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Thread: Difference between pub bhp and real bhp?

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    Difference between pub bhp and real bhp?

    Hello all,

    on ebay there is a Pinto/OHC engine for sale with this (see below) powerplot.
    P-Rad = 111 kW -> 151 BHP at the wheels
    P-Verl = 25 kW -> 34 BHP transmission loss
    P-Mot = 136 kW -> 185 BHP at the crank.

    Now P-DIN is listed as 166 kW and P-EC is 162 kW -> 221 BHP.

    Where did the 36 BHP difference come from???

    Regards, Leon.


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    Re: Difference between pub bhp and real bhp?

    See the Air Temp and air pressure that are incorrect. Thus, the correction is too high according to DIN 70020. The diagram is made for dreamers.
    As an example: An engine measured at 13*C / 999mBar = 133,9KW / 182,2PS / 218.1 nM
    at 32*C / 847mBar = 163,1KW / 222PS / 265,7nM

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    Re: Difference between pub bhp and real bhp?

    It could have been a very hot day: temp = 32 C / 847 hPa.
    Diagram itself could be okay.

    From what I now see they corrected the 136 kW to 162 kW by multiplying it by 1013 / 847 as a "correction" to 1 bar airpressure.

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    Re: Difference between pub bhp and real bhp?

    Hi Leon,

    I do believe I know where the extra power comes from. The original engine was original equipped with one carburetor and made 110 Bhp. Now they have fitted 2 carburetors so it's double the power, 221 Bhp. Simple !!!! All numbers in between,.... just accept. You are not supposed to understand them.

    I know the frustration Leon, I'm fighting against these fake figures for a very long time. From the day I got my own dyno. Unfortunately, they seems to believe my story with double carbs faster than what is really going on. There are many way's you can sheet a dyno graph. Big numbers make selling engines easier.

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    Re: Difference between pub bhp and real bhp?

    Whilst we are on the real dyno/pub dyno what does everyone think of the dyno i use for my tunning? I use it to compare figures on from start to finish but i would like to know if the pros think it is accurate or not.


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    Re: Difference between pub bhp and real bhp?

    As long as the dyno is repeatable it is useful for tuning. You need to know your modification was making more or less power. If you dyno is reading 100 Bhp more as what the engine really has, it does not have any influence on the engine tuning themselves. Only, you can't compare with others.

    Please note, a lost of 37 Kw ( 50 Bhp) is what I feel, not realistic. Not sure what RR you are using but I was measuring a lot smaller numbers on my RR. And DIN kW lower as the measured kW should mean it was on a very cold day (but is realistic).

    When I started working on my RR my Capri was making 150 Bhp. After TAE had re-calibrated the RR the same engine made 130 Bhp. I was not slower on the road (nor faster). I do believe you understand what I'm trying to explain.

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    Re: Difference between pub bhp and real bhp?

    If you want to do a simple test to see the dyno is more or less correct. You can fit a Sierra 2 ltr OHC, should read little over 100 Bhp and second ask a Porsche 3600 air cooler to do the same, should read 250 Bhp for the 250 Bhp 3,6 ltr. You got at least an indication.

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    Re: Difference between pub bhp and real bhp?

    Quote Originally Posted by onyd View Post
    If you want to do a simple test to see the dyno is more or less correct. You can fit a Sierra 2 ltr OHC, should read little over 100 Bhp and second ask a Porsche 3600 air cooler to do the same, should read 250 Bhp for the 250 Bhp 3,6 ltr. You got at least an indication.

    the reason why i ask is because they put all types of cars on there and regularly put standard cars on there for a look and come in at just under the standard power. There was a jre 250 bhp 2.0l redtop on there too and that came in at 230bhp. There is no worries any way as i totally understand what your trying to tell me figures mean not a lot to me too, all i know is every time me and my friend strap the escort onto the rollers it drives better and better.

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    Re: Difference between pub bhp and real bhp?

    This the most important, the engine must go faster and faster.

    What make of dyno is this? acceleration dyno? Eddy Current? I had a MAHA (SUN RAM 12) and my power losses where always a lot lower.

    Please note, as you will know, it's not because they have sold an engine for 250 bhp, it's really 250 Bhp.

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    Re: Difference between pub bhp and real bhp?

    Quote Originally Posted by onyd View Post
    This the most important, the engine must go faster and faster.

    What make of dyno is this? acceleration dyno? Eddy Current? I had a MAHA (SUN RAM 12) and my power losses where always a lot lower.

    Please note, as you will know, it's not because they have sold an engine for 250 bhp, it's really 250 Bhp.
    Yeah engine builders claim figures and not often make them any way, i think that the way some engine builders claiming mad figures only survive is because they are selling to people who are already at the top of their driving game. It is a MAHA SUN rolling road,what model it is i don't know.

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    Re: Difference between pub bhp and real bhp?

    Seller now revised his listing; he still states it has 221 bhp but the powerplot has been removed ...

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