Bucking when engine braking

Technical Discussion on Pre-1973 Mustangs

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Shaunp
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Re: Bucking when engine braking

Post by Shaunp »

hybrid wrote:It should work on the 2-wire ford valves Shaun... they aren't a stepper motor.
They work against a spring. The higher the pulsewidth, the more they open.
Ok Ill take your word for it I assumed they were a 4 wire.
hybrid
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Re: Bucking when engine braking

Post by hybrid »

Yeah 4 wire will definitely be a stepper (2 wires per coil), but the ford stuff of that era is usually 2 wire.
lukep6470
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Re: Bucking when engine braking

Post by lukep6470 »

Result!!

I did a lap of the neighborhood this morning and took a data log.

So the car was bucking on overrun in the section of the ignition table where I had 17@1200rpm and 25@1500rpm.

I pulled 3 degrees out of each cell and the bucking went away completely in that area!!!

It now only bucks a little bit when it gets close to idle speed (Currently 850).

This stupid AOD only drops back when the engine speed gets below 1000. Might be time fof a tricked up governor.

Also my LC-1 wideband controller has packed it in :-(

I'm getting close to having my cam behave like a mild instead of mid range cam.
hybrid
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Re: Bucking when engine braking

Post by hybrid »

Nice one. My cam is 220/220 so might be why yours behaves a bit differently.
Is your valve body stock?

You should look at getting a modified one.. it really wakes these boxes up. Not cheap, but well worth the cash.
lukep6470
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Re: Bucking when engine braking

Post by lukep6470 »

hybrid wrote:Nice one. My cam is 220/220 so might be why yours behaves a bit differently.
Is your valve body stock?

You should look at getting a modified one.. it really wakes these boxes up. Not cheap, but well worth the cash.
I'm using a bosch 3 wire with the resistor circuit. It seems to do the job well.
Husky65
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Re: Bucking when engine braking

Post by Husky65 »

good stuff mate! Once I get the gear and learn how to tune my car(with help from you smart folk) I'll have to play with this.
hybrid
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Re: Bucking when engine braking

Post by hybrid »

lukep6470 wrote:
hybrid wrote:Nice one. My cam is 220/220 so might be why yours behaves a bit differently.
Is your valve body stock?

You should look at getting a modified one.. it really wakes these boxes up. Not cheap, but well worth the cash.
I'm using a bosch 3 wire with the resistor circuit. It seems to do the job well.
Yep me too.
Husky65
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Re: Bucking when engine braking

Post by Husky65 »

Just to close this off from my end. The ecu had the wrong injector and maf settings, and was running quite rich as a result. It also had EGR enabled, which apparently has a different spark table in use at different rpms which adds spark advance. I don't have EGR, so it was adjusting spark without actually having an egr or smog pump.
So once i changed those three settings, the bucking has gone. I can't put my finger on what exactly caused it, but I'd say a combination of all 3 most likely led to it.
Last edited by Husky65 on Wed Feb 01, 2017 8:10 am, edited 2 times in total.
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