Backfire when you decerate? No... - Page 4 - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

S-eatin-grin · 10-10-2016, 06:40 PM

I had (and still do have) and M6. The way Ted (JRE) explained it to me was that the way the stock ECM is programmed there is a little squirt of fuel programmed into the exhaust stroke of the cycle. At higher RPM's it gets burned before reaching the exhaust, at lower RPM's it makes it to the exhaust before ignition where it then "pops" as a complete waste of fuel...unless you value the "pop". Eliminate the exhaust stroke squirt...and eliminate the "pop". Disclaimer...this is from memory 5 years ago I might not have said exactly what he said but it is the general version of it.

CamaroFred · 10-10-2016, 08:57 PM

An internal combustion engine is built on the premise that an explosion will push the piston down which compresses the connecting rod which passes on to spin crankshaft.

Deceleration is exactly the opposite. the crankshaft is pulling down and stretching the connecting rod and piston in way it was never meant to go.

Sure with the computer controlled technology we have it will put up with it, but it is far from ideal.

Moto-Mojo · 10-10-2016, 10:20 PM

Quote:

Originally Posted by CamaroFred

An internal combustion engine is built on the premise that an explosion will push the piston down which compresses the connecting rod which passes on to spin crankshaft.

Deceleration is exactly the opposite. the crankshaft is pulling down and stretching the connecting rod and piston in way it was never meant to go.

Sure with the computer controlled technology we have it will put up with it, but it is far from ideal.

Hard to believe that deceleration was never factored into the equation of what a piston and rod must do during its life cycle. Kind of Newton's Law - for every action...

And as far as that little "squirt" of gas we should tune out, what does that translate to over the course of a tank of fuel? I want pop-per-gallon stats!

Norm Peterson · 10-11-2016, 07:08 AM

Quote:

Originally Posted by CamaroFred

An internal combustion engine is built on the premise that an explosion will push the piston down which compresses the connecting rod which passes on to spin crankshaft.

Deceleration is exactly the opposite. the crankshaft is pulling down and stretching the connecting rod and piston in way it was never meant to go.

Stretching in a way it was never meant to go??? What do you think happens on the intake stroke even when you're accelerating?

On decel, with the engine being driven by the car's momentum, its main mission of making power to move the car is on hold. Instead of being a power-producer, it's temporarily become a power-absorber. Call this a convenient side effect for those times when more engine power is exactly what you don't want. At most, you only have to keep the engine from conking out. Which doesn't take any fueling or ignition at all if your fuel-cut-on-decel logic turns the fuel and spark back on at the right time/rpm level. Pretty hard to get this wrong enough for a racing environment for it to matter.

Never mind that you're conveniently ignoring the effect of inertia loading on the rods as the piston moves through TDC during the overlap phase even when it's in power-producing mode. The g's experienced by the piston and tensile loading on the rod are at their highest then, and the g's involved are not small numbers (well up in the thousands of g's, IIRC, got a spreadsheet app for this somewhere).

Norm

CamaroFred · 10-11-2016, 07:29 AM

Quote:

Originally Posted by Moto-Mojo

Hard to believe that deceleration was never factored into the equation of what a piston and rod must do during its life cycle. Kind of Newton's Law - for every action...

And as far as that little "squirt" of gas we should tune out, what does that translate to over the course of a tank of fuel? I want pop-per-gallon stats!

It's one thing if the reciprocating mass follows and another if you force it.
Did you ever own a mechanical watch and were warned never to set it back?

That squirt of fuel probably makes it easier on the parts causing at least some push on the piston.

For pop-per-gallon note that the American Le Mans Series (ALMS) lengthened their races from 3:30 to 3:45 so the fuel saving 10th place runner had to make another stop instead of winning.
So 15 minutes/tank.

frankwjr · 10-11-2016, 08:05 AM

Quote:

Originally Posted by CamaroFred

It's one thing if the reciprocating mass follows and another if you force it.
Did you ever own a mechanical watch and were warned never to set it back?

That squirt of fuel probably makes it easier on the parts causing at least some push on the piston.

For pop-per-gallon note that the American Le Mans Series (ALMS) lengthened their races from 3:30 to 3:45 so the fuel saving 10th place runner had to make another stop instead of winning.
So 15 minutes/tank.

On a motor gettin wat MPG? LULZ this is ONLY happening when car is left in gear in a decel envelope...I usually am poppin into neutral when coastin to a stop...heck I put it in neutral comin down the mountain on the interstate....rolls in neutral at 80...no probs...

And to a previous post about our cars decel pops soundin like a ricer,,,ROFL...anybody confusin the 2 needs to get their hearin checked...ain't no comparin the 2...

Motarded421 · 10-11-2016, 08:35 AM

Quote:

Originally Posted by frankwjr

On a motor gettin wat MPG? LULZ this is ONLY happening when car is left in gear in a decel envelope...I usually am poppin into neutral when coastin to a stop...heck I put it in neutral comin down the mountain on the interstate....rolls in neutral at 80...no probs...

And to a previous post about our cars decel pops soundin like a ricer,,,ROFL...anybody confusin the 2 needs to get their hearin checked...ain't no comparin the 2...

What is the purpose of doing that? You'd actually save fuel since the fuel flow is completely stopped when at 0% throttle and no load. Doesn't cause any additional wear and tear on the vehicle to let it engine brake (which is minimal in 6th gear anyways) going down a mountain....

LunarEclipse · 10-11-2016, 06:03 PM

Quote:

Originally Posted by URBAN LEGEND

The undisputed stock king of pop is the Jaguar F Type R.

YES this car is amazing, buddy of mine has one and sounds sick

Homeless Man · 10-11-2016, 09:02 PM

Quote:

Originally Posted by Motarded421

What is the purpose of doing that? You'd actually save fuel since the fuel flow is completely stopped when at 0% throttle and no load. Doesn't cause any additional wear and tear on the vehicle to let it engine brake (which is minimal in 6th gear anyways) going down a mountain....

I always get better MPG when I cruise in neutral on huge hills

Norm Peterson · 10-12-2016, 06:17 AM

Quote:

Originally Posted by frankwjr

heck I put it in neutral comin down the mountain on the interstate....rolls in neutral at 80...

An unwise technique for reasons not relevant to this discussion.

Norm

frankwjr · 10-12-2016, 08:49 AM

Quote:

Originally Posted by Norm Peterson

An unwise technique for reasons not relevant to this discussion.

Norm

hmmm. comin from a 'stang driver I'll leave that one alone....and your RELEVANT is IRRELEVANT to me sir!

arkentect · 10-12-2016, 09:06 AM

Love the way my v6 gurgles and pops on decel. Now I just need some Hi-flos to get her really goin

Norm Peterson · 10-12-2016, 10:03 AM

Quote:

Originally Posted by frankwjr

hmmm. comin from a 'stang driver I'll leave that one alone....and your RELEVANT is IRRELEVANT to me sir!

Don't judge us all by the moronic meme-inspiring driving of a few. Or underestimate the experience of others no matter what they might have chosen to drive.

Norm

Homeless Man · 10-12-2016, 01:48 PM

Quote:

Originally Posted by Norm Peterson

An unwise technique for reasons not relevant to this discussion.

Norm

How is this unwise?

10-12-2016, 09:06 AM	#54
arkentect Drives: 2010 Camaro SGM 1LT M6 Join Date: Jan 2015 Location: Rochester, NY Posts: 1,630	Love the way my v6 gurgles and pops on decel. Now I just need some Hi-flos to get her really goin __________________ Arkentect's Build Thread!! - UPSTATE C5 MEMBER 2010 SGM M6 1LT - SOLD Current - 2009 C6 Corvette Z51

10-10-2016, 06:40 PM	#43
S-eatin-grin Drives: 2013 2SS/RS AGM Join Date: Nov 2010 Location: WV Posts: 1,170 View My Garage	I had (and still do have) and M6. The way Ted (JRE) explained it to me was that the way the stock ECM is programmed there is a little squirt of fuel programmed into the exhaust stroke of the cycle. At higher RPM's it gets burned before reaching the exhaust, at lower RPM's it makes it to the exhaust before ignition where it then "pops" as a complete waste of fuel...unless you value the "pop". Eliminate the exhaust stroke squirt...and eliminate the "pop". Disclaimer...this is from memory 5 years ago I might not have said exactly what he said but it is the general version of it.

10-10-2016, 08:57 PM	#44
CamaroFred Drives: Miss Con Ception Join Date: Aug 2016 Location: Chicagoland Posts: 2,998	An internal combustion engine is built on the premise that an explosion will push the piston down which compresses the connecting rod which passes on to spin crankshaft. Deceleration is exactly the opposite. the crankshaft is pulling down and stretching the connecting rod and piston in way it was never meant to go. Sure with the computer controlled technology we have it will put up with it, but it is far from ideal.