Like I was saying...
Need to get my butt up to Redding or Eureka more often.

 

I would be curious to see the BP motor on that chart

 

Stock 1.8 with 85mm stroke would be just shy of 20 m/s piston speed at 7000rpm. So fairly tame piston speeds, but the BP is obviously not known as a high strung engine. I would say that low piston speed contributes to why the BP motors, in basically stock form, last forever as a track motor because the bottom end isnt really being stressed to much.

8800 rpm would be just shy of 25m/s...

The valve train on a BP is likely the limiting factor.

 

Thank you for that information.

 

I didn't include the Miata engines because they're not really even in the ballpark. The BP engine is notoriously rev-hating; I added in the B6 since some people go on and on about how it's much happier to rev. Looking at the numbers, the piston speeds probably don't have anything to do with that. They're also 80s technology. I did run the S14 numbers (OG BMW M3 engine), but it was unremarkable now - at 84mm stroke pretty similar to the B6 at 83.6mm. That was a hot, high-revving engine back when the Miata was new.

The data I'm choosing to show here is really, really biased. From the charts I haven't included, I think many manufacturers use a 20m/s redline, then we see the 24-25m/s. I discounted any engine that redlined at 20m/s and I focused on stuff built in this millennium. Biased.

@sonofthehill now that I'm awake and actually using my brain, what kind of engines were your "old school" engine builders building? Bike stuff? One pass down the strip and then rebuild it? And I agree on the 2L rule...

 

So... Believe it or not, I used to autocross . Back a millenia ago, the hot ticket, before the Miata existed, was a Toyota Corolla. Where do you think the FRS/BRZ/86's come from? The early Corollas were RWD and came with a 1.6 pushrod motor. The JDM version came with a DOHC 8 valve head, twin sides, and a nice cast 4 into 2 exhaust manifold. In 1980, our BP's are actually 70's tech, the Corolla came with a 1.8, basically a stroked version of the 1.6. The 2t and 3t were the small and large pushrod motors respectively. The 2tg was the JDM version. The thing to do was slap the 2tg head on a 3t block. Those 3tg's would run 8500 no problem for years with an accusump, also old tech. There was one guy with a red 74 that kept the 1.6 block and supposedly could run 10,000 rpm. These were nice relatively short stroke and big bore motors, definitely took some head work to get them there.
But yeah, they would build bike motors too, early Hondas, Datsuns, but the Corollas were king. They were all scared of rotaries.

 

I love the knowledge base here. And it used to be even better.

:sadkitten:

 

It’s late and I’m having a week, but just to cause more ruckus:

Those 2T engines with the 70mm stroke (1.6L) wouldn’t reach 25m/s until 10,700rpm.

 

I'd cause even more nerdy spreadsheet ruckus if I brought up attempting to calculate second-order vibrations at high RPM in excel caused by the rod ratio, piston mass, wrist pin mass, and small end of rod mass that each of these engines uses...

Saving the formula-ridden spreadsheet struggle, you'd find long rod ratio engines like the F20C and MZR 2.0L are both VERY well suited to high RPM performance (giving up low-end TQ to do so). Not needing balance shafts while also not rattling themselves to death on the top end of the powerband is neat for them both.... You'd also find the K24A2 and MZR 2.5L to have rather small rod ratios, and the feedback of them being paint can rattler engines with balance shafts deleted (*ahem nearly every kmiata ever ahem*) showcases the math checking out.

 

I saw a reel or something showing the Cosworth CA v8 engine revving out to 20k rpm last night. If I found the right data, it's something like a 98mm bore, 40mm stroke. That puts it at 26.6m/s MPS. So it's not like even the fanciest, most balanced-est engines are violating the laws of physics. Much.


Edited to add:

I'd love to be able to do some of those 2nd order vibration calculations. But KISS - the MPS alone shows that we're really pushing these engines to the limit with the rev limiters we've been using.

 

So I asked some of the K24 swapped folks, and one civic revs to 8500. The crazy boosted MR2 supposedly revs to 10,000, but that is hearsay, need to confirm with the actual driver. Pretty sure they are able to retain the balance system.

 

Yikes with the piston speeds. I'm going to assume that the rods and pistons are not stock, hopefully bringing down the rotating mass and going down the 2nd-order vibrations rabbit hole that Padlock mentioned.

Now, regarding the balance system... I read somewhere in a single post in a random internet forum that the balance shafts are primarily intended to address low RPM vibrations. Because it's on the internet it must be true, but I'd like to learn a little bit more about balance shafts.

Actually, no. At this point I've set my redline to 7600 and I want to focus on other things, like driving the car. Or having it last more than one season without an engine-out event. Sigh.

ETA - I'll be at Sonoma with NASA again this weekend @sonofthehill if you're in the area and want to say hi.

 

This is what I did, and I have yet to regret it.

 

 

Sorry I missed you Baron! I have been redoing one of my showers, was working on it all weekend, just finished today.

 

That is impressive. At least your pan looks salvageable?

 

There is major damage to the oil pan. It's going to be a job.

 

 

Is the only damage on the flat bit there? Think you'll be able to clean it and weld it up? If so that seems pretty best case as far as pan damage goes.

 

There was hit on the flange. It's not totally flat along there. I'll see if I can make it better. RTV will fill it. Otherwise, I welded up the holes.