Support Team Shaun_E Posted January 5, 2011 Support Team Share Posted January 5, 2011 What are the latest thoughts on exhaust tube diameters and lengths for a 240-250bhp K series? Engine will be a 1.9 with ported VVC head, larger valves, 1721/1444 cams, 42mm Jenveys. I have an SLR 4-2-1 exhaust at the moment which has 1.75" primaries, 2" secondaries and a 2.25" collector. Although achieving good power and torque are the primary requirements, it must be quiet so the silencer needs to be a decent length which may compromise the primary/secondary length. Most of the big power Ks seem to use the R500 4-1 or similar - is this the best route? Yellow SL #32 - member of Drowned Rat Racing Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted January 5, 2011 Share Posted January 5, 2011 From talking to exhaust builders when I got my 4-2-1 system, I understand the 4-2-1 gives better torque mid range, while the 4:1 is better for power at high revs. Depends if you want to use it on track at Max revs, or mid range on the road I guess ? Link to comment Share on other sites More sharing options...
Jason Plato Posted January 6, 2011 Share Posted January 6, 2011 stick with what you have if I were you. The cam spec you have already makes the step in power at 5500 so violent that the rear tyres cant cope on a sprint from cold in the first 4 gears . or contact Mark Durrant who has a spec for a custom exhaust with lengths that probably suit your cams and setup but it will cost a pretty penny.... here is my Duratec R .... C7 TOP Taffia joint AO with Al Link to comment Share on other sites More sharing options...
BSA Posted January 6, 2011 Share Posted January 6, 2011 Is there a big power difference running 1444 / 1444 cams to 1721 /1444 or just difference in power delivery ? Link to comment Share on other sites More sharing options...
Support Team Shaun_E Posted January 7, 2011 Author Support Team Share Posted January 7, 2011 BSA - I don't know yet - engine has yet to be built!. I am seriously thinking about sticking to 1444 for the inlet as well as the exhaust as I can't find anyone running the 1721 inlet cam yet. It's not even listed on the Piper website unless it has an alternative designation. I have decided to stick with the SLR exhaust for now but have the specification for a possibly more optimal design should I need it. Yellow SL #32 - member of Drowned Rat Racing Link to comment Share on other sites More sharing options...
Support Team Shaun_E Posted January 7, 2011 Author Support Team Share Posted January 7, 2011 Does anyone know the specifications for the Powerspeed primaries/secondaries? Yellow SL #32 - member of Drowned Rat Racing Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted January 7, 2011 Share Posted January 7, 2011 Call them and ask them 01233 662 225 Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted January 7, 2011 Leadership Team Share Posted January 7, 2011 Shaun, your engine spec will be the same as mine (with 1444 cams) and running the same exhaust - 240+bhp is not a problem and the power delivery is really sweet. As DJ says, stick with what you have! Stu. Link to comment Share on other sites More sharing options...
BSA Posted January 7, 2011 Share Posted January 7, 2011 Shaun i am building an engine to the same spec as yours apart from i am using a set of Caterham roller barrels , Bottom end is Farndon crank 1900 block top is a VVC head with Ivey Valves and 1444 cams inlet & exhaust i have been told the Engine will Rev slightly higher with a 1721 in let cam Iam going to use a R500 4-1 non cat system with a larger BTB silencer Matt Link to comment Share on other sites More sharing options...
OliverSedlacek Posted January 7, 2011 Share Posted January 7, 2011 Shaun, surely you've got enough power We noticed a significant power loss when fitting the intake plenum on Ian's car and I was wondering if you'd seem something similar. The intake plenum cuts noise, so will probably need to be fitted for track use. Link to comment Share on other sites More sharing options...
BSA Posted January 7, 2011 Share Posted January 7, 2011 Talked to Piper today 1721 inlet 288 duration/ 12.32mm lift 1444 inlet 276 duration /12.22mm lift the 1721 offers higher revs the 1444 more torque Link to comment Share on other sites More sharing options...
Support Team Shaun_E Posted January 7, 2011 Author Support Team Share Posted January 7, 2011 Some good info there - thanks. Oliver - one can never have enough power - I'm up against R500s and 2.3 Duratecs. I already have an airbox and will keep that - have not run without it so don't know if I would get more power. Noise is a major issue these days! I will go for the 1444 inlet and re-use my SLR exhaust. The 1721 inlet doesn't seem to fit my requirements as my new rev limit will be 8500rpm so I really need peak power to be below 8500rpm. BSA - everyone I have talked to says the 4-1 will give you a dip in the midle of the torque curve. I can't comment as I have always had the SLR pipes on my (226bhp) engine. Yellow SL #32 - member of Drowned Rat Racing Link to comment Share on other sites More sharing options...
Jason Plato Posted January 7, 2011 Share Posted January 7, 2011 226 moving to 245bhp wont make you any faster especially if your not reving the engine any further than present ☹️, in fact on the short hill and sprint courses it will probably be slower with less low down torque 260bhp +of full fat power at 8700rpm with 200ftlb of talks is what you need here is my Duratec R .... C7 TOP Taffia joint AO with Al Edited by - Dave Jackson on 7 Jan 2011 16:46:52 Link to comment Share on other sites More sharing options...
Support Team Shaun_E Posted January 7, 2011 Author Support Team Share Posted January 7, 2011 Currently only revving to 8000 which is partly what prompted the rebuild (that and I've done 20000+ miles and 5 seasons on this engine). 8500, maybe 8600, will give me a few more mph and put me back in the thick of the power band on upchange. It won't make me much faster but at the bigger circuits (Goodwood, Castle Combe, Anglesey) it might give me a few tenths. It's been pretty close this year in class 5 and every tenth counts! Yellow SL #32 - member of Drowned Rat Racing Link to comment Share on other sites More sharing options...
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