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Thread: Engine dyno vs in car figures

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    Engine dyno vs in car figures

    Hi All,

    Looking for some experiances here. Iíve got a friend who runs a full modern spec rally escort. He recently received a 2.4 duratec from and VERY reputable builder. The engine produced 320bhp and 225ft/lb in the dyno cell. With the engine is in the car, itís been in for remapping by again, a VERY reputable mapper.

    Now the engine is in the car itís making 284bhp and 197ft/lbs, I think we all understand that an engine dyno is the absolute perfect condition for making power, and in car there are realities like an inner wing and full exhaust that with affect power.

    My question/comments to him are, would you expect to lose as much as 35bhp and 30ft/lb? It seems a large amount for the sake of getting it into the car. Or is there something in the setup that damaging a great engine? Exhaust manifold (Simpson) or something similar?

    thanks guys

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    Re: Engine dyno vs in car figures

    if the engine wasnt dyno'd and rolling roaded on the same exhaust manifold and system, that could easily be a large chunk of the difference

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    Re: Engine dyno vs in car figures

    Are we talking flywheel or at the wheels figures ?

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    Re: Engine dyno vs in car figures

    Quote Originally Posted by wildo105e View Post
    Are we talking flywheel or at the wheels figures?
    My understanding is this is both sets of figures.

    This is the engine on the dyno

    Quote Originally Posted by Shaunster View Post
    The engine produced 320bhp and 225ft/lb in the dyno cell.
    And this is the figure at the wheels with the engine in the car.

    Quote Originally Posted by Shaunster View Post
    Now the engine is in the car it’s making 284bhp and 197ft/lbs
    I'm not sure I understand how it works down from flywheel figures anyway. But I know you can lose a sizeable amount down through the drive train.
    Last edited by rallyrob; 16-01-2019 at 11:48.

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    Engine dyno vs in car figures

    Quote Originally Posted by rallyrob View Post
    My understanding is this is both sets of figures.

    This is the engine on the dyno



    And this is the figure at the wheels with the engine in the car.



    I'm not sure I understand how it works down from flywheel figures anyway. But I know you can lose a sizeable amount down through the drive train.
    Exactly at the wheels must include losses. Dyno will have none. Unless they have calculated the losses and are still missing loads of power ?


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    Re: Engine dyno vs in car figures

    Different dynos (completely different in this case), different days, different atmospherics = different results. Only way to be sure is use the same dyno everytime for everything and even then you'll still get % variances. Most chassis dynos will use the rollers to drive the wheels on the down run to get an idea of transmission losses - 30 - 40hp doesn't sound outrageous bearing in mind to two figures could be high / low in comparison!

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    Engine dyno vs in car figures

    All flywheel figures, and drivetrain loses properly measured on run down, not calculated.

    Iím sure the builder would have had a dyno manifold, and the engine now has a Simpson 4-2-1 on. Maybe something there?

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    Re: Engine dyno vs in car figures

    Quote Originally Posted by Shaunster View Post
    I’m sure the builder would have had a dyno manifold, and the engine now has a Simpson 4-2-1 on. Maybe something there?
    absolutely, even more so because in the dyno the exhaust will be totally different, if not non existant

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    Engine dyno vs in car figures

    Has anyone got first hand experience of something like a millington before and after? Iíd had a 20bhp loss in my head, just surprised itís as much as that.

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    Re: Engine dyno vs in car figures

    I've recently had a 2.1 Pinto dynoed at 153bhp at the flywheel, with 96bhp at the wheels. However, that then prompted me to look at the excessive drivetain losses seen. Turns out my left hand rear caliper was binding on.
    Although the RR session was worthwhile in balancing my carbs out and sorting my fuel mixture out, I had no idea my brake was binding before this. Click image for larger version Name:	2nd run~01~01.jpg Views:	292 Size:	56.3 KB ID:	83500

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    Re: Engine dyno vs in car figures

    I can hardly believe these engines can make 320 Bhp and 225 Nm from 2,4 Ltr. At what kind of RPM is this engine making 320 Bhp? Specially the torque sounds very high. That's 308 Nm without a turbo !!!!

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    Re: Engine dyno vs in car figures

    Ive seen a few duratecs make 300 bhp or over at dave walkers, but they all needed around 10,000 rpm to do it

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    Re: Engine dyno vs in car figures

    These are about the numbers I had in mind. Fortunately, once you want to upgrade from 300 to 320 you really need something more as extra 2įadvance. It's still miles away.

    I bet they where not making 225 ft/lbs.

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    Re: Engine dyno vs in car figures

    Get it all the time at work on both car and bike dyno, the car world is obsessed with crank figures and bikes are more wheel hp.
    see alot of bike engine cars and its dodgy doing coast down runs as the clutch release doesn't always survive so we dont offer it, all our figures are wheel figures and are generally iro 10% below crank figures

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    Re: Engine dyno vs in car figures

    That's what drives the car along so should be the only pertinent measure............as long as no one changes the diff, the tyre (size / aspect / pressure) etc!

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    Re: Engine dyno vs in car figures

    Had my Pinto dyno'd at 189hp at the flywheel and then 132hp at the wheels

    57hp seems like a lot but i was told 30% loss is normal

    Different operator though

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    Re: Engine dyno vs in car figures

    Quote Originally Posted by Matt75 View Post
    Had my Pinto dyno'd at 189hp at the flywheel and then 132hp at the wheels

    57hp seems like a lot but i was told 30% loss is normal

    Different operator though
    Back in the day I chassis dyno'd my std RS2 which Ford quoted 110 crank hp and the rollers said 90hp so about 18-20% loss - 30% is NOT normal IMO!

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    Re: Engine dyno vs in car figures

    Back in the 80's the average Road Rally Pinto had approx 125 to 130 bhp at the wheels which we estimated to be between 150 and 155 bhp at the flywheel.

    A few years ago I witnessed a Pinto on 45's and a Burton 40/41 cam on an accurate calibrated static dyno and that made 160 bhp. The operator said that power was typical of an engine with a period cam in of the time.

    I certainly believe Katana's 18 to 20% loss is not too far off.

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    Re: Engine dyno vs in car figures

    One thing to bear in mind is that transmission losses shouldn't vary much ie. if an engine dyno says you have 150hp and a chassis dyno says 120hp is hitting the tarmac then the loss is 30hp or 20%. But if you up the engine to 200hp you should still only suffer a 30hp loss and this only now equates to 15% ! !
    So IMO, % losses can be a bit misleading - probably why we bikers like rear wheel hp figures - level playing field (btw my bike has 370hp @ rear wheel)

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    Re: Engine dyno vs in car figures

    Its impossible to make comparisons because so many dyno's read differently, the important thing is to have accurate data logging, a good dyno operator and a dyno that reads consistently to measure even the slightest change, and use the same dyno when carrying out development work. It's a tuning tool, people get hung up on chasing figures instead of using it properly.

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    Re: Engine dyno vs in car figures

    Quote Originally Posted by katana View Post
    (btw my bike has 370hp @ rear wheel)
    I think i'll add a % transmission lose - chains are really inefficient LOL! - say 20% ........ WOW 445hp - I like that number!

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    Re: Engine dyno vs in car figures

    Quote Originally Posted by katana View Post
    I think i'll add a % transmission lose - chains are really inefficient LOL! - say 20% ........ WOW 445hp - I like that number!
    Now you're just showing off...

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    Re: Engine dyno vs in car figures

    Quote Originally Posted by Forest_rallying View Post
    Back in the 80's the average Road Rally Pinto had approx 125 to 130 bhp at the wheels which we estimated to be between 150 and 155 bhp at the flywheel.

    A few years ago I witnessed a Pinto on 45's and a Burton 40/41 cam on an accurate calibrated static dyno and that made 160 bhp. The operator said that power was typical of an engine with a period cam in of the time.

    Sorry for a daft question, but is a static dyno an engine Dyno then?

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    Re: Engine dyno vs in car figures

    Spot on - same by a different name. Just like Rolling Road dyno's can be termed Chassis dyno's.

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    Re: Engine dyno vs in car figures

    Quote Originally Posted by rallyrob View Post
    Sorry for a daft question, but is a static dyno an engine Dyno then?
    Yes.

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    Re: Engine dyno vs in car figures

    Quote Originally Posted by katana View Post
    One thing to bear in mind is that transmission losses shouldn't vary much ie. if an engine dyno says you have 150hp and a chassis dyno says 120hp is hitting the tarmac then the loss is 30hp or 20%. But if you up the engine to 200hp you should still only suffer a 30hp loss and this only now equates to 15% ! !
    So IMO, % losses can be a bit misleading - probably why we bikers like rear wheel hp figures - level playing field (btw my bike has 370hp @ rear wheel)
    These rolling road losses are mainly "tyre to roller losses", not transmission losses. I regular use a gearbox on my engine dyno to keep the dyno speed lower and so I'm able to measure lower powered engines because my dyno's minimum load is a little high. If I measure an engine direct or in 3th gear over a T9 gearbox, the difference is very very little (biggest difference where torque is highest but we talk about 1 - 2 Nm or so). Honest, if you would loose 10 Kw over a gearbox, it will boil your 1,5 Ltr oil in 1 minute. Let alone 30 Kw. The tyre losses increase with speed, measure the same car in 3th of 4th gear and you will have different wheel horse power and different losses (calculated flywheel power will be approx the same).

    BTW, I would like to have a bik engine with 370 Bhp. Would already be happy if my Rover V8 would make 250 Bhp.

    So telling people, measuring with a rolling road is the power what you really got on your rear wheels is also far from true. Change your tyres or put more air into them does not change anything to the power at the rear wheels but it does make a big difference in measured power at the wheels.

    I did found out, the speed I measure the power with (time needed to go from 1000 to 8000 RPM) does have a big influence. I can set from zero to 80% speed. The faster you go, the less reliable. If you measure for example at 50% and after the same engine at 30% the torque lines are usual not the same. The slower you go, the more steady the reading. Rolling road dyno's usual measure very fast compared with what we call a dyno run.
    Last edited by onyd; 18-02-2019 at 20:19.

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    Re: Engine dyno vs in car figures

    You have more car dyno experience than I so I cannot argue with the points you make but up until about ten years ago bike chassis dynos were pure inertia types and a run took a few seconds if you were lucky. Thankfully load cell eddy-current dynos started appearing - the Dynojet250i was the first to reliably record upto 250hp with auto increasing of load to allow extended run time. A tuner I know has worked closely with Dynojet to produce the first 500hp, 750 and latterly 1000hp bike chassis dynos - he is currently pushing the latter to the limits having recorded 900+hp from a 1600 turbo busa motor - this is a beast to be near during a run and its back to taking seconds - enjoy......
    https://www.youtube.com/watch?v=BMJd...&start_radio=1

    But until folks just use a dyno as just a tool and keep using the same tool and operator, the results can only be compared to itself in previous runs - atmospheric conditions - temps and pressures - should be auto corrected. The amount of strapping / restraint just to stop wheel/tyre slip makes tyre pressure largely irrelevant! But agreed at lower less extreme outputs gear ratios, diff ratios and tyre pressures will have an effect - easy fudge factors by unscrupulous operators!
    Last edited by katana; 18-02-2019 at 21:55.

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    Re: Engine dyno vs in car figures

    Totally, agree, at least you need the same dyno to compare, and dyno operator is very important.

    No idea about the wheel losses in bike tuning rolling road but with cars, it is dramatic.

    Would love to have a bike with this kind of power !!!

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    Engine dyno vs in car figures

    Just to let everybody know (even though this thread has gone on a MASSIVE tangent from the original question &#128580 that the exhaust manifold in the car was choking a load of power.

    We swapped it for a bespoke unit from BTB and the engine picked up 28bhp at 8300rpm and 19ft/lbs at 6200rpm

    Just goes to show that off the shelf manifolds arenít suitable for race engines and you should have what your engine builder designed the combination to work with!

    Going back to the original question the power figures have now moved to 320bhp and 225ft/lbs on the engine dyno, to 312bhp and 216ft/lbs in the car. Which is much more what we were expecting!

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    Re: Engine dyno vs in car figures

    Great result, glad you were able to work out what the issue was and fix it.

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    Re: Engine dyno vs in car figures

    Quote Originally Posted by Shaunster View Post
    Going back to the original question the power figures have now moved to 320bhp and 225ft/lbs on the engine dyno, to 312bhp and 216ft/lbs in the car. Which is much more what we were expecting!
    I'd say that's more than bloody impressive - to only lose 5% through transmission, axle and wheels is super efficient!

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    Re: Engine dyno vs in car figures

    Yeah I spoke with SBD about the quoted power figure and they believe the engine builder they recommended has a dyno thatís on the conservative side. And I also believe the weather was spot on when it went in for its last rolling road session, 12 degrees outside and not much humidity. Probably the best of all conditions.

    Having said that, tractive box, tractive diff, high spec axle. I sure it wasnít only 5% loss, but I doubt it was the usual 15% either, etc.

    itíd be interesting to do test after test to see how it performs under all conditions but who knows!

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