So, here's a dumb question about exhaust cutouts, and losing HP.
06-26-2007, 06:12 PM
#1
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So, here's a dumb question about exhaust cutouts, and losing HP.
Has anyone dynoed their car before, then after with the dumps closed to see if they LOST HP?
Example:
With a normal straight through 'clean' exhaust, HP - 300
With dumps installed and closed, 'dirtying' the exhaust flow, hp - 290.
With dumps installed and open, hp - 315.
Just a thought I had as a possibility...
Example:
With a normal straight through 'clean' exhaust, HP - 300
With dumps installed and closed, 'dirtying' the exhaust flow, hp - 290.
With dumps installed and open, hp - 315.
Just a thought I had as a possibility...
06-26-2007, 06:23 PM
#3
AudiWorld Expert
possible, though likey more difference between various exhausts/mufflers/etc out there
Essentially with them closed, it's creating an SRT style exhaust. It actually worked out well for me as there was a "tinny" sound that I had at certain RPMs, and it was completely removed once I had my dumps installed.
<img src="http://ctny.audiworld.com/mark/s4/downpipes/dumps/dsc06156.jpg">
SRT:
<img src="http://pictureposter.audiworld.com/29837/backfrt.jpg">
<img src="http://ctny.audiworld.com/mark/s4/downpipes/dumps/dsc06156.jpg">
SRT:
<img src="http://pictureposter.audiworld.com/29837/backfrt.jpg">
06-26-2007, 06:31 PM
#5
AudiWorld Expert
Ok, so it seems I may have some useful data....
I dyno'd on the same dyno on 1/24/04 and 9/25/04, once before dumps were installed and once after. Both times I ran the same program (APR 104oct Race v1.2). I can't state what gas I used, nor if I fully removed the 93 or not.
While the reported #s differ, the corrected crank numbers are near identical, based on what a stock B5 S4 made on the respective days.
I'm not stating this as great data, but it's all I have to offer, so take it for what it's worth...
373wHP/403wTQ [449HP/485TQ] (1/24/04)
340wHP/376wTQ [447HP/494TQ] (9/25/04)<ul><li><a href="http://ctny.audiworld.com/mark/s4/dyno/">http://ctny.audiworld.com/mark/s4/dyno/</a</li></ul>
While the reported #s differ, the corrected crank numbers are near identical, based on what a stock B5 S4 made on the respective days.
I'm not stating this as great data, but it's all I have to offer, so take it for what it's worth...
373wHP/403wTQ [449HP/485TQ] (1/24/04)
340wHP/376wTQ [447HP/494TQ] (9/25/04)<ul><li><a href="http://ctny.audiworld.com/mark/s4/dyno/">http://ctny.audiworld.com/mark/s4/dyno/</a</li></ul>
06-26-2007, 07:07 PM
#6
with the style of dumps that merge off it is entierly possible that they could create
a pocket that back flows and causes turbulence. also could create wall resitance. i doubt its much tho
06-26-2007, 07:48 PM
#7
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Very doubtful. Matt Taesch did back to back dyno pulls during the AWE dyno day
and with K03s, his open DP numbers and closed DP numbers were virtually identical. If your "dirtying the exhaust" theory were true, he would have lost power while running through the full exhaust. But the fact that he actually ran exactly the same number as he did with the cutouts open leads me to believe that what you're proposing is not true.
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06-27-2007, 11:29 AM
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I've ran the same 1/4 times before the dumps were installed Vs. after they were installed
Also opening them up usually netting me 0 results at the 1/4 mile. Not sure, it could be setup, as i have the original APR downpipes without the flex joint. I beleive that the vibration from opening up the dumps is causing the car to pull timing. I later verified this by logging timing with the dumps open and closed. I saw a 5-8 degrees of time pulled through the rpm band.