GAMI trip report 4 - PRISM and Turonormalizing

One of the most exciting developments coming out of GAMI’s engineering work on piston engines is the PRISM electronic ignition system.

The big takeaway from all of their work is the most important aspect of engine managment is the timing of the peak power pulse (PPP) in relation to the top-dead-center (TDC) event. Best mechanical advantage is provided by PPP at 15 degrees past TDC. This also provides cooler operation and eliminates detonation. But with the stoneage fixed timing systems on the engines, we are limited to shifting PPP timing by diddling the mixture, a very indirect and inefficient setup.

The principle of PRISM is so simple it is brilliant. Aided by new sensor technology, GAMI has instrumented the engines to directly sense in real time the cylinder head pressures, and then in a closed-loop control system vary the timing of the spark to place PPP at 15 past TDC. Their original goal was to allow turbocharged engines to run on unleaded gas. This they achieved, but it also results in cooler, higher power takeoffs for normally aspirated engines, and even protects from detonation if you get jet fuel mixed with your avgas. PRISM is still in final development and they are working with the FAA towards their certification.

GAMI has a partner company in ADA, Tornado Aley Turbos that makes add-on turbo kits for planes such as Bonanza’s. We had a long discussion on the possibilty of turbonormalizing the SR22.

The bottom line was that if someone was willing to leave them an SR22 for 6 months, they could fit a turbonormalizer (with PRISM when approved). And subsequent installs could use the STC and would take about 4 weeks. There is plenty of room in the lower cowl, although they would probably build a new exhaust system. That would easily make this a 200kt airplane.

The fly in the ointment is weight and balance. The turbonormalizer would add 50-60pounds to the nose. That would certainly make the plane nose-heavy. We discussed ways to counteract that, such as adding an installed oxygen system to the tail, and moving BAT1 rearward. But you would still lose 60 pounds or so of useful load, and combined with the 20-50pounds of TKS, 20+ pounds of new avionics in the 2003, the plane is getting porky.

I asked how that was handled with Bonanza’s. Apparently Bonanza’s are tail-heavy to begin with, so the added weight up front is a plus. And there is an STC for tip-tanks for the Bonanza that adds 160 pounds of gross (sacrificing utility category to normal in the process).

Any gross weight increase on the SR22 would seem to be a big deal, since it would increase the already-near-limits stall speed, and require CAPS recertification etc.

So, I don’t see a practical way to keep the utility of the SR22 with a turbonormalizer, much as I’d love one. Anyone have any ideas?


Opps, attached is a photo of GAMI’s TNIO-550 for the Bonanza. The Cirrus version would be a bit different, as the air intake is in a different location and there is more room in the lower cowl.