spotch

I recently saw the .pdf file where Realtime Racing was requesting to put the tsx engine in the rsx race car and it raised some questions in me.... On the request form it said that the had had 8 k20 failures in the previous race season and 0 tsx engine failures. This struck me as odd because even though you'd have to rev the tsx's engine to lower rpm's to get the same power, it's got a worse rod/stroke ratio (doesn't it?) and a *much* longer stroke, so I would assume at 6000-7000rpm I would assume it has more stress on it than a k20 would have at 7000-8000rpm, right? Well apparently I was wrong, but why? Did honda do something different with the k24 or what? Is the rod/stroke ratio better than I'm assuming it is or what? I just don't get how an engine with this long a stroke can handle high revs as reliably as it does, basically.

moda_way

Well, I can tell you that the K20s and the K24s are nothing like their stock counterparts. First of all they aren't running our ECUs at all. Next, they are running very high compression ratios on their motors. When you take all the things into consideration, they were probably having to do so much to the K20 motors to keep them competitive that they lost a lot of longetivity out of them. When they ran the ITRs years back, the motors needed teardown after 40hrs.

spotch

I assumed they were pretty heavily modified but even heavy modifications aside the simple math that (according to this article below, at least) a k24 at 6900rpm has higher piston speeds than a k20 at 7900rpm, So if you figure they were only revving the cars to the stock limiters the k24 has higher piston speeds and I would assume higher stresses from it, not to mention they probably revved them both higher than the stock limits and it seems like the higher you go in each the stresses pile on the k24 quicker than the k20. So maybe they were shifting the k20 at like 10,000rpm and the 24 at only 8000 or so? I dunno.


EDIT: Has anyone ever heard of a tsx owner spinning a bearing or snapping a rod or anything from 7000+ rpm revving? I haven't ever seen anything about it but that's almost suprising with hondata'd ones running to 7500~ rpm. I remember reading something about the tsx's bearing surfaces being micropolished, I guess that would help prevent any failures quite a bit.

spotch

oh this is that thread I was talking about with the piston speeds...

https://acurazine.com/forums/showthread.php?t=14084

moda_way

Bottom ends on the K20 and K24 are the same, it is the head and the piston rod length that are different (to my understanding). I personally haven't heard of any failures that you are asking about.

As for shift points, I'm sure the K20s were shift further in the rev band than the K24s. There is one common fact amongst all the racing engines..... heat. Keeping a motor within the right temp range makes all the difference.

FYI, RTR was racing the K24 motor in the RSX all last year. I was talking with Eric Curran and he said that he liked the K24. I replied, "Don't you mean the K20?" He said, "Nope, we're running the K24s now." Dan Martin and a few others were there when he said at Mid-Ohio.... early in the race season. Additionally, the RTR TSXs and RSX were all running the RSX throttle body (bored out of course) since it wasn't a DBW module. I pulled that part number of there VTC sheets.

moda_way

Yeah, its pretty well known that the TSX has a faster piston speed. Someone actually compared the piston speed with other Honda (S2000, etc). As I recall, the S2k was just very slightly faster.

afici0nad0

^

you referring to this thread re: piston speed?

https://acurazine.com/forums/showthr...t=piston+speed

moda_way

That's the one!

sauceman

When I spoke with the RTR boys in Mosport last fall, one of the things a tech mentionned was that the K24's reliability greatly depended upon the pistons they were using. A pretty lightweight type of piston would last them only 4 races, while a heavier one would do over 10 races. I guess the same could be said of the K20s.

BTW, I do remember the guy mentionning me then that they were revving the K24 to 7800rpm, and that he couldn't imagine the engine lasting a single race at 8500rpm.

moda_way

Well, considering they aren't running anymore K20s speaks volumes for what they are doing to the K24s... Almost makes sense... why would you have 2 different motors on your team when you can go to one and have quite a few different setups going to see what works best.

spotch

Interesting that they were stopping at 7800rpm, that's a great tidbit of info! I wonder how high they were revving the k20's when they were having all those failures...

aaronng

Actually, the K24A has a shorter rod than the K20A. The crank also determines the displacement.