Thoughts on #4 being prone to failure...

Matt Monson · Post by **Matt Monson** » Thu Oct 28, 2004 8:52 pm

I have been running fuel rails on my personal WRX for 2 years now. It solved problems for me back then and they are still offer a big advantage today. The stock rails run an inline configuration which dead ends. Fine for stock power cars but not the best when power is the goal.
Since I tune EFI and have tuned over 350 WRX's to date I have the experience to tell you that the power stops when that one cyl starts to det. Since we dont have the option of individual cyl fuel and timing adjustments with the low cost EFI solutions for the EJ motor, anything we can do to raise that detonation threashold will make and add safety.
I have tested cars with and without rails with multiple EGT probes. I learned what Subaru already knew. #4 cyl flows more air. This is why JDM STI engines came with a different spark plug in #4. This problem was solved with the V8 intake manifold. The older two piece V7 style manifolds had air flow issues which caused more air to hit #4.
Another added benifit of the Perrin fuel rail kit is an increase in total fuel flow. Its typical to see a car enrich a full AFR point with the addition of this fuel rail kit. My own car increased over a full point. Because of this you need some form of engine management to reduce injector pulse widths back to the correct AFR for your application.
What you end up with is a big margin of safety in the form of reduce injector duty cycles, equal fuel flow to all cyls and not to mention they look cool. Its my opinion that anyone building a car that needs larger fuel injectors needs fuel rails

This was written by Clark from Kingpin. As I mentioned in Matt's EJ20G thread, I knew that #4 was the issue, but had always been told it was a fuel delivery issue. According to this, it is more of an extra air issue, but better fuel rails are still the solution...

Post by **Legacy777** » Thu Oct 28, 2004 9:09 pm

Very very interesting.

Since the intake manifold is symetrical other then the IAC valve, I bet that has something to do with #4 getting more air. That or there is some form of standing wave in there

I know nothing about when/what the different version manifolds came on....what model years and what models did they come on in the states, and when did they change?

Matt Monson · Post by **Matt Monson** » Thu Oct 28, 2004 9:14 pm

The change to the maniifold he is talking about is the v8 (2003) Japanese market and later.

Post by **Legacy777** » Thu Oct 28, 2004 9:17 pm

So we never got that manifold here in the states?

Any particular reason why? emissions....soa sucks?

Matt Monson · Post by **Matt Monson** » Thu Oct 28, 2004 9:36 pm

actually, I wouldn't be surprised if it found it's way onto the '05 that are hitting right now. And technically our '04 STI is a v8, so likely has the redesign...

Post by **Legacy777** » Thu Oct 28, 2004 9:47 pm

Physically....what is different between the two version of manifolds?

vrg3 · Post by **vrg3** » Fri Oct 29, 2004 12:39 am

This is interesting.

The redesign may be as simple as a slight bit of restriction on the inside of the runner.

There's also a cooling issue... mile hi mentioned it once. Cylinder 4's head doesn't get as much coolant flow as the others.

THAWA · Post by **THAWA** » Fri Oct 29, 2004 6:36 am

What I don't get, if there's all this stuff about cyl #4 and the engine is pretty much symettrical, why doesn't cyl #1 have these same problems?

vrg3 · Post by **vrg3** » Fri Oct 29, 2004 3:03 pm

The intake manifold isn't symmetrical. The air comes in only on one side, right? The IAC valve's only on one side. The PCV valve is on one corner. The brake booster provides air from another corner. Et cetera...

azn2nr · Post by **azn2nr** » Sat Oct 30, 2004 5:23 am

so can we identify which rails and injector parts are bolt up for our cars to solve this problem. with or without management.

douglas vincent · Post by **douglas vincent** » Sat Oct 30, 2004 6:07 am

I have proven that the #4 piston is prone to detonation in my little 2.2 NA!

93Leg-c · Post by **93Leg-c** » Fri Jan 06, 2006 5:07 pm

Has anyone been successful in remedying this situation? I've already burnt #4 exhaust valve pretty badly in my previous engine and I think I'm developing the same problem with the current engine I've had installed.

The v8 intake will not fit our engines, correct, unless we get v8 heads? Are fuel rails made for our cars--from other threads it seems only the NA rails will fit but if douglas vincent's NA engine burnt exhaust valve #4 then that's not a solution either, is it? What kind of mod can be made to restrict air flow to cylinder #4 by the proper amount? Can anything be done to increase cooling to cylinder #4 (I think the answer to this question is "no," right?)

Should we run a colder plug in cylinder #4? It might help detonation but it still wouldn't solve the underlying issue, would it? But if it will help some, I'll do it.

93Leg-c · Post by **93Leg-c** » Fri Jan 06, 2006 5:14 pm

Now I have another question. If only a few members on the Board have experienced exhaust valve #4 burning, why haven't the other members? For those who have experienced exhaust valve #4 burning, is it because some part is malfunctioning, and if so, which part is it?

vrg3 · Post by **vrg3** » Fri Jan 06, 2006 5:24 pm

Right, the v8 manifold won't fit our heads.

I don't know if any aftermarket rails fit our manifolds, but it can't be that hard to fab up some custom rails, can it? But in any case, better rails aren't going to solve the problem of uneven airflow.

Actually, there was some talk about drilling out a new cooling passage in the back of the driver side cylinder head, allowing more coolant to flow past cylinder 4's combustion chamber rather than just kind of pooling around it.

Maybe a colder plug in #4 would make sense if you're pushing a lot of power -- is that what earlier STis had?

evolutionmovement · Post by **evolutionmovement** » Fri Jan 06, 2006 8:09 pm

All my cylinders were gummed up about the same, so just another factor to add.

I think it is likely a cooling issue as the main culprit. I wonder if a turbo block running N/A and stock compression with its extra cooling line for the turbo would relieve some sort of pocket? Anyone have 15 years to find out? Mine went to 246k so I wouldn't call it a major problem, but definitely a weakness.

Steve

Subtle · Post by **Subtle** » Sat Jan 07, 2006 1:30 am

A couple of months ago I phoned Perrin to see if they had rails to fit the ej22t. Didn't know

Then on this site someone pointed out that the 93-94 NA rails did fit and that they, in turn, would take a wider range of injectors than those for the ej22t.

The question becomes-- will the Perrin fit the 93-94 rails?

If so, they may deliver a more uniform fuel flow to each cylinder, which could diminsh the potential problems of distinctively less air to # 1 .

Any comments

NICO · Post by **NICO** » Sat Jan 07, 2006 3:03 pm

i dont no about you guys but every so often when i stomp on the gas i hear a slight ping for a sec, it all ways comes on the #1 #4 side.

also i have never had any vavles bend brake or burn ever, piston #1 is in stock at my house becuse i dont feel like waitting 3 months from jap. thats the only thing that will brake on my motor when it brakes.

free5ty1e · Post by **free5ty1e** » Sat Jan 07, 2006 3:44 pm

By the "#4 cylinder" are we referring to the last in line for fuel, closest to the firewall on the passenger side of the engine compartment? I thought that was the #3 cylinder. At any rate, that's the one that has lowered compression in both my EJ22t's.

Post by **Legacy777** » Sat Jan 07, 2006 7:49 pm

No....No 4 cylinder is the one on the driver's side back corner.

free5ty1e · Post by **free5ty1e** » Sun Jan 08, 2006 4:37 pm

Huh. OK... #4 cylinder gets greater air flow than the others due to manifold design. It's also first in line for fuel. I guess the Subaru engineers were at least thinking.

555BCTurbo · Post by **555BCTurbo** » Thu Jan 12, 2006 1:56 am

NICO I WRX U wrote: ...piston #1 is in stock at my house becuse i dont feel like waitting 3 months from jap. thats the only thing that will brake on my motor when it brakes.

You just jinxed yourself!

dzx · Post by **dzx** » Thu Jan 12, 2006 4:18 am

I have two turbo legacy pistons, the other two were smashed to tiny bits when a rod let go. Never let a friend drive your car without you in it

professor · Post by **professor** » Thu Jan 12, 2006 5:14 pm

>>>Never let a friend drive your car without you in it

werd

my "friend" drove my BMW coupe and broke the wooden gearshift knob on the back window

slap shifting bastard

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Thoughts on #4 being prone to failure...

Thoughts on #4 being prone to failure...