Mark V8

iTrader: (2)

Just got my turbo bike running on Megasquirt and have unusual (according to the MS website) KPA at idle.

Engine DOHC 20 valve
1043cc
10:1 CR

inlet cam 106.5 deg
exhaust cam 105.5 deg
following instructions here
http://www.turbo-bike.net/Cam%20timing.htm

KPA at idle is around 68

Does this sound right?

thanks for any help

Mark

davidreader5

HI,

With out looking it up as dont use kpa, just bar and psi.
but on idle if i read your question right, you only would have vacuum, and boost
will only show under load,depending on the engine condition vacuum can change
from a good to a worn engine, ask the supplier of the kit what vacuum at idle
on average you should have.

DAVE R.

Mark V8

iTrader: (2)

There is no kit supplier, it's all home built

Around 98 KPA is normal atmospheric pressure, so 68 KPA is 0.68 bar absolute meaning that it still running a vacuum, just not much of one

Mark

davidreader5

HI,
what state of tune is the engin in, oil pressure ,compression etc,
if good and you cant find out off the engine manufacturer i would't worry to much
the cam timing if not std will have some effect on vacuum and idle speed.
i would of been more concerned about the high comprssion ratio,what amount of boost pressure are you using max.and is the engine injection or carb,

DAVE R.

Mark V8

iTrader: (2)

Engine is mint, and is now running on injection after I dumped some troublesome carbs. 10:1CR is not that high for a turbo bike and it is running forged pistons and around 12psi of boost.
I emailed a chap in the US who has done the same conversion and he gets around the same KPA reading at idle so panic over

Mark

JesseT

You didn´t tell your inlet cam duration, but with bike cams I wouldn't be surprised with your idle manifold pressure. Also the rpm where you let it idle affects the pressure hugely. If for some reason you need a lower manifold pressure at idle, then increase the idle by 100-200rpm.