dave barratt Posted December 19, 2005 Share Posted December 19, 2005 I've bought a set of UK spec Cam shafts I was thinking of fitting to my J_Spec TT. My question is is it worth fitting the exhaust cam. I read that there the same? Also should I sell the pair and just buy a Performance Inlet cam? Cam specs: Jap intake lift: 7.8 mm ... UK 8.25 mm. Jap exhaust lift: 8.4 mm ... UK 8.4 mm. Valve timing: Jap intake opening: 3 degs BTDC - closing 41 degs ABDC ... UK 3 degs BTDC - 50 degs ABDC. Jap exhaust opening: 52 degs BBDC - closing 4 degs ATDC ... UK same as Jap spec. Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 19, 2005 Share Posted December 19, 2005 What turbo(s)? The exhaust back pressure will have a big say in cam choice. What ecu, (in other words how much control o the maps have you)? Link to comment Share on other sites More sharing options...
dave barratt Posted December 19, 2005 Author Share Posted December 19, 2005 Hi Chris, Just the standard J-spec turbo's and ECU. Got your full decat exhaust with restrictor ring fitted Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 19, 2005 Share Posted December 19, 2005 Rhe stock turbos have tiny exhaust sides, giving a LOT of back pressure in the pursuit of low RPM torque via boost. If you go too wild on cam duration you get exhaust gas reversion. The stock cams are great, the most you'd want to run are around 264 degrees duration on the exhaust cams, and MAYBE 272 on the intake, these figures based on off the shelf performance cams. Even these tame figures will give lag and some increases in emissions. Change to a single turbo or larger (parallel) twins, however, and you cn utilize much more duration. ANY cam change should really be paired with a re programmable ecu, but 264's in inlet and exhaust positions aren't too bad with the stock J-Spec ecu. HTH. Link to comment Share on other sites More sharing options...
JohnA Posted December 19, 2005 Share Posted December 19, 2005 Chris, do you know if the "264" etc figures of aftermarket cams are comparable to the stock ones? (i.e. are they all meant to be measured at the same valve lift?) Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 19, 2005 Share Posted December 19, 2005 A very good question, wothout knowing at what lift et cetera it's very hard to compare profiles off makers spec sheets. Usually an aftermarket cam is measured from and to a certain lift figure, otherwise ramp profiles make large numeric duraton differences with little effect on flow. Short answer, I don't know. Link to comment Share on other sites More sharing options...
JohnA Posted December 19, 2005 Share Posted December 19, 2005 I was reading at a supra-friendly US site on the subject, and the guy's opinion was that they are not comparable. I think he had them measured and they were way off (but consistently, a sign of different valve lift used as a 'threshold') So apart from machining differences, ramp profiles etc we also have the question mark over degree comparisons. Link to comment Share on other sites More sharing options...
dave barratt Posted December 20, 2005 Author Share Posted December 20, 2005 Chris , thanks for all the advice, is it worth fitting the uk spec cams ? Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 20, 2005 Share Posted December 20, 2005 I'd save for a pair of 264's or thereabouts, from HKS or JUN. Not worth the labour costs fitting and shimming for such a small change, IMO. Link to comment Share on other sites More sharing options...
dangerous brain Posted December 20, 2005 Share Posted December 20, 2005 So if you've got adjustable pulley wheels and an safc2 on a car with hks 264 inlet and exhaust cams then is it worth having the SAFC2 mapped or the vernier pulleys setup or not? Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 20, 2005 Share Posted December 20, 2005 Cmas should always be dialled in via vernier pulleys, in an ideal world, an SAFC won't be able to modify the ignition map, will it? The ignition will need changing as much as, probably more so, than the fuelling with cam changes. Link to comment Share on other sites More sharing options...
dangerous brain Posted December 20, 2005 Share Posted December 20, 2005 So the combination of the vernier pulleys and the safc should make the car run better than it does now? Its not running badly but if its worth tuning a bit its worth knowing? Link to comment Share on other sites More sharing options...
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