Would it help to advance my timing from 10 to 14 degrees btc on my 1989 F150 with a 302. I read one post that said doing this would give more power if you premium unleaded.

 

It might help a bit..but i've heard only go as high as 12, or as high around there as u can get without geting engine ping.

 

More advance will give you more power, more retard will give you more torque. 14 should not be a problem, especially on premium gas.

 

>More advance will give you more power, more retard will give
>you more torque. 14 should not be a problem, especially on
>premium gas.


What the difference between more power and torque??? I pull a camper sometime so would I need more power or more torque???
I thought there wasn't much difference between the two, please explain the difference.

Thanks

 

Torque gets you rolling, hp keeps you rolling...More torque will give you more pulling or towing capacity at usually lower rpms...more hp will give you better top end power...I usually retard my timing to about 6-7 BTDC for towing and the truck will also run cooler...but if I want to put the truck on the drag strip, then it's advanced to 14 or 15 to get me down the track quicker...

 

Hey Slik, the reason why your truck runs cooler when you retard your timing is because you have just reduced the dynamic cylinder pressure (makig the engine weaker). This does not improve low end torque, rather hurting both torque and HP. Advance it to the limit: the reason why your fatory timing is set so retarded is to account for the worst possible scenarios, including very low octane fuel, and high cylindar deposits, contributing to octane-depreciation. The reason why you advance timing is because you want peak cylinder pressure to occur at 20 degrees after top dead center, and since the flame front travels slower than the piston in it's bore, and average gasoline requires about 36 degrees of head start to acheive maximum pressure at 20 ATDC. Now, the reason why this improves both horsepower and Torque are improved is because timing improvements will maximize cylinder pressure. Torque at a given RPM is a function of the integral of cylindar pressure with respect to time, and work is the integral of power, so you differentiate Torque to get power, or you could use a linear approximation. The bottom line is, maximizing cylinder preessure increases both, and detonation resistance is dependant on cylindar pressure and timing advance. If you have 130 psi of dynamic cylinder pressure, then you can advance your timing all the way up to optimal timing, which is 36 degrees BTDC, depending on the chemistry of that particular fuel. Higher octane fuel is more resistant to detonation, so although you could advance it more, you'd be losing cylindar pressure, since the peak cylinder pressure would occur less than 20 degrees ATDC, which mechanically is less leverage on the crank, and therefore less torque. If you still don't beleive me that timing advance helps both torque and power, then I'll submit a mathematical proof, and prove it beyond a shadow of a doubt.
Cadet Sergeant John F. Daly III,
South Carolina Corps of Cadets,
The Citadel, Charleston, S.C.
The TorqueKing

 

You can run math all day long, but I'm telling you rule of thumb from the old timers, racing folks, and the seat of my pants...and I trust what I feel...when I got a load and retard the timing to 6 degrees, my load tows better...now the other thing you have to consider and I believe the numbers that you were quoting is the total advance curve...I know I can barely get the truck away from a stop sign if my initial advance is 20 degrees...but get it up to 2500 rpm and it'll rocket off the line (that's where the stall converters work well on the hi-peformance cars/trucks)...so how you drive, the rpm range that you are working with, the total advance curve including total advance and how quickly it comes in and even the vacuum advance are all variables that work together for the best combo...Our race car has an initial of 32 and total of 36...but we idle at 1200-1500, have 5.57 gears, no vacuum advance, and we don't care about low end torque...

 

Okay, I can agree with the fact that having an intitial value lower than the total timing would help it launch better. We were talking about 2 different things, I was preaching about total, you were talking about initial. Crankshaft momentum is probably the factor here, as the momentum decreases, it shifts the point where peak cylinder pressure would give maximum acceleration of the piston father after TDC, it's all about leverage. I;m trying to think of an obvious mechanical example of this, but it doesn't matter, as long as you agree that depending on the fuel used, both Peak torque AND power will be made at 36-38 degrees total.

 

Absolutely, and I've been thinking somewhat backwards on more torque with more retard. I'll have to concede. Retarding the timing will back off the timing on the top end which will help prevent spark knock while towing, and while you will get maximum power (torque and hp) at the maximum advance, you also run a higher risk of spark knock, especially with a vacuum advance. Thanks for the good discussion.

 

Thanks Slik,
This Forum would be no fun if everybody with agreed with you, and you definately wouldn't learn anything. I'm sure you can tell that I'm an engineering student, young, well-read about all things automotive, but I'll be the first to tell you that there's something about having done it that just can't be replaced, and that's where I can learn mountains from guys like you and Franklin, and Mark Convil. I'd still like to show you the program I wrote to calculate compression ratio, and just the other day I wrote one to convert fuel injector flow (#/hour) into ft^3/min (cfm). That one was a doozy, the problem is, I wrote them on a program called MathCAD, which is great at handling extreme algebra and calculus, but it won't interface on this page. Look forward to talking to you in the future.
John F. Daly III
The TorqueKing

 

Sounds awesome....you need to come help us set up our race car!!! Now, that's a trick and it would be nice to apply all the setup stuff from the old timers to the laws of physics!!! These guys really know how to set stuff up and to react the way you want it too, but there are so many variables and when you change one thing, there are about ten other things that are affected....

 

 

....., but there are so many
>variables and when you change one thing, there are about ten
>other things that are affected....

Exactly one of the reasons I got out of racing. The other was "Know how to make a small fortune racing? Start with a big one."

Right on slik


Chuck

"The Ultimate small-block lives"