Wez Posted October 14, 2007 Share Posted October 14, 2007 Hey All, Now I have the HKS264/264 cams installed and mapped my power curve doesnt stop climbing, even at 7200rpm its still rising. I dont really want to rev the engine any further so was wondering if there are any tricks to shift the power over to the left a bit, I have been told that this can be done by advancing the intake cam. What are peoples thoughts on this? Link to comment Share on other sites More sharing options...
TLicense Posted October 14, 2007 Share Posted October 14, 2007 I'll be interested in an answer to this too. Link to comment Share on other sites More sharing options...
Wez Posted October 14, 2007 Author Share Posted October 14, 2007 I have heard the downside to this would be a crappy idle but that doesnt bother me. Link to comment Share on other sites More sharing options...
TLicense Posted October 14, 2007 Share Posted October 14, 2007 I'm sure it's nothing that can't be dialled out. Link to comment Share on other sites More sharing options...
Wez Posted October 14, 2007 Author Share Posted October 14, 2007 Having a quick read it would seem a 3 to 5 deg advance would lower peak power about 300 to 500rpm. Link to comment Share on other sites More sharing options...
Pig Posted October 15, 2007 Share Posted October 15, 2007 Im glad you said that, i thought it was just me. My bum sensor tells me it never stops pulling all the way to 7.5 - time to increase the rev limit Link to comment Share on other sites More sharing options...
Ryan.G Posted October 15, 2007 Share Posted October 15, 2007 Cam Timing is something that really needs to be setup on a chassis dyno or an engine dyno to find the perfect setup. To create a faster spooling setup a normal rule of thumb is to advance both cams so that they both open earlier, bringing the power range further down the rpm range but you could loose some top end power. You also might come into problems with compressor surge on a small turbo like a t60-1 if you advance the exhaust cam to much though. With some of the big power mr2's i have mapped i have found that fitting a setup like a 272 intake and a 264 exhaust then leaving the intake along and just advancing the exhaust has made a big difference in spool time while not affecting the power Ryan Link to comment Share on other sites More sharing options...
suprafan72 Posted October 15, 2007 Share Posted October 15, 2007 I'd be very interested to know this allso.... Link to comment Share on other sites More sharing options...
JohnA Posted October 15, 2007 Share Posted October 15, 2007 Wez, advance both cams a bit, otherwise you'd be also affecting overlap (which you may or may not want to do) As Ryan said, it's best done on a dyno so you can try different setups and see how much is 'too much' Link to comment Share on other sites More sharing options...
Wez Posted October 15, 2007 Author Share Posted October 15, 2007 To be fair I am really happy with the car, I am just curious as like I said the power doesnt drop off at all near the top. Would this be a worth while exercise? Link to comment Share on other sites More sharing options...
JohnA Posted October 15, 2007 Share Posted October 15, 2007 Probably, you don't have to dismantle a lot to dial the cams a bit, do you? Otherwise you'll never know if you are near the optimal cam settings - to minimise effort I'd dial them a bit more than necessary, and if it feels funny then dial back half way. Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 15, 2007 Share Posted October 15, 2007 http://www.carcraft.com/techarticles/horsepower_vs_torque/index.html http://www.billzilla.org/engvariable.html be aware these are both articles on N/A engines, but turbo cam timing will be fairly similar. Link to comment Share on other sites More sharing options...
JohnA Posted October 15, 2007 Share Posted October 15, 2007 I've found turbo timing to be quite more involved compared to n/a. Certainly less predictable. Supercharged engines, yes, they are almost like n/a. Turbochargers though create abnormally high exh pressures at high loads, and they don't exactly increase linearly. Also the turbocharger acts as a loose coupling between intake and exhaust, so whenever you change the timing on one it also affects the timing of the other one (but to a lesser extent) Dialling the cams to differing degrees also changes overlap and this affects boost leaking straight to the exhaust (in generously sized exh housings) or more often reversion (in tight exh housings, like stock setups) Sometimes you may find the best results in dialling the cams in the opposite direction (say retard inlet by 10deg and advance exh by 5 deg). This particular exh intervention would fill some of the midrange hole created by the inlet setup (which you'd want to keep because of the frenetic topend) Or it could be the other way round, hence the need for a dyno, since the 'seat of pants' dyno is often pants. Link to comment Share on other sites More sharing options...
Wez Posted October 15, 2007 Author Share Posted October 15, 2007 Think I will leave it alone then Link to comment Share on other sites More sharing options...
JohnA Posted October 15, 2007 Share Posted October 15, 2007 NOOOOOOOOO just advance the damn thing a bit! Link to comment Share on other sites More sharing options...
Wez Posted October 15, 2007 Author Share Posted October 15, 2007 Should it be advanced till the point where I see the power start to drop at the very top? Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted October 15, 2007 Share Posted October 15, 2007 I got hold of a single old HKS adjustable pulley a little while ago, (dead cheap) for an experiment i fitted it to my exhaust cam and advanced it by about six degrees, in the hope it would help spool up and help mid range torque, well all i can say is, on the last SRR session i had to abort my run due to det and mapping problem, but at just under 5,000 RPM it made 370BHP but 390 ftlb of torque, so maybe it worked. Link to comment Share on other sites More sharing options...
JohnA Posted October 15, 2007 Share Posted October 15, 2007 Should it be advanced till the point where I see the power start to drop at the very top? A bit less than that, but that's why the RR graphs are useful. The whole power curve changes, so from a point onwards you may find the trade-offs unacceptable. (say if you gain 5bhp on top and lose 10bhp down south) Also be careful with the seat of pants gotcha: If you lose midrange and topend stays the same, the car will feel *more* powerful because of the perceived increase after midrange. Times will be worse, but the feeling of urgency will mask the pure losses. A dyno graph would show this, however;) Link to comment Share on other sites More sharing options...
Wez Posted October 24, 2007 Author Share Posted October 24, 2007 Bringing this thread back to life as I am going to lower my rev limit a bit. http://www.mkivsupra.net/vbb/showthread.php?t=128695 My power curve was still on the up at 7500 so once its reduced to around 7000 I think I should look at pulling the curve over a bit. How easy is it to play with timing with the car on the dyno? Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 24, 2007 Share Posted October 24, 2007 Engine dyno, dead easy, chassis dyno, more difficult unless you KNOW how far you can move the cams and still retain excellent piston / valve clearance. What you need now is for me to build you a decent bottom end... Link to comment Share on other sites More sharing options...
Steve Posted October 24, 2007 Share Posted October 24, 2007 Engine dyno, dead easy, chassis dyno, more difficult unless you KNOW how far you can move the cams and still retain excellent piston / valve clearance. What you need now is for me to build you a decent bottom end... And what would be the rough cost of a 'decent' bottom end Link to comment Share on other sites More sharing options...
Wez Posted October 24, 2007 Author Share Posted October 24, 2007 What you need now is for me to build you a decent bottom end... What you got in mind and what sort of rev limit would be possible then? Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 24, 2007 Share Posted October 24, 2007 Steel crank and rods, JUN pistons, balanced and checked for alignment. Should turn 8250 / 8500 reliably. Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 24, 2007 Share Posted October 24, 2007 And what would be the rough cost of a 'decent' bottom end 5K 'ish? Link to comment Share on other sites More sharing options...
Steve Posted October 24, 2007 Share Posted October 24, 2007 Steel crank and rods, JUN pistons, balanced and checked for alignment. Should turn 8250 / 8500 reliably. Sounds interesting. Link to comment Share on other sites More sharing options...
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