Alex,
OK Bore on a 289 = 4.0 + .060 = 4.060
Stroke on a 289 = 2.87" or 73mm or 7.3 cm
=(4.060/2) squared X pi X 2.87"=swept volume
in metric (10.3124cm/2)squared X (22/7) X 7.2898cm
=swept volume 609.0684cc
If you have a piston arrangement that yields around 12.5:1 ratio with a 48cc
head then the following must be true:
The piston is flat with around 2 cc valve reliefs
The chamber is 48cc with the valves you are using and they are not too sunk.
The compressed gasket is .010 thick
The deck height is 0"
The Bore is 4.060
The total Final compressed area is 52.12235 including gasket volume
And the Total volume at piston BDC is 52.12235 + 609.115657 = 661.238012
This arrangement yields 12.6862:1 Compression
Keeping everything else constant and just changing your combo to the Dart
heads at 64CC yields a Compression ratio of 9.94149:1 a really nice ratio.
The 54cc heads give 11.47988:1
This is assuming a flat piston as I would have to recalculate if the piston
has a dome.
I hope this fully answers your question, but if not I did a quickie
spreadsheet if you want it.
I am out of town for the week so don't expect a quick response.
Best regards,
Tim Ronak
B382000680
-----Original Message-----
From: Alex MacLaurin [mailto:Alex_MacLaurin@telus.net]
Sent: Friday, January 21, 2000 3:04 PM
To: Ronak, TP (Timothy)
Subject: Re: Performance Tuning the Tiger
Tim- My motor is .060 over 289 that has 12.5:1{with I think
48cc 289 head]
forged TRW pistons. the motor was originally built with 54cc
351 heads that
were changed to 64cc dart heads. The motor pulled a
corrected 319.3 hp to the
wheels in November and have never had a problem using 94
octane pump gas.
Thanks again Alex
----- Original Message -----
From: Ronak, TP (Timothy) <Timothy.P.Ronak@akzo-nobel.com>
To: 'Doug Mallory' <rdmallory@earthling.net>; Ronak, TP
(Timothy)
<Timothy.P.Ronak@akzo-nobel.com>; 'Alex MacLaurin'
<Alex_MacLaurin@telus.net>; Ronak, TP (Timothy)
<Timothy.P.Ronak@akzo-nobel.com>; 'Bob Palmer'
<rpalmer@ames.ucsd.edu>
Cc: 'Tiger News Group List' <tigers@autox.team.net>
Sent: Friday, January 21, 2000 1:15 PM
Subject: RE: Performance Tuning the Tiger
> Alex,
> Theo pointed out that I did not answer the question!!!
Figures he would
zing
> me on that.
> To do the calculation give me the bore size of you engine,
the stroke and
> the piston configuration, we can make some assumptions by
working
> backwards. i.e.: if you have 11:1 pistons with your 54cc
heads if we know
the
> swept volume we can tell you how much the 64 cc heads will
drop
compression
> relative to your cubic inches.
> Regards,
> Tim
>
> -----Original Message-----
> From: Doug Mallory [mailto:rdmallory@earthling.net]
> Sent: Friday, January 21, 2000 1:53 PM
> To: Ronak, TP (Timothy); 'Alex MacLaurin'; Ronak, TP
> (Timothy); 'Bob Palmer'
> Cc: 'Tiger News Group List'
> Subject: RE: Performance Tuning the Tiger
>
> Well stated ! That was a collage course in two paragraphs.
>
> Rule of thumb was for every 1lb before ignition you get
> 10lbs after. That
> is why ignition timing is more critical when you start
> adding compression.
>
> Doug
>
>
>
> At 02:08 PM 1/21/00 -0600, Ronak, TP (Timothy) wrote:
> >Alex,
> >To determine compression it depends on whether you talk
> about static
> >compression or Dynamic compression.
> >Static Compression
> > i.e.: the compression based on the swept volume of the
> cylinder bore that
> >is displaced by the engine as it moves the piston. You
> simply take the bore
> >say 4" an put it into the formula for area of a cylinder
> lets presume the
> >stroke is say 3.48 (Chevy 350 sorry guys) for
(4/2)squared
> X pi X Length of
> >the cylinder 3.48" for 43.7485 cubic inches or X 8 =
> 349.988 ci (small block
> >350) . or in Metric 4" = 10.16 cm and 3.48" = 8.8392
cm
> the formula then
> >gives roughly 25.8064cm X 3.14285714285 X 8.8392 =
> 716.9106 cc.
> >
> >If we assume zero deck height no valve relief or dome and
> no gasket the
> >ratio would be ((716.9106 swept volume + 54cc Head
> volume)/54cc) : 1 or
> >13.276:1 compression.
> >
> >To do your computation we would need Bore size, dome and
> piston valve
> >relief, volume and thickness of the compressed head
gasket
> and piston to
> >deck height.
> >
> >That gives you static compression.
> >
> >Dynamic compression
> >What you really want is dynamic compression and get it
> around 195lbs of
> >compression for pump gas. And you can do this with a 10:1
> or a 11:1 or a
> >12:1 or a 13:1 compression ratio depending on when you
> choose to close the
> >intake valve in relation to the position of the piston in
> the bore. It
> >depends what you plan to use the engine for but I have
seen
> 10.5:1 motors
> >perform significantly better than 11.8:1 motors because
the
> produced more
> >cranking cylinder pressure.
> >
> >I hope that helps,
> >Tim Ronak
> >B382000680
> >A Canadian forced to stay indoors while it is cold out.
> >
> >
> > -----Original Message-----
> > From: Alex MacLaurin
> [mailto:Alex_MacLaurin@telus.net]
> > Sent: Friday, January 21, 2000 12:11
PM
> > To: Ronak, TP (Timothy); 'Bob
Palmer'
> > Cc: 'Tiger News Group List'
> > Subject: Re: Performance Tuning
the
> Tiger
> >
> > With all this talk about compression, I
> have a question: if a
> >motor has 11:1
> > compression with a 54cc chamber and all
> variables stay the
> >same, how much
> > compression does the engine have with a
> 64cc chamber?
> >
> >
> > ----- Original Message -----
> > From: Ronak, TP (Timothy)
> <Timothy.P.Ronak@akzo-nobel.com>
> > To: 'Bob Palmer' <rpalmer@ames.ucsd.edu>
> > Cc: 'Tiger News Group List'
> <tigers@autox.team.net>
> > Sent: Friday, January 21, 2000 10:14 AM
> > Subject: RE: Performance Tuning the
Tiger
> >
> >
> > > Bob,
> > > 195 ....so I was told ... is about the
> optimal pressure to
> >avoid excessive
> > > heat generation on the compression
> stroke and not use too
> >much power to
> > > compress the next charge when running
> pump gas. If you
> >were to optimally
> > > tune your engine you could probably
> retard the cam 1
> >degree close the
> > > intakes a little later drop the
cylinder
> pressure for an
> >average of 195
> > > (190-200 range between cylinders) and
> get a little more
> >power out and it
> > > might even run slightly cooler. IMHO
> This explains why you
> >do not have
> > > detonation. But didn't you run the car
> at 60 degrees
> >advance. I hope now
> > you
> > > are around 36-38 Total at 5000+ RPM. I
> hope someday I can
> >go for a ride.
> > > Regards,
> > > Tim Ronak
> > >
> > > -----Original Message-----
> > > From: Bob Palmer
> [mailto:rpalmer@ames.ucsd.edu]
> > > Sent: Friday, January 21, 2000 8:57 AM
> > > To: Ronak, TP (Timothy);
> MWood24020@aol.com;
> > > TSMIT@isotel.com;
> rdmallory@earthling.net; Ronak, Timothy
> >P;
> > > tigers@autox.team.net
> > > Subject: RE: Performance Tuning the
> Tiger
> > >
> > > Tim,
> > >
> > > After you guys taught me the proper
way
> to do a
> >compression
> > > test (plugs
> > > pulled, WOT) I get 195-205 psig
> depending on which
> >cylinder
> > > and which day.
> > > I'm at sea level here, but of course
> that doesn't affect
> > > psig, just psia.
> > >
> > > Bob
> > >
> > > At 07:57 AM 1/21/00 -0600, Ronak, TP
> (Timothy) wrote:
> > > >Bob,
> > > >I have to agree with you about the
> effect removing and
> > > sharp spots from the
> > > >combustion area will have on
> detonation. The key to
> > > avoiding the excessive
> > > >pressures is by changing where the
> Intake valve closes in
> > > relation to the
> > > >piston traveling up on the
compression
> stroke. What is
> >your
> > > cylinder
> > > >pressure warm with all of the plugs
out
> ... or have you
> > > tested it? The
> > > >method I will use on y 302 will be to
> chose the desired
> >cam
> > > profile and then
> > > >increase compression (or advance the
> cam) until I obtain
> > > about 195 lbs
> > > >cylinder pressure cranking. My
> experience is similar to
> > > yours in that
> > > >compression is fine provided that the
> combination once
> > > assembled gives you a
> > > >usable cylinder pressure. It may be
> that the guy who has
> >to
> > > run race gas
> > > >needs to install a cam with a little
> more overlap or one
> > > that closes the
> > > >intake valve a little later reducing
> the amount of
> >cylinder
> > > pressure the
> > > >piston can build. I do know that back
> in the race car
> >days
> > > we had an engine
> > > >that was 14:1 (remember that car Theo
> .. it was blue and
> > > yellow) it made
> > > >over 220 cranking cylinder pressure
and
> we had to run
> >C-14
> > > and methanol in a
> > > >15% and 85% ratio respectively or it
> detonated like
> >crazy.
> > > >My 2 cents too,
> > > >Tim Ronak
> > > >B382000680
> > > >PS: It is amazing how a well placed
> email gets us back on
> > > the performance
> > > >topic....YEEHaaaww!
> > >
> > > Robert L. Palmer
> > > UCSD, Dept. of AMES
> > > 619-822-1037 (o)
> > > 760-599-9927 (h)
> > > rpalmer@ucsd.edu
> > > rpalmer@cts.com
> > >
>
>
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