-
Will a lift pump affect timing?
by
Alcaid
on 05 Oct, 2011 04:18
-
Hi,
Is there a reason not to use a lift pump on our VE pumps as they do on the TDI engines? (VE, PD, CR) Will it affect timing and advance it too early in any way? Timing is controlled mechanically in our pumps and not electronic as on the TDIs so there might be an effect with higher input pressures?
-
#1
by
burn_your_money
on 05 Oct, 2011 06:41
-
It will have no effect on advance. Just make sure you don't use too high of a PSI lift pumpand blow out your pump seals.
-
#2
by
Mark(The Miser)UK
on 05 Oct, 2011 07:13
-
Hi,
Is there a reason not to use a lift pump on our VE pumps as they do on the TDI engines? (VE, PD, CR) Will it affect timing and advance it too early in any way? Timing is controlled mechanically in our pumps and not electronic as on the TDIs so there might be an effect with higher input pressures?
I thought the lift pump would alter the pressure diff across the advance system.
Why not cure the pump's pump, after al it's only a vane pump, and I bet the vanes can be reversed if damaged, just like the vac pump.
-
#3
by
Alcaid
on 05 Oct, 2011 09:40
-
I thought the lift pump would alter the pressure diff across the advance system.
Why not cure the pump's pump, after al it's only a vane pump, and I bet the vanes can be reversed if damaged, just like the vac pump.
Fixing something that isn't broke will not solve anything...
I was thinking of adding a lift pump to help the pump maintaining the proper advance up to 6000rpm. I've seen VP pumps failing to do this even up to measly 4500rpm without a lift pump and I feel the VE pump on my 1.6TD is failing to maintain advance at high revs (governor main spring shimmed solid) but haven't been able to check it (Vag-Com logging sure is useful, but not an option on our 1.6TD...
)
-
#4
by
8v-of-fury
on 05 Oct, 2011 09:55
-
I have a 6psi electric pump feeding my 1.6 n/a and 5500 rpm's are no problem.. Obviously with a non-turbo there isnt a ton of power up there.. but with my straight pipe exhaust it sounds AWESOME.
-
#5
by
R.O.R-2.0
on 05 Oct, 2011 13:34
-
i got a small lift pump, and i could tell the difference in the top end after i installed it.. its alot better than just having a suction feed, and it makes your filters last longer..
-
#6
by
Mark(The Miser)UK
on 05 Oct, 2011 15:22
-
I thought the lift pump would alter the pressure diff across the advance system.
Why not cure the pump's pump, after al it's only a vane pump, and I bet the vanes can be reversed if damaged, just like the vac pump.
Fixing something that isn't broke will not solve anything...
I was thinking of adding a lift pump to help the pump maintaining the proper advance up to 6000rpm. I've seen VP pumps failing to do this even up to measly 4500rpm without a lift pump and I feel the VE pump on my 1.6TD is failing to maintain advance at high revs (governor main spring shimmed solid) but haven't been able to check it (Vag-Com logging sure is useful, but not an option on our 1.6TD... )
Why not install a weaker advance spring, then the pump doesn't need to be overloaded with high internal pressures, to get the same advance?
We are lucky over here as we don't get water in the diesel. 
and so filters last.
-
#7
by
ORCoaster
on 05 Oct, 2011 16:53
-
Weaker spring would be my fix. There is a line of them that are color coded and the green one is the weakest therefore it gives the top end advance sooner or at lower pressures. You really have to gauge the IP to see what the pressures are at all cycles of the system before you can fix a lack in the advance at higher pressures. There are shims in that cover of the advance, have you played with that mod?
There is also only a certain amount of advance you can get. I think it is stated someplace here either 24 degrees or 12 not sure on that number. If you have good top end pressure and still lack advance I would be looking at the pump rebuild. Something is worn out and not moving the cam plate as it should to advance the injection time.
-
#8
by
fatmobile
on 05 Oct, 2011 20:49
-
I've wondered this too.
The low pressure side of the timing advance piston is connected to the front of the pump,..
so if the internal pressure is 6 psi higher,
and the pressure at the front of the pump (and other end of timing piston) are 6 psi higher too, then nothing would change.
-
#9
by
ORCoaster
on 05 Oct, 2011 21:35
-
I really don't think a low pressure pump pushing fuel into the inlet is going to change the timing much. Ever notice that it takes a pretty good change from idle to get the little bit of advance the cold start lever gives? I remember that the few degrees you get from pulling on the start lever is negated as soon as you get somewhere beyond 1200 RPM. Don't quote me on that but it is low. Now if the normal pressure in the IP at idle is supposed to be 43 psi and at 2000 RPM it is 74.5 then in the middle at about 58 PSI you are already advancing like the start lever.
I run a gauge and I can tell you that it is pretty quick to jump to 55 PSI as you upshift. Keeping more fuel coming into the pump under pressure instead of relying on a pull from the pump may help that jump happen sooner but I don't think you will even notice it. I doubt that once the internal pressure at idle is produced that there is an additive effect going on. It overrides the inlet pressure from that low pressure pump.
In the fire business we rely on pumps a lot and staging pumps in line allows us to move water long distances or produce high pressures. Depending on how and with what pumps. Some are built for volume others pressure. I am thinking this adding a low pressure pump to the front side of the IP is similar to how we would try to combine pumps to keep up with a high demand on the system down the line. You can starve a pump if the pressure is to low from the first but I don't think that is the situation here. Having the first pump producing more pressure didn't add to the final output either. It was/is limited by the rotation of the second pump. In our IP that is the vane pump.
-
#10
by
Alcaid
on 06 Oct, 2011 05:31
-
The reason why I want to add a lift pump is not the get the timing advance sooner as some of you write about, but rather maintaining it at the top rpm range were these pumps tends to starve and internal pressure drops.
-
#11
by
Mark(The Miser)UK
on 06 Oct, 2011 06:18
-
The reason why I want to add a lift pump is not the get the timing advance sooner as some of you write about, but rather maintaining it at the top rpm range were these pumps tends to starve and internal pressure drops.
Sounds reasonable, but I thought the govenor limited the max rpm.
As pump operates under an excess of fuel, would the late mk2 fuel bypass back to the filter rather than back to the tank not help that?
Then there is my belief that dropping the internal pressure of the pump coupled with a weaker advance spring, would get you all the advance needed, and less bursting pressure on the pump seals, less loading on the internal lift pump etc.
Check 'my' graph to see that the internal pressure of pump v rpm is linear over a large range of idle pressures...
-
#12
by
Alcaid
on 06 Oct, 2011 06:51
-
Have you logged case pressure doing a WOT run from 1500-2000rpm to ungoverned redline? Thats' when you see it dropping. I've seen it on several TDI pumps without lift pump and I don't see a reason why the VE pumps would act differently.
-
#13
by
Mark(The Miser)UK
on 06 Oct, 2011 07:05
-
Have you logged case pressure doing a WOT run from 1500-2000rpm to ungoverned redline? Thats' when you see it dropping. I've seen it on several TDI pumps without lift pump and I don't see a reason why the VE pumps would act differently.
Er nope
I don't do wide open throttle stuff 
My testing was confined to gauge readings upto 3500 ish under no load, as I have my head under the bonnet[hood] to read the gauge on a 9" length pipe with one eye whilst the other eye logs the digital readout on my strobe box, so you could be right 
-
#14
by
R.O.R-2.0
on 06 Oct, 2011 07:35
-
why do the dodge guys use lift pumps instead of weaker springs?
im still gonna say that a lift pump is better than a weak spring. the pump is being PRESSURE FED fuel, it doesnt have to make suction on its own.. that allows my stiff spring to advance sooner than a weak spring. because if the vane pump doesnt have an available excess of fuel, then it cant start advancing till it has enough fuel present to raise the internal pressure..