Turbo 2H - low boost problem (1 Viewer)

[ca18sean]

Turbo 2H guys help me out. Turbo Dynamics/Denco kit fitted. Runs like a top, got the fuel adjusted pretty well. Slight black smoke at low RPM, almost none at high. EGT at the manifold with the sensor on cylinder 5 is 950F degrees max, usually sits much lower. But it won't build more than 5 psi. Even with the waste gate disconnected and wired shut. I had a nasty exhaust leak and two broken exhaust studs so I just pulled the exhaust manifold, turbo looks ok. Very little shaft play. Spins freely, no abnormal noises. It is a Schwitzer S2A (T3 flanged). Changed exhaust studs, exhaust gaskets, turbo gaskets, and all the turbo hardware. Put it all back together and still 5 psi. What do I look at next? No intercooler, all hoses and couplers are new too. I'm stumped. No massive leaks that I can see or feel. Here's a couple pics of the setup.

Untitled by CA18 Sean, on Flickr

Untitled by CA18 Sean, on Flickr

Untitled by CA18 Sean, on Flickr

 

[Mookies]

I don't have a turbo 2H but on my Hilux the air filter was not flowing enough air for such a long intake including the snorkel. Seemed to be starving the turbo a bit until I swapped in a new one. If you wire the waste gate shut it should build fast though. Are you sure the boost gauge is accurate?

 

[ca18sean]

I don't have a turbo 2H but on my Hilux the air filter was not flowing enough air for such a long intake including the snorkel. Seemed to be starving the turbo a bit until I swapped in a new one. If you wire the waste gate shut it should build fast though. Are you sure the boost gauge is accurate?

I was wondering if it was the snorkel as well... I may take it for a spin with just a cone filter installed on the turbo and see if it builds more boost.

Boost gauge is a brand new VDO unit and if I blow into it with my mouth it registers more than 5psi. So I don't believe that's it. The previous boost gauge read about the same (but was in Bar as the truck came from Australia, so I preferred to switch it to PSI).

 

[AussieHJCruza]

Is something choking the flow of air into the turbo?

It's not likely, but is the snorkel clogged somehow? Or something in the airbox restricting flow. The factory filter should be no worries at the boost a 2H is happy with.

Also, I've had poor experiences with large silicone hoses that might see vacuum, such as from your air filter to crossover pipe, found they collapsed easily.
No worries under boost, but not so much vacuum. Heavy walled rubber seemed to be better under vacuum.

Lastly, your EGTs do seem quite low, but I guess if it was making boost before with the same fuel load, there's no reason why it shouldn't now.

 

[Mcreight911]

The schwitzer s2a is quite an unresponsive turbo . It has an old school design turbine which isn't the most efficient and the turbine housing is probably on the large side for your use . I think denco use a .50 or .54 A/r turbine housing . I'd say that 5psi is about all that it will do with a factory 2h pump. There simply isn't enough energy to drive the turbine to make more boost.

 

[AussieHJCruza]

Aha...it's a new install. Sorry, for some reason I thought it had been on before and was previously making more boost. X2 on what @Mcreight911 said then.

If the pump will deliver more fuel, 950F has a bit of room for more...I personally wouldn't run an IDI diesel at more than 1100F sustained under load.

 

[ca18sean]

Not a new install. Reinstalled with fresh gaskets. Making the same boost as before. It runs great at 5psi I was just wondering if it would make a little more. I'll try cranking fuel up a little more. Max EGT on the highway with the pedal down is 1000F.

 

[ca18sean]

Snorkel is new-ish, I installed it when I got the truck. And the silicone hose has a very short unsupported section. Both pipes nearly meet in the middle. I can't crush it by hand so I don't think that's the issue. But I'll try running without the intake pipe and see if it changes anything. Thanks for the suggestions! I'm thinking it's just a too large exhaust housing for a stock pump. Spool isn't super quick but it isn't unbearable. Is there a turbo size that's recommended for a stock 2H for when I get around to replacing this guy?

 

[ca18sean]

Update, I tested it with the intake piping removed. No change in boost. Right at 5psi. Also cranked up the fuel another turn. More black smoke, but no boost change. Didn't run it long enough to see what it did to the EGT's but it smokes like crazy now, so I'll be turning it back down. Lol. It's crazy that it can't make more boost. I guess I don't have enough experience with turbo diesels, but with a turbo gasser I've never had boost building problems that weren't leak related. My only turbo diesel experience is with our 7.3 Ford's at work and they build PLENTY of boost (unless you have a leaky intercooler connector). Oh well, I'll keep running the S2A until it gives out then upgrade to a better turbo!

 

[coldtaco]

So, it basically always has run only 5psi boost, this is not a new condition?

 

[ca18sean]

So, it basically always has run only 5psi boost, this is not a new condition?

Correct. But I knew it had at least one, maybe two bad exhaust port gaskets. So I was hoping with those fixed the boost would come up some. It does appear to have dropped the EGT's slightly without any exhaust manifold leaks, and of course no more ticking noise, but that's about it.

 

[IanB]

If you're first post hadn't stated you've tried wiring the wastegate shut with no changes I'd be suggesting that 5psi is what the wastegate is set to. Doesn't really make sense that the turbo is operating fine but you can't get it to build more than 5psi of boost.

 

[Tapage]

if I got you right not matter how much hi you go in the rpm range still 5PSI ..?

I'm using an old KKK model and I'm able ( with all the fuel pump it's capable up at this point ) to go 14 - 16 PSI by 3K rpm ..

 

[ca18sean]

if I got you right not matter how much hi you go in the rpm range still 5PSI ..?

I'm using an old KKK model and I'm able ( with all the fuel pump it's capable up at this point ) to go 14 - 16 PSI by 3K rpm ..

That's correct. It's like it's opening a wastegate and holding the pressure at 5psi. But it's not, because the actuator is wired shut. So I either have a massive boost leak either on the intake or exhaust side (which I'm not seeing) or it's running out of fuel to push the turbine any faster. I have the fuel cranked up so it leaves clouds of black when accelerating from a stop, but it hasn't increased the boost any. It drives pretty well, I'd say its about as fast as my 3RZ Tacoma.

 

[Tapage]

I'd say its about as fast as my 3RZ Tacoma.

Either your Taco it's pretty slow or your 2H it's insane fast ( fast I can't imagine it could be )

Are you positive about your boost gauge .. ?