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I have information on a few governors that Isuzu have used.

What type governor is on your IP? It should be on the tag for the governor.

The governor for a marine engine may well be different to the truck engine, which mostly use the RLD governor.
 

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are 153 and 154 only screws holding this to the inj pump???I have 89 npr with this piece loose,, mebbe screws missing,, can someone talk me thru repairing this, thanks buck,, [email protected], I lost oil from a missing plug,, didn't run long but now I have a clack goes away with oil pressure,, what is most likely candidate, doesn't sound deep like a rod or main, but no noise from under vAlve cover like rocker arm,, please help, buck
 

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So I did my own modifications to the boost compensator and they well very well.....and then not so much.....

So as all of you know, the spring in the boost compensator is designed to start opening at around 2-4 psi and be completely open at 7 psi. This was all good with stock fueling and turbo, but if we changed turbos and added boost+fuel, pretty soon we realized that 7 psi was not enough boost to burn all the fuel so there was always a cloud of black smoke until the boost kicked in and cleared. This had me always wanting to play with the spring to have as clean a burn as possible. From my personal observations and from what others have shared in the forum, when having a tuned pump, a boost compensator that started opening at around 4-5psi and be fully open by 15psi would be a good idea. So I remembered that Hooke´s Law for parallel springs is that you can add their compression forces. So I went to a spring shop and got a spring exactly like the one from the boost compensator. I assembled the two springs together into the compensator and got it running.

Before describing my results, I want to describe my setup. I have a 4BD2T with a TD04HL-19 5cm exhaust housing and 11 blade turbine. I run the engine at 5000ft above sea level in a heavy vehicle with a large intercooler. So given these conditions, boost does not build as fast as you would expect but EGTs are always under control.

When running the truck, it went great. Lag was not long at all, almost all smoke was gone during the transition and power was great....EXCEPT that I found that after a peak boost at any higher "fueling" positions, when boost starts to decrease at higher RPM, the boost compensator would not have enough pressure and would, therefore, defuel. I guess that this condition is increased by the fact that I have such a small exhaust housing....but I definitely need it because of my altitude and the weight of the vehicle. Maybe it coud work with a TD04 or HE221 with bigger turbine housing.....not sure. The symptoms were almost like a boost leak but the entire system was thorougly checked and it held pressure OK.

I intend to try with a slightly softer spring and see how it behaves. I will report soon enough!
 

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Here is a copy of parts of the calibration details for the 4BD2T fuel injection pump Zexel #101481 0250, Bosch # 9400610517

4BD2T Calibration 0 by Bushie Ute, on Flickr


Full load and idle (no load) governor curves, i.e. control rack position (mm) vs pump speed (rpm).
Dashed line is control rack position when the boost pressure is 8 kPa (1.16 psi) i.e. the boost compensator reduces the control rack position by 0.7 mm.
When boost pressure reaches 49.3 kPa (7.15 psi) there is no reduction in the control rack position.

The problem is that when the full load screw is adjusted to increase fuel/torque/power, the entire full load curves for both boost and no boost are moved p to match the increase in the control rack travel, but we need the dashed line (for control rack position when the boost pressure is 8 kPa), to stay where it was. The ideal way to achieve that is to increase the stroke of the boost compensator somehow.

4BD2T Calibration 23 by Bushie Ute, on Flickr


Boost compensator adjustment

4BD2T Calibration 24 by Bushie Ute, on Flickr


aneroid and boost compensator adjustment. Screw 'D' is the adjustment for boost compensator stroke. May also need to reduce length of push rod 'I'. Note the aneroid creates the first limitation to increasing control rack position.

4BD2T Calibration 282 by Bushie Ute, on Flickr
 

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Stroke of the boost compensator can effectively be adjusted with screw "D". In fact, the way to adjust "off boost" fueling is to disconnect the turbo wastegate and adjust screw D to have enough fuel to actually move the motor and create enough heat to spin the turbo but not to make smoke (air fuel ratio above 18?). I have also played with pushrod "L" believing it was somehow limiting control rack travel. Still had to adjust screw D to adjust off boost fueling.

What I was trying to do was not to change the stroke of the compensator but the pressure at which that stroke happens. Having the compensator fully compressed at 7psi makes the pump deliver way to much fuel for the air available for a clean burn if the pump has been modded for more fuel delivery and it creates a lot of black smoke until it finally the turbo supplies enough air to clean it up. I am still cracking my head thinking how I am going to do it.
 

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In fact, with screw "D" you can extend the stroke of the compensator but you can get to point in which so little fuel is delivered that: 1. A heavy vehicle will barely move and, 2. The turbo receives so little heat that it actually never builds boost and, therefore, never activating the compensator and the extra fuel.
 

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UPDATE!!!

It was a clogged fuel filter!!! After changing it, it works great. Still get boost, still keep boost and good torque all throughout! Now I can endorse the mod to those who want to minimize smoke during off boost - boost transition!
 

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Thanks Bush65 for posting the injector curve/rpm chart,
I now see where my 4HEi is letting me down on the water. Is there any adjustment availabe in the governor to extend the 1425 rpm drop off point....?? By about 300 rpm.
Cheers.
 

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Would this mod work on a 4BD2t injection pump that has both the boost compensator and the altitude compensator?

Thanks!
 

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Would this mod work on a 4BD2t injection pump that has both the boost compensator and the altitude compensator?

Thanks!
I removed the rod completely and everything works just fine on my 4bd2t with both boost comp and altitude comp. It will smoke when the turbos aren't lit but it did make the engine feel much more lively, it reacts to my foot much faster.
 

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Discussion Starter #54
Excellent info, thanks.

Do you have any other info on the spring (wire diameter, ID or OD)?
Stock spring is 22mm OD, 1.6mm wire, 6 active turns.
Rate of about 1.3 N/mm or 7 lb/in.
Installed height is 25mm, free length was 33mm so that's 8mm preload.

I'm looking for stiffer replacement springs now.
 

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Discussion Starter #55
UPDATE!!!

It was a clogged fuel filter!!! After changing it, it works great. Still get boost, still keep boost and good torque all throughout! Now I can endorse the mod to those who want to minimize smoke during off boost - boost transition!
If you're still around. Do you have the specs on the spring you used?
 
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