Should I build my 3.6 with MFI?

[Avery]

I was talking to a friend of mine this AM (who used to work at Garretson's back in the day and now owns a Porsche engine machine shop) about my thoughts on building up my 3.6 with MFI instead of going with the varioram induction that I already acquired. He said that if I want to go with the MFI, that he had an RSR MFI that he would give to me. I nearly **** in my pants! Trying to contain myself, I calmly ask him if the RSR pump would work in the 3.6. He said it should but that I ought to check with Gus over at Pacific Injection (which happens to be located on my way to work). I have the stacks, injectors, throttle valves, and air filter housing from a 72 MFI unit. Man....a 3.6 with an MFI would just be perfect in my RSR replica. I know I have to modify the throttle valves but with a free RSR unit, I was not going to complain...no way.

Does anyone out there have any experience with this kind of modification? Will the RSR pump work with no mods or will I have to get a new space cam for it? Here's the BOSCH PN: 0408126019v. Can anyone verify that number for me?

thanks....

[82SC]

wow...sounds cool...

if it were mine I would...

the only draw backs I can think of is getting the engine to run right with the MFI...but I think alot of that has to do with the person working on the car

I think the engine will run a little rich, so you might get frowns from the cars behind you or people walking by your car...I know paul weir's 3.5L RSR motor made his eyes tear up cause it ran so rich

but I think the wow factor and the cool factor would make up for these...plus sounds like you are getting the parts for very cheap!!

let us know what happens...

MJ

PS I'll take the RSR parts if you don't want them

[Tim Walsh]

P-Thomas spent a fair amount of $$ getting his 3.5MFI car running right. I think the RSR pump will handle it and run right but it will take alot of $$ and fiddling.

I'm almost sure you'll have to get a new spacecam for it.

[Paul Thomas]

That pump number is for a 73 RS/ 74 Euro Carrera MFI pump. Define RSR MFI. Are we talking high butterflies? Your intake ports are either 41.5 or 43mm, therefore you will probably have to get the throttle bodies bored and rebuilt ($1300) and get some adaptors to bolt them to the heads ($????). Go to www.eurometrix.ws to check on sizes and pricing. The 911 handbook has pictures of some adaptors that were made by Len Cummings at Autosport Engineering, check page 191. I would do the MFI no matter what, cause it would be cool and varioram is boring. For pump info talk to Gus and talk to Hanz at H&R in New York. 631.589.1600. I hope you speak Germ-English.

Worst case, you could sell that pump for alot and Hanz will build you one from good cores that he already has on the shelf.

Paul

[Elombard]

"I would do the MFI no matter what, cause it would be cool and varioram is boring"

Yes yes well said!!!!

[skinnerd]

The only problem I could see, is that you wouldn't be able to get enough air through the throttle bodies to feed that monster 3.6.... the factory certainly never had anything that big!!!
That said, I'd go for it big time. I think MFI rules. I love all that factory type stuff.... like the SC-RS engine. Somehow, someway, there are people that can help you make this work, so go for it.
Keep us posted.

[Paul Thomas]

There are a few of good ways to make this work unfortunately none of them are cheap. If you look at Eurometrix web site Matt lists a throttle body "from S to 42mm with a 44mm throttle plate", Unless i am mistaken, the first ones he did like these were for me. I then matched up a set of magnesium stacks and bored the crap out of them to match. They are 50mm at the top and flow lots of air. PMO sells vintage looking velocity stacks this size but luckily a friend has a 906 and he had a spare set of original stacks for it. The was an RS/SC MFI setup on ebay recently for $5500. If this set is at all serviceable, this is the deal of the century. the Kugelfischer/Bosch pump sells for about $9000 alone. Keep posting, i love to talk MFI.

Paul

[1fastredsc]

free?...................

[Avery]

Thanks for all the input. You guys now have me seriuosly leaning towards the MFI to handle air/fuel mixing duties for my 3.6.

I'll try to drop by Gus' place tomorrow to talk to him about the pump for my 3.6. If Gus says I have to modify the RS pump, I'd rather modify my T pump and return the RS pump to my friend (yes, it was free and no way would I turn around an sell it...I'd just give it back to him). I just can't see bastardizing a good RS pump when a T pump will do. I was hoping I could use the RS pump without any mods but that was probably wishful thinking. I'd only consider modifying the RS pump if the change was reversible. Does anyone have anyexperience here? Are there advantages of using the RS pump that I'm not aware of? This pump does not have the thermostat so cold starts could be harder....although the SF Bay area really does not get all THAT cold. The pump case is aluminum which is kinda cool but you can't really see it anyway and it's not all that much lighter.

Does anyone know if could I potentially get more HP and/or torque from an MFI set-up over the Varioram?

Thanks!

[Wayne 962]

Uhh, I hate to be the wet blanket, but there's almost no way that you would get this to work properly without investing at least $4K-$8K. Heck, $4k is about the rough number for rebuilding and obtaining all the parts for a regular RS. Here are some problems:

- Pump not calibrated. The pump *needs* to be matched to the displacement. This 2.7 will be way too lean for a 3.6

- T-bodies? As someone mentioned, you will have to have some custom ones made (along with stacks) as they are not going to be big enough. I don't even know if they will fit on the 3.6 heads (never tried it).

- The heads don't have holes for the injectors

- What injectors are you going to use? 935-style? You're in unchartered territory here, and that means big $$$

- I think since this is not a stock system, you'd be guessing on the setup, and the space-cam, and it probably would never run right, even after you kicked in about $6K for the fuel injection. Yes, it would look cool, but remember, the car is for driving first. Use the stock system or stick a TEC-3 on there for about 1/2 the cost...

-Wayne

[Paul Thomas]

Wayne is right along with the fact that your left cam doesnt have the drive for the injection pump belt. You would spend big big money, but it would be cool. If your friend would see his way clear to selling that RS pump and/or stacks there is another thread going on right now about a RS spec 2.7 and Rich could use that stuff.

Even with all of that, i'd do it anyway. My car is for enjoyment first, practicality second.

Paul

[82SC]

This is Paul Weir's 3.5L MFI...but it was not built on a 3.6L case..

If you want to stay old school...You can always go PMO's...I think that option has been done a few times....

I know the injection ports are not hard to have put in on the intake boss...and adding the MFI pully onto a cam is not too bad either...BA's book has a pic of a cam with a pulley attached by 3 bolts

I'd try to track down Paul Weir...he sells outragous items on ebay sometimes

Or talk to Steve Weiner at Rennsport systems...

I think wayne is right...it will be big bucks...but you'd have a pretty cool setup once it is all done...I guess it depends if you have the pioneer spirit in you...and how deep your pockets are


Porsche 3.5 RSR racing or street engine without induction system. Makes 375hp and redlines at 9200rpm. Engine has a 3.2 Carrera crankcase bored out for 100mm cylinders, it has boattailed main bearing saddles and Carrera oil pump, 3.2 935-962 crankshaft with factory polished titanium rods and titanium rod bolts. It has a lightened flywheel, light crank pulley, 935 chain tensinors, special smaller idler sprockets, Raceware headstuds, nuts and washers, Mahle 3.5 RSR 100mm 10.3 to one compression pistons and cylinders with lightweight 22mm wristpins, Big valve twinplug 930 heads with 54mm titanium intake valves and 41.5mm titanium exhaust valves with special valveguides with smaller valvestem diameters, ASSE high rev valve springs and Norris titanium retainers, 44mm intake ports and 42mm exhaust ports, Niresist headgasket sealing rings, GE-100 cams with left side mechanical injection pulley drive stub, Porsche factory RSR twinplug distibutor, sparkplug wires and looms, 12 sparkplug holddown clips, 2 MSD 6AL sparkboxes with 2 Bosch blue coils and on-off switch, early style mechanical injection style engine wiring harness, GT Racing yellow fiberglass racing engine top air shroud, 5 blade cooling fan was used because we had to much cooling with a big oil cooler on the car. RSR style headers with Weber-Woods mufflers and two Supertrapp noise suppressors. All perfect machine work was done by legendary Seattle machinist Jack Conner, he has 50 years experience. Machine work included rebuilding the titanium rods, balancing, machining heads for twin-plugs, machining cylinders and heads for niresist rings, manufacturing niresist rings, polish and straigten crankshaft, machining case for 100mm cylinders, boattailing mainbearing saddles, machining sides of cylinder bottoms for better airflow, notch piston crowns for big valves and GE 100 cam lift, install custom valve guides and hone to size for titanium valves, perfect valve job. Perfect engine assembly work was done by Paul Weir and Swiss Porsche racing engine expert Walter Gerber and included all new bearing, seals, gaskets, rocker arms, shafts, chains and hardware etc. Engine was dyno tested by Jerry Woods and gave 339hp and 269ft lbs of torque with GE 60 cams, dyno sheet available. With GE 100 cams installed now engine makes about 375hp and quickly revs to 9200rpm. Engine cost approximatly $55,000 to build without an induction system. Engine was run in my street car from 1997 to 1999 and has about 10,000 street miles on it including 3- 2000 mile roundtrips from Seattle to Montery California each summer. This engine has never had a problem, runs like a jeweled Swiss watch and is absolutly bulletproof. This is a one of a kind engine and a rare opportunity to aquire something special.

[1fastredsc]

3.5rsr (drool). Why not just use some twm stacks and a tech 3, whole setup shouldn't cost more than 5-6k and it's a fully adjustable fuel injected stack system?

[jmz]

cool factor would be way high but other than that; Why? The MFI stuff works well with the lower displacement peaky engines but with a 3.6 monster displacement motor just keep the varioram dme stuff. It will have a nice smoothe power band and pull from anywhere. You will spend alot of money making the MFI stuff work on that motor. Maybe you should just build a 2.7, 2.8, or 2.9 motor with your "free RSR" pump. ...doubtful it will end up being free b/c it will probably have to be gone through by Gus. ...oh and nothing boring about a varioram 3.6 in an early RS look car!

[kzm]

only some pumps can be made to RSR spec's and be adjusted for 3.6. With slide injection and the correct pump work, my 3.5 RSR motor runs real clean and fast. Good luck!

[Paul Thomas]

Kurt is right about the pump. Hanz at H&R told me that he will only build big motor pumps from core T pumps. Also, my 3.5 MFI runs great too, idles near normal and only smells a little rich at idle. It is all about the right space cam for the displacement, redline etc.

I had also heard that Paul Weirs 3.5 was so rich that his eyes watered. If that is the case it was because he was running the wrong pump and had to compensated at low RPM for the fact that it was leaning out too much at speed. If you look at the description of his 3.5 build he says that they used 22mm wrist pins. BA says that in the early 3.5 motors they used those pins and found them to be a mistake because of the pin location and gave them too much deack height. They then switched to 23mm wrist pins.

Kurt, what is that plastic tank in the back left of the photo? Is your breather hose attached to it? I have seen the same thing before but didn't know what it was.

Paul

[pu911]

Paul,
Any idea what kind of output your motor has, I'll get mine on a chassis dyno once I get it running correctly.
Phil

[Bill Verburg]

If you're going to spend that kind of $$ go for full Motec/TWM w/ some dyno time to dial it all in. It will run perfectly at all times.

[kzm]

the plastic tank is the breather catch tank. eventually, when i put a 935 dry sump up front like the factory did, the catch tank will be the sump and my 935 roll cage transports the blow-by from the breather hose in the engine bay to the dry sump. then, the cage has two functions. an RSR motor will always seem a little rich at some low rpm's because it has a ton of overlap in the cams. but believe it or not, mine will pass smog test for a 69 porsche so i can't be too rich don't you think. moving the dry sump to the front is the most valuable thing ballance wise you can do to help a tail heavy 911 corner like a mid engine car. can't wait till i find the $$ to do it. hmmmm, what can i sell today.

[Paul Thomas]

Kurt,
Thanks for the input. Where did you get that tank? Factory part? The front mount oil tank is on my short to-do list too. I will post Carolina Speedwerks phone #. Dave makes a tank just like Smart Racings for about 1/3 the price if i remember right. Any more pics of your motor would be great for my "archives".

Did you buy that motor setup like it is? If not, how much time did you spend getting the slide valves right. A friend of mine has them on a 2.5 and he doesnt run it much because it has an ON or OFF element to the throttle.

Paul