Member Contributer Mohawk Posted September 5, 2014 Author Member Contributer Share Posted September 5, 2014 All sounds correct to me, which then begs a question as to where did Honda get their numbers from ? I'll try to measure one of my head volumes at lunch time. Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted September 5, 2014 Author Member Contributer Share Posted September 5, 2014 OK, not quite got the right kit & can't find my buret, so working with what I have I put a small piece of tape over the spark plug hole & used my digital scales to weigh a measured amount of lubricated water into the leveled front head. I got 15.2 & 14.2cc the first was probably due to some leakage via a valve as some drips came out the bottom on that side. So your more carefully measured 14.4cc seems spot on, as I would have lost a tiny amount for tape & the plug head has an air volume around it, which you are also missing ! But I just went & measured one of those using same process, a whopping 0.1cc per plug ! Link to comment Share on other sites More sharing options...
Member Contributer Rush2112 Posted September 5, 2014 Member Contributer Share Posted September 5, 2014 Would you need to account for the portion of the piston that extends past the plane of the block by subtracting from sweep volume for CR calc? Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted September 5, 2014 Author Member Contributer Share Posted September 5, 2014 He already did Link to comment Share on other sites More sharing options...
Member Contributer HighSideNZ Posted September 5, 2014 Member Contributer Share Posted September 5, 2014 Thanks Mohawk. Yes, I'd say the 14.0/14.4 volume is what they came with as far as production tolerance goes. I've worked my CR out on the 14.4 volume, so if you got a motor with 14.0cc chambers all round, or a mix like mine were that would give a static CR of 13.2:1 and a dynamic of 12.36:1 (35 deg ABDC) I just can't get the advertised 11.6 to work out any where. Not to worry, bigger fish to fry than to ponder Honda's thinking. Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted September 5, 2014 Author Member Contributer Share Posted September 5, 2014 So running the numbers shows Honda's declared 11.6-1 is 14.6-1 so plus 3. Applying the same offset to the 74mm bore comes out at 15.3-1, so minus 3 = 12.3-1 verses the 12.25-1 originally calculated, so I reckon its fine as we know a 14-1 ratio would NOT run on regular unleaded ! Strangely if you add in 1mm of piston to head clearance that gives an additional 4cc that we are missing ! Have you checked the piston deck clearance ? Link to comment Share on other sites More sharing options...
Member Contributer HighSideNZ Posted September 5, 2014 Member Contributer Share Posted September 5, 2014 Yep. When I machined the piston crowns I measured the standard pistons from the gudgeon pin to crown and made the 929 ones exactly the same. So, the squish area sits flush with the top of the block and the centre "dome" is 1mm above. All exactly as per the standard vfr pistons. So not sure as to where the difference comes in but we will find out when she is a runner I expect. Link to comment Share on other sites More sharing options...
Member Contributer Switchblade Posted September 6, 2014 Member Contributer Share Posted September 6, 2014 I hope your planning on offering some kind of engine swapping program. You know send me a running 108hp motor and I will replace it with a 150hp motor for a small fee . Link to comment Share on other sites More sharing options...
CandyRedRC46 Posted September 6, 2014 Share Posted September 6, 2014 Why don't you guys look into doing compression tests (in psi). Look at what the stock max service limit is. Find out what the maximum streetable limit for pump gas is generally accepted around. Then assemble the engine and test it out. See if it's with in reason. If it's too high run some cams with more duration or retard the intake cam and or advance the exhaust cam a few degrees. Test the compression again, that should help and boost the top end. Ps I do realize you guys are trying to sort out the compression before assembly, but once piston to valve clearances are checked out to be okay, this might be a better way to go about things.... Link to comment Share on other sites More sharing options...
Member Contributer HighSideNZ Posted September 7, 2014 Member Contributer Share Posted September 7, 2014 Compression tests are all OK except that they are reliant upon a known cranking speed. Change the speed and you get a different result. All that I'm trying to do is get my head around what Honda advertised and what I've measured. Worst luck the motor I an working on was in no state to be cranked over before I started the project, so I'll just have to go with what I'm doing. Altering the cam timing on a Gen5 motor is no small feat. The cam gears are a press fit on to the cams so there is no way to make them easily adjustable like with what I did on my Gen6 and slotted the bolt holes. You have to assemble, measure, deassemble, press of the gear, move it and press it back on. Not sure how many time you can do this without loosing the press fit interference. Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted September 7, 2014 Author Member Contributer Share Posted September 7, 2014 Yeah I sometimes think this whole exercise would be easier on a Vtec engine. Adding extra head space a doddle. You could always remove some more material from the inter valve ridges to reduce CR if you think it's too much. I did some thinking & if you lose the anti-lash gears, then you could seperate two gear wheels & make an adjustable cam for degreeing, but like everything else on a V motor twice the count & twice the cost in both time & money. Link to comment Share on other sites More sharing options...
Member Contributer HighSideNZ Posted September 7, 2014 Member Contributer Share Posted September 7, 2014 Hey, I've been thinking as well. I wonder if there was some trapped air in the chamber when I did the assembled measurement the other day. It was such a pain to do, I only did one so don't have repeat-ability. What I'm going to do is this: 1. Seal the piston/bore interface with grease. 2. Dial gauge TDC and then drop the piston exactly 2mm in the bore. 3. Use my glass plate on the bore and fill the void from the burette. A full 2mm in a 74mm bore is 8.6cc. So then with the chamber volume of 14.4cc, gasket volume of 3.44cc = 17.84 Whatever the difference is in the measured volume in the bore from 8.66 is the volume I need to subtract from 17.84 to get the actual working chamber volume. I'll let you know once I've done the measurement, repeated times, and if it shows up anything different from my earlier post. Link to comment Share on other sites More sharing options...
Member Contributer vfrcapn Posted September 7, 2014 Member Contributer Share Posted September 7, 2014 You guys are insane. And I'm loving this. Carry on. Link to comment Share on other sites More sharing options...
Member Contributer HighSideNZ Posted September 7, 2014 Member Contributer Share Posted September 7, 2014 I'm glad we keep you entertained. LOL Cheers Phil Link to comment Share on other sites More sharing options...
CandyRedRC46 Posted September 7, 2014 Share Posted September 7, 2014 A good way to reduce compression/cylinder pressures would be radiusing the valve reliefs in the pistons and polishing everything. This would be a twofold mod, as you would reduce the cylinder pressures and reduce the hot spots. Both would aid in preventing detonation. Link to comment Share on other sites More sharing options...
Member Contributer HighSideNZ Posted September 7, 2014 Member Contributer Share Posted September 7, 2014 I've already removed all the possible hot spots on the piston crowns and in the chambers. The difference in volume is minuscule so good luck with trying this to reduce overall CR. When I did mine the other day, radiusing all of the valve pockets amounted to about 0.1cc per piston. Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted September 7, 2014 Author Member Contributer Share Posted September 7, 2014 Sounds like a plan. But one issue is that 17.84cc is not enough to have equalled the original claimed CR ! Nevermind the new one ! Link to comment Share on other sites More sharing options...
Member Contributer gll429 Posted September 7, 2014 Member Contributer Share Posted September 7, 2014 you guys are really OVER worrying about the head and combustion chamber IMO.. i have seen a Vmax punched out to 2000 ccs with very little head work and sucker runs on 87 oct. ditto for for god know how many harleys and busas and gs"s not to mention the big bore kits for every freaking ninja out there.. but do have fun!! Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted September 7, 2014 Author Member Contributer Share Posted September 7, 2014 Just found this reading the 2002 VFR press pack. If the gaskets fit, you too can have RC45 compression on your 5th gen ! Anyone got a set of 5th gen & 6th gen head gaskets to overlay & measure the thickness ? >>> The combustion chambers’ new ultra-compact, high-compression design also features a 30% thinner head gasket that helps minimise the ‘quenching area’ that normally exists in the corner gap between the head and cylinder block, improving the igniting flame’s reach into the far recesses of the combustion chamber and realising a significant increase in cleaner-burning combustion efficiency. <<< Link to comment Share on other sites More sharing options...
Member Contributer Rush2112 Posted September 7, 2014 Member Contributer Share Posted September 7, 2014 Wouldn't using a thinner head gasket effect the gear spacing on the cam drives? Would 30% thinner allow enough clearance between the drive gear and cam gears? Link to comment Share on other sites More sharing options...
CandyRedRC46 Posted September 7, 2014 Share Posted September 7, 2014 Yeah I sometimes think this whole exercise would be easier on a Vtec engine. Adding extra head space a doddle. You could always remove some more material from the inter valve ridges to reduce CR if you think it's too much. I did some thinking & if you lose the anti-lash gears, then you could seperate two gear wheels & make an adjustable cam for degreeing, but like everything else on a V motor twice the count & twice the cost in both time & money. That'd be one of the first things I'd do if I had a fifth gen. Remove those anti lash gears. Free power :) Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted September 7, 2014 Author Member Contributer Share Posted September 7, 2014 Wouldn't using a thinner head gasket effect the gear spacing on the cam drives? Would 30% thinner allow enough clearance between the drive gear and cam gears? Yes it would, but they can be adjusted if you know how ! :) I was thinking of having Cometic make some if I don't do the big bore. I've already calculated for 0.25mm thiner as possible. Just need to find out if the 6th Gen HG will fit & then how thick is it ? Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted September 7, 2014 Author Member Contributer Share Posted September 7, 2014 Just been wasting my Sunday afternoon cleaning the TBR system & checking the headers fit to one of my spare heads. So remeasured the headers extra carefully & the minimum difference between no1 & no3 cylinder is 6.5". Also the front head has 32mm exhaust ports where the exhaust mounts, so with the TBR inner diameter at the head connector flange being 37mm there is a 5mm or 2.5mm step around the port to the exhaust. Need to have a little thought about what to do with that. I might seal the ports & grind a cone into the head port. The next issue is the standard copper seals are engineered to suit the standard exhaust flange which is 4-5mm, but the TBR has a 2mm flange. So if I taper the exhaust ports then I need to find a new gasket. Link to comment Share on other sites More sharing options...
Member Contributer HighSideNZ Posted September 7, 2014 Member Contributer Share Posted September 7, 2014 I would not enlarge the port in the head. As far as I know, the HRC RC45 ports are pretty much stock. There is an issue with reversion in the gas flow that needs to be taken in to account. It is the same on the inlet side, where the throttle bodies do not flow evenly in to the ports. If the steps are removed, you end up loosing low/mid range, so be careful with what you do. I myself, would leave the step as is. Link to comment Share on other sites More sharing options...
Member Contributer HighSideNZ Posted September 8, 2014 Member Contributer Share Posted September 8, 2014 Hi GLL429 Yep you are probably right. There are lots of bikes out there with massively overbored blocks without issue. It's just that In cannot make the standard advertised Honda figures add up and this has me really perplexed. Phil Link to comment Share on other sites More sharing options...
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