20g vs 25d intake manifold

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91Legacyresto
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20g vs 25d intake manifold

Post by 91Legacyresto »

Just wondering if anyone knows how well the 20g intake manifold flows compared to the 25d manifold??? My current setup is a 22e/25d hybrid, yellow top injectors, vf48 turbo, speedyefi standalone ecu, and ive got her tuned on 16psi right now. Just wondering if i would gain any benefits from the 20g manifold over the 25d. Boost comes on quickly, but i seem to loose boost gradually about 2-2.5psi from 5500-7000rpm where i have my redline set. I normally shift at 6500...but for those occasional street runs, the extra 500rpm makes a big difference between shifts Image

Any input from those that have experience with both or either one would be appreciated Image ImageImage

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Legacy777
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Re: 20g vs 25d intake manifold

Post by Legacy777 »

I unfortunately don't have any direct experience.

However, any chance you have a 25d and 20g intake manifold you could setup a flow test with? You could use a shop vac with the hose on the exhaust end and hook it up to the throttle body. You'd need to setup a manometer of some sorts with tubing and liquid to measure the pressure drop from the throttle body to the outlet of the intake runners.

Out of curiosity, how are you controlling your boost, MBC, EBC?
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
91Legacyresto
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Posts: 52
Joined: Sun Feb 24, 2019 6:16 am

Re: 20g vs 25d intake manifold

Post by 91Legacyresto »

Thats an idea i might have to actually try out. I just found out yesterday its actually a 20k heads and manifold my buddy has in his hands. Im trying to convince him to let me buy it them lmao.

Otherwise in the mean time. It looks like JUN is the only company making 20k cams which should fit the 25d heads if im not mistaken. I was gunna try to take valve spring/seat/retainer/lock measurements and find a set to upgrade on the 25d heads to raise its rpm limit. As well try to convert to shimless buckets. Oem 20k parts are hard to find and come by at all. Then to top it all off i want to pnp the intake manifold.

Im controlling my boost through a Grimmspeed MBC. Little thing works great too. I didnt want a super cheap ebay mbc and so far im happy with the Grimmspeed unit.

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Legacy777
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Re: 20g vs 25d intake manifold

Post by Legacy777 »

Keep us posted if you decide to do some testing.

If you're losing boost towards redline when load is increasing have you considered it could be your turbo running out of air to maintain pressure? Have you looked at the compressor map for that turbo to see where you're running on it?
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
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