Thread: 4bd1/4bd1T and fuel consumption

Originally Posted by clean32

toped up today
105 ltrs = 934 klm around town with a bit of kit on and 31"

That's not too bad.It equates to a little over 25 MPG

John ( disco 44 )

i think so, its much better on the 31" than when on the 33" and every time i head out of town lately it seems to be to Mt Barker, so up the hill in 3rd on the Governor

Originally Posted by D3Jon

Generally around 10.5l / 100Km - non turbo (N/A) 4BD1 - not towing, mixture of town & hwy.

Jon

Forgot to mention, I drive around on mud terrain tyres on all the time, I reckon with AT's I'd be seeing 10 easily.

Jon

Originally Posted by flagg

...

Logically a turbo would have to use more as there is more air to mix it with..

The BSFC (brake specific fuel consumption) of the 4BD1T is lower than for the 4BD1.

Using official Isuzu figures from USA emission tags:

1980 4BD1 produces 87 HP SAE net at 3200 rpm and fuel rate at that power is 53.9 mm^3/stroke.

1989 4BD1T produces 121 HP SAE net at 3000 rpm and fuel rate at that power is 70.0 mm^3/stroke.

From those figures dividing HP by fuel rate tells us that:

The 4BD1 produces 1.614 HP from 1 mm^3/stroke at maximum power.

The 4BD1T produces 1.728 HP from 1 mm^3/stroke at maximum power.

Edit: So the 4BD1 with turbo should use less fuel to make the same power as a 4BD1 n/a. The 4BD1T is a very efficient engine by all comparisons.

At rated power, the 4BD1T is more efficient than a VW 1.9 tdi at rated power. Pretty impressive for a 25 year old truck engine.

I average 10 km/l with a RRC on AT tyres. Towing a light trailer takes me straight down to 9km/l (11l/100km), worst I've ever seen was about 6.5 km/l (15L/100km) which was towing another rangerover on a tandem trailer with a spring lift.

Another reason the turbo motors can use less fuel is they pull higher gears. It takes a pretty good hill to get me out of 5th. I can pull 4th up some ski field access roads.
Despite running a lot more torque and power than I used to have, my fuel consumption has not increased but my speed up hills certainly has. I use this vehicle for a lot of road trips, speed limits are 100km/h and enforced with tax-cameras.

12.7L/100 normally, 13.5-14.5L/100 with hard bush work, 15-16L/100 towing cars and car trailers, worst of seen was 19L/100 towing a bit over 3.5ton, at 120 on the hilly end of the hume, all on 35" tyres standard diff gears

My N/A 120" will not see any better than 14L/100

Don;t know how people can get 10's

My figures have all been accounted for any margin of error

In my Stage 1, N/A, LT95 and 3.54 diffs on 31's I get 11.5L/100k solo vehicle regardless.

Maximum top speed is 110kph flat.

Towed my 1.6t Field Kitchen to Meandarra from Brisvegas and a car full of crap at mostly 90km/h and got 12.5L/100k overall. This included up the range and alot of wind on the outward leg.

Can calculate precisley how many k's on a $20 top up on this method. I have to the fuel guage doesn't work.

CC

Originally Posted by rovercare

Don;t know how people can get 10's

There aren't any secrets to fuel economy, just a lot of factors which work together.

More aerodynamic vehicle (rounded brick vs square brick), thinner wheels with AT tyres at decent pressure and more open road driving (don't live in a city). I'm probably higher geared too (2000rpm at 100km/h).