A couple months back I had my car tuned and it made 432/395. Peak power was at 6750(redline) due to being out of injector. Car was sd tuned. Mods were...

Stock ls1 block
TReX cam
Stock 799s with patriot gold kit
Longtubes
Fast 92/92

Yesterday went to tune the car on a 150hit. Made 2 n/a pulls prior to tuning on spray and the car made 409/390 but the curve looked like someone put a 224cam in there while I was sleeping. Made peak power at 62-6300 and went down pretty rapidly to 7k. I believe it was in the 370hp area by 7000. Only change to the car was routing the air intake from the engine bay to the fender and switching from tr55s to br7ef's and changing from stock wires to msd 8.4mm wires. Same dyno, same gas. Tuner said the car was not seeing any knock.?? WTF?


On spray the car made 537/614. Timing didn't seem to matter, and I fear we didn't get enough out. Started with 8deg out made a pull, then 9 out, the put 3deg back in(6deg out) all within 5whp of each other and 7tq of each other. So he put it at 9deg out and concentrated on fueling. After we got finished I called some friends and they were saying that it may not have had enough timing out? What do u guys think?

 

If the power falls off that hard, it sounds like valve float.....?


What's your timing on motor? Did you read the plugs after a bottle pull? It's hard to get an accurate n2o tune on a dyno, but I'd think that's plenty of timing out to be a safe starting point.....then take it to the track and see what the plugs tell you. (after you get the n/a stuff figured out!)

 

Going to the track Sunday to see what it does and I'll read the plugs and go from there. As far as the na tune...valve float is something I was thinking but I only have 1500 miles on these springs.

 

post pics of dyno if u have it

 

Nitrous graph



Na graph from before



And sadly I didn't get one of the na pulls yesterday.

 

looks like u have a fuel issue have u watched your fuel pressure while under load?

 

I have not watched fuel pressure during a pull but afr stays solid.

Went back to the dyno Saturday and had jim pull 3 more degrees and we lost 25hp on spray. So he put it back how it was.

Sunday first pass off the trailer, 9.74@138 car felt great plugs looked a little rich so I went from 33 fuel jet to a 31. Afr went to the low 12s and we picked up 2mph but never e.t'd better than the 74. Car will go 9.50s on the 150 shot on a good pass with the tune up where it is now. This is with me shifting to 5th just after the 1/8th. Get a different gear in there and try to rev 4th out and we will see what it does.

Never made a motor pass cause we didn't have time but I will address those issues as soon as I can. Not sure if the longer intake pipe and colder plugs may have hurt the curve or if maybe I got ahold of some bad gas, idk.

 

You said it was running out of injector, but I didn't see where you said you installed and tuned for larger ones...

 

it ran out of injector at 432whp at 6750rpm, not 409whp at 6300rpm, And when it was " running out" it was at 98% duty and we decided not to push it further. So really there was a slight buffer there.

 

From what I gather, ~80% is the max you want them to see very often and anything over 92% is completely unacceptable.

 

do a compression check or a leak down test on some cylinders.remember to short shift with NOS it makes power sooner then NA.check your springs and push rods for broken & bent.

 

Haven't done a compression check or leak down but I did put a heat gun on the runners of the headers and all were with in about 50degrees iirc. The corners were slightly higher but all within a good range. I will do a compression test sometime this week but would it trap 140 down a cylinder?