This table has been floated around the list before:
Vacuum Advance dist. 40795
Inches Hg Degree Crank advance
2.0 0
3.0 1
4.0 1.75
5.0 2.5
6.0 2.75
Centrifugal Advance
RPM Degrees Crankshaft advance
500 0
700 0-2
1200 5-7
1600 9-11
So if you believe this is indeed crank degrees, you get a total max
advance of:
4 + 2.75 + 11 = 17.75 degrees
But I don't believe the above figures are in crank degrees, but
rather distributor degrees (half of crank). But the initial advance
maybe crank. So that gives you:
4 + 5.5 + 22 = 31.5 degrees
Which seems like a reasonable number. I recently read a book on
powertuning ignition systems, and it claims the combustion chamber
shape is the biggest factor in how much advance the engine can
tolerate. The one that most closely matches the TR head was called a
"bathtub" chamber, and they said 33-34 degrees. So that would be in
line with second calculation.
-Darrell
On Sep 21, 2007, at 8:36 AM, spamiam@comcast.net wrote:
> Does anybody know the ignition advance information for the TR4A?
>
> I know that stock static advance is 4 degrees BTDC, but what is the
> full vacuum advance? What is the full mechanical advance?
>
> Someone said to me that these engines can not tolerate all that
> much total advance (I.E. less than 30 degrees). I would have
> expected that a total advance in the mid-30's would have been about
> right!
>
> -Tony
> _______________________________________________
> darrellw@ipns.com
>
> This list supported in part by the Vintage Triumph Register
> http://www.vtr.org
>
> Triumphs mailing list
> Triumphs@autox.team.net
> http://autox.team.net/mailman/listinfo/triumphs
_______________________________________________
This list supported in part by the Vintage Triumph Register
http://www.vtr.org
Triumphs mailing list
Triumphs@autox.team.net
http://autox.team.net/mailman/listinfo/triumphs
|