Blackbird fuel pressure regulator question

[Martin Plant]

I wonder if anyone can point me to a fuel pressure regulator that can reliably deliver low pressure (say 0.5 - 1 psi) but with reasonable flow. I have a petrol king in mine at the moment and it is tricky if not impossible to get it to deliver a reasonable flow without overcoming the float valves.

 

On a related theme, anyone know where I can obtain a guage to use with the above (without going to the expense and bother of plumbing one in to the stack.

 

Thanks.

 

PS the above would be for use in my Blackbird c/w Keihin race flat slides.

[DanB]

Martin,

 

Are you using a bike fuel pump? If you are, you don't need the regulator. If you're not, fit one and save yourself the hassle! A lot of people have had difficulty getting a car fuel pump to deliver sufficient flow at low pressures - the engine either gets starved of fuel because there's not enough flow, or the float valves can't take the pressure. A Fireblade fuel pump (about £20 from a scrapper) does the job perfectly.

 

HTH

 

Dan

[J.R.]

Easiest & cheapest way to test the pressure is to run a length of clear tubing vertically from the pump outlet.

 

If it were pumping water then 1 psi would raise the the fluid by 2.307 feet or 27.6" this is ok if you pump water for testing, if you pump fuel then the relative density is lower and it will go proportionately higher.

 

Dont know the relative density of petrol but someone will probably soon post it.

 

This method is also very usefull for testing the ram air intake pressure.

 

Why are you using flat slide carbs? have you been having difficulties with fuelling, jetting, fuel pressuer etc using ram air set up on standard carbs? - if so I have been there myself may be able to help.

 

 

[Martin Plant]

Thanks for the replies.

 

Dan - I'm using a car pump because the car was built by Caterham like that. But thanks for the tip I will certainly see if that is a feasible option. The car has an ATL bag tank that could make a bike pump a bit tricky to fit.

 

J.R. - Thanks for the pipe tip. Good idea. The car has flat slides because it had an uprated engine fitted by the previous owner and I guess that the engine builder (Steve Owen at OMS Racing) decided that was the best bet for maximum power. 1200cc, pistons, rods, cams, head work and the carbs.

 

It had been running fine up until its last trip to the 'ring last year when it failed to start after one session. After much head scratching and blind alleys I've concluded that its flooding caused by too high a fuel pressure.

 

Incidentally I still have the original engine and carbs and sometimes think it would be simpler to swap the lumps over. But I do like the urge from the modified one

[DanB]

Fitting the pump shouldn't be a problem - mine lives in the engine bay, just under the carbs and seems to have no problems sucking petrol from the fuel tank. The pump has simple 8mm push-on fittings and 2 leads for power/earth. They're round and can be easily held in place by a 53mm exhaust clamp.

 

Good luck with the trouble-shooting

 

Dan

[Martin Plant]

Thanks again. I was concerned that my pump might be internal to the tank but it isnt - its mounted behind the passenger. Easy enough to do a straight swap with a 'blade pump.

 

Best I can get a used one for is 40 quid plus VAT and delivery or a new one from a dealer is 125 quid plus VAT. The difference is less than the cost of getting lifted off the 'ring on a public day which is where the car does most of its miles. Presume these things have a finite life like everything else. I'm tempted to get a new one.

 

Cheers

 

Martin