Author Topic: pump timing ? (Read 4626 times)

craiggroombridge · « **on:** March 07, 2007, 06:19:09 pm »

I'm starting to work on my 92 na, my injectors were taken apart and cleaned, now bently quote is 1750 psi for my car , if I set them at 2250 psi how much more timing will i need to add to compensate for the added pressure? or do i just set it at the turbo setting?

Craig

pernalonga · « **Reply #1 on:** March 08, 2007, 03:53:39 am »

Hi there

Increasing injection pressure does not require any extra timing advance.

Increasing injection pressure does improve thermal eficiency as well as ar/Diesel mixture so it also increases engine power.

Make sure u tune it all together, delivery ports with injection opening pressures.

REgards

Mark(The Miser)UK · « **Reply #2 on:** March 08, 2007, 04:56:55 am »

Quote from: pernalonga

Hi there

Increasing injection pressure does not require any extra timing advance

Are you sure?
Increasing injection pressure does improve thermal eficiency as well as ar/Diesel mixture so it also increases engine power.

Not sure about this one either... more like create a faster burn to the point of bang which raises temp of mixture which leads to a greater temp gradient across/through the head which leads to more power sunk into the coolant Nowa "ceramic-a-sized" head might reduce this... then there's the energy in the extra squashing of the fuel

Make sure u tune it all together, delivery ports with injection opening pressures.

REgards

[/size]
Strange

'Course I could be talkin' through my hat :mrgreen:

Sorry this post is a mess :roll:

craiggroombridge · « **Reply #3 on:** March 08, 2007, 05:45:32 pm »

well thanks for the replys but the higher psi is to allow better misting of the fuel ( smaller droplets) to better combust, at least this is what i was taught in school? i could be wrong but I don't think I am..
and yes the higher psi will take more time to make, this is why i need more timing, all that aside if I screw up so be it this is my first idi and some of the tricks used on bigger non computer controled idi's should work on this one as well

Of course I could be wrong?? what will it cost me? that is yet to be seen, again thank all of you

Craig

Mark(The Miser)UK · « **Reply #4 on:** March 08, 2007, 06:38:47 pm »

Quote from: craiggroombridge

well thanks for the replys but the higher psi is to allow better misting of the fuel ( smaller droplets) to better combust, at least this is what i was taught in school? i could be wrong but I don't think I am..
Of course I could be wrong?? what will it cost me? that is yet to be seen, again thank all of you

Craig

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It does seem intuitive...But what has to be remembered is that in the absence of faulty injectors we never (rarely)get incomplete combustion otherwise there would be more people committing suicide by diesel wouldn't there... :?:
Edit...
Somewhere I have a book that talks about overfine spray where the droplets are so small that their flames don't propagate so quickly. If we remember that there is a lot less diesel fuel in a chamber than petroleum so where a gasser runs relatively rich and operates best from wide dispersal; maybe diesel droplets run the risk of becoming isolated in places and so don't burn uniformly... MAYBE

craiggroombridge · « **Reply #5 on:** March 09, 2007, 09:24:03 am »

ok good points both, so what i'm getting is if I lower the psi, it will get better mpg, with possibly more smoke? if i rase it i get cleaner burn and less mpg? well I guess I need to test this on my car for my self...

Thank you for your time and effort

Craig

burn_your_money · « **Reply #6 on:** March 10, 2007, 06:52:48 am »

Andrew when you did the testing with yours and your friends car, do you guys drive your cars hard or do you drive for economy, also how old was your pump. I'd imagine the pumping loses would be less on a freshly rebuilt pump.

I'm glad someone else is testing this because I was going to do the exact same thing with my car, thank you

tylernt · « **Reply #7 on:** March 10, 2007, 11:36:41 am »

Let's refer to this as 'pumping effort', shall we? "Pumping loss" generally refers to the work the engine has to do to get the air in, compressed, and out of the engine. Increasing the breaking point has nothing to do with air but with increasing the parasitic HP draw of the pump via the timing belt.

Has anyone used a beam-type torque wrench to turn an IP hooked up to an injector to see how much torque it takes to pop the injector at various breaking points? I have a hard time believing that the difference is large enough to have an 8% impact on fuel economy. You'd be shredding timing belts, or snapping them. My guess is the increased breaking pressure is having some other effect that decreases MPG.

tylernt · « **Reply #8 on:** March 10, 2007, 11:40:17 am »

Come to think of it, don't the check valves on the back end of the pump have to be matched to the injectors? If you increase the breaking point of the injectors, don't the check valves have to be altered to match?

craiggroombridge · « **Reply #9 on:** March 10, 2007, 03:53:55 pm »

the check valves do not need to be calabrated they are there for reverse flow control only they don't have a " calulated" pop psi.

The weather here is getting better, soon i'll start testing all my theries and libbybapa's lower as well and I will publish my results...

as for turning toque for the ip the more psi will cause more parasitic losses but I thought the better burn from the fuel might offset that, my ip is only 460,000 kms old :lol: and I have a kit on the way any hard parts I can get localy so i will be starting from fresh.. or should that be scratch.

and I know that a timing belt is desined to take tremendus torque when adjusted properly, cause it has the same power as the clutch side

Craig

SMOKEYDUB · « **Reply #10 on:** March 10, 2007, 04:06:00 pm »

why not just try dual stage injectors out of a 1.9. If i am correct the send out a small amount of diesel as a "pilot" light and then send in the big batch. Correct me if im wrong...

Mark(The Miser)UK · « **Reply #11 on:** March 10, 2007, 04:38:56 pm »

Further to my theories on lower injection pressures; I'd like to add a proposition that if someone has a high mileage engine and adds 'new' lower pressure injectors then the lower compression ratio will also increase mpg. This assumes that the cylinders are all reasonably similarly worn.
Granted there will be some gain from the couple of pints of oil per K-miles; but 2 pints in 180 is only 1.1% ish.
Also starting difficulties may be an issue...

Does anyone know of a series of graphs of starting difficulty at different air temperatures at different compression ratios? (glowplug assisted?

H'mm this willl probably only need a few points of reference from anecdotal evidence from forae-ees

What evidence do I have?
My best performing Quantum definitely had lower compression than my others Did I measure the values? Nope ...because it's parked up at my parents farm awaiting a respray for 2 years and I never got round to it :roll:I obviously have too many Quantums :wink: Really must make that injector pressure tester too. :lol:

Mark(The Miser)UK · « **Reply #12 on:** March 10, 2007, 06:01:51 pm »

All that's really needed is data from people who have done rebuilds due to smoking engines that actually still started easily (or not) and had prior rebuild compression checks.
I suppose the bigger the engine the lower the compression ratio required... but is there a difference between 1.6 and 1.9?

Will a 1.6TD start with good glowplugs when only 18:1?