Turbo Help On MY Supra 94 TT

[wayne2jz]

I have a stock twin turbo and last week when I decided to downshift to 3 from 4 and gave it gas. It felt as if the cars first turbo worked like it should have but then when the second turbo kicked in it felt like a major lag.To me it feels like the second turbo is spooling its self up instead of the first one helping it out. I can hear the first one then the sound goes away. Please help

[warmkop]

Welcome wayne,

pwpanas will be able to help you with the stock turbo setup he is more familiar with it.

[pwpanas]

Originally Posted by wayne2jz

I have a stock twin turbo and last week when I decided to downshift to 3 from 4 and gave it gas. It felt as if the cars first turbo worked like it should have but then when the second turbo kicked in it felt like a major lag.To me it feels like the second turbo is spooling its self up instead of the first one helping it out. I can hear the first one then the sound goes away. Please help

Note: The first turbo doesn't help the second one spool up, except indirectly (i.e. through the engine - boost from #1 -> more total exhaust -> helps to spool up both#1 and #2 together).

Here's more info on how it all works:
http://mkiv.com/93-98-twin-turbo-faqs-2/#turbosystem1

...and here it is stated differently, from Toyota themselves:

http://mkiv.com/specifications/ncf/ncf93/ncf091.jpg (start about halfway down the page)
http://mkiv.com/specifications/ncf/ncf93/ncf092.jpg
http://mkiv.com/specifications/ncf/ncf93/ncf093.jpg
http://mkiv.com/specifications/ncf/ncf93/ncf094.jpg
http://mkiv.com/specifications/ncf/ncf93/ncf095.jpg

I'll guess as to what may be the problem BUT if you *really* want to figure it out 100% for sure, buy the TSRM and follow the troubleshooting steps. Please trust that the TSRM is an EXCELLENT investment - probably the best one you'll ever make (now that you have an Mkiv TT).

My guess: Based only on what you've told us so far, it's some sort of failure in the operation of #2. Hopefully it's not the #2 turbo itself, although that could definitely be the issue.

Here's the first test: Check for boost leaks. You'll need to pressurize the entire charge-air system and listen for leaks. You can rig up some sort of cup with a tire valve that fits the hose clamp behind the MAF, for example. When I do the test, I pressurize to at least 40psi (be careful - hose clamps not securely fastened can pop and shoot things across the room). I figure 40psi bone-cold isn't all that different to a hose clamp than 20psi or so when running very hot. Anything leaking? If so, fix it. Here's a pic of a boost leak tester:

Here's second test - set it temporarily into TTC mode:
http://mkiv.com/techarticles/ttc/ttc.htm
...if this fixes the total horsepower issue (noting that overall spool-up will be slower), then #2 is okay. However, if you're still getting a lack of total horsepower, your #2 might be kaput.

If there are no boost leaks but #2 is okay, then it's time to start troubleshooting your VSVs and actuators (most likely the ones related to the operation of #2)...one by one. It's painstaking work, and (by far) best to follow the TSRM step-by-step. As you've read above, the oem sequential TT system is not at all simple. It's a thing of beauty when it works right, but when it doesn't finding the problem can be a pain in the butt.

Good luck, and please keep us informed.