2.5 or 2.6

[ber911]

What cylinders are you using with the 89mm J.E pistons? I am looking to go the same route but am unsure about sleeved cylinders.

Robert

[blue72s]

P+C______________89mm_______90mm________92mm
Displacement _____2466cc_______2519cc_______2634cc
Spigot____________97mm_______97mm________97mm
CR_______________10.5_________7.0__________10.5
Price____________$3400________$1800________$3400

Take your pick.

[Cupcar]

BTW Andial has a high compression 90 mm 2.7 kit that nominally is 10.3:1 as a 2.7 on 70.4 mm stroke, comes out ~9.7:1 on a 66 mm crank and 2519 cc.

[Plavan]

I was lucky and had some old 89mm cylinders re plated.

[Cupcar]

Do the 92 mm RSR pistons require a special cylinder head machining cut to use with 2.4/2.7 heads or are people lowering CR with base gaskets alone?

[kenikh]

New to the BBS, so go easy on me.

Just a thought on the 2.5 short stroke motor using the RS pistons. 7:1 compression seems ideal for a blown motor (This is roughly the CR of a 3.3 turbo motor). Has anyone out there ever considered/attempted super/turbocharging a 7R cased motor? You'd obviously need to sort the MFI or carbs appropriately and swap in a no overlap cam, but seems doable. This idea has always been a pipe dream of mine, although I have obviously never tried it.

[KobaltBlau]

Welcome.

Not too many have built turbo cars on a mag case, a few with 2.7 CIS cars.

one of the big advantages of RS pistons is valve clearance for big cams. you could probably build a very powerful motor if you had a racing class that allowed 2.5 + turbo. For street or something, I think you'd be better off starting with a 930 motor. most people don't run too hot of cams with a turbo anyway.

[Shuie]

Originally posted by kenikh
Has anyone out there ever considered/attempted super/turbocharging a 7R cased motor?

Considered? Yes. Attempted? No.

A small displacement turbo is one of my dream motors. 2.5 using the low compression of the Mahle P&Cs on an aluminum case, 2.2 crank & rods, big oil pump, Supertec headstuds, Carrera manifold and motronic ECU w/knock sensor. Thats all I could figure out on my own though. Researching this stuff made my head hurt and I came to the conclusion that it was going to take someone a lot smarter than me to figure the rest of the motor specifics out.

Goran forwarded me a couple of websites on turbo charger maps, etc, in response to the link above. I'll see if I can find them.

[KobaltBlau]

Originally posted by Shuie
Attempted? No.

not quite true, there have been a few turbos on 2.7 CIS, at least one of them using that BAE(?) kit. we're not talking super high output, though. Certainly a different kind of motor than you'r describing, Shuie.

[kenikh]

I was thinking almost exactly in line w/ Shuie, except I am preferential to using a supercharger, specifically the Eaton unit out of a C230 Mercedes. It is perfectly sized for a 2.5L flat six. I have seen plenty of 3.2 installs using an Eaton roots type supercharger, integrating it with a serpentine belt running off of the crank. There is just something about not interrupting that beautiful exhaust note with a turbo...

I also agree with Shuie on another thing: the research is making my head hurt. I figure the case would have to be aluminum (but am not 100% sure), boat tailed and shuffle pinned with all Raceware or Arp hardware. Stock rods would probably be a no-no. Twin plugs, pretty much a must. Piston squirters installed if none exist. An intercooler would have to be involved. Cam would need to have minimal overlap (3.0/3.3 turbo unit?).

I also like the idea of a Carrera or 3.3 Turbo manifold, but the cost of a Motec w/ crankfire is brutal. Then again, the programability of the Motec in the long run (and the tunability a Lambda/knock sensor provide) would probably pay for itself in the labor you'd save trying to figure out all of that stuff without data acquisition. I belive that you can get the Motec brain with a boost sender, too.

My biggest question is how much of a beating can the lower end of an early motor take? If you have a 2.5L motor churning out 260-270HP, it makes no sense to build it if the bottom end goes sloppy in 20K miles.

Thoughts?

[KobaltBlau]

interesting ideas, but I stand by the assertion that starting with a 3.3 turbo motor would be cheaper and more powerful. If you have some odd-ball racing class to fit into it's a different deal.

[kenikh]

Originally posted by KobaltBlau
interesting ideas, but I stand by the assertion that starting with a 3.3 turbo motor would be cheaper and more powerful. If you have some odd-ball racing class to fit into it's a different deal.

You are 100% correct on all of your points. It would absolutely be cheaper and almost assuredly be more powerful. The only advantage to the short stroke, small pistoned motor would be that it would have the potential to redline higher, which is a source of fun unto itself.

This isn't for an oddball racing class; it would be a street motor. Unfortunately, I'm just an oddball with a penchant for the unusual. Just knowing myself, I'd never be happy with a 3.0/3.3 turbo in there. Anyone can swap in a factory motor, but a one-off lump is a conversation piece that never gets old. Then again, it could become a headache that never goes away...

[KobaltBlau]

I understand, we're on the same page. you're probably talking about over $10k even if you DIY the rebuild, though.

And there is a lot of fun stuff you can do with a 3.0/3.3, or even an SC base, with custom pistons, induction, injection, exhaust.

But I understand where you are coming from.

[82SC]

i dream of a 3.0RS

3.0 longblock...swap out the pistons with high comp Mahles
throw away the CIS
have a 911S MFI system bored and rebuilt for a 3.0
Brun-Bros RSR dual dizzy

longevity with the sturdy case...displacement, there is no replacement...and a rare motor that not many people out there have

that is my plan

[kenikh]

Originally posted by 82SC
i dream of a 3.0RS

3.0 longblock...swap out the pistons with high comp Mahles
throw away the CIS
have a 911S MFI system bored and rebuilt for a 3.0
Brun-Bros RSR dual dizzy

longevity with the sturdy case...displacement, there is no replacement...and a rare motor that not many people out there have

that is my plan

I did a web search on the distributor you mentioned, but didn't find anything. Any hints?

[Shuie]

yes, yes, yes, there are a a lot of fun motors we could build. The 3.0 RS with MFI would be another great one. Lets get back to NA 2.5s and 2.6s though.

The 10.3:1 90mm Mahle pistons sound real interesting. Id never heard of those before. Are they as difficult to find and as expensive as the high compression 89mm P&Cs are?

edit: just called Andial and they have a set of these on the shelf

[Shuie]

Originally posted by kenikh
Any hints?

Here are the distributors. Very exciting project.

[KobaltBlau]

me too 82SC except I would use TWM 3003s, megasquirt, and coil packs, twin plug of course. loses some "sex appeal" but gains a few things too.

Cheers,

[kenikh]

Since we talking NA motors (sorry for co-opting the thread ), has anybody seen one of these mean motors? 66mm stroke, 2.8L motor (95mm cyl), 9.5 CR, twin plugs, 300HP, 8600 RPM, pump gas:

http://www.supertecperformance.com/wild-porsche-engine.phtml

Gives me shivers!

[KobaltBlau]

yes, love it. Grady Clay is a big fan of this type of configuration, he has built many.