turbo a older 911

afterburn 549 · 07-14-2003, 09:50 AM

would like to hear from anyone has put a turbo on a 911 (mag case) please do not reply to this if you are going to just repeat the why you cant routine. thanx.

island911 · 07-14-2003, 10:55 AM

If it has case-savers, I imagine it would be fine for a bit more force. (how much more, I dunno) You might see what the supercharger guys have to say (for max boost on a mag case)

FWIW; I came across a write-up on a 1974 Turbo.
Here are a few pict's

I don't know if a mag case was used here, or not. I'll check it out, if I get a chance.(not my book)

I found it an interesting combo; year, bodystyle, and that an airesearch T04 turbo and boost restrictor were used. (I happen to have those components, squirrled away somewhere)

Anyway, cowtown makes a good point about the tranni. you wouldn't want to shift fast with boost . . .the torque spikes would do-in a mag box.

Aside:
Welcome to the board.

Coupeville, eh? Nice place. Californians may talk up their "Muscle beaches" . . .but for sure, you've got the best Mussel beach.

afterburn 549 · 07-14-2003, 10:56 AM

the most that can go wrong is every thing, so with that said to do it the correct way is repace everthing. So I have everthing except the the alum. case but if that stretches pulls I'll do that to . In doing the math 250 hp is 250 hp no mater how it's aquired- lots of cam and carbs or... ... turbo in my opinion it's the studs that the problem and I allready fixed all that

TerryBPP · 07-14-2003, 11:33 AM

Does anyone sell a supercharger kit for the 2.7? If so, Does it use CIS or something else? Always wondered about it.

724doorE · 07-14-2003, 11:34 AM

The 2.5 racing engines had 275 hp and used mag cases and mag trans as well so... go for it I remember reading that the 74 RSR turbo 2.1 needed an al case due to its power 480-500, but thats a pretty serious different story. It is surprising no one has ever devised a main girdle to help give the case some support. If the thickness of a girdle were removed from the main web, behind the case bolts, one might be able to use a main girdle , of an obviously custom design, to strengthen a mag case..........

island911 · 07-14-2003, 11:44 AM

Quote:

Originally posted by afterburn 549
. . .In doing the math 250 hp is 250 hp no mater how it's aquired- lots of cam and carbs or... ... turbo . .

Actually it's the torque, that is the problem. HP can be had by revving higher (and keeping the force (torque) the same or lower.)

You've got to use torque #'s when planing for the weakest link.

beepbeep · 07-14-2003, 12:10 PM

Actually, it's not torque that is main problem when using mag-cased motor, but peak cylinder pressure. The higher the pressure, the stronger the force will be trying to pull heads from the case.

Turbocharging means that you are boosting extra and increasing relative compression to something that could reach equivalent of 13:1 N/A C/R. That extra pressure will pull the studs out of the case even faster, and mag cases are famous for pulled studs even with stock C/R.

If you could make a girdle inside the case to bolt studs into it would work. Other possibility is to timecert whole case before assembling it...

Also, there is usual Porsche-problem of leaking heads in turbocharged applications.

I've been explained this by one Porsche-tech and i kinda believe it:

Aircooled engines head/cylinder temps fluctuate much more than watercooled ones. Watercooled motors are moderated by water (which has much higher temperature coeficient than air) and keep temperatures pretty constant. Temp of aircooled heads bobs up and down depending on RPM, boost and throttle opening.

These high amplitudes of temperature swings also amplify mechanical stresses and dimension changes caused by streching. So while watercooled engine top really moves twice every time you start the car (once when you heat it up and when you cool it down), aircooled ones are constantly heating up and cooling down depending on your driving style, grinding themself into each other in the process.

This extra wear produces whar Porsche mechanics call "uneven mating surface" between heads and cylinders and you end up with leaking heads even if studs are intact (usual 930 problem). Porsche solved this by beam-welding heads to cylinders and introducing water-cooled heads whenever serious amounts of boost were used (935, 959, 956, 962). In your case you can prolong the time before your heads start "walking" by machining O-rings, using high-strength studs, timecerts etc.

afterburn 549 · 07-14-2003, 02:15 PM

thanx for the input;I do know that its the torq and heat problem. sombody has to try it right wilbor? right orvill. Like I said was hopin to stumble on somebody that may have tried this. input?

obrut · 07-14-2003, 02:51 PM

OK I'm curious - why do you have to use the mag case? why not just install a 930 engine?

I'm about to replace my perfectly good early AL cased 2.7 with a mag cased 2.7 in order to comply with rule changes for historic race cars - its a pain in the a$$...

Cheers - Ryan

afterburn 549 · 07-14-2003, 03:43 PM

I don't have a an alum. case and I have all ready loaded the mag case so I think for the mony this will be at least E for effort. If the mag case gets twested then the alum. case will be next; unless you know some that has a alum. case pretty cheep now. to make a long story longer I have done every mod possable to make this work- but remains to be seen. thanx; input?

IROC · IROC's Garage

There was a guy on the old porschephiles/porschefans mailing list that installed a turbo onto a '77 mag-cased 2.7, I believe. We emailed back and forth about it somewhat. Seems that he set it up for modest bost (don't remember the actual amount) and had gone through the engine and twin-plugged it, etc. and the thing was working just fine. IIRC, he had a couple of years worth of hard driving on it and it was holding up to the abuse.

Speaking of high horsepower 2.7s - Galen Bridges in Marietta, GA used to have a killer 2.7 in his silver '74 (?). Twin plugged it by running a second distributor off of the cam gear for an MFI pump and was running compression ratios that I thought were "ludicrously" high, but it held together fine also and he was probably in the 275hp range, easy.

Mike

beepbeep · 04:58 PM

well there is no spectacular input that will change anything...yes, it will probably work, at least for a while. It's not the best case around for turbocharging, but it might hold depending on how good you prep it with case-savers and how much boost you run.

That's about it.

afterburn 549 · 07-14-2003, 03:54 PM

thanks for the incourgement; this is twin pluge with a engine managent sys. too( digital). I am thinking along the same lines as for boost probly not quite 1 bar and a 1/2 a brain hooked to the gas peddle. history will see? thanx for the info.

Adam · Adam's Garage

dougcl & bb are both Pelican members who run turbo 2.7 engines. I think bb's car was rated at around 253 hp (I think it's a BAE kit). Hopefully they'll weigh in with some encouragement for you.

I'm always keeping an eye open for components to do the conversion...

afterburn 549 · 07-14-2003, 05:08 PM

getting a turbo is ez its the management sys. thats $$. thanx for the input

dd74 · 07-14-2003, 05:33 PM

Supposedly the 915 gearbox with 7.31 ring and pinion can sustain a 3.3 930 engine, so I wouldn't be all that concerned with a transmission if you're prudent with RPMs and gear changes. Just don't shift it at 7K like a drag racer.

RFNG's turbo kit is about ready to be sold, though it's for a 3 liter. I haven't heard exactly that it wouldn't work with a 2.7. Might be worth looking into.

You can always buy a 930 engine. Should mostly plop right in, I think. You would need an ext. oil cooler, of course, unless you have one already.

dougcl · 07-15-2003, 01:32 PM

Afterburn, check here http://members.rennlist.org/dougcl and email me if you have any questions.

Doug
75 911S

dd74 · 07-15-2003, 01:53 PM

Doug: that is SWEET! I don't think I've seen your car before. Is that an original 930 motor? What's the story on it? It's very nice. I thought you needed a whale tail to fit an intercooler under the hood.

How's all that power translate to (what looks like) narrow body wheels and tires? Are they narrow body wheels and tires? 15x6s? 15x7s?

Again, nice looking car.

JTO · 07-15-2003, 02:04 PM

Yes Doug, that is one nice looking middle-year. You are in Oregon too and I hope to see it in person some time. What is the story behind your car, engine, suspension, wheels, body mods, etc.

Thanks for the photos.

Troy

dougcl · 07-15-2003, 02:06 PM

dd74,
Thanks! The engine is the original 2.7 (all sorted out). It's a low boost (5 psi) system with stock pistons. Makes about 200 ftlbs of torque at the rear wheels between 3500 and 5500. Engine runs cool, and it seems like a great package.

Doug
75 911S