Open'd exhaust. How much did you gain?
Just curious. By placing a cut out after the downpipe we've consistently removed 3/10 of a second off the 1/4. What have you all progressed from opening your exhaust?
We usually had either a TII or TI setup running mild boost with fair traction.
Anyone have any dyno-proven improvements?
-Bryan
Re: Open'd exhaust. How much did you gain?
You are correct on the 3/10's
I added a cutout to the SRT-4, wen from 13.80 to
13.52.
Re: Open'd exhaust. How much did you gain?
My Son's ( SC 2.5 ) 88 Shadow ES automatic;
We were running an open 2.25" stock downpipe, went to a 2.5" from an 89 Shelby Daytona and picked up 6/10ths and 4 MPH.
The Mitsu has the big swingvalve, it *really* likes a big downpipe.... :thumb:
Re: Open'd exhaust. How much did you gain?
On that note, full 3 inch mandrel system with a Magnaflow, I can't see gaining 3/10's??????????
Re: Open'd exhaust. How much did you gain?
Quote:
Originally Posted by turbovanman
On that note, full 3 inch mandrel system with a Magnaflow, I can't see gaining 3/10's??????????
Of course you still got the restriction of a 3" diameter vs. an open downpipe's amount resistant pressure being only barometric pressure.
There's literally no restriction in an open exhaust, just about how fast the engine is cranking it out.
Re: Open'd exhaust. How much did you gain?
What d'you have for an exhaust manifold and turbo SV?
Re: Open'd exhaust. How much did you gain?
I have a MoparzRule heavily ported exhaust manifold and a stock 2.25" '88 SV.
Re: Open'd exhaust. How much did you gain?
2 1/4" ran a 13.97 @99.98mph Over the winter opened the stock downpipe. Ran 13.27 @ 106.7mph 1st pass. Changed to a Rick D 2.5" ported S/v and open 3" downpipe. Ran 12.85 @ 109.7mph
On the dyno, full 3" system with a cat and a cutout before the cat. Lost 22ft lbs abd 11whp with the cutout closed.
Re: Open'd exhaust. How much did you gain?
Quote:
Originally Posted by GLHSKEN
2 1/4" ran a 13.97 @99.98mph Over the winter opened the stock downpipe. Ran 13.27 @ 106.7mph 1st pass. Changed to a Rick D 2.5" ported S/v and open 3" downpipe. Ran 12.85 @ 109.7mph
On the dyno, full 3" system with a cat and a cutout before the cat. Lost 22ft lbs abd 11whp with the cutout closed.
Wow.:clap2:
Re: Open'd exhaust. How much did you gain?
I am running no exhaust now... just open turbo :D freaking awesome!!!!
Re: Open'd exhaust. How much did you gain?
My R/T gained 20-25 hp over the entire pull with the cutout open. it's at the end of the downpipe 8-10" before the cat.
It's a 3" mandrel bent system and at the time the car had a cat on it. Pushed it from 29x whp to 322whp.
Re: Open'd exhaust. How much did you gain?
Nice gains but full 3 inch and Magnaflow, can't be loosing that much. Will have to try that on the dyno. Any bets?
Re: Open'd exhaust. How much did you gain?
'87 T2 shadow
Open stock downpipe, cut in front of converter = 13.00's
Full non-mandrel-bent (read: crimped corners) 3" after downpipe, no converter thru a 3" Dynomax Race Magnum Oval muffler, exit out the back = 13.00's
Re: Open'd exhaust. How much did you gain?
Quote:
Originally Posted by BadAssPerformance
'87 T2 shadow
Open stock downpipe, cut in front of converter = 13.00's
Full non-mandrel-bent (read: crimped corners) 3" after downpipe, no converter thru a 3" Dynomax Race Magnum Oval muffler, exit out the back = 13.00's
What were your 60's and 660's like on both passes? Can you get me both entire slips? That doesn't seem right at all. Either one's pulling real hard on the bottom or the other real hard on the top. Restriction is restriction. And you still had 9.42" x Y (y being whatever the length of the exhaust) of backpressure versus 0 being open.
Re: Open'd exhaust. How much did you gain?
Quote:
Originally Posted by Dave
What were your 60's and 660's like on both passes? Can you get me both entire slips? That doesn't seem right at all. Either one's pulling real hard on the bottom or the other real hard on the top. Restriction is restriction. And you still had 9.42" x Y (y being whatever the length of the exhaust) of backpressure versus 0 being open.
I think he's saying the backpressure in a full 3" exhaust is comparable to the backpressure from using a stock dp. Or at least that is what I read from it.
Re: Open'd exhaust. How much did you gain?
Quote:
Originally Posted by The S is Silent
I think he's saying the backpressure in a full 3" exhaust is comparable to the backpressure from using a stock dp. Or at least that is what I read from it.
What I got out of his saying is that an open downpipe is equivalent to a 3" mandrel bent exhaust.
Re: Open'd exhaust. How much did you gain?
Quote:
Originally Posted by Dave
What I got out of his saying is that an open downpipe is equivalent to a 3" mandrel bent exhaust.
Stock open DP = 3" NON-mandrel bent system
Re: Open'd exhaust. How much did you gain?
Quote:
Originally Posted by The S is Silent
Stock open DP = 3" NON-mandrel bent system
yep, that is what I said...
Stock open DP = full 3" non mandrel bent with 3" race magnum oval w/o converter
Entire timeslip is similar for both setups even tried with and without the back seat in the car with the full exhaust setup. Launch at 4000-4500, 1.83-1.85 60'... 13.00-13.10 @ 103-105 mph....
Re: Open'd exhaust. How much did you gain?
It sounds like you were still using the stock DP in both setups? Another way to look at it is that the restriction of the stock DP is such that adding the 3" system had no real effect on backpressure.
Re: Open'd exhaust. How much did you gain?
Quote:
Originally Posted by MiniMopar
It sounds like you were still using the stock DP in both setups? Another way to look at it is that the restriction of the stock DP is such that adding the 3" system had no real effect on backpressure.
Yep, stock turbo, SV & DP in both. So after that cork, a 3" flowed as good as the open DP :thumb: