If a CF Supercharged car has no trouble making max boost at redline in second and third gear, is there any reason why it should be unable to make max boost in 4th or 5th gear as well?

A slipping belt would be my guess. Or there is pinging and the resultant 'misfires' are taking their toll on boost.

Its not happening to me so far as I know..I was just curious if there was any relationship to gearing and boost production.

Originally posted by paul e
If a CF Supercharged car has no trouble making max boost at redline in second and third gear, is there any reason why it should be unable to make max boost in 4th or 5th gear as well?

Why would it have problems doing the same at any gear, with the same redline, given that it's mechanically driven? So basically I don't see why it would. With a turbo it could matter for several reasons: spool time (for large turbos), load, wastegate leak, etc.

Here's a simple way to prove this... monitor your RPM and HFM... compare when you max out your HFM (the RPM) in first, second and third gears... you will notice that it's maxed out at exactly the same RPM (this is a hunch, please double check). I don't see why any boost would drop off with load/speed.... CF SC's are engine/RPM related. :dunno

Boris

Could it be more load on the engine?, together with the extended time of necessary boost pressure the SC has to supply due to slower rpm build up? maybe the sizing isn't right to begin with... Just guessing...:)

There is a nearly infinitesimal, immesurable diff caused by what is termed 'boost lag', which is a type of lag independent of the speed of the compressor. This is simply the time for the intake tract to become pressurized. It is mostly a function of volume between the FI device outlet and large/fast swings in throttle opening. - Beau

>>together with the extended time of necessary boost pressure the SC has to supply due to slower rpm build up<<

Thats what I was kind of thinking. I have no evidence that this happens. I was only asking, because I note how quickly I can hit 11 psi in second and third, but in fourth, I usually run out of room before I can hit redline, hence, I have to take it on faith that Ill see 11 psi in fourth too. Thats the only reason I asked.

On my supercharged setup with ASA blower, Boost was higher in 5th and 6th gears. Say 1 or 2 psi.

But never lower in higher gears. If your belt is slipping it must also slip in lower gears under load.

Did you have this problems earlier or did it start recently Paul?

Mert

>>Did you have this problems earlier or did it start recently Paul?
<<

No no no...Like I keep saying, I DONT have this problem. I was only curious if it happens....