Dundon GT4/Spyder Race Header Group Buy
#17
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Going to switch membership over to Kidney4sale.com?
Jamie -
Interesting information. Was this run with a NEW tune for this TB/Plenum situation, or your standard "header" tune?
Do you feel that this is likely because the added possible flow benefits of TB/Plenum (which would probably be upper RPM range) are still bottlenecked by the OEM exhaust? Or is there something else at play?
I'm curious, because really wish to know how limiting the OEM cat-back exhaust has for upper RPM gains... it would nice to be able to keep it if the bottleneck was minimal, but as parts were added.
Plenum/TB:
We ran a popular plenum and 82mm TB on our headers and our tune and found no measurable improvements even at high rpm. This is good news to some as it means the power improvements are easily achieved with just headers and a tune or even headers alone. We do believe there is more power available through work on the intake/plenum and we will be pursuing this as a Stage 3 package.
Interesting information. Was this run with a NEW tune for this TB/Plenum situation, or your standard "header" tune?
Do you feel that this is likely because the added possible flow benefits of TB/Plenum (which would probably be upper RPM range) are still bottlenecked by the OEM exhaust? Or is there something else at play?
I'm curious, because really wish to know how limiting the OEM cat-back exhaust has for upper RPM gains... it would nice to be able to keep it if the bottleneck was minimal, but as parts were added.
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#18
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This is the wonderful benefit of using the Porsche Sport Exhaust, no drone at all, sounds great at low rpm cruise, can talk in the car without issue!
We bolted the TB/Plenum on with our headers and our developed tune. We logged the car and didn't see a noticeable gain. We flashed the car to stock and same story. We also logged manifold pressure, which surprisingly on the GT4 is sub ambient at WOT, this typically indicates a restriction as not all the air the car is asking for is filling up the manifold. The MAP was the same for both the setups. We're not sure why this is, but we know that the race headers are pulling quite a bit out of the cylinders in order to get 43whp at 7500 rpm. We believe this is all resonance wave governed, and it's possible that our race system is too strong an influence to see a difference with the TB/Plenum mods. we will continue to do more research and testing on this, but wanted to get the system out ASAP. The Good news is we're making a lot of power for just bolt on headers and a tune, so less parts to buy and less money to spend on installation. We have a few variants of plenum coming (all Porsche factory parts). And also will be 3d scanning the entire intake system as we would love to see the MAP a bit close to ambient (there is a ram air effect with these cars as well, but more on that later...).
We've run the car with a complete straight pipe exhaust during our testing and there was a bit of a benefit at high rpm. We will be offering this along with the street catted system once complete!
Interesting information. Was this run with a NEW tune for this TB/Plenum situation, or your standard "header" tune?
Do you feel that this is likely because the added possible flow benefits of TB/Plenum (which would probably be upper RPM range) are still bottlenecked by the OEM exhaust? Or is there something else at play?
I'm curious, because really wish to know how limiting the OEM cat-back exhaust has for upper RPM gains... it would nice to be able to keep it if the bottleneck was minimal, but as parts were added.
![Cheers](https://rennlist.com/forums/images/smilies/beerchug.gif)
Do you feel that this is likely because the added possible flow benefits of TB/Plenum (which would probably be upper RPM range) are still bottlenecked by the OEM exhaust? Or is there something else at play?
I'm curious, because really wish to know how limiting the OEM cat-back exhaust has for upper RPM gains... it would nice to be able to keep it if the bottleneck was minimal, but as parts were added.
![Cheers](https://rennlist.com/forums/images/smilies/beerchug.gif)
We've run the car with a complete straight pipe exhaust during our testing and there was a bit of a benefit at high rpm. We will be offering this along with the street catted system once complete!
__________________
Dundon Motorsports
Gig Harbor, WA
253-200-4454
jamie@dundonmotorsports.com
www.dundonmotorsports.com
Facebook.com/dundonmotorsports
Instagram @dundon_motorsports
Dundon Motorsports
Gig Harbor, WA
253-200-4454
jamie@dundonmotorsports.com
www.dundonmotorsports.com
Facebook.com/dundonmotorsports
Instagram @dundon_motorsports
Last edited by Jamie@dundonmotorsports; 08-18-2016 at 05:20 PM.
#20
Burning Brakes
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This is with nothing but headers and a tune?
#22
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Also in line with my thoughts. This vehicle has some interesting resonance effects, especially if a straight pipe exhaust is doing little. We all know Porsche does a lot of resonance wave testing AND design implementations. At least you have the 991 Carrera S X51 vehicle to give you some clues, likely a path you're headed down.
The ram air might help a little, but your negative manifold pressures gives some clues as well regarding the entire airflow environment, intake to exhaust. I would doubt the manifold stays negative at speed due to airflow... but who knows.
Great info.
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#29
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I didn't calculate each RPM from the BGB thread graph, and I assume tune cost is the same, but is the roughly 10whp difference at 6500 RPM worth ~$1,720?
It is to me.
Made in the US, 321SS, and possibly improvements to the tune for plenum and TB to come.
Dundon race headers $3,750 and free shipping group buy, tune;
3600 RPM: +50 wtq +32whp
5000 RPM: +55 wtq, +52whp
5800 RPM: +24 wtq, +26whp
6500 RPM: +30 wtq, +36whp
7500 RPM: +30 wtq, +43whp
Cargraphic race headers $1,980 plus half off shipping ($50?) group buy, tune, filters, plenum, TB;
342 - 316 = 26whp @ 6500
https://rennlist.com/forums/gt4/8822...l#post12683867
It is to me.
Made in the US, 321SS, and possibly improvements to the tune for plenum and TB to come.
Dundon race headers $3,750 and free shipping group buy, tune;
3600 RPM: +50 wtq +32whp
5000 RPM: +55 wtq, +52whp
5800 RPM: +24 wtq, +26whp
6500 RPM: +30 wtq, +36whp
7500 RPM: +30 wtq, +43whp
Cargraphic race headers $1,980 plus half off shipping ($50?) group buy, tune, filters, plenum, TB;
342 - 316 = 26whp @ 6500
https://rennlist.com/forums/gt4/8822...l#post12683867
Last edited by d00d; 12-25-2019 at 06:40 PM.
#30
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Also in line with my thoughts. This vehicle has some interesting resonance effects, especially if a straight pipe exhaust is doing little. We all know Porsche does a lot of resonance wave testing AND design implementations. At least you have the 991 Carrera S X51 vehicle to give you some clues, likely a path you're headed down.
The ram air might help a little, but your negative manifold pressures gives some clues as well regarding the entire airflow environment, intake to exhaust. I would doubt the manifold stays negative at speed due to airflow... but who knows.
Great info.
The ram air might help a little, but your negative manifold pressures gives some clues as well regarding the entire airflow environment, intake to exhaust. I would doubt the manifold stays negative at speed due to airflow... but who knows.
Great info.