Arch-Angel

I want to lower the compression of my h23 to about 8-8.5 so that I can get boost!
Is the best way to do this by getting new rods? I want to reinforce the engine at the same time...
If so can anyone recommend a good brand to use?

earl

Just put on a thicker headgasket. Shorter rods would drop your engine size

boostinb18

yah change the headgasket and psitons are also a great way to lower the compression.

texan

Shorter rods have no effect on engine displacement.

However it is a bad way to try and lower compression, as you'll also kill quench area with the piston not reaching the same TDC point (same goes for thicker head gaskets). You could also potentially run into clearance issues between the piston skirt and crankshaft. The best way to lower compression is with properly designed aftermarket pistons, which are now readily available in a variety of compression ratios.

X2BOARD

I've heard forged pistons wreak havoc on H23s sleeves or was that 22s ? But yes, new pistons would be the best way... a thick H/G, the cheapest. But you will change the cam timing with the H/G method.... necessitating adjustable cam gears to move the power band back down.

X2

texan

It's the H22, or any FRM cylinder liner for that matter. You need iron sleeves for aftermarket pistons on the H22, which is just fine because the stock pistons (especially on the H22A4) are about the weakest ones to be found in any Honda 4 cylinder.

Arch-Angel

thanks for the flood of input! Much appreciated.
So I have learned that aftermarket pistons are the way to go, but can anyone recommend a brand that woul dbe best suited to lower compression to about 8-8.5:1? I want something that is bulletproof...
Cheers!

TeStUdO

yeah, it definitely depends how much you want to boost on the motor. but i agree the thicker head gasket (cometic) is the cheap route, but you nneed the adjustable cams. If you want to make power and do it right, the pistons are the weakest link on a honga engine.

filetofit

I'll second the part about pistons being the weak link, guess how I found out.

earl

If you changed NOTHING but the length of the rod, it has to change the displacement. The piston would not go as far down or as far up in the cylinder, so the displacement would have to change.
If you reread the original question, the guy only wanted to change the length of the rod to lower the compression, not install a shorter rod and change the pin height.

Arch-Angel

Basically, I would like to shave 1.5-2 seconds off my 0-60mph times (get it down to about 6 seconds) and hopefully run quarters in the low 12's.
I have no idea how realistic these goals are, but in the end, I don't want to kill my engine! What would I need to do to the engine (in terms of reinforcing) to run 10psi at a 9:1 compression ratio?

keeping in mind that i can really only afford a stage 1 setup (for the mean time, I plan to upgrade over the next year or so) are those results I want possible?

speedworks

you will have to buy crower rods for the h23 which are about 650 dollars. eagle does not make a rod for this motor, only the h22

tk

Rod length doesn't change ci the piston goes up and down the same length exept it come s down further and goes up less.
The stroke of the crank determines the amount of movement

Example: if you have 4 inch stroke then the piston travels 4 inches and changing the rod length doesn't change that the piston goes up and down 4 inches,it changes the position where it goes up and down

Remember CI=bore x bore x stroke x # of cyls x .7854

Not rod length.
Rod length only changes the rod ratio and the speed of the movement

earl

Now that I stop and think about it, you are correct. That's the first mistake I've made this hour

Pelican

ah.............math

WONG FRIED RICE

lowering compression with a thicker head gasket, brings un necessary risks. Basically more chances of leaking. IMO

X2BOARD

With that train of thought... we shouldn't do anything to increase the power on our cars

If you're not breakin' stuff, you're not making enough power...

texan

That's not at all what he said. What he's saying (as am I) is that if you're going to do it, do it right. If you want to build the bottom end and lower compression, do it with pistons and not a thicker head gasket that partially negates it's own purpose by destroying quench tolerance. It will lower compression but at the same time increases the chances of detonation; the principle reason to drop compression in the first place.

Arch-Angel

OK OK!!! I will get new pistons!! We had already established that, but where can I get H23 pistons that will lower compression to 8:1?! I live in Australia, and no one down here has done much to hondas... It's finding out which brands do this sort of thing that I am having trouble with!

Is it worth doing the head gasket AS WELL AS the pistons for extra safety's sake?

If I want to run 10 pound boost safely can I run a 9:1 compression ratio?
AND
Will 10psi be enough to shave 1.5 seconds off 0-60mph and 2 seconds off quarter?


[Modified by Arch-Angel, 7:09 AM 10/24/2002]

X2BOARD

Pardon my apparent ignorance, but WTF does '...destroying quench tolerance. ' mean ? What tolerence is there in the quench area and how does a thicker H/G destroy it ?
The only thing that I know a thicker H/G promotes is being blown. But that's was H/G's are for... they are the 'fuse' before you blow the motor anyway. Admittedly, thicker H/Gs is not the ideal way to go as it is not a stock H/G (stock rules) and affects the cam timing and belt fitment, but it does work as some members of this board will testify.

As far as where or who to get pistons from.... the majority of piston companies out there will make a piston for ANYTHING as long as you give them measurements such as bore size, desired CR and the like. Hell, I just had some custom JE's delivered, 40 over, 11.5:1 for a GSR, it took almost 6 weeks with delivery time and ran me a hair under $600 shipped. Getting a piston to spec will not be a problem.

9:1 will go 10psi on aftermarket pistons with NO problem, you can even go up to 9.5:1 with only 10psi safely. (Remember, tuning is everything, regardless) Haven't you heard of people boosting 7 and 8 psi on stock GSR bottom ends ? 10:1 CR !!! Of course, that's pretty crazy... but it can be done... WOW, it's late... am I tired..... ZZZZZZzzzzzzzz......

texan

X2BOARD- In order for quench area to be effective at increasing the knock tolerance of a combustion chamber, the piston needs to get as close to the quench pad as possible (and properly mate up to it). Without very tight tolerances here (KB Pistons feels anything over .080" removes any measurable effect), the point is lost. Most of the really good engine builders aim for a tolerance of .040-.050". In order to drop his 9.8:1 static CR to 9:1 with a thicker head gasket, he'd have to run a head gasket approx. 9mm taller than stock. In fact, just to drop his CR to 9.5:1, he'd still need to run a gasket 5mm thicker than stock. Either way, he'll remove every bit of the quenching effect, thus lowering detonation resistance. Many engine builders feel that dropping a 1/2 point of compression but losing quench effect results in a net loss of detonation resistance, meaning you're worse off than before. This is what I term as "doing it wrong".


Arch-Angel- Actually I never said you needed pistons, the honest truth is there are very few people who have built H23 turbos, and I know of no one with firsthand experience as to how strong the internals are. Honda tends to make the internals stronger as RPM limit drops (because they no longer need to be so light), and in that regard there are other DOHC non-VTEC Honda motors running 20 psi on the stock internals without encountering problems (thus far). It's a commonly held notion that anything remotely nearing 10psi of boost requires a built motor, and its also a false one. A friend of mine ran at least 12psi on a stock B16A for 2 years and never had a problem (his daily driver too), when he did finally smoke the motor (which had nothing to do with the boost) he built it up, dropped the compression, and regretted it dearly. Less power, less response, less fun AND he spent more money in the process. If you're just planning to run 8psi of boost, and you don't abuse the motor all day long, there's no really compelling reason to build it up IMO. You just have to know the limits of driving a turbocharged Honda, which means basically use it once in a while, but not constantly. Not even a built bottom end will handle constant flogging, the heat involved will still cause a meltdown.

And no, you won't be running low 12's on such a setup. That will require about 350-400hp on 4th gen Prelude, which wouldn't be found until 15-18psi on an H23. You should fairly easily run high 5 second 0-60 times though. You'll be looking at around 220-250hp to the wheels with 8-10 psi of well tuned boost. Of course all of this is just my opinion, I could be wrong.

pissedoffsol

if you use aftermarket pistons, you need to get it re-sleeved.

DONT FORGET

Arch-Angel

Thanks to everyone who contributed to this topic!! It has given me a lot to think about. I know I am only a newb, but all the info helps.

Ok, so just to make sure we are on the same level here...
My plan is to go for a 9:1 CR with new pistons, and use a T3 turbo with a custom exhaust mani ( I am sure it would be too much trouble to try to find a prefab one here)
The aim is to run 10psi, and keep the stock clutch, fuel pump, injectors and oil/water feeders (till I can afford a better ones!)
I want to get a new computer, and will probably go for a Power FC. (No one can tune Hondata down here).

How does this sound? Not exactly high performance, but I just want her to hold together, while having a bit of fun.