Turbo Help On MY Supra 94 TT
 

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

Welcome wayne,

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

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:

http://www.benzworld.org/forums/atta...-image0261.jpg

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.