Thread: 101 on a Dyno

Since I have had my 101 I have been more than happy with the torque of the 3.5 V8 engine low down and offroad but not so happy when it sees a hill or its cruising speed on the highway. I believe it needs more torque up around the 3000-4000rpm rev mark. In saying that I certainly recognise the vehicle was not designed for highway cruising but nevertheless perform a little better.

A standard 3.5 24v 101 produces 86.5kw at 5000rpm and 230nm of torque at 2500rpm. I have an old style LPG system and an additional 12v alternator hanging off the engine so even if my engine was in as new condition it probably only produces around 80kw. My engine has about 150,000 km on it so a little wear - particularly of the cam lobes is to be expected but it does run sweet and easily revs out to 5000rpm through the gears.

So I thought I would put it on a dyno to see what is actually happening. The dyno guy says that typically a big 4wd with truck style diffs and gearbox etc will loose in the order of 30-35% of power through the drive system.

So here we are sitting on the dyno and doing a run. Sorry for the quality - taken on the phone and its microphone was overloaded by the sound - in real life the 101 sounded absolutely magnificent.



[ame]http://www.youtube.com/watch?v=xMmeSDHbNy4&feature=youtu.be[/ame]

Well there were a few issues with the dyno - its engine revs pickup was intermittent so torque was not available so the operator had to use my tacho to match power output. Secondly the dyno would not save the runs into its system so we had to manually record the kw displayed against my tacho.

So the results (power at the wheels)
1500 rpm 20kw
2000 rpm 25kw
2500 rpm 32kw
3000 rpm 36kw
3500 rpm 41kw

Why a max of 3500rpm?? The torque of the engine (noting its max is at 2500rpm) was just not good enough to allow the engine to develop full power. The dyno operator had the dyno set on its "softest" setting where it allows higher revs to be achieved but the old 101 just did not have in it to get over 3500rpm in 4th gear. On the road it will pull 4000rpm in 4th so the load on the dyno was greater than what the truck experiences on the road with no head wind.

The power curve was pretty straight and had not tapered off so assuming it could still manage full power at 5000rpm and it remained linear and flattened out between 4500 - 5000rpm (all assumption) then power at the back wheels would have been about 53kw.

Assuming the 30-35% power loss in the system this means my engine is producing somewhere around 75 to 80kw which seems about right. It would have been nice to get torque figures.

This exercise reinforced my view that while the 3.5 has good torque down low it need a bit more a little higher up to be a highway cruiser in hilly areas and headwinds.

Garry

Don't you dare break it before next weekend...