Hey guys,

While I don't have the time, money, or skills to emulate some of the more extensive modifications seen on this forum, I'd like to get some more juice out of my '92 740 turbo. Right now I don't have the cash for a 3" exhaust, but I was going to plug up a boost gauge and see what the current boost is and dial it up a bit.

I know the stock boost settings are pretty low, so what can I crank the boost up to before I'm limited by the exhaust? Also, I've read here that the redbock is a pretty robust engine. Should I be concerned that turning up the boost will impact reliability?

My turbo is the mitsubishi turbo. Everything on my car is stock....for now.

Of course I've read the sticky threads...so I have some sort of an idea of what I'm going to do. Just not sure where to put the few bits of cash. Where is the best place to start?

 

boost gauge and 10-12psi will make a big difference for a start. Stock computer will adjust to the new settings. those are cheap upgrades. rule of thumb is around 10hp per 1psi increase. you need to run 91+ octane from now on. only do this after you have a fairly solid base to work on. stage 0 first.

these are faily strong blocks. Josh from yoshifab is pumping out 390 whp on a stock bottom end with some ebay upgrades, and 16v head.

 

^ Thanks! I've really enjoyed reading your sticky post, you've done a great job. I'll keep doing some searches and figure this out. Turbobricks looks pretty good.

My car is pretty solid, just did a big overhaul and am pretty happy with it overall. I've put on the IPD lower chassis brace and I see you have the upper engine brace.... I'd like to go with another brace once I get the turbo putting out a bit more...

 

Your 92 motor has the bigger 13mm rods so you should be good to go as mentioned. You have a bit to go before the exhaust is an impediment. It's nice to have, but a mandrel bent 3" exhaust is pricey, although it is quite simple to install on a 7 series...goes straight back from the motor. Your car has a rather tiny Mitsu turbo. Originally, Volvo used a larger T3 Garrett turbo...boosted more but had more lag. Most Americans then, and now, expect instant power a la V8's. So...the smaller, faster boosting turbos came along. The only issue is they fall on their face at 5k. Another rather simple swap is the cam shaft. The stock T cam has a decent amount of low end but again, falls on its face around 4200-4500 rpms. Swapping in an IPD or RPI turbo cam will really wake up the motor. But...that isn't cheap either. Larger, used turbos on TB are relatively inexpensive and a major improvement too.

 

This is great stuff...I appreciate the knowledge drop! i'm actually kicking myself right now for not going with the IPD turbo cam when I was doing my big HG repair. Eventually when I get some more cash, I'll replace the stock cam.

I'm very new to turbo's, as this is the only car I've ever even driven with a turbo, let alone owned. I'm becoming a little obsessed since I think they are really cool with tons of potential. Would a bigger turbo be an upgrade even with a stock exhaust? If I only had the money to do either/or, which would be the better choice?

 

Meh...if it were me, I'd get the car back to stage zero first. Fresh vac hoses, rad hoses, belts, brakes, tires, shocks, O2 sensor, filters, cap and rotor, plugs and wires. Then, I'd score a turbo and sit on it until I could do the exhaust. Meanwhile, as Jeff has suggested, get a manual boost control and a numeric gauge. Bumping the boost up 4-6 psi will make a big difference. Being in Lubbock w/ the heat...you'll want to run 93 octane at least in the summer. I ran 16 psi on my 84 760 w/ stock T3 and stock intercooler. 93 octane and octane booster...any more boost was just hot air as the stock i/c won't handle it. 16 was the naked edge...I backed it off to 14 and ran that regularly right up until I took her back to stock to sell.

 

Sounds like a good plan, I'll keep checking TB for a turbo at a price I can stomach. Until then, I'll follow your advice and keep replacing things when I can, getting it back to 0.

I'm a pretty decent welder so I figured I could do the exhaust myself, just run a high flow muffler and no cat. Keep the stocker just in case... Is that what you guys do?

 

The trickiest part of the exhaust is the down pipe...and if you weld, even it isn't too bad. Once it is installed the rest is simple. Here's pics of my 84 760. Not counting the down pipe, I did it in an afternoon. Not nearly as pretty as my 240 exhaust...was my first attempt.
from front, looking aft...

bullet cat...

DynaMax oval muffler...

14" glass pack for a resonator...

Here's the final result in a sound byte...
‪84 760 Tic.wmv‬‏ - YouTube

 

^ Cool man, that looks do-able. There are plenty of muffler shops here where I can get the parts. I guess once I find a turbo then it's just a matter of finding a flange...

I don't expect any of this to happen overnight, my time-frame is within the coming year to slowly get this done. At this point I'm pretty much married to my 740, considering how much time I've put into her!

 

Yeah...the good thing about the 740...If you spend money on her...she won't let you down!