NeedforSpd_Z

Ok guys any input here is greatly appreciated on this matter. Over the summer I had the entire top-end done over, new heads,cam,injectors, everything. I sent the PCM to Ed wright to get tuned in for everything to work correctly. Now when we first got the car running something felt totally wrong, the car had just about no pickup. We put it down on the dyno and it make like 200RWHP(before it make 360) So we were like WTF. The Optispark seemed to be a problem so we replaced that and we immediately picked up something like 50RWHP. The car ran much better than before but it still didnt have any pickup to it. We had burned a few wires so we replaced those and the coil and put heatshields on all of them. After all this we turned back to Ed wright sent him the dyno numbers/graphs and then sent him the PCM back for a retune. To make a long story short we ended up sending it back three times, each time Ed made some corrections. Still however the car just didnt run right. Well the guys left the car on the dyno overnight, came back in the next day and ran it cold, and guess what? the graph was perfect! Pulled clean and clear across, and you could tell the car had a whole different feel to it. When you drive it cold its like 2 different cars! Once it gets warm though it loses that "Kick" to it. On the dyno the difference between hot and cold is 30RWHP right off the bat and by the time your at the top of the gear we are losing over 70RWHP. Now I thought It might have had something to do with closed loop so last time I had Ed set the car for open-loop only! But that seems to have changed nothing with the car's behavior. One of my buddies is a GM tech and we are going out tonight to scantool the car to see if there is something we missed or overlooked. We have been scanning it all along, car has shown no knock,no codes and seems to have about 32 degrees of timing at WOT. My big question is what would be causing these problems? Where should I look? Since I know these is a temperature related issue what things is the car looking at when its hot compared to when its cold? If you took the time to read this mess, Thank you! It is greatly appreciated! I just dont know where to go from here...

AFR Ported LT4 heads 2.02/1.60 valves
LT4 Intake Manifold
30lb SVO Fuel Injectors
Centerforce Dual Friction clutch
CC 224/ 236 blower cam
GM extreme duty timing chain
Pro magnum self-aligning 1.6 rockers
Compucar wet nitrous kit 75-150HP
Custom PCM tuning by Ed Wright
Powerdyne 6lb Supercharger
MSD6AL ignition Taylor wires TR6 plugs
AS&M 1 3/4 headers and AS&M 2 1/2 Y-pipe
Borla 3" cat-back exhaust

The Big Show

iTrader: (2)

I'm a little confused, did you make 360 before the heads/cam/injectors, etc..?

Arctic LT4

The big show ? for you when you bought those heads were they a direct bolt on? If so how much power did you gain?

As for the Vette my car has lots of problems when it gets hot and runs like a dog. when i got a 160 therom. it helped a little but not much.

ChrisB

If you still have the stock coil you need an aftermarket one ASAP. You might also try an ignition box, though I don't think this will help.

You can stick a resistor in the temp sensor by the waterpump - this is what the pcm reads off of. Use a multimeter to probe the sensor and determine the resistance when cold. Replace with appropriate sensor in harness. Now let the car heat up and see if you still have a good dyno.

If everything works great than it is a computer problem - if you have the problem still (with the temp sensor fooled) then you have something causing the issue besides the pcm - again, coil is my first guess.

Chris

SloRvette

Did you get this figured out yet ?

If the sensors are reading right, check the airflow numbers, hot vs. cold. The LT1 maf is temperture corrected internally.

A/F numbers getting screwy when hot ?

NeedforSpd_Z

Guys sorry so long on the reply. Internet has been down for 3+ weeks. To answer your questions yes bigshow it made 360RWHP before all the new stuff. Chris we tried putting in an aftermarket coil but it didnt change anything so we put the stock one back in. I was just about at a loss with this thing when I re-hooked up the scanner to it and took it out for a few road-tests. Well what I discovered from the open-loop tuning was that the car at WOT was adding in alot of timing(up to 36) and since this being I blower car I knew that was too much. Also I believe that there are two different timing tables that the car looks at, because at different times timing had some pretty big changes. So I picked up a MAF translator PLUS and I will be playing with that. Hopefully its just some kind of wacky timing advance issue. Guys thanks for lending a hand and trying to help me out, it is greatly appreciated!! I will keep you updated in the future, thanks again for all the help!