Thread: Results are in, Dyno figures D/gas

This is what i was struggling to understand the torque figures, going on those figures, the car would pull the skin off a rice pudding

I have 65 Hp and 125 FtLb of torque at the wheels running straight diesel, on Diesel/gas it produces 77 Hp and 150FtLb of torque

Compared to the torque figures below

1998 Land Rover Defender
Station Wagon

300Tdi – 2.5l Intercooled turbo diesel
5 Speed Manual
119,000km when fitted
Average fuel consumption 10.7 l/100k

Standard Power: (red line)
66hp @ 3350rpm
620lbft @ 2300rpm

DieselGas Power: (green line)
88.9hp @ 3600rpm (+34%)
930lbft @ 2450rpm (+50%)

Originally Posted by Redback

This is what i was struggling to understand the torque figures, going on those figures, the car would pull the skin off a rice pudding

I have 65 Hp and 125 FtLb of torque at the wheels running straight diesel, on Diesel/gas it produces 77 Hp and 150FtLb of torque

Compared to the torque figures below

1998 Land Rover Defender
Station Wagon

300Tdi – 2.5l Intercooled turbo diesel
5 Speed Manual
119,000km when fitted
Average fuel consumption 10.7 l/100k

Standard Power: (red line)
66hp @ 3350rpm
620lbft @ 2300rpm

DieselGas Power: (green line)
88.9hp @ 3600rpm (+34%)
930lbft @ 2450rpm (+50%)

Baz,

Something MAJORLY wrong with the figures there, think about it....

BHP = Torque x RPM / 5250
DieselGas Power: (green line)
88.9hp @ 3600rpm (+34%)
930lbft @ 2450rpm (+50%)[/

930 x 2450 = 2278500 / 5250 = 434 bhp at 2450rpm......

Someone's telling porkies.... hehee

Bazza

Originally Posted by Psimpson7

47 kw and 170NM

ouch - just goes to show how much the drive train chews up power - improve friction losses in the drive train - better than engine mods.

Dunno how to do it - but it sounds easy

Garry

Originally Posted by garrycol

<snnip>
Dunno how to do it - but it sounds easy

Garry

Good one Gaz !

<edit> 15 years ago I was running a 7cSt (ATF viscosity) GL5 gear oil in a racecar transaxle to try and minimise parasitic drag losses, and only 600ml when 1 litre was specified, (Hewland, the manufacturer OK'd it) but we'd do anything back then to go faster.

OK what I wanted to do was show the difference between the two.Go back to Wilburs thread were we both have the same system but mine works and wilburs didn't.I know that tuning the engine up will give me HP gains but I wanted a bit more such as cruising economy,lower cylinder head temps and cleaner burning,all these I have got.I'm the first to agree the torque figures don't sound right but I was more than supprised at the amount of HP engines weren't making looking over the other dyno sheets.T dropped into the other dyno shop in town and he hasn't dynoed a Tdi but the other figures were similar on the same engines they both have done.This dyno run was for my engine,as I have posted it is into old age now that thats fine by me as it's been fantastic over it's life but now it is just a little bit better,I overtook a truck driving home today and I ran it to the governor in fourth by mistake with no problems,it just revved there.For the gain it gives,it cost me $1100 all up including the tank cover I needed for rego it is worth it,it is early days,It's on it's second tank of diesel but I'm more than happy with the way it goes.I have an egt gauge ordered and am going to chase Davy up for an engine temp gauge and I'll post up the readings so we can see what is happening. Pat

Originally Posted by barrangey

Baz,

Something MAJORLY wrong with the figures there, think about it....

BHP = Torque x RPM / 5250
DieselGas Power: (green line)
88.9hp @ 3600rpm (+34%)
930lbft @ 2450rpm (+50%)[/

930 x 2450 = 2278500 / 5250 = 434 bhp at 2450rpm......

Someone's telling porkies.... hehee

Bazza

I suspect that it is not as simple as that. Power is a constant (less friction loss) however torque is dependant on gearing. In other words the power at the input and out put of a gearbox are the same (less loss could be 15%) however the RPM at the output of the gbox will differ depending on the gear selected (for the same input rpm). In order to come up with a power value that is somewhere near that input to the gbox (minus the losses) the torque figures vary in proportion (inverse) to the RPM at the output. As power is a product of torque and RPM you need to ensure that you use the torque figures and rpm figures at the same location. The torque figures provided might be at the wheels whereas the RPM figures are at the engine in this case. Well thats the theory anyway.

Someone who has a bit more practical experience should be able to confirm this.

I have tried to read that a few times but can't really work that out. Normally vehicles are ran up in the gear that is as close to a 1:1 ratio as possible to negate the torque multiplier a gearbox will give.

In my experience the power is plotted against engine rpm so the rpm of the wheels is not in the equation here. The torque measured is simply how much braking force is required to hold the engine at that speed.

Also the power at wheels is always lower than that at the engine due to losses as you mentioned, so this would mean even more than the quoted figures at the engine........

Bugatti Veyron has 922 lb/ft and 1001 bhp so again the figures are onviously WAY off for some reason. A 16 litre V8 Scania truck engine only makes around 1500 lb/ft

Originally Posted by barrangey

I have tried to read that a few times but can't really work that out. Normally vehicles are ran up in the gear that is as close to a 1:1 ratio as possible to negate the torque multiplier a gearbox will give.

In my experience the power is plotted against engine rpm so the rpm of the wheels is not in the equation here. The torque measured is simply how much braking force is required to hold the engine at that speed.

Also the power at wheels is always lower than that at the engine due to losses as you mentioned, so this would mean even more than the quoted figures at the engine........

Bugatti Veyron has 922 lb/ft and 1001 bhp so again the figures are onviously WAY off for some reason. A 16 litre V8 Scania truck engine only makes around 1500 lb/ft

What I mean is this as per this equation that I have taken from wikipedia.



Through the use a gearbox with the same engine running at the same RPM making the same power we can get the gbox at a 1:1 ratio to produce the same RPM and same torque (minus frictional losses)

Now put the gbox into a gear that results in 1:2 ratio to produce lower RPM i.e., 1/2 the RPM, in order to keep the power constant the torque has to go up to 2x as much as before (inverse relationship).

even if the gbox is kept at 1:1 on a dyno as you suggest there is still the transfer case gears and the diff gears that result in torque multiplication to get the torque delivered at the wheel.

So what I was trying to say before is that you must make sure that the torque and rpm values use to derive power are obtained at the same place. There is no point in stating torque at the wheel and using the engine RPM as it will give you the wrong value.

Now this has nothing at all to do with Diesel Gas so sorry for the hijack.