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DISCUSSION => Swaps, Turbos, Buildups => Topic started by: littleboyblues on February 22, 2009, 07:04:38 PM

Title: Turbo Friendly?
Post by: littleboyblues on February 22, 2009, 07:04:38 PM: Turbos generally like lowish compressions and the m42 has 10:1 which is kinda high. I know you can change the crank to lower the compression but i'm just wondering if m42's respond nicely to being turboed.

Thanks
Title: Turbo Friendly?
Post by: JoeDellio on February 22, 2009, 08:47:38 PM: Quote from: littleboyblues;67031
Turbos generally like lowish compressions and the m42 has 10:1 which is kinda high. I know you can change the crank to lower the compression but i'm just wondering if m42's respond nicely to being turboed.

Thanks

I dont know what these engines can handle stock, but I can tell you I wouldnt want to find out, higher compression will yield more HP in the long run but wont be forgiving on the tune. You have to have a good tuner bottomline in any FI application to be reliable and make the most power out of what you got.
Title: Turbo Friendly?
Post by: littleboyblues on February 23, 2009, 02:57:06 PM: wouldn't a FI tune be more difficult than a higher compression one?
Title: Turbo Friendly?
Post by: Danny707 on February 23, 2009, 03:43:52 PM: An FI tune is harder on a higher compression motor.
Title: Turbo Friendly?
Post by: littleboyblues on February 23, 2009, 04:20:09 PM: That makes sence that a higher compression FI would yeild more than a low compression one but would be harder to tune. So you would go with the lower compression. Doesnt this sort of take away its rev happiness b/c you are stroking it. I assume thats how most people get a lower compression.
Title: Turbo Friendly?
Post by: bearsbmw on February 23, 2009, 05:09:38 PM: M42 are turbo friendly on stock interals up to 12 psi and m44 are friendly at 10psi... some choose to run slightly higher but I don't think it's a good idea
Title: Turbo Friendly?
Post by: littleboyblues on February 23, 2009, 05:18:37 PM: Thanks. That clears things up a lot. I just sort of had this impression that everybody had to alter their compression inorder to turbo it. Guess not:)
Title: Turbo Friendly?
Post by: Deyan on February 24, 2009, 07:47:01 AM: If you use higher octane fuel and I am not sure, but some colder sparking plugs, you could run on 10-12 psi. But at the end it depends how you tune your car (A/F mixure, ignition). A friend of mine run M40B16 on 12 psi without problems and the engine blew on 18-20 psi :D and he told me, that 10 psi is like a friendly boost.