L6 vs T2 Firing Order

[milkdud]

The T2 and T2x had a different firing order than the standard L6's of the time. (did the T1 have the unique order? as well?)

What did the new firing order accomplish for the motor? If it produced more power, why didn't the standard production engines adopt the firing order?

Thanks.
C

[FUJIMO]

The T2 and T2x had a different firing order than the standard L6's of the time. (did the T1 have the unique order? as well?)

What did the new firing order accomplish for the motor? If it produced more power, why didn't the standard production engines adopt the firing order?

Thanks.
C

T2x(rich luhrs) here on the board, will definately know everything about this...

[petlun]

The different firing order of the ordinary inlines (1-4-5-2-3-6) and the T2/T2X (1-6-2-4-3-5) have an impact on exhaust tuning and on the need of crankcase to crankcase sealing.

On a std I/L, cylinder 1, 3 and 5 dumps exhaust into a common (shared) plenum in the powerhead, as does 2, 4 and 6 into its own. The 1/3/5 are 120 deg. apart wich is necessary to achieve pulse tuning from a commom shared plenum and the engine in this respect acts as two 3 cylinder engines (as does a Merc V6 of today). However, as the cylinders 1/3/5 and 2/4/6 are spaced more widely apart than in an ordinary 3 cyl. engine, the peak tuning effect on the std inline comes in at a lower rpm (the exhaust pulses, traveling at a fairly constant sonic speed having a longer distance to travel than if the cylinders would have been packed side by side) wich is good for midrange power/torque.

On the T2/T2X on the other hand, cylinders 1, 2 and 3 are 120 deg. apart and dumps into a commom plenum in the block and 4, 5 and 6 dumps into another common plenum. As cylinders within each group are "siamezed" side by side, puls traveling distanses are shorter and peak tuning comes at a higher rpm, good on a race engine.

When it comes to crankcase sealing, on the std engines cylinders 1 and 2, 3 and 4 and 5 and 6 are 180 deg. apart (suction pulses for each carb comes twice per revolution, 180 deg. apart) wich means that crankcase to crankcase pressures for these cylinder pairs are as high as they could be, with piston in cyl. 1 being at TDC while no. 2 is at BDC. So between these pair of cylinders, the labyrinth seals in the std I/L are needed.

In the T2/T2X, cylinders are 120 deg apart at worst so crankcase to crankcase pressure difference are a bit lower than it is between the 1/2, 3/4 and 5/6 groups in the std I/L. Thus the T2/T2X engines could have real needle bearings also in these intermediate bearing positions. Good for a high winding race engine to be "fully jeweled"! And maybe idle-quality wasn´t a priority on the T2/T2X?

I hope milkdud this was readable and makes some sense, English not being my native language.

[milkdud]

This is making sense Petlun. I need to re-read it tonight when I get home to fully understand.

Thanks

[Mark75H]

The T-2's are really 2 3 cylinder motors stacked one on top of the other ... regular inline 6's are 2 3cylinders woven together

Each has its place ... the close 3 cylinder tuning works better at higher rpm, the more spread out cylinder spacing tuning works better on a pleasure/work boat motor that is pushing a heavier boat

[milkdud]

Thank you. This makes sense. I understood that both used 3x3 cylinders to create optimum tuning, but did not know why one was better than the other. MK75H and Petlun both described the distance apart from the pairs of 3 create different sweet spots for power. Closer + higher RPM Farther apart + lower rpm.

I am wondering how a 6 carb (t2) front would react on a standard 1500 block? Im assuming it would be beneficial, but lack what a true T2 could do because of the firing order.

Conrad

[Mark75H]

Correct ... it would be the original C-6 Merc from 1970-ish, about 165 hp


I think Merc's clue to the exhaust tuning was that they were getting 90hp+ out of experimental versions of the 650/700 triple using basically the same parts ... solution ... weld 2 650 cranks together

[hydroplay]

I'm not sure which came first here- the chicken or the egg. The 650/700 never seemed a real engineering priority but more of a step-sister to the 6 cylinder stuff. There were different cranks with reversed firing order for the trippple but I'm guessing the revised 6 came first. BTW, since Mark 75-H is into Formula E racing- the only successful 650/700 in Formula E hydro used the reverse firing order crank. It won several Nationals with 2 different drivers and was often accused of being one of the 3 cyl loop motor project.