Is the firing pattern of a flat-plane v8 different than a cross-plane v8?
While the firing of the cross-plane V8 is regular overall, the firing of each bank is not LRLLRLRR; this leads to the need to connect exhaust pipes between the two banks to design an optimal exhaust system.
The punctuation of:
“the firing of each bank is not LRLLRLRR”
Is confusing.
The firing order of the engine ** is* LRLLRLRR.* perhaps less so.
IIRC, ALL American V8s are cross-fire, but Ferrari makes flat-planes.
Since flat-planers have smaller counter-weights, do they inherently have the capacity to rev higher?
Reducing the moment of inertia with lighter counterweights allows the engine to accelerate faster and slow quicker. So aids acceleration and speeds and smooths shifting, but doesn’t necissarily increase the rev limit. a subjective term would be “responsivness.” The amount of energy stored in a flywheel is proportional to the square of the rpm, so this becomes much more important as red line is pushed.
A laundry list of things that DO help increase rev limit:
-A short stroke to keep peak piston speeds reasonable.
-A short and/or low mass valve train to avoid valve float. (overhead cams)
-Anti pump-up valve train, usually means solid lifters, shims or selective fit parts
rather than adjustment screws.
-Multiple valves per cylinder to reduce valve throw.
-Small diameter main and rod jurnals to keep surface speeds reasonable.
-light pistons and rods to reduce dynamic forces.
Those are things that let an engine wind without damaging itself. Many other features are needed to allow a high reving engine use that speed to advantage by making lots of HP.
I just came across this after hearing about it on Horsepower…one of the PowerBlock car shows on Spike tv…about the 4/7 swap; switching the firing pattern of number 4 and 7 cylinders.
http://www.holley.com/HolleyNews/article.asp?ID=37
Does that essentialy convert an american crossplane v8 into a flatplane?
Do V8’s fire at eights of a turn or pair firings at quarters of a turn?
A normal V8 engine has a distributor that turns at half the rate of the crank. So it takes 2 rotations of the crank to get 1 rotation of the distirbutor. put another way, a complete firing of all 8 cylinders occurs every 720 degrees of crank rotation. 720 deg /8=90 degrees between firing. We’re talking about 4 stroke engines so your answer is every 1/4 turn.
Thanks. Still, that makes two rotations for the 8 firings, right? so the firings are at 1/4 turn but they are not paired. What about V6’s?
Math is the same for any four stroke engine. 720 degrees divided by number of cylinders.
In this case 720/6 = 120 degrees. (this assumes an even fire V-6, there are some odd fire engines that go 90-150-90-150-90-150)
are firings ever paired in any kind of engine? (meaning, have two cylinders fire at the same time)
In automotive use the only thing I can think of would be a 4 cylinder 2-stroke engine. Other than that, I can’t think of any.
In motorcycle racing, some twins have been re-cammed to fire both cylinders at once. No more power, but the idea was that it was supposed to help the rear wheel break loose in a more predictable and/or controllable way. This is referred to as a “big bang” engine.
this thread is doing a great job of showing my ignorance of basic ICE mechanics (this from a fan of F1). How would that work if a two cylinder engine fires both at the same time?. The mental image I am getting is two elephant jumping at both sides of a see-saw at the same time. Nothing good can come out of that.