[Sarra]

Not being very familiar with IM setups, I'm asking this for practical advice.

First question is, can an IM from a WRX or STi fit onto a Phase I DOHC 2.5 liter motor without modification, or are there fitment, bolt pattern, or electronics issues with doing such a swap?

Second, will I lose my boxer rumble, since I'm using an UEL IM, and the WRX/STi IM's are all EL?

Third, would I be able to run a higher rev limit due to the engine having better breathing characteristics in higher RPM range?

I am going to be FI'ing the car in the future, and running a TMIC will probably be stage 1 for me.

Last Q, if there are no fitment issues, what is involved with swapping the intake manifold over anyway? I know that a fuel injector/rail transplant will be necessary as well as moving the TB and a few sensors over.

 

[shifthead]

1: I don't know, I've never done it. Lots of people have, so they'll chime in.

2: No. That's firing order, engine design, and headers that make that happen. I didn't realize that there was a difference in IM's other than that some had better ports than others and were a little wider. I don't think it matters.

3: No. Your head still won't be able to handle that. you need to do springs and valves and stuff to get that higher. It's just like an intake or an exhaust won't give you more RPM's. However, a NOS sticker will.rly:

 

[tnice17]

i say if it bolts up than go for it!... you might have to fab up some bracets or vacuum lines.

 

[Sarra]

1: I don't know, I've never done it. Lots of people have, so they'll chime in.

2: No. That's firing order, engine design, and headers that make that happen. I didn't realize that there was a difference in IM's other than that some had better ports than others and were a little wider. I don't think it matters.

3: No. Your head still won't be able to handle that. you need to do springs and valves and stuff to get that higher. It's just like an intake or an exhaust won't give you more RPM's. However, a NOS sticker will.rly:

I've got a 100% stock exhaust, yet I get a grumble from my intake that sounds like a boxer rumble from a WRX exhaust sorta.

Heads, stock, can handle 8,000 rpm without mods. There is a 1998 LGT on NASIOC spinning 8 grand in Auto X with a custom intake manifold to help it breathe. I believe that the stock DOHC valvetrain can handle 8,250 or so RPM reliably.

 

[tnice17]

does the SOHC and DOHC (wrx) IM have different bold patterns?

 

[2slo4u]

You can't "bolt on" a wrx manifold on the dohc n/a heads unless you go with an older (98 and down) jdm wrx intake. The intake port bolt patterns on the heads are different.

this is a 98 intake gasket:

and a 2002 wrx intake gasket:

 

[Sarra]

Dang, there goes that idea. I think a one off custom intake manifold will be my ticket here, but I'm not paying $1100 for one.

Thanks for a definitive answer on this one.

 

[AcquaCow]

Dang, there goes that idea. I think a one off custom intake manifold will be my ticket here, but I'm not paying $1100 for one.

Thanks for a definitive answer on this one.

I think you may have to go back to the drawing board as well...

Putting a WRX manifold on an N/A block really won't get you anything over just running boost through the RS manifold...folks have been boosting on the RS manifold for years.

The valvetrain really can't deal with a much higher rev limit w/o upgraded valve springs. The valves will float at higher RPMs causing missfires and other fun things.

A higher RPM limit might not gain you anything anyways... once you go FI, especially on the N/A block, you won't be running enough boost to push the power curve that far to the right.

-- Dave

 

[Sarra]

I think you may have to go back to the drawing board as well...

Putting a WRX manifold on an N/A block really won't get you anything over just running boost through the RS manifold...folks have been boosting on the RS manifold for years.

The valvetrain really can't deal with a much higher rev limit w/o upgraded valve springs. The valves will float at higher RPMs causing missfires and other fun things.

A higher RPM limit might not gain you anything anyways... once you go FI, especially on the N/A block, you won't be running enough boost to push the power curve that far to the right.

-- Dave

There's an LGT running an 8,000 rpm rev limit on a totally stock motor, for autoX, no problems at all.

I do plan on doing a total valvetrain upgrade, something capable of running 10k, but I probably won't be spinnning it that high. I am planning on running a rather large turbo, an sti block with forged internals, and an Emanage Ultimate. Right now I'm trying to figure out how to build this thing properly.