A dyno debate

[300bhp/ton]

Hi there, nice new website!!!!

On a different forum there has been some dispute over the claims of a single user. They have an automatic Range Rover Classic with a 4.4 litre Rover V8 (this engine was used in Australia in some British Leyland vehicles).

This is an old school OHV and started life as a 215ci Buick small block. I’m sure some of you are familiar with them.

Not overly powerful, even the last 4.6 EFI units only had 225bhp and ~330lb ft from the factory.

A Range Rover has full time 4wd.

Anyway here’s the problem, they have produced a dyno graph and are claiming PEAK torque @ 1600rpm of 260lb ft to the wheels, they also claim only 50% of the power makes it to the wheels so in essence they are claiming over 500lb ft @ 1600rpm at the flywheel.

So far they will not accept that they may be wrong and that because of the auto the lower section of the torque curve may be inaccurate due to a non lock up converter.

Here is what they have been claiming. I’d appreciate any help or comments you may have as I’m only trying to help them and to discover the truth about their engines performance.

If they are correct and they really do have over 500lb ft @ 1600rpm at the engine could anyone take a stab and explain how?

Cheers.

Here is my Dyno graph. It is real and was done in second gear on a 4WD Dyno. The power is measured at the wheels and therefore there is usually a 30% to 40% power drop from ratings at the flywheel.

Ok in an auto Range Rover 3rd gear would be 1:1 not 2nd.

The left edge of the graph is about 1,600 RPM. For those that can do the conversions, as the graph is in KW's and Nm's, at the wheels my car was putting out 260 ft lb of torque at 1600 Rpm. The torque then drops off from there.

So PEAK torque @ only 1600rpm – eh? Normally these V8’s see PEAK torque above 3000rpm.

No it was at the wheels, so that would be the equivalent of around 400 Fl Lb plus at flywheel. But you have to think about the figures a little more.

Really???

No, it has nothing to do with what gear it is in, you will always lose around 40% of your power through the drive train.
It is an old 1970's 4.4 rover V8

Based on the gearing, atmosphere, etc, etc, the peak horsepower figure on the graph is less than half that at the actual flywheel.

I am correct when I have stated that the wheels only generate 50% of the power at the flywheel.

And in a auto, the torque convertor is the equivalent of the flywheel in a manual.

you would need a motor putting out around 500 ft lb torque in a manual to have the equivalent torque at the wheels as my motor and auto. I know that this is a difficult concept for some small brains to comprehend, but it does not change the facts.

Here are some of their other comments in the discussion:

Tdis have around the same torque at 4,000 RPMs as what they do at 1,800 RPM. Even though the 4.0Ltr V8 develops its peak torque at 3,000 RPM, it still has over 200 Ft Lb at 4,750 RPM. So the V8 has more grunt down low than the Tdi's and can deliver it quicker.

Not quite sure how making PEAK at higher rpms proves it makes more power at low rpms? Anyone want to take a stab at it?

Your problem is that a little knowledge is a bad thing. You read all this stuff and don't understand it, which leads to garbage coming out.

Thanks for every ones help

[kiwicar]

Hi there
the biggest problem seems to be that they are using torque and power as if they are the same thing, power is rate of work done, torque is angular force, you can have an enormous torque and no work done (and therefore no power) imagine a big fat RSJ embedded in the side of a building with a tank hung on the end of it, a very large torque at the point where the RSJ meets the building, but until somthing moves no work done therefor rate of work done zero therefor zero power.
The second thing is they are getting in a mess between aparent power as measured by the rolling road and the power generated by the engine. A very quick think about it would see that if you "lost" 250 bhp in a gearbox it would generate alot of heat in that gaer box, 1 bkp is 750 watts 250 bhp is 187500 watts or the same output as 61.5 kettles think how quickly 61.5 kettles would boil a gallon and a half of transmission oil (saying the heat is disipated in the two gearboxes and three diffs).
There is also the little detail that I do not know of a petrol engine under about 9 litres that will generate 500 ftlb of torque at 1600 revs may get 500 ft lb of torque out of a 501 BBC but at 2400revs at the minimum, or add a big blower.
Mike

[bill shurvinton]

Well for a start RWHP is totally meaningless. Dyno runs with an auto where you cannot lock up the TCC are meaningless. Dyno Dynamics rollers can easily be set up to give any number you want.

Ignore him.

[JP.]

claiming PEAK torque @ 1600rpm of 260lb ft to the wheels,
So far they will not accept that they may be wrong and that because of the auto the lower section of the torque curve may be inaccurate due to a non lock up converter.

You'r right on this one. The converter multiplies the torque by 2.5 till about 2000 rpm (depending on your stall and engine confiruration). Thats why its also called a torque converter.

Torque readings below 2000 rpm on a dyno with an autobox are always in accurate.

[Lewis]

The second thing is they are getting in a mess between aparent power as measured by the rolling road and the power generated by the engine.

Aye - very true. Most people know there are power losses through the drivetrain so wheel hp is always lower than flywheel hp. Front wheel drive cars with transverse engines tend to be more efficient than most rear drive configurations due to the layout of components. However many rolling roads, or owners, overestimate these losses considerably.

This is a bit OT but anyway, most rear drive cars have a 1 to 1, 4th gear which means that the power path goes directly through the mainshaft of the transmission. The only losses here are bearing drag which is less than 0.5% and the viscous drag of the gears running through the oil which is about 1% with hot oil. Published data indicates a transmission efficiency of 98 to 98.5% for conventional transmissions in 4th gear.

Losses caused by the driveshaft account for about 0.5% if they are properly aligned, balanced and with fresh U-joints.

Any loss from the differential, in the commonly used Hypoid type gearset, is in the order of 6 to 10%.

The worst scenario case for a rear drive setup is on the order of 12.5% in 4th gear, not the 20 -25% often published. If 25% was being lost in the drivetrain, the oil would boil in the differential housing in short order and aluminum transmission cases would fatigue and break from the temperatures generated. On a 200 hp engine, something on the order of 37,000 watts would have to be dissipated out of the transmission and differential housings. Obviously, this is not the case as mentioned previously, you'd have a bit of a problem if it were!

Transverse, front drive transaxles usually have no direct lockup gears and no 1 to 1 ratio, however, since the torque path is never turned 90 degrees as in the rear drive setup and efficient helical gears are usually employed for the final drive set, losses are more on the order of 6 to 9 percent in the upper ratios.

Unfortunately not looked much into 4x4 powertrains but I expect at maximum worst there could be something like 20% loss through them. I know certain non-turbo Imprezas suffer from heavy powertrain losses. Tire pressure plays a very important part in rolling road readings as well.

What do we reckon it's really making? 240BHP/320ft/lb? Depends if anything's been modified, I guess...

Only way they'll find out is by pulling the lump and bolting it to an engine dyno! - in fact, that applies to any engine!

[HairbearTE]

No 4.4 liter normally aspirated engine could make 500lbs @ 1600 rpm on regular fuel. At those rpms you couldnt get enough mixture through the engine to make 500lbs. A turbo diesel engine of 4.4 liters could be made to do it, but not a n/a rover v8. As has been suggested i would say this anomally has been caused by torque multiplication in the drivetrain.

[300bhp/ton]

Cheers for the replys, most helpful.

I'm not certain of the specs of their motor I've asked 5 times they still refuse to post the specs, however I suspect the cam is stock.