retard timing while racing

bigblock429 November 1st 2011, 10:21 pm

is there any real horsepower to gain by retarding your timing lets say 3 degrees going into high gear while racing? i was told that its frees up horsepower and its worth a least a tenth or 1-2 mph

71f150 November 2nd 2011, 12:59 am

If your engine makes max power at 34 degrees and you're running 37, then yeah there is a real HP gain there. Otherwise, no.

whatbumper November 2nd 2011, 8:24 am

guys used to do it a lot more. you can run more timing down low than you wold normally and then when the load is at its highest, high gear with a slower rpm increase, you can pull a couple of degrees out to get back to the ideal timing. we did it back in the day when our fuel wasn't as good as now and it was good for a couple of mph but the et was about the same.

bigblock429 November 2nd 2011, 9:41 pm

thanks

BOSS 429 November 2nd 2011, 11:36 pm

bigblock429 wrote:thanks

late 80s, taking out 2 in 4th would be about a .9 gain in et, almost a tenth, my freind made a switch that the shifter would come in contact with to do this. all for the reason above, but today we dont

rmcomprandy November 3rd 2011, 9:59 am

bigblock429 wrote:is there any real horsepower to gain by retarding your timing lets say 3 degrees going into high gear while racing? i was told that its frees up horsepower and its worth a least a tenth or 1-2 mph

A real misnomer ... it should have been referred to as lower gear advance instead of high gear retard; (although doing both is usually what was done).

Example: a car which runs best with 34 degrees of total timing may pick up a few hundredths or more by running 37 degrees in the lower gears and dropping it back to 33 in high gear only.

71f150 November 3rd 2011, 9:13 pm

rmcomprandy wrote:
Example: a car which runs best with 34 degrees of total timing may pick up a few hundredths or more by running 37 degrees in the lower gears and dropping it back to 33 in high gear only.

Why? And his is something I'd really like to understand.

I could understand if MBT changed at high speed because of differences in airflow, but that would mean that MBT might have been 34 on the dyno and became 37 at speed. Either way it's still MBT.

If the vehicle is traction / clutch / converter limited, then I could understand that also, but otherwise, why else would you want to produce less than peak HP for any RPM in a race car whose primary goal is acceleration? I'm not arguing - I'm asking an honest question as there is something to be learned here.

rmcomprandy November 3rd 2011, 11:43 pm

71f150 wrote:
rmcomprandy wrote:
Example: a car which runs best with 34 degrees of total timing may pick up a few hundredths or more by running 37 degrees in the lower gears and dropping it back to 33 in high gear only.
Why? And his is something I'd really like to understand.

I could understand if MBT changed at high speed because of differences in airflow, but that would mean that MBT might have been 34 on the dyno and became 37 at speed. Either way it's still MBT.

If the vehicle is traction / clutch / converter limited, then I could understand that also, but otherwise, why else would you want to produce less than peak HP for any RPM in a race car whose primary goal is acceleration? I'm not arguing - I'm asking an honest question as there is something to be learned here.

RATE of acceleration, RPM, (as related to the torque curve), and LOAD have a lot to do with required MBT for extracting the maximum amount of power; it is NOT always the same under those differing conditions, even with the same engine.
A singular MBT number through all conditions is simply the best AVERAGE of what the engine will use.

71f150 November 4th 2011, 1:34 am

Thanks Randy, I knew there was something I overlooked and you nailed it with the point about a "singular" MBT (ie - distributor timed).
I'm used to EFI, where you can set MBT timing for all RPM and load/efficiency points if you want to.

Having said that though, setting the ignition to MBT at all points in the lower RPMs makes for one heck of twitchy/sketchy driver on the street. Very Happy

rmcomprandy November 4th 2011, 10:35 am

71f150 wrote:Thanks Randy, I knew there was something I overlooked and you nailed it with the point about a "singular" MBT (ie - distributor timed).
I'm used to EFI, where you can set MBT timing for all RPM and load/efficiency points if you want to.

Having said that though, setting the ignition to MBT at all points in the lower RPMs makes for one heck of twitchy/sketchy driver on the street.

Not really ... I have run many OEM type engines on the dyno for LBT/MBT to arrive at a constantly variable ignition timing map: (and fuel map).
The ECM computers for OEM fuel injection have map surfaces which are gotten in just that way.
That, of course, would be almost impossible to do with a system which is not "programable" or using an engine which can't run at all throttle positions at differing loads for a good length of time. In those other cases a "best guess" scenario is all which can be tested once the average MBT is found.

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