mellonman Posted March 29, 2012 Share Posted March 29, 2012 (edited) okay after getting the car in the dyno at austec charity day, i have a question about the torque curve why does it drop off straight away between 1700 - 3000 does this idicate a problem? that is all i have of the torque curve sorry for the poor picture, i did see a thread about something similar some time ago but i cant find it what do you think? Edited March 30, 2012 by mellonman (see edit history) Quote Link to comment Share on other sites More sharing options...
mellonman Posted March 30, 2012 Author Share Posted March 30, 2012 strange no one has a view on this, where else could i ask this question? Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 30, 2012 Share Posted March 30, 2012 Where did that come from? it is rather strange in that the torque and BHP plot cross twice, and for it to drop so low that early makes me think the dyno calibration is wrong, also the later cross point is also low on the RPM scale. Quote Link to comment Share on other sites More sharing options...
Guest Budz86 Posted March 30, 2012 Share Posted March 30, 2012 Could that be low boost on the first turbo? Best person to answer this is probably Dude as it was his dyno. Surprised he didn't have a chat with you on the day but to be fair he was running around all over the place and not watching all the runs. Quote Link to comment Share on other sites More sharing options...
Guest Budz86 Posted March 30, 2012 Share Posted March 30, 2012 Good numbers by the way, your reaction was brilliant! Don't think you expected it to be more than 500 did you? Quote Link to comment Share on other sites More sharing options...
Chucky_waR Posted March 30, 2012 Share Posted March 30, 2012 It's your ecu bud.. You have the same one as mine and know its crap so we both should invest in a decent standalone ecu. I can’t wait to get my hands on a syvecs as soon as I can afford it. It's senseless running big single turbots’ with a crapy ecu. Quote Link to comment Share on other sites More sharing options...
SteveR Posted March 30, 2012 Share Posted March 30, 2012 That's definitely not right and needs sorting ASAP. As an immediate concern though, I would want to know the fuelling (AFR) is ok else there could be damage being done: have you got a gauge? Quote Link to comment Share on other sites More sharing options...
mellonman Posted March 30, 2012 Author Share Posted March 30, 2012 sorry i should of put this is a t67 dbb single turbo aem fic ecu there is alot of timing pulled 3* at absolute air pressure which might be the cause im not too sure, i was more thinking low compression with worn rings then boost is compensating by 3000rpm BUDZ86 yeah i bet me face was a picture was very shocked to be fair was expecting 470 max so creamed my pants a little Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 30, 2012 Share Posted March 30, 2012 It's your ecu bud.. You have the same one as mine and know its crap so we both should invest in a decent standalone ecu. I can’t wait to get my hands on a syvecs as soon as I can afford it. It's senseless running big single turbots’ with a crapy ecu. His piggyback should not even need any map changes in the closed loop area, which is where the problem lies, and if it is, then that will be the answer, as it will be fighting the closed loop of the std ECU, but it would have to be way out for things to look that bad, which is why i suggested dyno calibration, however if its was on the dyno day i doubt thats the case. Quote Link to comment Share on other sites More sharing options...
mellonman Posted March 30, 2012 Author Share Posted March 30, 2012 That's definitely not right and needs sorting ASAP. As an immediate concern though, I would want to know the fuelling (AFR) is ok else there could be damage being done: have you got a gauge? yep i have a afr and its does go to about 14.0 on pull off at that low cross over but then goes back to stoich (Closed loop) what are your thoughts what makes you worry so much about it? even when i was hybrids at supra pod last year i could tell that it had that drop in torque as was always playing catch up Quote Link to comment Share on other sites More sharing options...
garethr Posted March 30, 2012 Share Posted March 30, 2012 ...the later cross point is also low on the RPM scale.Since the dyno calculates BHP from torque, the graphs have to cross at 5252rpm. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 30, 2012 Share Posted March 30, 2012 Since the dyno calculates BHP from torque, the graphs have to cross at 5252rpm. Is that not what i just said, by saying its low on the graph RPM:blink: Quote Link to comment Share on other sites More sharing options...
mellonman Posted March 30, 2012 Author Share Posted March 30, 2012 (edited) Is that not what i just said, by saying its low on the graph RPM:blink: but they do cross at 5252, it just does that dip at the start which it then has to cross back to cross again at 5252 hope everyone understands what i mean Edited March 30, 2012 by mellonman (see edit history) Quote Link to comment Share on other sites More sharing options...
SteveR Posted March 30, 2012 Share Posted March 30, 2012 yep i have a afr and its does go to about 14.0 on pull off at that low cross over but then goes back to stoich (Closed loop) Well that sounds ok - in that case, there may be a very simple explanation here - was the car WOT for the full rev range or was it trundling along at partial throttle until it got up past 3000rpm? even when i was hybrids at supra pod last year i could tell that it had that drop in torque as was always playing catch up Hmm that does not sound so good. I've never seen torque curve drop like that - why would an engine struggle to produce more torque as it gets out of idle revs and towards the area when it's more into its stride (unless the turbo is hugely laggy?). I worry just because I do - anything modified (even when modified well) is arguably more prone to go wrong and when it does, do more damage than stock! If you've got an AFR gauge though you have peace of mind for what I was worrying about - i.e. under-fuelling. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 30, 2012 Share Posted March 30, 2012 but they do cross at 5252, it just does that dip at the start which it then has to cross back to cross again at 5252 hope everyone understands what i mean Its the fact that it crosses twice before then, that gives rise for concern. Quote Link to comment Share on other sites More sharing options...
garethr Posted March 30, 2012 Share Posted March 30, 2012 It's the fact that it crosses twice before then, that gives rise for concern.Sorry, I misunderstood. I thought you were talking about after the dip. No idea about the dip, though... wheelspin? Quote Link to comment Share on other sites More sharing options...
SteveR Posted March 30, 2012 Share Posted March 30, 2012 Its the fact that it crosses twice before then, that gives rise for concern. I'd be inclined not to worry about the graph layout so much: you could probably make most people's torque/bhp plot do that crossover if you use 2 vertical axis with different scales on each (which this graph has got). Power is a function of torque and gear - it's the dip in torque that is odd (and makes the power/torque crossover so apparent so I do take your point on board ). Quote Link to comment Share on other sites More sharing options...
mellonman Posted March 30, 2012 Author Share Posted March 30, 2012 Well that sounds ok - in that case, there may be a very simple explanation here - was the car WOT for the full rev range or was it trundling along at partial throttle until it got up past 3000rpm? steve i think that you have just answered the question right there, could it be like that because its an auto and maybe they didnt go wot due to kick down? Quote Link to comment Share on other sites More sharing options...
SteveR Posted March 30, 2012 Share Posted March 30, 2012 steve i think that you have just answered the question right there, could it be like that because its an auto and maybe they didnt go wot due to kick down? aha! You can probably ignore it then! Job's a good 'un! Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 30, 2012 Share Posted March 30, 2012 Ahh! Auto, that eureka moment, probably help if you mentioned that to start;) Quote Link to comment Share on other sites More sharing options...
mellonman Posted March 30, 2012 Author Share Posted March 30, 2012 Ahh! Auto, that eureka moment, probably help if you mentioned that to start;) i know what a pleb i am so sorry for wasting your time : i did miss alot out on that first post rookie mistake thanks alot guys Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 30, 2012 Share Posted March 30, 2012 You're all wrong, and the graph is actually right Most dyno charts don't go anywhere near the low end rpms that this chart does, so this is unfamiliar territory for most of us, myself included. So I looked up the BHP formula, and the way you can work out torque from it: Torque = (5252 * BHP) / RPM If you take the 1500rpm load site, you've got 75bhp. That's 260ftlbs of torque needed to generate that, at those revs. And that's where the torque line is (note the torque scale on the right starts at 210ftlbs). So we move right on the graph a bit to 2000rpm, and you've got about 87bhp. That's 228ftlbs. Because the revs have increased proportionally far more than the power level, the torque figure needed to give that power level actually drops It's only once the power starts ramping up again, say at 3000rpm when you're at 135bhp, that the torque figures are increasing again. BHP is simply the result of the above formula, it's the torque that's measured on a dyno. Whether the dyno measured your torque figures at those low rpms correctly or not isn't the issue here - the calculations are correct and bizarrely, the torque figures drop before climbing again. How about that -Ian Quote Link to comment Share on other sites More sharing options...
mellonman Posted March 31, 2012 Author Share Posted March 31, 2012 Ian so your saying theres a issue ? so its not the torque converter doing it then ? Quote Link to comment Share on other sites More sharing options...
SteveR Posted March 31, 2012 Share Posted March 31, 2012 ...bizarrely, the torque figures drop before climbing again. How about that The thought crossed my mind, that we don't usually see dyno graphs showing outputs that low down the rev range, but I still wasn't convinced torque would dip. According to *pinch of salt* Wikipedia, this is the torque output for a BMW K1200R (motorbike), and very strange things happen with the torque curve(s!) low in the revs range. Very odd! Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 31, 2012 Share Posted March 31, 2012 Ian so your saying theres a issue ? so its not the torque converter doing it then ? I'm specifically saying that there ISNT an issue, you can relax. It's just an artefact of the power the dyno reported that low down the rev range. Quote Link to comment Share on other sites More sharing options...
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