Confusing dyno sheet
Thread Starter
Race Director
Joined: Sep 2007
Posts: 16,557
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From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
Confusing dyno sheet
I had an opportunity last week to get in on a group dyno day. The car is an '08 A6 with LG street catless headers, Vararam, ported IM, Z06 mufflers, tune, 2.56 rear, and Yank 4000.
This pull was in 4th gear and went WOT at 2564 RPM according to my HPT scan. I hit 3 degrees of KR at 4479, again at 5332, and then 1.6 at 6174 increasing to 2.6 at 6464, before finishing at 6784.
The chart is showing 394.63 peak power at 5849, which my scan still shows 1.1 residual from the 2nd KR event. Peak TQ per chart was 389.29 at 4716, while the scan was peaking at 3.3 KR. The DA was 2700'.
Now the HP and TQ curves crossed at 5410, instead of 5252, so that just makes me wonder what is really happening here.
I have changed nothing since my last trip to the drags, where I ran 10.92 @ 125.26 in 2100' DA with minor (less than 1) KR only at 5700 in 3rd gear.
My main reason for the dyno was to see where my A/F was at WOT. It looks a taste lean from 4000 to 4800 and a smidgen rich from 5600 up.
I'm planning an early Sunday morning scan at my favorite TnT location, just to confirm my tune and check the KR.
So does anyone have any thoughts that this dyno sheet might seem a little strange? Or should I blow it off and just rely on timeslips?
This pull was in 4th gear and went WOT at 2564 RPM according to my HPT scan. I hit 3 degrees of KR at 4479, again at 5332, and then 1.6 at 6174 increasing to 2.6 at 6464, before finishing at 6784.
The chart is showing 394.63 peak power at 5849, which my scan still shows 1.1 residual from the 2nd KR event. Peak TQ per chart was 389.29 at 4716, while the scan was peaking at 3.3 KR. The DA was 2700'.
Now the HP and TQ curves crossed at 5410, instead of 5252, so that just makes me wonder what is really happening here.
I have changed nothing since my last trip to the drags, where I ran 10.92 @ 125.26 in 2100' DA with minor (less than 1) KR only at 5700 in 3rd gear.
My main reason for the dyno was to see where my A/F was at WOT. It looks a taste lean from 4000 to 4800 and a smidgen rich from 5600 up.
I'm planning an early Sunday morning scan at my favorite TnT location, just to confirm my tune and check the KR.
So does anyone have any thoughts that this dyno sheet might seem a little strange? Or should I blow it off and just rely on timeslips?
Last edited by HOXXOH; Dec 6, 2014 at 01:46 AM.
Le Mans Master
Joined: Apr 2013
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Hell, if you're running 10s with less than 400whp, I would say that you can ignore the dyno sheet.
It may be that you're seeing more KR on the dyno since you're loading it in 4th, whereas you only use 3rd for a 1/4 mile run?
In any event, as you rightly point out, it is mathematically impossible for the torque curve and the hp curve to NOT intersect at 5252 RPM, so something is definitely wrong with that dyno run.
It may be that you're seeing more KR on the dyno since you're loading it in 4th, whereas you only use 3rd for a 1/4 mile run?
In any event, as you rightly point out, it is mathematically impossible for the torque curve and the hp curve to NOT intersect at 5252 RPM, so something is definitely wrong with that dyno run.
Race Director
Joined: Mar 2005
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From: Southampton NJ
Tom I had something similar, so I ran to almost empty and then put sunoco 105 octane fuel in like 10 gallons ran it for a day and rechecked same knock, so figured false kr and turned the levels down
Thread Starter
Race Director
Joined: Sep 2007
Posts: 16,557
Likes: 2,108
From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
Hell, if you're running 10s with less than 400whp, I would say that you can ignore the dyno sheet.
It may be that you're seeing more KR on the dyno since you're loading it in 4th, whereas you only use 3rd for a 1/4 mile run?
In any event, as you rightly point out, it is mathematically impossible for the torque curve and the hp curve to NOT intersect at 5252 RPM, so something is definitely wrong with that dyno run.
It may be that you're seeing more KR on the dyno since you're loading it in 4th, whereas you only use 3rd for a 1/4 mile run?
In any event, as you rightly point out, it is mathematically impossible for the torque curve and the hp curve to NOT intersect at 5252 RPM, so something is definitely wrong with that dyno run.
This is not a paper dyno sheet. The dyno operator sends the results by email and a link to the program that allows various options for viewing. I found the key to the feature that adjusts the scaling and now the curves intersect correctly at 5252.
