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ZX-4R engine animation

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4.6K views 14 replies 7 participants last post by  ithaca00  
#1 · (Edited)
EDIT: Final video here ZX-4R Engine Layout.mp4

To bridge the waiting time and because I love various engine layouts, I've taken the time to model the crank, pistons and con-rods of the ZX-4R. They are about 80-90% dimensionally accurate (except bore and stroke, which of course are correct as they are known). I've only worked from the parts catalogue and its low-res images (Revzilla). I can't even find real pictures of the parts online yet, but the point is not to be fully accurate, just that the size and layout is correct. The main engine modeled here really is very similar to the ZXR400, only major difference is the ZXR400 has the main cog that transfers the power directly integrated on the crank replacing one of the counter-weights, the ZX-4R has the cog at the end (which I didn't model because I want to focus just on the engine layout).

I've done the same for our Vitpilen 401 (same engine as Duke 390) 373cc single-cylinder as later I want to add our V2 (XB12R), L2 (Moster S4) and V4 (VFR 800) engines to have a visual comparison in the end (and a few larger 4-cylinders as well).

Here the short animation for the ZX-4R
EDIT: Removed, see final video above.

The still renders are taken from the identical angle, so they are to relative scale to each other for comparability.

ZX-4R:
Image


Vitpilen 401:
Image
 
#7 ·
Correct, but the inner two and outer two do not fire at the same time. I am just working on this animation showing the firing sequence to make that clear. Our "screamer" I4 fires in this order 1-2-4-3, symmetrically firing once every 180° of rotation, in contrast to the modern crossplane Yamahas as mentioned by @NGeese. While V4 bring advantages that slightly outweigh the screamer I4 as most agree (thus the dominance in MotoGP), the I4 is as smooth as it gets in first order balance, equal firing order, and the perceived high frequency sound when revving because the equal firing order sounds to our ears like a higher-pitched sound with shorter sound waves.

While the firing order is different (irrelevant for sound as long as the spacing is the same), the spacing is the same as the ZX-4R and I think this is the simplest common denominator showing how the sound is produced:

In contrast, the cross-plane firing order (loosely comparable to V4 and used by Yamaha in the R1 today) has the same number of in-line cylinders, but because the firing spacing is not equal, it sounds much deeper and growlier for lack of a better term than the screamer:

Incidentally, this is how the sound was digitally generated in old motorcycle racing games, just one simple beat in the right spacing makes all the difference.
 
#4 ·
psycline said:
The middle cylinder pair and outer pair fall and rise in unison. Interesting! Is this what makes the engine so smooth?
Click to expand...
Grabbing the popcorn as this should turn into an interesting discussion of motor dynamics including the counter balancer and piston/crank orientation. There are likely people here that recite more information about motors in their sleep than I would ever know.
 
#5 ·
psycline said:
The middle cylinder pair and outer pair fall and rise in unison. Interesting! Is this what makes the engine so smooth?
Click to expand...
Yes, conventional i4 engines like in our beloved 4RR have perfect primary balance while not having perfect secondary engine balance (not as noticeable on smaller engines). Resulting in very smooth revving engines.

The YouTube channel Driving 4 Answers (https://www.youtube.com/@d4a) has a number of very good explanation videos of what primary and secondary engine balance are, how they are treated, and what some manufactures have done to compromise engine balance for other gains (Yamaha Crossplane i4 for example).
 
#6 ·
NGeese said:
The YouTube channel Driving 4 Answers (https://www.youtube.com/@d4a) has a number of very good explanation videos of what primary and secondary engine balance are, how they are treated, and what some manufactures have done to compromise engine balance for other gains (Yamaha Crossplane i4 for example).
Click to expand...
Youtube keeps showing me d4a, but I'll be damned if it's ever shown me the crossplane i4 video. Something to watch tonight :D
 
#12 · (Edited)
And at 14,000 rpm that is 14,000 / 60s = 233.3 revolutions per second and 233.3 x 2 ignitions per 360° revolution = about 467 ignitions per second. Kinda hard to believe that but I think it checks out.

It makes you begin to understand things like valve overlap, physical limits of pistons accelerating and the challenge of squeezing in the air fuel mixture into the right place in correct quantity and ignite it early enough so that it actually burns well in such a tiny time window.
 
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