In the latest issue of the OCC Bulletin, Bjarne Bergengren of
Helsingborg, Sweden suggest the need to advance the timing to 5 or even
10 degrees before TDC when using modern fuel. As I am running 92
octane in my TB, I'm considering advancing the timing. What are the
advantages? What, if any, is the relationship between octane rating
and timing advance. As US actane ratings for unleaded gasoline are
running at 87, 89 and 92, respectively, what are the best advance
timing settings for these octanes?
On Engine data, where can I find the specs for the XPAG; e.g., torque
settings, standard bearing measurements, etc.? Happy 2000 everyone,
Skip (TB 0304)
Timing and Engine Data
-
Andy Bradley
- Posts: 13
- Joined: Fri Jan 07, 2000 11:33 pm
Re: Timing and Engine Data
In general, advance as much as you can get away with.
When you start to get pinging under load, back off. It all depends on carb settings, cam profile and timing, cylinder head shape, etc. But the idea is to get the maximum cylinder pressure to give the most oomph on the power stroke. Just keep an eye on temperature, and a ear open for excessive pinking, and you will have it. Aslo keep in mind, you cannot run as much advance on the cheap stuff as you can with the 92 octane. There is no difference in the actual fuel that burns between the 87 and the 92, it is just the additive package that changes. But even our cheap stuff in higher in octane than the mystery fuels that they used to run. Hence, the better advance curves that we can get away with. Also, if it looks like you can run a good advance, do check the total advance. You will probably want about 32-34 degrees total. Over 36, you are probably pinging up a storm. Cheers...Andy
When you start to get pinging under load, back off. It all depends on carb settings, cam profile and timing, cylinder head shape, etc. But the idea is to get the maximum cylinder pressure to give the most oomph on the power stroke. Just keep an eye on temperature, and a ear open for excessive pinking, and you will have it. Aslo keep in mind, you cannot run as much advance on the cheap stuff as you can with the 92 octane. There is no difference in the actual fuel that burns between the 87 and the 92, it is just the additive package that changes. But even our cheap stuff in higher in octane than the mystery fuels that they used to run. Hence, the better advance curves that we can get away with. Also, if it looks like you can run a good advance, do check the total advance. You will probably want about 32-34 degrees total. Over 36, you are probably pinging up a storm. Cheers...Andy
-
John Seim
- Posts: 57
- Joined: Sun Jan 09, 2000 2:12 pm
Re: Timing and Engine Data
Skip Burns wrote:
workshop manuals, using a light with leads connected to the distributor
and coil, you will end up with 5-6 degrees advance BTDC, when you check
the engine timing with a strobe light. The distributor advance starts at
low rpm.
Ths biggest thing about spark advance is the maximum advance allowed by
the distributor action shaft and plate. The majority of Lucas
distributors have a 15 degree (30 at engine) advance plate. The action
shaft and advance plate are stamped with what advance maximum is
possible with the plate. There was a factory bulletin , advising of the
availability of a 17 degree (34 at engine) action shaft and advance
plate. Calculations with the weight size, distributor case size,
indicates that the maximum advance possible with the stock Lucas
distributor is 19 degrees (38 at engine).
With the TF 1500 engine, the distributor action shaft and plate advance
was reduced to 12.5 degrees (25 at engine). This was to ensure long life
of the engine with the fuels available of the day. A 15 degree or 17
degree plate will give much better performance than the 12.5 degree
plate.
John Seim
When you set the distributor timing staticly, as described in the>
> In the latest issue of the OCC Bulletin, Bjarne Bergengren of
> Helsingborg, Sweden suggest the need to advance the timing to 5 or even
> 10 degrees before TDC when using modern fuel. As I am running 92
> octane in my TB, I'm considering advancing the timing. What are the
> advantages? What, if any, is the relationship between octane rating
> and timing advance. As US actane ratings for unleaded gasoline are
> running at 87, 89 and 92, respectively, what are the best advance
> timing settings for these octanes?
> On Engine data, where can I find the specs for the XPAG; e.g., torque
> settings, standard bearing measurements, etc.? Happy 2000 everyone,
> Skip (TB 0304)
workshop manuals, using a light with leads connected to the distributor
and coil, you will end up with 5-6 degrees advance BTDC, when you check
the engine timing with a strobe light. The distributor advance starts at
low rpm.
Ths biggest thing about spark advance is the maximum advance allowed by
the distributor action shaft and plate. The majority of Lucas
distributors have a 15 degree (30 at engine) advance plate. The action
shaft and advance plate are stamped with what advance maximum is
possible with the plate. There was a factory bulletin , advising of the
availability of a 17 degree (34 at engine) action shaft and advance
plate. Calculations with the weight size, distributor case size,
indicates that the maximum advance possible with the stock Lucas
distributor is 19 degrees (38 at engine).
With the TF 1500 engine, the distributor action shaft and plate advance
was reduced to 12.5 degrees (25 at engine). This was to ensure long life
of the engine with the fuels available of the day. A 15 degree or 17
degree plate will give much better performance than the 12.5 degree
plate.
John Seim
-
Peter Pleitner
- Posts: 83
- Joined: Wed Dec 01, 1999 7:53 am
Re: Timing and Engine Data
Hi Whitworth Head,
Well here are my 2 cents worth, plus some change. Am feeling negligent
since I haven't contributed lately.
First of all, unless you are running high compression, you are wasting money
buying premium fuel. XPAGs don't need the extra cost fuel injection cleaner
additives, and the higher the octane the slower the burn rate, because the
higher octane fuel blend is more stable under compression. The slower burn
rate is why you can advance ignition timing a little further on high octane.
First, lets think about what ignition advance does. It starts combustion
pressure on the piston before it is on the power stroke. This is negative
force which robs power, and is audible as pinging when the extreme advance
condition is approached. So I would argue that the greatest advance is not
necessarily the best state of tune.
Timing at idle is not very important for performance or engine health, as
long as the ignition can support a reasonably smooth idle. Timing at the
fully advanced stage is important and will determine your engine's health
and performance. Not enough advance is a common cause of overheating.
Static timing is fine for ordinary driving if your distributor is
functioning properly. There are two ways to check your distributor. One is
removing it and mounting it in an old fashion distributor bench top test
rig. These are getting rare. The other is a timing light that incorporates
a dial-in advance-retard degree function. This is the instrument I
recommend.
Prepare by getting your crank pulley marked clearly and distinctly for top
dead center and five degrees advance. You might want to convince yourself
that your TDC mark is accurate by using a probe in #1 spark plug and put two
temporary marks on your crank pulley, one for when upward motion of the
piston stops and one when downward motion of the piston starts, half-way
between these marks is TDC. A probe is a ridged pointer (the longer the
more accurate) and some sort of measuring fixture. A real Rug Goldberg rig
is what you'll likely build. And its time consuming but very worth while if
you've never done this before the engine was assembled. Also remember that
disturbing the carbon build-up on the piston crown can cause changes in
measurement. So make a small clean spot by gentle scraping.
Set your timing using the static method at TDC (do this because you will
first want to measure the maximum advance of your distributor). Warm up
your XPAG and then connect your timing light. Now dial in 30, then 34 or 38
degrees advance on your timing light and adjust your distributor until you
see your TDC mark at the pointer when your XPAG is running at about 2200
engine rpm (others may have better info on this spec since I'm writing
without benefit of reference material). Hopefully you will have now
determine which distributor advance mechanism you have. Then adjust your
distributor statically again to 5 degrees advance. Now run your XPAG with
timing light attached and dial in 30, 34 or 38 degrees (which ever you
determined is your distributor) and run the engine around 2200 rpm. You
should see your TDC mark line up with the pointer (note there will always be
some wander due to point bounce or loose bushings). If you don't loosen
your distributor and adjust it until you do then tighten it and double
check. Then drop rpms to idle, dial in 5 degrees on the timing light and you
should again see your TDC mark reappear at the pointer.
If it doesn't your distributor's advance mechanism is not operating to spec.
This is a common problem, first because the distributor is not clean and/or
well lubricated underneath the points plate, and second because I suspect
replacement advance springs are not up to spec. But the important thing to
note here is that your ignition timing at the fully advanced state is much
more important because at this speed and above is where your engine is
beginning to do its hard work, not at idle. And when it is working hard is
when it is burning maximum fuel and generating maximum heat and stresses.
Lastly, what happens between these two distributor speeds is what is called
the advance curve. You can plot this as a function of advance relative to
engine rpm. The best shape of this curve (usually a couple of straight
lines really) is determined by cam spec, altitude, carbs, and driving
style - too deep a subject here, or for me without some study.
Cheers, Peter
-----Original Message-----
From: John Seim [mailto:kingseim@earthlink.net]
Sent: Sunday, January 09, 2000 5:19 PM
To: Skip Burns
Cc: mg-tabc@eGroups.com; Phil Gross
Subject: [mg-tabc] Re: Timing and Engine Data
Skip Burns wrote:
workshop manuals, using a light with leads connected to the distributor
and coil, you will end up with 5-6 degrees advance BTDC, when you check
the engine timing with a strobe light. The distributor advance starts at
low rpm.
Ths biggest thing about spark advance is the maximum advance allowed by
the distributor action shaft and plate. The majority of Lucas
distributors have a 15 degree (30 at engine) advance plate. The action
shaft and advance plate are stamped with what advance maximum is
possible with the plate. There was a factory bulletin , advising of the
availability of a 17 degree (34 at engine) action shaft and advance
plate. Calculations with the weight size, distributor case size,
indicates that the maximum advance possible with the stock Lucas
distributor is 19 degrees (38 at engine).
With the TF 1500 engine, the distributor action shaft and plate advance
was reduced to 12.5 degrees (25 at engine). This was to ensure long life
of the engine with the fuels available of the day. A 15 degree or 17
degree plate will give much better performance than the 12.5 degree
plate.
John Seim
------------------------------------------------------------------------
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Well here are my 2 cents worth, plus some change. Am feeling negligent
since I haven't contributed lately.
First of all, unless you are running high compression, you are wasting money
buying premium fuel. XPAGs don't need the extra cost fuel injection cleaner
additives, and the higher the octane the slower the burn rate, because the
higher octane fuel blend is more stable under compression. The slower burn
rate is why you can advance ignition timing a little further on high octane.
First, lets think about what ignition advance does. It starts combustion
pressure on the piston before it is on the power stroke. This is negative
force which robs power, and is audible as pinging when the extreme advance
condition is approached. So I would argue that the greatest advance is not
necessarily the best state of tune.
Timing at idle is not very important for performance or engine health, as
long as the ignition can support a reasonably smooth idle. Timing at the
fully advanced stage is important and will determine your engine's health
and performance. Not enough advance is a common cause of overheating.
Static timing is fine for ordinary driving if your distributor is
functioning properly. There are two ways to check your distributor. One is
removing it and mounting it in an old fashion distributor bench top test
rig. These are getting rare. The other is a timing light that incorporates
a dial-in advance-retard degree function. This is the instrument I
recommend.
Prepare by getting your crank pulley marked clearly and distinctly for top
dead center and five degrees advance. You might want to convince yourself
that your TDC mark is accurate by using a probe in #1 spark plug and put two
temporary marks on your crank pulley, one for when upward motion of the
piston stops and one when downward motion of the piston starts, half-way
between these marks is TDC. A probe is a ridged pointer (the longer the
more accurate) and some sort of measuring fixture. A real Rug Goldberg rig
is what you'll likely build. And its time consuming but very worth while if
you've never done this before the engine was assembled. Also remember that
disturbing the carbon build-up on the piston crown can cause changes in
measurement. So make a small clean spot by gentle scraping.
Set your timing using the static method at TDC (do this because you will
first want to measure the maximum advance of your distributor). Warm up
your XPAG and then connect your timing light. Now dial in 30, then 34 or 38
degrees advance on your timing light and adjust your distributor until you
see your TDC mark at the pointer when your XPAG is running at about 2200
engine rpm (others may have better info on this spec since I'm writing
without benefit of reference material). Hopefully you will have now
determine which distributor advance mechanism you have. Then adjust your
distributor statically again to 5 degrees advance. Now run your XPAG with
timing light attached and dial in 30, 34 or 38 degrees (which ever you
determined is your distributor) and run the engine around 2200 rpm. You
should see your TDC mark line up with the pointer (note there will always be
some wander due to point bounce or loose bushings). If you don't loosen
your distributor and adjust it until you do then tighten it and double
check. Then drop rpms to idle, dial in 5 degrees on the timing light and you
should again see your TDC mark reappear at the pointer.
If it doesn't your distributor's advance mechanism is not operating to spec.
This is a common problem, first because the distributor is not clean and/or
well lubricated underneath the points plate, and second because I suspect
replacement advance springs are not up to spec. But the important thing to
note here is that your ignition timing at the fully advanced state is much
more important because at this speed and above is where your engine is
beginning to do its hard work, not at idle. And when it is working hard is
when it is burning maximum fuel and generating maximum heat and stresses.
Lastly, what happens between these two distributor speeds is what is called
the advance curve. You can plot this as a function of advance relative to
engine rpm. The best shape of this curve (usually a couple of straight
lines really) is determined by cam spec, altitude, carbs, and driving
style - too deep a subject here, or for me without some study.
Cheers, Peter
-----Original Message-----
From: John Seim [mailto:kingseim@earthlink.net]
Sent: Sunday, January 09, 2000 5:19 PM
To: Skip Burns
Cc: mg-tabc@eGroups.com; Phil Gross
Subject: [mg-tabc] Re: Timing and Engine Data
Skip Burns wrote:
When you set the distributor timing staticly, as described in the>
> In the latest issue of the OCC Bulletin, Bjarne Bergengren of
> Helsingborg, Sweden suggest the need to advance the timing to 5 or even
> 10 degrees before TDC when using modern fuel. As I am running 92
> octane in my TB, I'm considering advancing the timing. What are the
> advantages? What, if any, is the relationship between octane rating
> and timing advance. As US actane ratings for unleaded gasoline are
> running at 87, 89 and 92, respectively, what are the best advance
> timing settings for these octanes?
> On Engine data, where can I find the specs for the XPAG; e.g., torque
> settings, standard bearing measurements, etc.? Happy 2000 everyone,
> Skip (TB 0304)
workshop manuals, using a light with leads connected to the distributor
and coil, you will end up with 5-6 degrees advance BTDC, when you check
the engine timing with a strobe light. The distributor advance starts at
low rpm.
Ths biggest thing about spark advance is the maximum advance allowed by
the distributor action shaft and plate. The majority of Lucas
distributors have a 15 degree (30 at engine) advance plate. The action
shaft and advance plate are stamped with what advance maximum is
possible with the plate. There was a factory bulletin , advising of the
availability of a 17 degree (34 at engine) action shaft and advance
plate. Calculations with the weight size, distributor case size,
indicates that the maximum advance possible with the stock Lucas
distributor is 19 degrees (38 at engine).
With the TF 1500 engine, the distributor action shaft and plate advance
was reduced to 12.5 degrees (25 at engine). This was to ensure long life
of the engine with the fuels available of the day. A 15 degree or 17
degree plate will give much better performance than the 12.5 degree
plate.
John Seim
------------------------------------------------------------------------
Looking for educational tools for your kids?
Find everything you need at SmarterKids.com
http://click.egroups.com/1/645/0/_/60353/_/947456184/
eGroups.com Home: http://www.egroups.com/group/mg-tabc/
http://www.egroups.com - Simplifying group communications
-
Peter Pleitner
- Posts: 83
- Joined: Wed Dec 01, 1999 7:53 am
Timing and Engine Data
Hi Whitworth Heads,
I was called to a great Alsatian dinner and sent me previous message in
haste. Now I found an error in the paragraph starting:
Set your timing using the static method at TDC (do this because you will
first want to measure the maximum advance of your distributor). Warm up
your XPAG and then connect your timing light. Now dial in 30, then 34 or 38
degrees advance on your timing light and adjust your distributor until you
see your TDC mark....
Remove "and adjust your distributor" in the last two lines above. I decided
it best to first determine what your distributor does at max advance, but
forgot to remove this statement.
Sorry for this error.
Cheers, Peter
I was called to a great Alsatian dinner and sent me previous message in
haste. Now I found an error in the paragraph starting:
Set your timing using the static method at TDC (do this because you will
first want to measure the maximum advance of your distributor). Warm up
your XPAG and then connect your timing light. Now dial in 30, then 34 or 38
degrees advance on your timing light and adjust your distributor until you
see your TDC mark....
Remove "and adjust your distributor" in the last two lines above. I decided
it best to first determine what your distributor does at max advance, but
forgot to remove this statement.
Sorry for this error.
Cheers, Peter
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