Timing Question??????

Can someone explain to me the reasoning behind retarding the timing in high gear for better MPH? I've heard it works and im wondering why?
Thanks.

 

not trying to push the piston back down. Easiest explanation I can think of.
Art

 

beleave me it works..Dave
www.myspace.com/daveloweswr

 

oil painting theory sounds good......

 

Maybe if you load about 100 lbs of paint in the car and then throw it out at the gear change you can pick up a couple of 100th's.

 

paint

Isn't that how they stripe the roads in S.C. Jody? lol

 

I just bought 200 gallons of paint and dropped a few grand on misc art supplies from Chang Vang..... now back to the question.

So nobody know's...... How does the engine know what gear the car is in?

 

Timing

highest load..working compression..easier to detonate..consider hi gear is correct timing and lower gears are increased timing (lower load)

 

Ha Ha Glenn, nope.... we usually just hold a yellow dog yankee down to the asphalt and drag his rear down the road. Find it leaves two nice stripes down the center line. hehehehe Happy Thanksgiving. Back to the question..... I used to retard in high gear and really could'nt see much diff., however my tuneup was prob. off some. Have been told by others that at less load the motors need less timing so they pick up some MPH, just wire the retard switch to your shifter/ shift light/ shift timer or rpm switch in your msd box.

 

Ok Bill, that's helpful.

 

man did this thread get side tracked..Dave

 

Look at it from this way,..
As the rod and piston come up in the cylinder on the compression
stroke with your given timing you have in it (advance) the sooner it will fire before it gets to
top dead center making the piston and rod work harder to get to tdc and the next revolution in the motor.
take timing away (retard) the later it will fire, putting
the piston and rod closer to top dead center
making it easier on the motor to make its next revolution, thus
freeing up a little hp because the motor is not working as hard.

 

I think the higher the cylinder pressures, the more advantage you see from doing this. Back in my TD days on my Nitrous motor, we gained 7mph by pulling as much as 8deg out of it! A blower motor won'r require this much. At least not that I have seen??!! Curious as to what others have experienced? I would tell ya what we pull out but my Crew Chief would slit my throat

 

If this theory is correct then why does it only work in high gear?

 

So if the rig picks up 7 mph with 8 less in high gear, Say 38 in first and second, 30 in 3rd, how would it run with 30 the whole time? if worse why?

 

are we talking about a blown alky or injected nitro vehicle..?????

,...You tell me ????

Maybe its because its at the top of its power band (gear wise), where all it does is pull from there on with out another shift coming, ????
does anybody test
and pull timing out just before every shift, hince 8973 box, or is it just because this happends to fast in between shifts to do it then, and better in high ????

You tell me ????

how about the same theory with advancing or retarding a cam
or,...
adjusting your valves looser or tighter than the suggested cam spec.

amazing stuff aint it.

 

I don't have your answer, but here are some comments;

I beleive passenger vehicles at highway speeds run some rediculous high advancement numbers, but under higher load (more throttle opening, etc) it gets retarded.

Does the rise time of the magneto change when the cylinder pressure changes?

Has anyone done tests comparing ignition timing requirements for different boost levels?

My experience when comparing my roots stuff to like N/A motor combinations, the blower deal makes peak power with about 5° less advance. This supports the fact that with more cylinder pressure it takes less advance.

 

In a car with a clutch maybe it actually reduces the power slightly and stops the motor driving through the clutch allowing more power to actually reach the rear tyres not get wasted in the can? a lot of people reduce counter weight to stop there cars shaking or smoking the tyres in low gear which results in not enough counterweight to lock up the clutch at the end of high gear so this could possibly allow the lutch to lock up?

 

To me this answer makes more sense than all the others because hp = mph so retarding and taking power away does not add up to me but thats just my opinion.

 

Top gear retard

My understanding of TGR goes like this
-in the lower gears the engine is able to build revs fast due to reduced load and therefore the cylinder pressure doesnt build up above the piston fast enough to cause detonation at a given tune
-in top gear the load is high and the engine cant rev as quickly, therefore the piston doesnt move (accelerate) down the bore as fast and excessive pressure builds above the piston - detonation
I know this sounds a bit unfeasable because it is all happening so fast, but if you think about it, it is to do with piston acceleration rates away from TDC at different LOADS (not revs)
This applies not only to the blown engines most guys here have, but also to N/A and petrol engines used in slower classes. Very few of those racers have the adjustable clutchs of TA.
Jim