<div dir="ltr">Getting down to the less than tenths of a C.C. is fine for really accurate compression ratios, but in the end you are measuring a ratio of VOLUMES not pressures so the thing to put in your mind is the effect on the percentage of volumetric efficiency. <div><br></div><div>Now for that you have to take a fine pointed thing, aim it at the engine and ask " How good are you?" Then start at the top of the heap of volumetric possibilities. Turbo and/or supercharger 100% plus, overhead cam, 4 valves, fuel injection around 95%, most triumph engines about 89-91% at best. Now that 13 to 1 volume ratio does not look so impressive, but does put a nice crackle in the exhaust note and seems to help a bunch down the long straights.</div><div>As in so many things like this I am just guessing along with everyone else. <div><br></div><div><br></div></div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><p><strong><font color="#000099">Never be beaten by equipment.</font></strong></p></div></div>
<br><div class="gmail_quote">On Fri, Sep 23, 2016 at 10:33 PM, Bill <span dir="ltr"><<a href="mailto:ponobill@gmail.com" target="_blank">ponobill@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">Yeah, but that’s just step one--after you measure the volume of the combustion chamber you still need to know all the stuff Steve Yott mentions. At least you do if you want to know the actual compression ratio. <div> <br><div><blockquote type="cite"><div>On Sep 23, 2016, at 9:19 PM, Steven Belfer <<a href="mailto:steve@artwithcars.com" target="_blank">steve@artwithcars.com</a>> wrote:</div><br><div><span style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">Get Kas' book. There's a helpful section describing how to CC the head using a plate of plexiglass and measuring how much fluid you can fill it with.<span> </span></span><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><span style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">~Steve</span><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><blockquote type="cite" style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">On Sep 23, 2016, at 8:14 PM, Steve Yott <<a href="mailto:tr4@wi.rr.com" target="_blank">tr4@wi.rr.com</a>> wrote:<br><br>Steve,<br>In order to calculate the combustion chamber volume desired you need also know the bore, stroke, head gasket diameter and thickness, piston to liner clearance, depth of the top ring and deck clearance of the piston (or pop up if you are running any). These all make up the total volume which you need to calculate the chamber volume you need for the static compression ratio you desire. Also when doing a chamber volume test don't forget that the valve head thickness will affect this measurement.<br><br>There are a good number of web sites out there that will do all these calculations for you and give you a required chamber volume for the desired compression ratio. There are various head castings out there so I would not take the thickness into account except for a rough idea.<br><br>This all creates a "static" compression ratio and will not mean much when the dynamics of the cam and valve overlap come into play and create the "dynamic" compression ratio.... wish there were a good method of calculating that!<br><br>Steve Yott<br><br><br><br>-----Original Message-----<br>From: Fot [<a href="mailto:fot-bounces@autox.team.net" target="_blank">mailto:fot-bounces@autox.<wbr>team.net</a>] On Behalf Of Stephen Borowski<br>Sent: Friday, September 23, 2016 6:45 PM<br>To: FOT Triumph <<a href="mailto:fot@autox.team.net" target="_blank">fot@autox.team.net</a>><br>Subject: [Fot] TR4 Compression Ratio Calculation Question<br><br>Hello All,<br>Does any one know the "chamber volumes" vs "compression ratio” for the TR4 high port head. What should the head thickness measure?<br><br>All comments welcome!<br><br>Thxs. 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