Originally Posted by Shifted
There are no ITB or bored single throttle body kits available for the 928. However, a few people have installed ITB's with very good results.
Given that the diameter of the stock throttle body inlet is 3.75", I don't see there being much to gain by increasing that diameter. The potential gains for the intake could be in things like intake side tank spacers, lower restriction air filter setup, or a custom intake manifold.
The stock manifold has the resonance flap that the ECU moves at about 3.5k RPM to extend the torque curve. It works very well.
The spacers are a "thing" and I think that 928 Motorsports has/had them for sale.
928 Motorsports also offered a replacement flywheel, but I can't speak to whether or not it is lighter. Maybe worth investigating.
Pelican resells some of the 928 Motorsports products, for what it's worth.
Regardless of what changes you make, you're going to want to retune the ECU's. The SharkTuner lets you tune the stock ECU's after swapping in some programmable chips. However, if you're going to be buying the SharkTuner itself, I would recommend you instead switch to a modern ECU like MegaSquirt Evo Pro, or one of the MAXX or Thunder ECU's.
Obviously, if you go the ITB route, you'll be doing Alpha-N speed density. It seems like others are happy with that for their ITB 928's, but I have no personal experience with that combination.
The stock fuel injectors at stock pressure levels are plenty to handle much more power than stock. They are batch fired, and switch to double the firing frequency at higher RPM's. Effectively doubling how much fuel they can deliver, and how much power that they can support.
I wouldn't recommend changing the fuel injectors unless you're going to be pushing the power output above 400hp at the wheels.
Another option to consider is forced induction. Supercharger kits are still available, or you can roll your own. There aren't any turbocharger kits available, but they can also be built from scratch.
I have a turbo system on my 928, and it is very doable and completely worth it. However, it will require a deep dive on several systems and disciplines if you're doing it yourself.
If you want the "Easy" button, get a porken chip. It's got a routine in there that advances the ignition timing until knock is detected, then backs off a little. Since our engines are knock limited, that means you end up with the absolutely maximum power that your specific car can support. Safely.
If you decide to program the ECU yourself, you can play with the tip-in and acceleration enrichment to improve throttle response.
|