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the car sounded so nice and pulled hard however mileage was terrible....
the 12~14 mpg deal breaker... then, still not enough psi to push the hot air through an intercooler and have any decent charge out the back end... the automakers messed around and quickly discovered the only supercharger that can breathe life to a sewing machine without disastrous mpg is a turbine (getting a free ride via exhaust power)... the only workable systems that made it to production cars, were roots' powered by 6 or 8 cylinders (w/ sufficient torque). there might be a few decent centrifugal units out there, but in the case of the Raptor, when belt slippage was finally solved, the bearings melted, and were consumed (BOOM)...
Originally Posted by Lemming
I went down that path with my 968 SC-powered 924S. For racing it was a waste of many many dollars, probably spent 2x $$ on the SC setup than on the V8 option.
Last edited by odurandina; 11-14-2014 at 12:56 PM.
Well I'm all for good mileage, but at the moment I'm ok with walking before I run tuning wise, there may come a day when it goes full stand alone ecu map sensors and all that jazz but I'm more concerned with the project stalling than I am with the mpg of the product.
Roots type blowers are inherently less efficient than turbine style and turbos, however the Buick ultra hit 22mpg weighing almost twice what my car does, same with the supercoupe 3.8, so decent mileage can be achieved. Also the benefit of that parasitic loss is instant boost. Most of the spirited driving of this car happens on the blue ridge parkway and similar, there are not monster straights where constant load power is useful, it's tight, winding diving corners where torque and chassis are key. even stock I love the 944 on those roads
I'm fine with moving the focus from mpg to performance because it's more consistent with how I use the car these days. (shorter trips, more pleasure driving)
My supercharged 84 944 is fantastic. The power comes on instantly, the torque is fantastic, and I can't get enough of the sound. It took me a year to complete but I didn't touch it last winter. maybe 6 mos. total work in my spare time.
The heart of the whole system is the Rogue Tuning DME Tuner and logger. Joshua at Rogue is definitely the man to talk to first. I would never use a rising rate FPR, having full control of your spark and fuel is the only way to go.
It's not easy, but totally worth it. Cost me about $2500 all in(not incl. the DME mods). I am a professional Tig welder and have built many cars before this.
Mike:
I think I see what you mean, fuel psi is being bled off by the injectors at WOT and that pressure is being replaced by the FPR staying wide open under boost.
My thought is that the 951 regulator is supplying fuel to a similar engine under similar boost conditions and yielding slightly more than my expected power level. Shouldn't the RRFPR from the 951 be a god fit for my application? What variable might I be leaving out?
I'm not sure what you mean by your first statement, and it scares me.
The variable you're leaving out is ECU tuning. If you're planning on tuning the ECU then the 1:1 regulator (which is not what I would call a RRFPR) will be fine. Otherwise you will need to add some extra fuel somehow, as the stock ECU/AFM will not accomplish this under boost. This is what the RRFPR's do.
Have you got a copy of Corky Bell's book on supercharging? Worth getting.
Mikey: I see what you mean here, It sounds like between the cost of the MSD box and an aftermarket RRFPR I'm approaching the cost of converting the car to Mega squirt,
DarenD:
Firstly, Beautiful project!! any idea what kind of hp/tq numbers you are getting? hows driveablity? any MPG figures? Have you had any belt slippage given your belt routing? If you had it to do over again what would you go about differently?.... sincerely your biggest fan
Lastly the first step in the project has been taken, I picked up an old bronco 2 so that the Porsche can be down!!!
DarenD:
Firstly, Beautiful project!! any idea what kind of hp/tq numbers you are getting? hows driveablity? any MPG figures? Have you had any belt slippage given your belt routing? If you had it to do over again what would you go about differently?.... sincerely your biggest fan
Lastly the first step in the project has been taken, I picked up an old bronco 2 so that the Porsche can be down!!!
Thanks. Based on calculations, I should be around 180 hp. I plan on putting the car on a dyno in the spring. Driveability is fantastic, the car drives like stock, only with far more hp and torque. The belt was ok for a while but did start to slip a bit when it stretched. My car is currently on an early 5-rib setup, I'm going to convert to 6-rib. I don't foresee any slippage issues, but if so I can always add another tensioner. If I had to do it over? I'd like to change my S/C inlet and outlet flanges and maybe do 2.5" I/C piping. I may do this this winter.
Glad to hear the 944 is off the road, good luck on your project, feel free to ask questions, I'll be happy to help as much as I can.
On this topic of FPR, I am also planning the same kind of M90 build, currently my original FPR is faulty, leaking down, fuel leaking out of vacuum side etc. I was going to replace it with a lindsey racing adjustable kind as its nearly as cheap as a new Bosch OEM. From what I understand, this will work in an identical fashion to the OEM, just manually adjustable? No detrimental characteristics for supercharging?
DarrenD
It would be great if you could say how you are currently managing your tuning, or what planned improvements you have?
I take it you have the Rogue MAF conversion? what else have you done? Larger injectors? Rogue DME chip with a tune?
What kind of fuel pressure reg, stock? looks stock in the photos.
My suggestion? find a 3.0L motor and swap, No fab work, about the same power (or more if its a 968 motor) and really around the same money. The S/s2 bellhousing will allow you to use your existing Torque tube, you need the engine harness, dme and motor and your good. There are documented swaps and info around on it. You'll need a trans after you blow up your NA transaxle, but if your nice it may last a little bit, you'll want and S2 box, but an S one would also live behind it as its beefed up vs the NA.
My s2 is 968 swapped and while i kinda wanted to supercharge it because of the altitude.... The cars pretty damn quick as it is, much much faster than any NA and without all of the headaches of a custom SC setup.
Yes I was thinking of doing that, and conveniently an S2 engine came up on ebay for cheap because its from an accident damaged car and the engine mount lugs are partially broken off the block, it also needs a rebuild. NA would keep life simpler and more reliable, not to mention no lag and thump of boost which is not ideal in RWD despite the balance of the 944.
I had searched, but havent been able to find a decent thread of sombodys conversion process. if it was possible I agree it would be a simpler option.
The thing about supercharging is the higher roof than an S2?
I was looking at a second hand wolf 3D ECM that seems to offer extensive tuning opportunities and might make the whole thing more managable.
The negativity toward supercharging I find hard to swallow when in theory if a 951 can make good power, why not a supercharged motor of the same build quality? I feel I would prefer the instant response of the charger for what I want, and am interested in it as a challenging project.
11-14-2014, 09:05 AM
The belt was ok for a while but did start to slip a bit when it stretched. My car is currently on an early 5-rib setup, I'm going to convert to 6-rib. I don't foresee any slippage issues, but if so I can always add another tensioner. If I had to do it over? I'd like to change my S/C inlet and outlet flanges and maybe do 2.5" I/C piping. I may do this this winter.
