cylinder numbering on V8s

[BAR]

Having recently spent a few hours cleaning up the rocker covers and ignition leads, I went looking for the cylinder numbering sequence on my V8 motor.

Took a long time, so I have made this reference chart for Topklasse readers: print it out and keep it with your owners manual.

http://i428.photobucket.com/albums/qq6/BARTopkalsse/CylinderNumberingW116V8.jpg

 

[WGB]

An easy to use guide - thanks.

Bill

 

[Styria]

Thanks for that, Bar. Your thread brings up a point that has always puzzled me and even to this day I still don't understand certain matters, namely the sonorous and characteristic American V8 burble compared to the 'whatever' one associated with Mercedes V8's, with the possible exception of the 350 - they can sound quite nice.

Is it a question of the muffler system that creates the two different types of sound or, indeed, is it the firing order ? For instance, on the Rover V8's, and I suspect on most Yankee units, the order is 1-8-4-3-6-5-7-2 as compared to 1-5-4-8-6-3-7-2 for the MB unit and I am wondering if anyone could explain the reasons for the difference in the firing order between the two units.

Is it to do with the crankshaft configuaration - obviously, it has, but even on that score, I am curious why different engineering principles have been applied.Over to you guys. Regards Styria

 

[s class]

Styria, a significant proportion of the exhaust sound is caused by the valve lift durations, and more importantly, the valve overlap angles. Other issues like compression ratio play a role too.

Mercedes engines tradntionally have a small overlap angle - well much smaller than BMW's anyhow. As an example case, 80s and 90's BMW sixes sound obviously like 6 cyl engines, especially when fitted with a louder exhaust. MB sixes on the other hand are much more subdued.

As to v8 firing order, it has a lot to do with balancing mechanical moments on the crank shaft. The crank is subjected to mechanical pulses that come at different points along its lenght, depending which cylinder is firing. If cyl 1 or 5 fires, the pulse is at the front of the crank, whereas 2,3,6 or 7 will pulse the crank near its centre. These forces act to excite moments (bending actions) on the crank, and this is significant in respect to its inevitable resonant frequencies - if you get it wrong, the engine will have harshness, noise, and vibration at particular speeds. Remember the old Mitsubishi 2 litre four that had a counter balance shaft? - efforts to try and correct this kind of problem.

The Mercedes approach is logical - successive firings alternate between the cylinder banks, which helps to make the engine smoother. The Yank firing order on the other hand has 4 and 3, 6 and 5, 5 and 7 (??) 2 and 1 firing as same- sided pairs (not sure if your order is entirely correct). This will also contribute to a different exhaust note.

Whilst I can clearly see some advantages to the MB system, I cant immediately see why the yank system has attractions, apart from making the observation that those would tend to be lower revving pushrod units, and so it may be less critical.

 

[GreaseMonkey]

Certainly MB firing order will be smoother than the yank motors, but the latter are often made worse by people fitting dual exhausts set up for maximum noise effect - like two four cylinder motors - a lot of hoons around here think that is cool, not realising they are not getting the best efficiency out of the motor.
A factory exhaust system on a MB with it's crossover balance pipe, not only sounds smoother, it helps with exhaust gas evacuation when the vlave opens and hence more efficient.
The explanation above from s-class covers it as well as it can be explained, and that is why a V6 can never be as smooth as a V8 or straight 6.
Chris M.

 

[Styria]

Hi S-Class, thanks for that information. Incidentally, the Rover V8 figures I have quoted without double checking and it is some two to three years since I've been involved in having to check the firing order.

I have to admit to a distinct liking for the Yankee V8 - I mean, they can really sound glorious, with the right mufflers. The Statesman we have, with the Chevrolet 5.7 litre alloy V8 is virtually super quiet. You just can't hear it. I wonder if that has helped to put a few ponies to sleep ?

This is digressing somewhat - blipping the throttle. No, I'll start a new thread. It could well add to S-Class's explanations regarding stresses etc. Regards Styria

 

[Michel]

Hi S-Class, thanks for that information. Incidentally, the Rover V8 figures I have quoted without double checking and it is some two to three years since I've been involved in having to check the firing order.

I have to admit to a distinct liking for the Yankee V8 - I mean, they can really sound glorious, with the right mufflers. Styria

I have both engines.. Yankee and MB (I am talking large capacity) and the 6.9 sound is as pleasing as the 454 in my 62 wagon.
Exhaust, mufflers and resonnators play a big part...

But the heart of the matter (the big donk) is what makes it throb.....

 

[John S]

Do the US engines use the same cylinder numbering system as Mercedes? Different numbering system equals a different sequence.


(Some years ago, when I owned a ‘65 Chev, I knew but unfortunately can no longer remember.)

 

[Michel]

Do the US engines use the same cylinder numbering system as Mercedes? Different numbering system equals a different sequence.


(Some years ago, when I owned a ‘65 Chev, I knew but unfortunately can no longer remember.)

You mean firing sequence?

 

[Lukas]

Hi Michel,

I think John S means the actual numbers assigned to each cylinder (and I second the question).

I don't know how cylinders are numbered on engines, but from S Class' explaination I take it that, when standing at the front of the car looking at the engine:

• Cylinder #1 is at the front left
• Cylinder #2 is directly behind it
• Cylinder #4 is at the back left
• Cylinder #5 is at the front right
• Cylinder #8 is at the back right

This is of course for a longitudinally mounted V8 engine, things go all wierd for transverse.

If the Yanks use a different cylinder numbering method, then the firing order quoted for them might be with a reference baseline of that alternate numbering method, and would thus need to be converted.

Lukas

 

[Styria]

Hi Lukas, I am not having a go at you, but normally in MATHEMATICAL order, the two sides are assessed from the driver's seat - in other words, the left bank will always be left bank etc. - as I said, I am not having a shot at you.

When you relate all this to MB engines, your description and location of cylinders and numbers relating thereto are perfectly correct. However, different manufacturers have different methods.

You have already pointed out the MB sequence, as has BAR. However, for instance with Rover, right bank (FROM DRIVER'S SEAT) is 1, 3, 5, 7 and, of course, on the left bank, 2, 4, 6 and 8.

Now, I am going back at least thirty years, to my Jaguar days, and if I remember correctly, No. 1 cylinder was at the back and No. 6 at the front. Wise heads like JohnS and Grease Monkey might be able to verify this - I am speaking purely from memory - SUCH AS IT IS. Boom , Boom...Styria

Knocks on the head !

 

[TJ 450]

Yes and another peculiar example is the PRV V6 engine, where #1 is closest to the firewall on the left bank where the engine is mounted longitudinally.

Tim

 

[WGB]

Most engines are numbered by their Manufacturer according to the cylinder position in linear order starting from the front of the engine.

Most V-engines have two conrods sharing one big-end journal - but one cylinder is always ahead of the next in a V-engine and can be seen in the asymmetry between the two banks where one bank is always 1/2 a cylinder width in front of the opposite side.

Some started from the back - Jaguar being one of these.

I guess D-B simplified their system for the benefit of semi-trained mechanics or some other reason.

Bill