BIR1, Rolling road.
Turbo Mini Forums

Today I was on a RR in Norway. I've had big problems with the car popping and banging recently. THe RR-operator changed the coil, and all was well.. almost.

He then ran it on the RR a couple of times on 14psi and it refused to run over 5100rpm. Fuel starvation! This guy uses a set of rollers that starts in fourth, and SLOWLY increase speed to maximum rpm. It takes 30-40 seconds at a guess. What he believed happened was that there is something limiting in the carb. The fuel pressure stayed perfect 18psi all the way.
It was less than 1 on the lambda scale.

It did infact run leanish all the way from 3000rpm when on boost.

On four Psi it's OK, but four Psi is boring!

Question one: Why does it lean out when on boost for a long time in fourth? If accelerating it will do 7000 in fourth I guess. But not on a long hill. It'd just die.

Question two: The rollers you guys are using, are they of this "long time" variety, or a fast one?

As far as I know, the engine ran 20psi earlier and got 165bhp at Baldwins at 14psi.

My car produced a little over 100hp today, and 185Nm. I know these rollers are not very "kind", but still 100hp at 14psi is WRONG.

Anyone??

Fucking Mini!

Could be the little filter in the float valve in the carb blocked with it being stood?

In answer to question 1, don't confuse pressure and flow. You may still be getting 18psi as your gauge says, but at the high engine speed, insufficient flow. Try lager fuel lines maybe? Or maybe the pump is deterioating with age? It has been mentioned before on here as well to increase the size of the driiling in the needle valve to help flow.

Question 2, I have personally used rollers that use the fourth gear "run" up method before, they seem to give results on par with what I was expecting for the car in question. The ones I used also have a run down facility to measure transmission drag and hence try to calculate power back to the flywheel.

i get that popping and banging occasionally, i thought it was the coil and then i went megajolt

the thing im thinking is it could be the spark plugs getting old, i will change them this weekend and try again

however it does come on in 3rd for me so my other thought is fueling, ill attack the other thing if that doesnt sort it

what needle are you using, it may be just a need of reprofiling, this is when a good operater can find the problem and who under stands a series turbo motors.

also 2 thiner oil will or lack of it will cause lean out under boost at low revs under full boost and load.

im running standard flow fuel pipe with 8mm micro bore return with a ford focus filter after the pump with no problems.

always looking for them bigger bunches of bannanas

the slow up method is better to get a "real" power reading...

the flash method usually gets done as it ups the power very slightly.... ie its a less fair test.

Alex

AlexF

Pressure may well have been fine, but flow not necessarily sufficient to keep up with engine even though pressure is OK.

I know, but I cannot seee how this should alter. Is there an easy way to see what the flow of the pump is? it's not easy to measure is it?

Is the balance pipe blocked off? I'd have thought that 'slow' approach on the RR wouldn't favout the balance pipe being connected...

Only way I can see of measuring flow is to pressurise regulator from some external source so that the pump is supply fuel at pressure, and then measure an amount over a time period.......not easy though.

Have you checked for damage to fuel lines e.g. dent/crimp in a solid line? I had a problem with a previous mini, it turned out that the monkeys at the tyre shop had somehow crushed a solid fuel line underneath when it went for new rubber.

The balance pipe on the carb is definately blocked off.

I have NOT checked the car's fuel lines unfortunately. I've been thinking of this myself though.

Time to buy a Lambda I guess, and start testing.

What could go wrong between the fuel inlet and needle? I do not have m uch experience with the Hif carbs as all Mini's sold in Norway were Hs fitted.

Is it possible that your bi metal jet holder leans the mixture ? Do you have filter between carb and regulator ? This caused me a lot of grief years ago. What about ignition advance setting ? Are you running std plenum with the internal restriction intact? I have seen excessive advance prevent an engine rev higher and the damn thing did not even pink. That does not explain the lean mixture, though.

165 hp at 14 psi from a 1275 or 1293 sounds a bit too much, I would expect a figure of 135-140 be closer to the mark. Anyway, your engine runs lean and that holds back the power. What are your fuel line sizes ?

Lambda is not the best possible tool if you are running on the road and try to keep the revs high in high gear. I did not know that you have that long straights in the land of fjords...

If it runs great in lower gears but lacks punch in high gear it sounds like fuel starvation, it?s either the pump or restriction is the system.

Dent in the return line should cause excessive fuel pressure, dent in the feed line restricts the flow.

HIF is a simple piece, if it has previously run OK there is only dirt that can cause problems.

The 165 hp was at P Balwinds which is known to read high, so you are completely correct Jukka.

The only thing I've fitted, is a take off for the fuel pressure gauge. This is fitted between the regulator and carb. I removed this and showed it to the RR-operator, and he said that this was not "enough" to restrict the flow to the carb.

Ignition was set by the RR operator. I cannot really comment on what it is at present.

It does rev to 7000 in the first gears.

I was also told about this bi metal jet holder. As I've mentioned earlier, I'm not that good with Hif-carbs. Could someone show me a picture of this? I'll try to remove the fuel pressure gauge, as I now know that pressure is there, but not flow.

We do have a couple of straights over here :)

Thanks!

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=311

Pic no longer show but some good info here.

Edited by T3Tone on 20th Sep, 2005.

-MINI CLUBMAN 1380 TURBO-

Vegard,
Do you suspect the carb has ever been rebuilt? If not, maybe you should consider this whilst modding the bi-met jet holder. The HIF is a very simple carb - admittedly more complex than the HS, but if you can rebuild a tranny, a carb will be VERY easy for you!

Another thing to consider, even at full chat, an A-series turbo engine doesn't consume that much fuel really... Remember where the fuel is coming out of - that tiny hole in the jet!

Personally - I'd be rigging up a few gauges at the same time (including a lambda) and repeating the runs.

* One gague between the carb and regulator.

*One gauge measuring from the float chamber (the pipe already blocked off - the one that used to be the anti-run on valve pipe).

*One gauge at the inlet to the fuel pressure regulator.

*Lambda


More thoughts:
I know BIR1 used to have a vauxhall EFI fuel pump. This has caused a regulator to expire at least once before as i recall. Has it got a restrictor fitted before the regulator?

Take the regulator apart and look at the diaphram - it should be taut, not rippled. IF it is, new ones are available from FSE I recall.

Check the plenum hasn't been messed with.

Dave. You mention a restrictor before the regulator? I seem to recall some talk about theis previously. Is it just an issue of fitting a piece of pipe between the fuel pump and inlet of the pressure regulator?

Crap, I'll have to go out and measure everything now :)

If you have 8mm pipes everywhere, just get a short piece of 8mm steel bar, drill a 5mm holethrough it, and ram it inside the rubber hose just before regulator inlet.


However - I don't think this is the true answer to your problem.

No, I don't think so either. But if this hasn't been done, I could..

I'll rebuild the carb soon along with the change of head.

you havent rebuilt the carb yet??? you ARE lazy :)

I had a very similar problem, it just seemed to run out of fuel in fourth gear. On the track it was fine in 1st, 2nd and 3rd.

After fannying around with loads of things, including the carb jet and pressure regulators, it turned out to be the pump.

The float bowl was actually being emptied because the pump just couldn't supply the fuel.

It was flowing around 1/2 litre/min, and it needs more like 1 litre/min.

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

I'm using a wally 255 for 2006- and just like peter, will be running it from the battery direct, and through a resistor pack for sub 5psi running...

Why are you using such a big pump ????

why are you guys using a resistor pack, is it just to prolong the life of the pump?

Team Racing

Fuck injectors guys, this is BIR1! :)

A picture of the carb upon rebuilding:



This didn't help fuelling in top, that's for sure!

Edited by Vegard on 19th Apr, 2006.