decreasing compression ratio in 3B (1 Viewer)

[Dougal]

Yes the Isuzu would have been a great choice but I already have too much time and money invested in my 3B to start over again. Plus my wife has actually learned over time what stuff is so just saying "im going to work on the truck" doesn't work anymore. I swear she has a list and keeps track of all the projects I do.

I was going to re do the pump in the future so that plunger option is very tempting indeed. Are old pumps common for those Dougal or can you just get the plungers by themselves?
g

The cheapest way to get a pump is to find a blown engine. The Isuzu 4BD2's crack heads occasionally (my guess is turbo gets gummed up, boost drops, driver doesn't know or care) and get given away.
There's also a cummins 4BT with an A pump for offroad applications which has 9.5mm plungers. Looks very similar to the Isuzu pump but fits on the other side of the engine.

Might be possible to retrofit the whole pump and governer, get rid of the pneumatic governor on the 3B. Isuzu pumps are on the right side of the engine, cummins on the left (drivers perspective).

Here's the cummins A pump:
http://www.4btswaps.com/forum/showthread.php?17692-Inline-A-pump-setup&highlight=pump

 

[Hulsty]

Are you talking inline or rotary pumps? Would a inline 13BT pump be reto fittable?

Does anyone know the capabilities of the 13BT pump?

 

[Dougal]

Are you talking inline or rotary pumps? Would a inline 13BT pump be reto fittable?

Does anyone know the capabilities of the 13BT pump?

These are all inline pumps. No idea about the 13BT, but if it's inline then the tag number will tell which plungers are inside.

 

[slammed41]

dougal,

are you saying that one could - theoretically - retrofit an isuzu 4BD2 fuel pump to a 3B? and, is this just theory?

is the advantage that this pump would move more fuel into the injectors, thus increasing power?

cheers,

r

 

[Dougal]

dougal,

are you saying that one could - theoretically - retrofit an isuzu 4BD2 fuel pump to a 3B? and, is this just theory?

is the advantage that this pump would move more fuel into the injectors, thus increasing power?

cheers,

r

The Isuzu pump is on the wrong side of the motor, so it'll be a PITA to try and fit the whole thing, but you should be able to strip both and rebuild the toyota pump with the larger Isuzu plungers.

The cummins 4BT inline injection pump is on the same side as the 3B pump and may fit as a complete unit. The plungers are similar size to the Isuzu ones. The cummins motor uses a mechanical governor instead of the pneumatic used by the toyota, it will feel very different to drive if you swap governors. All three of these engines use Bosch A type injection pumps, they are made by different companies but are all licensed designs so interchange will be high.

 

[slammed41]

thanks for the clarification, dougal. so, it's possible - though unconfirmed - that isuzu or cummins plungers would fit into a 3B pump.

it's also possible - but unconfirmed - that an entire 4BT pump could fit onto a 3B.

still, i am unclear as to why someone would want larger plungers in their pump.

The cummins motor uses a mechanical governor instead of the pneumatic used by the toyota, it will feel very different to drive if you swap governors.

can you elaborate on what the above means? exactly what is it that would feel very different?

curious,

r

 

[Dougal]

thanks for the clarification, dougal. so, it's possible - though unconfirmed - that isuzu or cummins plungers would fit into a 3B pump.

it's also possible - but unconfirmed - that an entire 4BT pump could fit onto a 3B.

still, i am unclear as to why someone would want larger plungers in their pump.

Yes that's right.
The larger plungers do two desirable things. Firstly they can pump a lot more fuel which directly translates to more avaialble power.
Secondly they inject fuel faster, this means a better burn, less smoke and lower EGT's for the same power level.

When plungers are being asked to deliver near all the fuel they can the injection duration becomes quite long, this means that instead of the fuel being injected when you need it, it has to start injecting early and finish injection late. The early injection causes black smoke, the late finish causes high EGT's.

By fitting bigger plungers you can get the same amount of power with a cleaner burn and lower EGT's.

can you elaborate on what the above means? exactly what is it that would feel very different?

curious,

r

The pneumatic governor used on most toyota diesels of this age uses a butterfly and pressure difference across that to control the engine speed. The cummins setup is a speed governor mechanical one using the cable onto the pump which results in your accelerator pedal setting an rpm which the engine will try it's best to maintain. It feels a little like cruise control or driving a tractor which will maintain speed even over undulating ground. The Isuzu governor is similar to the cummins one.

 

[slammed41]

Yes that's right.
By fitting bigger plungers you can get the same amount of power with a cleaner burn and lower EGT's.

It feels a little like cruise control or driving a tractor which will maintain speed even over undulating ground.

i understand, and nice analogies, almost tactile...thanks.

it all sounds great! i would suspect that if one was to rebuild their 3B pump, it would be worth seeing if these largers plungers could be installed OR finding out if a 4BT pump could be used in a retrofit.

what i don't understand is why i haven't heard of anyone doing such a thing. or perhaps i've not got my ear to the ground? i've seen no mention in the various 3B build stories.

anyone out there tried this?

r

 

[gerg]

Ok, sign me up.
g

 

[Dougal]

Ok, sign me up.
g

Are you on 4BTswaps.com? If not I can put out the call there for anyone with an un-needed pump.

 

[Dougal]

i understand, and nice analogies, almost tactile...thanks.

it all sounds great! i would suspect that if one was to rebuild their 3B pump, it would be worth seeing if these largers plungers could be installed OR finding out if a 4BT pump could be used in a retrofit.

what i don't understand is why i haven't heard of anyone doing such a thing. or perhaps i've not got my ear to the ground? i've seen no mention in the various 3B build stories.

anyone out there tried this?

r

So far no-one has pushed the limits of a 3B power-wise. Gerg is the first I've met. It's only because he's rebuilt it with alfin pistons and reduced the compression ratio that such a mod becomes sensible. Most people are happy with up to 10psi boost on an unopened motor and like to keep the risk down. The stock pump can deliver enough diesel for them.

 

[gerg]

This is really cool I must say. Just to clarify a few things though. I haven't as of yet dropped the compression but it is a for sure... when is the question. I am currently still running on my old cracked but not leaking head. My cam is still sitting on my bench waiting for a time when my wife and two daughters decide I can be in the garage for a day or so on some weekend. Yes I do live with women, and for those that do not, they do have a tendency to plan all of your spare time for this life and the next. That being said, I do love them to bits. Cam, inter cooler, head, pump? Something like that is my plan. I am past planning in terms of seasons and have moved on to years. I do have a spare pump and block that I can play with. Dougal sorry if I came across as like I was going to do this tomorrow. You had me at shorter duration of injection. More fuel is just gravy. I just think this sounds like a win win mod.
g

 

[baxter650]

I have a spare pump and a friend that works for BD in the fuel shop, i will have to pick his brain on this.
Never thought that far ahead to consider the IP as a power limiter.
I have (right or wrong) heard/thought precups to be the limiting factor, so aimed for keeping heat out of the head.

 

[Dougal]

I have a spare pump and a friend that works for BD in the fuel shop, i will have to pick his brain on this.
Never thought that far ahead to consider the IP as a power limiter.
I have (right or wrong) heard/though precups to be the limiting factor, so aimed for keeping heat out of the head.

Yes the head and pre-cups are going to be your limiting factor and the reality of souping up any engine is it may die in the process.

 

[baxter650]

That i do know, i have attended more than one funeral.
I will tell you, a quick death is not always painless.

 

[gerg]

Ok so here are two questions for you guys. Start up issues aside.

1. How low of a CR could an IDI engine run at operating temp with good fuel combustion efficiency and not have high soot production? 17:1?

2. With required fuel ignition temps aside, what CR would net greatest power output for an IDI diesel? I have heard really low number for diesels like 14-15ish:1


g

 

[Dougal]

Ok so here are two questions for you guys. Start up issues aside.

1. How low of a CR could an IDI engine run at operating temp with good fuel combustion efficiency and not have high soot production? 17:1?

2. With required fuel ignition temps aside, what CR would net greatest power output for an IDI diesel? I have heard really low number for diesels like 14-15ish:1


g

Soot production is caused by two things. Firstly is injecting fuel too early and charring it before it gets cleanl burnt (commonly seen by timing too far advanced), second is too much fuel (A/F ratio too rich).
I don't see your CR causing that, you'll have issues with white smoke from incomplete burn in the cold with a cr too low, but not black soot.

The best power and efficiency is the highest compression ratio you can run. Unfortunately mechanical limits (forces on the head and crank) stop us doing this.
However, replacing static compression with boost gives you a lot of that efficiency back, exactly how much is a game for people with expensive engine simulation software. A lot of modern di engines are running around 15-16:1 compression with a lot of boost, this keeps NOx down and makes for a smoother and quieter engine at idle. They run variable vane turbos but your compound set does much the same job.

The chev 6.5 diesel crowd have done a lot of work on reducing compression ratios in their idi engines, for the same reasons (make life easier on the head). 18:1 seems to be where they're at for their higher boost motors.

 

[gerg]

Thanks Dougal for that info, it is reassuring to hear. What kind of boost numbers are those guys running out of interest?
g

 

[Dougal]

Thanks Dougal for that info, it is reassuring to hear. What kind of boost numbers are those guys running out of interest?
g

Modern tdi's are running anywhere from 20-42psi boost in passenger cars, I'm not sure what the 6.5 chev owners are running.

 

[nate dogg]

I thought you were on a budget? You are speculating about larger plungers in your nippondenso pump? My guess (I actually don't intend to offend you, but) if you are unfamilar with the differences between IDI and DI pistons and liner protrusion then I am going to take a guess that you may be over your head in changing plungers in an inline pump or retrofiting a mechanical governor Isuzu pump onto a pneumatic governor Toyota engine. My recommendation if you just want a reliable motor and are on a budget of any sort is that you:
1. Remove pan of junkyard motor
2. Remove and replace bearings. Or if you have confidence in your bearing analysis decision making, clean, slather in Lubriplate 105, re-install
3. replace pump diaphragm
4. replace any other suspect gaskets, pilot bearing
5. inspect turbo fins, shaft play
6. re-install motor
Anything beyond this is experimenting and may or may not lead to frustration, stamping of feet and gnashing of teeth. Do not attempt to lower compression ratio, you (I believe) are not trying to build a 100psi compound turbo racing motor.