Disappointing fuel economy...

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Island Moose

Island Moose

Joined
Dec 2, 2004
Threads
126
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821
Location
Tauranga New Zealand via Vancouver Island Canada
I am now on my third tank of diesel since picking up the BJ70, and I must say that I'm less than impressed with the mileage. On the past two tanks I have averaged 13.25L/100kms or 17.75 miles per gallon.

Now I thought with this 3B engine I should be getting 9.5 L/100kms or 25 miles per gallon or better, given 100% highway driving.

Can someone offer a list of possible causes for this poor economy?

Thanks,
 
What size tires have you been running? Have you been booting it around town just 'cause it's so fun to do in the diesel? Have you been doing highway or city, hills or flats? What kind of RPM's has your engine been seeing? My truck (4-speed, mix of 235/75R15 & 31's, hard-top on & off, highway and city) has been getting around the 12L per 100km mark FWIW. Though I did get 9.0 (+-).5 L/100km one trip from PG to Jasper (return) (235/75R15's & hardtop & 80-90 KPH). Your 5-speed (and soft top) should get decent better fuel economy than a 4-spd 40 series.

How many km does your truck have? somewhere between 100000 - 150000km, you should think about getting the injectors rebuilt/replaced. Maybe adjust/check the valve clearances just as an excuse to learn some more about your new engine!?!?!?
 
Something doesn't jive there, Moose. My 13BT is now using approximately 11.4L/100kms in MIXED city/hwy driving. Your 3B should definitely be doing a lot better.

What's the mileage on your vehicle again? How much smoke coming out of the tailpipe? You have a fresh air filter, fuel filter, etc., right? Otherwise the truck runs smoothly and seems to develop expected power? Could be your injectors need servicing.
 
That is pretty bad. My BJ 70 with 170k miles on it gets 23 mpg on average, city highway offroad (~10liters/100km). It has fresh filters, belts, plugs and rebuilt injectors. Maybe you need to get new injectors.
 
FWIW, a BJ70 I've recently checked out gets 19MPG driving around town. The driver is a hospice worker, so she's kept good mileage records.
 
CruisinGA said:
oh wow.

17 mpg is bad for a cruiser?

All I got to say is I'm jealous. Damn jealous. :flipoff2:
Click to expand...

Yes, 17mpg on a deisel 'Cruiser is not good at all. I've had nearly 30mpg before! The 13B-T should be better than the 3B for mileage.
 
My BJ74 is not that great on fuel economy either, don't know what the MPG is exactly but I was expecting better. I will have to work it it exactly. The engine was smoking a lot initially but I replaced the filter and stuck a load of additive in the tank and it hardly smokes at all now, just a little bit on a cold start. I am using purple diesel which is a whole lot cheaper than the white stuff, makes a big difference.
 
Ok some more input

John,

I get about the same with my 70 series cruisers both on turbo and non turbo, actually the tubo'd ones get a little better. I think I get that because I am in southern california and the terrian is a lot of hills, and the hills kill the 3B. I also have some suspicions that the fuel in California as far as local diesel (not truck stop diesel) is not as good, I know sounds crazy but I do notice when I add some additives it runs way better with a little better mileage. Mine have around 200k+ mileage on most of them so maybe new injectors is something I need. Here is what I know about injectors on diesels as the wear they will give you more power because the opening wears to a larger one, so more power less fuel economy, so it could be a trade off. I friend of mine has an 85 BJ70 he just got, that is all stock and he is getting around 18mpg after we adusted the fuel flow (he had black smoke all the time). maybe helpfull or maybe you are noticing a problem I have been overlooking for years, but then again I am a lead foot so I normally do not expect good fuel economy :)

G'Day,

Michael
 
cruiser_guy said:
Yes, 17mpg on a deisel 'Cruiser is not good at all. I've had nearly 30mpg before! The 13B-T should be better than the 3B for mileage.
Click to expand...

I've never seen a 13BT that has had better fuel mileage than a 3B, Charles...including mine. So if you run into a 13BT owner that can beat the close to 30 MPG that a well tuned 3B is capable of...let me know. :) I'd be curious to know. I suspect that the direct injected 13BT is probably not as efficient as an indirect injected 3B even with the turbo. Thanks.

<edit> I always get my US and UK gallon mixed up, but finally found an online calculator that provides both US and UK MPG from L/100 km. Anyway, I guess 30 MPG might be on the high side for US MPG for a 3B to get consistently. My 13BT is only getting roughly 21 MPG in mixed driving, and I guess 24 MPG would be more realistic of a 3B than my out to lunch 30 MPG. :)

For those of you who are just as mathematically challenged as I am...the online mileage calculator (especially handy for Canadians to talk with Americans):

http://jumk.de/calc/mileage.shtml

Cheers.
 
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I have new filters, 31" tires on factory rims, no mods. I drive the speed limit, all highway, though with some pretty long steep hills (but then I turn around and come down the same hills).

No black smoke at all, so I have to think the injectors must be the problem. Anyone know of any rebuilders on Vancouver Island? Approximate cost if I deliver them in a box?
 
The long steep hills will definitely kill your economy, especially on a 3B as previously stated by someone. I would imagine that if your injectors were in poor shape that you would be seeing a lot more smoke since you would not be burning efficiently?
 
4 wheel auto in edmonton has injectors. they are small and can be shipped easy. i think its cheaper to buy than rebuild. but I could be wrong. also check that your injector pump is timed correctly.
I get 10.5L /100kms on the highway with my 3b 60. consistently. heres the link below.


incorrect knowledge @ the time. nozzle tips are cheaper, whole injectors are expensive. prolly 300 a piece. if you can get them. rebuild your own is the most practical. many good places will do the whole set for 200-300. I paid 300 and was very happy with results. sorry I had to fix my earlier post. thx


http://store.4wheelauto.com/view_product.php?product=INJ87MRL22
 
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Yeah, the hills are an issue to be sure. With only 120,000kms I would also question how dirty those injectors could be? But other guys here talk about hilly terrain and they get nearly double my mileage...it might be worth it to have them done anyhow.
 
Read this thread which talks about nozzles: https://forum.ih8mud.com/showthread.php?t=21501&highlight=idi+nozzles Your 3B has IDI nozzles.

Prices in the past if you take your nozzles into a shop have been around $50.00 per injector. Allied Holmes and Freds Fuel Injection in Vancouver have been two I have used in the past. Ask to see the nozzles tested with their bench tester (you will see crack open pressure and nozzle spray pattern).

You have done the fuel and air filters, so those are good.

Do a valve set as well...at least once a year. If you are feeling really adventurous pull the rockers off and check the ends to see if they have been pounded out from maladlustment.

hth's

gb
 
brownbear said:
4 wheel auto in edmonton has injectors. they are small and can be shipped easy. i think its cheaper to buy than rebuild. but I could be wrong. also check that your injector pump is timed correctly.
I get 10.5L /100kms on the highway with my 3b 60. consistently. heres the link below.


http://store.4wheelauto.com/view_product.php?product=INJ87MRL22
Click to expand...


I went to that site, and ordered that 24volt lighting kit (awesome!). I will also keep them in mind for the injector issue.

Thanks
 
Ok more specs on my rigs and mileage

Oh yeah,

I forgot to mention I am running 35" tires on my rigs one has 4.88 gears (too low for 3B don't do it!!) the other is running 4.11gears (perfect for on-road off-road with 3B) and the third one is running 3.70gears (a little too tall of a gear for 3B with 35").

I have been experimenting with gears and found you can stick with 3.70's on a BJ70 all the way up to 33" tires and you will do pretty good on and off road, but anything larger than 33" I recomend 4.11 gears they put you back to being just about right, that is if you are running turbo or not. I had originally put 4.88's in my BJ42 with AXT turbo on 3B running 35" and it just is not right off-roading, it always seems to be too low of a gear. So in conclusion the 3B's like a taller gear than a gasser, I think that is why they starting shipping the 70 series with 3.70 gears.

Thanks,

Michael
 
Stone said:
I've never seen a 13BT that has had better fuel mileage than a 3B, Charles...including mine. So if you run into a 13BT owner that can beat the close to 30 MPG that a well tuned 3B is capable of...let me know. :) I'd be curious to know. I suspect that the direct injected 13BT is probably not as efficient as an indirect injected 3B even with the turbo. Thanks.

<edit> I always get my US and UK gallon mixed up, but finally found an online calculator that provides both US and UK MPG from L/100 km. Anyway, I guess 30 MPG might be on the high side for US MPG for a 3B to get consistently. My 13BT is only getting roughly 21 MPG in mixed driving, and I guess 24 MPG would be more realistic of a 3B than my out to lunch 30 MPG. :)

For those of you who are just as mathematically challenged as I am...the online mileage calculator (especially handy for Canadians to talk with Americans):

http://jumk.de/calc/mileage.shtml

Cheers.
Click to expand...

My 30mpg was in imperial gallons being in Canada and all.

Stone, I'm surprised that the 13B-T does worse than the 3B on fuel economy. I would have thought that the direct injection makes things more efficient. The VW diesel is a direct injection as are all the big rigs. They are going for power and efficiency. From my understanding the indirect injection is really only good for startup as the precombustion chamber is small and quickly heated as compared to the whole cylinder. After that you're losing efficiency as the products of combustion need to travel through the precup with each cycle.
 
It seems to me that older DI engines are not necessarily more efficient then IDI engines, and certainly no comparison to modern common rail DI engines. There is no computer controlling fuel delivery at idle and under load, and there is no computer controlling of the nozzles. I do prefer the older system of the 3B and 13BT from a simplistic point of view.

The older DI engines are perhaps more tuneable then it's IDI brethren, which leads to the thought that perhaps the design “is” more efficient, and comparing a factory 13BT to a factory 3B via fuel economy is perhaps not the best measure.

IDI motors are built with natural aspiration in mind, and the 3B uses the pre-cups and piston design (Richardson Comet Mark 3...or something like that..ala info via the DTLC) to maximize the combustion process (and a 20:1 ratio). The lower compression 13BT (17:1) and direct injection requires the use a turbo (my thoughts, not confirmed) to use all the fuel. I'd hate to think of the smoke clouds behind a 13BT with no turbo in the system.

Also...more power at the foot = using that power.

What was the Toyota DI engine that was used in South America for a few years and had no turbo? Quite the smoke show from what I understand.

As for starting, my 13BT DI engine starts much easier then any IDI 3B I've owned. Down to 5C it starts no problems at all...with no glow. Below that, a few seconds of glow via Stickboys manual override works wonders. The only IDI engine I've seen start as nice as is the high compression 1HZ.

Charles, your 30impg is not your "average" mileage either...correct?

gb
 
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