VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: dillenger1 on September 14, 2008, 07:09:37 pm
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Im reading on another forum about adjusting internal pressure by means of pressure valve.I would like to know if anyone does this without a tach and how?It seems the pres. increase is linear through rpm range,so if i set my idle by ear(+-900rpm)Then set pump pressure to 40psi(seems to be magic number)them viola fuel economy!for testing i should probably get a tach huh?
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by tach you mean internal pump pressure gauge??
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no, its certainly a TACHometer he means
for these scientific purposes I wouldn't rely on the W terminal tach setup, its good to watch a needle move on the dashboard, but its too uncertain for this.
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Take a good read of that thread again. Lot's of good information in it.
The magic number is about 40psi@1000rpm. However, I found that even with my timing set at 1.00 it would advance too much at that pressure.
But take a read of the thread; I explained it all there.
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Post a link to the "Other" thread please?
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Here (http://www.vwdieselparts.com/forum/viewtopic.php?t=5936)
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Take a good read of that thread again. Lot's of good information in it.
The magic number is about 40psi@1000rpm. However, I found that even with my timing set at 1.00 it would advance too much at that pressure.
But take a read of the thread; I explained it all there.
So is that 1000 rpm engine rpm and not pump rpm?
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Engine RPM.
First page, first post of the thread.
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OH WOW!!!
You wanted me to read all that ???? :D
Thanks man.. :)
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ive tapped my out bolt.it turned out great .i did it on the drill press.I was able to just penetrate the top and not marr the bottom of the screen plug.Im going to tap for 1/8npt then use grease hose for a permanat gauge to start taking some readings when im up and running.Ill get some pics later.
(http://i249.photobucket.com/albums/gg206/2253benjamin/volkswagendiesel013-4.jpg)
out bolt tapped!!
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I'm planning on the same thing, I just need to get a vise for my drill press..
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I'm planning on the same thing, I just need to get a vise for my drill press..
Me too.
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Engine RPM.
First page, first post of the thread.
What remains to be answered, is 'flow rate at idle' means what speed?
Should idle mean 800rpm? or 1000rpm? Flow rate has no meaning until this is answered, and now Hagar is 'dead' he's not answering :roll:
So to check condition of pump we need a gauge attachment
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These are the pressures that I came across, as I don't have access to the Bosch official info. Unfortunately I don't know how to post pictures, so you will need some graph paper and pencil. Also these are given as engine RPM's and psi. Also the "research" is done on my pair of SB engined GTD's, with the "w" tach.
In all cases PSI was plotted against RPM's in 500 rpm steps. All fell on a straight line when plotted on a graph, so for my convenience I shall just give 1000 & 3000 rpm pressures. Plot these on a graph.
Hagars Recomended, 1000rpm 43psi, 3000rpm 107psi. from internet.
Ford 2.5 DI engine, 1000rpm 50psi, 3000rpm 90psi. from internet.
my 150,000 mile GTD, 1000rpm 35psi, 3000rpm 65psi. before adjusting.
my 200,000 mile GTD, 1000rpm 22psi, 3000rpm 60psi. before adjusting.
my 150,000 mile GTD, 1000rpm 50psi, 3000rpm 81psi. after adjusting.
my 200,000 mile GTD, 1000rpm 37psi, 3000rpm 80psi. after adjusting.
My thoughts are that there is a drop of pressure as the pumps age. This is probably why these cars like some extra advance on the pump static timings. Once adjusted, standard static timing seems to work good. I think 40 psi at 1000rpm is about the best setting, with standard injection timings. Adjustment of the pressure valve is VERY sensitive, so be GENTLE using a pin hammer and drift as there is no easy way to reduce pressure if you go too far. There was not much dramatic change with the 150,000 mile car but was a touch "naily", so I probably hopped past the sweet spot, which is probably at Hagars 43 psi. The 200,000 mile car was much improved, much less smoke, starts better, uses less juice, but it was knackered when I bought it 100,000 miles ago, and the compressions haven't improved since. Good luck and have fun. I have zero assets so please don't sue me when it all goes wrong.
:D [/img]
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Just to add a bit more, adjusting the pump pressure doesn't alter the gradients of the pressure vs rpm graphs. Also my two identical pumps also have different rates of pressure rise. My guess is that older pumps were optimised for performance and or fuel consumption, the newer pumps might be hamstrung by needing reduced NOx emmissions, ie lesser pump advance than is ideal at higher rpms. My next project will be to get some pressure valves from older pumps and test this. Bosch technicians must love reading these as we blunder about trying to optimise these things by guesswork and inspiration.
Flow rate, if the fuel filter is bunged up, then there will be no way to correctly adjust the pump pressures, pulling off the pressure guage to see if lots of fuel pours out while the engine is running would indicate that the filter isn't doing too bad.
Yet another thought, I would be leery of destroying the fine mesh screen that is in the outlet elbow as it is a useful way to find swarf collecting from a pump commiting suicide. It doesn't do anything useful though as your injectors will be full of swarf too. :roll: Er, what is there for then? :twisted:
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the screen in the bolt is palstic.Its some kind of a plug thats held in with a brass bushing of some type.Some very small tolerances so i chose to not mess with it.