WVO & Injector breaking pressure

[maxfax]

So at the monthly get together of we locals who burn all sorts of crazy stuff in our diesels the subject came up about higher injector breaking pressures and WVO..  (The beer was only half gone at this point)  I know I have heard mention of just this possibly here or somewhere in cyberland.. Since my engine is crap anyhow I've been considering toying with this a bit..   
 
IIRC I would need to advance timing to compensate for the higher pressure.. Since I don;t have the proper adapters for my diesel timing doo dad, I guess IP timing would be set by ear mostly... Anyone have something that would give a rough idea of the amount of timing change versus breaking pressure??

So how how high could I go and still have the pump be able to deal with it, and not be blowing things apart? At least 155 bar, how about say 170 bar???

Still rolling the idea around yet..  But since I don;t plan to be in the situation of having a running car with a crap engine for much longer why not try and blow something up! 

Thoughts, opinions, suggestions??   

[burn_your_money]

The pump can handle a lot more pressure then you will ever want to set your injectors at. I have to check some of my books but it's well over 200 bar.

[maxfax]

Excellent, that answers that much..   I wasn't planning on anything over 200 bar as my pop tester only goes to about 173...

[Rabbit on Roids]

we were putting 285 bar injectors in our volvos in alaska. they have a VE rotory pump just like our engines, but with a 12mm pump.

[jtanguay]

increasing the breaking pressure is a very good idea while running WVO.  it will ensure a proper atomization and less problems in the long term.  it would mean that you would only have to heat WVO to 100F or less?  to get the same effects as with lower breaking pressures, resulting in a cooler running pump which means increased longevity 

i suppose there are additional parasitic losses from the high breaking pressures though... this can be compensated with timing etc. though.  it will probably require lots of trial and error though to find the 'sweet spot'.

[maxfax]

286 bar on a VE pump.. Hmmm  Nope don't trust my welds on the pop tester that much.. 

I haven;t had the pump fail yet, but in the grand sceme of things it's onky got 150K miles on it.  As it is now I have some temp controls on the system as I was seeing the returned fuel temps matching the coolant temps.. AS of now I have it regulated (somewhat) to keep the fuel going in at around 180F..  Lower temps would woudl also allow for faster switching and possibly a smaller heat exchanger down the road..

Timing is going to be pretty much by ear..  So far I been lucky enough to usually hit the IP timing right by ear.. I need to contact a Snap-On rep..  I was given an older diesel timing doo dad called a lumy-mag..  It has all the GM diesel adapters but no VW...

 My thought for finding the ideal breaking pressure @ a certain temp would be to build another pop tester for WVO and heat the goo to the desired temp, then visually compare the spray pattern with a stock injector on diesel..

[burnt_servo]

the best way to see if a higher breaking pressure will work with a given fuel , is actually run the fuel at what ever temp you intend on running it , through a pop tester  with the same injector you are running and watch the spray pattern .
you may be surprised at what you see .

[burn_your_money]

The pump can handle a lot more pressure then you will ever want to set your injectors at. I have to check some of my books but it's well over 200 bar.

Well I checked my book and it says 200 bar. I suppose if you want to run higher opening pressures you would need to upgrade some pieces inside the pump. TDIs run at 220/300 bar so the VE pump is completely capable of higher opening pressures.

[maxfax]

Makes sense, more pressure, more stress, larger shaft needed..   

I managed to find a 3000 PSI  (206 bar?) gauge in my piles o crap.. Knowing the limit on the pump is 200 bar (Thanks Tyler) 185-190 bar sounds like a decent limit to allow some leeway...

Now to get a pop tester built with some variety of heating element...

[burnt_servo]

i thought i'd throw this out there ....

anyone know what some of the longer term problems of  running a really high pop pressure

i'm at 2800 psi right now , fuel consumption is down , power is up and black smoke is reduced , but the engine is a bit louder with the same dymanic timing  as stock .


* edited to make the post clearer . *

[maxfax]

OOOOH!  That's the other question I been wanting to throw out there!!!  All I could think of is why didn;t VW do that if the atomization is better....

You say the same timing burnt_servo, you mean the stock setting, or one reasonably close for the stock breaking pressure that is..

Generally  noisy means the timing is too far advanced, however from what I understand the higher breaking pressure will essentually make the injection timing late...   Hmm Maybe you're atomizing the fuel so fine that it combusts easier and therefore faster essentually compensating for the late injection timing??  (Okay I really have no clue, just pulled that outta my butt )

[Rabbit on Roids]

All of the higher bar VE pumps use the 20mm shaft.

my pumps were running 285 bar with a 12mm pump head. and they had 17mm shafts. i checked cause i was gonna try and bring one home with me.

[Jettage1]

so...  increasing the pressure could help with running WVO better - but if your system is like mine, you start on diesel and probably want to retain the flexibility of diesel use. 

So I come back to - if you optimize for WVO are you by definition "un-optimizing" for diesel?

BTW, max, we're not all that far from each other...  We went to Raystown earlier this summer & would have driven right by you.

[maxfax]

Good question, I'll let you know the answer as soon as I find it out..

I've got the same thing, start on diesel, switch to veggie..   In the summer it wouldn;t be much of an issue as everything gets hot quick and I run very little diesel though..  (1800 miles to a tank).. However, in the winter it's not near that good.. Then again, if I can run the veg at a lower temp that could change.. (one of the ultimate goals here, to run less diesel)..

It's going to be a tricky balance of acceptable diesel performance and improved veg performance.. I do want to retain some of the ability of it to run well on diesel (filters plug, valves take a poo etc)..  I wouldn't mind sacraficing some performance or milage on diesel if the veg does significantly better.. I'll define significant as soon as I figure out what that is...

I think I'm gonna put together 3 sets of injectors, first set to 170 bar, the next at 180, and the last at 190... AFter seeing which ones work the best both on the bench and in the car I can tweak from there.. Unless I blow the little bugger up first....

Honk and wave the next time you pass by!!!  Or stop for a beer, I always like an excuse to have a beer

[burnt_servo]

changed my post above to basicly read " the engine is louder with the higher pop presures , but with the same dymanic timing "

and


before you guys get all excited about increasing your pop pressures for veg oil .....

 run some through a pop tester first .

at room temp , canola oil needed to be mixed in a 30/70 ratio of veg oil / diesel for it to atomise ..... above that it was pretty much a solid stream , no spray .  even at 2800 psi , still a some what solid stream
i also heated some to just over 50 celcius .... still no real change just a soild stream at both 2300 psi and 2800 psi .

 this solid stream of oil is what will kill your engine , beacuse you will end up with a stream of burning oil into your piston rings , burning off your engine oil and sludging up the rings / crankcase oil .


higher temps in theory will cause things to atomise  , but i haven't tried them in a pop tester yet .