Low boost / Sluggish

[Kai]

I guess this thread is for clarification more than anything. Before the rebuild, the turbo would spool to 10psi (off the gauge) and pull like a train. The turbo itself hasn't been touched (aside from fresh gaskets, and the housing cleaned). Now, the turbo takes a few seconds to spool, and when it's done, i see max of about 5/6psi, even with my foot flat to the floor in 4th.

I did notice, on my initial startup - exhaust gas escaping from somewhere. If the turbo to manifold joint isn't tight enough, that would obviously cause a lack of boost, but...what about a leak from the turbo to elbow? Would that also cause a lack of boost? I'm pretty damn sure there are no boost leaks anywhere else - all the pipework is bolted down fairly tightly.

Thanks in advance!

 

[SideWinderGX]

Yes, that leak from the turbo to elbow will cause a weird exhaust profile increasing backpressure...not sure if it would have the effects you're describing though. Have to go back and tighten everything up =\

 

[hvyman]

Could also screw with the o2 sensor. But that doesnt get used at wot.

Maybe the waste gate is weak or is there any cracks on the flapper hole?

 

[Kai]

Wastegate was fine when i put it on, its on an adjustable actuator, set for 10psi.

The TSRM's 'TC' section shows the elbow, but no torque settings for the nuts - is there a recommended setting? Also - the turbo to manifold specifies 34lb/ft for the nuts but there's no way to get a torque wrench in there, so it was tightened to 'as tight as i can get it with a ring spanner'.

 

[hvyman]

I do the dp/elbow tight as they light to back out if not.

Same for the turbo.

 

[91Supra313]

I get them as tight as I possibly can. I basically put everything I have into it.

 

[Kai]

Well i got it to boost to 8psi just now, not entirely sure how - was just taking it 'round the block' so see how it coped. On an uphill twisty section doing about 40mph and trying to give it some throttle, it CHUGGED. Didn't want to go up it - but i kept the throttle at a constant and got up the top of the hill, downshifted to 3rd and it was fine. Drove okay. Got to the last section of straight tarmac outside my house, and gunned it in 2nd - boom, 8psi right off the bat, changed into 3rd and eased off the throttle and the engine died. Gave it drive again, engine sparked up like nothing had happened.

Pulled into my courtyard, and aside from the top end tick from valve clearances, it idled okay, no codes showing, no warning lights for anything. Very strange. All related to exhaust/boost leaks, or is this a case of shitty fuel thats stood in the tank for a while, AFM being unfiltered (yes, i know, i can't find an AFM adapter anywhere in the UK)...?

 

[Kai]

bump :/

 

[hvyman]

Could be from the fan blowing air to the afm. Screws up its readings. If your stock fan.

 

[Kai]

I didn't think of that....and yes, stock fan. Anywhere other than suprasport i can get a filter adapter for the AFM?

 

[hvyman]

I just saw one either yesterday or today let me go look. What are you looking for like a apexi or something or like a 3in filter adapter?

 

[hvyman]

http://www.amazon.com/APEXi-507T001-Power-Intake-Filter/dp/B000W7UQ3C
http://store.driftmotion.com/static/i-apexi507-t001.php
http://www.horsepowerfreaks.com/performanceparts/Toyota/Supra_MK3/Intakes/Air_Filter_Adapters

 

[Kai]

LS400 mounting is the same as the stock AFM, isn't it?

 

[hvyman]

Yup.

 

[Kai]

Okay - that makes things easier then, for now, i'll swap over the filter and adaptor from the blue one to see how that affects it.