Hi gang,

For those of you with experience with GM's LS-series engines, you know that the firing order is now 1-8-7-2-6-5-4-3, as opposed to the old 1-8-4-3-6-5-7-2 of previous GM V8 engines.

Does this change the sound of the engine or exhaust? I would think it has to.

My 5.7 Chrysler Hemi still fires on 18436572 and it has such a great sound. Fords always had some weird firing order that was different than the one used by GM and Chrysler. I always assumed that's why Ford V8s didn't sound as nice to me. (Then again, Oldsmobile V8s always sounded different than other GM V8s, and they all shared the same firing order.)

I read that the reason GM changed the firing order was to match other manufacturers V8s, but why would that matter?

Thoughts? Feedback?

This is the first time I've read about this.. I doubt that it's just to mimic other manufacturers, it needs to have some sort of advantage over the older firing order, I'm thinking something other then just sound. Someone with a degree in thermodynamics could be able to help.

its easier to have a fuel management/cut-off system with that firing order, since its the middle four cylinders that get cut-off.

Hmmm... I'm having trouble swallowing that. My Chrysler has cylinder deactivation and it uses 1-8-4-3-6-5-7-2.

And thermodynamically, the difference in firing order couldn't amount to a hill of beans, since we're talking milliseconds in between each cylinder firing.

Any other thoughts?

Honestly, I would resort to the advanced technical forum on LS1tech, I'm sure the geniuses there would know whatsup.

Looking at it, I think the new order might be a touch smoother without a cylinder deactivation system. But I think that difference would be negligible since it isn't a flat crank. On the surface it also looks like the scavenging would be more efficient for the individual banks of cylinders. But I really have no idea, just opinion.

I think the Fords were odd because of the way the cylinders are numbered not fired. Ford counts from front to back and not across the V. A link to popular V8 firing orders, shows the difference between the Ford and everybody else.
http://boxwrench.net/specs_index.htm

Let me refer you to Hot Rod magazine, March 2006, pp 106-110.


Performing a 4/7 swap of firing order on a stock Chevy 492 block is good for 10-12 hp, and while building an engine only costs $30. Swapping 3 and 2 at the same time result\d in the Corvette (C) firing order as in an LS1. Smoother running, less journal loading, quoting from teh article, Bill Compton, GM GenIII crank guru "Since the G3 engine was a clean slate project, each group looked at things they could change to optimize the performance of teh small block. Although we did not have an issue with crankshaft loading on the older V8s, there was room for improvement in the area of distributing the peak firing loads among the five crankshaft journals. Analysis showed that main 4 had peak loads significantly higher than main 2. By changing the firing order, the peak loading on main 4 was reduced and teh peak loading on main 2 went up. Overall, the loading through the mains was much better balanced. By improving the load balance across the crank, we created a better balanced oil film interface across the crank. The valvetrain group simply changed the cam lobe timing to work with the new crank firing order."

Because Ford numbers their cylinders different from GM, but if you renumber a FOrd 351 or late model 5.0 as if it were a GM, then you end up with exactly the same firing order as the LS1. Another interesting tidbit, NASCAR requires all engines currently to use the old GM firing order, even in Fords.

wow - very interesting achieftain. good find

Actually, YES, Firing order DOES have an affect on sound.

When GM developed this engine, back in the early 90’s D.O.D./AFM was just a far out idea to they were going to re-invent and bring to market sometime down the road. So their choice in firing order on this engine had little to do with it.

It is primarily done in an effort to smoothen the rotation of the motor and in the process, allows for a cleaner, meaner sound to it and doesn’t have the booming, hollow tone to it that previous generation SBC’s had. Not that previous generation SBC’s sounded bad mind you, they sound great in their own way. But this was an easier, less complicated method than adding items such as a counter rotating balance shaft like was employed on many 4.3L V6’s (which is an SBC with 2 cylinders chopped off), or other means to smoothen the engine.