Quick FC/Pinto Engine Tuning Question

[racer27]

We just re-installed our freshened head. We set timing to 38 Deg. Builder says set timing from 38-40 deg. Seems a little lower on torque then previously. Does moving the timing closer to 40 have any impact on the torque?

[Art Smith]

ignition, mixture, and the combination of the two will all effect torque.

was jetting adjusted for local conditions versus conditions on the dyno? if not, I'd do that before banging on the distributor. how are you assessing the combination of mixture and ignition timing: chassis dyno; EGT's; color of the tail pipe; color of the plugs; driver feel???

if the jetting is right/close, try a little more advance.......... YMMV

Art
artesmith@earthlink.net

[Brian]

Not that I'm a dyno expert - but I did stay in a Holiday Inn Express last night...

I talked about this once some years ago, with Ted Martin - a contemporary and competitor to Keith Duckworth, FWIW - and he told me that I needed to find MTBT - Minimum Timing Best Torque. If you plot torque vs timing, what you find is that as you increase timing, you reach a plateau where a further increase in timing does not result in an increase in torque (remember that a dyno only directly measures torque, and there is a mathematical conversion to HP). So you sweep timing and look for where torque stops increasing.

Then, you jet for that timing to optimize it, then you sweep timing again to see if a different timing now results in a different MTBT point, then you rejet for that new timing, until it's lunch time and you quit. Or the engine blows up from all the dyno pulls. Or it loses power because it needs a rebuild. Or you run out of dyno gas.

So increasing your timing to 40 degrees may help, or may just get you closer to detonation... sorry

Funny story - Ted did most of his serious engine tuning and design in the early 1960's. Then - the way you found MTBT was you had your mechanical dyno with a giant dial and a needle that pointed to a torque number, and you went into the dyno chamber, cranked the engine up to full RPM, and grabbed the distributor and started twisting until the number on the dial peaked out. Or so he told me...

brian

[azjc]

Funny story - Ted did most of his serious engine tuning and design in the early 1960's. Then - the way you found MTBT was you had your mechanical dyno with a giant dial and a needle that pointed to a torque number, and you went into the dyno chamber, cranked the engine up to full RPM, and grabbed the distributor and started twisting until the number on the dial peaked out. Or so he told me...

brian

Heck... I'd seen Formula Atlantic engines done that way in the LATE 70's! Where I worked they rented space to an engine builder for his dyno, was located just across from an airport - once the fire crews rolled over thinking the exhaust coming out the vent on the roof was a fire! Nothing quite like the sound, smells & vibration of a BDA going full song and being tuned on the dyno...

[Brian]

I freely confess that I am scared of dyno's. I work on them fairly rarely, a couple of times a year at most, and I kind of crouch behind the operator, 15 feet from the engine, behind a wall and a sheet of lexan, while they run the engine up to redline for a 10 second pull. What if it explodes, as it clearly wants to?

Then, I bolt the engine in my car, 6 " behind my head, and happily run it up to redline repeatedly for 20 minute race sessions, without a care in the world. Out of sight, out of mind I guess.

Brian

[Steve Demeter]

Out of the way of flying parts.....

[Jonathan Hirst]

Nothing quite like the sound, smells & vibration of a BDA going full song and being tuned on the dyno...

Here, here.

Another favorite was when I was working in a prep shop and the engine builder fired up a DFV on the Dyno. The memory still makes me smile.

Sorry for the hijack.

[LFFR]

...the way you found MTBT was you had your mechanical dyno with a giant dial and a needle that pointed to a torque number, and you went into the dyno chamber, cranked the engine up to full RPM, and grabbed the distributor and started twisting until the number on the dial peaked out. Or so he told me...

brian

...Actually, the dyno guys I use still do it that way. Only difference is that they use a chassis dyno. They do have a plate that drops into a slot in the floor that separates the spinning wheel from the guy who twists the distributor.

John Mihalich, Jr.

[DaveW]

I always used to set my Pinto cam timing a degree or two advanced (offset cam keys) from the QS dyno setting. That shifted the peak torque and HP lower on the RPM curve. IMO, that always gave better performance without having to buzz the crap out of the engine.

[Peter Horvath]

Will the engine builder do this if you ask him to?

[Art Smith]

here's an idea for something to provide your engine builder. scribed lines added to the pulley on the dyno would enable painless adjustment of the engine's characteristics......

Art
artesmith@earthlink.net