I own a 500+ hp STI
My older brother owns a 600+ hp EVO

For the last week or so i have been drivin around in his car which even on his 100 octane street map makes about 570 crank hp...heres a link to the review


http://forums.evolutionm.net/showthread.php?t=108709

U can imagine what dinners like @ my house when we get together.... :D

Its fun to compare the two cars after they each have had some good upgrades done...

Any pics or videos... they sound nice.

I would be more interested to see some dyno chart comparisons.

I would be more interested to see some dyno chart comparisons.
Both cars have plenty of dyno charts, but none on file...last time out on race fuel the STI put down 371 hp/395 torque....the EVO 471 hp/398 torque both on Vishnus DD DYNO.

My Stis currently havin some serious motor work done and should have some more power soon. :banana:


With 420 WHP the EVO ran a 11.5@122 :D ...no times yet with the 470WHP
The STI did a 11.8 @116 with 342 WHP

I should have some Pics up soon of both cars together

Ok so this may be a dumb question considering you own the STI, but... If you had to do it over again would you still get the STI over the Evo?

well hey, you can always go the built 2.8L route with a few grand worth of headwork.


I will simply not believe if you tell me a fully built 2 liter will make more power than a fully built 2.8 liter, given same volumetric efficiencies (which should be no problem with extensive headwork) and same airflow capacity via rev limits (which should be no problem with extensive headwork, and a built block. The I-speed 2.8L is revved to 8500 methinks?).

well hey, you can always go the built 2.8L route with a few grand worth of headwork.


I will simply not believe if you tell me a fully built 2 liter will make more power than a fully built 2.8 liter, given same volumetric efficiencies (which should be no problem with extensive headwork) and same airflow capacity via rev limits (which should be no problem with extensive headwork, and a built block. The I-speed 2.8L is revved to 8500 methinks?).
How about a 2.35 with a 8300 redline with a solid deck and built internals???...

Ok so this may be a dumb question considering you own the STI, but... If you had to do it over again would you still get the STI over the Evo?
i tried to buy a 05 EVO just a few weeks ago.....but the old wife won't let me.
So we bought somethin else :(

As long as i have my STI i'm :banana:

ok thats entirely way tooo much power for both of you, but thats sick

Both cars have plenty of dyno charts, but none on file...last time out on race fuel the STI put down 371 hp/395 torque....the EVO 471 hp/398 torque both on Vishnus DD DYNO.

My Stis currently havin some serious motor work done and should have some more power soon. :banana:


With 420 WHP the EVO ran a 11.5@122 :D ...no times yet with the 470WHP
The STI did a 11.8 @116 with 342 WHP

I should have some Pics up soon of both cars together

Were those drag number on pump or race gas?

:eek:

Were those drag number on pump or race gas?
vp C16

Both cars have plenty of dyno charts, but none on file...last time out on race fuel the STI put down 371 hp/395 torque....the EVO 471 hp/398 torque both on Vishnus DD DYNO.

My Stis currently havin some serious motor work done and should have some more power soon. :banana:


With 420 WHP the EVO ran a 11.5@122 :D ...no times yet with the 470WHP
The STI did a 11.8 @116 with 342 WHP

I should have some Pics up soon of both cars together

how the hell is he only .3 second faster than you? he has about 80 hp on you. :)

driver skill....i guess Mark puts Tom in his place where it matters =X

so, is the evo with stock internals? if it is that's damn inpressive. :banana:

so, is the evo with stock internals? if it is that's damn inpressive. :banana:

Hks 272 cams/ARP head studs...only mods to the internals.

Stock intake box/throttle body/intake manifold/bottom-end

mark. while your car is under the knife, spring (no pun intended) for an external wastegate setup. that will give you at least a good 30whp or so.

Hands down the 4G63 is a better motor. Stock clutch can wave bye bye though, but still. It's been proven for many years in the U.S. I would have seriously considered an Evo had it not been for Mitsubishi's dealership reputation...



Mika

how the hell is he only .3 second faster than you? he has about 80 hp on you. :)

Check out the trap speed difference. STi probably had a [much] better launch :D

Damn... I wish my brother had either one of your cars.

Wait... I don't have a brother. :confused:

i have 2.5 bpm forged internals for sale, if your interested. you will put your brother to shame with this and it's cheap.

hmmm, One thing that I learned from reading this is that the Evo has a cast iron closed deck block. I did not know that. That it a serious advantage for the Evo. Too Bad that the 4g63s have 2.5 ltrs of displacement. They really are nice motors. However, I havnt heard of any STi owners doing any damage to the block itself, so that should be a testiment to its strength. If you put forged pistons on the STi the close call between the two engines would be even closer.

The EVO leaves much to be desired in terms of torque. Tom's EVO pulls like crazy but the torque isn't there...for some thats great. I wouldn't want to be dealing with a bunch of torque on a road course...but for street driving I enjoy torque =)

the subie is already behind out of the gates with the fact that it is an aluminum block...not necessarily because it is weaker, but because it is noisier. you have to tune the ej engines with a lot of caution because of this...and is made even harder since the ej engines like timing.

another hit comes when you realize the turbo on the ej motors is a good 2-3ft off of the block. the evo's turbo is no more than 6" off the block.

ive yet to hear of anybody with engine problems because of cylinder wall flex (people were saying how thin the walls were). i dont think the iron/closed deck has really any advantage over the aluminum/semi-closed other than quieter and therefore easier to tune at the limit.

Why would 6" long header primaries be better than that of the subaru?
Why does an external WG make more power, specifically when they it's running the same boost as an internal WG?

Paul

another hit comes when you realize the turbo on the ej motors is a good 2-3ft off of the block. the evo's turbo is no more than 6" off the block.

Sort've makes one wonder why all of the our Suby-friendly vendors haven't developed a reversed intake manifold, modified ex manifold, up and down pipes, radiator in place of TMIC and FMIC package.:D It obviously wouldn't be an inexpensive package, but would probably be pretty popular.

I want to learn how to weld. I've given some thought to fabricating my own exhaust manifold and such that would allow me to put the turbo equidistant(sp) from each runner. Sorry for the hijack.

But why is such a short header length (such as the stock evo) any better?

When given the free choice, indy car and turbo F1 cars did not use such at arrangement.

Paul

Pavlo,

I imagine that there are two answers here. First, Indy and turbo F1 cars have packaging issues that just do not apply to street cars. A turbo hanging where the runners et al are shorter might require some aerodynamic or structural compromises that kill the advantage. They don't really have "free choice", as every idea has a cost. If the turbo was sitting right on the side of the block, keeping the shortest possible intake path, you would have to build cooling ducts to remove heat, spoiling aerodynamics, and you would need to build a big old lump in the nice smooth fairing, further disrupting aerodynamics. Those old, nearly unlmited, venturi-tunnelled F1 turbo cars had something insane like 4000lbs of downforce. 50 extra WHP would not be worth losing 600lbs of downforce and a .01cd.

For the first question, and I know that you know a lot of this, and more about a lot of it that I do, but, in general, hot, fast gas works better hitting the turbine than cold, slow gas. The turbine is just a heat-pump, after all. The longer the path, the more heat and speed you lose, meaning you run the turbine less energetically, slowing spool and reducing flow while increasing backpressure (to a point). Yes, I know that there are other considerations, but it's generally accepted that the shortest possible stable exhaust path from head to turbine is best. I know that "generally accepted" does not mean "100% accurate", but, speaking strictly from personal experience, hot headers work better than cold headers, to the tune of 10+ whp on the dyno. If hot headers work better, shorter headers, which A) will be hotter, faster and B) will allow faster, hotter gas flow, will work better also.

For the question a little while ago - about how an external wastegate makes more power - of course it can't. Unfortunately, some people think that it is worth "30whp" (sorry, hap - this is not personal...), and so that gets spread. They think this because a couple of well-known tuners have expressed this opinion. Yes, it is EASIER to tune a car for consistent, big power with an external gate. This is just because it makes consistent, solid boost that much easier. If you dial in 24psi and have 1psi of "drift" with an internal gate with no det, you are going to see 23-25psi at peak, right? If an external gate on the same setup gives you only .5psi of float, you can probably tune out to 24.5psi peak, and see 24-25psi once the "drift" is allowed for. So, on certain setups, you can probably make a little more power, a little more consistently, with an external gate. But 30whp? Come on!

-Sean

Mark, your STi is the one that edged out the Viper a couple times at the track, right? I think you took 2 of 4 races, where you kept spanking him out of the hole, and then holding him off til the finish line?

I can't wait to see what your new set up brings.

On the face of it, short headers seem like a good idea, but I am not sure they are all they are cracked up to be. Indy cars could put the turbo very close to the head if they wanted, but they are really quite long. This may be down to the high compression/low boost setup that is used.

It appears that EVOs need more boost than Imprezas to run the same power. It's also worth noting the port sizes in the EVO are much smaller.

Paul

FP Green STI would be a good comparison to a stock turbo EVO

ive yet to hear of anybody with engine problems because of cylinder wall flex (people were saying how thin the walls were). i dont think the iron/closed deck has really any advantage over the aluminum/semi-closed other than quieter and therefore easier to tune at the limit.
I have had a few talks with some tuners about the block...and the concern came that HIGH HP ( Read 600+ HP) levels the block would not hold due to a few different reasons one being the semi inclosed design and that it may have issues of expansion and contraction @ high hp levels. :confused:

Evotomi my older brothers pushin 471+ hp on the DD dyno...which is in the 660-670 crank hp level...with little internal mods. :eek:

I hope to push high power levels, but for me...i shall be using a solid deck 2.35 motor with some strong internals ;)

It appears that EVOs need more boost than Imprezas to run the same power.

Evo - 2.0L
STi - 2.5L

Mark, your STi is the one that edged out the Viper a couple times at the track, right? I think you took 2 of 4 races, where you kept spanking him out of the hole, and then holding him off til the finish line?

I can't wait to see what your new set up brings.
Thats was i :D
Now the viper guy has installed a Cam and line lock

Next year we have a rematch....either way i'll lose, if i best his 03 SRT10 he has another 1000+ hp viper sittin @ home :eek: bastard

FP Green STI would be a good comparison to a stock turbo EVO

In terms of spool time maybe, but the stock turbo is a 16g, right? And I believe that the green is based on a 20g. So a green will definatly out flow the stock evo turbo.

Why would 6" long header primaries be better than that of the subaru?
Why does an external WG make more power, specifically when they it's running the same boost as an internal WG?

Paul

Pavlo, big adventure is right. A wastegate alone wont make more power for you. But it will hold boost more consistantly. You most likely would not have creep issues you have with an internal. Therefore making it easier to tune and possibly yeilding a small amount of extra HP.

In terms of spool time maybe, but the stock turbo is a 16g, right? And I believe that the green is based on a 20g. So a green will definatly out flow the stock evo turbo.

Compare the times and dyno #'s his car ran to what the big shops get with a EVO on the stock turbo.

http://buschurracing.com/EVO_Stage4.html

robvas, great link. The dyno numbers are almost identical to each other. I couldnt find any info on the EVo times however. Just goes to show what a nice turbo that Mitsu fitted the Evos with. In Regards to te EVO MR, does it have the same 16g turbo?

Compare the times and dyno #'s his car ran to what the big shops get with a EVO on the stock turbo.

http://buschurracing.com/EVO_Stage4.html
The 11.5 pass was runnin with the weaker 420 hp map and it was the first time out with this setup u could say "shake down passes"...the car will be out again in a few days, this time running FULL power...

I would have seriously considered an Evo had it not been for Mitsubishi's dealership reputation

Precisely why i bought an STi

Does Mitsu have a bad customer service reputation? They're supposed to be the "best backed cars in america". After hearing about so many people having bad experiences with Subaru dealers, I doubt Mistu could be any worse....but I coul be wrong.

On the face of it, short headers seem like a good idea, but I am not sure they are all they are cracked up to be. Indy cars could put the turbo very close to the head if they wanted, but they are really quite long. This may be down to the high compression/low boost setup that is used.

It appears that EVOs need more boost than Imprezas to run the same power. It's also worth noting the port sizes in the EVO are much smaller.

Paul

Its simple thermodynamics. You shorten the distance between the combustion point and the point at which force is needed to spin the turbine wheel and less energy is lost to gas compression. It is all about efficiency. Otherwise we would have yards and yards of pipe with no drawbacks. When you think about this, don't think "Indy cars do it so it must be right", think about it from a physics perspective. Our cars are governed by physics, indy cars are governed by a sanctioning committee :D

Of course the EVO needs to run more boost...it is .5L smaller. This does not mean it is worse. I'd still like to know where all of the 1000hp EJ's are
:p

And as for dealer reputations, as long as people are modding the crap out of their cars and still expecting warranty coverage, I guess we will have whiners...on the other hand, I do not agree with Subaru/Dodge/Mitsubishi's choice to troll forums in order to void people's warranties.

Its simple thermodynamics. You shorten the distance between the combustion point and the point at which force is needed to spin the turbine wheel and less energy is lost to gas compression. It is all about efficiency. Otherwise we would have yards and yards of pipe with no drawbacks. When you think about this, don't think "Indy cars do it so it must be right", think about it from a physics perspective. Our cars are governed by physics, indy cars are governed by a sanctioning committee :D

Of course the EVO needs to run more boost...it is .5L smaller. This does not mean it is worse. I'd still like to know where all of the 1000hp EJ's are
:p

And as for dealer reputations, as long as people are modding the crap out of their cars and still expecting warranty coverage, I guess we will have whiners...on the other hand, I do not agree with Subaru/Dodge/Mitsubishi's choice to troll forums in order to void people's warranties.

Excuse me?

First, I never mentioned anything about 2.5 STIs did I? I am comparing 2.0 to 2.0 engines.

Second. It's not a case of 'simple' thermodynamics. If the 'energy' is lost between the point of combustion and the turbine wheel, where exactly is it lost to, what is this 'gas compression' you talk about? Bearing in mind we must have conservation of energy, and we make efforts to insulate our headers. Also, we only need a certain amount of energy to drive the turbine, excess energy (in the form of pressure) is bled off by the wastegate.

The other thing to remember when it comes to headers, is when we are spooling up the turbo (comparatively small gas flow) we are relying on the pulses (pressure waves) that come down the headers to drive the turbine.

Short headers will allow minimum loss of pressure wave intensity for a large diameter, which in turn aids flow. However we can still make use of pulse tuning which relies on header length as well as pressure wave intensity, to better scavenge the engine.

Paul

ok, yeah i probably shouldve been more clear.

of course by itself, an external wastegate running the same boost as an internal wastegate would net the same power. like people have said, the true advantage comes from the rock solid and pretty consistent boost that comes from the external wastegate. theres no creep and not a lot of variances run to run.

my analogy is this:
stock ecu is to UTEC as internal wastegate is to external wastegate.

where with the stock ecu, there are so many variables to try to determine what type of tune your car is going to run, where as with the utec, its going to run the same thing everytime. if all variables are going to be the same everytime, the utec (in theory) should provide a tune that can be closer to the "edge" time after time.

with the internal wastegate, you are more prone to creep when warm out, more creep when cold out, huge variances in boost when cold out, etc...when with the external, it will more or less stay the same all year round.

the more you can predict what your car will do under every circumstance, the closer you can run near the limit safely.

sorry i wasnt more clear about that. no offense taken, sean. :)

I don't get these big variations in boost with an internal gate using a correctly setup AVC-R. Boost hits target in every gear apart from 1st, every time. Spike is a very short 1 PSI that is only seen on a digital peak reading, but not on a lightly damped analog gauge. Self learn takes care of adjustments needed seasonally, but I don't get the temperature swing here some of you guys get admittedly.

If the boost is slightly higher or lower than desired and you are running on the edge, it will just be exchanged for a bit of timing and I don't think the end result would be too different. At say 22 PSI, what difference will 1 PSI make to power or torque, at most less than 3% and that is even assuming that an increase in pressure ratio will give you a proportional rise in power if you are on the edge.... nothing like. If I top out my turbo at peak power for the octane I'm using, I have a fairly wide variation of boost levels I can run either side and make very similar power just by exchanging timing for boost.

If there was a difference would it not be more to do with smoother gas flow through the wastegate and turbine housing? And having an externally venting wastegate which frees up the exhaust back pressure?

Did MARKGSTI ever post dynos of both the modified EVO and the modified STi? The link posted above by MARKGSTI is for a different EVO, isn't it?

I would be curious to see the useable powerband/peak hp & torque range of each car. Besides the posted times for the cars being close on the drag strip being attributed to the EVO's first run with some of the mods/tune and driver differences, some of the close timing on the drag strip might have alot to do with both car's RPM peak power range. I could be wrong - it's just a thought.

Excuse me?

First, I never mentioned anything about 2.5 STIs did I? I am comparing 2.0 to 2.0 engines.

Second. It's not a case of 'simple' thermodynamics. If the 'energy' is lost between the point of combustion and the turbine wheel, where exactly is it lost to, what is this 'gas compression' you talk about? Bearing in mind we must have conservation of energy, and we make efforts to insulate our headers. Also, we only need a certain amount of energy to drive the turbine, excess energy (in the form of pressure) is bled off by the wastegate.

The other thing to remember when it comes to headers, is when we are spooling up the turbo (comparatively small gas flow) we are relying on the pulses (pressure waves) that come down the headers to drive the turbine.

Short headers will allow minimum loss of pressure wave intensity for a large diameter, which in turn aids flow. However we can still make use of pulse tuning which relies on header length as well as pressure wave intensity, to better scavenge the engine.

Paul


Then I don't see what the problem is. My time is spent here. It just sounds like you are doing too much bench-engineering.

Did MARKGSTI ever post dynos of both the modified EVO and the modified STi? The link posted above by MARKGSTI is for a different EVO, isn't it?

I would be curious to see the useable powerband/peak hp & torque range of each car. Besides the posted times for the cars being close on the drag strip being attributed to the EVO's first run with some of the mods/tune and driver differences, some of the close timing on the drag strip might have alot to do with both car's RPM peak power range. I could be wrong - it's just a thought.
I never did post any dyno results....the printer over @ the shop is broken, but my 371 hp map is up on Vishnus Evolutionm site.....


The Evo will be out @ the track Saturday to get some more runs this time runnin 31#'s of boost with the gt35R, makin about 480 WHP on the DD dyno. :huh:

I don't get these big variations in boost with an internal gate using a correctly setup AVC-R. Boost hits target in every gear apart from 1st, every time. Spike is a very short 1 PSI that is only seen on a digital peak reading, but not on a lightly damped analog gauge. Self learn takes care of adjustments needed seasonally, but I don't get the temperature swing here some of you guys get admittedly.



Seconded - I could not maintain stable boost with either the UTEC or an MBC. AVCS would kick in, and boost would drop. I switched to AVC-R, and voila, ROCK solid boost.

Pavlo - Just so you know, I was agreeing with you - external gates do not make for "drastically" more power. And I agree with John, one place that they likely would improve power is by smoothing the flow, however, I think that would only be noticable with a dedicated external-gate setup - not an internal-gate housing with the flapper welded shut. To address your argument against the advantages of short headers - first, even if you jethot AND wrap the header, you still lose some heat and speed as the gas flows down the pipe. It radiates, and alot of it is swept away by airflow. But, let's not forget, very, very few members of the modded community actually wrap OR coat their headers, and almost nobody does both. They certainly don't come that way stock. And if they are not wrapped, they lose TONS of heat.

-Sean

Does Mitsu have a bad customer service reputation? They're supposed to be the "best backed cars in america". After hearing about so many people having bad experiences with Subaru dealers, I doubt Mistu could be any worse....but I coul be wrong.

As far as the Subaru horror stories, there's always 2 sides of the story. I've chilled at a Subaru dealership from time to time, and half the time owners try to "pull the wool" over the dealerships eyes. The dealership will deny warranty claims if they see obvious signs of modifications and reverting the car back to stock. Like some folks will put on X mod, and then remove it and put the stock back in place. What are you trying to hide? Be honest with them. I've had cam seals replaced under warranty after I put a turbo on. I was up front with them and I told them it was leaking before I installed the turbo. They said thanks for being cool and next time it's on your dime. I said thanks. :)

If you check out evolutionm.net, there'll be plenty of guys that have been denied warranty because the dealerships were being a-holes. Does Subaru do that? Yes, but it seems that they're not as extensive as Mitsu is. The "best backed cars in America" is just a gimmick. They might as well put a disclaimer on the bottom that says "excludes Evo's".

As far as modding the crap outta cars, yeah, then you're SOL when it comes to powertrain warranty. But sometimes things go wrong with other parts of the car. I'd like to have that stuff taken care of without a hassle. I guess I'm really lucky, living 20 minutes away from a mod-friendly dealer. They're really cool folks there. I'd like to think other dealerships are similar. They don't go out to tracks and take down VIN's and license plates #'s, unlike Mitsu. I should say that I've never heard of that from Subaru.

There are also people out there that lightly modify cars(exhaust, intake, AP). They want to be taken care of. Most Subaru dealerships will take care of them. Meh, I'm not bashing the product, but the folks backing it(Mitsu of America). They had a good product back in the day with the GST and GSX, and they hosed the customers back then. Now, they got a good product in the Evo, but people have learned from their first mistake. The past few years Mitsu has had financial problems, which makes me a bit more leary than usual. This, obviously is all my opinion. That and 1 buck will get me a cup of coffee...



Mika

Then I don't see what the problem is. My time is spent here. It just sounds like you are doing too much bench-engineering.

Don't think that is a fair accusation to throw at Paul when he has engineered his Scooby and is running 10s without nitrous on street legal tyres. :devil:

Seconded - I could not maintain stable boost with either the UTEC or an MBC. AVCS would kick in, and boost would drop. I switched to AVC-R, and voila, ROCK solid boost.

Pavlo - Just so you know, I was agreeing with you - external gates do not make for "drastically" more power. And I agree with John, one place that they likely would improve power is by smoothing the flow, however, I think that would only be noticable with a dedicated external-gate setup - not an internal-gate housing with the flapper welded shut. To address your argument against the advantages of short headers - first, even if you jethot AND wrap the header, you still lose some heat and speed as the gas flows down the pipe. It radiates, and alot of it is swept away by airflow. But, let's not forget, very, very few members of the modded community actually wrap OR coat their headers, and almost nobody does both. They certainly don't come that way stock. And if they are not wrapped, they lose TONS of heat.

-Sean
mine are coated AND wrapped. so that makes at least one member on this board. ;)

I think the major benefit to an external gate is instead of your wastegate exhaust and the turbine exhaust meeting right behind the turbine and making a sharp turn in the downpipe, the external gate places this merge farther downstream, or else has a separate dump pipe.. you end up with slightly less backpressure due to a smoother transition, and we all know since the turbo works on temp/heat difference, less backpressure exhaust means less backpressure on turbine inlet, which means engine VE as a system inproves and you can make more power.

I never did post any dyno results....the printer over @ the shop is broken, but my 371 hp map is up on Vishnus Evolutionm site.....

The Evo will be out @ the track Saturday to get some more runs this time runnin 31#'s of boost with the gt35R, makin about 480 WHP on the DD dyno. :huh:

Man, 31# is big. :huh: is right!

Does anybody have any estimates on how much boost a totally rebuilt EJ257 could run?

Don't think that is a fair accusation to throw at Paul when he has engineered his Scooby and is running 10s without nitrous on street legal tyres. :devil:

That's great, I respect anyone who can build a 10 second car.

But trying to reason why longer piping is not worse than short piping is a little backwards.

header tuning comes injto play with long and short pipes too, for the F1 cars I mean..

That's great, I respect anyone who can build a 10 second car.

apparently, you don't. i believe your words were a bit less than respectful.

But trying to reason why longer piping is not worse than short piping is a little backwards.

:lol:

i laugh at your self-aggrandizing idea that you know it all. perhaps--and just entertain the idea for a split second--there are some factors you have overlooked?

apparently, you don't. i believe your words were a bit less than respectful.



:lol:

i laugh at your self-aggrandizing idea that you know it all. perhaps--and just entertain the idea for a split second--there are some factors you have overlooked?

Like what...short pipe, other things held constant, has better energy transfer than long piping? Please give me examples of things overlooked...

i find it hard to understand how you totally blew off paul's direct rebuttal to your gross oversimplification--and now ask me to expound on the very same contributing factors--but here's a kick in the right direction:

pipes resonate

i find it hard to understand how you totally blew off paul's direct rebuttal to your gross oversimplification--and now ask me to expound on the very same contributing factors--but here's a kick in the right direction:

pipes resonate

<inserttongueincheek>

Not if you fill them with steel and bury the assembly in concrete!!!!

I'm not sure how well they would flow, though...

</inserttongueincheek>

:p

-Sean

In addition to the overal flow, there is also the pulse tuning aspect to consider. I am not claiming that we should all embrace the long headers that the EJ gives us in it's default package, only they we shouldn't discount the good aspects of such a design.

Due to the turbine it complicates things and negates some of the gains to be had. But on a N/A engine the design of the headers is VERY important. You don't see petrol running motors with very short headers to increase flow.

Short headers will normally give better high RPM performance as the time for a pulse to travel from the valve, to the collector and back again is shorter. But when the pulse returns from being reflected at the open end of the primary, it returns with negative pressure, ie suction, and helps scavenge the cylinder if the exhaust valve is open. The end effect is going to depend on how large the exhaust side of the turbo is and how low the back pressure is in general.

A WRC subaru does have a shorter set of headers, I would estimate that they are some 8 inches shorter overall, as the turbo sits on it's back just above the engine subframe (turbine shaft pointing down). So I can only assume it would be nice if the headers were a little shorter, although the packaging and weight benefits of the WRC setup are considerable too, so who knows. I will try and ask someone at Prodrive.

Paul

Seconded - I could not maintain stable boost with either the UTEC or an MBC. AVCS would kick in, and boost would drop. I switched to AVC-R, and voila, ROCK solid boost.

Pavlo - Just so you know, I was agreeing with you - external gates do not make for "drastically" more power. And I agree with John, one place that they likely would improve power is by smoothing the flow, however, I think that would only be noticable with a dedicated external-gate setup - not an internal-gate housing with the flapper welded shut. To address your argument against the advantages of short headers - first, even if you jethot AND wrap the header, you still lose some heat and speed as the gas flows down the pipe. It radiates, and alot of it is swept away by airflow. But, let's not forget, very, very few members of the modded community actually wrap OR coat their headers, and almost nobody does both. They certainly don't come that way stock. And if they are not wrapped, they lose TONS of heat.

-Sean

I was just asking for clarification on the WG thing. I have seen various people quoting magical power increases.

As for energy loss in the headers, the ideal set of headers would lose lots of energy at full power, as that would reduce back pressure and increase mass flow with cooler, denser exhaust gas (provided of course we still have enough to drive the turbine to our satisfaction). However that's very poor for spoolup, where I think we all agree we wan't high velocty.

I am not saying long is better full stop. They have some advantages, so we should try and make the most of them before resorting to playing around with radiators and the like.

Paul

mine are coated AND wrapped. so that makes at least one member on this board. ;)

Im another. I had all my pipes wrapped.

fwiw, with tuned intake headers one can achieve an "effective" supercharging pressure of 10 psi for narrow bands of frequencies/rpms. in other words, the pressure peak produced at the proper time pushes the charge air in as if you had 10 psi of boost. the differences are a) this boost is "free" since it does not require any exhaust or crankshaft energy to produce it, and b) it is only available at a narrow range of rpms.

i see no reason why similar results are not produced on the hot side, that is to say, inside the exhaust manifold. wouldn't it be nice to have a 10psi LESS exhaust gas back pressure right at the exhaust port? hell i would even take 3psi less...

correct me if i'm wrong, but aren't subie engines generally regarded as having decent low-end torque? compared to other engines of similar displacement? look directly to the longer runners, intake and exhaust, for a possible cause, as these shift the resonant frequencies downward vs. the short runners of a inline or even v config engine.

ken

fwiw, with tuned intake headers one can achieve an "effective" supercharging pressure of 10 psi for narrow bands of frequencies/rpms. in other words, the pressure peak produced at the proper time pushes the charge air in as if you had 10 psi of boost. the differences are a) this boost is "free" since it does not require any exhaust or crankshaft energy to produce it, and b) it is only available at a narrow range of rpms.

i see no reason why similar results are not produced on the hot side, that is to say, inside the exhaust manifold. wouldn't it be nice to have a 10psi LESS exhaust gas back pressure right at the exhaust port? hell i would even take 3psi less...

correct me if i'm wrong, but aren't subie engines generally regarded as having decent low-end torque? compared to other engines of similar displacement? look directly to the longer runners, intake and exhaust, for a possible cause, as these shift the resonant frequencies downward vs. the short runners of a inline or even v config engine.

ken

exactly

a proper EVO engine/manifold etc.

RallyX EVO:

http://www.lancerregister.com/attachment.php?postid=257503

http://www.lancerregister.com/attachment.php?postid=257788

It seems pretty obvious to me that on a turbocharged motor that shorter headers are preferred because as the heat is lost, the velocity of gas slows. In order to maximize gas velocity and turbo efficiency keep the distance short. In addition, the longer the pipe the more potential for backpressure as hot gas has to try to push through slower,cooler gas. Maybe this is related to why the STI/WRX likes bigger turbo housings. I think the tuned header, equal length headers, definitely are factor but probably less significant when compared to overall distance.

correct me if i'm wrong, but aren't subie engines generally regarded as having decent low-end torque? compared to other engines of similar displacement? look directly to the longer runners, intake and exhaust, for a possible cause, as these shift the resonant frequencies downward vs. the short runners of a inline or even v config engine.

ken
nope, subie engines generally have pretty weak low-end torque as compard to other engines with the similiar displacement(such as evo or even vw's 1.8t) due to nearly 6 ft long of exhaust plumbing. the boxer engine design just complicates exhaust plumbing. Wouldnt 1 more cylinder on each side and twin turbos be a more ideal setup :)

nope, subie engines generally have pretty weak low-end torque as compard to other engines with the similiar displacement(such as evo or even vw's 1.8t) due to nearly 6 ft long of exhaust plumbing. the boxer engine design just complicates exhaust plumbing. Wouldnt 1 more cylinder on each side and twin turbos be a more ideal setup :)

Not at the same boost. Don't confuse lack of torque for poor spoolup, which is definitely hampered by long headers (to a point).

Paul

yes, as paul pointed out, i'm not necessarily talking about a forced induction setup... how about a good old NA ej25?

http://www.protekperformance.com/rv7/engine/dyno_graph.jpg