Adapting supercharger to a 3.2

[Slanski62]

I'm interested in a forced induction system for my 3.2-based build. I say '3.2-based' because the motor is a 3.2 now, and when I rebuild it, I'll bump it up to 3.4 liters. I also plan to dual plug it.

From what I've read, a 3.4L, dual plugged, chipped, freer breathing motor might yield 300 HP on a good day. I want more than that. I'd like to exceed 350HP. I think forced induction is the only realistic way to get there. Assuming I find a blower and can mount it, what other considerations are there? Can I use my stock intake and run a flexible hose from the blower to the throttle body? What about engine management? What systems are there that are flexible enough to handle fuel delivery and timing? Are there any off-the-shelf kits I should consider? Note I prefer a supercharger and not a turbo, unless folks convince me I'm wrong in my thinking.

What else do I need to consider? I don't know what I don't know, so all feedback is appreciated.

Steve

[impactbumper]

the only advice i can give you is not to fall into tpc crap. Tons of engine management options out there nowadays.

[kuehl]

Steve,

I, naively, started a supercharger project 10 years ago. Its a lot of fun.
Forced induction via superchargers on the 911 is not uncommon. Superchargers of Knoxville supplied plenty of kits years ago.

Its been a long learning curve for me, simply because I 'naively' thought anything could be done. It can't. Logically there are limitations whether you are doing this with a stock configuration or modified. Since I started the project I've had to have the engine torn down 3 times, lol, so much for not reading and learning before taking the journey.

On my stock US spec 3.2 (1987) getting an extra 100 rwhp with 6 psi was not difficult. Stock engine, exhaust, injectors, a little extra fuel pressure and modification to the fuel maps (don't forget the ignition maps, ohhh boy!). It all finally fell into place when I called "Sal" (you'll find his ingenious posts here on Pelican discussing MAF).

Today the engine is a 3.5, 9.5:1 with larger headers (needed when you get above 3K rpms). And, the engine is apart because of the "3.5" and its pistons; flame spread. I should of kept the displacement stock (pistons and jugs) and simply tweeked the fuel and ing maps more precisely. But... its all been fun because of the stubborn streak I'm learning how things really work. Not reinventing the wheel, simply listening and learning; and that' been the most rewarding part ... meeting and discussing it all with fantastic people.

If you decide to go down the slippery slope, which I do not advise, there are plenty of good engine management systems out there today, and unlike years ago when we could only read plugs and look EG temps there is wide band (our savior).

My suggestion for what its worth, talk to the pro's, read all the threads and books, and if it does not make sense..... "Just call Sal".

Soon as I figure how to do valve timing and break in the new rings, not literally, that's happened twice, I'll be tossing on some form of new engine management system to support the twin plugging we did this past winter.

Bottom line for me, I'm more optimistic with this latest build simply because I'm less naive. A little bit less.

[Slanski62]

Hi Kuehl. Thanks for your thoughtful response. I know Sal. He's just now fine tuning his DME code for my car with his MAF. It's based mostly on my discussions with him that I concluded 300HP is the most I will see out of my current platform, and that's after a rebuild to 3.4L. I'm very curious why you say you do not advise doing this. BTW, my mechanic is Chuck Miller. He speaks highly of you.

Steve

[Slanski62]

Hi impactburner. I like your tag line! Could you tell me more about your dislike of the TPC stuff?

Steve

[Nick Triesch]

If you do everything right your 911 could end up as fast as a 2016 Subaru Impreza compact sedan! How fun would that be???

[Rodsrsr]

I ran a SOK Paxton unit years ago on my somewhat tired 3.2 and it was awesome. The model was SN2000. I was using the stock AFM back then, with a rising rate fuel pressure reg and a tuned chip to retard the timing. It put out about 6psi but not like a turbo. It was a very linear buildup of power. The boost increased with rpm, so you may have had 6 psi at the upper rpm range just about when youre ready to shift. The result was a very smooth clean acceleration, and it basically made the engine feel like a 3.8. It was also easy on the drivetrain. I ran it for years behind a 915 gearbox, never had a problem. It put out about 325 hp, which is around a 100 hp increase. It basically brought the performance of the car into the 21st century and yes it was fun watching kids in their late model turbo Impreza's unable to walk away from a 40 year old P-car.

[wwest]

The more you "derate" the base engine, ~8:1 compression ratio, the more boost (***) can be used.


*** PRE-COOLED,COMPRESSEDairflow.

[Tippy]

Simplest for the Motronic system is a rising rate fuel pressure regulator from BEGI and MSD BTM (boost timing master) for timing retard.

Yes, you can hook silicone hoses to the throttlebody.

Run an intercooler. You can find cheap $100 ones on ebay all day long that will work for your 350hp goal.

Protomotive makes chips and fuel pressure regulators to handle the Motronic system, but he's charging big money now.

Turbos are superior to peak hp over superchargers, but a screw type (Whipple, Kenne Bell, TPC) or roots style (Eaton) make instant low end boost and torque.

That can really hard on a 915 trans, no sweat for a G50 though. Not sure what you have?

[Rodsrsr]

I subsequently ended up doing a motor refresh, due to the dreaded over-rev on a missed shift to 3rd. (make sure those couplers are adjusted!) and at that time decided I wanted more, power so I opted for a turbo. The pros are that its "much more power." but it comes at a cost. With the mods I did to the engine and the increase in boost it is simply too much for the 915 to abuse anymore. Going to a 3.4 is a waste of money IMO, increasing displacement will yield very little gains for the amount of money invested. I dont even think the 3.4 would get you to 300 hp and thats after $12,000 rebuild. Im sure it could be done, but at serious effort and you would end up with a very un-streetable motor. Simply increasing the displacement to 3.4 will probably give you an extra 8 to 10 percent increase in hp if that. My guess is a nice 3.4 will land in the 240-260 hp range. I've gone over this a million times in my head and my conclusion is that if you currently have a 3.2, the only cost effective way to get into the 400 plus hp zone is to turbo it. If you're set on swapping out P/C's, forget the 3.4, and grab a set of 930's then you can go as much boost as you want.

[kuehl]

Originally Posted by Slanski62

I'm very curious why you say you do not advise doing this.

With the 3.2 motor stock (other than more fuel pressure), using a rising rate FP (which is not a clean way to go, that's why we have "Sal"), a slipping "V" belt to drive the charger, about 4 psi (boost gauge busted), with the super charger belt off we had a chassis dyno of 175 rwhp. This is because of too rich AFR's. Belt on we had 267 rwhp, again too rich AFR's. So +92 rwhp running a lousy set up.

Moving forward... serpentine belt. Boost now 5 psi. We meet Sal. Toss the rising rate and use a doubler. Larger injectors. Tuned the fuel maps No dyno but its like "you know, you can tell". 0-60 mph was just under 5 seconds.
The driver seat bends when you get on it. But, (the learning part) boost got into the crank area and we blew out seals, so much for crankcase ventilation.

Forward some more. Added a belt tensioner to the serpentine system. Refined the fuel maps. Boost now between 5-6 psi. No dyno available but you know when your car accelerates faster. 0-60 mph in high 4's. We go more blow by at the rings. This is what happens when you play with a engine that has 100K on the jugs and pistons, Nikasil was worn.

Faster forward. Toss on some L&N 3.5 jugs with JE pistons (still at 9:5.1). Refine fuel maps and smaller blower pulley. No dyno but 0-60mp in mid 4's. We start smoking clutch packages so toss on a mid range Kennedy clutch package.
Lose #1 head (blow by at the top) and crack a ring.

Faster some more. Cut in flame rings for heads, new rings. Canyon cylinder studs. Step up to 1.75" primaries. She's purring like a kitten. At 5k rpms all hell breaks loose and we are flying, and.... crack top rings on 1 and 4. Come to find stock ring set supplied with the JE pistons are "stock". Now we learn about rings. And, after reviewing the data on the street tune (dyno was not available), we were pushing 8 psi when all hell broke loose. 9.5:1 + 8 psi on high dome pistons is not a good diet.
Some like to run with lower compression and put the boost on top. That's lag.
Me, I'm stubborn, I like to feel it all right out of the box. Now we learn about flame propagation and we talk to Total Seal rings plus all the guru's we should have talked to before and the books we should have read.

By the way, all above was on pump gas.

Today.... stronger rings, twin plugged, backing off the boost, to be: sequential injection and new ecu. And, we will dial back the ign advance (should have done that in the beginning... but you gotta love the acceleration

Bottom line. I would be just as happy with the stock 3.2 pistons, a finer tune and the 1.75" primaries. Because of the hemi heads you can't run high domes above a certain "total" compression on street gas and no cooler. I had just as much fun blowing off the young rice rockets with this 25 year old non ABS non air bag car.
Going from 3.2 to 3.5 is just fine on a normally aspirated with good cams and engine management, but on a blown system you gotta a lot of things to work on.
However, I'm for a penny in for a dime so what the heck.

But, its all in the fun.

I think you might find more reading on the Pelican Supercharged forum.
In either event, read, read, read before you pull any trigger. And, work with Sal.

[JohnJL]

I have a thread here you can find on exactly how I did this, trials, tribulations and results. I still track that car a dozen times year reliably with 450+ hp. It wouldnt be a nice road car though.