4.0L OHV Turbo - Not Building Boost!

[norm209326]

I did a custom turbo setup on my 4.0L OHV (in my 99 exploder sport) and Im having trouble with it. Its simply not building boost.

Specs:

Small turbo from a mid 80's Mercedes Turbo Diesel (not sure exactly what size) - internally wastegated and set at 7 lbs
Custom manifold piping and downpipe
Custom charge pipe with blow-through MAF and blow of valve (before the MAF).
Apexi air fuel controller
Stock injectors
66mm (i think) throttle body (its the aftermarket BBK one)

Now, I have the turbo running off only the passenger side bank. All the plumbing is done right, but the turbo won't spool. No boost leak, I would hear the air escaping. The a/f ratio is perfect, as we monitored it with an air fuel meter while tuning. Intake turbine is not spinning on the shaft. The wastegate is not stuck open. So far Ive narrowed it down to the possibility of a vacuum leak (the car doesn't idle that well) as well as my EGR stuck open. However, I don't understand why I wouldn't see at least a little boost (even a pound or two). I plan on getting rid of the EGR and smoking the vacuum system this weekend to see if that fixes anything.

If there are any turbo gurus on here, please give me some input or point me in the right direction. Im getting very frustrated with this build.

PICS:







And the truck

[norm209326]

Sorry, the BOV is not pictured in that top pic, but it is between the MAF and the turbo

[norm209326]

bump

[ZBlackBeast]

Probably not enough, or a consistent flow of air off JUST the passenger side. Not only that but your changing back pressure and flow characteristics of the motor.

What car exactly did you get it off of?

[norm209326]

Originally Posted by ZBlackBeast

Probably not enough, or a consistent flow of air off JUST the passenger side. Not only that but your changing back pressure and flow characteristics of the motor.

What car exactly did you get it off of?

shouldn't be a problem, saab ran turbo's off one bank for a long time until recently. and although the saab turbos are smaller, i should still see at least some pressure being built

i believe it came off of an 86 mercedes 300, but I'm not entirely sure. my turbo guy had it on his shelf for a while and when he heard exactly what my project was (and that i was only running off one bank, or 2 liters) he thought this turbo would be a good match and he rebuilt it for me.

[IAmTodd]

Originally Posted by norm209326

shouldn't be a problem, saab ran turbo's off one bank for a long time until recently. and although the saab turbos are smaller, i should still see at least some pressure being built

The turbo on a 3.0t was more of a restriction than anything. It wasn't even equipped with a wastegate it was so useless.

[FIND]

That turbo on the OM603 was barely big enough for for the OM603, it is not big enough to feed a 4.0. Turbos aren't just about the amount of boost they make. The CFMs they deliver is what you need to pay attention to. Find it's long lost twin and you will get enough air to your engine.

[mp40]

I assume that the turbo has been checked to see that the compressor side impeller does indeed turn?

It does seem odd that a turbo especially what looks to be a large turbo, doesn't supply *any* measurable boost.. Does the intake have any cracks and are the gaskets in good shape?

Have you ran the truck without the air filter on it to see that the impeller is turning? Do you have another turbo to try?

[FIND]

Originally Posted by mp40

I assume that the turbo has been checked to see that the compressor side impeller does indeed turn?

It does seem odd that a turbo especially what looks to be a large turbo, doesn't supply *any* measurable boost.. Does the intake have any cracks and are the gaskets in good shape?

Have you ran the truck without the air filter on it to see that the impeller is turning? Do you have another turbo to try?

Nah, that's a little guy. Plus, it is made to spin up at a low RPM and isn't made to deliver a lot of air because it was just adding boost to a diesel engine to make it efficient, not really to make much power. It only had to worry about supplying air to an asthmatic 3.0. Since that engine really only makes 143 HP, it doesn't need a lot of air. It probably isn't that the turbo isn't making boost... It just can't delivering enough cubic feet of air to the manifold to actually boost over the air that 4.0 can swallow just on vacuum.

But yeah really, Diezel Benzs are really popular in Finland, and those guys will tell you the first thing they have to do to make any power is change turbos, then change plungers in the injector pump.

[norm209326]

Did a smoke test on the vacuum system yesterday.... there are no leaks whatsoever. Got about halfway through removing the egr (installing new drivers side tubular manifold with egr plugged) and after breaking 3 of the 6 studs, i called it quits for the weakend haha.

im picking up an intake plenum from a 94 ohv (the aluminum one) without an egr hole, so once i get that ill finish everything up and try again.

[norm209326]

Originally Posted by FIND

Nah, that's a little guy. Plus, it is made to spin up at a low RPM and isn't made to deliver a lot of air because it was just adding boost to a diesel engine to make it efficient, not really to make much power. It only had to worry about supplying air to an asthmatic 3.0. Since that engine really only makes 143 HP, it doesn't need a lot of air. It probably isn't that the turbo isn't making boost... It just can't delivering enough cubic feet of air to the manifold to actually boost over the air that 4.0 can swallow just on vacuum.

But yeah really, Diezel Benzs are really popular in Finland, and those guys will tell you the first thing they have to do to make any power is change turbos, then change plungers in the injector pump.

It seems that you're exactly right. Ive looked up the flow maps for this turbo (which is a t3-45) and the intake flow map for the explorer and found that the turbo simply doesn't move enough air.

We have a t3/t4 lying around, so were going to try to modify as little as possible while bolting it on to see if it changes things.