samsupra37 Posted February 27, 2007 Share Posted February 27, 2007 As stated in a previous thread I don't know how to work out power at the fly wheel. So if a car was running a carbon carbon clutch with 6speed box and its hub dyno figure was 100 rear hub bhp. What would the recognised formula be to get a) rear wheel figure b) fly wheel figure numbers won't count need the % using the basic info given.(Please note this is not a joke or intended as a wind up I realy want to know then maybe we will all sing from the same song book) Link to comment Share on other sites More sharing options...
JamieP Posted February 27, 2007 Share Posted February 27, 2007 Id say the rhhp is about the same as the fly figure;) lets see what Gamers car makes at there dyno day as we know what figures he has had on marlins and SRR. Link to comment Share on other sites More sharing options...
Jake Posted February 27, 2007 Share Posted February 27, 2007 Id say the rhhp is about the same as the fly figure Yeah, I reckon that's about right Link to comment Share on other sites More sharing options...
Alex Posted February 27, 2007 Share Posted February 27, 2007 If it wasn't a HUB dyno - I'd say 8-12% for transmission loss on a manual. The lighter the components in the drive train the lower the loss. But I'd stand by my ascertion that the Thor Hub dyno seems to produce Fly figures not RWHP figures. Link to comment Share on other sites More sharing options...
Bobbeh Posted February 27, 2007 Share Posted February 27, 2007 Its not gonna be the same as the flywheel as you're still gonna get the drivetrain loss. It takes out the tyre and wheel differences which is useful. I tend to use 18% loss for a manual on dyno dynamics rr and closer to 10% on a hub dyno like Thors, based on my dyno runs using each system. Link to comment Share on other sites More sharing options...
Marty Posted February 27, 2007 Share Posted February 27, 2007 Why do people bother quoting flywheel horsepower? its what is a the wheels that matters Link to comment Share on other sites More sharing options...
samsupra37 Posted February 27, 2007 Author Share Posted February 27, 2007 If it wasn't a HUB dyno - I'd say 8-12% for transmission loss on a manual. The lighter the components in the drive train the lower the loss. But I'd stand by my ascertion that the Thor Hub dyno seems to produce Fly figures not RWHP figures. Alex I wasn't disputing what you said in the last thread this is to assertain exactly what I should be using as a formular to work it out Link to comment Share on other sites More sharing options...
Alex Posted February 27, 2007 Share Posted February 27, 2007 Alex I wasn't disputing what you said in the last thread this is to assertain exactly what I should be using as a formular to work it out I know - which is why I added what I'd expect off a normal dyno Link to comment Share on other sites More sharing options...
samsupra37 Posted February 27, 2007 Author Share Posted February 27, 2007 Ok, so if you think it measures fly not rear why do they put the hubs at the back..... Yes I know a typical blonde question...but bstay with me I shall get there in the end;) Link to comment Share on other sites More sharing options...
JamieP Posted February 27, 2007 Share Posted February 27, 2007 Why do people bother quoting flywheel horsepower? its what is a the wheels that matters Seems all dyno's are different, when joe went to srr dyno he got a huge improvment in rwhp over the dyno that TF use but the fly figures was exactly the same.. All these figures are bollox imo, if you are happy with how the car performs thats what matters, dyno's are for tunning imo. Link to comment Share on other sites More sharing options...
samsupra37 Posted February 27, 2007 Author Share Posted February 27, 2007 I agree but every one always asks the question so it would be good to have a recognised formula to work with...it just seems rediculas (spelt wrong I'm sorry) that there isn't one layed out for all you use as a bench mark.... As of yet no one has told me what by 100hub bhp car is running at the fly and how they got there..... Link to comment Share on other sites More sharing options...
Homer Posted February 27, 2007 Share Posted February 27, 2007 Ok, so if you think it measures fly not rear why do they put the hubs at the back..... Yes I know a typical blonde question...but bstay with me I shall get there in the end;) Its to keep the customer happy, customer goes there, gets a nice high figure - happy customer means repeat business They're consitently higher results than other reputable dyno operators. From most results I've heard from members that have been there, the rhhp quotes are more or less what you'd expect at the flywheel. Link to comment Share on other sites More sharing options...
Homer Posted February 27, 2007 Share Posted February 27, 2007 As of yet no one has told me what by 100hub bhp car is running at the fly and how they got there..... I don;t think it's going to be possible Sam, only the dyno could really work it out. Alex already mentioned the approximate calculation used when converting a rolling road dyno to flywheel figures, but working out the differences just the wheel would be very difficult indeed. Edited to add - unless anyone has ever taken a completely stock UK spec car there and had it dyno'd. If we assume the flywheel is 326bhp as Toyota quoted, an approx calculation could be worked out. Link to comment Share on other sites More sharing options...
samsupra37 Posted February 27, 2007 Author Share Posted February 27, 2007 I don;t think it's going to be possible Sam, only the dyno could really work it out. Alex already mentioned the approximate calculation used when converting a rolling road dyno to flywheel figures, but working out the differences just the wheel would be very difficult indeed. But I only do difficult....after all I am a woman!!!!!! Link to comment Share on other sites More sharing options...
Marty Posted February 27, 2007 Share Posted February 27, 2007 Guess the main problem is its guess work when working out the fly figure, people know the aproximate transmission losses but not he exact ones so its never going to be right, unless the engine is taken out, and dyno'd. Plus different garages use different dyno techniques etc. As Alex says, if youve changed your clutch, flywheel or prop shaft especially, your transmission losses will change, maybe by a good few percent, which will throw the calculations right out. Your right Jamie, its good for a basic indication but you cant rely on them, they are just mainly really handy for tuning. But its good tellin the lads down the battlecruiser that your car is running a kergillion brake, with the print outs to prove it Link to comment Share on other sites More sharing options...
Thorin Posted February 27, 2007 Share Posted February 27, 2007 http://www.mkivsupra.net/vbb/showthread.php?t=14480 and http://www.mkivsupra.net/vbb/showthread.php?t=21854 for older reading on the topic. Link to comment Share on other sites More sharing options...
Bob Posted February 27, 2007 Share Posted February 27, 2007 Wouldn't the only way to work it out be to use an engine dyno (engine out job, obviously! ), then install the same engine into an otherwise stock car and dyno that both on a hub dyno and a rolling road. Then you can have some true(ish) figures. There you go Sam, another little side project for you and Greg! Link to comment Share on other sites More sharing options...
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