to independently change intake and exhaust timing and I'd certainly prefer it to get the most in performance and fuel efficiency.



Really, VVT is not a means to eliminate EGR in cam-in-block engines. It's much more useful for that in DOHC engines (or in Hemis with the cam-in-cam design), where intake and exhaust are independently controlled. The GM cam-in-block engines have a static overlap value, so EGR is much harder to control from a VVT perspective in that sense. In the Hemi cam-in-cam or in DOHC engines, the overlap can be changed, to a much larger degree in the DOHC engines, which allows for meaningful EGR control at cruising speeds. With the introduction of the Gen IV LS engines in 2005, EGR was completely eliminated, but the Gen IV didn't get VVT until 2008. There were still some other engine families with EGR valves and/or A.I.R. of course, including the 3.5/3.9, I'm only talking about the LS for sake of simplicity. However, with VVT, at cruise speeds, the cam can be placed into the fully retarded position under light load cruise conditions, which reduces power output to increase efficiency, which greatly reduces the need for an EGR valve to meet emissions requirements, and thus lowers production costs.

For an all out race car that won't be driven on the street, and will spend almost all of its time at 5000+ RPM, deleting VVT and going totally wild on the cam will probably be a better option. But for a street driven car, even that may see part time track duty, I think a milder cam with VVT will almost always be a better option, giving more total output even if peak numbers are slightly lower. I would do whatever I can to use VVT in any engine swap I was doing, if possible. I totally understand your reasoning for wanting to lock the cam in your swap, but maybe now that tuning options are easier to come by (I presume you tune your car with HP Tuners, which can handle VVT in the GM ECMs), you might want to look into possibly unlocking the cam and tuning the VVT to give you a smoother power band and better fuel economy.
Joseph Upson SEP 17, 05:50 PM

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Originally posted by dobey:
(I presume you tune your car with HP Tuners, which can handle VVT in the GM ECMs), you might want to look into possibly unlocking the cam and tuning the VVT to give you a smoother power band and better fuel economy.



It's all give and take, GM is holding back on the compression ratio. It's high by old standards but not by new combustion chamber design and fuel delivery tech. I believe they're inching along to avoid giving too much too soon and having greater difficulty in the future meeting increasing EPA demands. My fuel economy is great at 27-28 mpg hwy and exceeded 30+ on the first build with higher compression. If I'm not mistaken the latest 3.6L in some applications is still rated for 87 octane with as high as 11.X compression so I know they can go much higher than that on pump gas even if it requires premium fuel. The performance increase would be far greater than a mere 10% naturally aspirated if they took greater advantage of the compression ratio which I would do and is why I'm so interested in this engine.

I understand the crank pins are 2.2" so I'd be looking to stroke the motor in addition to the compression bump the same as I did with the 3.9L.

[This message has been edited by Joseph Upson (edited 09-17-2016).]

dobey SEP 17, 09:08 PM

quote
Originally posted by Joseph Upson:
It's all give and take, GM is holding back on the compression ratio. It's high by old standards but not by new combustion chamber design and fuel delivery tech. I believe they're inching along to avoid giving too much too soon and having greater difficulty in the future meeting increasing EPA demands. My fuel economy is great at 27-28 mpg hwy and exceeded 30+ on the first build with higher compression. If I'm not mistaken the latest 3.6L in some applications is still rated for 87 octane with as high as 11.X compression so I know they can go much higher than that on pump gas even if it requires premium fuel. The performance increase would be far greater than a mere 10% naturally aspirated if they took greater advantage of the compression ratio which I would do and is why I'm so interested in this engine.

I understand the crank pins are 2.2" so I'd be looking to stroke the motor in addition to the compression bump the same as I did with the 3.9L.



Yeah, the CR is getting up there. It's 11.5:1 on the Gen V LT1 and L86 too. The LT4 is dropped down to 10.0:1 for the boost though. I'm building my LS4 to be around 11:1. I think they're "slowly" working it up to the point where they switch over to HCCI instead of spark ignition. They've been working on it for a while now, but I guess they haven't quite got it to where it needs to be for reliability and driveability in production cars yet. I'm expecting the Zora mid-engine Vette to be a hybrid car too. No idea what the engine will be exactly, other than I expect it to be based on the Gen V V8. I think there are a couple of Ecotec (or similar) engines used in some Opels that had up to 12.0:1 compression.

Heck, Honda had some cars with 11.1:1 in the 90s/00s. The B16A3 in my del Sol is 10.4:1. It requires premium, because it is PFI and engine management back then wasn't anywhere near what it is today, but it gets 28 MPG around town and mid-high 30s on the highway.
Crytes SEP 18, 09:16 AM
So how high does compression get before an engine stops being spark ignition? Or is the practical limit on compression from some element now? What I want is a street friendly 500 hp fiero with a power tain about the same weight as stock and decent milage for commute driving. I'm thinking this will require leveraging and pushing all the technology available to it's practical limit. Or just a pipe dream.
fieroguru SEP 18, 10:19 AM

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Originally posted by Crytes:
What I want is a street friendly 500 hp fiero with a power tain about the same weight as stock and decent milage for commute driving. I'm thinking this will require leveraging and pushing all the technology available to it's practical limit. Or just a pipe dream.



Not sure if you are talking rwhp or fwhp, by my LS4/F40 88 Fiero has 382 whp (about 430 fwhp), weighs a little over 2800 lbs, and averaged 23 mpg on the 2800 mile HRPT (lots of stop/go, AC on, some 110mph sprints on toll roads). Some tanks I see at high at 29 mpg depending on type of driving. I have put 34K miles on it in 3 years as I daily drive it most days except for winter or when there is salt on the road. I could add a small shot of nos and easily get to your targets without compromising the other criteria.

I am in the planning stages for adding a turbo...
bmwguru SEP 18, 01:59 PM
One issue with the stock ecu was the vehicle speed sensor. There is not a sensor in the transmission on the Saab F40. It uses the ABS module to send the VSS signal on the can bus line. I wasn't about to add that in. The AEM wants to know the VSS also, but I spoke with Speedhut (the manufacturer of my gauges) and they do offer a VSS output from their GPS speedometer on some models.
I'll have to update my build thread one of these days....There is quite a bit to update.
Dave

[This message has been edited by bmwguru (edited 09-18-2016).]

Crytes SEP 18, 03:49 PM
FieroGuru I din't realize transmission losses were so great. 383 Wheel to 430 Flywheel is a 11% lose. Either way I'd be happy with flywheel numbers close enough to call 500hp I like the idea of say my car has 5 time the power of stock. I figured a turbo would be needed to get into the power I want and a dual spool looks good for drivability. Currently I'm looking at the F40 but don't like the idea of adapting it to a different engine too many wear parts for my taste. The LS4 does look nice tho might have to look at your page again and see if I can live with the compromises to make it fit. Until I start buying parts my current idea is to see is the new Ecotec 2.5 will accept the top end off the new 2.0 turbo my guess is that combo should be close if it can be tuned in.