dandan Posted January 29, 2004 Share Posted January 29, 2004 Hi people, Can anyone tell me how much the engine rpm drops across each gear change (in a 6 speed manual tt). I wondered if these figures were around somewhere, 1) to save me going out and trying to get them myself (esp due to weather) and 2) not sure how accurate my rev counter is either. Thanks Dan Quote Link to comment Share on other sites More sharing options...
eyefi Posted January 30, 2004 Share Posted January 30, 2004 ive seen it, but cant find it at the moment. Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted January 30, 2004 Share Posted January 30, 2004 Please note the RPM drop will be more dramatic with a lightened flywheel due to the reduced inertia. If you get desperate for them, I have them on another PC. Quote Link to comment Share on other sites More sharing options...
eyefi Posted January 30, 2004 Share Posted January 30, 2004 http://www.boostaholic.com/supra/shiftpoints.html that isn't what i was thinking of but it may do the job. Quote Link to comment Share on other sites More sharing options...
dandan Posted January 30, 2004 Author Share Posted January 30, 2004 Thanks guys, I'm on a stock flywheel at the moment. According to the link the rpm drops change a fair bit depending on the rpm the change ocurs. I can only assume this is due to extra inertia in the rotating assembly at higher speeds. Once I've been back to Thor on Sat and checked my fuelling at around 1.2bar, I'll be looking to work out some ideal shift points. Cheers Dan Quote Link to comment Share on other sites More sharing options...
Ian C Posted January 30, 2004 Share Posted January 30, 2004 By RPM drop I reckon you mean what rpm you'll be doing after changing up a gear compared to what RPM you were doing before you changed up? If so, that's got nothing to do with inertia of the drivetrain (which affects how quickly your RPMs drop when you aren't applying drive) but has everything to do with the gearbox's ratios and the RPM that you shift at. E.g. the RPM drop is about 500rpm per gear if you change up at 2000rpm, whereas a shift from 4th to 5th at 7000rpm produces a huge drop of almost 2000rpm. Off the top of my head, but I'm using these figures as an example. I used to have a spreadsheet with a gearshift/speed/rpm calculator but I think it's on my work PC and I'm not there until monday... -Ian Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted January 30, 2004 Share Posted January 30, 2004 Whilst I agree with what you say Big C, try driving a car with a lightened flywheel and tell me the effect is not significant on the rpm drop. Maybe you can just change gear much faster than me;) Quote Link to comment Share on other sites More sharing options...
Ian C Posted January 30, 2004 Share Posted January 30, 2004 It'll drop rpms faster, but it won't physically change the ratios, you need to be heavier on the throttle during gearchanges to keep the revs up -Ian Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted January 30, 2004 Share Posted January 30, 2004 The theory is perfect, just talking from experience. It really needs full throttle gear shifts, I may look at that with the RLTC. Quote Link to comment Share on other sites More sharing options...
outatime Posted January 30, 2004 Share Posted January 30, 2004 Eyefi was looking into full throttle gear changes through RLTC, sounds a good idea. I don't know how he got on... Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted January 30, 2004 Share Posted January 30, 2004 It's easy enough to do, it just adds another rev limit when the clutch is depressed AFAIK, like the launch, so you keep your foot planted but the RPM would stay at say 4k. It would also keep the load on the turbo. This is my only concern. I don't know what if anything it would do to the longevity of the turbo. Quote Link to comment Share on other sites More sharing options...
eyefi Posted January 30, 2004 Share Posted January 30, 2004 full throttle grear shifts rock, takes some getting used to and a bit of fiddling with the limiter. very wierd at first. i keep meaning to log my boost patterns with this, it maintains better boost through the shift. Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted January 30, 2004 Share Posted January 30, 2004 Eyefi have you got an oil temp gauge? It just worries me that the turbo will be spooling all the time. These worries are probably unfounded, but I would appreicate feed back on temos inc. EGT's Quote Link to comment Share on other sites More sharing options...
eyefi Posted January 30, 2004 Share Posted January 30, 2004 i would imagine it would b better for the turbo, it can keep a more average shaft rpm. probably not too bad on the drivetrain if the limiter is well matched to the shift rpm. clutch probably suffers a little Quote Link to comment Share on other sites More sharing options...
eyefi Posted January 30, 2004 Share Posted January 30, 2004 i seem to b replying just before u post. i have no oil temp, but i only use full throttle change rarely, when really necessary. i have no hard data on egt's, but mine r fine. it never gets very hot. i dont think my guage is fast enough to respond within the part second that its in this state. boost does still drop (not as low) but response after change is better Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted January 30, 2004 Share Posted January 30, 2004 Yeah I thought it was a bit funny. What are the AFR's like when using it? Quote Link to comment Share on other sites More sharing options...
eyefi Posted January 30, 2004 Share Posted January 30, 2004 u can see the limiter's cut effect, normal / lean / normal / lean / normal / lean Quote Link to comment Share on other sites More sharing options...
eyefi Posted January 30, 2004 Share Posted January 30, 2004 u can only see this in the logged graph (iirc 20logs/sec). its not really a lean its an air reading (no combustion or fuel). Quote Link to comment Share on other sites More sharing options...
dandan Posted January 30, 2004 Author Share Posted January 30, 2004 Ian, I've just realised what I posted there in one of my replys. Of course the engine speed drop doesn't change depending rpm's due to inertia. As soon as the clutch is let back up then the gear ratios immediately govern what rpm the engine will do related to the road speed!! I was still half asleep at that point. Working out optimum gearshift points is not going to as straight forward as I thought..... Regards Dan Thanks for everyone elses comments so far.... Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 30, 2004 Share Posted January 30, 2004 Originally posted by Terry S Please note the RPM drop will be more dramatic with a lightened flywheel due to the reduced inertia. If you get desperate for them, I have them on another PC. Ehh? The RPM drop he is aking about (I am sure) is that given and fixed by the gear ratios. Given the boxes ratios it's a pure maths thing to work out. The mass of the flywheel only governs how fast the revs drop whilst between gears. Quote Link to comment Share on other sites More sharing options...
dandan Posted January 30, 2004 Author Share Posted January 30, 2004 Yes that is what I was asking. I think Terry is thinking of something slightly different... - How much the revs would drop whilst the clutch was depressed before re-engaging it again. ie Before the revs are brought up to the speed determined by the gear ratios and road speed. Dan Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted January 30, 2004 Share Posted January 30, 2004 Yeah sorry for the confusion Quote Link to comment Share on other sites More sharing options...
Ian C Posted January 30, 2004 Share Posted January 30, 2004 Keep up Chris, I straightened that confusion out already -Ian Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 30, 2004 Share Posted January 30, 2004 Originally posted by Ian C Keep up Chris, I straightened that confusion out already -Ian Sorry! Bit hassled today, a rhea has had the sleeve out of my overalls (again) and the older male emu has sworn vengence `cos I nicked 5 eggs out of the nest when it went frosty and snowy. He didn't *SEE* me, but he *KNOWS* I did it. I'm watching my *rse, he's up for revenge... Anyway, everythings fed and watered, 3 rats shot that had taken up residence in some old pipe (they refused a rent book, so what do you do...?), and I have found where Mr. Fox is buryng the neighbours fowl, I'm doing a headstone for Foxy as I type Soaked to the skin, shower and down the pub tonight I think Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted January 30, 2004 Share Posted January 30, 2004 Originally posted by Chris Wilson the older male emu has sworn vengence `cos I nicked 5 eggs out of the nest when it went frosty and snowy. He didn't *SEE* me, but he *KNOWS* I did it. I'm watching my *rse, he's up for revenge... It's official, Chris Wilson is Johnny Rotten:D Quote Link to comment Share on other sites More sharing options...
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