Fuel starvation flat out
Turbo Mini Forums

Wondered if anyone has had this problem and resolved it:

Getting fuel starvation flat out in 4th gear when held open. Obviously its draining the float chamber but how can i sort it, currently running 18psi and has the float chamber extension, larger needle valve, i have upped the base fuel pressure to 6 psi and has made no difference.

Any ideas much appreciated,
Cheers,
oli

Edited by retroracer1380 on 5th Apr, 2010.

there is a high flow needle valve available, and also a float chamber extention.

i have the same issue.. im going to try re-profiling the needle at the WOT position

It has the float extension and high flow needle valve.
Needle has all been reprofiled on the rollers, its only when held flat out say on a straight it runs out of fuel. Is an even bigger needle valve needed? Forgot to say its on a 3 bar mpi pump

Edited by retroracer1380 on 5th Apr, 2010.

If it's emptying the float bowl then you need a pump that pumps more fuel / min, not more pressure.

If you still have the standard feed out of the tank it may be restricting the flow rate.

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

Its got an MPI standard pump fitted in an SPI tank.

What HP? You may have reached the flow limit of the MPi pump, it was never designed to suport 200hp, lol

Edited by Sprocket on 5th Apr, 2010.

Its not 200horse, not had a power figure from it, prob about 150ish at the wheels. Do you think i need to try a different pump?

have you set the float valve correctly?

Got to be honest ive never really thought to check that, how do you set them?

Its in the haynes manual if you have a copy

A straight edge and feeler gauges are all thats needed

cheers will get the carb off tomorow and have a bit of a more indepth look

What size is the needle valve ? Cross drilling the body can assist fuel flow into the reservoir.

And as far as float chamber extensions go. Unless they also extend the jet tube to the bottom of the new depth, they are a waste of time.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Oli.

Whilst you have the carb off, its also worth checking you dont have any crap in the plastic gauze filter Rover decided to fit in the float bowl (you could try removing this and fitting an in-line filter between the FPR and carb).

If it's blocked, it could be exacerbating the issue.

The only thing the bowl extension has done for me is to prolong the time it takes for the fuel to boil in the bottom of the carb when the engine is shut down and my perc fan is off !

IMO, there's probably more work to do on the bottom 1/4 inch of the needle profile.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

hi oli,
if your running a thick oil in the dashpot , it can mean that for a while, eg on the rollers , it runs rich enough ,but then the piston creeps up after a while and it leans off ,try a thinner oil ?

if its then lean all the time ,you need a thinner needle at that point .provided you have fuel pressure there ..

thats another thing to check is the pressure being maintained at 3 to 4 psi above boost , so you should have around 22 psi pressure .

pump wize ..if you take you fuel feed off the carb ,stick it in a bucket ,then apply 18 psi to the fpr boost feed ,you can see how much it flows ,1.5 litres a minute i vaguely remember should be enough ,check that though lol.!


a good way to see if you have enough flow through the needle and filter in the carb , is to pull the choke on , if there a empty float bowl ,youll get little enrichment ... this saves having to take it all apart .

the float bowl extension is not a solution for a bad flow ,just a delay .


im running the needle from the su kit ,whick actually turned out to be bigger than the avonbar one ,and didnt leak like the 3 different avonbar ones i tried did , it appears to be fine up to 190 bhp .

another point is , if your intercooled , the efect of this is increased with speed ,so at high speed your getting a denser mass of air ,but the same amount of fuel ,so it goes lean ,if the rr had no air flow to the ic , it wont mimic this pattern .

hope that helps ,
regards
robert

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Great stuff that gives me some ideas to have a look at later today, will try the choke idea before i take it apart,
Cheers all, will let you know how i get on

Right just tested the pump and mocking 18 psi up with the air line and a regulator im getting 2.6 litres per minute, so i dont think it can the pump thats the problem.

Il take the carb off and have a look next

Do you still have the bi-metallic strip holding the jet?

No ive got rid of the metalic strip jet holder

Had a chance to have a play agian with it today, i have had the carb off, needle valve orifice is 2.9mm diameter, i have taken the littl pre needle valve filter out, it was clean so i left it out and tried it again, thinking it might be obstructing the flow. It might have gone slightly longer flat out, but still ran out of fuel and coughed and spluttered.

I cant see it being the needle profile because is doesnt show up lean on the rollers, and lasts a while flat out before hitting fuel stravation. It does exactly the same on the rollers as on the road.

What are the MPI pumps capable of, and what is and what is an alternative pump to rig up to see if is the pump thats not man enough?

ANy thought much apreciated,
Cheers

itseeither the pump or proberly the fuel pickup from the tank to the pump.

i used a standard 7.5 gallon tank with standard outlet but used the t piece method between the tank and pump and works very well, as this way the fuel coming out of the tank is what the enine is using, if you fit a reurn to the tank then you need to fit a bigger out let from the tank as i needs to supply what the engine is using plus what the rurn rate is.

i can run upto 18psi at the mo at 184 bhp with no probs to date oif running out of fuel i also have fitted a ford focus inline fuel filetr from pressure side of pump which works well

always looking for them bigger bunches of bannanas

Cheers for the help, so id need to revert back to a standard tank and external pump too try this then im guessing? No way of rigging it up with the mpi tank, unless i cud some how extend the return into the bottom of the tank, to use as as an open feed pipe, to link to an external pump.

I'm sure I saw a post about putting a civic pump in a standard mpi tank. I think it links to a 16v mini club page. From memory that gave more fuel than the mpi pump

Ah cheers will have a look on that

did you try the float level settings. I had the exact same problem, hit a brick wall if acc hard at 80mph... I remember setting it in the paddock of Olton park, was perfectly fine afterwards and pulled up to the limiter.