is this a fuel pump issue, or mapping issue?

supra is BPU. it has a Apexi SAFC. doubel decat,

it does boost too high in 4th 5th & 6th, but under that its ok

anyway, if i pull off normal, and nurse the accelerator in, itl boost all the way out nicely & pull really strong.

however, if i do a drag start, or flat it hard/suddely, it holds back, and will only boost to 0.5b.

its very hard to describe, but say if ive nursed the boost in on 3rd gear, itl boost fine all the way out,

but say ive nursed it in & boosted all the way out,

then come off the accelerator....

then floored it again, it wont boost all the way out, only say 0.5b again

i would have to nurse it in slowly to get full boost, sharply flatting it doesnt boost fully.

is this:

1) the fuel pump

2) the SAFC/ insuficant fuel controlling/mapping

3) the way suquentian turbos wokor

Is it in the transition point between turbos 1 and 2 or all across the rev range?

Is it in the transition point between turbos 1 and 2 or all across the rev range?

not sure what you mean there sorry, can you elaborate?

say for example if im in first gear and do a dear start, and shift into second, it will only boost to 0.5. when the revs are all the way out.

but if i did a slow pull off start, then slowly nurst the accelerator in, it would boost fully.

The point where number 2 turbo comes online, does it come online or not?

ah rite i see,

so i maybe getting only the 1st turbo boosting when i do a drag start,

but will have to nurse the accelerator in for the second turbo...

could possibly be the second turbo not kicking in after ive let it spooled once and come off.

e.g. the 2nd turbo will only spool once been built/nurst slowly.

if i try to flat it, it wont spool...

this maybe the case?

why would this happen?

Its wierd for sure, when its on low boost does it feel noticably slower? What is your normal boost? Id say if Nevins is about and near you maybe he could have a look at it? Always hard to describe these things over t'internet

It sounds suspiciously like your pressure tank is not holding pressure.

If you look at the back of the engine, to the left of the spark plug cover you'll see the IACV VSV (labelled below). Remove the hose that goes between the valve and the hard pipes. Try to do this after your car has sat for a while (an hour or so). If you don't get a hiss of air when you pull the pipe off, I'd say you have either a failed non-return valve in the pressure tank or a spilt in one of the hoses downstream of the tank.

when its on low boost does it feel noticably slower?

Yes, 0.5bar will always feel slower, dont get the pull effect

What is your normal boost?

1bar +

It sounds suspiciously like your pressure tank is not holding pressure.

 

If you look at the back of the engine, to the left of the spark plug cover you'll see the IACV VSV (labelled below). Remove the hose that goes between the valve and the hard pipes. Try to do this after your car has sat for a while (an hour or so). If you don't get a hiss of air when you pull the pipe off, I'd say you have either a failed non-return valve in the pressure tank or a spilt in one of the hoses downstream of the tank.

 

http://www.mkivsupra.net/vbb/attachment.php?attachmentid=13940&stc=1&thumb=1&d=1131440991

 

 

http://www.mkivsupra.net/vbb/attachment.php?attachmentid=13945&stc=1&thumb=1&d=1131440991

thanks for that mate, will have a try.

funny you say that, as the car has an idle issue, where revs are low and cut out. so expect a leak somewhere.

EDIT:

it was the second turbo not coming in, due to the boost controller being wired up wrongly, to one of the VSVs that controlled the spool of the second turbo