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Re: [turbobike] dragracing

christer johansson (christer.johansson@mbox383.swipnet.se)
Thu, 31 Dec 1998 19:46:02 +0100

Hello Ove

Is it a K26 turbo? The kkk`s are very good motorcycle turbos
as they have a bigger turbine housing compared to otherwise
equally sized Garrets ,Mitsu, IHI etc etc.
The mods made to bike turboīs are commonly to port the wastegate
port and install a bigger wastegate valve if the turbo has a integrated
wastegate. Sometimes the turbine wheel are cut in the major diameter
and the fins can be backcutted/undercutted to reduce backpressure
before the turbo. This because bike motors are sensitive to backpressure

as they have much overlap on the cams, and as people want turbos that
spool up qickly and with fast response they use "small" turbos but still

want those big hp. Therefore the turbos are often maximised.
You can also sharpen the wings on the compressor wheel and make
a smoth taper towards the compressor wheel.
I have done all those mods plus some more to My new turbo (Schwitzer).
You are probably right about that intercoolers donīt make much of a
on drag motor ,at least not a air to air type anyway. If You are to run
the bike
only at the drag ,You should consider a liquid cooled version,
preferably with
something else than water as cooling media. As water take to long to
heat up
it wont lead away the heat fast enough.Then there are other materials
aluminum that will lead heat faster/better. You want a intercooler that
can dispose
of heat very rapidly and efficintly and still not be a restrictor, not
the easiest task.
How do You control Your boost settings with the pop off valve ,spring
Where have you placed the priority breather valve?
I will try and make it to Åland the 22 of may then.

best regards / Christer

Ove Osterlund skrev:

> Christer:
> My turbo is a german KKK, taken from an Audi A4 2.2 litre engine.
> I have no idea of the spec. of the turbo, or what model it is.
> I only know that the air intake on the compressor house is 45 mm.
> I donīt use a intercooler, mainly because I donīt have one,
> and the other reason for not using an intercooler is that I donīt
> think it would make so much difference in power output.
> At least not when you only is going to race a 1/8 mile strip.
> I use a blowthrough based system, with a priority breather valve,
> this will allow the engine to suck cold air pass the turbo before
> boost is being build up.
> I don't use a wastegate, I use a blow off valve instead.
> My compression ratio is 9,5:1, I run the bike on
> pump gas. (which were I live is 99 octane)
> Maximum boost that I ran the bike on was 1 bar. (15 psi?)
> Have no idea of the power output though, I havenīt had the
> opportunity to dyno it. I can only say that, when having 1 bar of
> boost, it feels like the arms is going to be ripped off your body!
> I have built my turbo system myself, so I donīt have
> so much experience about turbocharging yet.
> Iīve understand that they usually modify the turbocharger
> for use on motorcycles. What are these mods??
> We are going to have the next race here on Åland at a preliminary
> date set at 22nd May. We always have alot of swedes coming here
> to race. We all talk swedish on Åland so the language is no problem.
> Iīve now protested against running with pro stocks and such,
> so now there might be a little chance of turbo street bikes to
> be allowed to run with other street bikes.
> I mean, they allow stock street bikes to run with bikes
> that have 1427 cc big blocks!!
> /Ove