Today is a very sad day for me. I finally dynode my car and it turns only 271RWHP and that’s with opened air box, K&N, MAF ends, adjustable fuel pressure regulator, and A&A exhaust. I was hoping for 310HP but got 271.1HP and 280.2 TQ on my first and 265.7HP and 281.4TQ on my 3rd. On the third run, the upper rpm range, the HP and TQ line looked like a saw blade. It was about 90 degrees outside and no fan to cool the car. The coolant temp was over 200.

Before the dyno run, I got a code: “P1626 Theft Deterrent System Fuel enable Circuit –C”. I have never received this code before. But it went away and everything was fine during the dyno. There were no codes related to the car after that except the typical traction control/abs system code. What’s wrong with my car?

I bought it used at 19k miles and it is currently at 39k. It does not consume oil; I have just changed the oil and radiator fluid. The clutch is a little weak but it is still holding ok. The computer never threw any codes except for the left door control module. The dealer replaced the PCM once when it had the “reduced power” message at around 28k miles. Dealer won’t tell me what happened. The car idles at 650rpm but it sometimes it does this little rpm dip during idle and the lights will get dim at night. Again, it never threw codes. Also, the computer never keeps the average MPG in the system. It always starts at 0.0 MPG every morning. Do you think the PCM is bad? The fuel pressure regulator is set at 55 PSI from the factory 58(mine OEM regulator was running 60psi).

The guy that Dyno, looking at my dyno graph says it may be the sparkplugs, I have not changed the plugs because I was going to do it at 40k miles. I could be fouled and the computer is retarding the time? But do you think sparkplugs can really take up 30 to 40HP??? I am going to replace the plugs, wires and clean the fuel injector anyway. I can order NGK from LAPD or I can just get those Bosch Platnum +4 from pepboys, which ones should I buy?

When I installed the bolt-ons, I did not notice differences in power gain or loss. Also, I don't think the car has gotten worse or better since I bought it, it is my daily driver. What’s wrong with my car?
:sad:

 

Wow that does seem awfully low. I have an automatic 98 that I dynoed at the first corvetteforum cruise-in and got 302 RWHP. MY friend had a 99 6-speed stock and got around 320 RWHP. From what I understand is 6-speeds make more RWHP than automatics. I would try another dyno at a different place just to make sure. :sad:

 

Your numbers are low but there could be several reasons that don't indicate a chronic engine problem.
1. Was the dyno operator experienced? Was the car positioned properly on the rollers? 4th gear pulls?
2. What kind of numbers were similar cars recently running on that dyno.
3. Bad gas and/or knock retard
4. Were air/fuel ratios measured and if so what were they?

Have the car checked on another dyno before you worry too much.

 

Sorry to hear about that. Could it have been a bad tank of gas (are you using premium fuel)?

Borrow someone's autotap and see what it has to say about your timing, air/fuel, knock retard, etc. Also, post your dynograph.

Good luck.
Cliff

 

1. The dyno guys seems to be experienced, it was my first pull. I know a lot of F-body buys dyno there and one of the owner used to have a F-body. It was a 4th gear pull.
2. He usually sees F-bodys pulling 290HP and C5 pulling 305HP.
3. Yes, it could be bad gas. Wife put in Costco gas 91 octane ... Is autotap the only may to check knock retard?
4. Did not measured fuel/air ratio. What is the optimim ratio?

 

If I were running these numbers I would definately take another dyno run else where and then compare before jumping on the fix...Those numbers are surely low and in case the dyno is fine, I would have a good look at that PCM that was replaced...MPG read out should only go to 0 with the battery dead or disconnected or pcm relearn....

 

benelliwang,
I believe the air/fuel ratio for maximum power is 13.3 to 1. Some dynos will stick a sensor up your tail pipe to get this data but I've heard that is not accurate - you need a bung installed upstream of the cats.

 

Benelli...Just to make you feel a little better, mine dyno'd pretty low as well. You can see all my mods in my sig and it dyno'd 308 rwhp. I was upset as well and am now thinking of having my rings replaced and am gonna add stage II heads and a different cam and LS6 intake manifold. Apparently the 97-98's were not making nearly as much rwhp as the newer 99's and up. I have heard of other 98's starting at around your same mark. I am hoping to make it to 380- 400 rwhp someday. :yesnod: Keep the faith!

 

I have a '99 autoand my first pull about 6mos. ago was 286hp. I have added a black wing and a new maf and got 290hp. I have other mods but I was told the maf translator would make a big difference. the problem is your air/fuel ratio.

 

Why do you think new rings will have any effect on your HP? That would help on oil consumption, if you have that issue...but nothing I've ever seen indicates that would have any impact on performance whatsoever. :confused:

 

You should run around 295hp SAE corrected on a Dynojet with an unmodified '98 6sp., and the open airbox should give you around 10hp more (+/- 3-5hp for car variance). Something is wrong, but the possibilities are endless.

 

Definitely change the plugs. It is cheap and easy. It can't hurt. Go with the copper plug...I have the NGK TR55's. Definitely check your air/fuel ratio. :cheers:

 

[QUOTE]Wow that does seem awfully low. I have an automatic 98 that I dynoed at the first corvetteforum cruise-in and got 302 RWHP. MY friend had a 99 6-speed stock and got around 320 RWHP. ]

Those #'s seem awfully high. Most stock C5's from '97-'99 dyno at approx. 280 RWHP for A4 cars and 295 for 6-speed's.

You are probably off by 10-15 H.P. which could be anything from off timing, bad fuel or a faulty spark plug. How the car idles and runs will tell you alot.

 

Well guys, thanks for the replies, I just ordered NGK TR55, MSD 8.5mm Super Conductor Plug Wire and Redline Fuel Injector cleaner from LAPD. Hope this helps the car a little. Also, I am looking to check my air/fuel mixure and the knock retard. Is AutoTap the only way to check this? Also, I have a adjustable fuel pressure regulator and I set it per instruction of 54psi at idle. Should I re-adjust it to a different setting?

 

I still have my dyno sheet from Breathless Performance. If my calculations are right my car would be at 362 hp which is about right considering I have a Donaldson intake,corsa exhaust, and hypertech programming. The car stock is at 345 hp.
I would think around 290 hp for stock automatics considering the 20% drivetrain loss. Sorry I probably should have noted I had a couple of mods.


[Modified by vette9898, 10:59 PM 4/22/2002]


[Modified by vette9898, 11:04 PM 4/22/2002]

 

Will,
If you buy a MAFT and bring it to AZ I will install it and do the Autotap tuning for you... I'm sure I can help you find a lot of hidden HP with just that work...
Shirl :cool:

 

271 that seems real low for a modded engine. Mine hit 322 hp @340 tq


[Modified by RHILL, 10:26 PM 4/22/2002]

 

OK guys, I pulled the #2 and #4 sparkplugs to take a look and I notice three things. First, the #2 plug wire and plug seems to be dirtier. Second, there are some white resudues in the wire socket. Third, the #2 plug wire is cracked! :eek: I did not check the rest of the plugs or the wires. Could this be it? :confused:

The plugs seems to be in ok shape, it is in gray color with no oil or evidence of running too hot (no melting or red colors). But I did notice a greenish gray on the tip of the plugs, is this normal?

I have take some pictures and you can seem them here: http://www.lvcm.com/wwang/C5/Old_Plug/index.html

EDIT: Here are some of the pictures if you are too lazy to click the link:





[Modified by benelliwang, 1:56 AM 4/23/2002]

 

I wouldn't worry about dyno numbers. It's how you use what you have that counts. I guarantee that there are several guys on this forum that could easily smoke my car with me driving with way less horsepower.

On another note, I'd be willing to bet the dyno had something to do with it. Try another one and see what the numbers are. The only really good way to compare numbers is if you and Joe Schmoe go to the same dyno together and he pulls 320 RWHP and then you pull 271. Then you know for sure your car is low on power.


[Modified by QuickSilver97, 2:56 AM 4/23/2002]

 

MDL-01C5..The "ring replacement" was in there because it was one of the things I was gonna fix at the same time as swapping my heads/cam/intake. It was not to increase HP, but to help with my oil consumption issue as you brought up. It should help in keeping my exhaust tips a bit cleaner as well. :D