Finally got it back to the dyno after switching back to gas. Mathew wasn't available so he just emailed us a safe baseline tune he had on file. ECUtek will have their tuning suite available in a few weeks. We'll start tuning ourselves and continue development. No idea what the SAG 2.0 is capable of. It's a whole new realm for us. A few salient points:
Bore 83.5mm, same as a BP 1.8
Stroke is 91.2mm (BP is 85.0mm)
Rod ratio of SAG 2.0 is 1.70!
BP is 1.56
B6 is 1.59
K20A2 1.62 (86mm stroke)
That's really high, particularly for such an undersquare engine. So it should rev like mad right? Well, no. High revs require a head that breathes. The PE-VPS head has small ports. Really
small, crazy high velocity ports.
Peak head CFM stock with stock cams
174 CFM BP05 (NA8)
204 CFM BP4W, BP6D (NB)
157 CFM PE-VPS (ND)
We ran the flow bench way out to 3mm past OEM lift on the stock ND cams and as expected, flow didn't improve much. This points to a very thoroughly developed head, cam grind and ECU mapping. It works exceptionally well, truly world class in it's intended usage regime. Outside of that (trackday bro!), it's going to take some creativity to find big N/A power.
So why the really high rod ratio? Detonation resistance, that's why. Chambers that build pressure rapidly near TDC (low rod ratio) are more prone to uncontrolled hot sparky things happening. In a high rod ratio engine, the piston zips towards TDC then slows down, chills out and spends some time with it's bros, the DI and plug. They sit down and have a nice controlled combustion event. In the past, this relatively slow kernel growth and flame front propagation hurt low speed torque. With advanced multi injection pulse per evolution DI and continuously variable cam timing (atkinson/de-atkinson), OEM's can actually make what is effectively a variable compression ratio engine and control heat in ways that were not possible 10 years ago.
OEM rods are, ah dainty. We're not yet sure how much boost they'll accept before they wilt. Journals, yeah they're small too. Low friction means less heat wasted means less fuel burned.
So the bitchin rod ratio and acceptable stroke means we could theoretically spin an SAG 2.0 pretty high and still have mean and peak piston speeds in acceptable ranges. We tore an SAG 2.0 down a few months back and are slowly planning our first N/A build with some custom internal bits. Fun stuff. We'll be learning more as the months tick by.
Hard to read, sorry. 153whp, 146tq on 91. Tune, GCC header, metal cat, 2.5" exhaust. Otherwise 100% stock.