Lister Engine Forum

Alternative fuels => Straight Vegetable Oil => Topic started by: vegoil on March 28, 2020, 02:34:41 PM

Title: injector
Post by: vegoil on March 28, 2020, 02:34:41 PM
Has anyone increased the pop pressure of the injector on a Lister cs 8/1 running on WVO or is this not a good idea?

Title: Re: injector
Post by: veggie on March 28, 2020, 02:46:54 PM

Good question,
A few years ago I sold 2 Listeroids to a fellow who had been running wvo for 5 years in an older Lister.
He experimented with all kinds of stuff and he told me that when I start running WVO in my Lister I should "lower" my pop pressure a little bit.
That did not make sense to me so I didn't do it.

Title: Re: injector
Post by: glort on March 29, 2020, 04:26:48 AM

This came up years ago when Veg oil was all the rage for Vehicles. Wonder if it might see a resurgence now as the world rebuilds? Not many vehicles left that can run it.  Might keep my eye out for a bargain.

Increasing the pressure makes NO difference other than to put added stress on the IP.
Even a " low" pressure Mechanical pump is running over 20,000PSI and anyhing you can turn the pressure up to from there isn't going to make a damn of difference. There is not a lot of margin in high and low recommended pressures anyway so it would only make a small percentage difference.  You can't just screw the pressure up to whatever you want.

  I remember someone doing a test on it years ago and they  turned the pressure up to about double and tested what I seem to remember was a Cummins engine and could find no difference other than the IP making horrible noises.
It's a thought most people have had I think though.

What makes a HUGE difference is having a new injector over an old one.
I had an injector fail in my truck and even though the previous owner said they had been changed just 3 years earlier, I swapped them out.
What a difference!

Wisely, I turned the Fuelling down on the IP from where I had screwed it up to before firing the thing up the first time.  When I test drove it the power and performance was slightly up at only HALF the boost I was running before.  Quite amazing.  I never touched it from the guestimate I set it at.
Thing pulled like a train and was a lot less stressful on the turbo on everything else.  I believe it was a little more economical but I would have burnt any economy advantage so may have been imagination. I am confident that if driven more conservatively the thing would have used less fuel as it was certainly smoking a lot less.

After 19 years of using veg, I also completely dispute the oil preheating mantra.
The Pump is well bolted to the block and runs at a similar temperature. the injector will be hat head temp. You can pre heat the oil hot as you like but to think the amount of oil passing through the IP  is going to make any difference and not be sunk into the block or even if you heat between the IP and injector, if that isn't going to be wicked away by being wedged into a 20 KG lump of metal where the tip of the injector is indirectly exposed to the combustion flame front, then someone is believing in fantasy.

Whatever temp the engine and particularly the head is sitting at is the temp the oil will be injected at no matter what you do to it before hand.  The only reason to pre heat oil is  to melt any fats from blocking the fuel filter. If your oil is prepared right, You shouldn't even have to do that.

Clean, DRY oil and an injector in good condition will make infinitely more difference than higher pop off pressures.

Title: Re: injector
Post by: vegoil on March 29, 2020, 12:25:02 PM
That makes good sense. (best to leave it set to original Lister factory settings).

Title: Re: injector
Post by: listeroil on April 07, 2020, 11:46:52 PM

Check this out its a serious university report on running a lister 6/1 on vegoil with 3 simple modifications.  Personally I think it is flawed.  They make a preheater out of the CS bung to increase the fuel temperature to 90 degC just before it enters the injector.  I dont believe this is of any benefit at all.  They have a thermostat on the engine and they do all their testing when the engine is up to 90 deg C. Not once do they ever do a test without preheating the fuel even when they don't use their fancy preheater they use electric heating on the injector pipe.  How can they know if it makes any difference when they haven't tested it with no preheating?

In their report they increase the injector pressure and adjust the timing. They recommend 15Mpa injector pressure which is 148 atmospheres. This is nearly the same as the injector pressure for the 16/2 engines see excerpt from 1971 Lister manual. They also advance the injection to 25 deg BTDC which again is similar to the 16/1 setting.


Title: Re: injector
Post by: glort on April 08, 2020, 01:24:12 AM

I don't think there was anything in that study that was not already Known on veg oil forums well before the study was done.
I remember loads of these university types coming on sites like info pop with long lists of questions wanting people to do their Thesis for them.

It was well known way back that veg burned slower than Diesel and advancing the timing was helpful. Only had to go out and play with the timing on your car to see that. Was enough to fall within the sensitivity of the Butt Dyno and a stop watch quite easily.

The study as I see it fails in a major way in that they didn't test individual variations in the modifications they made. They seemed to have the idea that this "kit" as they called it of doing 3 things was going to work and wanted to prove that. They didn't seem to test each factor nor in pairs to even see if one was making a difference and how they worked in conjunction

They also made mention many times of making modifications to suit the 3rd world but then went on with a lot of 1st world concerns like Co levels and opacity of the exhaust.  Something no Indian farmer could give 2 hoots about.

To me if they don't test the before and after of every modification on it's own and then pair them up, you never know if one change is working or not or if another is detrimental and the other change is covering that and still showing improvement.

At the end of the day these tests can be interesting but it has to be remembered they are just a bunch of uni kids trying to demonstrate a theroy.
The amount of other work quoted in this study must have cut down their time and effort considerably.
Title: Re: injector
Post by: veggie on April 08, 2020, 03:24:06 PM

One thing that they did state lower down in the article...

"All parameters point toward an optimized tuning of the injector timing at 25 BTDC with an IVOP of15MPa."
Title: Re: injector
Post by: glort on April 09, 2020, 03:05:16 AM

One thing that they did state lower down in the article...

"All parameters point toward an optimized tuning of the injector timing at 25 BTDC with an IVOP of15MPa."

Was it you that recently wondered about if your timing was too advanced with the wrong timing marks?
Probably not as much as you thought!

Title: Re: injector
Post by: veggie on April 09, 2020, 09:46:52 PM

Nope. That was not me.
Although my wife would argue that I'm not as advanced as I thought.  ;D
Title: Re: injector
Post by: glort on April 10, 2020, 03:33:21 AM

Nope. That was not me.
Although my wife would argue that I'm not as advanced as I thought.  ;D

Your wife sounds very kind and caring. Must be a lovely lady.

My wife just knows just enough about engines not to put it so subtlety.

She would just say I'm retarded!   :embarassed:
Title: Re: injector
Post by: veggie on May 26, 2020, 09:47:34 PM
Back to the original question....
This lab test shows that the optimal timing and injector pop pressure for a 6/1 Listeroid burning WVO is.....

Timing : 25 Deg BTDC
Injector Pressure: 15 MPa

Below is the report.
Title: Re: injector
Post by: glort on May 27, 2020, 09:05:48 AM

From what I can deduce from the test, those setting are optimal for emissions only. They, from what I can see, never measured power or even mention it.  Their sole parameter of testing was single point and emissions concerned only.

They also make a number of other conclusions amounting to variable loadings and RPM gave very different results.  Much to my surprise they  not that heating the oil gave improved results in SOME load points and even more curiously, indicate that at others the " Modified" Fuel as they put it actually performed 1% worse.  I can't see how heating oil improves anything and I certainly can't see how it could make anything worse but then again, I only look at power and starting  and have never looked at emissions or give a Damn for that matter.

I don't see where there is concern when one is using a Renewable, " Natural" fuel to start with. Their conclusion was diesel was over all the cleanest fuel.  It's worse in some things and better in others but by their testing, it did have the lowest emissions over all.

I am still completely unconvinced that heating the oil before it goes through the injector let alone the fuel pump as is common practice can have any  effect on emissions or power/ output.  It may have an effect IF it was injected hotter but I fail to see how that can be when an injector is buried in the lump of metal the head is and the thermal conductivity between the two. I would have to see something that convinced me the injector was capable of running at a different temp of some substantial amount than the head it's buried in during sustained load on an engine that has been running long enough to heat soak completely.

I remain thoroughly convinced that the greatest asset in running WVO in a standard engine is the addition of 5% Petrol to the oil for the exact reasons the report addresses.

It lowers Viscosity and improves the spray pattern which is what they were testing with heating the oil and the running the higher injector pressures.
It improves starting by making the fuel easier to light off. Something they noted several times in relationship to Diesel Vs. Veg.
It brings the timing forward and closer to the light of characteristics of Diesel which again improves starting and running performance.
No doubt these improvements which are the same as they were trying to achieve with the mechanical modifications would also help emissions if one were concerned about that.

While Listers are easy to change timing and injection pressures on ( for the little and variable that was worth) many other engines particularly small engines are not and the addition of 5% Petrol can have all the desirable benefits with very little effort. In my experience with a variety of engines from small industrial to a variety of Vehicles, the The starting improvement ULP makes in cold weather starting is huge.  In the winter months the ULP ratio can be Bumped as high as 15% ( Some say 20 But I find after 15% there are undesirable side effects)  to help that even more.

My recent experience with my little 3Cyl Diesel showed harder starting on straight oil even in the warmer months but the addition of 5% ULP had it starting every bit as easy as if it were running straight diesel, perhaps fractionally better. That said I tend to like an engine to have a few cranks before lighting to reduce or eliminate the time it is running before the oil pressure comes up.

While I certainly believe bringing the timing forward on engines running WVO is a sure benefit, I remain unconvinced of the benefits of fuel heating ( over around 30oC to melt any fats through filters) and IP pressure increases. The report seemed to find the heating and IP pressure increase had variable and minimal benifit at best and only on the emissions they tested for.
Power nor ease of starting was not mentioned that I saw.