No wastegate on turbo

[gloverman]

Lately we had a customer phone up regarding an car with no wastegates on the turbos. A 2JZ-GTTE had been fitted with twin T70 turbos. Instead of controling exhaust flow through the turbos there was a external type wastegate on the intercooler pipes before the throttle body to bleed excess boost off before the motor. Interesting idea I thought. I wish I had some photos to explain better. What do you think??

 

[striker]

much like a compressor system then,

superchargers all/most work that way, and I can't see why it wouldn't work on turbo's, the only thing is that with watsegates you can controll boost more effectivle then via a bypass valve of some sorts even if it's stepper motor drivven buy the ECU. + the wastegate pust less much less strain on the turbo's themselves.

I have never seen a race engine that didn't have wastegates, but then again I haven't seen every race engine ever build.

grtz Thomas

 

[JustenGT8]

This has been used quite a lot by one of the 'name' shops here in Oz. If you size the turbos very very well (which takes alot of experirnce with a single engine) then it can work sorta OK...... but, the main reason it's not a great idea is you put the compressor well out of it's efficiency range so while you may control boost, intake temps go thru the roof. You also run the real risk of overspeeding the shaft.......just cheap and dodgy for mine.

 

[stevechumo]

I don't think it's a good idea to use this type of controller to control the boost. It might be slower to respond to relieve the air out. Once the air is full in the intake pipe, that controller will see a certain amount of unnecessary air. That's when the engine already sucks in more air than needed. But if the wastegate is positioned before the turbo, it'll relieve the gas before the turbo, thus the turbo won't build up air in the intake pipe.

 

[gloverman]

I spent a couple of weeks thinking about the system. Apparently it's often used on drag cars. I wasn't sure it would control the boost properly. It was also hoped that it would release boost like a blow off valve on decel. We sorted a few bits and pieces on the car and went to the dyno with a lowish spring in the gate. I use another workshops dyno with a mate running the dyno and me on the ECU numbers. For this one we had another staff member watching the wideband and a fourth guy with the fire extignuisher keeping a eye on under the bonnet. The dyno man bet twenty dollars thet it wouldn't work and some other workshop owners also put their two cents in. First run with engine very rich it made 190KW and held a perfect 9psi. This tuning session was to get the engine to a safe driving point and see if the system would work. Even with huge turbos for this engine it made boost around 4000rpm and was nice to drive. No release of pressure on decel so a proper blow off valve needs to be fitted. This system worked much better than I expected, no boost spikes in the range we ran it in.
We have considered the extra strain on the turbos , one thought was by running turbos that provide less exhaust restriction it reduces the chance of overspeed. Next time we will measure the shaft speed of each turbo.
Within the range we used (rev counter on car was out so we dyno operator wasn't reving it hard) intake temps were very good.
The owner wanted the "WOW" factor and two huge turbos do that for alot of people. I look forward to doing more work on this car and seeing how the system works over a long period and how much we can extract out of it. Cheers

 

[XR8tt]

I know a few rotories like this and have throttle body pre turbo...No point in having BOV either..