Naturally aspirited boxer tuning?
 

I was wondering if anyone has any experience with n/a boxer engines, what can I do with a v9 STi bottom end to get it up to nice spec, which heads/cams..etc?

I'm not expert but the good old N/A route is polish and port + cams. Not sure that a turbo engine is a good start point as the head flow requirements are different to NA engines (exhaust side particularly). Also the compression ratios are totally different.

Have a chat with David at API, but as you have a confusion over STI engines (there was no version 9 and new age sti engines are very confusing due to the several different versions available), plus its severe overkill, and its always best to stick to a similar/same engine.
Do not expect big gains though, you wont get much out of a NA engine power wise.

Tony:)

TEG have built a couple of N/A engines for the road rally guys (as they are no longer allowed turbos).From memory both were 2.5L bottom ends.One had V3 RA heads, ported polished etc and the other had n/a heads with some high lift/long duration cams.We made a ram air type system air box feeding through the turbo bonnet scoop, fitted Simtek ECUs (modded for n/a operation) and made 195 BHP (std cam) and 210 BHP (high lift) on a 10% meth mix.

Steve

210bhp on a n/a. very respectable.

Hit the nail on the head there, you can only use a max of 4 cyl engines now... I swear some of the guys running it are demented.

Do you know what torque they made?

Yeah i'm aware that a higher compression is more favourable, I was thinking of using ported&polished sport heads, high lift cams and getting the block skimmed to increase compression.

Can't exactly remember torque figures (will pull up graphs when I'm back in dyno after New year) but was in the region of 180 - 200 ft lb with quite a nice flat profile from 2500 to 5000 RPM. We used CR around 11.0:1 due to problem getting good fuel on night rallies at the fuel halts.If fuel wasn't an issue I would try 11.5 -12 CR.

Steve