Varying Timing With Increasing RPM??

I was thinking one day in the jet.....

"Would there be an advantage to adding timing as RPM increases?"

Sometimes I have a little too much time on my hands and was wondering if there was any knowledge (that anyone wanted to share) on this subject. I understand timing curves at lower RPM on wedge stuff, but let's say you end up at 30-32 as a base (fuel heads) and say 26 base (fat head), would adding a certain amount of timing help with lugging the motor at lower RPMs (not having 35, 30 respectively at say 4500-5000) and then bring timing up to those numbers as RPMs increase and dwell time decreases?

My previous gas/wedge experience was to attempt to achieve maximum cylinder pressure about 14* ATDC, does this hold true for alcohol?

Something interesting to think about............let me know what you think

 

Most motors require the maximum timing at the launch as the most power/torque is needed. Typically, timing is pulled out as you go down the track for 2 reasons, to reduce the risk of hurting the motor, and because the engine runs free-er with less timing in it, resulting in higher speeds.

 

Interesting....

Thanks Ken, very interesting..... Never thought of letting the motor run free-er with less acceleration going on down track. Thanks.

 

I COMPLETLEY DISAGREE OR AM READING POST WRONG
if a promod style car left on full timing it would BLOW the tires off imeditaly

we leave at 20 deg and shoot for 28 by 1.40 sec into run and stay at 28 untill finishline depending on track

 

Your talking -6/-18 from base timing right ? Say base is 28 - 6= 22deg

 

I guess it depends what kind of car/motor/fuel you are talking about

 

I retard for the first 1.5 seconds in the Launch Retard graph on the Grid, this post is about overall timing with RPM and whether timing needs to advance as RPM increases down track. Mainly a flame travel vs. RPM vs. peak cylinder pressure discussion.

 

IMO and experience, if you are hurting parts because of too much ignition timing lead, you would make more power with less timing.

 

That's not true. Most promods run 27 degrees leaving the line. Then back it out by .8. Just for that extra umph to gt off the line. Then car setup and engine mgmt takes over. If you pull timing out in high gear you have to pull fuel as well. And yes it will go faster the trick is how much and when.

 

timing

27-28 deg off line with any power will make it ten foot ....or they have a loose converter and will only 1.00 60ft

 

I've gone 3.2g @.960 60fts leaving on full timing on some pretty bad tracks in Canada. If your blowing the tires off try less gear blown 69. I've seen rocky deliecy go 5.97 on those same tracks with a convertor Lenco deal and he leaves with full power. His mcamis car will go down a dirt road. I think it all boils down to how well everything jives together. One thing is not the cure all for everyone. Some accelerate an engine with timing , some with gear.

 

timing

I guess the old man tuning our stuff doesnot know what he is doing
and we cant get less than a 1,25 box in the trans ,we don't blow the tires off because we drop 8 out at the hit and roll back in to full timing by 1.2

 

In our USAC midgets (injected methanal 200inch pushrod 4cyl) the common practice is retard the base timing between 2 and 4 degrees as the motor picks up RPM coming off the corner and down the strait-away. We have a secondary profile that driver can switch to if the track slicks off and we struggle with traction on corner exit that is basically a flat line of a 4 degree retard.

What are your thoughts on this practice?

 

Exactly,
Do you agree (on an optimal track) that we should be pulling timing out of it as the RPMs pick back up after the car exits the corner?