Hi There,


I was hoping someone on the forum could help me out. I recently purchased a 1997 C-5 (automatic). To increase it's performance, I have done the following:

- Dynatech headers & hi-flow cats
- B & B cat back exhaust
- Yank SS3800 stall
- B & M tranny cooler
- 3.42 gears
- ATI Procharger (7 psi)
- Granatelli mass air flow sensor
- BBK 80mm Throttle Body
- Weiand Lingenfelter manifold (polished aluminum)
- LS1 Edit


I have had the car dynoed on a Dynojet. It produces 427RWHP and 467Ft/LB of torque. I have read articles on the supercharger, so I know what others have experienced. I also know what the manufacturer claims. I am quite happy with the torque results, but I figured I should have been somewhere around 450RWHP with only the S/C and without any other mods. With the additional mods, I would have expected to see higher numbers.

Does anyone agree or am I just crazy??? Any insight/thoughts would be greatly appreciated. I did not do any baseline testing prior to the mods. However, my best 0-60 time was 4.97 seconds (prior to the mods), and now it is 4.47 (due to severe traction limitations). I think I will need larger wheels/tries, but that is a whole other discussion...


Thanks,


LS12NV

 

I agree, sounds kinda low. Tell us more about the supercharger kit - is it a "stock" ATI system or did you purchase and install a tuner's kit such as ECS or A&A's?

Before I forged my engine and added the blower cam, my stock LS1 with a ECS Procharger Kit, Kook's 1 3/4 headers, hi-flow cats and Borla Stinger exhaust made 519HP at the rear wheels.

Who tuned the car for you? Perhaps you have left HP on the table?

 

It was ATI's "off-the-shelf" kit. I also think the numbers are low, particuarly given what I have read in various articles about this set-up. I think I need to go back to my mechanic and ask "what's up???".



LS12NV

 

getting horsepower is all in the tune. You should easily see 475 RWHP with your set up. How much boost are you running?

 

You should be above that for sure, it has to be your tune. Go back and ask about it or find another tuner.

 

Lets see,
Your 467 torque figure would indicate that you have good mods.
Your 427 RWHP indicates to me that something is wrong-top end.
Most likely fuel starvation, filter, pump, or need booster.
However your tuner should have stopped everything and told you that something is not right when he saw the ratio of the numbers.
Go back and discuss, if his face is blank-find a new tuner.

In an older '97 you might expect 427 RWHP (w/A4) just from the ATI, add in 25 RWHP for exhaust, maybe 10 or less for Granatelli MAF + 80 mm BBK, say 460 RWHP. I don't know about the Weiand manifold-I've seen it compared to LS6 and FAST in a magazine article and it came out on the bottom. If Lingenfelter ports it completely you might get an increase at top end with a cam. But lets add in 10 more RWHP.
Now 470 RWHP w/467 RWTQ. RWHP still seems low at that torque.
Given that the torque is correct-still goes back to lack of fuel on the top end or of course our usual problem with belt drive things-belt slip!

Check the belt/pulley areas for rubber dust/particles.
The stress in the belt drive is proportional to the power consumed by the blower, so it could be not slipping much at peak torque, but significantly at 6000 RPM and 7 PSI boost due to the rapidly increasing power requirement (cube of speed) of the blower.

Again if your RWTQ is correct, you shold be pushing 500 RWHP.

Roy

 

when you're happy with peak torque, but not with peak hp, on a centrifugal mechanical sc where boost rises with rpms, then check knock retard.

If you don't get knock retard check belt slip or a plugged up cat.

If you get knock retard, check the air fuel ratio from a wideband.

If you are running lean, check fuel pressure.

If you're OK in air-fuel ratios but still have KR, then probably you're running too aggressive timing. Note, your aluminum intake absorbs much more heat than thermoplastic intakes. That means the charge air temps between hot engine running and warm engine running is notable. A reputable Michigan tuner discovered the same issue on a Ram Air LS1 f-body with a vortech and alum. aftermarket intake when trying to chase away detonation. So make sure your engine is running hot before dialing in the timing.

 

I'm running 7psi - that's the standard tfor the C-5 kit. I could upgrade, but without doing further engine mods, it is not recommended...

 

Thanks for your suggestions regarding belt slippage. I'll check for the dust particles ASAP. If that isn't the problem, I'll check the fuel pressure/starvation issue with my tuner. I have heard from another Forum Member that I should check the air/fuel ratio with a wideband sensor. Hearing it from more than one person now, I should probably check it out.


Thanks,


LS12NV

 

Dude...you are ok. The hp levels you are seeing with your mods are right where they should be or at least really close. It seems everybody missed the fact you have an AUTO and are running a Yank Torque Converter with a higher stall. You are running 7 psi on a stock internal 97 ls1, through an automatic tranny. Stock hp for a 97 with an Automatic is right around 280rwhp. You are about 150hp over that.

The only problem I really see with your kit, is that it is an off the shelf ATI C5 kit. Check my sig and look for the picture of my ATI kit. It was way before Andy did any single I/C kits. The Radiator is lowered to allow for the use of the stock fans and a cool air intake into the blower inlet. Doing this will increase your ability to keep your IATs lower during the hotter times of the year and allow your stock fans to cool your radiator..unlike the ATI kit fan. It takes close to nothing to lower the radiator. It is an easy fix. Just cut the RAD supports and move them forward 5.5-6", bolt or weld them in place. Purchase a granetelli air bridge and K&N Filter and you will be set for the hotter times of the year. If you need help finding a stock set of fans (in case you didn't get them when you bought the car) look in the C5 parts forsale section or ask the guy you bought the car off of.

Click on link for website pics
http://temp.corvetteforum.net/member...es/shinobis97/

If you are still convinced that you are lower than you should be or that something is wrong because your tq is high (I give credit to the Yank TQ converter and 3800rpm stall). Than maybe your valves are floating at the higher rpms. Do you have the stock valve springs? Maybe the belt is slipping (as somebody previously mentioned). If not one than maybe both. One thing the stock ATI kit is known for is belt slippage, shredding, and overheating. But on a stock motor (cam, heads, etc..) I would say you are not too far off on the power levels you have.

 

Thanks for your note. Impressive photos of your set-up!!!

In response to your question, I am still running all stock internals, including valve springs. I am going to investigate the belt slippage problem and potential fuel starvation issue. I think I may want to either adjust the fuel pressure (I have an adjustable fuel pressure regulator, but don't know what psi to run with a S/C), or invest in an umpgraded fuel pump (Racetronix). I really want to understand if there truly is a problem before I go out an begin replacing parts on a guess.

Thanks,


LS12NV

 

If you want email me your dyno sheet or post it. I will take a look at it, and tell you what is happening. You have the 97 FR, you are already in pretty good shape. We need to take a look at what the AFR is doing after 5500rpms.

When the valves float the hp will drop dead in the upper rpms. With 7psi and a P1SC, I am going to guess that you are running at least a 4.25" pully. The bigger the blower pully, the least likely it is to slip. I would not push more than 9lbs on a stock LS1. You are safe at 7lbs.

What you could do is swap in a bigger cam and some dual valve springs. You will then break the 500rwhp mark easy and maybe even up to 550rwhp. Having a 97 makes it easier to mod because your fuel system will only require an aftermarket FP. Your existing fuel system should support 450-500rwhp. Hell I dyno'd my car up to 600rwhp with a D1 and 01 fuel system...but it started to lean out at 6200 rpms. That was the first time, over 2 years ago.

 

I am with Shinobi as far as replacement of the valve springs... I bet that is one or maybe all of your problems.

VR