Supercharged 450 running out of puff !

[Richard 858]

Since getting a tighter belt sorted for my supercharger I've noticed that when pushing on the motor is starting to cough & splutter a bit at 5,000 rpm +. I'm putting it down to fuel or air starvation or spark when at full chat.

I have a single Pipercross air filter fitted to ACT silicone inlet hose (into larger Bosch AFM), standard fuel pump (but green giant injectors) and Lucas 14 CUX (let's not start that argument again though !)with decent leads & NGK 7 grade plugs.

Was making 415bhp with some belt slip so it seems it's just the extra top end load from a non-slipping supercharger that is causing the issue.

Any ideas welcome. Thanks in advance.

[Richard 858]

At the time of mapping the belt just started to squeal a little when over 5,000 rpm. Gradually got worse after that until I fitted the tighter belt. On reflection I suppose this could be the reason but I'm also beginning to think that the standard fuel pump might well be at it's flow limit (or a bit beyond).

[Richard 858]

I'm only running 6 psi of boost and have the larger C38 supercharger. I'm still inclined to fit an uprated fuel pump and perhaps go for a twin air filter set up to remove another potential restriction, will this madness never end !!!!!!!!!!!!!

[Richard 858]

Thanks for all the advice chaps.

Boost was measured with pressure gauge at Rolling Road session with MA.
Standard fuel regulator is still in place but looks to have been squeezed a little to up the fuel pressure slightly (according to MA).

I will check/adjust as many of these suggestions as I can over the weekend (although I'm not sure the missus has the nerve for a consistent high speed run with voltmeter in hand !) and report back when issue is sorted.

[Richard 858]

Thank you all for suggestions, I'm sure the answer is in there somewhere. Please don't get into argy bargy on my account and Pupp is quite right I do wish to keep the original Lucas set up for the time being. I have a higher flow fuel pump which I will try initially (I have it anyway but it's a long story why I haven't currently got it fitted) and I go through a process of elimination starting cheapest first. The ECU has been remapped by Mark A on a rolling road and I have discussed this latest issue with him, it may need another short session to put right but we'll see.

Thanks again chaps, but please don't fall out with each other, it's really not worth it