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Old 01-15-2009, 08:30 PM   #1
OB2
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Default 2.5i or Cosworth manifold???

To begin I do have a GC8 RSTI with a EJ257 forged engine and a rotated GT30R turbo kit!

At the end of the last summer my frend totaled is 05 2.5I and give me is intake for free! I plan to install it on my engine to find the last bit of HP and TQ I can find on my engine!

But last week I find that Cosworth have made wonderful cast intake that I can buy here in Quebec Canada for 1500$CAD!!!

THE QUESTION IS: will it worth the 1500$ to install the Cosworth intake or do you think the FREE 2.5i intake will do a good job the help me to find a bit more HP and the most important of all, allot more TQ???

Please help me to make my choise???
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Old 01-15-2009, 08:43 PM   #2
TDagen
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interesting...
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Old 01-15-2009, 08:51 PM   #3
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Cosworth Manifold for my HTA86 STI swapped 98rs.
Its designed to make power. The 2.5i just happens to "work".

Junior
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Old 01-15-2009, 09:10 PM   #4
TDagen
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There it is^
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Old 01-15-2009, 09:22 PM   #5
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I want cosworth. Junior have you tested it yet?
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Old 01-15-2009, 10:31 PM   #6
Mycues1982
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Yea but is it really worth $1000? I think the 2.5i manifold is better designed for a FMIC application givin that the runners are directed out the rear. Since the Cosworth looks to have been designed for a universal application it still uses the same brick wall design but with a larger plenum. It would be nice to see what the cosworth looks like on the inside though. Maybe the runners are designed better then I assume.
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Old 01-15-2009, 11:35 PM   #7
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From the info that I gather...when XX tuning was selling n/a manifolds...there was more than just slapping the manifold on and it works...there was port done as well and some modification.

I would love to see the new cosi and a n/a mani back to back test!
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Old 01-15-2009, 11:43 PM   #8
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Yea there will need to be some modification to use the 2.5i manifold, I think mostly to get fuel rails to work. I havn't researched it much but I think some custom hold down brackets might be needed. You will also need a TB adapter if your running anything but the DBW tb. I have 2 of them here and plan on doing some testing with them over the summer to help me determine a design for an intake manifold I'd like to produce myself.
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Old 01-16-2009, 01:19 AM   #9
watchunglava
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why not just get the free one and have it port and polished for like a 1/4 of the price?
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Old 01-16-2009, 11:51 AM   #10
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Well you can't really port the 2.5i, you could sand and polish the runners some though. The flange section already matches up to the cylinder heads and gaskets perfectly.
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Old 01-16-2009, 07:34 PM   #11
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I have already done the 2.5i intake manifold on my ej257. I took wrx TGV's and had them ported and welded the ends shut. Then I had the manifold cut where the tgv's should be and had the wrx units welded on and portmatched on the insides. This gives you all the fuel rail options in the world and only cost me about $250 total. My car should be done in the next two weeks. Curious to see what it can do on a 35R car(mine).
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Old 01-16-2009, 07:40 PM   #12
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Still waiting for my cosworth to come in, ordered it a month ago, looking forward to how its going to hopefully better my numbers on the cosworth longblock !!
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Old 01-19-2009, 03:04 PM   #13
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Thanks for the info, and keep me informed on the 2.5I and the Cosworth intake!!
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Old 01-29-2009, 02:26 PM   #14
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TOOOOP....

Nobody use 2.5I intake manifold...........want more info about it???
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Old 01-29-2009, 03:51 PM   #15
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I think Phil from Element reported having using it on his time attack car, and did mention about the need to increase fueling at the top end after it went on, which was a sign that it was making more power than usual
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Old 02-02-2009, 08:36 AM   #16
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Comunication witht Me vs Phil Grabow:

Phil :

Yes I run that manifold but it requires custom plenum spacers (about 15mm), grinding, different fuel rail spacing, and welding closed some things. The 05 Legacy NA has the same upper (you use your TGV housings) so this is a much easier option than going with the unit I did.

Unfortunately I didn't document the before and after results on the dyno since I had no time before my race. When I tuned the map I could tell by how much more fuel I had to add that I had a sustantial gain around 5500-6500 rpm but there was more lag.

Thanks,

Phil Grabow
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Old 02-02-2009, 09:04 AM   #17
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I like the Cosworth manifold, just unfortunately doesn't come with long intake runners.
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Old 02-02-2009, 11:12 AM   #18
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Quote:
Originally Posted by 9vapors View Post
I like the Cosworth manifold, just unfortunately doesn't come with long intake runners.
long intake runners are for na cars iirc, short runners are for turbo cars
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Old 02-02-2009, 11:41 AM   #19
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not 100% true. Long runners still help with velocity issues, but has other drawbacks with turbo cars.
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Old 02-03-2009, 12:01 AM   #20
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What drawbacks would there be???
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Old 02-03-2009, 12:45 PM   #21
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What I meant to say was that unlike the V8 manifold, you need to run TGVs with the Cosworth, it doesn't come with the deletes...
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Old 02-04-2009, 07:41 AM   #22
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Quote:
Originally Posted by 9vapors View Post
What I meant to say was that unlike the V8 manifold, you need to run TGVs with the Cosworth, it doesn't come with the deletes...
Oh I see what you mean
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Old 02-04-2009, 11:18 AM   #23
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All street motors are na till the boost comes up. How can long runners be a concern under boost. It seems long runners only add intake volume to me.
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