CP Pistons offer a 93mm piston.

[Orphan]

Hey guys,

Just thought i'd let you know CP pistons manufacture a 93mm piston. Its a 1+ mm oversize piston for the EJ20 WRX and the part number is SC7401. They are an 8.5:1 compression ratio though. Maybe someone with actual piston knowledge could get the specs of CP and see if they would actually be an option. Could be a good option for forced induction projects if they fit.

Cosworth also offer a 93mm piston for the EJ20 WRX part number PA2690.100

Quite pretty but for two sets it will run you around 2k and yet again they look to be 8.5-9.0:1 CP.

Unfornately besides that CP only make 90's 95.5 96 and 100 so it looks like custom is going to be the only real way to go to get 93mm pistons for an N/A application.

I've found a company that makes 93mm and 98mm pistons but yet to hear back from them regarding the specs to see if they are useful to the VH community.

[gs14racer]

Cp already has VH45 pistons, they are built to order (ie you tell them the over bore and compression you want) they take about 2 - 3 weeks to get and they are vh45 specific. They run about 1100. They are even on ebay.

Enjoyhttp://cgi.ebay.com/ebaymotors...ories

[Orphan]

Lol my bad. $1100 isn't that bad as long as they are decent pistons. Thats good to know though thanks. Then again they are custom order so not exactly as economical as they would be if they were actually stocked but I doubt there are even 100 sets of aftermarket pistons sold for the VH series worldwide every year.

Are CP pistons any good? From what i've heard they aren't super but still alright but thats just here say from forums etc.

Does anyone think it would be worth it to bore a VH out to 96 or 98mm? In either a 41 or 45 it would be pretty nice, i believe 98mm brings the 41 to around 4.5 and the 4.5 to just under 5L from memory.

Anyone know general costs for boring out an engine 2.5m radious?

[hannibal]

The cylinder liners are only 3mm. I dont know how much you can bore them out, maybe 95mm?? That leaves them 2mm thick. DOnt know if thats enough.

John has bored out his VH45 to 98mm with a displacement of 5L. He obviously installed new sleeves. If I were trying this I'd find some off the self sleeves to use. Darton has a nice list on their site.

Is it worth it? Still waiting to see John's dyno numbers. I think it will be...

Maybe this is a good time to ask, how thick should these sleeves be? Seems like the larger the bore, the thicker the sleeve should be. And I cant figure out how the sleeve is held in place.

[PanzerAce]

Realistically, any big name aftermarket piston manufacturer is going to have analogous end products for a given application. CP Pistons, JE Pistons, Arias, Wiseco, etc doesn't really matter that much.

re: cylinder wall thickness

The guys on HBZ building high hp have settled on .125" cylinder wall thickness for a wet liner as the recommended minimum for boosted engines. Bear in mind that these engines are running in excess of 200whp/L. So if you want serious displacement, I'd go for new sleeves, and shoot for .125" (unless the VH is a dry sleeve...anyone care to shed some light on if it's dry or wet?)

[Orphan]

Hannibal are you sure about the liners only being 3mm? They look quite a bit thicker then that in this picture. Even so they don't look 2.5+3.175=5.675mm thick as would be a safe thickness to bore out 2.5mm radius.



There is a local machine shop not far from where I live that quoted me $495 to bore and hone the block to .200 (5.08mm) oversized. I haven't ever had an engine bored out before but that seems pretty reasonable to me.

EDIT: I also have no idea how they are held in place haha, I always get the picture in my head of them sliding down onto the crank haha. Can anyone explain how it all holds together?

Who is John? Any pics of his project? I'd love to see + can't wait for results, since 98mm is quite large would you also need to get the heads machined to limit squish area?


Modified by Orphan at 6:21 PM 4/8/2009

[OUKNO]

John Dixon

He is building a BAD @SS MOFO!!!Here's some info for your reading and viewing pleasurehttp://forums.nicoclub.com/zerosearch

http://www.youtube.com/watch?v...ex=18

http://www.youtube.com/watch?v..._page

[PanzerAce]

EDIT: I also have no idea how they are held in place haha, I always get the picture in my head of them sliding down onto the crank haha. Can anyone explain how it all holds together?

-40* sleeves + 150ish* block + hydraulic press. Basically, simple tension holds them in.

realistically, if you wanted to go serious overbore, you'd have to get new liners/sleeves, so it wouldn't matter what the original thickness is.

[Orphan]

Oh that 5L ITB build, i've seen that on youtube before. That thing sounds great, can't wait to see it finished and with a full tune. I love that slight rasp it has, sounds like an exotic.

[hannibal]

I too am curious about what (if anything) John did to his heads. Ive never heard him mention anything.

I found the 3mm cylinder liner thickness in the VH45 SAE paper. Top left column of page 126...http://www.nicoclub.com/articl...n.pdf

Hannibal are you sure about the liners only being 3mm? They look quite a bit thicker then that in this picture. Even so they don't look 2.5+3.175=5.675mm thick as would be a safe thickness to bore out 2.5mm radius.

I dont even see the liner in that pic, and I cant figure out what youre adding up. A 1mm overbore reduces thickness by 0.5mm.