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+--- Thread: How much PSI is too much (/showthread.php?tid=1456)
How much PSI is too much - Actros617 - 06-23-2010
How much PSI of boost can a OM617 safely.
RE: How much PSI is too much - ForcedInduction - 06-23-2010
I've run 18psi for around a minute at a time without issues.
Some others have run up to 26psi on the stock injection pump and turbo. They didn't understand that "more isn't better", they're overspeeding their turbo and actually reducing performance with the excessive boost.
RE: How much PSI is too much - Captain America - 06-23-2010
I don't think anyone really knows for certain.... But you will definitely run out of fuel before you need to worry about it.
RE: How much PSI is too much - Actros617 - 06-23-2010
How about using a diffrent turbo, then how much boost can the engine handle.
RE: How much PSI is too much - ForcedInduction - 06-24-2010
Pressure is pressure, the turbo makes no difference.
RE: How much PSI is too much - winmutt - 06-24-2010
My wastegate is unhooked currently, I am pulling well into 20s flooring it at 75mph. Heat soak is rampant.
RE: How much PSI is too much - Einar - 06-26-2010
I drove my `83 123.193 with the actuator hose disconnected, then I had 20 PSI, and the car had the same power as on 9 PSI, when I adjusted the pump I got 25 PSI, but the car lost much power, attached the actuator hose again, drove it on 9 PSI and I had much more power than before.
I drove it on 20 PSI for a long while, no harm done, boost dont hurt a diesel engine, but fuel can hurt it.
RE: How much PSI is too much - winmutt - 06-26-2010
(06-26-2010, 04:08 AM)Einar I drove my `83 123.193 with the actuator hose disconnected, then I had 20 PSI, and the car had the same power as on 9 PSI, when I adjusted the pump I got 25 PSI, but the car lost much power, attached the actuator hose again, drove it on 9 PSI and I had much more power than before.Did you plug the hole? I have plenty more HP.
I drove it on 20 PSI for a long while, no harm done, boost dont hurt a diesel engine, but fuel can hurt it.
RE: How much PSI is too much - ForcedInduction - 06-26-2010
More boost doesn't go anything good if you don't have extra fuel to burn with it.
RE: How much PSI is too much - Einar - 06-26-2010
I think The KKK-turbo got too busy or I got far too lean AFR for maximum power.
Only ALDA, torque and max throttle adjusted.
RE: How much PSI is too much - JTY - 06-26-2010
OM617A conrod brake limit around 38-40psi (OM617 takes less punishment).
There's allready several om617a superturbos that have made same discovery here in Finland
So to be on safe side 28psi would be the max.
RE: How much PSI is too much - MJF - 06-27-2010
28psi with small turbo is VERY different thing than 28psi with big turbo. Small turbo breaks things.
RE: How much PSI is too much - shredator - 06-27-2010
(06-26-2010, 07:29 PM)JTY OM617A conrod brake limit around 38-40psi (OM617 takes less punishment).Can you share some more info about these con rod failures?
There's allready several om617a superturbos that have made same discovery here in Finland
So to be on safe side 28psi would be the max.
In every case, were the con rods the first thing to go? (before the head gasket?)
RE: How much PSI is too much - GREASY_BEAST - 06-27-2010
How much fuel was being pushed in these 40psi failures???
RE: How much PSI is too much - ForcedInduction - 06-27-2010
(06-27-2010, 09:34 AM)MJF 28psi with small turbo is VERY different thing than 28psi with big turbo. Small turbo breaks things.
No. The difference is in density which is a function of compression efficiency.
A small well matched turbo may be running in the middle of its map at 75% efficiency, but replacing it with a big turbo running close to the surge line and 60% efficiency will produce hotter air and less CFM. So "Small turbo breaks things" is very generalized and not accurate to many applications. In other words, replacing the stock T3-45 with an HX40 and running it at the stock 9psi would produce less power (not taking into consideration the extremely poor spoolup response of using a larger turbo).
Choosing a turbo is far more involved than "I want a bigass turbo", it must be matched properly to the engine's airflow and pressure needs.
RE: How much PSI is too much - Tymbrymi - 06-28-2010
(06-26-2010, 07:29 PM)JTY OM617A conrod brake limit around 38-40psi (OM617 takes less punishment).
Thanks for the info!!
(06-27-2010, 10:53 PM)ForcedInduction So "Small turbo breaks things" is very generalized and not accurate to many applications. In other words, replacing the stock T3-45 with an HX40 and running it at the stock 9psi would produce less power.
I don't think people with an HX40 are going to be running the stock 9psi
(06-27-2010, 10:53 PM)ForcedInduction Choosing a turbo is far more involved than "I want a bigass turbo", it must be matched properly to the engine's airflow and pressure needs.
And your design goals. If you want to make huge HP numbers, you can't have the restriction in the exhaust (not to mention operating in the choke limit of the compressor) of a small turbo. Unless you put a big VGT on it, long spool up time is just a trade off.
Engineering/design work is ALL about trade offs.
RE: How much PSI is too much - MJF - 06-29-2010
(06-27-2010, 10:53 PM)ForcedInduction A small well matched turbo may be running in the middle of its map at 75% efficiency, but replacing it with a big turbo running close to the surge line and 60% efficiency will produce hotter air and less CFM. So "Small turbo breaks things" is very generalized and not accurate to many applications. In other words, replacing the stock T3-45 with an HX40 and running it at the stock 9psi would produce less power (not taking into consideration the extremely poor spoolup response of using a larger turbo).
Choosing a turbo is far more involved than "I want a bigass turbo", it must be matched properly to the engine's airflow and pressure needs.
Of course matching turbo size is important. But for example, if you use
stock, vnt, or even smaller turbo and run it ~30psi, you most likely will break a con rod, head gasket or something. With better matching turbo and you have never any problems with same 30psi boost and will get more power. This is seen gazillion times with vw-tuners.
The question was: How much PSI of boost can a OM617 safely.
I´d say it depends very much of what turbo are you using etc.
RE: How much PSI is too much - ForcedInduction - 06-29-2010
"Small turbo breaks things" isn't very accurate, its more like "high exhaust pressure breaks things".
RE: How much PSI is too much - GREASY_BEAST - 06-29-2010
(06-29-2010, 02:22 PM)ForcedInduction "Small turbo breaks things" isn't very accurate, its more like "high exhaust pressure breaks things".
Small turbo causes high exhaust pressure, high exhaust pressure breaks things, therefore small turbo breaks things. It is equivalent to say "small turbo breaks things" and "high exhaust pressure breaks things" if they are causally linked.
RE: How much PSI is too much - ForcedInduction - 06-30-2010
Right, but many people don't take EMP into consideration and thats why I mentioned it.