I recently got my '00 Z28 on the dyno. The results, i think, were a bit off. My first two runs only netted 260-ish at the wheels. The last run was the best at 271rwhp, 286ft/lbs. The graph was really shaky as you can see. There were a few other cars on there that day, and the graphs were nice and smooth for them. I don't feel anything wrong when driving it. Any suggestions on what to try? Something as simple as plugs and wires? I cleaned the MAF and it feels snappier to the butt-dyno, could that have been all it needed?

I'm totally stock except for a Magnaflow cat-back. A4 w/2.73 gears. Normal results for an A4 w/2.73s?

 

something is wrong. It should be 300/300 at the tire at least. Also look how shaky it is, thats not right.

 

Looks like spark knock.

-Geoff

 

Spark knock? Can't say i've heard that one before. Is that different from engine knocking? Any suggestions? The guy running the dyno even said it didn't look right. The ecu doesn't use the maf for wot, right? So cleaning the maf would just help part throttle duties.

Could it just need a plug change?

 

bs, stock 2.73 autos often dyno under 300.

 

Spark knock being pre detonation in the cylinder. Engine knocking would be from a bad bearing.

I would suggest a complete Seafoam job then new sparkplugs.

And AFAIK the PCM still uses the MAF for WOT. It doesn't use the O2s but it still uses the MAF.

 

PCM uses a blend of the MAF and MAP sensors under 4K RPM. Above, it's pure MAF. If the MAF was dirty and reporting false numbers, your AFR could be rich or lean....which would lead to you being down on power from too much fuel or too little (causing knock - and the PCM would pull timing).

Also, lazy O2's can hurt because the PCM assumes what's happening during normal driving happens at WOT. So, if you happen to show lean at cruise and the PCM has to add in fuel, those positive trims will be carried over to WOT to make your AFR richer. Keep in mind, it will only add - not subtract - as a safety precaution.

 

Well, ok. Guess that could explain why it feels snappier all around after i cleaned the maf, it definately got rid of the part throttle bog i was getting. I'll hit it was the seafoam and change the plugs next.

Thanks guys! Any other recommendations, i'm all ears. I love cz28.com!

 

"It should be 300/300 at the tire at least"

yeah welcome to the world of mis-information and resulting in disappointing dyno results.

in all reality only some cars actually dynoed over 300rwhp.

and most of those were m6.

now the numbers are a bit low, i wouldn't say rediculously. if i had the same car, i would have been expecting about 290rwhp.

simple things like plugs, wires, o2 sensor, dirty maf and age could easily drop those numbers.

 

Congrats on the improvement!

The reason I would say spark knock is that when it is jagged like in your graph, it is a result of the PCM continually adding and retarding timing. Not always, but sometimes it looks like that.

-Geoff

 

If it was a 98 and did the numbers above i would say okay. But the majority of 99+ cars did 300/300.

****, most 01 and 02's did 300-315rwhp stock. I know that have a ls6 intake and some had ls6 blocks but still, its a little low.

 

LS6 block does nothing for HP. The 01 & 02 models did dyno better because of the LS6 intake you mentioned and also because the stock manifolds flowed better (about the same as shorty headers).

2000 auto with 2.73's should dyno 280-285 stock. With Magnaflow I would expect to see 290. So the numers are low IMO. If you got the money I would change the plugs & wires, get LT's and then a dynotune. The tune alone could fix your problem but if you're gonna tune it then may as well get headers on first

 

M6 cars yes; 300-305ish rwhp. Someone could prove me wrong, but I don't believe i've EVER seen a AUTO LS1 dyno above 300rwhp.

 

I agree, my 2001 Z28 A4 with 3.73 and Y3000, with 18X91/2 in rims (larger rolling mass):

293RWHP/345RWTQ (305@5500RPM)

The vehicle has no mechanical problems, runs great.

SteveC

 

That stall and gear are sucking up power tho. Mainly the stall.