hey there jim, just reading up on whats been goin on around here lately (been away) and saw your findings. very nice results imo. just for my own curiosity though would the fact that ar hp figures always state higher then they actually are ie. your sz example, have to do with the fact that they possibly dyno their engines without accessories ie. alternater etc etc. realli like to hear your opinion on this one? and if so is there a general agreement between manufactures to dyno all engines without accessories and the like or would you say that is up to the manufactures discretion, so that one car maker may give a hp figure with and one may give a figure without. maybe a bit of a off topic/silly question but its been on my mind for a while actually.
patzo_3l
3l gtv6 turbo 85'
2006 147 gta selespeed
1990 75 twinspark
1998 spider
2.0l gtv 85'
33 1.7ie
3l gtv6 turbo 85'
2006 147 gta selespeed
1990 75 twinspark
1998 spider
2.0l gtv 85'
33 1.7ie
It all has to do with the particular method of measurement used, EEC, ISO, SAE, JIS, DIN etc...They each stipulate with what accessories the measurement is to be carried out and under what environmental conditions. In Europe and most of the industry, the EEC method has prevailed as it is the one closest to actual engine operating conditions. In some systems, they remove the alternator and the water pump...supplying coolant and power from an outside source, but all systems are rated without any power steering or other servo pumps connected. Thankfully, to avoid confusion everyone states which system their claims correspond to, as a bare power number is not very meaningful. Roller dyno figures are usualy DIN numbers as a complete vehicle is obviously involved.
Another variable not many people are aware of is the effect of the roller diameter of a chassis dyno. Small rollers (up to ~24" diameter, usually twin ones) are suited for small to moderate power levels and large ones (~40" or more, single) are suited for powerful engines. This relation has much to do with the accuracy of the results. Dyno makers advise all buyers of the capabilities of their products but buyers of one or the other type aren't going to turn customers away now, are they? just Google around the various makers and you will find all kinds of info on this.
Jim K.
Another variable not many people are aware of is the effect of the roller diameter of a chassis dyno. Small rollers (up to ~24" diameter, usually twin ones) are suited for small to moderate power levels and large ones (~40" or more, single) are suited for powerful engines. This relation has much to do with the accuracy of the results. Dyno makers advise all buyers of the capabilities of their products but buyers of one or the other type aren't going to turn customers away now, are they? just Google around the various makers and you will find all kinds of info on this.
Jim K.
Jim,
Why not go for one of those hub dynos? I think you posted the result on a dynapak and you had 199 wheel bhp and the flywheel output was rated at 234+ bhp? A little optimistic on the flywheel side, but wouldn't the hub dyno be the dyno of choice to avoid variables like roller size, tire tread, tire pressure?
If I am not mistaken the rototest dyno is also a hub type? They have lots of dyno readings on their website, even for Alfas.
Why not go for one of those hub dynos? I think you posted the result on a dynapak and you had 199 wheel bhp and the flywheel output was rated at 234+ bhp? A little optimistic on the flywheel side, but wouldn't the hub dyno be the dyno of choice to avoid variables like roller size, tire tread, tire pressure?
If I am not mistaken the rototest dyno is also a hub type? They have lots of dyno readings on their website, even for Alfas.
That was the previous engine and ~235hp was after mapping on the hub dyno (206hp on the carmag dyno). After seeing the obviously inflated power numbers, I asked about losses and the guy said he used 18.5% as routine for rwd cars, but he can set loss % to any number I would like. That didn't seem right to me either; how on earth could I come up with the correct figure?
Recently, the same guy opened his own business and bought a Rototest (hub type). I have no info so far about what this rig reads or how good it is; I know they're good machines though. I had already made a deal with the carmag dyno people and they would also write an article with power measurement info for the book, besides mapping the ECU for all tests. So, that part is set. Just for comparison though, I will go to the Rototest once and see what it reads. Will let you know when it happens.
Jim K.
Recently, the same guy opened his own business and bought a Rototest (hub type). I have no info so far about what this rig reads or how good it is; I know they're good machines though. I had already made a deal with the carmag dyno people and they would also write an article with power measurement info for the book, besides mapping the ECU for all tests. So, that part is set. Just for comparison though, I will go to the Rototest once and see what it reads. Will let you know when it happens.
Jim K.
Whenever we talk prices we must take into account the std cost of living in a particular country (... 
) Unfortunately its the only way to determine if something costs 'very little' or 'too much'. I know its difficult to do, but having lived in different countries I have a better idea of cost and value. 100Euros in Switzerland is very little while in Greece its about 1/6th what a sales clerk in a dept. store makes a month (net)!
Dyno and mapping (approx. 2hrs worth) runs to about 350Euros here. Expressed in US$ its about 30% more ($455) with the going ex.rate.
Jim K.
) Unfortunately its the only way to determine if something costs 'very little' or 'too much'. I know its difficult to do, but having lived in different countries I have a better idea of cost and value. 100Euros in Switzerland is very little while in Greece its about 1/6th what a sales clerk in a dept. store makes a month (net)! Dyno and mapping (approx. 2hrs worth) runs to about 350Euros here. Expressed in US$ its about 30% more ($455) with the going ex.rate.
Jim K.
