Mad-Machine

you will need to replace the internal chain gear.

Dmitry

Beta 1.8 and 2.0 have same bore (diameter)

According to webtech diameter of pistons:
81.97-82.00 mm (3.2271- 3.2283 in.) [1.8L,2.0L]

Mad-Machine

AND if you add new pistons and do not mind making your engine impossible to rebuild later.. get the largerst diameter replacement pistons you can buy. The Factory says the rebuild limit is 1mm, if you bore your cylinders out to 1mm and fill the bores with the proper slugs.. you are looking at a jump from 1975CC to 2025CC in displacement. You MIGHT be able to go larger, but I would talk to a machine shop before I made that decision.

Dmitry

^^^ do you think 50cc will give you much hp gain? Maybe couple of ponnies.

Mad-Machine

if you have to rebuild the engine anyway.. might as well go as large as you can. And yes, I am certain that those 50cc would probably make a difference.

Grottenolm

So I need a set of aftermarket 83mm oversize cast pistons with 11:1 or even 11,5:1 compression ration and bore out the cylinders 1mm, right?

@Mad-Machine
How much hp will the added 50ccm give me? And how about the higher compression?


Does anybody know who produces cast pistons with higher CR (except shop.hp with their 13:1 pistons) ?

hamhead

Compression I would imagine on a Tib would bump up the HP like 7whp per 1:1 you move it up. So going from the stock 10.3:1 to 12:1 would probably net like 14whp. Just a baseline though, lots of other factors come into play.

Zman

If you want pistons you should ask Rick at real engineering (look at his store forums here) I think I remember having seen some 13,x high comp pistons at his website. If not, you could also ask David at kspec, I haven't seen them there, but both David and Rick are very helpful, serious and they will always try to get you the best.

Be careful with the porting and polishing of the head; I myself asked those questions a few months back, and according to the majority, if you're not going turbo (and judging your mods you are not) the benefits you could get in very high rpm range are not worth what you loose on the bottom.


Think about this: imagine your engine has like 180whp but it get's to the upper 60% of the power above 5800 rpm, and you are racing someone with "only" 160whp but he gets 80% of his power starting at 3000rpm. At launch you will feel like a turttle against him, so highest HP numbers are not the thing to aim, but a reasonable power curve. Also, our engines don't rev really high, at a very max of 7000 rpm (and that's tweaking the electronically controlled rev limiter) you still want to get the power earlier, compared for examplke to a high revving engine that can reach as high as 9000rpm...

LarryMcFly

First, 1.8l pistons will give you 10.6-10.9 of cr...not worthed the trouble unless you have plenty of time.

Second, if you install agressive cams, you don't absolutely need a piggyback but you absolutely need some king of fuel tuning. An ajustable fuel pressure regulator could do the trick for cheaper. It's less efficient, but a whole less trouble to install and tune. It allows you to delay the purchase of a piggyback. B&M frp for hondas fit perfectly (command flow)

Third, a 65mm tb is quite large for an N/A application. I have a 60mm tb from a Honda CRV, works great.

Fourth, with a p/p head job, you will lose on the bottom end but gain on the top end. If you have a lightweight flywheel an UDP, it will hurt you in first gear, at launch ONLY....when I am at the track, once I am rolling, I rarely go under 5000rpm. It depends on your application.

Finally, about the rev limit on the beta. Yes, theoretically blah blah you can't rev safely over let say 7000rpm....however, I have been at 7000rpm for easily over 80 000km including many track days without anything close to a problem. Someone I know goes to 8000rpm without any problems to.

Everything said in this is based on first hand experience, not theories....
Also remember that to support high compresison pistons/agressive cams, you will probably have to do some ignition work too. Noise level of your car will be insane at 13:1. Daily drivability of your car will be quite reduced.

hamhead

El-major offtopicness... but did you have to modify the CRV TB at all to fit the Tib? In case you haven't noticed, we've been looking for a larger replacement off of a stock car.