bigdsz

iTrader: (1)

The above is true and I am absolutely beside myself. When I dynoed today the ambient temperature was 10* warmer than when I last dynoed and the humidity was higher. I was running JBA headers before I switched to Jet Hot LT's and their 3" ORY pipe. I'm very pleased with the Jet Hot products, quality all the way.
Anyway back to my problem- current mods are lid, ported MAF ends, Fernco coupler,Shaner S2 TB, LS6 intake, CC moly push rods, CC 915 springs, CC 216/220 .525/.532 cam, Spec clutch, and Hooker cat back. Before the LT install I was making 355rwhp and 363 rwtq, after todays run I made 353 rwhp and 356 rwtq. I have been dyno tuned with LS1 edit and was running 13.0 to 1 AF. Today I was running about 12.7 to 1 AF, a little rich. I can retune the car and have that adjusted out in addition to picking up a few HP.
The big question is why didn't I pick up 20 to 25 HP like most others? I know my cam isn't that big but I still should have seen some nice gains. As I stated before I love the Jet Hots workmanship, quality, and fitment was superb.
I know heads will help considerably, but short of that what canI do???

99MONGOOSE

Maybe a possibilty of the old tune not running well with the new fuel curve caused by the new headers???????

blk~2000~Z28

Were you picking up any KR? I would look at some WOT runs from before and after and see if that is possibly the reason. Other than that I think this sucks, sorry to hear.

TILEMAN

Did you gain anything under the curve? Or are you just looking at peak numbers?

bigdsz

iTrader: (1)

I gained nothing under the curve one line virtually over layed the other. Since my earlier post I talked with Jet Hot about this matter and they told me I'm not the only one with this problem. They said the problem is not with the headers it's with the Y pipe that the 3" diameter is too large unless you have heads. Todd said that they were going to come out with a 2 1/2" Y pipe but every body objected to that diameter. My guess is that the smaller diameter keeps the exhaust velocity up.

2MCHPWR

iTrader: (10)

that smaller diameter stuff sounds like BS.
i have stock heads. how's my hp look?
i have 3 inch y pipe as well and my collector for the y pipe goes up to 4 inches before being reduced to 3 for the intermediate pipe/cat-back.

did you atap your dyno runs? you should have.

WILWAXU

iTrader: (6)

Hehe.. I love the back pressure arguement. I run 1 7/8 headers and a almost 3" y-pipe on my stock internals car. It runs alright, times are in the sig.

My suggestion. Take it to the track.

TILEMAN

Exactly, sometimes dyno numbers mean squat.

bigdsz

iTrader: (1)

I agree that taking it to the track is the best way to find out what the mods have done, however to me the dyno is a more controlled environment. I've got a M6 and repeatability of runs at the track at least for me isn't as good as the dyno. I've dynoed 17 times on the same dyno and spent 3 hours dyno time with LS1 edit. All I know is that I didn't gain anything from the LT install. I'd like to find out if anybody else has hsd this problem.

soundengineer

iTrader: (16)

you switched from one header to another???
most headers are very similar...most people see maybe 5-10 improvement when you change headers from one to another.I am not suprised at all to see little change...and still in the y-pipe....try changing to true duals and you will see a slight improvement...also when you put in long tubes you usually loose some down low...but you should see the improvement up high...
also you have a cam...did you replace the springs at the same time as the cam???either way...how long has the cam been in.... a buddy of mine lost over 20 hp to springs that were worn out....retune to 13.... my car needed 13.3 to be the best...losing a couple horses to being too rich

bigdsz

iTrader: (1)

The JBA's are shorty headers and they offer little gain over the factory cast manifolds. The main reason for using them is that they are the only CARB approved headers in california.

kulablkta

i added mac mids and ory and only gained 6 rwhp, once funally tuned, gained another 5-10. tuning tuning tuning. i didnt think tuning would of had that much of a different but my a/f ratio was way off. i figured the price of a maf translator wasnt worth it so i forked up the extra cash and got the ls1 edit done to the car and all together gained about 12-15 more rwhp. if i were you, i would check the tuning anf a/f ratio

bigdsz

iTrader: (1)

I'm dyno tuned with LS1 edit, AF is running 12.7 to 1, a little rich. The point is that if I tune the AF to 13 to 1 which is optimum what am I going to gain maybe 5 HP?