Oddie
AntiSeptic Sandal Wearer
Is it possible to check just the rear wheels of a 4 wheel drive vehicle on a 2 wheel dyno? - surely there's loads of factors to take into consideration, like the power being consumed by the central diff, the gearing ratios for torque, the tyre size, that's before you consider the actual engine output of the beast! Other than the official stats for the engine which are readily available, it would be quite a difficult one to measure on that kit i would have thought?
They removed the front prop shaft and then activated the diff lock in the transfer box then it will run rear wheels only. It has standard size tyres and I am aware there are losses to the rear wheels. The stats say that it has a 132kw motor if Im not mistaken, but I want to know what is the maximum I can expect at the rear wheels. I had it dyno tuned as it felt dead now I have nothing to compare the results with.
Oddie
AntiSeptic Sandal Wearer
I can't see why you'd want this stat, it's never going to actually be achieved coz you'll always be driving it with 4 wheels - it' like asking how fast a horse would be if you broke its two front legs - but if it matters, i guess you could compare the results you got with the stock 132KW
thebiglad
Well-Known Member
I know you will always drive in 4wd, but you can only tune it on a dyno in 2wd for max performance, therefore I want to compare it to see if it is running correct. The 132kw as far as I know is measured on the flywheel.
Hi lunnmj, re your query on power at the wheels, I believe I know where your are coming from.
The motor industry as a general rule quotes it's engine power outputs in either BHP or Kw at the cranshaft.
You obvious understand that the avail power at the rear wheels (what would be on most german cars, the driving wheels) will be less due to transmission losses.
With most modern two wheel drive cars accepted wisdom says 10-15% loss.
With a 4 wheel drive - even in the two drive config you suggest - will be more. But I didn't realise how much more?
This is NOT a definative answer but I'm pretty sure I read somewhere recently that a TD5 Defender was tested and these were the results:
1. At the crank 122bhp;
2. At the rear wheels 62bhp !!!!!!!!!
Make of that what you will, but when you have a look underneath any fairly modern (coil sprung) Landy, there's a LOT of metal to move, between the engine & the back wheels.
Re your own tuning program imo I would use your first set of figures as your benchmark, then tune away and measure again. Then you wil see in % terms how good the tune-up was and whether it was worth it??!!
Cheers and good luck
Dave
RAZ8550TDI
New Member
dont see the point in measuring at the flywheel, at the end of the day on anycar yer still have to take away the drivtrain loss which will be about 20-25% then work out yer power per tonne, which on your car will prob equivilate to about 50bhp per tonne. again another loss, as mentioned just get a reading, use it as a bench mark and tune away from there.
You see the problem is I sent it in for a dyno tune as it felt sluggish on uphills and at the same time I had branches and a free flow exhaust fitted.
now I have the final results on paper of the max output KW and NM.
The Disco feels more responsive , but how do I know if this is better than standard or did the mods make it perform better and now it performs as standard ? Seeing that it is a low revving motor, what are the bets revs to keep it in for Performance and economy ? Example you cannot exccelerate in 5th gear or drive up any hill in 5th even at 100kph / 60mph as it slows down down. Is this correct ?
now I have the final results on paper of the max output KW and NM.
The Disco feels more responsive , but how do I know if this is better than standard or did the mods make it perform better and now it performs as standard ? Seeing that it is a low revving motor, what are the bets revs to keep it in for Performance and economy ? Example you cannot exccelerate in 5th gear or drive up any hill in 5th even at 100kph / 60mph as it slows down down. Is this correct ?
thebiglad
Well-Known Member
I'm sure the V8 boys will pile in soon on that one !!!! I can't believe that a 4 ltr v8 cannot pull itself up a hill - something is wrong and needs to be got to the bottom of.
V8 specialists please
BOOMER
Bloke from Dorset
Seems to me you are fretting over this rather too much chap.
I dont know what your local area is like for hills, but unless you ignore the fuel gauge and drive it on a bit like I have to in Dorset it WILL seem a bit sluggish on the steeper hills.
It wont matter one bit how many performance mods you add if the engine is not in fine fettle to start off with.
Worn camshafts are common and can affect performance (inability to rev much past 4000rpm) as could the air mass meter playing up (its between the air filter and the plenum chamber).
It could be lots of things, but I can vouch for the fact that a V8 at full chat is bloody quick for a big 4x4......
I dont know what your local area is like for hills, but unless you ignore the fuel gauge and drive it on a bit like I have to in Dorset it WILL seem a bit sluggish on the steeper hills.
It wont matter one bit how many performance mods you add if the engine is not in fine fettle to start off with.
Worn camshafts are common and can affect performance (inability to rev much past 4000rpm) as could the air mass meter playing up (its between the air filter and the plenum chamber).
It could be lots of things, but I can vouch for the fact that a V8 at full chat is bloody quick for a big 4x4......
RAZ8550TDI
New Member
yer gotta start with the basics mate and very good maintenance before you start modding as youll be wasting your money, its took me a long time to make sure my engine is perfect condition and running wise before it started tweaking.
