Tuesday, February 26, 2008 - 02:54 pm, by: Peter Taplin(Mrfourwd)
Hi guys Some comments from an old timer.. Don't guess "test" Check the speed of the pulley at various engine speeds with either a contact tachometer or an optical one. Check the pulley speed under load at 5000rpm full noise. Calculate the projected speed based on pulley sizes, 5% losses are normal anything over that and you have slip. My car used to slip at high RPM from about 3500RPM up to redline at 7500rpm, changing the way the belt was routed solved all the issues with belt slip by increasing wrap. Stock engine all the mods to intake and exhaust it still made 9.5lb boost. New motor, low comp, big cams,ported heads, now it will not boost over 7.6lb... the engines demand for air exceeds the ability of the SC to supply it. The pulley at 2.2 inches on a 32 reaches max rpm for the M90 at 6400rpm taking the losses into account and measured at the pulley under load.
Leaks could be an issue, belt slip sure, but if this engine is stock then it should get close to 10PSI
If the exhaust is restrictive it will give higher boost figures not lower. If the intake is restricted it will lose boost.. this is not likely as the STD soarer box will flow enough air for 10PSI.. check it for restriction with a manometer.. across the air box and TB. If you have to use a belt slip spray you have a mechanical issue that needs addressing. When I had slip I had a small amount of black dust on the SC nose etc.. now with the change to belt route I have no slip and little or no dust. If your belt is popping off it's slipping badly and may be out of line.. Here again don't guess check it.. Your engine is stock, they don't breath well stock and will make close to 10PSI with an M90
If your belt follows this route you are in trouble at that pulley size
Here is the modified route, this belt has done about 35000Kl with no cleaning as you can see there is dust but not a lot for the K's
Tuesday, February 26, 2008 - 06:45 pm, by: Kim Hunt(Lxtasi)
Peter Taplin wrote on Tuesday, February 26, 2008 - 02:54 pm:
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Here is the modified route, this belt has done about 35000Kl with no cleaning as you can see there is dust but not a lot for the K's
mine is really similar to this set up , well the amount of wrap i mean.
with the fuel issue. i have my rising rte fuel reg off the boost side. is that wrong?
i also have a new belt and it doesn't make any dust. the gates belt i used ended up slipping and splitting but i have noticed that with the bosch belt i have no problems. i will try the fuel reg off the manifold side and see what happens. thanks guys
Gary Nimmo TryHard WA V8 Supercharged & intercooled
Tuesday, February 26, 2008 - 07:58 pm, by: Kim Hunt(Lxtasi)
315cc well i does pop a bit at idle but i have fixed the reg now so that it is at 45PSI 50PSI at idle. but i want to know if the fuel reg needs to have a line from the boost side or the vacuum side of the engine?
Gary Nimmo TryHard WA V8 Supercharged & intercooled