Dynamometer Results & Comparisons - 379 HP - Dynojet Problems?

Hi All, last week I got my '97 M6 C5 back from Tom Wong. He installed a set of Ported LS6 heads (with all new valvetrain) and a 232/234 .595/.598 Camshaft. He also installed a host of other supporting upgrades.

After his tune - my car made 400 whp and 362 wtq on his Mustang Dyno.

Since everyone on "the interwebs" seems to be running on a Dynojet type dyno, I wanted to throw my car on one too and see how my hand ported heads with this cam stacked up against some of the CNC ported heads. I was expecting somewhere near 410-430whp...

So a week after getting it back from Tom, i threw it on Turbo Technologies Inc's Dyno here in WA, and put down 379 whp 350 tq... ( I didn't get AFR... But Tom had it dialed in Perfect on his Mustang Dyno)

I was expecting over 400... Any ideas whats going on?

How often have folks seen a Dynojet Read 5% or more lower than a Mustang dyno? Tom said his dyno usually reads at least 10hp lower than other dynos... sometimes more...

I'm gonna run out and check some things when i get home... like clogged vararam or loose plug wire (which happened to me twice now)

Any other ideas?

:cheers:
Dan

See what the dyno correction was. Maybe the dyno weather station gave a jacked-up correction and made your numbers lower. It happens. :(

See what the dyno correction was. Maybe the dyno weather station gave a jacked-up correction and made your numbers lower. It happens. :(


.98

Uncorrect numbers were like 382...

Bout 65* and 40% humidity... not too bad... Cooler and Less Humid than the day my 400whp Run was done in Vancouver on the Mustang Dyno!

-Dan

How do I check my plug wires? Maybe I'm not firing on all 8 Cylinders?

379 / 7cyl = 54hp Per Cylinder.

54 * 8 = 433hp (Which is where i should be on a Dynojet, or atleast close...)


Since i made 400 on a conservative Mustang dyno, I was expecting 420-430 with this setup on the DJ (similar to what everyone else w/ this setup makes) and getting 379 might indicate a problem with my car?

How often do people see Dynojet type dynos throw numbers LOWER than Conservative Mustang dynos?

-Dan

hell with the numbers...before you go thinking your car isnt running correctly does it seem to run ok? run as strong as it did when it was tuned?

hell with the numbers...before you go thinking your car isnt running correctly does it seem to run ok? run as strong as it did when it was tuned?

Well, It runs strong - i mean, even if it was firing on 7 cylinders and made 379, thats still almost 50hp more than it had... so as far as i can tell it's still running strong. It feels way stronger than it used to be... but is it running as strong as it should be? Hard for me to tell, i just got it back w/ all the power...

It has a phenomenal amount of carbon buildup on the back of my car... I know the aerodynamics of the back of corvettes pull a bunch of shit up... but not normally is it all black carbon... usually its road film...


-Dan

So I brought it back down to Tom Wong and threw it on the dyno.

Pretty interesting results...

The AFR was flat, right where it should be up until about 5200 RPMs... then it DIVES to 9:1... pig rich... and black smoke billows out the back. Which explains the ridiculous amount of carbon crap i've had on the back of my car...

The only thing we could find that could cause the problem (after trying a couple things) was the air meter. Its most likely getting spikes up top, and the ECU is preparing for a massive amount of air by dumping fuel in...

I'm going to replace that and redyno it... we'll see if that fixes the issue.

Of note - the weather was nice, and my car peaked at ~396 whp with a 9:1 AFR from 5200 to 6400 RPM.... LOL With a correct AFR Tom suspects i would've hit ~415whp. hehe

So turns out the Dynojet may not have been wrong after all, and my car may indeed have a problem...

Update to come...

-Dan

to see if you're on 7 cyls, put it in high gear (6th m6 or 3rd a4) and stomp the gas for second at low rpms, and if it shudders like it wants to jump off the mounts, you're on 7

So I went to Tom's last night and made a bunch of passes on his dyno trying to diagnose the problem.


The AFR goes Pig Rich for no apparent reason above 5k RPMs...

We tossed in a new MAF and rescaled the tune - but got the same results...

The injectors, and the Air Flow readings all appear normal. Tom doesn't see any indication or explanation for why the AFR dives to 10:1.

We pulled the Evap line, and some other fuel related vacuum line and checked for fuel... also made a pass - no difference... the car still dives pig rich...

Tom tried pulling a BUNCH of fuel - to really lean it out up top... but, surprisingly, that made it worse... went even more rich... 9:1

I reseated all the injector connections, and wiggled all the injectors, and reconnected the harness wires, and made a pass. (This after 2.5 hours of trying stuff...) and out of no where the AFR was laser flat...

So re tried it again... same result.. laser flat AFR. So we put the stock MAF back on and uploaded the original tune and reran it. Same result... everything seems fine now...

I'm not entirely sure what, if anything, we fixed. And/or what the problem was.... But for now, i guess my only option is to watch for clouds of black crap out the back again, and use that as my indicator to if i start running rich again...

Tom also suggested cleaning all the grounds... especially around my PCM...

Does anyone have any ideas where the extra fuel would be coming from, and/or what might be going on there?



:cheers:
Dan

Check to see if your cat protection mode is dumping fuel. Many pcms will dump fuel to protect cats at higher rpm. My 2007 Suburban did it. After we fixed that, we gained close to 30 rwhp.

Check to see if your cat protection mode is dumping fuel. Many pcms will dump fuel to protect cats at higher rpm. My 2007 Suburban did it. After we fixed that, we gained close to 30 rwhp.

Hmm - Thanks for the Tip Patrick! - I think Tom mentioned something about the Cats but i didn't quite hear him - damn shop fan was really loud. I'll ask him if he remembers checking that.

Any other ideas are welcome! :)

Thanks,
Dan

Check to see if your cat protection mode is dumping fuel. Many pcms will dump fuel to protect cats at higher rpm. My 2007 Suburban did it. After we fixed that, we gained close to 30 rwhp.

Tom said "That's too easy...and yes it was disabled..." hehe - I figured he would've checked something like that, lol - i hope i didn't insult him any by asking! hehehe

What are the options for monitoring AFR while driving?

-Dan

Wow, sounds like a handful but you're on the right track! Good luck man, keep it up. You'll be harassing local ricers in no time :thumb:

I'd try to scan your PCM while at WOT and send the file to someone on the board that may be able to help. That's my advice :)

to see if you're on 7 cyls, put it in high gear (6th m6 or 3rd a4) and stomp the gas for second at low rpms, and if it shudders like it wants to jump off the mounts, you're on 7

how does that work?

If you have headers, just get your brother's squirt gun and hit the primaries while hot. The difference in steam will be obvious, someone on here posted. I've never tried it, and I'd think they would all be so hot it wouldn't mantter, but that's what I've heard to do.