GM Crossfire build

[Kane]

Hi- this is an INCREDIBLE site!!! Y'all have a lot of great information here and I am very happy I found these message boards!

I have a 1982 Corvette that has been in my family since the 80s. My dad was the second or maybe third owner and I have had it for almost two years. My intent is to keep the car as stock looking as possible- so that means keeping the OE airbox, twin TBIs, etc.


I recently put a crate motor into it and have been working on getting the tune where I want it. Seems to be running really well- although I still think I have some fine tuning with some of the tables.

Here is what I have:

Engine:

• Cast iron pre '86 passenger car perimeter bolt heads
• Hypereutectic pistons
• 9:1 compression
• .465"in / .488"ex - duration @.50 224in x 234ex
• 36 degrees total timing advance

Air / Fuel delivery & Engine Management:

• 80lb injectors
• Renegade Intake (full sized intake port aftermarket crossfire specific manifold)
• 15psi adjustable regulator
• Stock TBI units- balanced (removed the anti-tamper plug & weld)
• EBL Flash
• TT01 WB (coming soon, but not installed yet)

This has been a really education for me- that's for sure!

Some things have been trial and error. For example, I tried running a spark table originally for a TBI truck to get the tuning started since the heads are not aluminum, swirl port, Vortec, or other that seems to have a lot of SA maps floating around the web. Needless to say, a truck SA table wasn't a good match- so I found an older table from another project. My current SA table (in the attached file) is based upon an iron head, TPI motor with an L82 cam and 1.6 rockers I had about six years ago.

So here is my first question- does this SA table seem to be a good match? It seems to run very well from idle through 5k rpm with no knock at any rpm or kpa. The timing pulls into the ball park of maximum advance at WOT starting at 2200 (well, 33 degrees at WOT including PE at the upper kpas) and holds at almost 30 degrees (before PE) from 3200-4800.

And my second question... I'd like any thoughts or suggestions y'all might have about the tune otherwise.


Thanks in advance!

[Kane]

For anyone without the EBL XDF.... here is an image of the SA tables...

[Kane]

A few more...



VE tables so far and then some other tables and settings like idle speed, AE, BPC (not vacuum referenced), and a few others...


I still think the high speed VE tables may change with a few more VE learns, but they seem to be fairly set for idle to 2800rpm.

[Six_Shooter]

It's really hard to say that an SA table is good or not for an engine just by looking at the SA table, at least without obvious large changes from adjacent cells. ;)

Does the engine run well? Yes? It's probably a good match
Does the engine diesel? No? It's probably a good match
Does the engine pull smoothly? Yes? Then it's probably a good match.

Is there room for improvement? Likely...

Sometimes the only way to know if there is room for improvement is to try changing things and see what the result is.

[Kane]

It's really hard to say that an SA table is good or not for an engine just by looking at the SA table, at least without obvious large changes from adjacent cells. ;)

Does the engine run well? Yes? It's probably a good match
Does the engine diesel? No? It's probably a good match
Does the engine pull smoothly? Yes? Then it's probably a good match.

Is there room for improvement? Likely...

Sometimes the only way to know if there is room for improvement is to try changing things and see what the result is.

That's kinda what I was thinking- but being new at the tuning... figured I had better ask. :)


Again... kudos to the site... I looked over the the '85 and '86 Vette SA tables that y'all have out here. My heads are the same castings as those. 82/84/85 Corvettes all share the same casting numbers. So, I feel like based upon the way the car runs and then what I have seen in terms of SA tables for similar systems, I am in good shape to really start to tweak things. I literally spent MONTHS looking for SA tables for iron headed GM EFI cars. The most I found on my own were the 5.0L TBI trucks. Which would be great if I had a truck- but since I don't- I really got the sense the spark advance really needed to be higher. I couldn't place my finger on exactly how high it should be, but 8-13 degrees at 90kpa between 1000 and 2000rpm was just pitiful. I will say this for sure: 20- 26 degrees at 90kpa between 1000 and 2000rpm is a lot better.

And thanks again for having the online resources to confirm that for me!!

[Fast355]

That's kinda what I was thinking- but being new at the tuning... figured I had better ask. :)


Again... kudos to the site... I looked over the the '85 and '86 Vette SA tables that y'all have out here. My heads are the same castings as those. 82/84/85 Corvettes all share the same casting numbers. So, I feel like based upon the way the car runs and then what I have seen in terms of SA tables for similar systems, I am in good shape to really start to tweak things. I literally spent MONTHS looking for SA tables for iron headed GM EFI cars. The most I found on my own were the 5.0L TBI trucks. Which would be great if I had a truck- but since I don't- I really got the sense the spark advance really needed to be higher. I couldn't place my finger on exactly how high it should be, but 8-13 degrees at 90kpa between 1000 and 2000rpm was just pitiful. I will say this for sure: 20- 26 degrees at 90kpa between 1000 and 2000rpm is a lot better.

And thanks again for having the online resources to confirm that for me!!

My L82 based spark map doesn't have that quick of an advance rate, FWIW.

[Kane]

My L82 based spark map doesn't have that quick of an advance rate, FWIW.

Interesting.

So, would you be willing to share that SA table? I'd like to see what it looks like.

Thanks!

[Fast355]

Interesting.

So, would you be willing to share that SA table? I'd like to see what it looks like.

Thanks!

I would except its a Holden 5.0 based calibration. Basically a 165 TPI MAF ECM running Austrailian 808 based code.

[Kane]

Very interesting. I hadn't even thought about Holdens. Thanks for talking about your calibration.

I just looked over a BIN, AFTZ9887 with $5D, for an 89 Holden Commodore.
http://pcmhacking.net/forums/viewtopic.php?f=7&t=3

The Australian Holden's configuration, naming conventions, and whatnot are a really different way to look at things!


Anyway... if your SA tables are anywhere near that, I think I know what you meant when you said your spark map doesn't have that quick of an advance rate. Neat stuff!!!

[Fast355]

Very interesting. I hadn't even thought about Holdens. Thanks for talking about your calibration.

I just looked over a BIN, AFTZ9887 with $5D, for an 89 Holden Commodore.
http://pcmhacking.net/forums/viewtopic.php?f=7&t=3

The Australian Holden's configuration, naming conventions, and whatnot are a really different way to look at things!


Anyway... if your SA tables are anywhere near that, I think I know what you meant when you said your spark map doesn't have that quick of an advance rate. Neat stuff!!!

I am running $12P with a 2-bar map sensor because the low compression 350 I have in the car is destined for twin T3/T4 T04Es someday. Right now I am working on killing the TH250C that is in the car first and building a TH400 for it. The engine itself is pretty basic. Its one of those old goodwrench/targetmaster 350s that has been bored .030" over and built to 1980 L82 specs. It has flattop pistons, recondition "X" rods with arp bolts, factory forged crank turned .010/.010, and balanced, 76cc hecho en mexico heads with screw in studs, guide plates, Z/28 springs, 2.02/1.60 valves, Mellings C-410-P L82 grind cam (291/287 @ .006, 224/224 @ .050, .450/.460, 114* LSA, advanced 4* to 110* ICL, 1985 Camaro TPI setup with LT1 injectors, shorty headers and exhaust. The cam is not exactly ideal but given the non roller block and future plans the wider LSA will work out well and the lift works great with the junk heads and limited lift capacity. The TPI base has been ported, has a pair of AS&M large diameter runners, and a ported plenum on it. Power starts to come on around 2,500 and pulls pretty hard from 3,500 up to about 6,000 rpm.

[Kane]

Wow- that is totally wicked!

[Fast355]

Wow- that is totally wicked!

The static compression ratio is about 9:1 in and the dynamic compression ratio is in the mid to high 7s with only about 160 psi cranking compression. I only run 87 octane and the spark map is designed around use on 87 octane. I don't have a good method for ducting cool air to the throttle body and it has one of those rectangular filters right behind the radiator fan, not ideal but it works. One day I will convert to electric fans and make room for the proper duct work. You can see how much timing I have to remove at high coolant temps and intake air temps. Sitting idle with the a/c on in 100*F weather puts the engine running 210-220*F and the IATs in the 160*F range. Taking off out of a light the timing is pretty lame, but I get a ton of knock counts if I don't pull timing when its that hot.

The car itself is a 1980 L82 Corvette that came to me without an engine and trans. It had a 305 in it that I simply wore out. Was burning about 1 qt every 800 miles when I pulled it and leaking equally as much through the rear main. Pulled the engine when I rebuilt the suspension and cleaned up the frame.

[Fast355]

double

[Kane]

Almost a decade ago, I ran that same spark table I shared on an L82 based TPI motor. Same heads as you have- and yes same "hecho in Mexico" block as well. I did run an 85 Vette baseplate since it was a direct fit for the center intake bolts to the old style heads.

Like you, I had an '80 Vette that motor sat in. I ran speed density. Also ran with SLP runners and then out the sides with '69 style sidepipes.


On my '82, I went ahead and removed the solenoid and fresh air chamber flap. That helps draw in some air from just in front of the radiator through the hood and into the air box. You can't do that with a TPI motor though. I usually went with the L88 hoods to get some more clearance and reduce the underhood temps.

I'm not getting any knock with my SA tables as they stand. I also don't have an AC that works (it is all there- just the system is empty) and I run 93 octane. I have thought about the coolant temperature and potentially pulling the timing back at 200-220 degrees F. But again, no knock there that I have seen. Right now, I have left the TBI truck BIN's values for that alone.

[Fast355]

Almost a decade ago, I ran that same spark table I shared on an L82 based TPI motor. Same heads as you have- and yes same "hecho in Mexico" block as well. I did run an 85 Vette baseplate since it was a direct fit for the center intake bolts to the old style heads.

Like you, I had an '80 Vette that motor sat in. I ran speed density. Also ran with SLP runners and then out the sides with '69 style sidepipes.


On my '82, I went ahead and removed the solenoid and fresh air chamber flap. That helps draw in some air from just in front of the radiator through the hood and into the air box. You can't do that with a TPI motor though. I usually went with the L88 hoods to get some more clearance and reduce the underhood temps.

I'm not getting any knock with my SA tables as they stand. I also don't have an AC that works (it is all there- just the system is empty) and I run 93 octane. I have thought about the coolant temperature and potentially pulling the timing back at 200-220 degrees F. But again, no knock there that I have seen. Right now, I have left the TBI truck BIN's values for that alone.

85 camaro has the same older pre 87 style of intake as well.

Its hard to know what spark advance curve works best unless you do some back performance testing. I have on particular section of road that starts off slightly uphill and levels off that is perfect for 0-60 mph testing as it has no cross roads and is 2 lanes wide. My timing advance under 2,500 rpm is sand bagged a touch to allow the car to actually hook up rather than just light up tires.

I am running speed density as well, just using a MAF ECM with a Speed Density code.