ive got 2 theories as to why it isnt make boost.
a/ the comp cover has been machined too big. so there is either too much clearance radially or axiallly, thus not allowing boost to build.
b/ way out of balance, and not able to spin upto boost.
it is very loud when trying to boost, and have checked that the wheels arent coming into contact with the housings.
also locked off wastegate to make sure that wasnt jamming open.
just want to know other peoples thoughts on why it isnt boosting.
no cat on vehicle.
pipes fine and plumbing.
plenty of oil bearings,ok. spins on after switch for about 30 nseconds. i actually think there could be too much oil. whats recommended volume? garret only supply a min pressure spec.
spoke with mtq about comp cover machining as i think they machined the cover too deep. (compared with other turbos i have laying around) diameter looks fine. i have to take it back to them monday to see what they can do..
and i think the noise is due to som e slight misalignment during assembly of the ground t3 shaft into gt cartridge.
big pain in the arse
around 1-2l min for a bush turbo, probly halve that for a BB turbo do a search on here there was a discussion about this a year ago or so, no company howevery can give flow figures only pressure figures but pressure varys with restriction, on a BB turbo you only want to just wet the bearing, too much oil and the balls tend to float and wear unevenly.
my mate had his t28bb turbo down to 400ml a minute at idle as oil kept coming out the comrpessor cover, car ran for a few months before he sold it.
ok here are my results.
my .9 welding tip turned out to be 1.1mm.
i got
360cc/min @ 65psi @ 30 degrees oil temp
480cc/min @ 43psi @ 53 degress
480cc/min @ 33 psi @ 63 degrees
doubling the flow rate would mean i need a 1.5mm restrictor.
1.3mm
800cc/min @33psi @ 60 degrees
1.4mm
960cc @35psi @ 55 degrees.
so ill stick with the 1.4mm orifice. oil will get a bit hotter, and flow will increase a bit.
i've heard anywhere form half a litre/minute is ok, so im happy with 960cc
even if the comp cover is machined a LITTLE bit to big, wouldnt it still make boost? i meant he compresor will still be spinning at 150000rpm. if it has to fill the compressor cover, piping, plenum etc, that slight extra volume shouldnt worry it, the onlyt hing im not sure on, is if it will effect the airflow properties in and out of the actual wheel itself that much as to stop it making boost. what was peak boost/lowest vaccum it made?
what are you using to measure/check for boost? have you eliminated that as a possible problem?
Quote:
Originally Posted by R34NRG
even if the comp cover is machined a LITTLE bit to big, wouldnt it still make boost? i meant he compresor will still be spinning at 150000rpm. if it has to fill the compressor cover, piping, plenum etc, that slight extra volume shouldnt worry it
Nah hes not talking about volume hes talking about the clearance in between the side of the compressor wheel and the compressor housing so that all the boost would just leak out the front of the turbo...
IMO theres just NO way any turbo shop could possibly make a mistake like that!
If the turbo seriously isnt making boost its got to be a balancing/bearing issue. Perhaps the bearings are way to tight or something.
the clearance was greater than other turbos i had, so on reassembly i spaced the wheel closer to the cover to allow for it.
i think the main problem was due to it being so far out of alignment when it was assembled it was that foar out of balance it wouldnt spin up.
anyway its at mtq now for a dynamic test to make sure its ok to go this time.
and i posted my oil figures for other peoples benefit, not saying that was my problem.
