is there "safe" boost level without intercooler?

[ipdown]

Is it safe to crank the boost a little up without having an intercooler? And how much it is safe? Will it have the desired effect? I mean will the pump give more fuel just by sensing higher boost or it also need to be tweaked.
I don't plan intercooling, I decided to go with MW50 injection, but it is not parts are not arrived yet. I will use high pressure electrical water pump and pressure switch.

[Jason]

I ran as much as 20lbs of boost without an intercooler, but it depends on your turbo... The stock turbo will be pushing hot air at the boost level, where a bigger turbo will more than likely be able to move that kind of boost more efficiently and at a cooler temp. I'm running a T3/T4 though. If your still running a stock turbo, I don't think 15lbs would be all I would go without an intercooler. You may be able to make that much boost on stock fueling with a boost controller, but it will depend on the pump settings, if its ever been adjusted, what your timing is, etc... To really feel much difference you will need to turn the pump up somewhat. As long as you aren't blasting black smoke at full boost, you are using all the fuel you are injecting and making efficient power. If its still blowing black at full boost, its turned up too far and your wasting fuel. I would also recomend grinding the fuel pin in the AFC housing. Info on that and turning the pump up is in the sticky in this section.

Remember, even with intercooling, 20lbs is really about it for stock head bolts... Some have held more, and for a long time, but the more you push the more risky it gets. If you really want to push some boost, you will need head studs.

Jason

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The turbo is stock, garrett T3. The strange is that the wastegate actuator does not have external rod, but it is somehow fitted directly on the housing. So the rod is not visible. I've never seen before such arrangement. Sorry but what is 20 lbs - is it the same as PSI? I am from Europe, you know If it so - it means almost 1.4 bars which is good. I think I am running now something like 0.8-0.9 bar at max.
I don't know the specs of the stock turbo, it looks to me something like .48 hotside A/R and maybe .42 compressor, but I really don't know. I should take a look.

From what I understand I probably can safely try up to 1.1 bar. Before playing with the pump (grinding that pin), I will probably need to read some more docs, became more familiar with it and get myself a dial gauge. I just don't feel good when I don't understand what I am doing.

And about studs vs. bolts - the car is '86 740 in very good shape, with only 140K kms. So, I just want a little bit more power, nothing monstrous and ant the car to last - and probably will not go more than 1.2 bars.

Originally Posted by Jason

I ran as much as 20lbs of boost without an intercooler, but it depends on your turbo... The stock turbo will be pushing hot air at the boost level, where a bigger turbo will more than likely be able to move that kind of boost more efficiently and at a cooler temp. I'm running a T3/T4 though. If your still running a stock turbo, I don't think 15lbs would be all I would go without an intercooler. You may be able to make that much boost on stock fueling with a boost controller, but it will depend on the pump settings, if its ever been adjusted, what your timing is, etc... To really feel much difference you will need to turn the pump up somewhat. As long as you aren't blasting black smoke at full boost, you are using all the fuel you are injecting and making efficient power. If its still blowing black at full boost, its turned up too far and your wasting fuel. I would also recomend grinding the fuel pin in the AFC housing. Info on that and turning the pump up is in the sticky in this section.

Remember, even with intercooling, 20lbs is really about it for stock head bolts... Some have held more, and for a long time, but the more you push the more risky it gets. If you really want to push some boost, you will need head studs.

Jason

[Jason]

20 psi (or lbs). 1 bar is around 14lbs so you are in the ball park. The stock turbo only has a .36 a/r hot side and a .42 (if i remember correctly) cold side. 15lbs of boost would be a noticable increase in power without really pushing it. You will want to turn up the pump though, as more boost doesn't mean more power if there is no fuel to go with it. They never came with head studs stock, that is a aftermarket performance thing. ARP makes them.

Jason

[ipdown]

Originally Posted by Jason

20 psi (or lbs). 1 bar is around 14lbs so you are in the ball park. The stock turbo only has a .36 a/r hot side and a .42 (if i remember correctly) cold side. 15lbs of boost would be a noticable increase in power without really pushing it. You will want to turn up the pump though, as more boost doesn't mean more power if there is no fuel to go with it. They never came with head studs stock, that is a aftermarket performance thing. ARP makes them.

Jason

I will see the pump mod thread. Does turning up the fuel have something with the pump timing? I guess not, but anyway, I look at the pump as a something sacred, since I don't fully understand how it works (basically yes, but not in details) and don't have instruments to check or correct the timing if I screw something. So I'd preferred to not mess with it, till now when I want more power. About the studs - I would not open perfectly working motor. If sometime it develops head/gasket problems I would replace them, but not now.

One more, a bit offtopic question - I've installed a voltmeter and boost gauge from 740 turbo to my instrument panel which don't had them. Shouldn't I see vacuum when the motor is idle? I see only positive boost. May be my hose is too soft and collapses at vacuum? Or may be the lack of throttle plate on diesels? Strange..

[Jason]

It would be the lack of a throttle butterfly... The intake tract is open on a diesel, so there is no vac at idle. As for the pump, setting the timing is another thing all together. It is something you should check though. If your timing is off, you can be throwing power and mileage out the window.

Jason

[Jason]

Originally Posted by ForcedInduction

There is no boost limit to any diesel. What IS the limit is exhaust temperature.

Don't listen to this moron. There is a boost limit on a D24t its called stretch bolts, an aluminum head, and a fiber gasket.

Jason

[Jason]

Not that it cant be improved with studs, and a MLS gasket. Even so, with an intercooler you can still push double factory boost which is a pretty good increase!

Jason

[hvguy]

A little food for thought: I pushed about 30psi on a stock 280000 mile motor and blew the head gasket.... although I think it was from the 4 or 5 times I drastically overheated it...

heat is your enemy; know this.

[Jason]

Ya if the head warps your kinda hosed, even at stock boost. More likely than not the gasket is gonna start to leak after that.

Jason