Maestro Turbo not boosting past 3750 rpm

[EVO AL]

Today at the rolling road 496 would not rev past 3750rpm while under load.

Fuel and air seem to be okay as it goes very well till 3750rpm then it just stops like it's hit a wall.

Anyone got any ideas?

[G Force]

Hi It could be that boost pressure has overcome fuel pressure.

You need a 4psi fuel pressure advantage over boost pressure otherwise no fuel will be metered.

Depending on where you are taking a fuel/air sample from will affect the real time reading. i.e. if your sample is from the tail pipe then the delay of the meter reacting might cause you to think fuel/air reading is ok at the time the engine cuts out.

[Mike Brock]

What boost pressure is it running Al?

[E_T_V]

Balance pipe on the carb ok?. Classic symptoms is sudden fuel starvation.
Otherwise what about the crank sensor - what does the igntion timing do at that point. If it changes rapidly then have a look at the crank sensor and possibly make sure the rotor arm isn't loose in the camshaft.

[EVO AL]

Hi It could be that boost pressure has overcome fuel pressure.

You need a 4psi fuel pressure advantage over boost pressure otherwise no fuel will be metered.

Depending on where you are taking a fuel/air sample from will affect the real time reading. i.e. if your sample is from the tail pipe then the delay of the meter reacting might cause you to think fuel/air reading is ok at the time the engine cuts out.

Hi G,

Thanks for that, at first we were only running 8psi boost and it still would not rev past 3750rpm. We adjusted the actuator rod and then held a stable 15psi, but had the same problem.

The carb is standard and the pressure reg has not been adjusted from standard. Is there such a thing as running out of spark so to speak?

Things I want to try this Saturday are different Coil, ECU, Spark plugs. Anything else?

Thanks for your help!

[EVO AL]

Balance pipe on the carb ok?. Classic symptoms is sudden fuel starvation.
Otherwise what about the crank sensor - what does the igntion timing do at that point. If it changes rapidly then have a look at the crank sensor and possibly make sure the rotor arm isn't loose in the camshaft.

Hi Dan,

It's a new bit of pipe, rotor arm and dizzy cap are all new and we had a look at both and they seem fine.

It does not cough or splutter, it just runs out of puff

[E_T_V]

Cam timing ok?

Is the knock sensor ok?

[EVO AL]

We tried a run with the knock sensor unplugged and there was no change. Not too sure what that means.....

[ian drew]

Al, does it happen in any gear? If so then probably not fuel/air related as the load is very different at the same revs in different gears.

Ian

[E_T_V]

We tried a run with the knock sensor unplugged and there was no change. Not too sure what that means.....

Did they have seperate Det cans on it on the run? So long as it isn't detonating unduely then It is probably ok.

Is the power loss gradual or like a brick wall? Any plots to illustrate?

[E_T_V]

Also perhaps worth temporarily at least fitting a fuel pressure gauge to the car input to verify that it is getting enough fuel. What turbo is it running? I assume it'll have spooled by then unless it is a huge one.

[EVO AL]

Did they have seperate Det cans on it on the run? So long as it isn't detonating unduely then It is probably ok.

Is the power loss gradual or like a brick wall? Any plots to illustrate?

Brick wall. :-( No plots.

Also perhaps worth temporarily at least fitting a fuel pressure gauge to the car input to verify that it is getting enough fuel. What turbo is it running? I assume it'll have spooled by then unless it is a huge one.

It's all standard. I don't want to uprate anything till it's working properly in standard trim.

I sounds like its reving higher in 1st and 2nd but it's all over quite quickly in those gears.

Thanks for the help guys!

[ian drew]

Have you tried a different fuel pump? I get exactly these characteristics in my ZT V8, which going by what other people have experienced, is the fuel pump.

Again, a fuel pressure gauge may help here.

Ian

[E_T_V]

If you have a suitable pressure gauge it is simple enough to check the fuel pressure is ok at idle but needs to be on a rolling road to identify it properly under boost.

Something like this gauge
http://www.ebay.co.uk/itm/Fuel-Press...item2a50a78245

But on this kit
http://www.ebay.co.uk/itm/Fuel-Press...id=p5731.m3795

would be ideal. You need to have a fuel pressure 4psi above boost pressure.

You could just get away with the 1 bar gauge setup for standard boost levels, but not so great when you go higher.

It would prove whether it is fuel related anyhow, although I'd expect the AFR's to go extremely lean (even off the chart) if it is running out of fuel under boost.

[Mike Brock]

Spark needs to be a big healthy and blue when you turn engine over. If it is not (like dull yellow for example) could be spark blowout on higher boost?