Looking for 12 - 12.5:1. Not looking to rebuild the whole engine. Keep stock valve train, etc.

I would even consider 13:1 if it can be done without rebuilding the whole engine. I understand I would need race gas for this.

I am hoping I could get this w/ pistons and gaskets.

Can anyone confirm and/or recommend parts?

-Ry

 

smoking the go-fast crack pipe eh as hyashi puts it. Not a big deal for this happen, expect to pay around 2500 when it's all said and done with parts and labor. Parts would be JE-pistons, new headgasket, rings, bearings, RTV sealant and if you want to do it right, you would need to fork up the extra cash for stronger rods (although stock will be fine), and a new ECU (extra $$$) for tuning.

-ardy

 

forgot to mention larger fuel injectors and a fuel pressure regulator.

 

I've got a steady go-fast IV drip going by now

Would I need a whole ECU or would a VAFC be able to deliver the extra fuel?

 

you can get by with a vafc, but that's a band-aid approach and not the best way to do it. Know what I mean? It works but just isn't the best way. Plus, after spending a grip of cash on pistons/rods and whatever, it would be very frustrating to sacrifice the longevity of the motor by skimping out on proper engine management. Remember the vafc can't control ignition timing, it can only control fuel delivery and the range of that delivery is not that much depending on how crazy you want to go.

 

Aww hell, you don't even need extra fuel to begin with. The stock mixture is rich as it stands, and higher compression really doesn't change the mixture much, it just extracts more energy from a given quantity of fuel (higher thermal efficiency).

But if you're going to pay the 100 point internal engine mod price, why not go all out? ;-)

Anyways, to get to 12.5:1 compression, you need to reduce the combustion chamber space by 6cc. Normally this would be done pretty much entirely through increasing the piston dome size. A dome increase of this size might cause a little bit of interference with airflow (think during the overlap period), but you'd probably be o.k.

Don't expect to get massive power increases. I'd wouldn't expect more than about 3-4 lbs-ft of torque across the rpm range. Nice, but nothing major.

Cost for some good custom pistons would be around $600+. Stick with stock Honda rings unless you plan to sleeve and overbore the motor (new rings will be about $100-$120, haven't checked prices lately). If your motor is fresh, all you'll need is a light hone on the cylinders (figure a $100-$200), otherwise an overbore will cost more. Might as well throw in new rod bearings while you're at it. You could do the job yourself if you buy a piston ring compressor, but otherwise, expect to spend a few hundred on labor. All told, you could get away for $1500 or so if an overbore isn't needed.

That's a lot of money and hassle (pump gas will be iffy on 12.5:1) for small gains. Now, if you decided to sleeve the block and open if up to an 89-90mm bore, you'd be looking at an extra $1000, but now you'd be getting the compression _and_ an extra 140cc of displacement. Now you're looking at total gains in power/torque in the range of 9-10% throughout the rpm range. That would be worth it, IMO.

UL

 

This mod is not for Speedventures, and I realize its gonna stick me into unlimited.

But with the rest of my OTC mods I'm gonna be there anyway.

I was hoping to see more gains than that tho from upping the compression.

So many ways to spend my money