dynamometer readings

[SidewaysFeltham]

And of course, unless the engine has an onboard Fuel-Air mixture analyser built in, any read out is a simulation according to the preset parameters of the ECU....................................................

Gas analysis is a pretty common technology, these days: the old Exhaust Gas Analysers we used to use were OK but not very accurate.

In the end experience and various indicators were as good as anything else when setting up multiple carbs, for example.

As an example, Explosive Sniffers (which all look for a specific gas given off by all normal military and commercial explosives) enjoy an accuracy of a few parts per million in air.

Since 1980 when I sort of crossed the tracks in engineering back to ICT and Silicon areas, I have become increasingly distrustful of Black Box Syndrome.

Any measuring kit is only accurate, really, at the point of careful calibration: which is a lab job. Even with quite simple stuff like DMMs (Digital Multi Meters).

Unfortunately, far too many people, today, assume a black box can't lie: like the flawed Lion Intoxometer used by Plod, when hundreds of cases were subsequently thrown out: and, of course, Gatsos which haven't been correctly setup and calibrated.

Etc.

What is now practical, is stuff like cylinder combustion pressure measurement to very accurately measure/calculate BMEP for example.

All sorts of hazardous environment transducers are readily available thanks to aviation and space research etc. which have really made performance engine design and testing a most scientific area, instead of an intuitive process.

Only an experimental area back in 1970.

[AU N EGL]

Many of our race series now require that NO tuning be done to your race car from the time it goes on track of the first practice, not qualification to the race. Pre race tech will put special tape and seal the OBD II port. If the seal is broken your disqualified. If there is an emergency and permission is given, then a retune may be done, IF there is a portable dyno at that race so the car can be re dynoed and HP verified before the next on track session.
Historic race cars are different.
What also is done with cars that do not have a computer, ( or 4 wheel drive) if the car 'appears' to be faster then its peers, then the Race Tech Stewards place a GPS recording device on that car to measure speed, acceleration, and a few other things.
From these recordings that car can be determined what the HP is, the car is weighed and the HP:WT ratio is calculated too assure race compliance.
We have had several ppl put in multiple computers ( hidding a second computer) and a hidden switch ( as a High beem flash switch) to change between computers and different tunning for different HP levels.
Our race cars do not have to be emissions compliant. Mine is( somewhat) I do run 100 octane race fuel, I do have High flow cats and it is still road legal and licensed. I do pass the annual emissions requirements each year..
I only do this so I can drive on the country public roads to assure the car is running properly before I take it to the race track.
Back to OP. It appears Dynos are used differently on each side of the pond.

[SidewaysFeltham]

Originally Posted by AU N EGL

Back to OP. It appears Dynos are used differently on each side of the pond.

I don't think they are used particularly differently, AU N EGL: after all everyone is seeking identical results.

Simply, they are expressed in different ways.

Since this most interesting thread started, I've now had the opportunity to look up some of the related references.

Power for automotive engines is stated in different expressions in different countries.

In the USA HP (SAE) has replaced other values of measurement. SAE Certified HP has now apparently replaced HP (SAE) in an endeavour of creating one level benchmark.

In europe HP (ECE) was created to replace DIN: and is now being replaced by ISO-14396 as the new standard.

There were a load more but these are now basically redundant.

Thus it is simply a matter of codification, like any other measurement benchmark, be it inches, centimetres, volts, etc

All that said, since power is a function expressed as:

Power = Work
Time

Then it doesn't matter Where it is measured: at the flywheel or at the driving wheels. It's comparitive.

What is critical is that whatever expression is used to quantify power e.g. is used across the board when comparing like for like.

Going back in time, when I was installing my brake (1971), I worked closely with the Head Tech of the supplying company: after this we stayed in touch as we shared keen interest in the future of engine diagnostics.

In the end he was headhunted by BMW, who at the time were, of course, investing millions in engine research and performance.

BMW were then using active pressure transducers to measure combustion pressure to optimise their head designs and adiabatic efficiency etc.

Engine Measurement Technology is now of course extremely advanced for both development tuning and operating management.

Most competitors of course, simply cannot afford to use it.

[tristancliffe]

Originally Posted by AU N EGL

if the car 'appears' to be faster then its peers, then the Race Tech Stewards place a GPS recording device on that car to measure speed, acceleration, and a few other things.
From these recordings that car can be determined what the HP

Do they really think it's possible to generate accurate horsepower readings from accelerations? Do they not understand aerodynamics and other frictional losses? Yes, you can guess vague ballpark figures, but not with sufficient accuracy to perform power:weight ratio legality calcs!

I conclude that rolling roads are pretty similar each side of the pond, but the organisers and competitors have different ideas of what the values can be used for, and what they actually mean.

[AU N EGL]

Originally Posted by SidewaysFeltham

Engine Measurement Technology is now of course extremely advanced for both development tuning and operating management.

Most competitors of course, simply cannot afford to use it.

Very true. Even the least expesive Bosch Motorsports ( Many GT cars) ECMs are expesive. However, finding good after market ECM programing software is not that difficult for modern cars and race cars.

My tuner and I use EFI Live. http://www.gmhightechperformance.com...ing/index.html Any modern race car builder will also need great computer tuning skills, along with access dyno tuner to get the most out of their cars.

[AU N EGL]

Originally Posted by tristancliffe

Do they really think it's possible to generate accurate horsepower readings from accelerations? Do they not understand aerodynamics and other frictional losses? Yes, you can guess vague ballpark figures, but not with sufficient accuracy to perform power:weight ratio legality calcs!

Ball park figures are close enough when at the race track and a dyno is unavailable to test the race car. Or for use with a 4 wheel drive car. If that 'ball park' figure shows that a particular car is faster then its competitors, then the results will be in dispute until the particular car goes to an Official dyno station to get tested.

The few cars that were caught we running too low a HP:WT ratio for that class. If these guys do it again with in 3 years, they are history.

I will look for the particular GPS / Accelerometers package they use and get back with it.

[SidewaysFeltham]

Originally Posted by AU N EGL

Very true. Even the least expesive Bosch Motorsports ( Many GT cars) ECMs are expesive. However, finding good after market ECM programing software is not that difficult for modern cars and race cars.

My tuner and I use EFI Live. http://www.gmhightechperformance.com...ing/index.html Any modern race car builder will also need great computer tuning skills, along with access dyno tuner to get the most out of their cars.

This sort of kit is quite common in Europe, in fact.

Re-Programming EEPROMs, also known as "Flashing" is of course common in ICT areas (Modems, cell phones etc) as well as Automotive.

The rather uncomfortable term used in the UK is "Chipping".

What I mean, however, was having access to a comprehensive engine dyno and the range of very expensive things like combustion pressure transducers, solid state temp transducers of various sorts, accurate flow transducers and etc.

These, are commonly used nowadays, of course, by manufacturers and such as F I engine developers.

Changing mapping without access to a whole host of ancilliary equipment can be fraught with problems.

Many "Tuning Firms" did and still do, but often whilst they do create more power, they then build in other difficulties.

A bit like the early turbos, for example: no power, the engine nearly died and then suddenly, after a null, the power came in all at once: leaving the car dangerously undriveable.

A good race engine has to deliver performance right the way through: no point in having massive top end power and useless acceleration, for example.

It's all a compromise, at the end of the day.

[AU N EGL]

Originally Posted by SidewaysFeltham

A good race engine has to deliver performance right the way through: no point in having massive top end power and useless acceleration, for example.

It's all a compromise, at the end of the day.

I agree.

We have many many drag races who all they want is TOP END POWER. Of course their cars have nothing under 3000 rpms.
There HP & TQ numbers are great, but the under the curve numbers are down the toilet. Great for Pub ( bar ) / BS racing.


One of the acceleratmeters that is used over here is called G-Tech Pro. It is really not too bad. Plug in a few numbers, cars wt, ect and can give the owner a good HP & Tq ratings, 1/4" mile times, 60 foot acceleration times. Not bad for few hundred dollars.

[johnny yuma]

Originally Posted by Dave Brand

It was used in some countries outside Britain & the colonies. The British system , RAC Horse Power, was based on bore & number of cylinders - stroke wasn't taken into account, which is why a lot of pre-war British cars had engines with very small bores & long strokes. I believe the 105E Anglia would have been rated at 16HP under that system - its predecessors were 10s.

France still uses 'Puissance Fiscale' to determine the taxation rates for cars. Since 1998 it has been calculated from a combination of BHP (manufacturers' figure) & CO2 emissions.

Two cannibals were eating a clown.One says to the other "does this taste funny to you ?"

In South Australia the annual Top Speed runs on the perfect salt of Lake Gairdner are happening over 5 days from Monday thru Friday on a 9 mile course March 3 to7. Link at www.dlra.org.au .Why am I telling you this?-because the salt lake is known as the Big White Dyno where power meets wind resistance meets traction.Only place you'll see a Suzuki Hayabusa do 224 mph or a 34 Ford Roadster 197 mph on a dyno that doesn't lie.

[Suze]

Hoping somebody can help please.....

......I understand [now ] that there is a percentage loss in HP from the flywheel to the driven wheels. What I am trying to ascertain, is what on average that percentage loss is as I am selling my racing car but price dependent on the outcome of a rolling road test......

The figures I have been given with prices are based on measurements at the flywheel, so I am now trying to convert this to the HP at the driven wheels but whilst found this article useful have found very little resource material on the internet to do with RWD cars, have seen figures from 18-22% as the loss. Am trying to go back to the guy with some reasonable figures.

anybody got any info?

[AU N EGL]

Every Engine is different, for example:

For a small block V8 Chevy LS1, LS2, LS6, LS7 the figure used is 17% to 15%. Not exact but close enough.

17% for a manual transmission with the engine in STOCK form. 15% for a semi modifed engine, with better main bearings, light wt fly wheel, light wt drive shagft and a hardened gear racing tranmsisson and diff.

We have seen that number as low as 12% loss in a fully built race engine and drive train.

[Suze]

It's a Formula Vee, so a 1300 air cooled engine....

[tristancliffe]

I would say somewhere between 10 - 15% loss myself, erring towards around 12/13%. But that is +-4% anyway... It's just a guess.

Or take the rolling road readings estimated at the flywheel and tell him it's the 'wheel' readings

[SidewaysFeltham]

Originally Posted by Suze

Hoping somebody can help please.....

......I understand [now ] that there is a percentage loss in HP from the flywheel to the driven wheels. What I am trying to ascertain, is what on average that percentage loss is as I am selling my racing car but price dependent on the outcome of a rolling road test......

The figures I have been given with prices are based on measurements at the flywheel, so I am now trying to convert this to the HP at the driven wheels but whilst found this article useful have found very little resource material on the internet to do with RWD cars, have seen figures from 18-22% as the loss. Am trying to go back to the guy with some reasonable figures.

anybody got any info?

In order to accurately measure frictional losses in the power train, manufacturer's level chassis dynos run a reverse test, where a known power is applied to the rollers, which then drive the transmission with the engine off.

The problem here is that in order to enjoy any accuracy, the internal frictional losses of the engine have to be known, too. This is measured in a similar way by power testing the engine on an engine dyno: and then running the engine (switched off) by a known power exerted by the dyno. Eddy Current Dynos are used for this purpose.

Once you know the internal frictional losses of the engine: then this can be deducted from the transmission loss test (which includes the engine loss).

How much power you are losing in your specific transmission is a function of the gear type (e.g. straight cut), the condition of the bearings and the gears, etc.

From a rusty memory, RWD road cars lose between 20-25% through the transmission and FWD cars up to 55%!

For example a standard Mini 850 would produce circa 34BHP net at the flywheel and you could see as little as 19 BHP at the driving wheels!

Race cars with a straight cut (e.g. Hewland) transaxle lose probably 15% ish.

In the absence of accurate measurement it's all a guess!

However, if you already have an accurate engine dyno power figure, then by subtracting a rolling road figure then you have the loss in power( I won't say "BHP" in case this starts another argument!) and then you can work out the percentage power loss by arithmetic proportion.

[Suze]

Thanks for that, found a few more things during my "web hunt" yesterday, shall see what happens!

[AU N EGL]

Inertia dyno: Measures the time for acceleration from a slow speed to top speed.
Grand AM DP cars must go though the engine dyno, chassis dyno and Inertia dyno. Then the Scrutineers determine what rewards wts to what car to balance performance

[AU N EGL]

Originally Posted by AU N EGL

I will look for the particular GPS / Accelerometers package they use and get back with it.

found one of them:

http://www.sae.org/servlets/productD...D=2002-01-3336

"tracking the GPS doppler frequency information provides a precise measure of the vehicle velocity that can be integrated to obtain very precise position estimates without having to solve for the CDGPS biases."