80 series pump, overboost??.......

[vn15]

The truck is an 80 series 4.2 1HD-T. It has adjustable boost, and fuel wound up to max, so next is removing the pump and have it modified.

Anyway, to night I was out testing.

Boost was set to 1.5bar, only for this ride.
And the ting is that it reached 1.5bar at 2500rpm, then the boost/power slowly decreased as it climbed towards 3000rpm, it ended at only 0.95bar

is the pump built like this, that it decreases fuel delivery at higher revs? Can something be done to overcome this, or is it a job for a qualified diesel mech only

[+dj_hansen+]

You will probably find that the turbo is well out of its efficiency range, pumping hot air, which is less dense, therefore the pressure is dropping. Assuming you are measuring boost at the inlet manifold, not on the outlet side of your boost control before the waste-gate actuator.

[Die Tryin2]

Boost is relative to fuel being delivored a turbo wont react if theres not a heap of fuel id be going to a specialist rather than mucking around with it, you might make it worse. just my 2 c

[vn15]

Boost is relative to fuel being delivored a turbo wont react if theres not a heap of fuel id be going to a specialist rather than mucking around with it, you might make it worse. just my 2 c

Thanks for answers. I am leaning towards the pump not able to deliver enough at higher revs.

[Die Tryin2]

Before you spend big bucks taking it to a specialist check and renew your fuel filter/s if you have access and know what filter you need, if you have a slight restriction to your pump it will be fine at low to mid rpm but at high rpm the 'primer pump' that supplies your cant deliver all the fuel the engine needs at high rpm thus reducing the actual fuel delivered in each cyl fire and will decrease your boost as stated before boost is relative to fuel. Let me know how you go.


BTW sorry about the lecture and explaining everything i just prefer to get as much info out as i can in one post rather than having to string a whole heap along, cheers.

[MR Duck]

You will probably find that the turbo is well out of its efficiency range, pumping hot air, which is less dense, therefore the pressure is dropping. Assuming you are measuring boost at the inlet manifold, not on the outlet side of your boost control before the waste-gate actuator.

Sorry in advance about the long winded dribble... a lot of fuel aneroid’s will pull back the fuel in an over boost situation, like the 22 psi that you are trying to extract from your turbo, a spacer can be installed to stop the aneroid from over travelling but be aware that if you pull it out mark the position of the diaphragm relevant to the housing as the pin is an eccentric taper and if rotated in a different position you will change the ramp rate of fuel at given pressure this can be good if you have a pyro or bad if you don't and melt your internals
**** Warning this little pin when pulled out may have to have a bevel ground on the bottom on one side to get it back in!!! the little pin that pushes on it is spring loaded ****
even after a spacer is installed my experience with a 1HD-FT is still similar (slightly different turbo) the CT26 turbine although quite large is quite restrictive when compared to the GT2871R that is now on mine even with a .64A/R housing, physically a much smaller turbo to look at but the proof is in the testing with out touching any thing else the garrett boost would hold through till 4000 with lower EGT's than before. With the .86A/R flow is improved still, however the loss in bottom end was more than I was happy with so will stick with the .64, took notes of pressure vs rpm under load and found that they were almost identical as far as initial spool up pressure at a given rpm (Auto with brakes on loading up stall converter (would not recommend this) brakes wont hold vehicle in 4wd and brakes traction in 2wd with rear diff lock on tar seal at boost over 10psi with lpg on) with next to no loss at top end, where the CT 26 would go from 15psi at 3000 to 10psi at 4000 Exhaust temps are now lower at the top end than mid range which means I could increase my fuel but will try changing the gas rather than the diesel but that is another story……….
So like +dj_hansen+ wrote your turbo is probably out side it's efficiency range and beyond its RPM limit.

[vn15]

You will probably find that the turbo is well out of its efficiency range, pumping hot air, which is less dense, therefore the pressure is dropping. Assuming you are measuring boost at the inlet manifold, not on the outlet side of your boost control before the waste-gate actuator.

Sorry in advance about the long winded dribble... a lot of fuel aneroid’s will pull back the fuel in an over boost situation, like the 22 psi that you are trying to extract from your turbo, a spacer can be installed to stop the aneroid from over travelling but be aware that if you pull it out mark the position of the diaphragm relevant to the housing as the pin is an eccentric taper and if rotated in a different position you will change the ramp rate of fuel at given pressure this can be good if you have a pyro or bad if you don't and melt your internals
**** Warning this little pin when pulled out may have to have a bevel ground on the bottom on one side to get it back in!!! the little pin that pushes on it is spring loaded ****
even after a spacer is installed my experience with a 1HD-FT is still similar (slightly different turbo) the CT26 turbine although quite large is quite restrictive when compared to the GT2871R that is now on mine even with a .64A/R housing, physically a much smaller turbo to look at but the proof is in the testing with out touching any thing else the garrett boost would hold through till 4000 with lower EGT's than before. With the .86A/R flow is improved still, however the loss in bottom end was more than I was happy with so will stick with the .64, took notes of pressure vs rpm under load and found that they were almost identical as far as initial spool up pressure at a given rpm (Auto with brakes on loading up stall converter (would not recommend this) brakes wont hold vehicle in 4wd and brakes traction in 2wd with rear diff lock on tar seal at boost over 10psi with lpg on) with next to no loss at top end, where the CT 26 would go from 15psi at 3000 to 10psi at 4000 Exhaust temps are now lower at the top end than mid range which means I could increase my fuel but will try changing the gas rather than the diesel but that is another story……….
So like +dj_hansen+ wrote your turbo is probably out side it's efficiency range and beyond its RPM limit.

Good reading mate Yep will get a new roller turbo. Do you put this spacer under the diaphragm, and how thick does it have to be Am avare of the little spring loaded pin, must be careful not to drop it.

Will check the fuelfilter also, are there another filter/ a screen in the pump somewhere . I know Nissan Patrols has one.

Thanks

[MR Duck]

Good reading mate Yep will get a new roller turbo. Do you put this spacer under the diaphragm, and how thick does it have to be Am avare of the little spring loaded pin, must be careful not to drop it.

Will check the fuelfilter also, are there another filter/ a screen in the pump somewhere . I know Nissan Patrols has one.

Thanks

The spacer is custom made to suit your pump so as to stop the diaphragm/pin at the dead band part of it's stroke (there is a small parrallel section just before it ramps back out) you will need to do some measurement to work out how thick it needs to be, putting a thin smear of grease on the taper, push down on the metal disc that is on top of the diphragm by hand a couple of times will allow you to see the point that it stops at, the spacer is a clearence fit over the taper pins largest diameter and sits inside the large spring
the smaller pin will not fall out but rather has spring pressure that holds it out and stops you from putting the taper pin back in, the bottom of the taper pin is relativly flat and the small pin sticks out inside the bore hence the carefull butchering of the bottom of the taper pin..... with the small bevel ground on one side (the side with the shortest taper gives you more room and the bevel can be quite steep) line up the small pin and gently rotate back and forth til it pops in thin smear of grease will help. Take your time and think about what you are doing and you will be fine
Put a small mark on the metal disc on top so you know where the long taper is as a max point, 180 deg either direction from there will take it to the minimum point of influence
The long taper side of the pin towards the small pin will give earlier fuel increase and more full boost fuel (the small pin out is max increase full in and the aneroid has no effect on the fuel pump)
Have fun......Oh and don't stuff with the pump without a pyro fitted and it is usless if you don't keep an eye on it!!

[80's_delirious]

Awesome info there Mr the Ducks guts.

Ive been running 18psi and up to 22psi on my 1HD-T for a couple of months and been struggling with tuning. Keep hitting a bad flat spot around 3000rpm.

The hose to the aneroid blew off one day and suddenly the flat spot was gone

Ive been scratching my head as to why the aneroid/boost compensator was reducing the fuel delivery.
will have to look at setting up a spacer. Have been sure the boost compensator should help deliver a more consistent fuel load across the rev range