Thread: 4BD1 performance

fwiw, my most recent and noticeable improvement in power/performance and economy came from fitting a new zu 82deg thermostat (as recommended by earlier threads)

engine had been running way too cool

don't fit it without a new gasket however

Gidday mate, I've had some experience wringing the best out of my 4BD1 dragging things heavy. I dragged a tandem trailer (all up about 3 tons) from Derby, WA to Alice Springs (2600km on the bitumen). The fuel system was "OK" with no known probs. Poured black smoke for the first 1500km then gradually cleaned up and picked up a bit of power after a few days of flat chat slogging. 2nd gear at 50-60kph on big hills. Lack of cogs in my 4 speed is the main issue (6 would be nice). Only mod I have is a 2 1/2 inch straight through exhaust.

Other things I have found; don't miss the filter inside the delivery pump inlet banjo connection.

The real eye opener was the overflow valve on the top of the fuel filter. After 23yrs use, this valve's seat wears down to only about 1mm thick (about 4mm new). This lengthens the spring and reduces the fuel pressure to the IP (not good). I put a new one in (Isuzu gen. part from Don Kyatt for $29) and the difference was immediate, especially hill climbing. Hills that required a down change can no be made in the higher gear. Best $29 I ever spent on mine!

My preferred mod for more grunt is to fit a diesel gas system (even the most basic type). Easy to do and the govt gives you a subsidy. Adding a turbo is complex and expensive, albeit with a good result.

The 4BD1 is awesome off road, but it a slogger on the highway with heavy loads... not a speedster.

Check your fuel filter overflow valve as it actually determines the fuel pressue feed to the IP.

JohnS
(KhunMoo)

Originally Posted by KhunMoo

My preferred mod for more grunt is to fit a diesel gas system (even the most basic type). Easy to do and the govt gives you a subsidy. Adding a turbo is complex and expensive, albeit with a good result.

Along with the downsides of diesel-gas (detonation etc) on a NA engine it displaces much needed air (incl oxygen).
The combo of more fuel and less air means you'll be in danger of melting pistons.

A turbo actually makes your engine run both cooler and more effiiently, reducing EGT's as it improves power.

I too have an 86 5 speed I changed the transfer ratio from .996 to 1.23 ratio from a disco box. It has made a lot of difference on hills etc. 1st gear high is lower for better up hill starts and reduces the gap between 4th or 5th low and 1st high is much better for driving bush tracks. At a nice steady pace I found 4th low to slow but 1st high was ok but a bit of a creek or something I had to drop back to low again but now 2nd high is about like the old 1st.Highway still cruise at 90/100 all day. Hope this helps Jim.

With my 4BD1T in a rangie (2.3t empty) I can just be passed on hills by a new commonrail hilux.

Those hilux's have 130kw and are half a ton lighter.

These things don't have the run on me all the time, even when fully laden in the County I'll run past them up-hill!, mostly they look heavy, but we're 4 ton plus with all the gear!.......no way they'd be anywhere near that!.......their wheels would fall off!.

On improving the performance of a 4BD1, you could try a 3 inch raised air intake, using a 'ram' type head and smooth pipe all the way to the filter housing, to force air through. Also a 3 inch exhaust, with limited muffling would help.

Anything else is going to cost a bit more, like polishing up the inlet manifold and internals, fitting extractors, viscous fan, and/or blue print/balance the engine.

.......have you tried folding the mirrors back and treating the Rover to a good coat of wax?.

Originally Posted by yt110

I too have an 86 5 speed I changed the transfer ratio from .996 to 1.23 ratio from a disco box. It has made a lot of difference on hills etc. 1st gear high is lower for better up hill starts and reduces the gap between 4th or 5th low and 1st high is much better for driving bush tracks. At a nice steady pace I found 4th low to slow but 1st high was ok but a bit of a creek or something I had to drop back to low again but now 2nd high is about like the old 1st.Highway still cruise at 90/100 all day. Hope this helps Jim.

What vehicle is this in and what is your resulting rpm at 100km/h?

I went the other way in my rangerover, from 1.22:1 to 1.003:1. I saved some fuel doing it and cut noise in a huge way. Was 2500rpm at 100km/h, now 2000rpm.

Of course mine is turbo'd and shifts it's 2.3T very well. Squeals wheels in second on dry tarmac.

Originally Posted by 1103.9TDI

On improving the performance of a 4BD1, you could try a 3 inch raised air intake, using a 'ram' type head and smooth pipe all the way to the filter housing, to force air through. Also a 3 inch exhaust, with limited muffling would help.

Anything else is going to cost a bit more, like polishing up the inlet manifold and internals, fitting extractors, viscous fan, and/or blue print/balance the engine.

.......have you tried folding the mirrors back and treating the Rover to a good coat of wax?.

Or just turn the max fuel screw.
Of course you don't want to do this without an EGT gauge and preferably a turbo.

Using my fixed dyno (man made concrete viaduct with a known slope) I know I've got 75kw (100hp) at the wheels at 2000rpm.
Factor in a drivetrain loss of 25% and that gives me torque of 460Nm (this is at 1000m altitude).
Drivetrain loss of 30% gives engine torque of 497Nm

If the drivetrain loss is greater, then the engine torque is greater.
Can't wait to get the intercooler on, but I think the 24sp axles are a higher priority.