Latest SNAFU with Vette

[UB2 SLOW]

I got back from the Dyno and I picked up some more HP. I am now turning out 313 rwhp and 300 rwtq. If my math is correct this is 391 HP and 375 TQ at the crank. Not too bad for an Auto. I still have one nagging problem. The power curve gets eratic about 5600 rpms and does not smooth out. It stays eratic until the 6200 rpm shift point. I can only come up with 2 possibilities. 1) the timing is off. 2) I might be getting fuel starvation with the stock pump. I am pulling alot more HP with the original pump still on. What do you think?

 

[69MyWay]

I think you are picking up spark retard from either noise in the engine, or actual spark retard.

My suggestion is to run the LT4 knock sensor module (if not already in place) and hook a scanner to the car during the dyno run to determine if you are getting knock retard at that point (which I really do believe you are).

If it is true knock retard, raise your fuel pressure to avoid being lean there, and or use a cooler spark plug range.

If it is just noise in the engine, the LT4 module will help, but you can't always get all of that out.

Go with a thicker oil, heat wrap your headers, and make sure you don't have excessive noise in the idle pulley or self adjuting tensioner. All of these things will fool the computer into thinking you have spark knock, and kick the timing back.

Finally, you can just reprogram the computer for a tad less timing at that point to avoid the erratic jump back and fourth.

 

[UB2 SLOW]

I got the LT4 knock module in place and I have raised the fuel pressure just in case. The car does lean out at the hight RPMS.

 

[69MyWay]

If you are getting lean, do you know if the spark retard is kicking in?

Sounds like you need a different program for the ECM that gives you more squirt on top.

 

[UB2 SLOW]

I am considering sending the ECM back to Ed Wright with a Dyno print out, but that would leave me walking for about 2 weeks.

 

[JohnnyC]

How did you calc the horsepower? I thought it was 85% loss in the trans, etc... that is 313 / 0.85 = 368 hp? I guess you used 80% as your loss. Which is correct/more accturate?

Is auto 80% and manual 85%?

Either way, congrats on the 313 rwhp. Nice job!
John

 

[UB2 SLOW]

I used 80. I have an Auto:eyerole I wish I had a 6SPD.