Good evening,

Well, the other day I completed my second dyno session after installing the Kinetix plenum and Crawford headers. I did the dyno to prepare for a TS ECU flash, but something weird has come up.

Look at the graph below. No, this does not include the headers and plenum. This is an older dyno. Look at how wavey runs 2 and 3 are compared to run 6. I am trying to figure out what causes this. I know about the smoothing function in the RunViewer software. That is not it. When the runs were completed, the waves could be 25 lb/ft or more. The run operator then smoothed them out before the files were given to me. I mean the swings were huge.

Also, when comparing three back to back runs, the first was always smooth and then the second and third would be really wavey. This happened on multiple occassions.

So, what causes this to happen on the dyno? I have seen it in dyno charts around here before. I am really curious to find out because I think the "waves" are skewing my numbers. I serious think there is an issue here.

By the way, a friend of mine with a roadster and essentially the same mods did a run right after me. He had no issue with waves?!?! Oh, in case it matters, he has a touring model and I think he has VDC, although turned off for the dyno.

The dyno operator first said it was the ECU trying to read the O2 sensors and make adjustments. I pointed out that the ECU has a open loop mode and that sensors are ignored under WOT. He then said it is probably the traction control (which was off).

At any rate, what gives?

 

Oh, I forgot to mention that Doug from Crawford looked at these, and other results. He thinks the waves are really strange as well. He has not seen them before at all. This made me even more suspicious.

The dyno is a DynoJet by the way.

Tires used during the run were stock RE040's, with little remaining thread in the rear.

 

Get a re-dyno from another shop and compare it. Sometimes dynos malfunction and give unaccurate readings. That's what I'd do..

 

Maybe the car wasn't tightened down enough and the tires were slipping?

Also could be your clutch.

If this is an old dyno, how was the new one? Lets take a look.

 

I would of course, but we only have one local dyno shop. There is another, but the guy is in the business of building mobile DynoJets. So, he only has one in stock to use on occassion. Also, he sold the dyno to the shop I used.
The clutch and the strapping is something to consider. I doubt the strapping was an issue, but the clutch could be the issue. Hmmm...never thought of that before.

As for posting the other dynos, I don't want to do that just yet. Obviously, I cannot get a clean run in. If I posted the dyno including the Crawford headers and Kinetix plenum, people would read too much into it. They would think that the products are not so hot when in fact it is the dyno run that is borked.

Hmmm...I won't be able to determine if it is the clutch anytime soon. Only way to do so is to get a new clutch. I guess I could hit a tall hill in sixth and see if it slips. I haven't felt any slipping yet, but my butt is not that sensitive. Maybe I will have the chance to hit another dyno soon.

 

the ignition wire they hook up to read the rpm, sometimes they dont get a good connection and it causes something that looks like static on dyno graphs.

 

the slipping inssue could be the answer, but hardly. when we dyno'd a 600+ whp S2000 at my shop, when it would slip ( it slipped even in fourth gear) it would just show a lower HP reading. the waves don't look that evident. however, given the nature and size of the two cars this could be the answer to this problem.

john

 

Yeah, the more I thought about the slipping the more I wondered whether that was it. If the clutch did slip, the line on the graph would dive and head hard right (decreased HP detection but accelerating rise of RPM). Who knows though. Maybe this is an excuse for a JWT clutch and flywheel

You wanna see waves, the image below is uncorrected from the shop. It is hard to see, but look at the yellow torque line at 4500-5000 rpm. It has a 25 lb/ft wave. And no, these are not the Crawford/Kinetix runs either (oh, and ignore my A/F. That is getting corrected soon):

 

do other cars dynoed on this dyno have these waves?

 

I've seen issues like that rise from lean AF ratios/ detonation....remember, you can't always hear detonation.

--wes

 

My guess is the knock sensor pulling timing. Not sure why it would spike up like that though, unless the lean AF causes the increase in torque and then detonation, which activates the knock sensor, which retards timing, which lowers power but stops detonation, which allows the timing to advance again, and then the process repeats.

I don't think a slipping action would cause spikes at a frequency that high, and I think you'd notice it. I notice that the fluctuation starts when the AF leans out a bit, so that's why I think it is the knock sensor.

Instead of dynoing at a different place, maybe you can add some octane booster then run again with everything else the same to see if that makes a difference.

-D'oh!

 

when i dyno'd my Z, final results came to 252WHP. it had no waves what-so-ever. just a clean line throughout the entire RPM range. with my experience, ive seen those type of waves on two cars. my TT supra had similar waves to tho. its was a result of boost spikes and A/F, and the 600+whp s2000 with its incorrect timing. however looking at the yellow line on the above dyno graph leads me to beleive that it is infact the dyno laying down incorrect results. you would notice that big of a difference on any car while driving it and perhaps listens to it.

you should recalibrate a dyno. ever car is different and as we all know dyno's are stressed every time they are used. not saying you should calibrate it everytime but checking to see its accurancy can't hurt. we do so on our dynojet, even tho it doesnt need it. it prevents the dyno from misleading anyone and becomes a more respectable and more reliable dyno to use.

john

 

I had the same problem with my 2nd run after an intake install. The owner of the shop said something about running lean as well. I'd really like to figure out what the problem is.

.002 was my baseline dyno, notice a 10 degree temp difference.

 

Also notice how I lost a good amount of power on the runs after the intake install....I'm wondering if it has something to do with those fluctuations.

 

May take more than an intake install to be running too lean. The top few intakes (JWT, Injen, typhoon) for this car consistently make a A/F difference at 5500+ and it's only a small difference (0.2-0.3 higher).

I do know for certain that after my cat install and swapping my AEM for a JWT, the ecu was pulling timing. Lasted about 2 days, and acceleration felt gooey and weak. Felt like I lost massive torque. Did the ECU reset procedure, no difference. 2 days later and after driving around quite a bit, it came back to life on the 3rd day in the morning w/ plenty of extra power.

My belief is that the ECU pulls timing when the A/F is lean, but also pulls timing if theres a sudden change in A/F (regardless of where its at).

 

I did the dyno about 1,000 miles after the intake install, so the ECU should have had time to compensate for anything....Also did the ECU reset procedure.

 

i was told those really jagged lines are timing being pulled by the ecu feedback from the knock sensor... my stock dynos did not have them, but my CAI dynos did (same dyno machine). now with my fuel and timing control, i do not see them again...

m

 

Okay, it is not the clutch. I got on a step hill going up at 30 mph. I dumped it in 6th at 1000rpm and it bogged hard. The clutch did not slip one bit.

I can seriously believe that it is timing being pulled. Look at my second image above (the uncorrected one with 6 runs). There are basically two AF curves. The second set is newer and richer. The ECU must have adjusted some. The higher curve was right after I made some major changes. The lower curve was the result of 1000 miles of driving or more.

One thing to note about detonation and the resulting retard. First, the sound of the engine on the dyno was a little "tin-y". Not nuts in a can, but not smooth. Second, I use Sunoco 94 like a religion. I should be able to run leaner safely when compared to a 91 octane user. Then again, I was pretty lean.

Well, at least the fix may be something I had planned anyhow. The TS ECU is next for me, so that should help.

Thanks y'all

 

Here is mine from today doing a 5th gear pull

 

Yup, that is the neighborhood I am shooting for with my mods. I don't mean total (every dyno is different), but % change. Looking at my unposted recent numbers, I think some ECU tweaking might do it. We'll see.

Very nice by the way.