intake manifold improvements over the years

awd4ever · 06-01-2004, 04:50 AM

I've searched, but was unable to find any benefits to using an STI intake manifold over a 98rs one for my project. Are there are benefits to having STI manifold (besides the color)?

Thanks

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totoherbs · 06-01-2004, 06:07 AM

No, unless its a ver 8, they are a different design. Side note the ver 8 STis run the same plug in all 4 holes, while the ver 7 with the older manifold runs a hotter plug in number 4...

awd4ever · 06-02-2004, 01:08 AM

i am not sure i follow you.. are you talking about spark plugs? they dont go into intake manifold

Reason i am asking, is i am trying to get the calculations out of the way before I start spending money on parts, and with ~20-22psi planned I want the most volume from intake mani.

Thanks

subiekid · 06-02-2004, 02:24 AM

well an sti intake manidold would give you more room for an intercooler.

will the v8 sti manifold fit onto a set of 98 dohc heads? i dont think they will, but what ever.

totoherbs · 06-02-2004, 01:59 PM

Quote:

Originally posted by awd4ever
i am not sure i follow you.. are you talking about spark plugs? they dont go into intake manifold

Reason i am asking, is i am trying to get the calculations out of the way before I start spending money on parts, and with ~20-22psi planned I want the most volume from intake mani.

Thanks

Get a worked manifold...

I was talking about the plugs... number 4 runs hotter then the other cylinders. And some belive its becase of the old manifold.

subiekid · 06-02-2004, 07:26 PM

so does the v 8 sti manifold fit into a set of dohc heads?

totoherbs · 06-02-2004, 07:38 PM

Quote:

Originally posted by subiekid
so does the v 8 sti manifold fit into a set of dohc heads?

DOHC heads, well the sti has DOHC heads... I dont know how different they are vs the older DOHC heads. Other then the AVCS...

subiekid · 06-02-2004, 09:49 PM

Hmm, I always thought the new intake manifolds for the wrx/sti would not fit onto the older DOHC heads. I might have to do some research.

Matt Monson · 06-02-2004, 10:42 PM

I have it from a pretty good source that the USDM '98 DOHC EJ25 heads use the same cores as the '97-99 JDM EJ20K's. They are a big bore with different cams, springs and valves. I can't tell you if they used the same manifold or not, but it wouldn't make much sense to make a new manifold for old cores.

I have also been told that EJ207 manifolds do not line up correctly to EJ20K heads, so a V7 or V8 manifold would likely not fit. But the fact of the matter is that on a FI build, the stock manifold is not going to be a major restriction and doesn't neeed any time or money spent trying to figure out a solution for running 20-25psi...

no-coast-punk · 06-03-2004, 10:13 PM

Extrude honing your existing manifold is really the way to go. Plus with the older manifolds you don't have to deal with all that TGV crap.

Drac9 · 06-03-2004, 10:53 PM

I thought I remembered cobb doing some flow bench stuff on the old manifolds and saying that modifying the manifold is not really worth it for the minimal power gains. I also seem to remember something about the unequal length of the runners causing different cfm's at each runner making certain cyliners run hotter. Maybe a custom equal length runner manifold is in order- but not for 20 psi. YOu should be fine with the stock manifold at those boost levels.

Matt Monson · 06-04-2004, 06:41 PM

Quote:

Originally posted by Drac9
I thought I remembered cobb doing some flow bench stuff on the old manifolds and saying that modifying the manifold is not really worth it for the minimal power gains.

I spoke with Josh at Cobb about this last weekend regarding my NA build and that is exactly what he said. He said that when they cut a manifold to access all parts of the runners during porting and then re-welded it together they saw about a 3% gain in flow. Not worth the effort in my mind, especially on a boosted build...

THAWA · 06-05-2004, 12:25 AM

Quote:

Originally posted by totoherbs
Get a worked manifold...

I was talking about the plugs... number 4 runs hotter then the other cylinders. And some belive its becase of the old manifold.

I thought it was fuel related, what with the rails being parallel and all that.

ExecNav · 06-05-2004, 12:38 AM

I think you're referring to series. The third cylinder is last in the series configuration. Parallel is what you want in ragards to fuel distribution.

-Brett

awd4ever · 06-06-2004, 08:22 PM

thank you guys, this info has been really helpfull. And it goes in line with what local shops told me.

Wedge · 06-07-2004, 03:35 PM

I wanna see someone get the 04 2.5 RS/TS manifold and take some intake temp readings.....it's GOTTA be colder since it is plastic!

I'd be REALLY interested in the comparison results.

Drac9 · 06-07-2004, 04:07 PM

One thing that does help these manifolds a lot is phenolic spacers. Cuts manifolds temps a lot.

06-01-2004, 04:50 AM	#1
awd4ever Scooby Specialist Member#: 31573 Join Date: Jan 2003 Chapter/Region: NWIC Location: land of kirk Vehicle: I found the meaning of life!	intake manifold improvements over the years I've searched, but was unable to find any benefits to using an STI intake manifold over a 98rs one for my project. Are there are benefits to having STI manifold (besides the color)? Thanks * Registered users of the site do not see these ads.

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06-01-2004, 06:07 AM	#2
totoherbs Scooby Guru Member#: 7321 Join Date: Jun 2001 Chapter/Region: NESIC Location: waltham, ma Vehicle: .... 122 IggPoints Work... ahhh... so tired.	No, unless its a ver 8, they are a different design. Side note the ver 8 STis run the same plug in all 4 holes, while the ver 7 with the older manifold runs a hotter plug in number 4...

06-02-2004, 01:08 AM	#3
awd4ever Scooby Specialist Member#: 31573 Join Date: Jan 2003 Chapter/Region: NWIC Location: land of kirk Vehicle: I found the meaning of life!	i am not sure i follow you.. are you talking about spark plugs? they dont go into intake manifold Reason i am asking, is i am trying to get the calculations out of the way before I start spending money on parts, and with ~20-22psi planned I want the most volume from intake mani. Thanks

06-02-2004, 02:24 AM	#4
subiekid Scooby Guru Member#: 25516 Join Date: Oct 2002 Chapter/Region: NWIC Location: Send help, stuck in internet! Vehicle: 1995 Legacy TURBO!!! EJ22T/TEC3 & 06 MCS	well an sti intake manidold would give you more room for an intercooler. will the v8 sti manifold fit onto a set of 98 dohc heads? i dont think they will, but what ever.

06-02-2004, 07:26 PM	#6
subiekid Scooby Guru Member#: 25516 Join Date: Oct 2002 Chapter/Region: NWIC Location: Send help, stuck in internet! Vehicle: 1995 Legacy TURBO!!! EJ22T/TEC3 & 06 MCS	so does the v 8 sti manifold fit into a set of dohc heads?

06-02-2004, 09:49 PM	#8
subiekid Scooby Guru Member#: 25516 Join Date: Oct 2002 Chapter/Region: NWIC Location: Send help, stuck in internet! Vehicle: 1995 Legacy TURBO!!! EJ22T/TEC3 & 06 MCS	Hmm, I always thought the new intake manifolds for the wrx/sti would not fit onto the older DOHC heads. I might have to do some research.

06-02-2004, 10:42 PM	#9
Matt Monson Scooby Guru Member#: 832 Join Date: Jan 2000 Chapter/Region: RMIC Location: Teh Ghetto Garage, CO Vehicle: 99 2.5RS, '85 911 '73 914 and 2012 BRZ	I have it from a pretty good source that the USDM '98 DOHC EJ25 heads use the same cores as the '97-99 JDM EJ20K's. They are a big bore with different cams, springs and valves. I can't tell you if they used the same manifold or not, but it wouldn't make much sense to make a new manifold for old cores. I have also been told that EJ207 manifolds do not line up correctly to EJ20K heads, so a V7 or V8 manifold would likely not fit. But the fact of the matter is that on a FI build, the stock manifold is not going to be a major restriction and doesn't neeed any time or money spent trying to figure out a solution for running 20-25psi...

06-03-2004, 10:13 PM	#10
no-coast-punk Scooby Specialist Member#: 49087 Join Date: Nov 2003 Chapter/Region: RMIC Location: Inside your carnot cycle Vehicle: 1998 RST V8 STi swap '05 R6 '95 BMW V8 hotness	Extrude honing your existing manifold is really the way to go. Plus with the older manifolds you don't have to deal with all that TGV crap.

06-03-2004, 10:53 PM	#11
Drac9 Scooby Specialist Member#: 9861 Join Date: Sep 2001 Chapter/Region: RMIC Location: Colorado Springs, CO Vehicle: 1999 2.35 RS-T w/NOS Hybrid Rally Blue Pearl	I thought I remembered cobb doing some flow bench stuff on the old manifolds and saying that modifying the manifold is not really worth it for the minimal power gains. I also seem to remember something about the unequal length of the runners causing different cfm's at each runner making certain cyliners run hotter. Maybe a custom equal length runner manifold is in order- but not for 20 psi. YOu should be fine with the stock manifold at those boost levels.

06-05-2004, 12:38 AM	#14
ExecNav NASIOC Supporter Member#: 30554 Join Date: Nov 2002 Chapter/Region: South East Location: Ellijay, GA Vehicle: 08 LGT Spec.B 01 Impreza RS-T	I think you're referring to series. The third cylinder is last in the series configuration. Parallel is what you want in ragards to fuel distribution. -Brett

06-06-2004, 08:22 PM	#15
awd4ever Scooby Specialist Member#: 31573 Join Date: Jan 2003 Chapter/Region: NWIC Location: land of kirk Vehicle: I found the meaning of life!	thank you guys, this info has been really helpfull. And it goes in line with what local shops told me.

06-07-2004, 03:35 PM	#16
Wedge Scooby Specialist Member#: 2279 Join Date: Sep 2000 Chapter/Region: South East Location: The MIA Vehicle: 2000 Slingshot/99RS Pastelito Racing / SFSOC	I wanna see someone get the 04 2.5 RS/TS manifold and take some intake temp readings.....it's GOTTA be colder since it is plastic! I'd be REALLY interested in the comparison results.

06-07-2004, 04:07 PM	#17
Drac9 Scooby Specialist Member#: 9861 Join Date: Sep 2001 Chapter/Region: RMIC Location: Colorado Springs, CO Vehicle: 1999 2.35 RS-T w/NOS Hybrid Rally Blue Pearl	One thing that does help these manifolds a lot is phenolic spacers. Cuts manifolds temps a lot.