My GS finally made it back on the dyno on Saturday (Dynojet 248C). I was hoping for about 350+rwhp, but I came in at 344.8rwhp and 334.1rwtq (SAE) on the first pull, which I was still fairly happy with. Second pull was down about 6rwhp, I think mainly because the coolant temp had climbed from about 190* at the start of the first pull to about 220* at the end of the 2nd. The previous owner had dynoed #470 when it was stock (293rwhp) and after only the Hot Cam (326rwhp), but this is the first time I've dynoed it since I got it. Current mods are in the sig.

Since I had never done this before, I wasn't sure how the process normally works. I was expecting one of their folks to be at the wheel when they were getting readings on the dyno, but they put me behind the wheel. Is this normal? I was a little nervous and got out of the throttle a little before redline on both pulls, but it did look like power was still building at that time (which probably makes sense because of what's been done to the car). This is also with a stock computer program. I'm still hoping that with some adjustment of the AFPR, programming (probably Ed Wright) and pulling to 6300 my goal of 350+rwhp is still attainable.

Here's a link to the dyno graph: www.jaderenterprises.com/todd/images/gsdyno1.jpg

In case you care, I also got a short video clip of the car on the dyno (approx 5MB): www.jaderenterprises.com/todd/images/gsdyno1.avi

No cats, longtube headers, Corsa, 6000+rpm and a small concrete room = VERY LOUD

tje

 

Nice numbers I have seen 02 ZO6's with those same numbers :cheers:

 

Yep, all sounds normal to me. When I dynoed my 85, I backed it up on to the dynometer and I went through the gears (automatic; operator telling me what to do) and then once it clicked into drive (had to get the car up to about 45mph) then the guy just said "Nail it till I tell you to stop." So I buried the throttle and spun my basically stock L98 up to 5200rpm (To get the 5250 mark). It was quite a feeling, setting there in my vette, with the throttle buried, watching the tach wind up, and going nowhere! :crazy: Good pulls though. :)

 

GS470, those results sound just about right. With a good tune you will reach your goal without doubt. It sure is nice to see actual dyno results from these various parts.

The stock number, 293 , is about right, and 326 with the hotcam is about right as well. So a total of 52 rwhp were picked up from filter/lid, TPIS headers, no cats, Corsa catback, hotcam. You probably are not getting too much from the throttle body but it will help as you build more power. With a custom tune I am sure you will be at 350+ rwhp, which again , is about right.

Car should run about 112-113 in the 1/4 mile. Those are '01 Z06 trap speeds........nice.

I am still waiting to see what mildly porting the intake manifold and putting on the correct LT4 gasket do on the dyno (maybe that would be a relatively inexpensive next mod for you :) )

Anyway , good luck and nice numbers. I will be doing just about the same mods to my car in the coming months.....nice info. :seeya

 

:eek: Nice Numbers!!

I can't wait to slap on my 190 AFRs, LT4 hotcam, and headers. I plan on going with shorties because I want to retain cats and I don't have the money to buy TPIS headers after the heads put the dent in the wallet.

Maybe down the road I will upgrade to TPIS LTs and get random Cats.

:cheers:

 

Man I would like to know what I am doing wrong. My setup only put out 285 rwhp and 333 ft/lb :confused:

The next day my tranny took a dump, so maybe my numbers were off. Who knows? :rolleyes:

 

I've seen a lot of discussion on valve springs. When looking at Todd's dynograph, are the spikes at the upper rpm ranges potentially the result of weak valve springs? :confused:

I'm asking because I plan to install the LT4 HOT Cam later this year in my GS. :cheers: :cheers:

Jim Mason
'96 Grand Sport #007

 

Nice number GS470

ski_dwn_it Maybe your number were so bad because of your trany! we worked on a Camaro it would not do anything until we changed the trany.

Jay

 

Nice numbers dude, good work! :cool:

 

Looks like you are pretty well dialed in now. You may pick up a few more HP with a custom tune. Congrats :cheers:

 

I agree totally with this. Either the stock computer or the stock springs are hurting you. Just to be on the safe side I'd look into this more. Nice numbers by the way :cheers:

 

I mentioned valve springs in an earlier post. If the tires were slipping on the dyno drum for some reason, I suppose that could result in the spikes you see as well.

:flag

Jim Mason
'96 Grand Sport #007

 

Thanks to everyone for the replies and comments.

Shriker - You mentioned using the "correct LT4 gasket". Do the intake manifold gaskets from the factory not match up properly? I know Jim Mason (owner of GS007) did some of his own intake porting and his combo of bolt ons produced some good results.

A couple of you commented on the spikes in the graph in the upper RPMs, I was curious about the feedback I was going to get that. One of the main guys at the shop, who struck me as very sharp and apparently has a very extensive background in high-perf engine building and tuning (I heard this from others in the shop), thought it was ignition related. He said the dyno itself isn't able to detect small HP/TQ variations like this and it was more the result of electrical impulses in the small dyno room affecting the dyno readout (something like that). He said he thought the charge going through the wires and plugs was breaking up enough to cause it and that an MSD would remedy the situation. He wasn't doing a hard sell on this, but this was the opinion he gave me. Any feedback on this??? BTW - As you may have heard in the video clip, the car sounded smooth through the entire pull. If it was valve spring related, would I have heard the engine start to miss??


[Modified by GS470, 2:05 PM 6/19/2002]

 

:confused: Hmmm the first comment implies EM Interference with the dyno equipment. The last comment implies the car has a weak ignition system. I suppose either is possible.

Since the spikes begin around 4700 rpm, I'd be surprised if it was coil related. The LT4 winds past 6000 rpm so I doubt the stock components are lacking. Old or failing components are another issue :nonod: The MSD module may crutch the old components until they fail completely. If it is ignition related, it's more likely time for new plug wires or optispark. If those are new, I'll stick with valve springs or tire slippage on the roller as possibilities.

:seeya

Jim Mason
'96 Grand Sport #007

 

In my signature is a link to my website where I document the intake manifold porting and other comments about the bigger 12367777 gasket.

 

I've always heard that if you want to turn past 5000rpm you need ignition
upgrades on any GM. Just my .02

Nice #'s :cheers:

 

VERY NICE NUMBERS!!!

just a small suggestion, your tuning actually looks pretty good, i would be curoous to know what your fuel pressure is being that your running rather on the rich side, 11.9-12.2 is a little richer then you need to make your best power. given the straight line across though it looks like maybe a PSI or two less would get you a little leaner to about 12.8-12.9, this could make as much as 5-10 RWHP in some cases.

as for the spiking, maybe springs, maybe ignition, but springs are generally higher in the rev band, unless thay are just all worn down. i would like to see a log of that dyno run, it would give alot of the info you might be interested in finding to help track the culprit.

but congrats that a gorgeous and FAST Car i bet!

Chris

 

Above 5000 may be an issue with stock Gen 1 HEI ignitions, but I don't think that's the case with Gen 2 Optispark ignitions. GM specs the hp peak at ~5800 for the LT4, so I wouldn't think they'd short change the ignition components....'course then again :jester

Here is a link to LT4 dyno runs, all of which show hp peaks around 5800/5900 rpm. All are pretty smooth above 5000 rpm as compared to what Todd experienced. The second link is my dyno run.
http://www.hashmarks.com/dyno_page.htm
http://www.hashmarks.com/dynos/mason_dyno.jpg

:cheers:

Jim Mason
'96 Grand Sport #007

 

Good numbers :cheers:

 

Great results! As suggested above, take a few psi out of the fuel pressure and in your case power should go up. Before I installed my ported heads (flow 257 cfm @ .550) mine showed 327 rwhp.

Thomas