Best downpipe on a IX??? Fitment/quality/craftsmanship/performance
There's no real reason not to go with a 3.0" downpipe. The most efficient turbo outlet is the outlet that expands in diameter relative to the velocity / cooling of the exhaust gas. Since only companies like Lockheed Martin or Boeing have the ability to model/test this gas expansion / velocity and because of the limitations of the car it's real hard to design a downpipe that follows this expansion rate. That's why on some race cars the "turbo outlet" simply looks like a horn.
The only benefit of running a 2.75" downpipe is the decrease in friction on the pipe wall because exhaust gases initially travel along the pipe wall first. While this makes a good argument against twin pipe exhausts, from 2.75" -> 3.0" the difference is very minimal (just calculate the circumference difference). And because the average 272 cammed evo pushes far more exhaust gas volume at high RPMs and fills the entire pipe it makes sense to run a 3.0" diameter downpipe. Guys, THERE IS A ~20% DIFFERENCE IN FLOW AREA between a 2.75" and a 3.0" downpipe (just do the math!)
The reality that some manufacturers push a 70mm downpipe for the EVO is two fold:
1. Many manufacturers just don't have the ***** or the high precision CNC mandrel equipment to go 76mm. As you all know 76mm means VERY TIGHT clearances on the EVO. Sometimes a slight tolerance issue during the bending or welding process means downpipe rubbing. Most manufacturers with older equipment are not willing to take the risk.
2. 70mm tube is cheaper and easier to get than 76mm tube. 76mm tube is obviously based on the Imperial request for 3" piping. Most foundries in Asia will only manufacture this tube (seamless, drawn) on a special order basis and in large quantities.
As a general rule of thumb, on a turbo car, bigger is better on the exhaust side. You don't want an exhaust system that tapers to 70mm and you don't want a downpipe that reduces to 70mm. Unless of course you're pretty much stock and making about 220whp where you won't be needing that extra 76mm capacity. That's power being left on the table.
We have Helix (76mm) and RSR (80mm) downpipes good in stock.
Cheers,
Gary
Gruppe-S
The only benefit of running a 2.75" downpipe is the decrease in friction on the pipe wall because exhaust gases initially travel along the pipe wall first. While this makes a good argument against twin pipe exhausts, from 2.75" -> 3.0" the difference is very minimal (just calculate the circumference difference). And because the average 272 cammed evo pushes far more exhaust gas volume at high RPMs and fills the entire pipe it makes sense to run a 3.0" diameter downpipe. Guys, THERE IS A ~20% DIFFERENCE IN FLOW AREA between a 2.75" and a 3.0" downpipe (just do the math!)
The reality that some manufacturers push a 70mm downpipe for the EVO is two fold:
1. Many manufacturers just don't have the ***** or the high precision CNC mandrel equipment to go 76mm. As you all know 76mm means VERY TIGHT clearances on the EVO. Sometimes a slight tolerance issue during the bending or welding process means downpipe rubbing. Most manufacturers with older equipment are not willing to take the risk.
2. 70mm tube is cheaper and easier to get than 76mm tube. 76mm tube is obviously based on the Imperial request for 3" piping. Most foundries in Asia will only manufacture this tube (seamless, drawn) on a special order basis and in large quantities.
As a general rule of thumb, on a turbo car, bigger is better on the exhaust side. You don't want an exhaust system that tapers to 70mm and you don't want a downpipe that reduces to 70mm. Unless of course you're pretty much stock and making about 220whp where you won't be needing that extra 76mm capacity. That's power being left on the table.
We have Helix (76mm) and RSR (80mm) downpipes good in stock.
Cheers,
Gary
Gruppe-S
From my personal experience with 2 Evo 8 and 1 Evo 9, I would say going from a 76mm to 70mm makes no different if you are on stock turbo. I have yet seen any concrete data showing a 3" dp making significantly more power than a 2.75. My Evo9 makes 290whp and 306tq on CA **** water on a Mustang. I have a tanabe 2.75dp and a very restrictive Apexi Noir which neck down to about 2.5" in the resignator. My tuner tells me most of the car he tune with 3" and 2.75" makes the same top end power but less tq with the bigger pipe. Just my 2 cents!
Last time I check, I thought Helix redesigned to a 70mm dp because the 3" rub on the subframe or oil pan.
Last time I check, I thought Helix redesigned to a 70mm dp because the 3" rub on the subframe or oil pan.
Last edited by tlclee; Oct 20, 2006 at 01:22 PM.
Do you have any empircal evidence that the 3" dp works better than a 2.75" on 91 octane pump gas with an EVO 9?
There is a very good reason not to run a 3" dp, and that is fitment. Fitment when it comes to these cars is not just a fit and finish cosmetic issue, a close tight fitting 3" dp is more likely to cause issues of false knock if it contacts the drivetrain. This false knock is a huge issue and prevents cars from seeing their full potential.
Even when manufacturers can control tight tolerances, their 3" dp often only clears drivetrain components within millimeters. When manufactures attempt to clear the lower tie bars without spacers this issue is especially true. By using spacers, this is less of a problem as this allows the downpipe to sit lower.
Also, just because a dp isn't rattling at idle or under light cruise doesnt mean it isn't upsetting the knock sensor at WOT. At WOT the engine and exhaust are a lot louder and that contact may not be audible to the driver.
As far as I am concerned, all that math and all those text books thermodynamics theories make for great marketing. But at the end of the sale, on the dyno where we test what works and what doesn't, all that marketing doesn't do any good if the results don't match the theory.
In real science, theories are developed to decribe observed phenomenon in the real world. If that theory doesn't match reality, the theory is changed. Only sales people think they can argue away the facts.
*edit*
As clarification, if you intend on running C-16 and want to do 1/4 mile drag racing, yes go run the 3" dp. At that hp level I am certain the 3" will see benefits.
However, in my area I have yet to meet many people who have these goals, most people are into open track road course driving or autox, where transient response and low end torque are very important.
There is a very good reason not to run a 3" dp, and that is fitment. Fitment when it comes to these cars is not just a fit and finish cosmetic issue, a close tight fitting 3" dp is more likely to cause issues of false knock if it contacts the drivetrain. This false knock is a huge issue and prevents cars from seeing their full potential.
Even when manufacturers can control tight tolerances, their 3" dp often only clears drivetrain components within millimeters. When manufactures attempt to clear the lower tie bars without spacers this issue is especially true. By using spacers, this is less of a problem as this allows the downpipe to sit lower.
Also, just because a dp isn't rattling at idle or under light cruise doesnt mean it isn't upsetting the knock sensor at WOT. At WOT the engine and exhaust are a lot louder and that contact may not be audible to the driver.
As far as I am concerned, all that math and all those text books thermodynamics theories make for great marketing. But at the end of the sale, on the dyno where we test what works and what doesn't, all that marketing doesn't do any good if the results don't match the theory.
In real science, theories are developed to decribe observed phenomenon in the real world. If that theory doesn't match reality, the theory is changed. Only sales people think they can argue away the facts.
*edit*
As clarification, if you intend on running C-16 and want to do 1/4 mile drag racing, yes go run the 3" dp. At that hp level I am certain the 3" will see benefits.
However, in my area I have yet to meet many people who have these goals, most people are into open track road course driving or autox, where transient response and low end torque are very important.
Last edited by EFIxMR; Oct 20, 2006 at 01:52 PM.
Originally Posted by EFIxMR
Do you have any empircal evidence that the 3" dp works better than a 2.75" on 91 octane pump gas with an EVO 9?
There is a very good reason not to run a 3" dp, and that is fitment. Fitment when it comes to these cars is not just a fit and finish cosmetic issue, a close tight fitting 3" dp is more likely to cause issues of false knock if it contacts the drivetrain. This false knock is a huge issue and prevents cars from seeing their full potential.
Even when manufacturers can control tight tolerances, their 3" dp often only clears drivetrain components within millimeters. When manufactures attempt to clear the lower tie bars without spacers this issue is especially true. By using spacers, this is less of a problem as this allows the downpipe to sit lower.
Also, just because a dp isn't rattling at idle or under light cruise doesnt mean it isn't upsetting the knock sensor at WOT. At WOT the engine and exhaust are a lot louder and that contact may not be audible to the driver.
As far as I am concerned, all that math and all those text books thermodynamics theories make for great marketing. But at the end of the sale, on the dyno where we test what works and what doesn't, all that marketing doesn't do any good if the results don't match the theory.
In real science, theories are developed to decribe observed phenomenon in the real world. If that theory doesn't match reality, the theory is changed. Only sales people think they can argue away the facts.
There is a very good reason not to run a 3" dp, and that is fitment. Fitment when it comes to these cars is not just a fit and finish cosmetic issue, a close tight fitting 3" dp is more likely to cause issues of false knock if it contacts the drivetrain. This false knock is a huge issue and prevents cars from seeing their full potential.
Even when manufacturers can control tight tolerances, their 3" dp often only clears drivetrain components within millimeters. When manufactures attempt to clear the lower tie bars without spacers this issue is especially true. By using spacers, this is less of a problem as this allows the downpipe to sit lower.
Also, just because a dp isn't rattling at idle or under light cruise doesnt mean it isn't upsetting the knock sensor at WOT. At WOT the engine and exhaust are a lot louder and that contact may not be audible to the driver.
As far as I am concerned, all that math and all those text books thermodynamics theories make for great marketing. But at the end of the sale, on the dyno where we test what works and what doesn't, all that marketing doesn't do any good if the results don't match the theory.
In real science, theories are developed to decribe observed phenomenon in the real world. If that theory doesn't match reality, the theory is changed. Only sales people think they can argue away the facts.
True, a poorly made downpipe can cause knock will cause problems. But the Helix V2 and RSR downpipes don't have any fitment issues because of tighter tolerances. And there is no knock activity at WOT.
As for science, gas thermodynamics is not a new field of science, it has been around for decades. And yes, we do have a Mustang 4WD dyno to run tests on. And yes it may be down right now, but our new Mustangdyne 500SE will be shipping in two weeks.
The reason that the Apexi Noir in combination with the Tanabe 70mm downpipe makes sense is because with an exhaust that tapers to 70mm or less, you are better off running a smaller diameter upstream as this will increase exhaust gas flow and reduce turbulence when the bottle neck is reached downstream. So you are correct in that with a restrictive exhaust system (one that tapers to 70mm) a 76mm downpipe is not necessary - but with most systems that do not taper, such as the HKS, Apexi GT, Helix, etc. you're in much better shape running a 76mm downpipe.
The Helix V1 downpipe was redesigned to avoid clearance issues on the ACD cars. It is a full 76mm downpipe. Let me grab some pics.
Cheers,
Gary
Gruppe-S
Originally Posted by EFIxMR
I'm running a Perrin 3" acd compatible dp in my EVO9, however, from my experience the tanabe 2.75" is a better downpipe than a 3". the 2.75" provides more low end tq and response with no sacrifice on pump gas. I'm doing a swap to the small downpipe and will document the differences.
One of my customers has a car with identical mods as mine except he runs the 2.75 and is making 10 more wtq several hundred rpm sooner than mine with a 3".
One of my customers has a car with identical mods as mine except he runs the 2.75 and is making 10 more wtq several hundred rpm sooner than mine with a 3".
Originally Posted by EFIxMR
These two cars are running Garage HRS 3" exhaust from the Tanabe 2.75" dp back.
300 wtq at 3500 rpm on 91 octane! Oh Snap!
Five dyno runs done 3 MONTHS apart cannot be construed as anything even remotely "conclusive". I can get the same results here too if we dyno a car midday or after a few cars have been on the dyno, and 8pm and night when it's cooler. Oh Snap! LOL
Gary
Gruppe-S
Originally Posted by Gruppe-S
So based on your 5 dyno graphs, you are saying changing over from 3.0" to 2.75" downpipe yields 7 ft/lbs and 13whp? Haha I think not.
Five dyno runs done 3 MONTHS apart cannot be construed as anything even remotely "conclusive". I can get the same results here too if we dyno a car midday or after a few cars have been on the dyno, and 8pm and night when it's cooler. Oh Snap! LOL
Gary
Gruppe-S
Five dyno runs done 3 MONTHS apart cannot be construed as anything even remotely "conclusive". I can get the same results here too if we dyno a car midday or after a few cars have been on the dyno, and 8pm and night when it's cooler. Oh Snap! LOL
Gary
Gruppe-S
These two cars are running Garage HRS 3" exhaust from the Tanabe 2.75" dp back.
Amongst me and paul we probably have over 20 EVO9's running the 2.75" tanabe dp with over 300 wtq with similar curves.
This is not something I have come to the conclusion with overnight. We have plenty of test data to back it up.
I used to be adament about the 3" dp also. I ran one on my EVO 8 and thought it was great because I didn't have anything else to compare it against. As I drove and tuned more cars with the 3" and the 2.75", I noticed that the 2.75" were much more fun to drive, but before I would tell anyone I tried on my own EVO9 a 3" dp to see if what I thought was true.
Low and behold I actually lost a small amount of tq and my peak tq was moved later, compared to my completely stock exhaust!!!!
What the dyno graph doesn't show is that the transient response on and off throttle with my 3" dp is noticably worse than my stock setup. It is something that the dyno doesn't show, but I can definately feel. Of course my new found top end and midrange with a full exhaust is great, but honestly how often is my daily driver in that powerband?
I'm putting on a 2.75" on my car, not because I can't afford a name brand high dollar 3" downpipe. I'm putting it on because it works better for the type of driving that I do.
Last edited by EFIxMR; Oct 20, 2006 at 02:42 PM.
Evolving Member
Joined: Nov 2005
Posts: 383
Likes: 0
From: Fremont, Ca
Originally Posted by JDMevoBOOST
Best downpipe for a IX???
I'm not looking for some overpriced jdm piece...just looking for something that is reliable, great construction, good welds, good materials.....I'm not really going to discriminate on prices....
would also like to know what are pros and cons of running 2.75" vs 3" dp on a IX that plans to be around 350-400 whp
I'm not looking for some overpriced jdm piece...just looking for something that is reliable, great construction, good welds, good materials.....I'm not really going to discriminate on prices....
would also like to know what are pros and cons of running 2.75" vs 3" dp on a IX that plans to be around 350-400 whp
WORKS...
Originally Posted by Gruppe-S
but with most systems that do not taper, such as the HKS, Apexi GT, Helix, etc. you're in much better shape running a 76mm downpipe.
The Helix V1 downpipe was redesigned to avoid clearance issues on the ACD cars. It is a full 76mm downpipe. Let me grab some pics.
Cheers,
Gary
Gruppe-S
The Helix V1 downpipe was redesigned to avoid clearance issues on the ACD cars. It is a full 76mm downpipe. Let me grab some pics.
Cheers,
Gary
Gruppe-S
Actually, I think 95% of the JDM exhaust all taper where it meets the cat. Are you saying everyone that runs a "taper" exhaust should run a 70mm dp?
I had the 3" Helix v1 dp on my 03 and it was rattling against my subframe but then I guess you can argue that it was a faulty installation or didn't use a kartboy hanger to correct the problem. However, I have installed many TBE without issue so my side of the story is the tolerance on the Helix dp was too large and not up to spec. Lets hope they have corrected that issue and also not burn anymore bumpers.
Going back to the 2.75" vs 3", I have never seen a 3" dp on a stock turbo car made a considerable amount or any more whp then with 2.75" I would love to see a comparison. Are you volunteering to prove 3" dp will make more than 2.75"? I would love to see those graphs since your dynodynamic is coming your way.
Originally Posted by EFIxMR
On my original thread we are actually talking about a total of 4 different cars. Two of which are our customers cars, and the other two are our own EVO 9's we use for testing.
Amongst me and paul we probably have over 20 EVO9's running the 2.75" tanabe dp with over 300 wtq with similar curves.
This is not something I have come to the conclusion with overnight. We have plenty of test data to back it up.
I used to be adament about the 3" dp also. I ran one on my EVO 8 and thought it was great because I didn't have anything else to compare it against. As I drove and tuned more cars with the 3" and the 2.75", I noticed that the 2.75" were much more fun to drive, but before I would tell anyone I tried on my own EVO9 a 3" dp to see if what I thought was true.
Low and behold I actually lost a small amount of tq and my peak tq was moved later, compared to my completely stock exhaust!!!!
What the dyno graph doesn't show is that the transient response on and off throttle with my 3" dp is noticably worse than my stock setup. It is something that the dyno doesn't show, but I can definately feel. Of course my new found top end and midrange with a full exhaust is great, but honestly how often is my daily driver in that powerband?
I'm putting on a 2.75" on my car, not because I can't afford a name brand high dollar 3" downpipe. I'm putting it on because it works better for the type of driving that I do.
Amongst me and paul we probably have over 20 EVO9's running the 2.75" tanabe dp with over 300 wtq with similar curves.
This is not something I have come to the conclusion with overnight. We have plenty of test data to back it up.
I used to be adament about the 3" dp also. I ran one on my EVO 8 and thought it was great because I didn't have anything else to compare it against. As I drove and tuned more cars with the 3" and the 2.75", I noticed that the 2.75" were much more fun to drive, but before I would tell anyone I tried on my own EVO9 a 3" dp to see if what I thought was true.
Low and behold I actually lost a small amount of tq and my peak tq was moved later, compared to my completely stock exhaust!!!!
What the dyno graph doesn't show is that the transient response on and off throttle with my 3" dp is noticably worse than my stock setup. It is something that the dyno doesn't show, but I can definately feel. Of course my new found top end and midrange with a full exhaust is great, but honestly how often is my daily driver in that powerband?
I'm putting on a 2.75" on my car, not because I can't afford a name brand high dollar 3" downpipe. I'm putting it on because it works better for the type of driving that I do.
Cheers,
Gary
Gruppe-S
Originally Posted by tlclee
Actually, I think 95% of the JDM exhaust all taper where it meets the cat. Are you saying everyone that runs a "taper" exhaust should run a 70mm dp?
I had the 3" Helix v1 dp on my 03 and it was rattling against my subframe but then I guess you can argue that it was a faulty installation or didn't use a kartboy hanger to correct the problem. However, I have installed many TBE without issue so my side of the story is the tolerance on the Helix dp was too large and not up to spec. Lets hope they have corrected that issue and also not burn anymore bumpers.
Going back to the 2.75" vs 3", I have never seen a 3" dp on a stock turbo car made a considerable amount or any more whp then with 2.75" I would love to see a comparison. Are you volunteering to prove 3" dp will make more than 2.75"? I would love to see those graphs since your dynodynamic is coming your way.
I had the 3" Helix v1 dp on my 03 and it was rattling against my subframe but then I guess you can argue that it was a faulty installation or didn't use a kartboy hanger to correct the problem. However, I have installed many TBE without issue so my side of the story is the tolerance on the Helix dp was too large and not up to spec. Lets hope they have corrected that issue and also not burn anymore bumpers.
Going back to the 2.75" vs 3", I have never seen a 3" dp on a stock turbo car made a considerable amount or any more whp then with 2.75" I would love to see a comparison. Are you volunteering to prove 3" dp will make more than 2.75"? I would love to see those graphs since your dynodynamic is coming your way.
You mean the Helix V1 I helped you install? The Helix V1 definitely had looser tolerances than the V2, the manufacturer for the V2 downpipe is different as they have better equipment for the manufacturing process. I'll get some dyno graphs when I get a chance.
Cheers,
Gary
Gruppe-S
Newbie
Joined: Sep 2006
Posts: 64
Likes: 0
From: San Diego
What about an invidia exhaust system. i havent heard anything on that. i just purchased one recently, but i think since i already went with the cbe, i might as well finish off with an invidia dp and test pipe. Is this a smart move for the fitment of the exhuast, or should i take my chances and mix up other components like an UR test pipe and Tanabe dp for my ix?