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  #1  
Old 02-15-2006, 01:06 AM
ForcedInduction
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Fuel pressure

What PSI range does the feed pump give to the IP?

As way to bump performace, is there an external adjustment (cap for a spring, etc.) to bump up the IP's regulated pressure a few psi?

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  #2  
Old 02-15-2006, 01:38 AM
Brandon314159
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As I have read it regulates in the low 10's as far as PSI I believe.

To change the pressure you would need to fiddle with the relief valve on the back of the IP (the engine block side). Its the banjo bolt that looks a little extra tall

The pressure relief vave is inside that unit and you would have to tear it apart to figure out how to bring the pressure up a tad. I guess you could also put an external regulator on there as well.

Haven't taken that thing apart personally...though I expect I might be getting into it sooner than I wish simply becuase I am having issues with random power delivery.

When the engine is stone cold I can get massive power when I foot it.

But after I do this a few times its not longer good...and its not the IC getting head soaked because sometimes I have good power with a warm IC...

BTW...just curious...what do you wish to accomplish by doing this adjustment? Remember that the IP is metering fuel by volume and is a closed system once the valve starts delivering fuel to the injector. Much like putting water in a given volume its tricky to fit MORE in there under a slightly greater pressure like you otherwise could with a less dense fluid, such as air
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  #3  
Old 02-15-2006, 02:08 AM
ForcedInduction
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Quote:
Originally Posted by Brandon314159
BTW...just curious...what do you wish to accomplish by doing this adjustment? Remember that the IP is metering fuel by volume and is a closed system once the valve starts delivering fuel to the injector. Much like putting water in a given volume its tricky to fit MORE in there under a slightly greater pressure like you otherwise could with a less dense fluid, such as air
My idea was that at full output, higher psi could push that little bit more fuel into the pumping chamber before it's closed off.
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  #4  
Old 02-15-2006, 02:16 AM
Brandon314159
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Quote:
Originally Posted by ForcedInduction
My idea was that at full output, higher psi could push that little bit more fuel into the pumping chamber before it's closed off.
I guess it is possible...however much like hydraulic fluid and the like its pretty hard to push MORE fuel into a given space as it doesn't compress beyond its normal state very far.

It might help compensate for a weak lift pump or something but just remember that the IP is metering fuel and not simply doing the gasser fuel injector thing of opening a valve and saying "cmon out boys!!!" hehe.
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  #5  
Old 02-15-2006, 08:53 AM
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Under low load conditions (but decent rpm) with a clean filter, I see between 12 and 15 psi at the ip. Under heavy load it will drop to between 8 and 10. At idle it is usually around 12.

I really don't think you're going to see any gains at all by adding any higher pressure. I say this because I've seen the pressure get down to as low as 0-2psi under load with a dirty filter and yet still haven't seen any drop off in performance. If it doesn't drop off at that low of pressure, I can't see a few extra psi adding much.
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  #6  
Old 02-15-2006, 09:41 AM
LarryBible
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You guys are talking about the low pressure of the fuel being delivered to the pump. Bumping this up will NOT change the amount of fuel injected into the cylinders. You will have to do something on the high pressure side that will increase the pressure at the injector.

How to do that I have no clue. I do know that if you can do something to pressure more fuel into the engine you will get more power. I also know that you will be doing this at the expense of SERIOUSLY REDUCED ENGINE LIFE.

Back in the sixties and seventies there was quite an underground racket going on. It involved "turning up" Cummins diesels and I expect that there were ways to do the same with Cats and Detroits.

Drivers would find one of these yahoos and have them do their thing, which on a Cummins involved changing a restrictor that caused more fuel to be forced into the delivery system and less rerouted to the tank. This resulted in significant power increases and seriously reduced engine life.

The drivers that did this were RARELY the owner of the truck to which they had this done. I saw some "turned up" Cummins engines that had made it no more than 30,000 miles after being turned up before needing a major overhaul. On a Cummins of the seventies 30,000 miles was nothing, they commonly went AT THE VERY LEAST a half million miles between overhauls. As you might expect the owners of these trucks had to be peeled off the ceiling.

SOOoooo.... if you want more power, go for it, but I would advise that you start shopping for engine rebuild parts as soon as you "turn it up."

Have a great day,
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  #7  
Old 02-15-2006, 11:01 AM
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Quote:
Originally Posted by Brandon314159
BTW...just curious...what do you wish to accomplish by doing this adjustment? Remember that the IP is metering fuel by volume and is a closed system once the valve starts delivering fuel to the injector. Much like putting water in a given volume its tricky to fit MORE in there under a slightly greater pressure like you otherwise could with a less dense fluid, such as air
liquids tend to atomize better when fed through an injector at a higher pressure. Also in a diesel the fuel spray may get a little farther before it burns because its moving faster, thus distributing heat a little better. On an OM617 I'm not sure what this will accomplish as it is injected as a thin jet that hits a ball in the prechamber.

some of the effects are shown in this report http://powerlab.mech.okayama-u.ac.jp/~esd/comodia2004/A6_1_022.pdf
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  #8  
Old 02-15-2006, 02:04 PM
Brandon314159
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Quote:
Originally Posted by ConnClark
liquids tend to atomize better when fed through an injector at a higher pressure. Also in a diesel the fuel spray may get a little farther before it burns because its moving faster, thus distributing heat a little better. On an OM617 I'm not sure what this will accomplish as it is injected as a thin jet that hits a ball in the prechamber.

some of the effects are shown in this report http://powerlab.mech.okayama-u.ac.jp/~esd/comodia2004/A6_1_022.pdf
But that is if the metered liquid is actually going through the injector at a higher pressure (like in my SD). To accomplish that you would have to adjust the pop pressure of the injector to a higher value than the stock 135bar for turbo motors.

I think that putting more "pre metering" pressure on the IP won't accomplish anything unless there is something in the system not doing its job.

I support upping the pop pressure slightly as it does help atomoize the fuel a little better but I don't think anyone will get much extra bang for their buck by trying to pressurize the IP's fuel inlet side. The diesel shop that I visit for questions and such also hears good reviews of a slightly higher pop pressure on the mercedes turbo engines...
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  #9  
Old 02-15-2006, 09:18 PM
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Quote:
Originally Posted by LarryBible
You guys are talking about the low pressure of the fuel being delivered to the pump. Bumping this up will NOT change the amount of fuel injected into the cylinders. You will have to do something on the high pressure side that will increase the pressure at the injector.

How to do that I have no clue. I do know that if you can do something to pressure more fuel into the engine you will get more power. I also know that you will be doing this at the expense of SERIOUSLY REDUCED ENGINE LIFE.

Back in the sixties and seventies there was quite an underground racket going on. It involved "turning up" Cummins diesels and I expect that there were ways to do the same with Cats and Detroits.

Drivers would find one of these yahoos and have them do their thing, which on a Cummins involved changing a restrictor that caused more fuel to be forced into the delivery system and less rerouted to the tank. This resulted in significant power increases and seriously reduced engine life.

The drivers that did this were RARELY the owner of the truck to which they had this done. I saw some "turned up" Cummins engines that had made it no more than 30,000 miles after being turned up before needing a major overhaul. On a Cummins of the seventies 30,000 miles was nothing, they commonly went AT THE VERY LEAST a half million miles between overhauls. As you might expect the owners of these trucks had to be peeled off the ceiling.

SOOoooo.... if you want more power, go for it, but I would advise that you start shopping for engine rebuild parts as soon as you "turn it up."

Have a great day,
on the cummins you refer too the injection system is the "pressure time system" I dont claim to know much about it except the broad strokes but a mechanic i talked to years ago said they cranked those things up till fire came out of the stack!

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