greenworks

I have been chasing down boost leaks for weeks and have finally got them all fixed except a fair size leak on the intercooler.MY question is the manufactuer says the turbo wastegate is set at 42 psi and I can only get to 39, how much will 3 psi mean in realtion to a reduction in EGT's I should note I am struggling keeping it under 1500 at WOT hence why I have been searching for so long on this boost leakage. Thanks fellas

jimjawz

I dont think three pounds will make that big a deal

RowJ

Another way of looking at it is your losing over 7% of your boost. With your box & injectors, if your fighting high EGT's, I think that might be significant!

RJ

greenworks

Rj thats what I was thinking, it soesn't seem like much but it is.

HOHN

As you go higher in total boost, individual boost differences mean less and less.

3 Psi from 20-23 is VERy significant.

3 Psi from 39-42 is much less significant.

3 psi from 90-93 is practically insignificant.

To put this in proper perspective, you should compare PSIA, not PSIG like your gauge shows. Add atmospheric pressure (14.7psi@ seal level) to your numbers, THEN look at the difference. That's a more appropriate context for your numbers.

I would say that the difference from ~ 53psi to ~ 56psi is not that significant in determining your EGTs.

I suggest you look elsewhere to figure out your EGT problem. You might be a candidate for a CAM upgrade or ported head.

Justin

BigBlue

Or twins.

greenworks

I am now dumbfounded..... I talked to the BD power service manager and he explained that during a pressure test you should have no leak through the valves at any point in the crank rotation.....WHAT!!!! That would mean no gas would ever leave the piston right? He says I should be able to pressure up the system and it shoul stay pressurized baring no boost leaks like I have been chasing. Maybe I have been sniffing to much diesel but is ther a point at least where all exhaust or intake valves would be closed to even do this? I asked this question before but everyone said no, ohterwise a person would have to plug of the air at the intake manifold or intake horn to have pressure stay in the system. Am I nuts, because the way this BD talks my valves are FUBAR! Yet the truck runs like a champ just a very hot one.

BigBlue

If the intake valves are open, then the exhaust should be closed and no pressure would escape from that. If the intake valves are closed, then no pressure should escape from there. And chances are that one or the other is closed so you shouldn't lose pressure through them.

greenworks

So what this BD guys is saying should ring true once the system is pressured up the truck should stay that way unless I have a bad valve/s? I guess I know know what I will ask santa for

Kyle Graham

If your running those injectors and comp on 5x5 w.o.t. that would be a 450 rwhp truck to say the least if your valve's are ok you might want to go with twins bd doe's sell a kit if you did just buy the one to upgrade it to twins second turbo and all the piping ats manifold and so on. Hopefully valvetrain is alright.

berner

There's a point in a gas engine that both valves are open a bit. It's referred to as "overlap". The intake starts to open before TDC on the exhaust stroke, while the exhaust valve is closing. I'm betting that a diesel engine operates the same. When I checked for boost leaks, I had air coming out of the exhaust pipe. In my case, it's either valve overlap, shot exhaust valves (not), or leaking turbo seals (maybe).

greenworks

kyle that was the reason for buying the top turbo only just for now, but does the theory make sense that nothing should leak through the exhaust at any time with the intake system pressured up? I'm glad somone chimmed in with the same though as mine about the impossibility of all the valves being shut at any given time, the way I think you will always have some leak through

Bushy

There is valve overlap and you will have some leakdown during a pressurizing test.
We normally pressurize to about 20 psi, then listen first...then go hunting with soapy water depending on the RATE of leakdown. It is very slow, but it does leak down.

pb....

greenworks

bushy counting leakdown through the valves starting at 20 psi what kind of time where you seeing for a loss of pressure? I think I am going to block the intake horn this weekend to get an idea as to how much is actually leaking from the turbo to the manifold.