Flat spots running Veg?? read on >>>>

[Mattcheese31]

Even if there's no leaks it'll pull timing, because the veg is thick, the pump will struggle to pull it up the lines, lose pressure, bam timing gone... Air makes things even worse!

Thing is, it's got to pull it through the filter, the housing, through the strainer in the tank and all the lines back there, hardly surprising!

indeed, all the more reason for feeding the throttle in progressively too, lol, it's not easy to drive one of these beasts properly

[nominous]

If the dynamic advance operates on the pressure differential, should the thicker fuel therefore not mean lower pressure and more advance ? - in an ideal world where supply is not an issue.
Is it therefore just that it's more a lack of fuel which is the problem causing the drop in advance?

I'm wondering if an inline pump on veg would help you get that timing back again.
But a fine line between that, the temperature of it and the pressure difference at the pump.

Certainly heating it makes a massive difference. I use a FPHE and a electrical supplement heater in the TDI.

If/when I get a 306, I have a few ideas I'm going to try out at any road.
Probs including mapping IPP against RPM and throttle on derv and veg.



Tom, would solenoid control over the pressure valve and thus your IPP give you any top end advantage ??
Say with the addition of forcing the fuel in with a lift pump and backing off pressure at low revs.
You could add IPP control into the electronics - forgive me if you're doing this already. - I guess why you wanted to try an electronic pump

[THE_Liam]

I'd love to see a measure of the viscosity of WARM veg and diesel.

[nominous]

Soon as the pump begins to drop internal pressure due to sucking veg, you INSTANTLY drop timing, it's a finely balanced system that if there's any suction going on, it'll instantly retard the pump back to base timing.

As far as I can see, soon as you start running veg - bam you've probably lost 5* of timing midrange, by the time you're past 3800rpm, it's struggling so bad to get fuel, the timing is right back at stock position.

So to come back to this....
With veg, part of the issue is using up the fuel and not being able to replace it as quickly than with diesel. So how to cure?
One option is heating it to reduce the viscosity. The downside of doing this is that it will over time make your fuel lines and the inside of your pump look like a chip pan.

So I'm coming back to what I wrote above:

If the dynamic advance operates on the pressure differential, should the thicker fuel therefore not mean lower pressure and more advance ? - in an ideal world where supply is not an issue.
Is it therefore just that it's more a lack of fuel which is the problem causing the drop in advance?

Still pondering if it's worth while trying to maintain IPP using an inline pump to boost the pressure on veg. A very low pressure but something that doesn't cause the pump to rely on sucking the veg up. I've experienced the difference that it makes whilst faffing around on the corsa with a pressurised fuel container.
Doesn't always have to run, could just be on WOT at higher revs.


Oh and the next proper build for veg is having an engine bay insulated swirl pot and hard lines. I'm done chasing air leaks and having starvation.

[r3k1355]

I'd love to see a measure of the viscosity of WARM veg and diesel.

Must be some homebrew/garage science way to do it.

Like run a gallon of it from one container to the other using a thin pipe.
Time how long it takes each one to drain through and make an approximation of the % change.

or something.

[Ruan]

Best option really is to use a lift pump to draw your fuel of choice to a swirl pot as CLOSE to the injection pump as possible - you can then allow the overflow back to the tank and your injection pump feeds from the swirl pot.

This also means you can pre-heat the oil in the swirl pot if so desired.

This way you don't have the problems of applying pressure into the fuel pump, any excess pressure is simply bled back to the tank, since that only ever ends in problems, since positive pressure increases advance, you end up shifting the advance curve lower in the rev range. Just ensure your return line if of a bigger diameter than your feed line, that way you can guarantee there'll never be pressure build up in the swirl pot.

[welshpug]

guess the VP pumps work a little differently as my BMW does use a lift pump, albeit at only 5-6 psi.

[Ruan]

Yeah, they can do because they have the internal pressure fed to the timing piston by a PWM solenoid valve with feedback, so it will adjust itself accordingly even if case pressure changes.

VPs/yours will have the pressure regulator jammed in all the way.

[Dum-Dum]

10mm fuel lines stops it holding back and hesitating when your at full load/throttle in the upper gears.

[Mattcheese31]

10mm fuel lines stops it holding back and hesitating when your at full load/throttle in the upper gears.

I've heard that before mate, never looked before, are they easy enough to run the pipes?

[Chris_90]

10mm fuel lines stops it holding back and hesitating when your at full load/throttle in the upper gears.

I've got 10mm lines and it still holds back / hesitates on a long pull. 

[Mattcheese31]

10mm fuel lines stops it holding back and hesitating when your at full load/throttle in the upper gears.

I've got 10mm lines and it still holds back / hesitates on a long pull. 

yeah but you run yours on sludge don't you Chris? Lol

[Dum-Dum]

10mm lines are VERY easy to run. Just get 5-6mm of 10mm fuel line, some jubilee clips, a 10mm priming grenade, a 10mm (3/8ths) fuel filter and the appropriate banjo for the bosch pump. Also some 10mm PVC pipe and a 10mm joiner if you want to have a clear bit to check for air in the system.

The outlet on the in tank pick up is actually very close to 10mm anyway so you can just clamp the pipe onto that and run it under the car and up to the bay next to the return line with a ton of cable ties.

You could probably do it in an hour, certainly under 2.


On my 2.1 it used to suffer terribly with holding back till i swapped the lines and it never happened afterwards even on nearly pure veg. That must of been close on 200bhp with the VNT

[Mattcheese31]

5-6mm???

[Chris_90]

10mm fuel lines stops it holding back and hesitating when your at full load/throttle in the upper gears.

I've got 10mm lines and it still holds back / hesitates on a long pull. 

yeah but you run yours on sludge don't you Chris? Lol

No 90% wvo 10% petrol normaly but I'm on 100% new ktc oil at min. No sludge involved......

[Mattcheese31]

I've got 10mm lines and it still holds back / hesitates on a long pull. 

yeah but you run yours on sludge don't you Chris? Lol

No 90% wvo 10% petrol normaly but I'm on 100% new ktc oil at min. No sludge involved......

that ktc isn't very good tbh mate, cheap yeah but does run lumpy

[Chris_90]

yeah but you run yours on sludge don't you Chris? Lol

No 90% wvo 10% petrol normaly but I'm on 100% new ktc oil at min. No sludge involved......

that ktc isn't very good tbh mate, cheap yeah but does run lumpy

It don't start lumpy it's nice and smooth, just under prolonged pull it lacks in power/miss's, not to fussed it's only when I'm on bypass on normal roads never affects me.

[Mattcheese31]

Soya bean oil equals poo poo

[Chris_90]

Soya bean oil equals cheap running  

Edited for you

[Mattcheese31]

Soya bean oil equals cheap running  

Edited for you

I know lol, not the best though by a fair whack

[Chris_90]

[quote pid='496842' dateline='1417980568']

Soya bean oil equals cheap running  

Edited for you

I know lol, not the best though by a fair whack
[/quote]

Ahhh couldn't give a toss tbh what ever is cheap goes in tank normally I'm paying 25ppl unfiltered wvo but to cold at min to be filtering so I stick the cheapest new stuff in, if I had the money tho I'd buy the 1000litres of new rapeseed off ebay for £450.

[nominous]

since positive pressure increases advance, you end up shifting the advance curve lower in the rev range.

Missed the bit about running it only at WOT or indeed higher RPM's only.
I've not tried it, but since it can be difficult to get fuel in at high RPM's within the injection window, pressure makes some sense at first glance.


Having run several hundred thousand miles on veg in a variety of cars, the swirl pot is the future for me.
It cuts away all the crap with hoses that will leak given time. As I expect to use hard lines to the pump from it.
Return back to the pot from the IP to keep the warm veg circling.
lift pump on a float & timer to get the thing topped up but not constantly cycling, also allows it to maintain heat.
Return to tank very high up and only used under some dire circumstance and for venting air.
Pot will be mounted on the engine somewhere to make hoses and heating easier.

[Ruan]

It doesn't really matter if it runs at high RPMs or not... You want to keep the advance curve in check all the time, it's a major component to how the engine runs and it's efficiency - people just assume because it's running, the curve is there, but soon as there's any sign of struggling for fuel, the advance is the first thing to drop, literally, the slightest suction will cause a massive drop in case pressure and pull timing off - which is the difference of the advance curve starting to come in at 1500rpm or say 2500rpm - that whole time the engine will be running badly, let alone the increased ignition delay of veg oil... You need more timing to compensate, but just not at the wrong RPM!

Some day when I'm bored and have time, I'll fit the needle lift feedback system off a later XUD with the electronic advance system and measure the advance curve... You want to have the least restriction without adding positive pressure IMHO.

[nominous]

I think we are talking at crossed purposes. I do get all of this fully.

The lift back system, can this be run on a normal mech pump without a problem?
Whilst I was going to grab the TPS sensor, I would really appreciate a way of measuring the advance position, and the LDA for that matter.
I can add all of them into the extension board I have for my LM1 and graph it.

[Ruan]

I think we are talking at crossed purposes. I do get all of this fully.

The lift back system, can this be run on a normal mech pump without a problem?
Whilst I was going to grab the TPS sensor, I would really appreciate a way of measuring the advance position, and the LDA for that matter.
I can add all of them into the extension board I have for my LM1 and graph it.

No reason you can't add the needle lift sensor, you'd need to put in the later style flywheel also for crank position, but I've never seen anyone recalibrate the ECU for them, so no point in running that.