problem with using stock header for turbo app?

waren · 04-16-2002, 06:35 PM

This forum is a great idea.

I have been trying to design a turbo kit for my 97' Legacy GT (EJ25) and this forum has been a gold mine of information. A few months ago SCC had an article about building an exhaust manifold for a turbo application.

The recomendation was NOT to use mild steel. Yet it seems that most "kits" use the factory headers on the EJ25 and connect the up pipe for the turbo at the "Y" where the factory cat once was.

I assume that the factory headers are carbon steel (mild steel) and not stainless. According to SCC this setup shouldnt last long. BUT I havent read of any problems.

Since I have a legacy I dont think that I can use the stock legacy turbo manifold [ problem with cross member?]. So I either have to use the stock headers ... or fab a complete manifold.

It would be a lot eaiser to use the factory headers and just bolt on at the "Y" ..... has anyone had a problem with this configuration?

Leaks?
Warping over time?
weight of the turbo causing problems? (how should I support the turbo?)

If the steel tube stock headers are OK ... one has to ask why wouldnt steel tube up and down pipes be OK?

If anyone has experiences to share I would really appreciate it.

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markus · 04-16-2002, 09:23 PM

IIRC, stock EJ25 exhaust manifold is made from cast iron and not carbon steel. The cast iron would make it very robust, but the piping diameter is very small (1.75" I think).

There has been a lot of discussion on this board as to whether the stock manifold is the best solution, however, I think that the Vishnu turbo kits which make crazy amounts of power use the stock EJ25 exhaust manifold, so you should be okay sticking with that.

Revision · 04-17-2002, 01:01 AM

I don't know man. It looked like bent aluminized pipe to me..

Dang, no pre-jethot pictures...

waren · 04-17-2002, 01:18 PM

Quote:

Originally posted by Revision
I don't know man. It looked like bent aluminized pipe to me..

Thanks for posting the picture!

I havent had the heat shields off my stock pipe yet to have a good look .. but I expected it to be tube.

From a design perspective, why would Subaru add all that weight [of a full cast manifold] if the exhaust temps etc. of a turbo didnt require it?

The manifold flanges are likely cast and maybe the "y" connection too.

Anyway, I guess if its cast or not doesnt really matter, even if we know cast would be better. If guys have 50,000 miles on their RS-T s [ after the turbo ] with no problems maybe its not worth worrying about?

8Complex · 04-17-2002, 01:26 PM

I believe that the collectors are cast and the tubes are bent/welded on from there.

BTW, don't believe everything you read... especially not from SCC.

Not that they're totally non-credible, but they're just commonly mistaken.

waren · 04-17-2002, 02:57 PM

Quote:

Originally posted by 8Complex
I believe that the collectors are cast and the tubes are bent/welded on from there.

BTW, don't believe everything you read... especially not from SCC. Not that they're totally non-credible, but they're just commonly mistaken.

Hey, Thanks for the post!

And good point on SCC, you have to wonder what publications some of those guys worked for before they became car "experts".

Anyway I looked at some of your old posts and I found that you have a stage III ludeSPEED turbo kit that you arent running.

Why did you take it off [hope you dont mind me asking ..]

engine mechanical trouble? engine management ?

I really want to try a turbo but I have read enough about the EJ25 to cause some concern [ even at 5 - 7 psi].

It would be great to know your experience and what made you decide to take the turbo off

Revision · 04-17-2002, 04:50 PM

Actually, nothing on that Y-Pipe is cast..
The main collectors are bits of tubing welded togther and the final section on the Y is also two bits of tubing, one welded inside of the other.

I take that back, I believe the flanges to be cast.

As for 8Complex, can you say 3 engines a tranny and currently a body kit.

8Complex · 04-17-2002, 06:05 PM

Quote:

Originally posted by waren
Why did you take it off [hope you dont mind me asking ..]

engine mechanical trouble? engine management ?

Well, the turbo got me for a motor and a trans so far. Now the trick will be to drive easier (already learned to do that on the ACT clutch) and to tune it right. I have mainly been holding off because I don't have the cash to get the engine management I want/need to take care of doing it right.

At this point, I most likely will be selling the kit as a non-engine-managment kit (ie: you NEED to get something to run the kit) and building up another on my own (will need a few tools, but should be a piece of cake). Depending on the cash situation, of course. If I can only afford engine management and no motor build, I may put the kit back on and run low-boost with the 440cc injectors I have sitting here.

Revision - You're probably half-right... those collectors are probably stamped steel (in halves) and welded together. The flanges, however, are machined steel plates... they don't have the right texture to have been cast.

waren · 04-18-2002, 02:57 PM

Quote:

Originally posted by 8Complex

Well, the turbo got me for a motor and a trans so far. Now the trick will be to drive easier (already learned to do that on the ACT clutch) and to tune it right.

Thanks for posting , I have one last question. [ Im pulling this thread as far as I can

] What is the most common failure for boosted EJ25's ? You didnt really mention what happened in your case.

Was it rebuildable? I guess what I am asking is has anyone destroyed a block [open deck] and if so at what power level or boost level.

If it was a ECU issue then I could see head gasket, burned valves, rings, maybe pistons ... its bad but life goes on if the crank, rods and block can be reused.

My understanding was that the EJ25 could safely take 250 HP, I was hoping for around 225 HP with proper management.

Thoughts?

8Complex · 04-18-2002, 03:11 PM

The most common problem is detonating and taking a chunk out of the crown of the #4 piston. It's the furthest from the FPR so the theory goes that it doesn't get enough fuel and therefore runs hotter and is much more prone to detonation.

The other major failure is stripping second gear, though it happens NA as well, just have to beat on it harder.

04-16-2002, 06:35 PM	#1
waren Scooby Newbie Member#: 17584 Join Date: Apr 2002	problem with using stock header for turbo app? This forum is a great idea. I have been trying to design a turbo kit for my 97' Legacy GT (EJ25) and this forum has been a gold mine of information. A few months ago SCC had an article about building an exhaust manifold for a turbo application. The recomendation was NOT to use mild steel. Yet it seems that most "kits" use the factory headers on the EJ25 and connect the up pipe for the turbo at the "Y" where the factory cat once was. I assume that the factory headers are carbon steel (mild steel) and not stainless. According to SCC this setup shouldnt last long. BUT I havent read of any problems. Since I have a legacy I dont think that I can use the stock legacy turbo manifold [ problem with cross member?]. So I either have to use the stock headers ... or fab a complete manifold. It would be a lot eaiser to use the factory headers and just bolt on at the "Y" ..... has anyone had a problem with this configuration? Leaks? Warping over time? weight of the turbo causing problems? (how should I support the turbo?) If the steel tube stock headers are OK ... one has to ask why wouldnt steel tube up and down pipes be OK? If anyone has experiences to share I would really appreciate it. * Registered users of the site do not see these ads.

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04-16-2002, 09:23 PM	#2
markus Scooby Specialist Member#: 438 Join Date: Oct 1999 Chapter/Region: W. Canada Location: St. Albert, AB, Canada Vehicle: 2004 STi White on Gold	IIRC, stock EJ25 exhaust manifold is made from cast iron and not carbon steel. The cast iron would make it very robust, but the piping diameter is very small (1.75" I think). There has been a lot of discussion on this board as to whether the stock manifold is the best solution, however, I think that the Vishnu turbo kits which make crazy amounts of power use the stock EJ25 exhaust manifold, so you should be okay sticking with that.

04-17-2002, 01:01 AM	#3
Revision Scooby Guru Member#: 242 Join Date: Sep 1999 Chapter/Region: MWSOC Location: Carol Stream, IL USA Vehicle: MY05 PSM GGA !STOCK MY99 RS-RIP / MY95 MX-5	I don't know man. It looked like bent aluminized pipe to me.. Dang, no pre-jethot pictures...

04-17-2002, 01:26 PM	#5
8Complex Moderator Member#: 922 Join Date: Feb 2000 Chapter/Region: MWSOC Location: Schaumburg, IL Vehicle: 04 FXT Red	I believe that the collectors are cast and the tubes are bent/welded on from there. BTW, don't believe everything you read... especially not from SCC. Not that they're totally non-credible, but they're just commonly mistaken.

04-17-2002, 04:50 PM	#7
Revision Scooby Guru Member#: 242 Join Date: Sep 1999 Chapter/Region: MWSOC Location: Carol Stream, IL USA Vehicle: MY05 PSM GGA !STOCK MY99 RS-RIP / MY95 MX-5	Actually, nothing on that Y-Pipe is cast.. The main collectors are bits of tubing welded togther and the final section on the Y is also two bits of tubing, one welded inside of the other. I take that back, I believe the flanges to be cast. As for 8Complex, can you say 3 engines a tranny and currently a body kit.

04-18-2002, 03:11 PM	#10
8Complex Moderator Member#: 922 Join Date: Feb 2000 Chapter/Region: MWSOC Location: Schaumburg, IL Vehicle: 04 FXT Red	The most common problem is detonating and taking a chunk out of the crown of the #4 piston. It's the furthest from the FPR so the theory goes that it doesn't get enough fuel and therefore runs hotter and is much more prone to detonation. The other major failure is stripping second gear, though it happens NA as well, just have to beat on it harder.