Steve P Posted September 1, 2015 Report Share Posted September 1, 2015 Evening all, Is a 13:1 compression ratio head practical for a road car? Thanks Steve Quote Link to post Share on other sites
Guest ntc Posted September 1, 2015 Report Share Posted September 1, 2015 No sorry Quote Link to post Share on other sites
Steve P Posted September 1, 2015 Author Report Share Posted September 1, 2015 Thanks Quote Link to post Share on other sites
snowric Posted September 1, 2015 Report Share Posted September 1, 2015 But if you really need to use it then a copper head cylinder gasket to lower it. Headgasket.com in USA can custom build them. Suspect you need at least a couple of mm. Never used one myself only read about them Snowy Quote Link to post Share on other sites
john.r.davies Posted September 1, 2015 Report Share Posted September 1, 2015 (edited) Yes, of course it's possible - anything is possible if you throw enough ingenuity, and money, at it. In this case 110 octane fuel minimum, plus water injection cooling into the chambers, forged pistons and best of all, Alcohol fuel. That would run like a kitten purring - a tiger kitten. The engine before last that I built had a static CR of 10.8 - and it pinked out of the box, until I refilled the tank with new fuel. John Edited September 2, 2015 by john.r.davies Quote Link to post Share on other sites
Nick Jones Posted September 1, 2015 Report Share Posted September 1, 2015 With an aggressive enough cam (which will reduce the dynamic compression ratio), you might get away with it. Whether you could actually put up with the manners of such a cam on the road is another question. Possibly could be tamed to an extent with modern engine management, but on the whole I'm forced to agree with Neil....... Might be some use on a 2L engine - or is that where it came from? Nick Quote Link to post Share on other sites
Peter Cobbold Posted September 2, 2015 Report Share Posted September 2, 2015 (edited) Yes, with a few tricks, to do with spark and fuelling, it could be made to work. I have to cope with boosts that give that effective compression and run on 95RON. Back to your 13:1 normally aspiarted road engine: Away from full throttle it will run fine on pump fuel of say 97RON. Towards mid- to full-throttle it will knock on 97RON once cylinder filling brings above 10.5:1 eff comp. You then have several options, triggered at that point. Alone or in combination. 1. Richen the mixture to around AFR 9:1 https://supertrarged.wordpress.com/2015/08/30/tr6se33-running-on-95ron-octane/ - that will give you very roughly 1.5 ratios above 10.5:1 ( fig 3 in pdf), so that could make it safe at eff CR12:1. 2. Retard the spark. slide 50: https://supertrarged.wordpress.com/2015/08/10/iwe-tech-seminar-supercharging-trs-for-the-road/ ' retard 3 crank deg for each compression ratio rise' Programmable 123 disy could be useful. 3 Fit water injection https://supertrarged.wordpress.com/2014/11/10/tr6se-28-water-injection/ but getting water to distribute well between all 6 cylinders is awkward: https://supertrarged.wordpress.com/2014/11/22/tr6se-29-distribution-of-injected-water/ So a 13:1 head is not going to work without a lot of test and experiment. Easiest is spark retard, but that could lead to bad overheating if run for longer than short bursts. Peter Whether its worth the hassle is another question. The power gain going from comprat 9.5 to 13 is around 8% http://www.hotrod.com/events/coverage/0311em-power-squeeze/ But that table assumes the gain is not knock-limited. All the cures for knock suggested above will reduce that gain below 8%. The only way to keep all the gain is to run road-illegal high octane fuel. Edited September 2, 2015 by Peter Cobbold Quote Link to post Share on other sites
Guest ntc Posted September 2, 2015 Report Share Posted September 2, 2015 With an aggressive enough cam (which will reduce the dynamic compression ratio), you might get away with it. Whether you could actually put up with the manners of such a cam on the road is another question. Possibly could be tamed to an extent with modern engine management, but on the whole I'm forced to agree with Neil....... Might be some use on a 2L engine - or is that where it came from? Nick Nick Correct a 2L is possible but anything over it is skip fodder. Quote Link to post Share on other sites
DaveN Posted September 2, 2015 Report Share Posted September 2, 2015 That must be the stage 3 head currently on the bay at the mo! Quote Link to post Share on other sites
Alec Pringle Posted September 2, 2015 Report Share Posted September 2, 2015 This one ? http://www.ebay.co.uk/itm/Triumph-Tr5-Tr6-Cylinder-Head-/252074637235?hash=item3ab0d1b7b3 13:1 cr sounds a little improbable to me, 10.3:1 may perhaps have been what was intended ? Cheers Alec Quote Link to post Share on other sites
Guest ntc Posted September 2, 2015 Report Share Posted September 2, 2015 Where's Tom Boyd he should know? Quote Link to post Share on other sites
Tom Boyd Posted September 2, 2015 Report Share Posted September 2, 2015 What would you like to know Neil?? I feel honoured you want to involve me in all this ???????????????????????????????? Quote Link to post Share on other sites
Guest ntc Posted September 2, 2015 Report Share Posted September 2, 2015 What would you like to know Neil?? I feel honoured you want to involve me in all this Your way around it Tom and your welcome Quote Link to post Share on other sites
Tom Boyd Posted September 2, 2015 Report Share Posted September 2, 2015 Bit on the high side for a road car for sure....... ???????????? Quote Link to post Share on other sites
Guest ntc Posted September 2, 2015 Report Share Posted September 2, 2015 Bit on the high side for a road car for sure....... Can be done Tom you end up with a shi!!! load of torque but the cost is not worth it for road use. Quote Link to post Share on other sites
Tom Boyd Posted September 2, 2015 Report Share Posted September 2, 2015 Been there and done it...... Tom Quote Link to post Share on other sites
WWT338J Posted September 2, 2015 Report Share Posted September 2, 2015 I made a bad decision a decade or so ago to buy a reconditioned engine from Rimmers. The engine pinked like crazy unless I retarded the ignition pretty much to TDC. Retarding the cam timing helped a bit but the engine still ran v hot. In the end I used a solid shim copper gasket from Gasketworks US to reduce the CR down to about 10. The engine ran fine and made good torque. The only problem was an irritating oil leak from the spark plug side of the gasket which required liberal coatings of gasket sealant. A little while ago a UK firm was advertising Cometic shim gaskets in varying thicknesses for the TR6 on ebay. I think these would be easier to install than solid copper. David Quote Link to post Share on other sites
Nick Jones Posted September 2, 2015 Report Share Posted September 2, 2015 Looking at the ebay pics, the amount of material removed from the chamber seems to be quite large, which does lead me to wonder if it really is 13:1. Certainly would have taken a big skim. Nick Quote Link to post Share on other sites
Alec Pringle Posted September 2, 2015 Report Share Posted September 2, 2015 Indeed Nick, it does look well skimmed, but even so . . . . . hence my comment about 10.3, rather than 13, having looked carefully at the photos ! Apart from anything else, 13:1 is simply not going to run on anything resembling pump fuel. Cheers Alec Quote Link to post Share on other sites
Peter Cobbold Posted September 2, 2015 Report Share Posted September 2, 2015 (edited) Fitting a decompression gasket kills squish and that promotes knock, so the compression has to be lowered more. And it would probably need lowering below 10.5:1 since that is near the knock limit of head with squish, on 97RON. 99RON might help a little. But a 10.5:1 head with its decent squish seems to me to be the better bolt-on answer. But it would be fun trying to get 13:1 to run on the road reliably. I dont think its impossible, except with the Lucas PI. Peter Edited September 2, 2015 by Peter Cobbold Quote Link to post Share on other sites
Steve P Posted September 3, 2015 Author Report Share Posted September 3, 2015 Morning Guys, I spoke with the owner of the head yesterday. He confirmed that it is indeed 13:1 cr. He said the previous owner was building a race car and installed the head to a standard engine but then never finished upgrading the rest of the engine. The guy said he used it on the road for a while (and it was fast) until eventually the performance dropped off due to damaged pistons. Steve Quote Link to post Share on other sites
Peter Cobbold Posted September 3, 2015 Report Share Posted September 3, 2015 eventually the performance dropped off due to damaged pistons. Steve Steve, That figures !! - its exactly what knock, aka detonation, will do. Peter Quote Link to post Share on other sites
Rien Posted September 3, 2015 Report Share Posted September 3, 2015 Evening all, Is a 13:1 compression ratio head practical for a road car? Thanks Steve Depents off the camshaft and fuel you are use, but I don't think so. Quote Link to post Share on other sites
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