Hesitant when on boost/under load.
Turbo Mini Forums

as above, standard metro turbo setup becoming very hesitant whilst boost is building up, if you keep your foot down it will begin to misfire and sometimes even pop (what i believe to be back through the carb). I have not changed anything when this originally happened, it just started doing it out of the blue. But then! sometimes its completely fine and fucks off into the sunset..

The boost pressure stays put and does not fluctuate etc, so im almost certain that there is no air leaks?
Seems to be alot worse the more i stamp the loud pedal, if i back off to half throttle it feels a tad better

What ive done so far:
rebuilt carburettor, changed turbo, changed HG, checked FPR diaphragm, checked gasket for float bowl pressure hole, done the T-piece trick, blanked off the DV, oil in dashpot (20/50),

So my thoughts are it has to be fuel or timing related, perhaps the vaccuum advance is not working correctly? and the boost is causing this? perhaps its broke the diaphragm in the vac advance?

or am i missing something completely stupid? neither me nor my old man can get our heads around this one, and any help/advice would be appreciated!!

Cheers lads.

Low boosting for now.

Poping back through the carb is almost certainly due to being lean
Try pulling the choke out to get some more fuel in there and if it solves it they you know its fuel

Yes i moved to the darkside

Instagram @jdm_brett

hmm i did try this yesterday, made a slight difference but nothing noticable, i mean it starts hesitating almost as soon as you hear the turbo spooling, obviously the mixture screw wont make any difference will it?

cheers brett

Low boosting for now.

Tryed the 'T' peice trick? Search it on here
maybe the float bowl pressurisation port has got a little blocked

edit
part throttle lean off still fitted?
All kf the pipes leading to the fuel chamber at the bottom of the carb blocked properly?

Edited by Brett on 1st May, 2014.

Yes i moved to the darkside

Instagram @jdm_brett

using the T piece trick still as stated in original post above.

part throttle lean off pipe is fitted yes, worth blocking off?

will carry on fiddling when this pissing weather stops lol soon to be installing megajolt, i think my next thing to get will be an AEM wideband and save all this fart arsing about guessing

Low boosting for now.

Go for the part throttle pipe.

In the 13's at last!.. Just

Checked part throttle pipe nothing wrong there, taken out the intercooler to help narrow down the amount of pipework that could be faulty, still having the same symptoms!

The thing that concernes me most of all is whenever i am having this issue, under boost, all i can hear is a hissing noise, sounds similar to a tyre being inflated, its more audable when the cars under alot of load/the worse it bogs. So obviously this is the cause! it has to be?

Colour of the plugs is perfectly brown compression test (to my amazement) read 150psi across the Board!
20/50 in the dashpot and the carb has been rebuilt less than 1k miles ago. i have also made a proper job of blocking off the Factory overboost valve that i am happy with.

All i have left to do now is to change the Cylinder head for my rebuilt Turbo Phil head, and install megajolt!

Throw some knowledgeable ideas at me please! i dont want to give up on this.

Low boosting for now.

Did you change the part throttle pipe or just inspect it? It can develop cracks/splits that aren't apparent by just looking at, and as it is just a short length of fuel hose it may as well be replaced to eliminate it as a potential source of the problem.

replaced it, blanked it no difference, however i did make some progress, took out all the old dashpot oil and refilled it with halfrauds 20w/50 and it runs a hell of alot better but still not quite 100%

Low boosting for now.