Jump to content
The mkiv Supra Owners Club

Low Boost problem


Supraguy

Recommended Posts

Im just trying to fish around here for ideas. Noticed over the weekend that while giving the car some stick that it didnt feel like it was pulling as hard as it should. A quick look down at the boost guage and it reads about 0.8-0.9 bar.

 

Since then, I have comepletely removed the front bumber and gone over IC piping. Tried dialling up more boost, but just simply cant push anything more than 0.9 bar. I was running approx 1.35bar peak before.

 

All vac lines out of the BC Solenoid look intact, but the only thing I cant really get around to is the Wastegate. Any other ideas or suggestions?

 

Keep in mind this is a Single Turbo, so its not a blown stocker.

 

This puts a big damper in things as I was planning on running it at Pod this weekend.

:(

Link to comment
Share on other sites

Originally posted by colsoop

Im clutching at straws here but perhaps itsbuild up of heat.

i know on a cold evening i can hit boost cut but during the day it drops away from that.

 

Its definitely not heatsoak. From a cold start it does the same and Ive got an R-Spec Intercooler. Shouldnt see nearly half a bar loss of boost from heatsoak anyway, IMO.

Link to comment
Share on other sites

Originally posted by Ian C

How about a blockage in the exhaust system?

 

-Ian

 

PHR Downpipe and Midpipe and HKS Exhaust. Unless some twat has stuck something up the zorst to be funny. Doubtful, but I will have a look anyway.

 

Come to think of it, my cat as been missing for a few days! :eek: :innocent:

 

J/K :D

Link to comment
Share on other sites

Originally posted by eyefi

boost controller settings?

 

As I said, last night I played with the settings to try and turn up the boost but it made no changes. I dont think this would be the cause unless the controller has gone faulty.

 

I had pre-dialled in the settings when it was dyno tuned.

Link to comment
Share on other sites

I'd say a problem with the boost gauge but you say it feels slower as well. Might be worth checking with another gauge?

 

Exhaust silencers can have their packing material come out and block the exhaust up. Shine a torch up the tailpipe and see if there is any wooly sort of material wedged in there (hopefully it's not your pet cat).

 

-Ian

Link to comment
Share on other sites

Really dont think the guage is faulty. Ive got 3 exact readings. One from S-AFCII, one from the Boost Controller, and one from my Greddy Guage pod. :(

 

There's quite a load of difference in 0.8 and 1.3 bar on a single turbo! :)

 

The only thing I cant really check up on is the Wastegate due to location. Hopefully I can get it on a lift tomorrow for closer inspection.

Link to comment
Share on other sites

Well, if you've got three readings, fair enough.

 

The wastegate defaults to closed, under spring pressure. If that went wrong you'd get too much boost, rather than not enough. It would have to be jammed wide open for the symptoms you are describing and that's dubious. But as I have learnt in the past, *everything* is worth checking :)

 

-Ian

Link to comment
Share on other sites

Originally posted by Ian C

Well, if you've got three readings, fair enough.

 

The wastegate defaults to closed, under spring pressure. If that went wrong you'd get too much boost, rather than not enough. It would have to be jammed wide open for the symptoms you are describing and that's dubious. But as I have learnt in the past, *everything* is worth checking :)

 

-Ian

 

Yes, but spring pressure for my single turbo should be around 12psi. This just so happens to equate to ~0.83 bar. Coincidence? Maybe my boost controller is nackered and not keeping the WG shut allowing me to build more boost?

 

Got a slot in with Leon tomorrow, so we can take a better look at it with some real tools and equipment.

 

Appreciate all the help tho.. I'm running out of ideas.

 

:p

Link to comment
Share on other sites

Ah ha! Typical, the one place I couldnt get to was at fault. One of the Vac lines to the WG from the BC Solenoid had split an end. Readjusted the jubilee clamp and reattached and voila.. 1.3 bar again. :)

 

Least I was spot on with the Spring setting on the WG. Boost Controller just couldnt force more boost due to the line being cut.

 

Thanks for the help guys! :thumbs:

Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. You might also be interested in our Guidelines, Privacy Policy and Terms of Use.