Quote:
Originally Posted by The Radium King
ergh. our cars have a maf and not a map so not certain if they can measure compressed air or not. if not then the sensor has to go upstream of the s/c. and don't think you want to have your 7th injector upstream of the i/c either - the fuel would just condense. again, now that you can find guys that can tune the 7.2 i would just go with bigger injectors as per ike84 and a custom tune.
my final thoughts on packaging before i moved away from it was to clean up the top of the engine (ie, go electric w the p/s, delete the a/c) put on a 996 intake manifold (taller). mount the s/c on top of the engine feeding upwards direct into an i/c mounted between the two intake runners. use the a/c condensers with a small pump and reservoir to cool the charge.
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The map sensors will do the job since they are hot film and have iat built in. It's not as accurate as using a map sensor but the nbo2s will smooth it out.
The stock injectors will also likely be sufficient. Bosch has a chart on flow rates. The prefacelift cars use a one-off injector but Bosch started making them for Porsche in 03. I want to say they're good to 350hp but it's been a long time since I've looked at that.
I would avoid a custom tune and work on a setup that will take a 996 tune. This will require a larger MAF but the ECU will handle at least 15% deviation from baseline maps without issue (ie 350hp). The reason I say that is despite an exhaustive search 2 years ago, I couldn't get ANYONE on the phone in this country who actually knows how to tune me7.2. I'm not saying that as gospel, it was just my experience.
There are workarounds for the tune though. You can retard timing with the clutch sensor under the dash. Rig it to be permanently activated and the ECU will pull timing. Also, you can fool the nbo2 input to the maf by either using variable resistors or by getting a hold of an innovate sc1 to output a custom signal that you can map based on a wbo2 sensor.
The reason I mentioned boost control is exactly what you mentioned trk. I got into the boxster game after the FI fad had died out but from what I read, a lot of conrods met their demise at the end of a 7psi sc setup. They should easily handle power levels of a stock 996 but I would be cautious going much higher than 325 to 350hp (which is conveniently where you'll top out your injectors also). SCs are intrinsically more difficult to control after the design stage of the build than turbos are, but there are a few options out there (vac controlled release valves, for instance) but I have no experience with any of those products to offer.
Also, piggyback injectors are a bit of a mess imo. If I were going to add more injectors, it would be for a wmi setup (more for insurance than performance).
Lastly, trk's suggestion is a very good one - you better put a damn good intercooler setup on this thing. Another shortcoming of the original sc kits. You could redirect the center radiate and dedicate it to a wic setup, or you can mount an air to air intercooler inside the rear bumper (after gutting the stock exhaust and removing that giant shock absorber bar and vent it through the license plate shroud.
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