Subject: Re: [Fot] TR4 Compression Ratio Calculation Question

From: "Steve Yott" <[email-masked]>
Date: Fri, 23 Sep 2016 22:14:26 -0500

Steve,
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.

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.

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!

Steve Yott

-----Original Message-----
From: Fot [mailto:[email-masked]] On Behalf Of Stephen Borowski
Sent: Friday, September 23, 2016 6:45 PM
To: FOT Triumph <[email-masked]>
Subject: [Fot] TR4 Compression Ratio Calculation Question

Hello All,
Does any one know the "chamber volumes" vs "compression ratio” for the TR4 high port head. What should the head thickness measure?

All comments welcome!

Thxs. Steve
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From: Steven Belfer <[email-masked]>
Date: Fri, 23 Sep 2016 21:19:46 -0700

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. 

~Steve

> On Sep 23, 2016, at 8:14 PM, Steve Yott <[email-masked]> wrote:
> 
> Steve,
> Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/[email-masked]
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From: Bill <[email-masked]>
Date: Fri, 23 Sep 2016 22:33:24 -0700

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Yeah, but that=E2=80=99s 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.=20
=20
> On Sep 23, 2016, at 9:19 PM, Steven Belfer <[email-masked]> =
wrote:
>=20
> 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.=20
>=20
> ~Steve
>=20
>=20
>> On Sep 23, 2016, at 8:14 PM, Steve Yott <[email-masked] =
>>=20
>> Steve,
>> 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.
>>=20
>> 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.
>>=20
>> 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!
>>=20
>>=20
>>=20
>>=20
>> From: Fot [mailto:[email-masked]] On Behalf Of Stephen =
Borowski
>>=20
>> Does any one know the "chamber volumes" vs "compression ratio=E2=80=9D =
for the TR4 high port head. What should the head thickness measure?
>>=20
>>=20
>>=20
>>=20
>> Unsubscribe/Manage: =
http://autox.team.net/mailman/options/fot/[email-masked]
>>=20
>>=20
>>=20
>>=20
>>=20
>> Unsubscribe/Manage: =
http://autox.team.net/mailman/options/fot/[email-masked] =
<http://autox.team.net/mailman/options/fot/[email-masked]>
>>=20
>>=20
>=20
> http://www.fot-racing.com <http://www.fot-racing.com/>
>=20
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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dutf-8"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" =
class=3D"">Yeah, but that=E2=80=99s 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.&nbsp;<div class=3D"">&nbsp;<br =
class=3D""><div><blockquote type=3D"cite" class=3D""><div class=3D"">On =
Sep 23, 2016, at 9:19 PM, Steven Belfer &lt;<a =
href=3D"mailto:[email-masked]" =
class=3D"">[email-masked]</a>&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><div class=3D""><span =
style=3D"font-family: Helvetica; font-size: 12px; font-style: normal; =
font-variant-caps: normal; font-weight: normal; letter-spacing: normal; =
orphans: auto; text-align: start; text-indent: 0px; text-transform: =
none; white-space: normal; widows: auto; word-spacing: 0px; =
-webkit-text-stroke-width: 0px; float: none; display: inline =
!important;" class=3D"">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 =
class=3D"Apple-converted-space">&nbsp;</span></span><br =
style=3D"font-family: Helvetica; font-size: 12px; font-style: normal; =
font-variant-caps: normal; font-weight: normal; letter-spacing: normal; =
orphans: auto; text-align: start; text-indent: 0px; text-transform: =
none; white-space: normal; widows: auto; word-spacing: 0px; =
-webkit-text-stroke-width: 0px;" class=3D""><br style=3D"font-family: =
Helvetica; font-size: 12px; font-style: normal; font-variant-caps: =
normal; font-weight: normal; letter-spacing: normal; orphans: auto; =
text-align: start; text-indent: 0px; text-transform: none; white-space: =
normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: =
0px;" class=3D""><span style=3D"font-family: Helvetica; font-size: 12px; =
font-style: normal; font-variant-caps: normal; font-weight: normal; =
letter-spacing: normal; orphans: auto; text-align: start; text-indent: =
0px; text-transform: none; white-space: normal; widows: auto; =
word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: =
inline !important;" class=3D"">~Steve</span><br style=3D"font-family: =
Helvetica; font-size: 12px; font-style: normal; font-variant-caps: =
normal; font-weight: normal; letter-spacing: normal; orphans: auto; =
text-align: start; text-indent: 0px; text-transform: none; white-space: =
normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: =
0px;" class=3D""><br style=3D"font-family: Helvetica; font-size: 12px; =
font-style: normal; font-variant-caps: normal; font-weight: normal; =
letter-spacing: normal; orphans: auto; text-align: start; text-indent: =
0px; text-transform: none; white-space: normal; widows: auto; =
word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=3D""><br =
style=3D"font-family: Helvetica; font-size: 12px; font-style: normal; =
font-variant-caps: normal; font-weight: normal; letter-spacing: normal; =
orphans: auto; text-align: start; text-indent: 0px; text-transform: =
none; white-space: normal; widows: auto; word-spacing: 0px; =
-webkit-text-stroke-width: 0px;" class=3D""><blockquote type=3D"cite" =
style=3D"font-family: Helvetica; font-size: 12px; font-style: normal; =
font-variant-caps: normal; font-weight: normal; letter-spacing: normal; =
orphans: auto; text-align: start; text-indent: 0px; text-transform: =
none; white-space: normal; widows: auto; word-spacing: 0px; =
-webkit-text-stroke-width: 0px;" class=3D"">On Sep 23, 2016, at 8:14 PM, =
Steve Yott &lt;<a href=3D"mailto:[email-masked]" =
class=3D"">[email-masked]</a>&gt; wrote:<br class=3D""><br =
class=3D"">Steve,<br class=3D"">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). =
&nbsp;These all make up the total volume which you need to calculate the =
chamber volume you need for the static compression ratio you desire. =
&nbsp;Also when doing a chamber volume test don't forget that the valve =
head thickness will affect this measurement.<br class=3D""><br =
class=3D"">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. &nbsp;There are various head castings =
out there so I would not take the thickness into account except for a =
rough idea.<br class=3D""><br class=3D"">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 =
class=3D""><br class=3D"">Steve Yott<br class=3D""><br class=3D""><br =
class=3D""><br class=3D"">-----Original Message-----<br class=3D"">From: =
Fot [<a href=3D"mailto:[email-masked]" =
class=3D"">mailto:[email-masked]</a>] On Behalf Of Stephen =
Borowski<br class=3D"">Sent: Friday, September 23, 2016 6:45 PM<br =
class=3D"">To: FOT Triumph &lt;<a href=3D"mailto:[email-masked]" =
class=3D"">[email-masked]</a>&gt;<br class=3D"">Subject: [Fot] TR4 =
Compression Ratio Calculation Question<br class=3D""><br class=3D"">Hello =
All,<br class=3D"">Does any one know the "chamber volumes" vs =
"compression ratio=E2=80=9D for the TR4 high port head. What should the =
head thickness measure?<br class=3D""><br class=3D"">All comments =
welcome!<br class=3D""><br class=3D"">Thxs. Steve<br =
class=3D"">_______________________________________________<br =
class=3D""><a href=3D"mailto:[email-masked]" =
class=3D"">[email-masked]</a><br class=3D""><br =
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From: John Hasty <[email-masked]>
Date: Sat, 24 Sep 2016 10:42:41 +0000

Exactly what we did on our 2stroke motorcycle racers

Sent from my iPhone

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From: Duncan Charlton <[email-masked]>
Date: Sat, 24 Sep 2016 07:21:12 -0500

Steve,

I seem to remember seeing an online calculator to figure dynamic compression ratio.  It needed stroke, rod length and the crank degree figure at the point of intake valve closing.  However I measured it the “easy” way, just measuring piston rise every 2 degrees from BDC on a partially disassembled engine (using a dial indicator) and comparing those figures to my camshaft specs (I’d checked those using a degree wheel and dial indicator before disassembly).  Once I had a figure for the amount of stroke remaining after the intake valve closed it was simple to calculate dynamic CR, which I was trying to get just under 9:1.

To get unswept volume I did a test assembly of an engine (just one cylinder needed valves and piston w/ rings for this test), put the piston at TDC and tilted it so that the plug hole was the high point, and then measured the amount of fluid needed to fill the “overhead” space.  I used water with a bit of alcohol in it which gave lower surface tension than plain water, filling the cylinder using a calibrated burette bought through Amazon.  Very light oil might be better if you don’t want to have to remove the rings, etc. afterward to remove the water but I was concerned what the oil would do to the plastic burette.

To determine solely the chamber volume, I used the old tried-and-true method.  I cut a round piece of 1/4” plexiglas with a small hole for liquid to enter and a smaller one next to it for air to exhaust.  Put the head upside down on the bench (tilt it enough for the air to get out of the exhaust hole in the plexiglas) with the valves inserted.  I used some vaseline to seal the plexiglas to the head (and to better seal the valves since they were old and worn) and let the liquid pour in, noting the number of milliliters (1 ml = 1cc) that had dripped in when the chamber is full.

To answer part of Steve’s question, according to TeriAnn’s Triumph web page a stock high-port TR head is 3.30” thick.

Duncan Charlton
Elgin, Texas USA

> On Sep 23, 2016, at 10:14 PM, Steve Yott <[email-masked]> wrote:
> 
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---

From: Kas Kastner <[email-masked]>
Date: Sat, 24 Sep 2016 08:35:29 -0700

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--001a11394e2c6f8b9c053d42a76a
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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.

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.
As in so many things like this I am just guessing along with everyone else.

*Never be beaten by equipment.*

On Fri, Sep 23, 2016 at 10:33 PM, Bill <[email-masked]> wrote:

> Yeah, but that=E2=80=99s just step one--after you measure the volume of t=
he
> 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 rati=
o.
>
>
> On Sep 23, 2016, at 9:19 PM, Steven Belfer <[email-masked]> wrote:
>
> 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.
>
> ~Steve
>
>
> In order to calculate the combustion chamber volume desired you need also
> know the bore, stroke, head gasket diameter and thickness, piston to line=
r
> 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 tha=
t
> the valve head thickness will affect this measurement.
>
> 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 desir=
ed
> compression ratio.  There are various head castings out there so I would
> not take the thickness into account except for a rough idea.
>
> 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!
>
> Steve Yott
>
>
>
> From: Fot [mailto:[email-masked] <[email-masked]>=
]
> On Behalf Of Stephen Borowski
> Does any one know the "chamber volumes" vs "compression ratio=E2=80=9D fo=
r the TR4
> high port head. What should the head thickness measure?
>
> All comments welcome!
>
> Thxs. Steve
> Unsubscribe/Manage: http://autox.team.net/mailman/
> options/fot/[email-masked]
>
>
>
> Unsubscribe/Manage: http://autox.team.net/mailman/
> options/fot/[email-masked]
>
>
>
>

--001a11394e2c6f8b9c053d42a76a
Content-Transfer-Encoding: quoted-printable

<div dir=3D"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 rat=
io of VOLUMES not pressures so the thing to put in your mind is the effect =
on the percentage of volumetric efficiency.=C2=A0<div><br></div><div>Now fo=
r that you have to take a fine pointed thing, aim it at the engine and ask =
&quot; How good are you?&quot; Then start at the top of the heap of volumet=
ric possibilities.=C2=A0 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 p=
ut a nice crackle in the exhaust note and seems to help a bunch down the lo=
ng straights.</div><div>As in so many things like this I am just guessing a=
long with everyone else.=C2=A0<div><br></div><div><br></div></div></div><di=
v class=3D"gmail_extra"><br clear=3D"all"><div><div class=3D"gmail_signatur=
e" data-smartmail=3D"gmail_signature"><p><strong><font color=3D"#000099">Ne=
ver be beaten by equipment.</font></strong></p></div></div>
<br><div class=3D"gmail_quote">On Fri, Sep 23, 2016 at 10:33 PM, Bill <span=
 dir=3D"ltr">&lt;<a href=3D"mailto:[email-masked]" target=3D"_blank">po=
[email-masked]</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote"=
 style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><d=
iv style=3D"word-wrap:break-word">Yeah, but that=E2=80=99s just step one--a=
fter you measure the volume of the combustion chamber you still need to kno=
w all the stuff Steve Yott mentions. At least you do if you want to know th=
e actual compression ratio.=C2=A0<div>=C2=A0<br><div><blockquote type=3D"ci=
te"><div>On Sep 23, 2016, at 9:19 PM, Steven Belfer &lt;<a href=3D"mailto:s=
[email-masked]" target=3D"_blank">[email-masked]</a>&gt; wrote=
:</div><br><div><span style=3D"font-family:Helvetica;font-size:12px;font-st=
yle:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-i=
ndent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:non=
e;display:inline!important">Get Kas&#39; book. There&#39;s a helpful sectio=
n describing how to CC the head using a plate of plexiglass and measuring h=
ow much fluid you can fill it with.<span>=C2=A0</span></span><br style=3D"f=
ont-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;le=
tter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;wh=
ite-space:normal;word-spacing:0px"><br style=3D"font-family:Helvetica;font-=
size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-a=
lign:start;text-indent:0px;text-transform:none;white-space:normal;word-spac=
ing:0px"><span style=3D"font-family:Helvetica;font-size:12px;font-style:nor=
mal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0=
px;text-transform:none;white-space:normal;word-spacing:0px;float:none;displ=
ay:inline!important">~Steve</span><br style=3D"font-family:Helvetica;font-s=
ize:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-al=
ign:start;text-indent:0px;text-transform:none;white-space:normal;word-spaci=
ng:0px"><br style=3D"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=3D"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=3D"cite" style=3D"font-fami=
ly:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spa=
cing:normal;text-align:start;text-indent:0px;text-transform:none;white-spac=
e:normal;word-spacing:0px">On Sep 23, 2016, at 8:14 PM, Steve Yott &lt;<a h=
ref=3D"mailto:[email-masked]" target=3D"_blank">[email-masked]</a>&gt; wrote:=
<br><br>Steve,<br>In order to calculate the combustion chamber volume desir=
ed 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).=C2=A0 These all make up the tot=
al volume which you need to calculate the chamber volume you need for the s=
tatic compression ratio you desire.=C2=A0 Also when doing a chamber volume =
test don&#39;t forget that the valve head thickness will affect this measur=
ement.<br><br>There are a good number of web sites out there that will do a=
ll these calculations for you and give you a required chamber volume for th=
e desired compression ratio.=C2=A0 There are various head castings out ther=
e so I would not take the thickness into account except for a rough idea.<b=
r><br>This all creates a &quot;static&quot; compression ratio and will not =
mean much when the dynamics of the cam and valve overlap come into play and=
 create the &quot;dynamic&quot; compression ratio.... wish there were a goo=
d method of calculating that!<br><br>Steve Yott<br><br><br><br>-----Origina=
l Message-----<br>From: Fot [<a href=3D"mailto:[email-masked]" =
target=3D"_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 Tri=
umph &lt;<a href=3D"mailto:[email-masked]" target=3D"_blank">fot@autox.=
team.net</a>&gt;<br>Subject: [Fot] TR4 Compression Ratio Calculation Questi=
on<br><br>Hello All,<br>Does any one know the &quot;chamber volumes&quot; v=
s &quot;compression ratio=E2=80=9D for the TR4 high port head. What should =
the head thickness measure?<br><br>All comments welcome!<br><br>Thxs. Steve=
<br>______________________________<wbr>_________________<br><a href=3D"mail=
to:[email-masked]" target=3D"_blank">[email-masked]</a><br><br><a h=
ref=3D"http://www.fot-racing.com" target=3D"_blank">http://www.fot-racing.c=
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<br></blockquote></div><br></div>

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---

From: Bill <[email-masked]>
Date: Sat, 24 Sep 2016 13:55:59 -0700

--===============2711103454588993297==

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Borowski

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></div></blockquote></div><br class=3D""></div></body></html>=

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