We have our old Supra back after 10 years! But it seems a bit slow... Info/Advice...

[Ian C]

I do recall the Superchips couldn't ever 'chip' the Supra so they bunged in a £15 bleed valve and charged you £300, nice to see that rumour was in fact true

 

OK where to begin

 

The rear VSV is the Exhaust Gas Bypass valve. It's not a wastegate per se, it controls the prespool of the second turbo (which is the rear one) by diverting exhaust gas from turbo #1 to turbo #2. This makes sure the second turbo is spinning before the other valves open to bring it online. This VSV being bypassed means the bypass valve will never open so the second turbo will never prespool, and when brought online it'll have to fully spin up first, in the face of boost pressure suddenly trying to spin it backwards. So this'll be a) why it's late to spin up and b) why it feels slow - you'll get a drop in power at the sequential transition point due to boost pressure venting out #2 turbo backwards.

 

The front VSV is the wastegate control one, and it's only used above 4000rpm when both turbos are online. With this bypassed, the wastegate will be opening as turbo pressure builds up, known as wastegate creep. This means as boost increases, less exhaust gas gets to the turbo and boost production slows. This also won't be helping power delivery and will be contributing to the late full boost symptom you're seeing.

 

I've looked at the photos, and it seems like madness. The bleed valve has been installed on the atmospheric side of the system It'll have zero effect because all the work done by the boost pressure has already been done, the bleed valve is connected to point 15 on the pressure map in the FAQ thread, where it vents back to the atmospheric side of the intake system. So no matter how far you open it, the boosted air either vents to atmo or.... vents to atmo (and gets re-ingested by the turbos )

 

To have an effect, the bleed valve should be between the #1 turbo intake scroll and the wastegate actuator (points 12 and 13 on the pressure map). All this setup does is massively delay #2 from getting online and possibly makes a nice whistling noise.

 

Well, anyway, the upshot is, bin the bleed valve and put it all back to stock, see how you get on

 

If you have a look at the images in the sequential system FAQ:

http://www.mkivsupra.net/vbb/showthread.php?35926-The-sequential-system

 

You'll see a nice overhead shot of the engine showing you where the hoses should go at the back. Also in the pictures is the pressure map and some numbered bits that correspond to numbers on the images, so it hopefully will help you check all the hoses and get them plumbed in correctly

 

-Ian

Edited September 14, 2011 by Ian C (see edit history)

[Ian C]

Poached into tech

[Robzki]

Did this ever get resolved, or did Stav disappear in the same direction as his boost?