THEhomelessONE

I've been doing a ton of reading on what kind of compression I need and what stage cams. A common thing I'm seeing is even folks with stage 2 cams and upgraded valvetrain cut their dyno runs right at 8k even though power is still climbing?

THEhomelessONE

TTTits

Aradin

Do you have any specific engines you're talking about? I'm assuming you're talking about H series since you're posting in the Prelude subforum so I'll just post some general info. As the old saying goes, just because you can doesn't mean you should. RPM capability isn't strictly related to the cylinder head and valvetrain. The bottom end also plays a huge factor in engine efficiency at high rpm and the ability to handle it safely. In the case of stock bottom ends it's more than likely cut short for a degree of safety.

The factory rods and bearings can only take so much abuse and RPM. In your typical NA Honda engine the connecting rods will see the most stress on the exhaust stroke. The forces inside the engine are literally trying to pull the rod in half(this is when they are at their weakest, connecting rods are much stronger in compression than tension) and the forces that cause this increase exponentially with RPM. Engine geometry, pistons speeds, piston design, bearing clearances, etc etc will all play factors in the amount of RPM you can safely turn. A long stroke engine like the H23A(95mm) will be less likely to last very long at super high RPM than say an F20B(88mm). This is because in the H23A the piston speeds reach much higher speeds much earlier which compounds the effect I talked about above with the rods being in tension. The rod angle will also be more severe in the H23A and cause more side loading on the piston skirts/sleeves, etc etc. Long stroke engines are also less efficient at high rpm than a similar, shorter stroke engine. In direct comparison the F20B has much longer rods and a shorter stroke so the the rod angles are less severe, pistons speeds are lower, etc which all results in a much less stressed engine across the board. That's why you see F20Bs going to 9500RPM on a stock bottom end with just valvetrain and cams, whereas something like an H23A or H22 likely wouldn't make it anywhere near that far before having a catastrophic failure of some kind.

If you're asking about more specific setups that are built or whatever, you'll have to ask the engine builder, tuner, or owner of whatever builds you're looking at.

TimiK

usually people dont bother to get that high comp pistons with h22 (or rods etc since its NA setup) since you need to sleeve the block for them so setups stop to make more after 7500rpm

those things cost a ton of money and gains are not that high with H serie

THEhomelessONE

Thanks for the help guys. Figured since they're inline engines with lower reciprocating weights rod stroke ratios weren't as critical as say an old v8. A b16 would have to spin 3k higher rpm to make the same power as an h22 equally modified. Not sure how happy b16's are spinning to 11k lol. But yes sorry it's an h22a1 from a 94 prelude I'm planning to swap into an 89 crx. Not a daily, just something quick when I have some free time and a few track days.

Going to brainstorm some more but I think I'll go with type S pistons, thin head gasket, upgraded valvetrain, maybe flat faced valves and a milder cam. Pro1 maybe pro2. Don't see a point in the stage 3 and higher cams if the engine wants to grenade before it can utilize the extra duration. Maybe a 5.13 FD to get some extra pep.

Seems like building a lightweight balanced forged rotating assembly just to spin 9k or 10k isn't worth it then correct? I don't want to rebuild the thing every 20k miles. Sorry for all the what if style questions. I'm right at that point in a build where I can cut my losses and not lose anything. Been there done that, not fun.

THEhomelessONE

I just looked up some rod stroke comparisons and the b18c5 is the same as the h22a1. My good friend had an ITR that we would regularly spin to 9200 I believe. Maybe once every year and a half or two we'd toss in some rod bearings and do it again. Never any smoke or low compression readings. He ended up getting tired of the engine and was ready for a JDM K20A swap. Late in the night in "Mexico" he told me to blow the engine lol...too many beers and a bad night of racing. I had that thing pegged at the limiter in 5th going over 150mph for 5 to 7 minutes? Two weeks later, rod knock again. Throw some new bearings and all is well. He was very meticulous about maintenance and using high quality parts, fluids etc. At the same time, a friend of mine would dog his poor gsr, driving it hard while the oil wasn't fully warmed up, late oil changes, crap oil, bouncing off the limiter etc. The rings would smoke but it never broke down.

Now, I really think 9k isn't asking too much with the hell we gave the C5. I know for a fact they need better valvetrain (from what the race shop said) but that's needed when throwing cams in anyway. A shop I spoke to really wanted me to go with a jdm h23v but ref said he won't pass it. But the guys said they'd regularly hit 10k on the stock bottom end, I told them that sounds too good to be true and they said they've been doing it for a while now. I looked up the crank differences and it's a good 6lbs lighter than the h22 cranks and their rod bolts aren't pressed in. I'm reading one thing online and hearing another elsewhere. I'm new to this stuff but I think I'd be safe if I went with some forged rods, lightened crank and a balanced assembly.

One of the main reasons I got the CRX was its light weight and I'd like to keep up with my cousins 135i we built. He's fully built, turbos and all. 450whp on a daily tune on crap 91. 500whp on 91 and with port injection 600whp on e85/meth. I don't stand a chance once he goes to e85 but if I can get in the 260+whp range and shed a bit more weight I should be fine. I can't go FI and don't want to run nitrous. I may just say to hell with it and swap in a h23v after I get it ref'd. I can get one locally for less than $700 I think.

TimiK

H22s hardly make more power after 8000 so makes no sense to make insane rpm goals

K swaps are different thing and you could say it would be a lot easier to build K engine - youll get a lot more hp for your cash, time and work

other than K serie wont be quick NA

Aradin

I wouldn't worry about an RPM figure. The build you have laid out here would be stout and properly fast in a light chassis and should rev to ~8500 at least with a good header and intake combo. Just bump the compression up as much as you can, valvetrain/cams, shorter gears, and let it eat.

Now the bold part I don't believe at all. Yes the crank is lighter and the pistons are strutted too. Honda made those changes to ensure the engine would survive to only ~6900rpm for it's original intended purpose. The rod bolts are a moot point because all the later model H/F series came with them standard instead of the pressed-in stud style setup the early engines had. Even if somebody was turning a stock bottom end H23A to 10k it would be will beyond it's efficiency range, if it even survived. The pistons in those engines are notorious for piston-to-valve contact near the exhaust valve reliefs if you put any kind of fairly large aftermarket cam in them as well. The absolute most I have seen on one is 8500rpm and that's pushing it because the stock rods are pretty weak in those. But yes, in theory you could throw some F22/H23 rods(which are actually .5mm longer than the factory H23A blue top rods), some Type-S pistons, and cams/valvetrain to end up with a really healthy setup. You would still run into efficiency issues at high rpm because of the long stroke though.

THEhomelessONE

Thanks for the replies. I came across a thread here named fastest h22 times and there's a couple folks NA in the 10s with similar weight with stock bottom end h23a's? No idea how they're pulling it off, need to do more reading up when I get a chance.