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      02-08-2013, 12:55 PM   #1
RingMeister01
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Engine Firing Order Factor?

Technical question regarding the effect of different cylinder firing order.

Its obvious that (for example) the BMW S65 has a different firing order than the Mercedes M156 or anyother V8 for this matter. Formula One teams go as far as recording the exhaust sound of competing teams using super sensitive equipment, in order to firgure the engines firing order. Some factories, such as Lamborghini, pride the firing order enough to stamp it on the engine cover. My question is; how do different firing orders effect performance and why do the factories choose the appropriate combination.

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      02-08-2013, 02:04 PM   #2
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First thing that's important is that say for instance the S65 and most other V8's have cross-plane cranks, versus the F1 and most other exotics have flat plane cranks, so that in itself affects the firing order.

Also, you have to consider the cylinder numbering can be different from brand to brand. For instance, GM has one bank be the "odd" cylinders, versus ford has one bank be 1-4 and the other be 5-8.. In other words, on a GM V8, the drivers side bank are cylinders 1,3,5,7 and the pass side is 2,4,6,8. On a ford, the drivers side bank is 1,2,3,4 and the pass side is 5,6,7,8.

The firing order has an affect on how smooth the engine operates, the important part is that one cylinder fires every 90, so however you accomplish that is really all that matters.. The major benefit I could see is for exhaust scavenging.

Obviously exhaust scavenging isn't as important on a boosted engine versus a N/A engine, but in F1 even 5-10HP can make a big difference at that level of performance. For a street car, I don't think it matters.
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      02-08-2013, 04:56 PM   #3
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Quote:
Originally Posted by elwesso View Post
First thing that's important is that say for instance the S65 and most other V8's have cross-plane cranks, versus the F1 and most other exotics have flat plane cranks, so that in itself affects the firing order.

Also, you have to consider the cylinder numbering can be different from brand to brand. For instance, GM has one bank be the "odd" cylinders, versus ford has one bank be 1-4 and the other be 5-8.. In other words, on a GM V8, the drivers side bank are cylinders 1,3,5,7 and the pass side is 2,4,6,8. On a ford, the drivers side bank is 1,2,3,4 and the pass side is 5,6,7,8.

The firing order has an affect on how smooth the engine operates, the important part is that one cylinder fires every 90, so however you accomplish that is really all that matters.. The major benefit I could see is for exhaust scavenging.

Obviously exhaust scavenging isn't as important on a boosted engine versus a N/A engine, but in F1 even 5-10HP can make a big difference at that level of performance. For a street car, I don't think it matters.

Thanks for the info! So firing order relates to the balance of horsepower, torque, efficiency and smooth operation. I suppose one firing order does a better job at a specific task than the other and its the decision of the engineer to assign this combination for that tasks success.
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