Adam W Posted November 27, 2003 Share Posted November 27, 2003 It seems to me that converting backwards up the drivetrain is fairly immaterial - it's the only power which reaches the wheels that does you any good, so that's what you should quote/be interested in. Quote Link to comment Share on other sites More sharing options...
Patrick_Devlin Posted November 27, 2003 Share Posted November 27, 2003 Originally posted by Adam W It seems to me that converting backwards up the drivetrain is fairly immaterial - it's the only power which reaches the wheels that does you any good, so that's what you should quote/be interested in. OK thats a fair point and as long as we ensure we all present our figures using one format we're fine. I think the reason we're so hung up on crank figures is that they are (supposedly) what the manufacturers give, so we're trying to gauge how our cars match up to other vehicles... so how much power at the hubs does a 355 or a Tuscan have as stock? (Lets not start a "all that matters is the driver" debate either ) Quote Link to comment Share on other sites More sharing options...
Wipeout Posted November 27, 2003 Share Posted November 27, 2003 "Quote" Interesting thread. Everyone should post their dyno graphs into the Dyno Results thread in the multimedia gallery, that would make them all a lot easier to compare - if anyone needs some webspace to host them on they can either use http://www.showoffyourcar.com or send them to me to host... __________________ My Dyno plots are here if anyone want a look. My Web Site Quote Link to comment Share on other sites More sharing options...
Adam W Posted November 27, 2003 Share Posted November 27, 2003 Originally posted by Patrick_Devlin OK thats a fair point and as long as we ensure we all present our figures using one format we're fine. I think the reason we're so hung up on crank figures is that they are (supposedly) what the manufacturers give, so we're trying to gauge how our cars match up to other vehicles... so how much power at the hubs does a 355 or a Tuscan have as stock? (Lets not start a "all that matters is the driver" debate either ) Yeah, I can see that side of the coin as well, but I reckon it would be easier if all modded cars were compared using rwhp, and there is usually a set of dyno figures for most standard sports cars floating about. ie someone will have dynoed a stock tuscan or ferrari or whatever so you should be able to find out their rwhp. Quote Link to comment Share on other sites More sharing options...
Mark Ayling Posted November 27, 2003 Share Posted November 27, 2003 Originally posted by Wipeout My Dyno plots are here if anyone want a look. My Web Site The point of my post was that it would be nice to see them all in one place If you have them on your webspace you could link to them in the Dyno Results thread... Quote Link to comment Share on other sites More sharing options...
Tannhauser Posted November 27, 2003 Author Share Posted November 27, 2003 Originally posted by dandan I don't think the straight percentage correction (eg add 15%) is a valid one. The idea that a high powered well built engine and drivetrain could lose a lot more power than an older car with much lower power does not seem logical. I think we should consider a certain hp loss figure across all mkiv's and also a percentage loss on top of that to account for what extra power is indeed lost as crank power increases (be it increased heat/noise/vibration etc) Having played around a bit i think this seems a fairly useful "correction": (Hub Horsepower x 1.06) + 18 = Flywheel power eg Hub Flywheel 280 315 300 336 330 368 350 389 380 421 400 442 430 474 450 495 You may or may not agree with this, and i'm sure some people may think the figures are too low. However, don't forget Bobbeh's car was only losing 30-35bhp from flywheel to hubs. (Assuming healthy flywheel power of 320-325). What do you reckon? Within the range of values that you've cited, using a fixed % conversion (such as x1.11 I suggested) or using your (x1.06 + 18) doesn't seem to yield very different results. The fixed % conversion I suggest comes out with 311 flywheel bhp for 280 rhhp and 499 flywheel bhp for 450 rhhp. So I think that within a relatively narrow range of figures, we're in substantial agreement. Although we know rwhp is 'what counts', just for entertainment value it's nice to have a guesstimate about our crank bhp. I'm forever being asked about the bhp of my car, but I don't think they mean 'at the wheels'. Regards, Cliff Quote Link to comment Share on other sites More sharing options...
dandan Posted November 28, 2003 Share Posted November 28, 2003 Hi Cliff, I know what you're saying about the figures being close but I just don't agree with the straight % loss idea. It seems daft to automatically assume that two cars of same age, condition and mileage could differ so much when just applying a straight %. I'm not saying it's miles off or anything but just not quite how i see it. I fully appreciate we/you are only talking about a rough idea of flywheel hp so it's not really all that important, just nice to "compare" to other cars. 1.11 260 hhp = 289bhp (29hp loss) 480 hhp = 533bhp (53hp loss) ...... 24hp extra loss 1.06 + 18 260 hhp = 294 bhp (34hp loss) 480 hhp = 527 bhp (47hp loss) ...... 13hp extra loss The second way (ie not straight %) reduces the extra losses automatically added using 1st method. Seems more realistic to me. Think how much heat 1hp is equivalent to. I think 1hp=0.875kW. We all know how much heat a 2kW fan/gas heater pushes out. Imagine and extra 20kW or so (of power losses) and then it's easy to appreciate how much power we're talking about being lost thru the drivetrain. I know it's all fairly pointless and not proven (need an engine dyno and thor dyno with a few engines of different specs to get a real indication) so no point argueing over it but still Anyway I'm happy enough: 332hhp and 347lbft is pleasing enough at 1.05bar with top cat still in !! Plenty more potential at 1.2 bar with full decat. (Any news CW??) Quote Link to comment Share on other sites More sharing options...
Patrick_Devlin Posted November 28, 2003 Share Posted November 28, 2003 I'm happy to go with those calculations. I was going on a straight 10% loss, so with this equation I get a rough crank figure of 407bhp. Quote Link to comment Share on other sites More sharing options...
dandan Posted November 28, 2003 Share Posted November 28, 2003 Yeh i'd be happy if someone said the Thoe figure is actually equiv to flywheel figure as 331bhp at 1.05bar seemed good to me, never mind the fact that it was at the hubs! Great having a beast like the Supe isn't it, my mate has an STi5 and he's well jealous of the power i'm putting down Quote Link to comment Share on other sites More sharing options...
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