Alex Posted February 3, 2002 Share Posted February 3, 2002 HKS seem to go to 272deg at most is there a reason why there arn't 280 or 290deg cams. Just curious as then you could get some custom made "race" cams for serious track work to mainly help out the restrictive exhaust port. I was thinking a 264i and a 280e cam set just to keep it drivable on the road and make it unique (Edited by Alex Holdroyd at 11:09 pm on Feb. 3, 2002) Link to comment Share on other sites More sharing options...
Rich J Posted February 4, 2002 Share Posted February 4, 2002 Too much duration means the inlet and exhaust cams will over lap on opening too much and blow all the nice air your turbo just did all that hard work to shift straight out the exhaust so there's a limit on what is worth having as far as duration on a turboed car (N/A cars can have longer durations, the JUN ones for the Integra Type R come on a 304deg duration in top spec) Link to comment Share on other sites More sharing options...
Alex Posted February 4, 2002 Author Share Posted February 4, 2002 Cheers for that So does that mean 272 is the max or just a safe place to stop? Link to comment Share on other sites More sharing options...
Simon Posted February 7, 2002 Share Posted February 7, 2002 Quote: from HardHead42 on 7:40 pm on Feb. 4, 2002[br]Too much duration means the inlet and exhaust cams will over lap on opening too much and blow all the nice air your turbo just did all that hard work to shift straight out the exhaust And all that unburnt petrol as well, (expensive). Link to comment Share on other sites More sharing options...
Adam W Posted February 7, 2002 Share Posted February 7, 2002 You'd get flames out the back though . . . Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 7, 2002 Share Posted February 7, 2002 Quote: from Alex Holdroyd on 11:09 pm on Feb. 3, 2002[br]HKS seem to go to 272deg at most is there a reason why there arn't 280 or 290deg cams. Just curious as then you could get some custom made "race" cams for serious track work to mainly help out the restrictive exhaust port. I was thinking a 264i and a 280e cam set just to keep it drivable on the road and make it unique (Edited by Alex Holdroyd at 11:09 pm on Feb. 3, 2002) Well Mr Holdroyd, you sure asking some deep questions these days. Very simplistically HKS will have arbitrarily have chosen these maximum figures for 2 rreasons. One will be the ability to give good idle and a reasonable chance of running on stock ECU settings, the second will be no danger of valve to piston interference. Raise lift and duration and events within the combustion chamber can become very mechanically close to interference, or indeed interference can occur. then pistons or even cylinder walls can need machining. Durations of well over 300 degrees and lifts of 14 mm or more are used on race turbo engines, but you need much bigger exhaust housings on the turbos, very low restriction exhausts, and a bottom end that will rev to beyond 9000 to get the most out of them, assuming the valves, ports amd manifolds will flow enough gas to feed the chambers. Forget an idle, there won't be one, and fuel consumption will be horrific. So, as with EVERY aspect of an engines design, it's a compromise. Hundreds of books have been written on camshft design, and evem now, with computer simulation, it's still regarded as a bit of a black art. 272 degrees, in the grand scal of things, on a 3 litre engine, is still very tame though. You could still keep some drivability with more duration and lift. The constrictive exhaust housings of the stock turbos are a limitation. i suspect the UK / USA turbos use a bigger housing to go with their increased duration cam. Link to comment Share on other sites More sharing options...
Alex Posted February 8, 2002 Author Share Posted February 8, 2002 Thanks Chris, I was hoping you'd pick this thread up! I don't mind the Turbo's being the restriction as they are "relatively easy to replace. But having a longer duration exhaust cam will I think be benefitial. 272i/290e (yep they just got wilder) cams with a mild 9mm lift should keep the engine reliable without putting too much stress on the valve springs. If I wanted a cam company like Kent Cams to make me some custom cams what information would I need to give them? (Edited by Alex Holdroyd at 5:31 pm on Feb. 8, 2002) Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 8, 2002 Share Posted February 8, 2002 Quote: from Alex Holdroyd on 5:30 pm on Feb. 8, 2002[br]Thanks Chris, I was hoping you'd pick this thread up! I don't mind the Turbo's being the restriction as they are "relatively easy to replace. But having a longer duration exhaust cam will I think be benefitial. 272i/290e (yep they just got wilder) cams with a mild 9mm lift should keep the engine reliable without putting too much stress on the valve springs. If I wanted a cam company like Kent Cams to make me some custom cams what information would I need to give them? (Edited by Alex Holdroyd at 5:31 pm on Feb. 8, 2002) See what Cosworth profiles exist for the Cossie Sierra turbo engine, and get them to copy one of those. If you are happy to have some pistons machined (and just adding duration MAY neccessitate this anyway, go for more lift. 9mm is pathetic, try for about 11. You will need different valve springs too. What will you do to map it to use the better breathing though? Link to comment Share on other sites More sharing options...
Alex Posted February 8, 2002 Author Share Posted February 8, 2002 I've got that mines unit and I believe there are uprated injectors in there too (I really must whip off the intake and take a look) - so I think there is some give in the system. I was thinking of just the Fields Simple fuel computer or an S-AFC but that'll require a trip to a tuner ehh Chris. I picked 9mm as I understand that the standard exhaust ports are restrictive and arn't much cop beyond 8mm also I believed that the stock springs couldn't take much more so to keep costs down I went for 9. But if I'm going custom then i might as well go the whole hog... retainers, guides, springs. Still thanks for the idea...be good to Ian C's car tomorrow (sat) Link to comment Share on other sites More sharing options...
Ian C Posted February 8, 2002 Share Posted February 8, 2002 Quote: from Alex Holdroyd on 10:14 pm on Feb. 8, 2002[br] Still thanks for the idea...be good to Ian C's car tomorrow (sat) I second that... :biggrin: -Ian Link to comment Share on other sites More sharing options...
Sharpie Posted November 16, 2005 Share Posted November 16, 2005 Hey Alex, HKS must of been on here As they now have 280 deg cams for you! http://www.titanmotorsports.com/hks280176cams.html Not much info around. Link to comment Share on other sites More sharing options...
CJ Posted November 16, 2005 Share Posted November 16, 2005 Thats got to win the title of "oldest thread ressurection" by a mile eh? Link to comment Share on other sites More sharing options...
darren j adams Posted November 16, 2005 Share Posted November 16, 2005 crower do big uns d. Link to comment Share on other sites More sharing options...
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