The Official 1HD-T/FT Fuel Pump Mod Tuning Thread (3 Viewers)

[Douglas S]

Off-boost performance is controlled by the "smoke screw" cam adjustment on the boost compensator lid, and once boost starts building it builds quickly. You could use shims to alter the starting depth of the pin in the compensator body if need be.

I'm working in theory as I've not yet dug into my pump tuning, but I think having some tuning resolution would be more important in the 10-25psi range than in the 0-10psi range due to variance of air volume and the fuel requirements that would follow. I guess I've got to get to playing with it to gain some context.

I can totally understand why you'd do this on an electronically controlled injection pump, but why introduce limitations like this on a mechanical one?

That AFC Live setup looks amazing, @Wheelingnoob has one on his Cummins swap and had good things to say about it. I wonder if it could be adapted to our pumps?

AFC Live works on Cummins VE pumps so I expect it would work on a 1HD-T/FT considering they use a similar pump design just scaled down. I'm far from an expert on the subject though. As far as I can tell from browsing Cummins forums AFC is synonymous with boost compensator.

 

[vwluv10338]

Yes, our boost compensator is what they call the AFC. I would think the Live AFC would just be varying the pressure the boost comp sees. I can't imagine it would do anything else. What @GTSSportCoupe is talking about with a linear bleed valve was my first understanding before I probably starting overthinking and going down the wrong path. Staying out of fuel cut my showing your engine lower than actual boost either mechanical or electronic I would think would work in the same fashion.
I understand what you are saying @IanB about controlling the off boost fuel via the smoke screw but that really controls nothing other than the starting point on the fuel pin curve for your off boost fuel. Once boost starts to build to 1-3 psi we want the pin to star moving like in Graeme's tuning guide. If we increase the spring tension a ton to stay out of fuel cut then isn't the spring tension going to keep the rod from moving until much more than slight boost? Obviously I am no expert because I have been messing with my pump for only a few days. Using a linear bleed valve would allow the rod to move earlier or maybe it bleeding off boost would be the same as extra tension on the spring.

 

[vwluv10338]

AFC Live works on Cummins VE pumps so I expect it would work on a 1HD-T/FT considering they use a similar pump design just scaled down. I'm far from an expert on the subject though. As far as I can tell from browsing Cummins forums AFC is synonymous with boost compensator.

View attachment 1483741

I have been unsuccessfully trying to find one for sale or the dimensions of their boost comp lid as they have a bolt vs our cam plate. I wondered if it could work on our pump

 

[diby 2000]

While @vwluv10338 is correct, more spring tension does delay the pressure where the aneroid begins to move there is another crucial aspect I don't think you have thought about. That is once you are running more boost (>10psi) to utilize that boost you have to add fuel. The volume of fuel that you have to add is generally more than what you can get bu just rotating the aneroid to a deeper grind, so the extra fuel potential comes from the max fuel screw.
When adding fuel with the max fuel screw, more fuel is delivered right across the range, including no boost. This means that now you are running richer than ideal (some smoke) when flat to the boards with no boost. The way to fix that is to get the follower pin riding on a larger section of the aneroid or add some boost without adding any extra fuel. Once the boost level matches the spooling fueling level, then you want the aneroid to begin to move to continue adding fuel to keep the spooling going. So delaying the aneroid movement until a couple of psi of boost is already happening is actually a good thing.
I think my aneroid begins to move at about 3-4psi right now. I'm only running a crude tune right now but with enough fuel for 24:1 @ 32psi, I can see 14-15:1 if I mash the throttle with low rpm and no boost (with the TPS fooled). This then leans out to about 17:1 then stays around that number as boost is building.

I will have to investigate that AFC Live, but I assume it will be similar to the diagram on the last page with adjustable flow restictor and bleed valve.

 

[vwluv10338]

@diby 2000
I get the paint the pin and boost to tell if you are into fuel cut but how are you supposed to tell when your pin starts to move? Graeme's tuning guide doesn't tell you that. Also, then wouldn't less pretension on the spring but a custom grind with a longer and taller ramp be better? I guess that's why people grind their pins but even the one in Graeme's guide doesn't look like it went up much further than the aggressive side of the stock pin.

Edit:
Also, for some reason I have been stuck on getting the pin to move quickly but after looking at the stock pin it has quite a lot of travel where it could be pulling fuel before it hits any sort of ramp. So say with less spring tension that it starts moving at 1 psi but it rides up the full circumference part and doesn't hit the ramp till 5 psi anyway. Now we add tension for increased boost and it doesn't move at all till 5 psi but we have adjusted it down via the snake screw where it was sitting right at the edge of the ramp so at 5 psi it gives more fuel anyway.

 

[IanB]

This is where the old adage that "tuning mechanical injection pumps is a black art" rings true, search as you may, you won't find a lot of old info on tuning the pumps on these engines, we borrow from what has worked on other platforms with similar pumps, but we really are pioneers as strange as that seems on ~25 year old trucks.

Make changes, test, observe, make changes, rinse, repeat.

 

[vwluv10338]

I'm a new school mechanic. I'm used to working with a laptop and a data list with 6 pages of data. Driving and recording data snapshots. There are only a few old heads left in my shop that remember tuning carburetors.

 

[mudgudgeon]

@diby 2000
I get the paint the pin and boost to tell if you are into fuel cut but how are you supposed to tell when your pin starts to move? Graeme's tuning guide doesn't tell you that. Also, then wouldn't less pretension on the spring but a custom grind with a longer and taller ramp be better? I guess that's why people grind their pins but even the one in Graeme's guide doesn't look like it went up much further than the aggressive side of the stock pin.

There is a limit to how far the pin can travel.
See my dimensions drawing a few pages back.
The stock pins do not use the full range of movement available.
Graeme's guide you posted shows vernier calipers on the length of the pin, and a red mark at the top. I suspect his intention here was to grind the pin so the new length is adjusted so the follower is starting on the full diameter of the pin, but as close to the start of the ramp as possible.

 

[mudgudgeon]

This is where the old adage that "tuning mechanical injection pumps is a black art" rings true, search as you may, you won't find a lot of old info on tuning the pumps on these engines, we borrow from what has worked on other platforms with similar pumps, but we really are pioneers as strange as that seems on ~25 year old trucks.

Make changes, test, observe, make changes, rinse, repeat.

I couldn't agree more.
There's more than one way to achieve the same result. Several variables all interact and depend on each other.
Understanding what the individual adjustments do helps, then there is a lot of trial and error.

Greame's guide I think is attempting to give you a base line that is close to a decent tune. There's still going to be tweaking.

 

[mudgudgeon]

I'm a new school mechanic. I'm used to working with a laptop and a data list with 6 pages of data. Driving and recording data snapshots. There are only a few old heads left in my shop that remember tuning carburetors.

God, that makes me feel old!

I played with carburetted v8's when I was young and stupid, now that I'm old and silly, I'm playing with mechanical diesels

 

[diby 2000]

I couldn't even afford a carby V8 in my misspent younger days. Carby inline 6 (in a cortina with a manual box) was my first and only carburetted vehicle. Even then I had heaps of trouble tuning the carby in it.

 

[vwluv10338]

So I drove over the mountains to go camping this weekend in what should have been a 2.5 hour drive. I added an extra hour to our time, calculated by a very forgiving girlfriend, by stopping at least 6 times to change my tune on the way. It actually worked out really well where I could hit some sustained climbs and then pull over and make some changes. I did have an "oh sh!t" moment when all of a sudden I could no longer boost over 7psi. My EGTs were fine but it just wouldn't boost. I pulled over and my idle was surging some. Luckily whole checking it out I saw the lock nut on the smoke screw just slinging around with the engine vibrations. I guess I hadn't tightened it enough and it let go. Therefore my fuel rod wasn't moving and the boost line for that is where my T for my boost gauge is. Tightened it back up and I could hit 20psi again. I quoted IanB's post because that seems to be where I got my tune. My last trip I could end up slowing down on some hills with the pedal to the floor. Now I could push the pedal down a bit to maintain my speed and watch the temp climb to around 1150F at 15psi. If I stepped on it I could get 20psi and 1300 but I would just back off. I need to paint the fuel pin and check if I'm in fuel cut still but I just made a bunch of changes on the fly and ended up reducing main fuel but going to the more aggressive side of the rod. Cruising EGTs are up a bit at 800's so I might try to turn the fuel down some and not loose any low end or just leave it till I finish my exhaust and intercooler.

OK, that's not a "max EGT" reading, that's a highway cruising EGT reading. Totally different things.

I had my truck in the mountains last summer, and with my current tune it was easy to keep the EGT's below 1250F up mountain passes with my right foot, but it would exceed that if you stayed in it and weren't watching. Now that I'm back home on the prairies, I can't get it to 1050F without staying into the pedal trying to see what my top speed might be. Cruising at 110km/h at about 16psi lands me around 850F if memory serves me, stock turbo, no intercooler.

600F at 110km/h on the prairies with an intercooler is reasonable I think. Sustained climbs heat soak the system, I'm talking several minutes at a time pulling up a grade, that's when you'll find out what your "Max EGT" really is. Impossible to tune for that without paying for dyno time or hooking on a trailer when you live in the prairies.

 

[vwluv10338]

Deleted accidental post

 

[mudgudgeon]

o I drove over the mountains to go camping this weekend in what should have been a 2.5 hour drive. I added an extra hour to our time, calculated by a very forgiving girlfriend

I see an extended shoe** shopping trip in your future






** Damn auto edit! Substitute "shoe" for your girl's fashion/shopping fetish of choice

 

[Mcreight911]

To check at what boost your pin starts to move and at what boost you reach fuel cut colour the pin with texta as previously mentioned . Then use regulated compressed air and your normal gauge on the same line plumed to the compensator. Try low psi on the compensator first then release the pressure. Raise the boost in small increments untill you here the pin re-seat as the air pressure is released. The psi that your boost Comp moves will be a tad below that . The texta will also show if it moved .If u use the standard compensator spring with hi boost you may need to shim the pin to eliminate over boost fuel cut . A deeper grind helps too.

Do the same for your max boost to set your grind or shim point .

Using the main fuel screw effects internal case pressure and timing advance too . Keep that in mind .

 

[DancesWithMutts]

Great discussion as always. I am surprised that no shop has offered aftermarket aneroid pins for us yet. Does anyone know if there is anything to be gained by having a larger diameter aneroid? Does the follower pin have any more useful travel in that direction?

Just to clarify i am talking about solving the issue of over-fueling at off-boost for very built rigs.

 

[mudgudgeon]

Great discussion as always. I am surprised that no shop has offered aftermarket aneroid pins for us yet. Does anyone know if there is anything to be gained by having a larger diameter aneroid? Does the follower pin have any more useful travel in that direction?

Just to clarify i am talking about solving the issue of over-fueling at off-boost for very built rigs.

Yes a larger diameter aneroid pin was discussed recently.
It would give you a greater difference from off boost fueling to full boost.
This would give you the opportunity to have a hotter main fuel screw setting, while still maintaining leaner off boost fuel setting.

You are right, one limitation is how far the follower pin, and stop lever can travel before they hit the housing.

Bosch VE pumps (Cummins amongst others) use a larger diameter aneroid pin.
I can't remember if the conclusion was that Bosch parts could be swapped onto a denso pump or not.
Top cover of the pump would have to come off to swap the aneroid bushing

 

[remy]

You can swap the fulcrum lever from a bosch. Some of them have a different ratio and so does in fact the same thing. Some bosch pumps have smallers dia pins also.

 

[remy]

Using the main fuel screw effects internal case pressure and timing advance too . Keep that in mind .

It was my understanding that case pressure was depending on rpms, not by main fuel screw.

 

[ForealBoreal]

Yes Bosch parts can be swapped over.
In my case the sleeve from one was put into my pump so I could run a cummins style pin.