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Re: [turbobike] jet kit for turbo carbs

Christer Johansson (christer.johansson@mbox383.swipnet.se)
Wed, 14 Apr 1999 23:04:19 +0200

Hello George
I did send a mail about 3 days agoo to this list ,but it seems
to have vanished!
Thereīs no secrets in tuning CV carbs for turbo ,just laws of physics.
You have to pressurize them right, I have a 1/2 inch hose routed from
the pressure pipe (after the intercooler) to the carbs ,connects beneath
the membranes ,thus eqalizing the pressure in the carbs and the boost.
I also have a thin line routed from the pressure pipe to the vent pipes
on the bowls, this "line" protrudes into the pressure pipe (about halfways)

facing against incoming air, thus giving dynamic pressure.
Sort of "force feeding" the main jets. I used 162,5 main jets on the old
But it depends on how this pressurizing turn out, wich mains You will need.

I know people that has used 130 mains on 300hp bikes.
I will send You picīs , probably will explain it a bit better.
I also use stock springs and needles. My bike idles just like a stocker,
much better than the Efi bikes I have seen. As longs as Your carbs
are tuned correctly ,there is no advantage in EFI.
Mark Moisan used 36mm CVīs on his 429hp GSXR.
The plastic lids on the CVīs can crack if You go wild on the boost (+20psi)

or get a backfire, I have had no problems though.
You asked earlier about the data on My old Garrett T03, it was trim60
A/R ,48 in this size it will support about 270hp . Port the outlet and fit
biggest possible wastegate valve and it support about 290-300hp.
There is no idea to use a bigger A/R as the narrow sector is in the
turbine wheel itself, bigger A/R would only yield more lag.
You could also separate the wastegate and the turbine and run twin
exhaust pipes, this would give even less backpressure.
If You want more power than this You will have to use a bigger turbo
like the T04E, but then you You will have to use a twin flow exhaust
housing ,otherwise there will be to much lag.

Hope this helps / Christer

george kalogeropoulos skrev:

> Now what's the secret behind jetting the stock cv carbs with a turbo?!I
> haven't been able to get some real info on what people are using to do
> this....is it some kind of jet kit?Who makes the heavier
> springs,needles,jets.Everyone is saying that these parts where modified
> to work?Can someone give me some real info about this???This has been
> tormenting me for the last few nights!My friend says don't bother with
> carbs.Christer seems to have this system running really well.Will the
> bike idle properly?
> Thank guys :)
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