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The mkiv Supra Owners Club

Help! BPU overboosting problem


DaveR

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Yesterday I replaced a few vacuum hoses on my car, including a few for the sequential turbo system.

 

Specifically:

image

 

and closer in to the turbo side of things:

image

 

The hoses circled in red are the ones I replaced; the one circled in green in each pic is one that I had replaced, but have now returned to stock (including clips) due to the routing of the new one not looking right (I made the hose longer to try to prevent it kinking in the middle, but it ended up being kinked anyway...).

 

I also, for completenss of info, replaced the three hoses for the stock charcoal canister.

 

All of the hoses that I have used as replacements are the same internal diameter as the ones that were on the car before and I have checked and double-checked the hose clamps / zip ties (as applicable) to make sure they are all done up nice and tight.

 

 

On my way back from my MOT this morning, I noticed that my turbos were overboosting. My HKS EVC-6 is set to run 1.1bar, but under load my peak hold has been up to 1.3bar and that includes me backing off the throttle before the redline when I noticed something was wrong.

 

I had a bit of a poke around under the bonnet to check that all of the hoses are secure, both the ones I replaced yesterday and the existing ones and they all look fine. On revving the engine though, I saw that the wastegate stays open for what looks like a long time. I've never noticed this before, but in fairness I've never really been looking. When the actuator closes, it makes a sort of "whoosing" or "squelching" noise, too, which is something I've not heard before, either.

 

Here's a vid of the wastegate:

 

You can just about hear the noise I'm talking about if you really listen...

 

Also, another symptom is that with the car at a standstill, my EVC-6 is registering boost (up to about 0.2bar) when I rev the engine, which I'm fairly certain isn't meant to happen - I thought that no boost was normally made when the car is in neutral?

 

Until today, the turbos have been working normally and peak hold, even when driving in a "spirited" manner with the engine revving to the redline has not spiked above about 1.18 - 1.2bar, including on gear changes.

 

 

So...

Is what my wastegate is doing normal?

Have I missed something?

Does anyone know how to cure this problem?

 

 

Basically, I want to try to avoid paying labour rates for what I imagine could be quite a simple fix...

 

Help!

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You've plumbed them in wrong bud. You have them looping over each other cutting out the VSV entirely. Have a look at the vsv it has no way for the pressure to get in, or out... it's looping lol.

 

Be careful with that stuff mate, you could have easily popped your turbos. Do them one at a time instead of pulling everything off and shooting in the dark.

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Mmm... Interesting you say that, cos that's exactly what I did - replaced them one at a time! This is exactly what they looked like before, just blue rather than black. However, assuming I did still manage to f*ck it up (it does happen...), how should it look?

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Not a chance it was like that bud, you've gotten mixed up. You would have been seeing all kinds of boost problems, like you are.

 

Looking at the picture, the LHS of the blue should connect where the RHS of the black is, the RHS of the black should connect where the LHS of the blue is.

 

OR vice versa.

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Scott, you're a legend! Thanks very much.

 

The weird thing is, I promise you it was like this before - typically I can't find a close enough pic to prove it (it's not, after all, a particularly interesting bit of the engine bay...!), but I was so careful to do all of this one at a time to, ironically, avoid any problems! Anyway, it matters not as I can now go and sort it out.

 

Thanks again!

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Guest Budz86

Not 100% sure but I think Scott is right. When I look at the first picture you posted it doesn't look like how mine are set up, I'll get a pic for you later if I get a chance

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Not 100% sure but I think Scott is right. When I look at the first picture you posted it doesn't look like how mine are set up, I'll get a pic for you later if I get a chance

 

That'd be useful if you can, matey - the more examples the better, frankly!

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So... A spot of re-plumbing later, something like this:

 

image

 

image

 

 

Quick test in second and then third gear at full load up to the redline (on private land of course) and the boost is holding steady at no more than 1.13bar. Much better!

 

Thanks again Scott - labour rates avoided!

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In (slightly) other news, my wastegate is still behaving as per how it is in my vid in post 1, i.e. the actuator staying open for a few seconds after the throttle is released. Am I to assume this is normal...?

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Told you :p

 

I think the amount of beers I'm owed is finally starting to catch up on the amount I owe :D

 

Invaluble advise from Scott there, thumbs up to you :thumbs: now relax with a game of mallets mallet :D

 

now, Scott about my aeriel thoughts ?? :innocent:

 

In (slightly) other news, my wastegate is still behaving as per how it is in my vid in post 1, i.e. the actuator staying open for a few seconds after the throttle is released. Am I to assume this is normal...?

 

no you broke it while messing about with your vac pipes.... put the spanners away :D

 

Told you :p

 

I think the amount of beers I'm owed is finally starting to catch up on the amount I owe :D

 

Cash them in at Suprapod :)

Edited by scotty71 (see edit history)
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Told you :p

 

I think the amount of beers I'm owed is finally starting to catch up on the amount I owe :D

 

You did! I actually don't mind it so much when my car goes wrong as a result of something I've done myself - I've only got myself to blame then. Touch wood, thete's been nothing catastrophic yet...

 

Definitely a few beers owed there, anyway!

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now, Scott about my aeriel thoughts ?? :innocent:

 

I checked out the thread but you already had the answer bud. If the stereo doesn't tell the aerial to only actuate when the radio is on then the only alternative with an aftermarket stereo is a switch. Simple enough to sort out though :)

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