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Dual progressive throtle bodies

Dual progressive throtle bodies

Dual progressive throtle bodies

(OP)
Hey guys. I'm building a Mitsu Starion engine (2.7Lturbo) w/ about 550hp (maybe more in the future) in mind. I don't wanna go with too large of a throttle body b/c this is for street driving and at the same time I don't wanna choke off my top end (prolly a T-72 turbo w/ 18psi; 7500rpm redline; max piston speed = 4800fpm).

A setup I'm looking into is to use two progressive throttle bodies from a vw/audi turbo. Post-intercooler ducting would split right before the TB's and reunite just before the intake manifold (right after the TB's).

The intake manifold, turbo (etc) will be built for 4Krpm+ power so I'm trying to scavenge every bit of 'off-idle' power I can.

Plenum volume = about 80% of displacement (abot 2.15L)
still working on runner length/diam/v stack but will be midway between [short-fat hi-rpm] and [long-thin lo end-torque] size.

Whaddyu guys think about the dual progressive setup?
If not then what size do u recommend? (please give logic/ proof).

Thanks.


And keep up the good work with the info. Some good reading here. *thumbs up*



P.S.
(for anybody who's familiar with these engines: No. I am not gonna use the stock intake manifold/TBI. Custom MPFI manifold so spare me the fuel discussions. Happens everytime I bring up anything to do w/ my car)

RE: Dual progressive throtle bodies

Hey man. Sounds like your gonna have a sweet motor when your all done. Im not familiar with Mitsu but can you tell me what the bore/stroke of your motor? What size connecting rods are u using?

Also I could be wrong but your piston speed is looking alittle on the high side, im guessing your gonna be using some good parts but piston speed kills motors.

Later,

Ryan

RE: Dual progressive throtle bodies

(OP)
Thanks.

The motor has a undersquare bore stroke ratio (like .9:1 bore/stroke).

bore: 3.587" (91.1mm) (gonna bore .040")
stroke: 3.858" (98mm)
(prev mistake: 2.7L was supp to be 2.6L)

Conrods I'm not exactly sure of cause I can't find the factory specs but I used the shortest one I could find aftermarket: 6.527" b/c I don't think any manufacturer in their right mind would make a shorter than stock conrod, esp in this car. It could be longer than stock tho but I figure for safety margin tho I'll calculate with the shortest rod length I see (prolly gonna use some longer aftmrkt rods anyway).

I know those pistons speeds are high but I've spoken w/ a few people who are running those rpms in their motor. I'm hoping to coat the skirts of the pistons and I'll prolly set my rev limiter @ 7000rpm instead of 7.5krpm. Maybe at the drag strip I might put it back to 7.5krpm. I'm also looking into a tranny with longer gears from 3rd up (more top speed, better use of torque, better mpg & less time spent @ 6.5krpms+).

Right now the block is off to a friend of mine for blueprinting/ chamfering/ annealing/ etc and I'm still finalizing my research on rods & pistons but once I finish if u want I can send u the exact specs (with the results of the calculations I used).

Take care

RE: Dual progressive throtle bodies

Ya man that would be great. I’ve never really heard of this motor before so in definitely interested.

Also what’s up with annealing the block? I know annealing is a process of softening a metal, seems something more like a stress relief process would be better? cant say ive heard about that before. Is the block cast iron or Aluminum?

Let me know,

Ryan

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