2.75inch or 3inch DOWNPIPE
he is somewhat in the same boat im in, im currently trying to figure out if i should go and get all mandrel bent stainless steel 3 inch piping done. i mean i have 3 inch piping on my car now just its crush bent and not stainless steel. big price to pay for some piping but i will see.
Originally Posted by donmeca2020
he is somewhat in the same boat im in, im currently trying to figure out if i should go and get all mandrel bent stainless steel 3 inch piping done. i mean i have 3 inch piping on my car now just its crush bent and not stainless steel. big price to pay for some piping but i will see.
Evolving Member
Joined: Mar 2005
Posts: 130
Likes: 0
From: The Islands
Originally Posted by CubanEVO
Right now im running a Tanabe downpipe that is 2.75 inches would there be any difference if i changed to a 3 inch
I'm supposed to get a retune for some other mods in another month, so now would probably be the best time to change.
Originally Posted by NDgsx
Back it up with proof then.
Here is my proof, clipped from www.roadraceengineering.com
Espelier Stainless Steel Down Pipe
Espelier Stainless Steel 2.75" down pipe. OMG! It's only 2.75" diameter! ¡Que horríble! Yeah, you will be limited to about 600 hp with "only" a 2.75" down pipe. But hey, it nicely fits all EVOs including MR and '05s and newer cars with active center differentials. We figured that was the important part.
Look at all the JDM downpipes, they were designed with the stock turbo in mind....
not to mention, you'll have better clearance with the lower tie bars with a smaller diameter pipe.
Originally Posted by Blue Evo 8
Here is my proof, clipped from www.roadraceengineering.com
Espelier Stainless Steel Down Pipe
Espelier Stainless Steel 2.75" down pipe. OMG! It's only 2.75" diameter! ¡Que horríble! Yeah, you will be limited to about 600 hp with "only" a 2.75" down pipe. But hey, it nicely fits all EVOs including MR and '05s and newer cars with active center differentials. We figured that was the important part.
Look at all the JDM downpipes, they were designed with the stock turbo in mind....
not to mention, you'll have better clearance with the lower tie bars with a smaller diameter pipe.
Espelier Stainless Steel Down Pipe
Espelier Stainless Steel 2.75" down pipe. OMG! It's only 2.75" diameter! ¡Que horríble! Yeah, you will be limited to about 600 hp with "only" a 2.75" down pipe. But hey, it nicely fits all EVOs including MR and '05s and newer cars with active center differentials. We figured that was the important part.
Look at all the JDM downpipes, they were designed with the stock turbo in mind....
not to mention, you'll have better clearance with the lower tie bars with a smaller diameter pipe.
The following excerpts are from Jay Kavanaugh, a turbosystems engineer at Garrett...
Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure.
Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range.
As for 2.5" vs. 3.0", the "best" turboback exhaust depends on the amount of flow, or horsepower. At 250 hp, 2.5" is fine. Going to 3" at this power level won't get you much, if anything, other than a louder exhaust note. 300 hp and you're definitely suboptimal with 2.5". For 400-450 hp, even 3" is on the small side...
Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure.
Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range.
As for 2.5" vs. 3.0", the "best" turboback exhaust depends on the amount of flow, or horsepower. At 250 hp, 2.5" is fine. Going to 3" at this power level won't get you much, if anything, other than a louder exhaust note. 300 hp and you're definitely suboptimal with 2.5". For 400-450 hp, even 3" is on the small side...
...also, Garrett's motives for stating such should not be in question as they do not sell exhaust systems.
http://www.turbobygarrett.com/
BTW, it might serve many of you guys well to go to their site and read up in their tech sections... really good info.
Last edited by Zeus; Apr 11, 2006 at 10:32 AM.
Originally Posted by Blue Evo 8
On a stock turbo'd evo you'll lose low end tq going to a full 3" DP....
Not exactly, but if you run the stock 2.5' cat, a 3' DP in front of it it's not going to help much.
Originally Posted by Zeus
RoadRace is a grade A shop/team, top end outfit... however, I'd rather take the word of those designing Garret Turbos...
Although this quote comes from a while back... even Buschur posted back to back dyno results on this site refuting that a 2.5" downpipe makes more power than a 3" in an EVO application. I'm not interested in looking for the post, but I believe you will find that was throughout the power band bottom to top.
...also, Garrett's motives for stating such should not be in question as they do not sell exhaust systems.
http://www.turbobygarrett.com/
BTW, it might serve many of you guys well to go to their site and read up in their tech sections... really good info.
Although this quote comes from a while back... even Buschur posted back to back dyno results on this site refuting that a 2.5" downpipe makes more power than a 3" in an EVO application. I'm not interested in looking for the post, but I believe you will find that was throughout the power band bottom to top.
...also, Garrett's motives for stating such should not be in question as they do not sell exhaust systems.
http://www.turbobygarrett.com/
BTW, it might serve many of you guys well to go to their site and read up in their tech sections... really good info.
Evolving Member
Joined: Mar 2005
Posts: 173
Likes: 0
From: Baton Rouge, LA
Originally Posted by Zeus
RoadRace is a grade A shop/team, top end outfit... however, I'd rather take the word of those designing Garret Turbos...
Originally Posted by Jay Kavanaugh @ Garret
Other things you can do (in addition to choosing an appropriate diameter) to minimize exhaust backpressure in a turboback exhaust are: avoid crush-bent tubes (use mandrel bends); avoid tight-radius turns (keep it as straight as possible); avoid step changes in diameter; avoid "cheated" radii (cuts that are non-perpendicular); use a high flow cat; use a straight-thru perforated core muffler... etc
Originally Posted by Blue Evo 8
Here is my proof, clipped from www.roadraceengineering.com
Espelier Stainless Steel Down Pipe
Espelier Stainless Steel 2.75" down pipe. OMG! It's only 2.75" diameter! ¡Que horríble! Yeah, you will be limited to about 600 hp with "only" a 2.75" down pipe. But hey, it nicely fits all EVOs including MR and '05s and newer cars with active center differentials. We figured that was the important part.
Look at all the JDM downpipes, they were designed with the stock turbo in mind....
not to mention, you'll have better clearance with the lower tie bars with a smaller diameter pipe.
Espelier Stainless Steel Down Pipe
Espelier Stainless Steel 2.75" down pipe. OMG! It's only 2.75" diameter! ¡Que horríble! Yeah, you will be limited to about 600 hp with "only" a 2.75" down pipe. But hey, it nicely fits all EVOs including MR and '05s and newer cars with active center differentials. We figured that was the important part.
Look at all the JDM downpipes, they were designed with the stock turbo in mind....
not to mention, you'll have better clearance with the lower tie bars with a smaller diameter pipe.
On a stock turbo'd evo you'll lose low end tq going to a full 3" DP....
Eh, you'll lose power in the low end range, but you'll get better overall top end power. You wouldn't lose power, thats just dumb. Even from what RRE said, they still aren't stating that you'll lose power when going with a larger diameter pipe.
He's got a point technically, you do lose power, just in certain ranges RPM but you compensate with better overall top end power.
He's got a point technically, you do lose power, just in certain ranges RPM but you compensate with better overall top end power.
Evolving Member
Joined: Jan 2005
Posts: 294
Likes: 0
From: Kent, WA
Originally Posted by Blue Evo 8
Here is my proof, clipped from www.roadraceengineering.com
Espelier Stainless Steel Down Pipe
Espelier Stainless Steel 2.75" down pipe. OMG! It's only 2.75" diameter! ¡Que horríble! Yeah, you will be limited to about 600 hp with "only" a 2.75" down pipe. But hey, it nicely fits all EVOs including MR and '05s and newer cars with active center differentials. We figured that was the important part.
Look at all the JDM downpipes, they were designed with the stock turbo in mind....
not to mention, you'll have better clearance with the lower tie bars with a smaller diameter pipe.
Espelier Stainless Steel Down Pipe
Espelier Stainless Steel 2.75" down pipe. OMG! It's only 2.75" diameter! ¡Que horríble! Yeah, you will be limited to about 600 hp with "only" a 2.75" down pipe. But hey, it nicely fits all EVOs including MR and '05s and newer cars with active center differentials. We figured that was the important part.
Look at all the JDM downpipes, they were designed with the stock turbo in mind....
not to mention, you'll have better clearance with the lower tie bars with a smaller diameter pipe.
You said that a 3" exhaust will REDUCE low end torque, which is 100% not true.
Believe what you want guys... Garrett and Buschur agree in engineering and actual live data that bigger is better when it comes to turbo charged applications. There are graphs, Turbo engineers opinions, what else must people need. Yes, you perceive less low end torque due to the "high end rush", but that is exactly what it is... a perception.
What more could you need?
What more could you need?
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