I finally got out to the dyno after having Stage II Katech heads and cam installed. Thanks to Paul and Geoff and the guys at Thunder Racing. They run a clean shop and are very professional.

I was a little disappointed in my numbers. I followed an '02 ZO6 which was making 415+ RWHP with just a cam, exhaust, and headers. I didn't get near that level.

My 3 runs ended up as follows: 1. HP=391.2; Torque=349.2
2. HP=382.3; Torque=351.9
3. HP=389.3; Torque=352.7

I keep getting a drop in power consistently at 4400 RPM where the computer retards the timing like crazy. My air/fuel curve is a nice flat line across the band with 17.5 max.

From what I've seen and heard, with the mods I have - all bolt-ons and Stage II H/C, I should be at least another 20-30 hp and ft-lb. torque. Anyone with ideas or suggestions as to why we ran so poorly?

I tried to post the graphs themselves, but the server won't let me put .jpg images on my CF homepage. Ever since the changeover, the forum is running like crap on my Mac. My DSL download times seem like dial-up!

My final disappointment of the day was that my nitrous wouldn't work, so all of the runs were NA. :mad

So, what do y'all think? :confused:

 

You need to get Thunder to do a custom tune on the dyno. A/F should be around 12.8 to 13.1 on a NA Dynojet head/cam run....17.5 is wayyyyyyyyyy lean causing the KR and a loss of HP. :cheers:

 

99HRDTP.
You need tuning bad, A/F is way off as stated above.

You don't say if your running an M6 or A4. Automatics don't dyno as high, check my signature.
Caholo1 :flag :cheers:

 

Better tune...what size cam did you use...a TR 224 with those H&C and all the other goodies...headers, pully, air intake, should have yielded you over 400rwhp and close to that with the rwtq. Keep in mind a lot of dyno's are different too. But your AFR should be around 13.0 with H&C package to be optimal..that is just from what I have seen. average 12.7-13.2

 

17.5 = oh no!!

 

17.5 and they didnt think anything was wrong? Interesting :crazy:

 

what r your cam specs?

what bolt ons do u have?

seems like some proper tuning should help u out?

 

I can't believe that your A/F ratio is 17.5 all the way across the RPM band. I can believe that 17.5 was the "max" just before they stepped on the throttle to start the run. It should have then dropped down close to 13. You need to go back and look at the dyno chart again and look at the A/F ratio in the 4000 to 6000 RPM range and let us know what you find.

- Mark

 

Are you saying thunder racing dyno'd your car 3 times in a row, when each time it was coming out at 17.5/1 A/F the whole run? Did they say anything to you about it?

 

Mark is exactly correct. 99HRDTP is looking at the "max" value the dynojet recorded and it is listed at the top of the graph, just like where your "max" hp/tq numbers are located. Right as you start the dyno, the wideband 02 does spike as you are going from part-throttle to wide-open. Once at WOT, the wideband stabilizes and records the WOT A/F ratio. However, since the dynojet did record this spike, this will show up as the peak A/F number.

99HRDTP's car was not at 17.5:1 the entire run.


[Modified by Jason99T/A, 11:11 PM 11/30/2002]

 

That scares the crap out of all of us, I can't believe no one said anything during the runs, after my h/c we dyno's to around 13 and after the sc we retuned to the same thing, I'm surprised your computer didn't do more than screw with your timing I'm not sure how lean it will go without shutting down.

 

HRDTP - I am not convinced that your numbers are so bad.

We need to know EXACTLY what your mods are (including specs on your cam, compression ratio on the heads, gears in your diff, automatic or 6-speed, etc.) in order to accomplish an accurate differential diagnosis! :D

For example, one variable may be the gears you are running. If you look at my sig below, you'll see that I am running around 380 rwhp with mega-mods and the benefit of Mike Morgan tuning. These were results with 3.42 gears (not the current 3.73's which would result in lower rwhp/rwtq numbers than what I already have).

The dyno numbers are only part of the story. The current set-up gets me into the high 11's on a hot day. On a cool day I might be in the 11.7x's or even 11.6x's.

Once you get the A/F situation and tuning resolved (agree with others in that you should be right at 13.1 with your current setup), I would take it out to your local track and see what numbers you can put down in the 1/4 mile. That is your ultimate BOTTOM line.

Again, I am at least 20 rwhp BELOW 400 ponies and regularly beating the crap out of several cars that have OVER 500 rwhp.

Just my .02 cents.

Gary

 

Whoa, just got back from a Christmas party, to discover 13 replies!!!!!

Thanks for all the concern re A/F ratios. Let me clear things up a bit. As Mark and Jason said, 17.5 is listed at the top as "max air/fuel." Across the band, it runs 12.8-13.6, sitting at 13-13.5 between 4-6,000 RPM.

As far as my mods, here goes:

1. MN6 (of course, it's a hardtop)
2. Donaldson air filter
3. LS6 intake manifold
4. TTS long tube headers
5. Borla XR-1 exhaust
6. Katech stage 2 heads (2.020 intake/1.575 exhaust)
7. Katech comp cam regrind - 224/228 581/588 114 lsa
8. Katech ported throttle body
9. ported MAF ends
10. 160 degree T-stat/HPIII without power tuning
11. NGK TR6 plugs/MSD wires
12. Halltech carbon air bridge
13. KWIS timing chain/gear
14. MAF translator - set at 0, right now
15. NX express 150 shot (not used for run)
16. 3.42 (stock) rear end

I know that some of the above bolt-ons don't mean squat for the runs, but I tried to be all-inclusive.

Does this help clear things up? Any more ideas??


Thanks, again, guys!!



[Modified by 99HRDTP, 1:53 AM 12/1/2002]

 

if you were getting KR on your runs, that'll explain the low #'s. Get your entire PE AFR at 12.4:1 to see how much timing that allows. then start dialing in as much timing as possible. Do you have Edit? if not...get it. you'll need it as the MAFT will not help you any more. (since you will probably have the need to tweek PORTIONS of a table. MAFT is all or none type of thing).

 

I agree with rwj383 and buckmaster that I should have run somewhere in the 400-410 rwhp with the torque around 380-390. Katech guessed around 415 without tuning!!!

This dyno run was supposed to be a baseline to use for a tuning session later. However, with the A/F ratios where they were, Paul didn't see the opportunity for much improvement.

Geoff felt that he could tune around the timing issues, but I can't see why I keep getting the KR at 4400 RPM. The power drops almost 50 hp there and never quite recovers. :confused:

To clarify, the guys at Thunder were very professional and forthright - no BS there. I would gladly let them tune the car.

I need some opinions from guys with simliar setups and/or problems.

 

If your hitting peak torque around 4400, try making the A/F richer in that area of the curve. I have read, in the F-Body forums, a number of posts indicating that putting back their stock MAF increased power.

 

I don't know about the 400 or 415+ numbers you were quoted but I'd be shocked to see you get there. With stage II heads, and fairly small valves, combined with a fairly conservative cam, I'd say that 390 rwhp is not altogether unreasonable...

Just my opinion..

 

Well, first off, 391rwhp isn't super low for a Stage 2 LS1 heads/cam setup. My previous Cartek ls1 heads/cam made 394rwhp, but made 380rwtq. 350rwtq is insanely low for a heads/cam car, something definately isn't right, and I'm guessing it's in the tuning somewhere. Tuned, I'm guessing you'll be around 400rwhp, 380rwtq. Your power is also being limited by a couple of your mods. Switching to 1 3/4" TPIS headers will gain you some decent power. As will ditching the Donaldson and going with something like a Vararam or Vortex ram air. Those two things alone would be worth possibly 15rwhp. Also, ditching the cats is worth big power on heads/cam cars. That would be worth an additional 10-15rwhp on top of what I already mentioned.

Those are just a few suggestions, but you should be able to get around 420rwhp if you do all that. Good luck. :cheers:

 

Don't waste your money switching from a Blackwing to a Vortec..I have had both. My 1997 Coupe w/H&C, TPIS Headers, LS6 Intake, 85mm Pace VV MAF (Z06), ASP Pully, Off Road X-Pipe. made 430/400 RWHP/RWTQ. I doubt very much that switching from a Blackwing to something else would have yielded more horsepower..it is all about filter surface..which the blackwing has the most of. Anyway..I have heard people having problems with MAF ends..maybe it effected your tune..I know that you should be around 14.7 all the time unless you are going WOT..17.5 tells me the "sniffer" must have fallen out of the exhaust when they were dynoing it..did they put the AFR sensor at the 02 bungs in the collector or at the tailpipe..the most accurate is at the collector, but most people do it at the tailpipe..it must have blown out during the dyno to get that AFR reading. A drunk could blow that AFR!

 

No answers here, but I do have some ideas.

Check your plugs, and make sure you are running a proper temp and gap. Assuming those are good and the AF ratios were in the normal rage, you may be getting some false knock. This is a pain to detect, but you can do some trial and error. Run some race gas and put it back on the dyno. If you still see KR, it could be false caused by some other resonance in the motor. Not suggesting this without some careful consideration, but you can desensitize the knock sensors with programming.