rolling road at malvern

[rpurchon]

did you put your car on the dyno at malvern.if so how did you get on?

i was a little bit worried about putting my car on. half expecting to

to get embarrasing poor figures.

but i was v happy with the results.considering my car runs on SUs

and my diy head porting skills and engine mods.

richard

[foster461]

did you put your car on the dyno at malvern.if so how did you get on?

i was a little bit worried about putting my car on. half expecting to

to get embarrasing poor figures.

but i was v happy with the results.considering my car runs on SUs

and my diy head porting skills and engine mods.

richard

 

 

I was just gathering some data the other day via various web sites and magazine articles. Your dyno numbers are consistent with what I found I think. These are all based on the stock US carb engine as the starting point, rear wheel measurements.

 

 

[font=Courier New]Engine                                        Peak HP       Peak Torque[/font]    [font=Courier New]Stock engine                                     74             95Mild cam                                         89            111Mild cam, ported head, higher CR                100            114Big cam, ported head, higher CR, three carbs    146            144Supercharged, mild cam, 5lbs boost              118            134Supercharged, mild cam, 7lbs boost              131            147[/font]

 

[Guest ntc]

did you put your car on the dyno at malvern.if so how did you get on?

i was a little bit worried about putting my car on. half expecting to

to get embarrasing poor figures.

but i was v happy with the results.considering my car runs on SUs

and my diy head porting skills and engine mods.

richard

 

Richard

What was different between run 14 and 15 ?

Edited July 21, 2008 by ntc

[rpurchon]

Richard

What was the difference between run 14 and 15 ?

 

run 14 was the first run. no adjustments were made for run 15.

probably better second run as it was idling for 5 mins while they tied it down,

and it would have blown all the **** out the engine and exhaust.

richard

[Alec Pringle]

Hi Richard,

 

a very creditable exercise on your part !

 

One question on the figures . . . the calculated flywheel power compared to measured power at the wheels appears to indicate 22% loss. That seems a touch high to me, although I guess is makes the flywheel figure look better !

 

Any thoughts from anyone on drivetrain losses ?

 

Cheers,

 

Alec

[marvmul]

did you put your car on the dyno at malvern.if so how did you get on?

i was a little bit worried about putting my car on. half expecting to

to get embarrasing poor figures.

but i was v happy with the results.considering my car runs on SUs

and my diy head porting skills and engine mods.

richard

Nice figures! What camshaft is in it? It seems that your engine could do with a hotter camshaft without loosing much on the lower rpm range.

The maximum power is at over 5200 but is it possible that, when accelerating, you will tend to change to next gear at 4000 rpm already?

Maybe a hotter cam will give a sportier feel? No need to discard the SU's, unless you want the maximum torque at 5500 rpm.

[foster461]

Hi Richard,

 

a very creditable exercise on your part !

 

One question on the figures . . . the calculated flywheel power compared to measured power at the wheels appears to indicate 22% loss. That seems a touch high to me, although I guess is makes the flywheel figure look better !

 

Any thoughts from anyone on drivetrain losses ?

 

Cheers,

 

Alec

 

 

Wikipedia says drivetrain losses are typically between 10 and 20 percent and 20% doesnt sound unreasonable for these relics.

 

Stan

[rpurchon]

Nice figures! What camshaft is in it? It seems that your engine could do with a hotter camshaft without loosing much on the lower rpm range.

The maximum power is at over 5200 but is it possible that, when accelerating, you will tend to change to next gear at 4000 rpm already?

Maybe a hotter cam will give a sportier feel? No need to discard the SU's, unless you want the maximum torque at 5500 rpm.

 

its got a bog std cr cam in it.

i would consider changing it to a 2.5 pi saloon cam.

it would be half way between the cr and cp cam.

re the bhp figures max bhp above 5000+rpm is no good to anyone on a road car.

i am more impressed with the torque figures. spot on between 2500 and 4500rpm.

 

richard

[Alec Pringle]

Hi Stan,

 

for sure you'd never get anywhere near 10% losses in any TR !!

 

16-18% would be more in line with my past experience with IRS TRs, and a genuine 136bhp at the flywheel would be a good result running on twin SUs.

 

The 22% on Richard's print-out is what I was querying. But agreed, there is plenty of scope for power loss in an IRS set-up - it's all too easy to concentrate on the engine, and lose sight of how much is being wasted in an inefficent, worn, or poorly set-up drivetrain . . .

 

Cheers,

 

Alec

[Guest ntc]

Hi Stan,

 

for sure you'd never get anywhere near 10% losses in any TR !!

 

16-18% would be more in line with my past experience with IRS TRs, and a genuine 136bhp at the flywheel would be a good result running on twin SUs.

 

The 22% on Richard's print-out is what I was querying. But agreed, there is plenty of scope for power loss in an IRS set-up - it's all too easy to concentrate on the engine, and lose sight of how much is being wasted in an inefficent, worn, or poorly set-up drivetrain . . .

 

Cheers,

 

Alec

 

Alec

The rolling road man I use say's 18/20% on a TR with irs in good condition if that is any help

Regard's

Neil

[dblenk]

Hi all

 

i got my rolling road done and got 125 Flywheel with 83 at the wheels thats about 33%

 

i dont feel very well now, has something dropped off mine

 

he did say he set it for torque 151lbf.ft@3129 rpm

 

mine is a std head, std exhaust and std 125 cam (triple dellortos)

 

the sooner i get it sorted the better, waiting to get the lakes out the way first

 

regards

 

david

[foster461]

Hi all

 

i got my rolling road done and got 125 Flywheel with 83 at the wheels thats about 33%

 

i dont feel very well now, has something dropped off mine

 

he did say he set it for torque 151lbf.ft@3129 rpm

 

mine is a std head, std exhaust and std 125 cam (triple dellortos)

 

the sooner i get it sorted the better, waiting to get the lakes out the way first

 

regards

 

david

 

 

David, since the dyno can only measure what is happening at the rear wheels many of the HP numbers are derived including the power at the flywheel so it is unclear to me where that 33% number came from. Bottom line, you could have even less HP at the flywheel than you thought .

 

 

Stan

[dblenk]

Hi Stan

 

could be a bit of salesmanship, i know the 83 at the wheels is low hence i want to do the mods

 

i was thinking the engine is good for 165 at the flywheel following Kas Kastners book as i have posted previously so working on the theory i should look for around 135 at the wheels

 

awaiting the winter break cant wait for Malvern next year

 

regards

 

david

[Alec Pringle]

Hi David,

 

If 42bhp is being lost in the drivetrain, then somewhere along it's being translated into friction losses, or heat - about 31kW of heat, by my reckoning.

 

Either you've got the hottest TR6 on the planet, or the rolling road man was having a funny moment.

 

Cheers,

 

Alec

[Guest ntc]

Hi David,

 

If 42bhp is being lost in the drivetrain, then somewhere along it's being translated into friction losses, or heat - about 31kW of heat, by my reckoning.

 

Either you've got the hottest TR6 on the planet, or the rolling road man was having a funny moment.

 

Cheers,

 

Alec

 

Hi David

Don't get down hearted those figures just don't add up

Regard's

Neil

[Ragtag]

Hi all

 

i got my rolling road done and got 125 Flywheel with 83 at the wheels thats about 33%

 

My guess is that the 125 flywheel figure just comes from the theoretical value associated with a CR engined car. Unless your engine is fresh, it would be unreasonable to expect 125 from it in current spec.

[88V8]

My guess is that the 125 flywheel figure just comes from the theoretical value associated with a CR engined car. Unless your engine is fresh, it would be unreasonable to expect 125 from it in current spec.

 

Yes, and of course with crappy modern fuel we're having to run less advance than in the car's heyday.

 

My car showed 95bhp at the wheels, estimated 123hp at the flywheel. OK it's a CR, but the engine was tuned in the late 70s and I expected more than that.

 

I'm actually a bit suspicious about the figures. The car is high geared by its big tyres - one has to add 20% to the speedo figure - and the gearing must proportionately influence the power 'seen' by the dyno. When I explained the gearing to the dyno guy he looked rather blank and went into mumble-mode. Also, I noticed his inductive pickup that he supposedly used to check the rev counter was actually attached to the coil lead (perhaps it's a different design to mine ??) so one way and another I was underwhelmed.

 

Anyway, when I finish a few other jobs I'm going to take it to Engenuity for a run on their dyno, and then if the horses are really missing some legs, we'll conduct a search. In the meantime, I'm withholding judgement.

 

Ivor

[rpurchon]

what torque figures did you get.

on your print out bottom left = id date time run in @ rr

what figures are under the in @ rr

mine say 100@125.

it also says gear 3 on the other data.

and im quite sure he tested it in 3rd gear.

richard

[dblenk]

Hi Alex,Chris and Neil

the car ran well down and back up from Malvern , so thats what matters

i will use the figures at the wheel

i was hoping to mod to get 150 at teh wheels but that might be a bit optimistic

regards

david

[TR 2100]

If 42bhp is being lost in the drivetrain, then somewhere along it's being translated

into friction losses, or heat - about 31kW of heat, by my reckoning.

 

This prompts a few interesting questions in my mind.

 

Even if the typical modern car figure of a 20 bhp loss, flywheel to

rear wheels, is taken, it's still a significant loss, which, as Alec says,

must translate into a heat generated somewhere. But where?

 

The losses, and therefore heat gain, must be primarily where the

drive changes direction, that's gearbox and axle, a far lesser amount

would be lost through straight drive bearings for halfshafts etc.

 

Also, since if it's the max power that is being measured, it seems logical

to all but ignore the inertia of the moving components.

 

If max power is measured at the rear wheels, wouldn't it make a difference

if this were based on a measurement in 3rd rather than 'direct' drive in 4th?

(Or take this factor into account some other way)

 

Any theoretical engineers out there?

 

AlanR

[88V8]

what torque figures did you get.

on your print out bottom left = id date time run in @ rr

what figures are under the in @ rr

mine say 100@125.

it also says gear 3 on the other data.

and im quite sure he tested it in 3rd gear.

 

100@125, whatever that is.

Gear 3

But my gear 3 is not your gear 3, how/if he compensates for that..... ?

 

I suppose I should have asked him what all the other figures mean, I'd somewhat lost interest.

 

I got a separate print of the torque. Peak was 88 ftlb at 2850rpm, then fell off to 75 at 3200 then wobbled around 75 until 3,900 then tails off to nothing by 5,700rpm. Can torque be grossed back in the same way as HP? If so that would be 113 ftlb at the flywheel.

 

HP peaked at 95 @ 5,250 but was above 90hp from 4,400 to 5,600.

 

Ivor

[Guest Wyn]

I was told that BHP can be calculated as follows :

 

Torque multiplied by revs and divided by 5252 = BHP

 

It seems to tie in with my Rolling Road figures

 

Wyn

[foster461]

I was told that BHP can be calculated as follows :

 

Torque multiplied by revs and divided by 5252 = BHP

 

It seems to tie in with my Rolling Road figures

 

Wyn

 

The dyno shop that I plan on visiting soon says this on their web site:

 

How is engine power measured?

The fact is there is no way of directly measuring power - all types of dynamometer measure torque and then power is calculated from the formula BHP = Torque (ft/lbs) x rpm/5252. This basic equation is the foundation of all engine design, development, and tuning. Two main methods of measuring power are used in the automotive industry - (1) measurement at the crankshaft of the engine or (2) measurement at the driving wheels. Read on to find out more about these two methods.

 

How does an inertia type rolling road work?

The majority of rolling roads used to determine power figures in the US are inertia dynamometers. Inertia dynos do not directly measure the force on the dyno rollers to determine power figures. Instead, these systems calculate the force on the rollers using the formula:

F = ma

Where F is force; m is mass; a is acceleration

 

The mass and system inertia of the dyno rollers is known. In order to calculate the force applied, inertia dynos measure acceleration of the rollers by measuring the increase in current and voltage production when the dyno's eddy-current retarders are used as a power generator instead of a power absorber (as used to hold the dyno load when mapping engines).

 

Force on the rollers is therefore the roller mass multiplied by the acceleration determined by the voltage output. This force is multiplied by the radius of the roller itself to give torque at the wheels using the following equation:

T = Fr

Where T is torque; F is force; r is radius of application

Power is determined by using the formula:

BHP = Torque (ft/lbs) x RPM/ 5252

 

This calculation is then used for the power at the wheels measurement. If an ignition pickup on the engine is used, these power figures can be used to plot a power curve. In order to determine power at the flywheel figures, a coast down procedure is used which measures the deceleration of the rollers, and uses this figure as negative acceleration and the F=ma calculation is used again to obtain the power losses through the transmission.

 

The major problems with these systems occur when changes are made to any of the rotating masses in the system. This includes items such as the clutch, flywheel, or aftermarket wheels. These items do not change the power of the engine (obviously). However they will change the rate of acceleration of the vehicle. Therefore these changes will change the power output measured on an inertia dyno. This is another reason why a number of dyno manufacturers will not guarantee accuracy greater than 5% for their dyno systems.

[Guest ntc]

Hi Stan

If that is the case? how come a tractor unit with 320 hp and loads of torque can pull a 44 ton load be compared with a 700hp Audi quattro rally car that can not, there is more to it than that

Regards

Neil

[stuart]

Hi Stan

If that is the case? how come a tractor unit with 320 hp and loads of torque can pull a 44 ton load be compared with a 700hp Audi quattro rally car that can not, there is more to it than that

Regards

Neil

Neil the truck can do it because of its gearing and the heavy duty clutch. A 320 hp pulling 44 ton wouldnt do too well either as that size is considered way too under powered for that weight nowadays, 420 up to 610 is more the norm!

I suspect the Audi could probably do the same if the clutch would take it but its power curve is totally different, the trucks maximum is delivered around 16/1800 Rpm!

Stuart..