08 Supercharged Corvette Tune Advice

[gapd you]

Just picked up an 08 vette with A&A V3 with 3.4 pulley, btr3, fore fuel, id1000, headers, yank 3400, meth,dsx flex fuel. The previous owner ran best of 9.67 at 143 mph so the car seems good on the top end.

However I took the car out for a spin today and the drivability seems pretty crappy as it bogs between shifts. i'd consider my self a beginner/amateur at tuning but im looking for some opinions on where to start here.

I haven't had a chance to log it since the weather hasn't been the best in Chicago and I haven't installed my wide band yet. This car was tuned by a well know tuner.

things I've noticed:

- timing seems low compared to my old cts-v on e85
- injector data seems off(flow rate vs pressure is all the same number?)
- maf curve has some bumps and is not the smoothest
- o2 rich vs lean voltage seems odd
- power enrich looks pretty lean
- im still learning tranmissions but any input is appreciated

Tune file attached. corvette tune.hpt

Any help would be greatly appreciated.

[RobZL1]

I'm not an auto transmission guy, so I can't help there, but here's my take on your notes:

- timing seems low compared to my old cts-v on e85
higher compression motor to start with = lower timing required
- injector data seems off(flow rate vs pressure is all the same number?)
this is due to your fore return system, also the double stoich/half IFR method is in use here (though the IVT terms were not halved, FWIW)
- maf curve has some bumps and is not the smoothest
I agree. This could probably be better with some logging and tweaking. Looks like a quick dyno tune / close enough kinda thing.
- o2 rich vs lean voltage seems odd
it's unchanged from stock. You can change them both to 450 if you like (should probably also spend some time dialing in the Proportional and Integral as well)
- power enrich looks pretty lean
I agree I'd target richer for a centri... certainly not 0.86. More like 0.80

Other things I saw:
- all misfire tables are maxed out and the misfire DTC is turned off. (You shouldn't have to do this in my opinion.)
- you could probably improve idle with a little time invested

[kevin87turbot]

The bogging that you feel during each shift is transmission TM. He's increased the shift pressures and reduced shift times, but left the transmission torque management stock.

As far as the timing, look in the Alcohol Spark table. It will add up to 5.5 degrees to your base table, depending on your ethanol percentage. The base table looks about right for your application.

[gapd you]

Thank you for the detailed description on each subject Robzl1. This helps me out so much. I will work on the suggested areas and hope for some improvement.

If I half ivt will it throw a bunch of things off?

[gapd you]

The bogging that you feel during each shift is transmission TM. He's increased the shift pressures and reduced shift times, but left the transmission torque management stock.

As far as the timing, look in the Alcohol Spark table. It will add up to 5.5 degrees to your base table, depending on your ethanol percentage. The base table looks about right for your application.

What would be the best approach to dial in the torque management? Im still trying to learn the 6l90. Thanks for the recommendations.

[kevin87turbot]

You can go the Transmission Torque Management tab and reduce the Torque Factor by 40% or so. Maybe 50% if you want to be aggressive. I'd prefer to be on the safe side unless you don't mind pulling the transmission for the occasional freshen up.

[gapd you]

You can go the Transmission Torque Management tab and reduce the Torque Factor by 40% or so. Maybe 50% if you want to be aggressive. I'd prefer to be on the safe side unless you don't mind pulling the transmission for the occasional freshen up.

I do not want to be rebuilding the trans. It is still a stock trans in the car. Will 40% be good?

[mbray01]

i would be careful just changing PE, the tuner may have a rich maf curve, and used a leaner EQ ratio to pull it out, although not the perfect way to do it, its common, so just throwing fuel at it arbitrarily is not great advice. Put a wideband on it, log what its actually doing, and make fuel corrections based on what you are seeing in the log

[gapd you]

i would be careful just changing PE, the tuner may have a rich maf curve, and used a leaner EQ ratio to pull it out, although not the perfect way to do it, its common, so just throwing fuel at it arbitrarily is not great advice. Put a wideband on it, log what its actually doing, and make fuel corrections based on what you are seeing in the log

I don?t plan to change PE until I get the wideband installed in the next few days. I will probably log some drivability stuff today to check fuel trims and the part throttle bogging when shifting.

[RobZL1]

so just throwing fuel at it arbitrarily is not great advice. Put a wideband on it, log what its actually doing, and make fuel corrections based on what you are seeing in the log

Just to clarify, I fully agree with this statement. Wasn't advocating just changing PE blindly. Assumed wideband was a given. (Probably shouldn't assume that though.)

[RobZL1]

Other thing you can do to improve driveability is look into flex fuel spark, not just PE alcohol spark. E85 mix wants different advance everywhere, not just at WOT.

[gapd you]

took the car out for a short log on the original tune today still with no wideband installed yet. maf curve looked a little lean. I'm going to richen it up some and make the other adjustments to the IVT, o2 sensors, and the torque management for the next revision. Hoping it will clean up the drivability some.


log 1.hpl

[mbray01]

one other thing to take note of, is if pe spark is active, changing pe, will also increase, or decrease spark based on that number as well, ive seen cars have 3degrees timing added just because they added 10% fuel to the pe table

[gapd you]

Got the fuel looking better on the maf curve with the first revision and the shifts while cruising are night and day difference!

Next i need to figure out what to adjust to keep the rpms from jumping 1-200 rpm back and forth when cruising 35-40 mph. Is this something that needs to be dialed in the trans? Id like to run open loop between 1000-1600 rpm to run richer but the car is on 2bar os. Is there a way to do this?

Planning to get the wideband installed and in the dash this weekend to do some WOT testing.

log and file attached if anyone can point me in the right direction of the rpm surging.

corvette tune 1 torque factor reduced, ivt halved, 02 voltage 450.hpt

revision 1 log.hpl