Is there a market for a factory twin turbocharger upgrade for MKIV??
 

Hello all.

I am a newbie and what I do for a living is design and manufacture turbocharger upgrades for all kinds of cars.

I have a MKIV customer right now that sent me a set of turbochargers to upgrade. I need to know what are the do's and don'ts and what their limits are. I will not be reusing the old CHRA's. The turbochargers will have 100% all new parts in the CHRA's and will be built for big boost. This upgrade will not just be a larger compressor machined to fit the factory turbine wheel. I know the stock turbos are weak and cant handle too much boost for very long.

I am here to gather ideas that will get you what you want and need.

My business is well known in the RX7 community. Our business holds the HP record on factory based twin turbo upgradess and also holds the record for the older RX7 single turbo upgrades as well. I want to offer you guys the same...

Bryan@BNR
205 640 1193
www.bnrturbos.com

The tiny, pencil-thin shafts are the weak point in the oem twins. If you can machine out the housings to accept a larger shaft, then you'll probably be able to put on some larger wheels and have the result be reliable. Fwiw, as far as I know (and I've been heavily involved in the Mkiv community since early '98 ... and owned an Mkiv since early '94), every single attempt to put larger wheels on those oem pencil-thin shafts has failed within a few thousand miles of driving.

...so to boil that down: first and foremost, the upgrade >>>must<<< be reliable.

Secondly, the more horsepower the better. I honestly can't imagine any size of wheel you could fit into the oem housings that would be too large for the needs of the Mkiv Supra community.

Please keep us informed, and feel free to contact me to discuss further.

Turbochargers are almost complete. I have custom pieces to get CNC machined before I can post pictures of them. I am certain that you guys will be pleased with the final product and it will be something you have never seen.

As for the wastegate actuators, how much boost is possible with the factory actuators and should they be upgraded? I want you guys to turn these things up :D.

Do you have boost creep issues?

Bryan@BNR
205 640 1193
www.bnrturbos.com

Good to hear...we're looking forward to it.

With a 'bpu' Mkiv Supra tt, the wastegate actuator (there's only one for both turbos) will hold about 22psi at most (on race fuel of course). Some owners have added a spring to resist the actuator, which results in a further increase to about 28psi max. Note that 28psi is only possible on a 'fresh' (i.e. low mileage) set of oem twins...and they're running very inefficiently at that boost level.

Yes. For example, the oem boost point is supposed to be about 11.5 psi. With the simple addition of a downpipe, the oem ecu won't be able to regulate boost down below about 13.5-14psi.

Why do you ask?

I ask about the creep b/c that is a problem for some cars. I would like to know the charactoristics of the twins so I can solve problems.

Bryan@BNR
205 640 1193
www.bnrturbos.com

I understand, but this generally isn't an area of focus for Mkiv Supra TT owners (and as a result, there's very little data on this topic). Since the 2jz-gte is such a 'stout' engine, boost creep is almost regarded as a 'good' thing with the stock twins. Assuming sufficient octane (i.e. race fuel), the oem twins can not produce anywhere near enough boost to hurt the engine.