Team Camaro Tech banner

Firing order and exhaust note...

5K views 28 replies 9 participants last post by  Vintage 68 
#1 ·
What's the physical difference in firing order between the Mustang and the Chevy that would cause the difference in exhaust sound?
 
#2 ·
Re: I have a General question about cylinder heads.

The timing of the sound pulses and, of course, exhaust system and internal muffler design, i.e., sound chamber design, Helmholz(?) design. Unless I'm in left field, Professor?
 
#3 ·
Re: I have a General question about cylinder heads.

I would agree that the exhaust system design tailors the sound, as well as the cam timing, etc., my question was in regards to the firing order proper. It seems to me that the sound pulses emit from the engine in the same order and timing from a 5.0 Mustang as they do from an SBC, basically a RLLRLRRL sequence.
 
#5 · (Edited)
Re: I have a General question about cylinder heads.

... Still thinking............
It's a tough one to get your head around :yes:
But, if you've ever heard one of those older experimental "180deg"* SBC's barking through a set of headers as it made a pass you'll never forget how just changing the firing order can radically change the exhaust note.

* = not sure if anyone still does this or not, it was 'sorta' popular with several engine builders in the 70's. It phased the cyclinders to fire in the order they are at 180 to each othe, rather than the slightly out-of-phase sequence GM engineered - "supposed" to add a small amount of HP at top end... my one try with it was a bust - but a cam grinder made some money.
 
#6 ·
Re: I have a General question about cylinder heads.

While the firing order is different between chevy and ford, don't they also number thier cylinders differently?

Chevy Ford
Engine Front
1 2 1 5
3 4 2 6
5 6 3 7
7 8 4 8

I thought I read somewhere that on the new vette's the firing order changed to reduce crank loading (4/7 swap), but ends up firing the cylinders in the same sequence as ford if you number the cylinders the same.
 
#8 ·
Re: I have a General question about cylinder heads.

While the firing order is different between chevy and ford, don't they also number thier cylinders differently?

Chevy Ford
Engine Front
1 2 1 5
3 4 2 6
5 6 3 7
7 8 4 8

I thought I read somewhere that on the new vette's the firing order changed to reduce crank loading (4/7 swap), but ends up firing the cylinders in the same sequence as ford if you number the cylinders the same.
Yes, Ford does number different, but Ford has #1 on Pass side front.
Ford -front
5 1
6 2
7 3
8 4

But as shown by my earlier post, "Still thinkin'" I've taken GM #1 cyl and placed it after #2 (see the firing order?) and the result is the same = both are a match.
 
#12 · (Edited)
I have thought about this today as I drove my tractor around. Just a couple of things to consider.

Personally, at the dragstrips with cars with no mufflers, I have often thought I noticed a difference in the sound of chevy and ford engines of somewhat comparable size and power. I have tried to convince myself that this difference I am noticing is purely anecdotal. Maybe it is anecdotal, maybe not. Like most here I am a bowtie fan and thus I am biased.

I will list the firing of each engine to see if there is a pattern. But first we need to renumber the cylinders so that we are comparing apples to apples.

For simplicity I will use the sbc/bbc pattern to label the cylinders in both engines, which willindicate numbers 1-3-5-7 on the driver side, and 2-4-6-8 on the opposite side. So forget about the order that Ford used to number their cylinders. The factory numbers are just for identification. What we are after,imo, is if there is a difference in the firing of consecutive cylinders in each bank. AND THERE IS!!

I will use 8 revolutions for each engine as an illustration (2880* cranktrain revolution total), which means there will be 4 fires in each cylinder for this experiment.There is 90* of cranktrain revolution per fire. I will start with cylinder number 1, which is identified the same by both companies (8 is the only other cylinder that fires in the same actual order for the trivia buffs)

Chevy LRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLR

Ford LLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRR

We see that the driver's side bank fires three consecutive times in the Ford in 720* of cranktrain rotation. The Chevy never does this. The right bank of the Ford has 2 cylinders that fire consecutively twice in each 720* of cranktrain rotation, the Chevy fires a single cylinder in the right bank twice per 720*, and fires 2 consecutive cylinders in the right bank once per 720*.

If there is actually a difference in the sound of the exhaust in these engines, this is the likely cause of the difference. And I think Occam would approve :)

This was quite a mind bending effort. I think it is only fair as compensation for such effort that someone rewards me with a numbers matching '69 pace car in immaculate condition :).
 
#13 · (Edited)
I have thought about this today as I drove my tractor around. ...

Chevy LRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLR

Ford LLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRR

If there is actually a difference in the sound of the exhaust in these engines, this is likely the difference. :yes:

This was quite a mind bending effort. I think it is only fair as compensation for such effort that someone rewards me with a numbers matching '69 pace car in immaculate condition :).
So, now close you eyes and ponder what a SBC that fires LRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLRLR ... sounds like :thumbsup:
That's why those old "180's" sounded so weird :yes:

You need to pay the taxes and a 'handling charge' on the 69-pacer you've won - so just send me a Western Union money transfer for $120,000 and I'll see that you car is released from the prize vault and shipped directly to you - we don't need your address, it's on file l:)
 
#16 ·
I don't see where you get three in a row from Ford. A Ford has the #1, 2, 3 and 4 cylinders on the right (passenger) side, Chevy has #2, 4, 6 and 8 on the passenger side. Your summary:

Chevy LRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLR RLRLLRLRRLRLLR

Ford LLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLLLRRLRRLL LRRLRRLLLRRLRR


Chevy firing order is 1-8-4-3-6-5-7-2
Chevy: 1(L) 8(R) 4(R) 3(L) 6(R) 5(L) 7(L) 2(R) 1(L) 8(R) 4(R) 3(L) 6(R) 5(L) 7(L) 2(R)
That's LRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLR
2 in a row from either side.

Ford firing order is 1-3-7-2-6-5-4-8
Ford: 1(R) 3(R) 7(L) 2(R) 6(L) 5(L) 4(R) 8(L) 1(R) 3(R) 7(L) 2(R) 6(L) 5(L) 4(R) 8(L)
That's RRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRLRRLRLLRL
2 in a row from either side.

The exact same LRRLRLLR pattern exists in each firing order.
 
#20 ·
The exact same LRRLRLLR pattern exists in each firing order.
Exactly! This was the info in my two deleted posts. The same pattern exists.

So, as I am corrected, my bad, the exhaust sound pulses are the same, or at least the rhythm is the same.

Since both engines displace the same volume, and for this science experiment, have the same stock characteristics, carb, head volumes, etc., I would suggest its the exhaust design making the difference in the brands.

And yes, 180° headers have a definite sound.
 
#21 ·
Looks like Ononova and Everett are correct in the firing order of the two engines.

So I lose out on a 69 pace car.

But....if there is a difference in the exhaust note due to the firing order or anything else there is a logical answer for it.

Perhaps the order in which the cylinders fire creates a scavenging effect that creates a difference. Or, perhaps there is no difference at all.
 
#26 ·
There is a guy that runs a bracket car locally that has a sbc, good running car (high 5's in the 1/8) that a friend says has NASCAR headers on it...thing sounds like a 6 cyl. I just wonder if it is a 180* motor....it really doesn't sound like a NASCAR engine to me.


On another note......wasn't the Offy 4 cyl that was raced for a couple decades at Indy a 180* engine?
 
#27 ·
All 4-cylinder engines would have exhaust pulses 180° apart. Put them in a single collector and they'll sound like half a set of 180° V-8 headers.
 
#29 ·
Boy, you can't get 'nuttin by Dave anymore :D
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top