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4" true downpipe

mk6'12gti

Drag Racing Champion
Location
Cleveland
That just sounds like Trackslag but with extra steps...
How so? Trackslags dp tapers down to 3" right before the flex pipe. Mine with be 4" after the flex then taper to 3" with the reducer to bolt to the exhaust. Trackslags is extra steps vs this one imo
 

JerseyDrew77

Autocross Champion
Location
Virginia & NC
Car(s)
2016 TR GTI S 6MT
How so? Trackslags dp tapers down to 3" right before the flex pipe. Mine with be 4" after the flex then taper to 3" with the reducer to bolt to the exhaust. Trackslags is extra steps vs this one imo
No. Trackslag is 4 inches for the 180* down to 3.5 inches to the flex joint and 3 inches after the flex joint. It's a very nice gradual decrease versus going from 4 immediately down to 3 with not much of a taper.
 

daconchslop

Autocross Champion
Location
South Carolina
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mk6'12gti

Drag Racing Champion
Location
Cleveland
No. Trackslag is 4 inches for the 180* down to 3.5 inches to the flex joint and 3 inches after the flex joint. It's a very nice gradual decrease versus going from 4 immediately down to 3 with not much of a taper.
Meh oh well still dont matter prefer mine thats being made.
 

git_fan

Go Kart Champion
Location
Virginia
Car(s)
2016 GTI
No. Trackslag is 4 inches for the 180* down to 3.5 inches to the flex joint and 3 inches after the flex joint. It's a very nice gradual decrease versus going from 4 immediately down to 3 with not much of a taper.
He hasn't even made the DP yet, how do you know how much of a taper it will have?
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
No. Trackslag is 4 inches for the 180* down to 3.5 inches to the flex joint and 3 inches after the flex joint. It's a very nice gradual decrease versus going from 4 immediately down to 3 with not much of a taper.
I would be more concerned with backpressure suddenly going from 4" to 3".
 

git_fan

Go Kart Champion
Location
Virginia
Car(s)
2016 GTI
He specifically said that the whole DP will be 4 inches with a reducer to mate to his APR exhaust, which doesn't leave very much room. The one thing that comes to my mind is like what Jim said, backpressure.

I would be more concerned with backpressure suddenly going from 4" to 3".
What is the length of the reducer? The transition has been described as "immediate" and "sudden". So it's going from 4" down to 3", but how many inches of exhaust length is it taking to go from one to the other?
 

Desslok

Autocross Champion
Location
PA
Car(s)
2019 Rabbit
Doesn't the Trackslag bolt to the stock catback?
If the claims that catbacks offer zero HP gains are actually true, going from 4" to 3" will be far less of a problem than 4" to 2.5".
 

zucchinies

Go Kart Newbie
Location
San Diego
Car(s)
2020 A3
Doesn't the Trackslag bolt to the stock catback?
If the claims that catbacks offer zero HP gains are actually true, going from 4" to 3" will be far less of a problem than 4" to 2.5".
I always wondered this. People say there are no discernable difference but in terms of flow, your restriction will always be the smallest diameter pipe. Think of a Hourglass. No matter how big and wide you get your hourglass at the top, the sand's flow will be restricted to the small hole.
 

El_bigote_AJ

Autocross Champion
Location
Las Vegas
Car(s)
2019 GTI bunny
I always wondered this. People say there are no discernable difference but in terms of flow, your restriction will always be the smallest diameter pipe. Think of a Hourglass. No matter how big and wide you get your hourglass at the top, the sand's flow will be restricted to the small hole.
This is only looking at it from a flow aspect… trackslags DP effectiveness (with real world results to back that up) don’t just have to do with this perceived volume of flow from being bigger. the results (spool/power) you are gaining are due to the reduced egts and the scavenging effect that are results of the large internal section directly off the turbo as well and the gradual reductions in size.



To the point of concerns with it going from 4-3 under the car… I think the effect would be negligible as noted above since the temps will already be greatly reduced by that time.
 

zucchinies

Go Kart Newbie
Location
San Diego
Car(s)
2020 A3
This is only looking at it from a flow aspect… trackslags DP effectiveness (with real world results to back that up) don’t just have to do with this perceived volume of flow from being bigger. the results (spool/power) you are gaining are due to the reduced egts and the scavenging effect that are results of the large internal section directly off the turbo as well and the gradual reductions in size.



To the point of concerns with it going from 4-3 under the car… I think the effect would be negligible as noted above since the temps will already be greatly reduced by that time.
That makes sense. Thank you for the explanation.
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
What is the length of the reducer? The transition has been described as "immediate" and "sudden". So it's going from 4" down to 3", but how many inches of exhaust length is it taking to go from one to the other?
You would have to ask the OP who is building it.
 
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