bubblegoose Posted January 13, 2011 Share Posted January 13, 2011 you babes may or may not know im supercharging a 4g63, it has kelfords 272 off the shelf grinds in it made for evo/vr4 turban gayness i called kelford for some advise on redialling to suit a supercharger, just looking for basic guidance as to where to start and tweak as i go/a point in the right direction. All i got told was i need some custom cams grinding for $49567893457 each i dont want to take this advise and would like to know if any of you boes have any hints PS, im miles away from driving but i have no money and the initial dial in cost nothing Quote Link to comment Share on other sites More sharing options...
keltik Posted January 13, 2011 Share Posted January 13, 2011 Run it as is. I'd imagine the main difference between turbo cams and s/c cams would be chiefly in the overlap stage. Since your going to have less exhaust back-pressure with a s/c - might be losing a wee bit of power but shouldnt cause harm. Could just get a set of adjustable cam gears to try and compensate. Quote Link to comment Share on other sites More sharing options...
kpr Posted January 13, 2011 Share Posted January 13, 2011 as above might be best to dial them in as per kelfords. then adjust later to see how engine responds but for a possible better starting point. you could retard the exhaust cam and advance the inlet to give you some overlap. which the turbo cams lack, due to exhaust pressure being higher than the inlet. should give it more midrange and make it idle more shit. Quote Link to comment Share on other sites More sharing options...
bubblegoose Posted January 14, 2011 Author Share Posted January 14, 2011 i was thinking the in cam come be advanced a bit but just wanted confirmation on that i have adjustable cam gears already Quote Link to comment Share on other sites More sharing options...
kpr Posted January 14, 2011 Share Posted January 14, 2011 might benefit from closing the exhaust later also. since its shutting at tdc, if im looking at the right cams. Quote Link to comment Share on other sites More sharing options...
bubblegoose Posted January 14, 2011 Author Share Posted January 14, 2011 they do indeed Quote Link to comment Share on other sites More sharing options...
Testament Posted January 16, 2011 Share Posted January 16, 2011 you can run quite a bit of overlap with superchargers apparently - because inlet pressure is higher than exhaust you dont get much reversion at all and get rid of the spent exhaust gasses better which is good for power. also the supercharger stops any spit back etc. so "tames" the cams somewhat. But you waste quite a bit of fuel as the inlet charge goes out the exhaust port more so no factory supercharged cars do this. but as you say hard evidence is thin on the ground and the v8 boys aren't generally much help as they buy cams off the shelf and the lobe seperation is fixed. Any idea what the inlet/exhaust flow ratio is like on the mitsi head? its a reasonable starting point to figure which cam needs to be bigger or more duration. Quote Link to comment Share on other sites More sharing options...
eke_zetec_RWD Posted January 16, 2011 Share Posted January 16, 2011 if your set on using tha cams you have then smash em in and fuck with the timing on the dyno- instant results Quote Link to comment Share on other sites More sharing options...
Testament Posted January 16, 2011 Share Posted January 16, 2011 if your set on using tha cams you have then smash em in and fuck with the timing on the dyno- instant results just make measurements during engine building as to how many degrees either way is safe to keep valves/pistons with happy clearances Quote Link to comment Share on other sites More sharing options...
RUNAMUCK Posted January 16, 2011 Share Posted January 16, 2011 Also with a positive displacement blowers, any unburnt fuel that gets blown out the exhaust valve from overlap can actually help to cool the zhorst valves. Quote Link to comment Share on other sites More sharing options...
kpr Posted January 16, 2011 Share Posted January 16, 2011 hmm yeh was running 310 deg na cams with heaps of overlap + sc14 on my 4ag. 14.0na vs 13.1 1/4 mile on 4psi, so does work Quote Link to comment Share on other sites More sharing options...
bubblegoose Posted January 16, 2011 Author Share Posted January 16, 2011 think there would be much difference in lobe profile between a turbo cam and sc cam? much between turbo and na? Quote Link to comment Share on other sites More sharing options...
mjrstar Posted January 16, 2011 Share Posted January 16, 2011 ^^ not too sure on the 4g63 but the 1gge has 10% more lift than the 1ggte it has been proven that the N/A cams make around 30 more HP at high boost. Quote Link to comment Share on other sites More sharing options...
bubblegoose Posted January 16, 2011 Author Share Posted January 16, 2011 i was more referring to the shape of the lobe rather than just lift and duration ie difference between 11mm 290 na cam vs 11mm 290 turbo cam other than the timing Quote Link to comment Share on other sites More sharing options...
RUNAMUCK Posted January 17, 2011 Share Posted January 17, 2011 I can't say either way, but I do know that you'll be able to tweak your LSA being as to how your motor is twin cam. This will denote your overlap, which is the critical thing I supose. As may have been said above, (or not) a supercharged motor can stand much more overlap than a turbo engine. Although I think with an angry turbo (and definately with a nitrous) cam, the LSA is a bit wider, and the exhuast event begins a bit sooner. (before BDC) This (with nitrous anyway) helps to utilise some of the thermal expansion to aid the evacuation of the spent charge. (since it's being added artificially on the intake side) This does cost some power, (The wider the LSA, the more power it costs) but where the power is being added it's a trade-off. I would assume that an earlier (BBDC) exhuast event would also bode well for a turbo engine, as it's going to help get the turbo spooling faster. Since more of the spent gasses are still expanding. Also on single cam engines, wider LSA's are ussually accompanied by smaller overlap durations/lift, so you don't have exhuast gas back feeding out the intake corrupting the vaccuum signal, and impeading the compressor wheel while the other gasses are trying to spool the other side of the turbo. I suppose ssuperchargers are more flexible in what cams they can run with. (Think about the millercycle engines) I did once run a can with 106* lsa on my datto with ther blower. It went like fuck too. (For a wee while) Dunno if what ive written is relevant/makes sence. (It's probably a load of horseshit anyway) Quote Link to comment Share on other sites More sharing options...
Testament Posted January 17, 2011 Share Posted January 17, 2011 i was more referring to the shape of the lobe rather than just lift and duration ie difference between 11mm 290 na cam vs 11mm 290 turbo cam other than the timing depends on what the application is. generally turbo cams will be a little milder to try and improve driveability/low mid end as you have boost to make up for having slightly less volume flow. but when you get to the very extremes it's not really different apart from the timing, the faster/higher (up to a point) you can open the valves the more air you can force in - if you can force in more air you can burn more fuel and make more power. back to your original question - the kelford 272's should work fine but will probably perfer different timing. custom profile etc. to your spec will be better obviously, how much better is hard to say. I need to get my shite sorted for my motor too as it will be somewhat similar. also a decent example although not that similar (sbc with centrifugal setup) http://www.superchevy.com/technical/eng ... index.html but basically bigger cam = bigger power. Quote Link to comment Share on other sites More sharing options...
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