Thread: 4BD2T Inection Pump on a 4BD1T?

I'd throw it on and see what happens...be carefull almost every diesel place in Australia will rort ya as the old "needs a full rebuild" is almost always used by diesel services...Dougal or John may have more of an idea but I can't see it hurting by trying it on your motor then play with timing to see if you can get it to run properly, I'd say it will either start and run fine or won't start at all...depending on how different the cam is will determine how smoothly it delivers the fuel in comparison to engine cycle but bd1 and bd2's both share the same basic design,capacity,stroke etc this may be determined through some of the figures you posted

So reading through those charts, here is what I pick up.

The 4BD2T is factory set to about 10% more fuel, because the 2T is factory intercooled.
The 4BD2T timing device produces about 1 degree less timing advance.
The 4BD2T can produce a lot more fuel between idle and max torque, it relies on the boost compensator to limit the fuel based on boost.
The 4BD2T needs more fuel at idle.

There are apparently plenty of converted 4BD2-4BD1 engines in the US, but I haven't conversed with the owners of any. The biggest fundamental difference is the starting. 4BD1's run excess fuel to start, 4BD2's rely on their glow plugs. This is point "I" on the graphs. Both are allegedly set to the same value, but how the governor actually uses that point may be very different.

I'd run it and see. The timing marks on the 4BD2 likely won't line up.

Further to what Dougal said:

Timing adjustment is conducted by rotating the pump assembly with respect to the mounting flange that bolts up to the rear of the timing case. That is a non-issue.

I have only had time for a very quick scan of the pics:

Staying with timing for the moment I see differences in the timing advance
4BD1T: 0 deg @ 1250 prpm (pump rpm) to 3.5 deg @ 1500 prpm
4BD2T: 0.5 deg @ 500 prpm to 2.5 deg @ 1500 prpm (prpm = 1/2 engine rpm). You may be able to swap timers, but this depends upon whether the end of the camshaft is the same size.

Different camshaft could be any number of things. There are at least 2 different forms of the drive end of the shaft, where the timer attaches. The plunger lift may be different, but I doubt that would be significant because fuel delivery rates are fairly close. Perhaps the injection duration is different (rate of plunger lift).

The big difference I see is shown by the full load diagrams. In these pics the upper diagram shows control rack position vs pump rpm for the full load adjustment. The lower diagram is for idle adjustment.

The dashed line on the full load diagram is the change (reduction in travel) in rack position made by the boost compensator when there is no boost pressure.

4BD1T


4BD2T

The 4BD1T pump number you have given 101401-0660 is for a pump with a boost compensator fitted, and is the pump used on the 4BD1T from late 1985 to late 1988. Late 88 on have a different pump again.

Why do you want to change the 101401-0660 pump on your 4BD1T?

Thanks gents,

The governor maps are making a bit more sense now, as is the rest of the data.

Dougal, is there much chance of doing damage to the engine if the timing's not right? I'm thinking not likely, as the ignition's controlled by compression rather than spark, so it will either ignite when it's supposed to or not at all - would that be right? Also, where would be the best place to get in touch with the US guys regarding 4BD1 - 4BD2 differences?

John, I have a 4BD1T block without the pump. I've found on the forum that the 101401-0660 pump number corresponds to a 4BD1T, and gave it to MTQ Diesel so they have something to match it to. I currently run an NA pump with the fuel screw wound out.

I can see the differences in fuelling at full load between the two governors. If I'm reading that right, the 4BD1T reduces fuel delivery for the engine operating between 1000 and 1300 RPM at full load, and then ramps up again at 1500. Not what I would have intuitively expected - is that to deal with some sort of internal resonance / efficiency? More importantly, I'm curious to see what the NA pump governor map looks like at full load as that's what's currently running my NA engine that I put a turbo on.

From the graphs, the 4BD2T governor also seems to have a greater boost compensator stroke length, implying greater difference between off boost and on boost fuelling?

WRT changing the automatic advance mechanisms, the securing nuts have different part numbers, but look to be the same general shape, so I'm sure I could fit the old (NA) automatic advance unit on the new pump using the new securing nut. Question is, how different is the automatic advance fitted to NA engine pumps to the turbo versions?

4BD1T Auto Timing Advance___________________________________________ ____________________________________ 4BD2TC Automatic Timing Advance

Originally Posted by Offender90

Thanks gents,

The governor maps are making a bit more sense now, as is the rest of the data.

Dougal, is there much chance of doing damage to the engine if the timing's not right? I'm thinking not likely, as the ignition's controlled by compression rather than spark, so it will either ignite when it's supposed to or not at all - would that be right? Also, where would be the best place to get in touch with the US guys regarding 4BD1 - 4BD2 differences?

Damage, not really. If you are too far retarded then you'll get white smoke, particularly when the engine is cold. If you are too far advanced then you'll get black smoke, no power and a lot of diesel-knock tractor type noise.
IN between those two extremes there is a wide usable range depending on what you're trying to acheive.

I wouldn't worry about 1 deg difference in advance. First thing is see which mechanism fits which pump. There are two different tapers available for the mechanism fitment.

www.4btswaps.com a lot of members on there have 4BD2T's.

Originally Posted by Offender90

I can see the differences in fuelling at full load between the two governors. If I'm reading that right, the 4BD1T reduces fuel delivery for the engine operating between 1000 and 1300 RPM at full load, and then ramps up again at 1500. Not what I would have intuitively expected - is that to deal with some sort of internal resonance / efficiency? More importantly, I'm curious to see what the NA pump governor map looks like at full load as that's what's currently running my NA engine that I put a turbo on.

At the low end it's starting and anti-stall (yes we had it long before the pumas), the dip in the middle is to stop blowing smoke before the turbo wakes up.

Originally Posted by Offender90

From the graphs, the 4BD2T governor also seems to have a greater boost compensator stroke length, implying greater difference between off boost and on boost fuelling?

The Boost compensator stroke is noted "BCL". It's 0.75mm for the 4BD1T you've shown, which is funny because post 88 4BD1T's don't generally have a boost compensator, 0.7mm for the 4BD2T you've shown and 1.05mm for my 9185 4BD1T.

My pump in stock trim was set to produce a hair more than the 4BD2T pump. 79cc for the 4BD2T and 79.2cc for mine. It appears the early JDM engines ran the highest stock power/torque ratings of any 4BD1T. US market ones were dialled back a bit.

Pics below give the calibration for late the 85 to late 88 4BD1, pump 101401-0290. Unfortunately the control rack stoke vs rpm diagram is not orientated the same way as for the 4BD1T.

Full load calibration compared to the 101401-0660 pump for the 4BD1T of the same year range:

Adj point 'A' (this is approx where the engine make max torque)
4BD1 - 67.3 to 70.3 cc/1000 strokes at 950 pump rpm
4BD1T - 69.6 to 72.8 cc/1000 strokes at 900 pump rpm

Adj point 'B' for 4BD1 or 'D' for 4BD1T (max power)
4BD1 - 67.0 to 70.2 cc/1000 strokes at 1600 pump rpm
4BD1T - 78.0 cc/1000 strokes at 1500 pump rpm

Adj point 'D' for 4BD1 or 'B' for 4BD1T (low speed)
4BD1 - 48.7 to 51.9 cc/1000 strokes at 650 pump rpm
4BD1T - 49.7 cc/1000 strokes at 550 pump rpm

Dougal mentioned before that the 4BD2T pump delivery was greater to suit being intercooled. The torque curves I have shows

4BD2T
282 Nm at 1000 rpm
rising linearly to
339 Nm at 1800 rpm
then plateau at
344 Nm between 1900 and 2100 rpm
falling to
340 Nm at 3000 rpm

For late 88 on 4BD1T
248 Nm at 1000 rpm
rising somewhat exponentially to
305 Nm at 1800 rpm
peaking at
314 Nm at 2200 rpm
falling to
285 Nm at 3000 rpm

Note the performance of the late 4BD1T is about 14% greater than the pre 89 version 90 kW vs 79 kW and peak torque 314 Nm at 2200 rpm vs 305 Nm at 1800 rpm.

The 4BD1T, being direct injection, will produce more power and torque than a 4BD2T at the same max load fuel rate. So with the stock 4BD2T pump on a suitably turbo'd and intercooled 4BD1T you will get better performance.

Regarding "full load calibration", this is when the control rack is at the maximum travel (in the fuel increase direction) that the governor will allow over the full rpm range.

When we adjust outward, the full load stop screw on the outside of the governor, we permit the control rack to travel further when the accelerator pedal is pushed all the way down (for full load). This extra travel will be seen over the full rpm range if our right foot is fully down over that rpm range. This is similar to how the boost compensator shifts the curve down when the boost is low, but adjusting the full load stop screw moves the curve up. The issue with adjusting the stop screw for maximum fuel rate is the increase at low rpm when boost is low.

If 4BD1T and 4BD2T pumps have the full load stop screw right out I would think the delivery around where max torque is produced would be very similar. The difference will be at lower rpm.

Thanks John,

That gives me some confidence that the 4BD2T pump will be an improvement over my NA pump.

The two things I was somewhat concerned about (the shape of the governor performance at full load, and differences in timing advance) seem to be closer matched on the 4BD2T than the 4BD1 governor.

When compared with direct injection diesels, the 4BD2T pump appears to start advancing timing earlier (0.5 degrees at 500 pump RPM) to 2.5 degrees at 1500RPM. Direct injection pumps on the other hand advance very little before 1250 pump RPM, but then start advancing more rapidly:
- N/A pump - <0.5 degree @ 1250 RPM, 1.6 degrees at 1400 RPM and 5 degrees at 1600 RPM,
- 4BD1T pump - no advance at 1250RPM increasing to 3.5 degrees at 1500 RPM

May I ask what purpose the timing advance serves? Why does it provide better conditions for diesel combustion at higher RPM by injecting earlier? I understand indirect diesels have a precombustion chamber, so the pump has to allow additional time for the atomised diesel to make its way into the cylinder / combustion chamber, however why does the timing has to advance at increased engine speeds?

BTW, how long do the mechanically injected diesels "spray" for? Is it throughout the "downstroke", or just while the piston is near the top or the cylinder?

WRT governor performance, it's interesting to see the 4BD1 governor also has a rack position "dip" at full load, although much higher up in the rev range (looks like 1000 to 1100 pump RPM), or 2000 to 2200 engine RPM. This is compared to 4BD1T's dip at 1000 to 1300 engine RPM. If I put a small turbo (or a VNT turbo) that spools up early, I may be able to make better use of the extra fuel the 4BD2T pump seems to deliver during this "dip". Would that be a good assumption?

BTW, I've adjusted the 4BD1 governor performance graph so that it's oriented in the same position as the others:

Originally Posted by Offender90

Thanks John,

That gives me some confidence that the 4BD2T pump will be an improvement over my NA pump.

The two things I was somewhat concerned about (the shape of the governor performance at full load, and differences in timing advance) seem to be closer matched on the 4BD2T than the 4BD1 governor.

When compared with direct injection diesels, the 4BD2T pump appears to start advancing timing earlier (0.5 degrees at 500 pump RPM) to 2.5 degrees at 1500RPM. Direct injection pumps on the other hand advance very little before 1250 pump RPM, but then start advancing more rapidly:
- N/A pump - <0.5 degree @ 1250 RPM, 1.6 degrees at 1400 RPM and 5 degrees at 1600 RPM,
- 4BD1T pump - no advance at 1250RPM increasing to 3.5 degrees at 1500 RPM

May I ask what purpose the timing advance serves? Why does it provide better conditions for diesel combustion at higher RPM by injecting earlier? I understand indirect diesels have a precombustion chamber, so the pump has to allow additional time for the atomised diesel to make its way into the cylinder / combustion chamber, however why does the timing has to advance at increased engine speeds?

BTW, how long do the mechanically injected diesels "spray" for? Is it throughout the "downstroke", or just while the piston is near the top or the cylinder?

WRT governor performance, it's interesting to see the 4BD1 governor also has a rack position "dip" at full load, although much higher up in the rev range (looks like 1000 to 1100 pump RPM), or 2000 to 2200 engine RPM. This is compared to 4BD1T's dip at 1000 to 1300 engine RPM. If I put a small turbo (or a VNT turbo) that spools up early, I may be able to make better use of the extra fuel the 4BD2T pump seems to deliver during this "dip". Would that be a good assumption?
...

If you have a good turbo that spools quickly you should be able to produce a good deal more torque at low speed with the 4BD2T pump, otherwise the boost compensator should do its job. If not you either won't be able to put your foot down as far, or wont be able to turn the full load screw out as much to control smoke at low speed (before boost builds).

I'll do some calcs later today to show what happens with that extra fuel at low speed.

Regarding timing advance:

In the injection pump, the fuel in the gallery has filled the plunger cylinder when it is at the bottom of its stroke.

As the plunger rises it first closes the intake port and once that happens the pressure in the fuel rises.

The delivery valve at the top of the pump element opens when the pressure reaches the setting of the valve, and the pressure increases in the fuel line until it reaches the setting of the injector and they open. This discussion of pressure is very simplified, because it is a complex issue involving pressure waves traveling at the speed of sound in the fluid (many times higher than the speed of sound in air) and at sonic speeds much of what you might understand at lower speed will not hold.

The plunger continues to rise until a helical groove in the side uncovers the inlet port and the fluid above the plunger is open to the fuel gallery by a hole on the centre of the plunger to the helical groove and the inlet port. The pressure drops and so the injector and delivery valve close.

Now the governor has pushed the control rack, which rotated the plunger, by a sleeve that has gear teeth which engage with those on the control rack. The rotation of the plunger changes the stroke/displacement of the plunger when the helical groove uncovers the port.

What this means is when the governor determines more fuel needs to be delivered by the pump, because the load has increased or we have put our foot down and told it to increase speed (accelerate) the injection period is extended, more to the point the finish of injection is extended.

Combustion needs to take place close to top dead centre for best power and torque. Injection usually starts about 15 to 10 degrees before top dead centre and is usually all over by 15 degrees after (much earlier when running under low load).

The earlier combustion takes place the higher the torque and power. With larger displacement cylinders, larger displacement injection pumps are required to inject the fuel in the short time available for best performance. When we turn up our pumps, we increase the duration period as a consequence, but that is far from ideal. We could get more power from the same amount of fuel if it was injected in a shorter period. To mee

Unlike petrol which is a vapour thoroughly mixed with air in the correct proportions before it enters the cylinder. Diesel is injected as fine liquid droplets.

Before diesel combustion can start the hydrocarbon molecule has to be split into smaller molecules, mainly by the heat of the compressed air in the cylinder, but possibly helped by pressure. This delay time, before ignition, is fixed and doesn't speed up with increased engine speed. It does however speed up with the increased temperature and pressure after start of combustion. Getting off topic a little, the mechanical pump continues to inject fuel during this delay period, so when ignition does start and the the cracking of the molecules speeds up, there is suddenly a large amount of fuel that starts to burn, producing a shock wave (pressure wave) that we notice as "diesel knock". Modern computer controlled fuel injection systems, only inject a small initial quantity to get through this initial delay, then inject more when combustion has started. This greatly reduces the noise and importantly reduces NOx emissions (most NOx is produced by the early temperature and pressure rise at the beginning of combustion. Diesel combustion produces greatest pressure at the beginning and tapers off toward the end of combustion, which is the opposite of what happens in a spark ignition (petrol) engine.

So that fixed length pre ignition delay is one reason why timing has to be advanced as engine rpm increases.

Another reason is to allow time for the atomised fuel to mix with the air. A further reason is because of the longer injection duration when more fuel needs to be injected for higher loads or speed.

Your description of the combustion in an indirect injection diesel is not quite correct. Combustion of the fuel starts in the pre-combustion chamber and expands into the cylinder as the piston descends. No atomised fuel finds its way into the cylinder when the engine is running normally.