Spool

[raver0789]

Long story short...

I have an s256et .55 AR on a LNF 09 Cobalt. I rev to 7400, as that is the limits of the cam phasers.

My tuner and I have had no problem getting it to put out top end power. The problem is we get a graph that looks like this, with very weird torque.

http://s1189.photobucket.com/user/ra...tml?sort=3&o=1

Very low torque I would say, and full boost at 4700, which is not where this turbo should spool. It should be 4000-4200 and I was hoping I would get 460 torque to the wheel. Approaching redline, torque looks really high as well there, I didn't think most setups would produce that much torque at redline.

It did have a small exhaust leak between the motor and exhaust housing but my mechanic thinks it's not too bad.
I believe it had a 9psi wastegate spring on my Tial 38mm. I have bought a 20.5psi spring and put it in there.
The issue is not with the boost controller I believe. It is set up and working.

Question:

1) Any tuning advice to make this spool faster? I could retard timing more in the midrange (who cares about fuel economy)

2) How would my new wastegate spring change this entire graph and/or drivability? Am I going to run into surge issues? I figured 20.5psi spring since 20.5 is the least I would run on this setup on pump gas.

3) Do my MALT talbes need to me maxed at 99.99 to get maximum torque, and if i don't, is the ecu limiting this? I thought this would be controlled by boost controller.

Obviously 460 torque to the wheels would make this car ALOT faster.

Thanks.

[cobaltssoverbooster]

pm me if you have a file i can look at. three things spool a turbo faster, more airflow/gas expansion in the header (retarded timing)/and heat. run it lean like .92 until you get a few psi going and retard the timing in that area to force some of the gas to expand late in the cycle. should hel with sool time.


if you dont mind me taking a peak i can find any trq limiting factors for you.

[raver0789]

This may seem a bit insane but since the gm stage 1 tune is so lean aka practically stoic at wot and since the motor is direct injection - think a hint of stoich at wot down low would be okay?

[armcclure]

I wouldn't be complaining about that too much.. Unless you're looking for an excuse to buy a 6-speed swap.

[raver0789]

LOL. I just want the most from my setup.

I already have the 4.45

Not as stout obviously but I think the gear
Ratios are perfect for the power.