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I'll scan and post a copy of my dyno sometime this weekend hopefully. Overall, the dyno session went very well, but it was not without its problems.
The belt started slipping above ~6000 rpms. The plot shows almost linear acceleration, and then a sudden dip in the hp and torque graphs. Standing in front of the car and observing the B&M fuel pressure gauge confirmed this. When the belt started slipping, the fuel pressure also bounced around.
Even with the slipping belt, max hp was around 215 with 162 ft-lbs torque. A/F ratio was measured using an HKS wideband unit, and unfortunately, the results could not be graphed. We saw roughly 12.5:1 over the entire rpm when plugging the sensor in AFTER the catalytic converter (which should show a little leaner than before the cat).
I made a decision to end the tuning session early, as I figured I'd have to tighten the belt to see my max hp numbers. I'll be going back in a week or so to "finish" the tuning session.
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215/162 with a slipping belt isn't too shabby... [img]smile.gif[/img]
Post the final chart when you have a chance, and what are you using to tune fuel?
Chuck
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i just tightened my alternator to supercharger belt. . .I didn't realize there'd be that much slack in it! So now I'm hopeful for higher dyno numbers.
I use a VAFC to tune fuel.
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Do you know what your boost was reading from the belt slip? Assuming your belt was slipping, I bet you'll end up in the 230 +/- a few range given your initial results.
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Yeah. I watched the boost gauge on one of the runs. . . it peaked around 11 psi, but then dropped to about 6 and then wavered between 6 and 7 psi.
After tightening the belt, it peaked at about 11 psi and then settled between 9 and 10 psi. Problem was, when I was sitting on the dyno, I couldn't access the lock nut for the alternator to supercharger tensioner.
I'll be going back in on Monday for 2 or 3 power runs. I doubt I'll be able to use the wideband again, since they'll probably want to charge me another $50 to use it.
<font color="#a62a2a" size="1">[ June 13, 2003 01:13 PM: Message edited by: 217gsr ]</font>
<font color="#a62a2a" size="1">[ June 13, 2003 01:28 PM: Message edited by: 217gsr ]</font>
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do you know what the intake temps were @ on your highest boost levels??
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217gsr
Do you think you had the slipping belt when you ran thar Neon SRT-4? This could have made the difference.....
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Actually, yeah. . .that's pretty likely too. I went back into my maintenance records. The last time I adjusted my alternator belt was when I replaced my alternator, in mid February. [img]eek.gif[/img]
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I just got back from my dyno re-run. Now remember, the only adjustment that I made was tightening up my alternator to supercharger belt.
The car made 226.1 / 177.0 peak over last time's 224.1 / 169.0 peak.
But the biggest difference is in the range around 6000-7000 rpm, where the hp jumped between 15-20 hp and the torque jumped 10-15 ft-lbs of torque.
I still think there's a little bit more belt slippage, but instead of being around 6500 rpm, I think it's around 7000-7500 rpm now. Tightening the belt up a little bit more might help out the power. I probably won't do that, but instead change out the belt entirely in a little bit.
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What brand belt are you using? Might want to go the next smallest size perhaps.
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I forget which brand I'm using. The belt looks a little different from the ones that I used to use. It has horizontal ribs as well as vertical ribs. The decreased contact area may be a reason why there is slip.
The tensioner still has some ways to go, so I probably won't need a smaller belt size. I'll probably buy a different brand next time though.
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No, my dip is not nearly that extreme. My graph just seems to level off as you approach redline.
I've scanned my dyno plots. There are 3 of them. Can anyone host them or tell me how to post them? Thanks.
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hey i was just wondering if you sudden dip on your dyno was something like this???
Cause i am having a problem, the dip happens consistantly at 6500rpm.
http://www.imagestation.com/picture/...5/fd348287.jpg
defcon
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Come on guys . . . no one will host my dyno pics?
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E-mail me your pictures.
Chuck
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Excellent. Thanks 96IntegraRS. I'll have my girlfriend email them to you today. I'll follow your post up with an explanation of the plots.
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Thanks again 96IntegraRS!!
Run #17 - 1st run on dyno day 1
Run #33 - last run on dyno day 1
Run #34 - 1st run on dyno day 2 (only tightened belt)
Run #39 - last run on dyno day 2
Does anyone else think that in run #39 my belt is still slipping above ~7000 rpm?
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Two things pop into my head when I compare these two dyno runs (#34, #39)...
1) Engine coolant temperature: It appears that the earlier pass may have been done with the coolant temp below 172'... which will richen up the fuel tables a bit.
2) Gear selection: Looking at the RPM/MPH values, it appears that run #39 was done one gear lower than #34. This may make a bit of a difference.
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Hmm. . . thanks Jim. I never noticed that run 39's values for rpm/mph were different than the others. I know that the tuner knew to run it in 4th in every run. . . maybe it was just a brain fart. If it was run in 3rd, does that tend to show higher or lower values?
Run #34 was done right when I got to the dyno, after driving about 15 minutes on the freeway. The car only rested for about 10 minutes while we strapped the car to the dyno.
