How much PSI is too much
How much PSI is too much
06-23-2010, 09:31 AM
#2
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.
This post was last modified: 06-23-2010, 09:36 AM by ForcedInduction.
ForcedInduction
06-23-2010, 09:31 AM
#2
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.
06-23-2010, 09:55 AM
#3
1982 300D Turbo ... 3,6xxlbs, No fan, No AC, Hood Stack, No ALDA, No rear bumper and stuffed front, A/W Intercooled, Injectors by Greezer and HUGE Pre-Chambers with help from OM616 & Simpler=Better, Fuel Cranked up, 60 Trim Compressor wheel, EGT, EMP, Boost 50" Rigid Radius bar on roof Aux tank for a total of 48 Gal Of Diesel! Odyssey PC-1750 Battery in trunk, 27"x8.5"/R14 Maxxis BigHorn Mud Terrains, In June '14 issue of Off Road Mag
AX15 Jeep Trans swap in progress....
Captain America
06-23-2010, 09:55 AM #3I don't think anyone really knows for certain.... But you will definitely run out of fuel before you need to worry about it.
1982 300D Turbo ... 3,6xxlbs, No fan, No AC, Hood Stack, No ALDA, No rear bumper and stuffed front, A/W Intercooled, Injectors by Greezer and HUGE Pre-Chambers with help from OM616 & Simpler=Better, Fuel Cranked up, 60 Trim Compressor wheel, EGT, EMP, Boost 50" Rigid Radius bar on roof Aux tank for a total of 48 Gal Of Diesel! Odyssey PC-1750 Battery in trunk, 27"x8.5"/R14 Maxxis BigHorn Mud Terrains, In June '14 issue of Off Road Mag
AX15 Jeep Trans swap in progress....
06-26-2010, 04:08 AM
#7
I drove it on 20 PSI for a long while, no harm done, boost dont hurt a diesel engine, but fuel can hurt it.
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.
06-26-2010, 07:43 AM
#8
(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.
1987 300D Sturmmachine
1991 300D Nearly Perfect
1985 300D Weekend/Camping/Dog car
1974 L508D Motoroam Monarch "NightMare"
OBK #42
(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.
1987 300D Sturmmachine
1991 300D Nearly Perfect
1985 300D Weekend/Camping/Dog car
1974 L508D Motoroam Monarch "NightMare"
OBK #42
06-26-2010, 08:06 AM
#9
ForcedInduction
06-26-2010, 08:06 AM
#9
More boost doesn't go anything good if you don't have extra fuel to burn with it.
06-26-2010, 07:29 PM
#11
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.
- MB w126 300SD Superturbo (US) -83, Mods: OM617A with custom head work, Master Power Turbo 802332, PP-Diesel custom 7mm IP, China intercooler, KKD-Motorsport exhaust manifold, DIY intake manifold, Coolmist Waterinjection, DIY Supermeter display/datalog with PLX Wideband Lambda, Siekkinen custom 722.3 autotrans, Elbe Performance LSD, Green Filter cold air intake, straight 3" exhaust with two dual 2.5" outputs
- MB r129 500SL AMG (JDM) -94
Full AMG bodykit, full JDM features, modified ECU and exhaust
- MB w123 250E-TT (JDM) -85
Full 1JZ-GTE twinturbo conversion, full aircon, custom china cooler, custom IC-pipes, custom sport recaro interior, custom 3-piece JDM rims
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.
- MB w126 300SD Superturbo (US) -83, Mods: OM617A with custom head work, Master Power Turbo 802332, PP-Diesel custom 7mm IP, China intercooler, KKD-Motorsport exhaust manifold, DIY intake manifold, Coolmist Waterinjection, DIY Supermeter display/datalog with PLX Wideband Lambda, Siekkinen custom 722.3 autotrans, Elbe Performance LSD, Green Filter cold air intake, straight 3" exhaust with two dual 2.5" outputs
- MB r129 500SL AMG (JDM) -94
Full AMG bodykit, full JDM features, modified ECU and exhaust
- MB w123 250E-TT (JDM) -85
Full 1JZ-GTE twinturbo conversion, full aircon, custom china cooler, custom IC-pipes, custom sport recaro interior, custom 3-piece JDM rims
06-27-2010, 03:01 PM
#13
(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?)
(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?)
06-27-2010, 10:53 PM
#15
(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.
This post was last modified: 06-27-2010, 10:59 PM by ForcedInduction.
ForcedInduction
06-27-2010, 10:53 PM
#15
(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.
06-28-2010, 09:12 AM
#16
(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.
John Robbins
'05 E320 CDI - 118k - Faaaaaast!!
'87 300TD - 317k - Cracked head... but an OM606 is on the way!
'79 300SD - 295k - Bad engine = project car!
(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.
John Robbins
'05 E320 CDI - 118k - Faaaaaast!!
'87 300TD - 317k - Cracked head... but an OM606 is on the way!
'79 300SD - 295k - Bad engine = project car!
06-29-2010, 04:56 AM
#17
(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.
This post was last modified: 06-29-2010, 04:58 AM by MJF.
(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.
06-29-2010, 02:22 PM
#18
ForcedInduction
06-29-2010, 02:22 PM
#18
"Small turbo breaks things" isn't very accurate, its more like "high exhaust pressure breaks things".
06-29-2010, 08:40 PM
#19
(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.
GREASY_BEAST
06-29-2010, 08:40 PM #19(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.
06-30-2010, 12:50 AM
#20
This post was last modified: 06-30-2010, 12:50 AM by ForcedInduction.
ForcedInduction
06-30-2010, 12:50 AM
#20
Right, but many people don't take EMP into consideration and thats why I mentioned it.
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