Coworker and I had a discussion yesterday about how Supra engines fire. I was under the impression that cylinders fire in pairs, i.e. 1 and 6 fire at the same time, 2 and 5, 3 and 4... He says that while cylinder 1 is firing, cylinder 6 is exhausting. Is this how our engines are? I tried looking into it a bit yesterday but couldn't come up with any good info with Google.
Supra engines, are they even-firing or odd-firing?
- Thread starter te72
- Start date
While 1 is on compressin 6 is on exhaust stroke. Wasted spark both 1/6 plugs are firing. Every 1/3 of crank rotation a cylinder fires.
hvyman;1850346 said:
QFT
I didn't check if the firing order is the same, but watch a pair of pistons and notice the alternating power strokes:
[video=youtube;NNqmNqaZlKA]http://www.youtube.com/watch?v=NNqmNqaZlKA[/video]
LMAO very few if any car engines are "Big Bang" (2 cylinders fire at the same time) only ones I've ever seen use this were the GP bikes when they went 4 stroke.
Being old I'm a long way from having seen everything... they keep making new things for me to look atAnother MkIII;1850463 said:
Yes, but much closer than I am, lolIJ.;1850468 said:Being old I'm a long way from having seen everything... they keep making new things for me to look at
-AM3
Technically, this does depend of your 7M is a GE or GTE.
The GE uses a distributor, so there is no waste spark, it's a straightforward 1-5-3-6-2-4 pattern.
The GTE uses the distributorless ignition, and fires in pairs. Still, the fact that the cams can be swapped indicates that the firing order is exactly the same. So each cylinder will have the plug fire as it approaches TDC. Of each pair, 1 will be at the end of compression, and 1 will be at the end of exhaust.
The GE uses a distributor, so there is no waste spark, it's a straightforward 1-5-3-6-2-4 pattern.
The GTE uses the distributorless ignition, and fires in pairs. Still, the fact that the cams can be swapped indicates that the firing order is exactly the same. So each cylinder will have the plug fire as it approaches TDC. Of each pair, 1 will be at the end of compression, and 1 will be at the end of exhaust.
I did a little more research on this last night, some rather interesting reading here:
http://www.epi-eng.com/piston_engine_technology/torsional_excitation_from_piston_engines.htm
Anyway, thanks for clearing that up guys. It would seem that odd firing engines are uncommon, and the even/odd fire thing has more to do with timing than how I initially understood it.
Now for the fun hypothetical question: How would an inline 6 behave if the cylinders were fired two at a time? I would think the torque output would be pretty awesome, but when 1/6 fired, you would put a lot of stress on the center of the crank...
http://www.epi-eng.com/piston_engine_technology/torsional_excitation_from_piston_engines.htm
Anyway, thanks for clearing that up guys. It would seem that odd firing engines are uncommon, and the even/odd fire thing has more to do with timing than how I initially understood it.
Now for the fun hypothetical question: How would an inline 6 behave if the cylinders were fired two at a time? I would think the torque output would be pretty awesome, but when 1/6 fired, you would put a lot of stress on the center of the crank...
Yeah, I was wondering why what you were getting at had to do with even/odd firing. I own an odd firing engine btw. The first generation PRV 6 is such an animal. It comes from it being a V8 with two cylinders loped off. You can tell distributor equipped odd firing engines by the uneven plug wire spacing on the cap.
Sorry if it was unclear in how I worded the first post. I've heard of a few of those V6 engines. It seems that they might be the only "traditional" engine layouts that are odd firing. Seem like they're prone to very high levels of torque, but not very smooth running, from what I was reading.jetjock;1850664 said:
How do you like it?
^ It does. It also doesn't idle very smoothly. No surprise there. French built it is. Ah well, you know that old joke about how in Hell the French are the engineers...
And to make matters worse they rotate at 2x crank speed and only have a plain journal bearing at each end of the shaft.
Reminds me of the V4 in the Sonett III I owned many years ago... It had a balance shaft, though it ran at crank speed. Not a bad little engine.