irishbastard
Hi all, my 740 Turbo has been getting worse and worse for a while now, I've noticed since I put my boost valve on it I've been slowly slowly loosing boost, I replaced all boost vaccume lines, checked all hoses for cracks/holes, I can here the turbo spool really well It just seems that theirs neally no boost at all, it sounds like the cars ready to "get up and go" but it's basically running like a 740 turbo with 4-6 psi, I've always had the boost valve set before fuel cutout which is around 14 psi, I can't work out where all the boost is leaking from?,
Any ideas/ suggestions would be appreciated,
Cheers, Darcy
Dauntless
So it's only making 4-6 psi even though it was originally set to 14?
Hoses can also leak at connections, intercoolers can sometimes leak too.
It might also be worth checking the intake hose to make sure it isn't sucking closed. Mine used to do that, it would still make 10 psi but no airflow.
If you turn up the boost controller, does the boost level increase? Does it make stock levels of boost without the boost controller connected?
Have you verified the boost controller isn't going out of adjustment? Depending on type, it may be worth marking it with a paint pen or similar.
irishbastard
Yep the boost level increases if I turn the boost up and it chokes because I then pass fuel cut out, if I take the boost valve off It makes normal boost
irishbastard
So it beats me, maybe the boost valve is putting strain on something that's leaking or maybe the boost controller is buggered?, could it be waste gate related?
egads (she/her)
How squishy are your boost hoses? My starting place would be that sucking closed assuming it behaves the same with or without mbc.
irishbastard
I bought brand new boost hoses for my black 740HP from mark iceton a little while ago that r now on my blue 740T the only thing I didn't replace woz the blue hose that connects the turbo to the intercooler pipe, the turbo waste gate hasn't been making any blow off noises, is that normal? , I'm not sure what a mbc is could you fill me in @egads‌
egads (she/her)
Okey doke, so those should be ok. Mbc is manual boost controller. Test that out I reckon.
irishbastard
Kool yep, I'll have a look first thing when I'm home tomoz at the boost controller, it's pretty new, probs not even 2 months old, mark iceton brought it for me for my black 740 t but I stopped driving it so it's on the blue 740 t now, and then this problem started
Dauntless
At what pressure are you hitting fuel cut?
irishbastard
About 15 ish psi
Dauntless
If you're constantly having to turn up the boost controller to maintain your boost levels, it's probably going out of adjustment. It's unlikely to be a leak that's progressively getting worse.
If when running directly to the wastegate you're not having any issues, the problem is almost certainly the boost controller.
I'd suggest paint marks on the boost controller as a starting point.
irishbastard
Yep will do, someone suggested it could be the intercooler leaking I think they could be right too
Vee_Que
Do you tighten the nut holding the adjuster to keep it in place? Is it on the right way?
Philia_Bear
Truboost is your answer
Worth every cent
deleted_user_160
Depends which mbc darc got. Some are bold and nut on a 90deg joiner (like ours Alex), very agricultural, others are like the turbosmart, greedy type etc. Adjuster on spring ball bearing click type.
Darc did you install the mbc the same way it was fitted on the black car?
irishbastard
Yep, It was bought for the black car but never fitted to it, I definetally installed it on the blue one correctly, mark had a look while he was over helping me put a red leather interior in it
nickm
Leaking cbv or wastegate diaphragms?
deleted_user_160
oooo that means you might like my red centre cosole cup holder arm rest. NOS including the OEM box. got it shipped over from the US. installed on my car, realised it will be a shit with the T5 box so now its off.
irishbastard
Yep, I'm definetally interested, how much were u after jay?
deleted_user_160
$70 and I'll drop it off. Inc box. It's all about the oem boxing.
