captiva

Does it take much of an air/vacuum leak to lose boost? I suspect the plenum gasket as I have the classic symptons, according to this forum, as I have hesitation/misfire under boost , soot coming out the exhaust and AFR that keeps changing and loss of boost

silky16v

iTrader: (1)

get the whole intake system pressure tested, a good test is to start car hold revs abour 2000rpm then get a can of WD40 and spray it around the area you suspect the leak you can sometimes see where the fluid id being sucked in and you also find that the revs will increase or die in some cases.

The other thing i'd check is the Map Sensor, Phase Sensor Gapping (and conditon), Crank Sensor condition and gapping also the condition of the whole ignition system

captiva

This only started happening when I fitted a T34 turbo so would think that all of the above was OK and perhaps would not contribute to a loss of boost pressure don't you think?

silky16v

iTrader: (1)

what boost pressure you running have you upgraded the rest of the management system so thats it aware that you have fitted a T34
(eg: bosch 803's, 3 bar Map Sensor, ECU Chip)???

captiva

Yes I had all the above before. I had a T3 and went to a T34 and new MSD chip.

silky16v

iTrader: (1)

well double check all gapping on the sensors if in doubt replace them
check the condition of your ignition amplifier also what voltage are you getting at the fuel pump & at the ECU.

do not continue to try and drive car as it will cause damage.

also what plugs are using? and what boost pressure have you got it set at

captiva

Got Denso Iridium IK27 plugs and boost is set to "half a hole" (4mm) which is giving me 15psi. When I tighten rod, no increase in boost, have removed jet from R port on amal too.

JTECH James

iTrader: (13)

as siad your next step really needs to be a pressure test, could have a leak somewhere opening up at higher boost levels...ive had a few in my cossie time

also maybe you have a shagged acuator spring......

captiva

Got a new -31 actuator so can't be that. How would I pressure test it as there will always be at least one valve open

JTECH James

iTrader: (13)

the system i use is a cylinder leakage tester, which normally would be used to pressure up one cylinder down the plug hole. i made a series of adaptors so i can fit this to the air filter hose, so it pressures everything from the turbo compressor housing..... it has a regulator so you can adjust the ammount of air going into the system, and has a gauge to tell you what percentage of air is being lost.

yes you always lose some through the engine valves, but the system can hold 3 bar, and leaks are easy to spot.

you will be amazed where you find leaks...and how many aswell

JTECH James

iTrader: (13)

heres mine....

captiva

That sounds like a great idea but can't quite see how you can measure the percentage loss when one of the valves will be open I would assume that it would not pressurize at all because any air would be going out the valve. No, hold on it would fill the cylinder wouldn't it but it must be crucial where the crank is like TDC or somewhere when exhaust valves were closed. Am I on the right track?

Can you send your gauge over to Canada!!!!!!!!!!!!!!!lol

JTECH James

iTrader: (13)

it works really well, you always gets a small loss through a valve, turn the engine over untill it reaches the smallest amount of loss,

but the system can add more air than is being lost so still reaches the desired pressure.

pop your car over and i'll show ya

captiva

I'm on the next boat!!!!!!!!!!!!!!!!!