Thread: UK 10:1 on boost?

Yeah, 10:1 CR is not a problem if tuned right. A lot of modern turbo engines are 10:1 or more.

370 cc imjectors are tiny. We had a an externally gated t25 setup here running 740cc injectors at about 80percent duty cycle at 15psi. Id get 740cc injectors gives you some room to grow, also an n62 maf, how much boost you run is whatever you are comfortbale with. But 15lbs on 93 is pretty safe depending on tune. 10:1 is a better motor, better valves, more aggresive cam, it is a dope engine.

you should be fine with 370s at 4 bar, unless you plan on running e85

10:1 motor is fine, however c2 cams on a t25? Not so fine. Matter fact, horrible idea. Way too much overlap for a turbo that creates high backpressures. You will have problems i dont care how good the tune is if you go with those cams and a t25. Use the 10:1 motor, s4 cams with stock springs and retainers and on 10psi of boost the thing will be a monster. You dont need 740's, 370's on 4 bar or 550's would be fine.

A good tune is key though to prevent problems. But high compression loves boost. That is a fact.

At 200whp I was hitting 85% duty cycle on 370cc injectors. On 520cc STI's I'm hitting 70% at same horsepower. It's not even overly rich either.

i made 263 hp at just over 70% duty cycle on 520cc sti's @ 3bar (stock regulator with walbro - actually slightly above 3bar). VE + 75 dry shot.

So what motor are you gonna run?

high compression boost is king, no need to boost crazy to make same level of power vs lower compression motor.
I purchased muleman's 10.4:1 block, once fully tuned I made 43X hp 32X tq @ 18psi on SC61 on RNN14 Power FC. I built another B13 w/ 9.0:1 and transferred turbo, took me 22psi to realize those numbers. I learned alot from Hondas, especially boosting 11.5:1 motors from K20A-R and F20C motors, even the occassional B20Vtec 11:1 all motor cars switching to boost, tuning is crucial, and it can be done.
Recently Chris Miller tuned one of my friends B Series, which had made 550hp 380tq on 8.8:1 at 26psi, with 10.5:1 at 20 psi we made those numbers, at 26 psi we made 640hp 460tq
My current B13 is 11:1 DE w/ 6765, made 350hp 290tq @ 10psi on AEM EMS 2

9.5:1 is a slow as I would ever go given the chance. I really liked my 10:1 T28 with S4's and AEM EMS. The thing had great mpg, made a ton of power and was reliable as hell.

Brent