How much BHP has escaped / Was never there?

[treetops]

Anyone dyno'd their brand new car (after running in) to see a BHP figure.

Or checked their used car now (unmodified) to see how many horses have escaped!

Lots of talk about used cars having xyz power but 10 years on I'm sure quite a few horses have retired....

[Vixpy1]

A few times

[pthelazyjourno]

A lot of time it's a myth, spread by idiots like Clarkson.

They buy ratty old sheds that have never been serviced, running on 5yr old oil, with half the spark plugs failing to fire, half the time suffering from compression issues and god only knows what - it's hardly any surprise their £5k supercars are running with 56 horses...

From the results I've seen, unless you have big issues, keep it in tip-top condition, and there's no reason to lose any BHP, at least at semi-sensible miles.

[MissChief]

Sometimes, once the engine has been run in and all the rough edges inside the cylinders have worn smooth its not unusual to make more than when new.

[300bhp/ton]

treetops said:

Anyone dyno'd their brand new car (after running in) to see a BHP figure.

Or checked their used car now (unmodified) to see how many horses have escaped!

Lots of talk about used cars having xyz power but 10 years on I'm sure quite a few horses have retired....

Trouble is, unless you use an engine dyno and test to the same standards (SAE Net/DIN or whatever) then the numbers you get are pretty meaningless and not comparable to any claimed figures.

[OdramaSwimLaden]

300bhp/ton said:

treetops said:

Anyone dyno'd their brand new car (after running in) to see a BHP figure.

Or checked their used car now (unmodified) to see how many horses have escaped!

Lots of talk about used cars having xyz power but 10 years on I'm sure quite a few horses have retired....

Trouble is, unless you use an engine dyno and test to the same standards (SAE Net/DIN or whatever) then the numbers you get are pretty meaningless and not comparable to any claimed figures.

I agree with you 289bhp/ton...!

[007 VXR]

Vixpy1 said:

A few times

You found some extra in mine last time

[Codswallop]

A guy on SeatCupra.net tested his standard 130,000 mile Toledo V5 just after buying it and giving it an oil service. The dyno estimated 171bhp at the flywheel, which is just above the factory new figure.

Iirc, Autocar or Auto Express did a strip down of a 60,000 mile BMW Mini which also included a dyno run, and again the power figure was spot on the factory figure.

There's often considerable variability in dyno accuracy however...

[Garlick]

The brochure for the Chim 400 claims 240bhp when new, a trip to SRR a couple of years ago resulted in this



I was rather pleased.

[300bhp/ton]

Codswallop said:

A guy on SeatCupra.net tested his standard 130,000 mile Toledo V5 just after buying it and giving it an oil service. The dyno estimated 171bhp at the flywheel, which is just above the factory new figure.

But that's exactly my point. How did they "guess" flywheel power from the derived whp figure? Was it imperial or metric hp? Was it an eddy current or a static drag brake dyno? What level of graph smoothing was used? And what standard where the figures corrected to?

[GregMac]

My 1997 Turbo 2000 only lost 3 ponies over 15 years - not bad going

[trashbat]

Unmodified Alfa 156 JTS, 7 years old. Supposed to be 165hp, gave me about 145hp. They all do that sir.

[300bhp/ton]

The Crack Fox said:

See this lot ?



Well, me and a bunch of mates wondered the same thing about BHP loss, so en-route to a trackday, we went and rolling roaded them, results are as below:



DNF = Doesn't really mean DNF, it mean we couldn't get 4WD stuff on the rollers, aside from the Maserati, in which case DNF meant DNF.

The main surprise was that there were no surprises, all cars had 'lost' roughly the same %age, from the brand new Caterham to the ancient Merc. All good fun though. Especially on track afterwards.

More pics of this lot [url=http://www.sucksqueezebangblow.net/folder/2012/10/04/car-club-18-30-a-classic-s2b2-adventure/[/here] if anyone is interested.

Surely if everything lost the same percentage that hints that the way you where measuring/calculating current flywheel hp was likely wrong by that amount?

It's a bit like saying that's worth $100, what does that work out in £'s? But not clarifying if you are talking USD or AusD or something else.

[BriC175]

I had my '97 E36 M3 Evo on a fairly accurate set of rollers and it produced 309bhp. They're about 315bhp as standard.

I also had my '99 BMW M5 on a different set of rollers just after having the Vanos rebuilt, a few other bits and bobs, and a service... It produced 405bhp. They're about 400bhp as standard.

[Codswallop]

300bhp/ton said:

Codswallop said:

A guy on SeatCupra.net tested his standard 130,000 mile Toledo V5 just after buying it and giving it an oil service. The dyno estimated 171bhp at the flywheel, which is just above the factory new figure.

But that's exactly my point. How did they "guess" flywheel power from the derived whp figure? Was it imperial or metric hp? Was it an eddy current or a static drag brake dyno? What level of graph smoothing was used? And what standard where the figures corrected to?

That's why I said in my post that dyno results accuracy can be variable. Not only are there variations in measurement units as you mentioned, but also in the way that the dyno itself works (and none of that info was provided by the OP in question).

I don't know the full details of how the flywheel estimate is come to (maybe Vixpy can expand on that), but I was under the impression that the flywheel figure was created after accounting for drivetrain losses using some sort of calculation (but that's just what I heard/ read elsewhere, so is possibly all wrong).

[300bhp/ton]

The Crack Fox said:

300bhp/ton said:

Surely if everything lost the same percentage that hints that the way you where measuring/calculating current flywheel hp was likely wrong by that amount?

I thought that too, but it was a newly installed, recently calibrated RR from a very reputable company. The results didn't have precisely the same loss, FWIW.

A rolling can and will be accurate, but they don't all work the same. There are fundamental differences between how they measure torque. Then you have the whole standards thing to account for DA, ambient temp etc etc.

Interesting non the less though

[zygalski]

Interesting...
A bunch of guys over on the Astra mk2 forums have independently dyno'd their redtop GTE's & all achieved factory returns of around 155 bhp on standard vehicles which are 20 years old, many having 100k on the clocks.
Guess it depends on how well engineered the units were in the first place & how well they've been serviced.

[300bhp/ton]

Codswallop said:

I don't know the full details of how the flywheel estimate is come to (maybe Vixpy can expand on that), but I was under the impression that the flywheel figure was created after accounting for drivetrain losses using some sort of calculation (but that's just what I heard/ read elsewhere, so is possibly all wrong).

Different dyno's do different things. Some just use a percentage (often controlled/editable by the user). Typically 15% loss for manuals and 18% for auto's and 25% for AWD.

Some will measure drag on a run down, but that's only part of the story as that is only the static resistance of the drivetrain, not the resistance underload.

The biggest trouble with 'guessing' flywheel figures is it's very easy to over estimate and give false high figures. Whenever my car goes on the rollers I try to persuade the operator to switch to whp figures as it improves accuracy.

[TheEnd]

300bhp/ton said:

I try to persuade the operator to switch to whp figures as it improves accuracy.

You'd never know if your car has lost power from leaving the factory, or if it ever made the claimed figure as manufacturers don't give out wheel power figures.

[otolith]

It would make far more sense to standardise on power at the wheels - at least that is measurable, and it's what you've actually get. No point getting excited at a bit of extra power at the fly if you have the world's most inefficient transmission.