Electric power steering pumps can be more efficient than a belt driven pump, but
for other reasons, predominantly that assist is only needed when actually turning,
and the assist required is inversely proportional to road speed.
Pretty much exactly this. There is no efficiency to be gained from bolting on an electro-hydraulic pump and running it full blast all the time. It will, all things being equal, always use more power due to conversion losses. That being said, I didn't do this for any perceived efficiency benefit, it was only for packaging. The car has fairly heavy steering now which I am actually a bit ambivalent about, I have no need for effortless parking lot steering and feel at speed is about the same as before.
Thats not true at all. Plenty of people with power racks are still using EPAS
Exactly. We put a prius EPAS column in our E36 lemons race car. The thing kept nuking power steering pumps and tossing the serpentine belt. All we did was loop the lines on the rack and mount the column. The torsion bar isn't even locked out in the spool valve and it works great. Steering feel is slightly worse but it's not exactly razor sharp from the factory so
In preparation for dyno tuning I added some instrumentation to the car. I wanted exhaust gas temperature and fuel pressure monitoring in the ECU to make sure things weren't going pear shaped. Bought a Setra transducer on ebay and made a short M12 to D38999 jumper harness that connected to one of the spare I/O bulkhead connectors Karl set up on the engine harness.
I didn't get any pictures of the EGT probe work but the engine now has 8 K-type sensors on it. One for each cylinder, one in the collector, and one in the downpipe. I connected everything to an 8 channel thermocouple to CAN interface box from AEM. Apart from an intial SNAFU where I had to learn the hard way that the AEM box does not support grounded sensors, everything went together pretty smoothly.
I took last Friday off work to meet up with my ace calibrator friend Neel at a shop in the inland empire called Nine-11 Design. It's a high-end Porsche shop that graciously allowed an old Volvo to besmirch their Dynapack for a day.
The Dynapack absorber unit was a very tight fit on the passenger side of the car. While bolting up the hub adapter I was nervous about clearance but it just about fit.
Their cooling fan setup is highly optimized for air cooled Porsches so we had to be careful to keep temperatures in check. There just wasn't enough airflow to keep up with steady state operation above about 4000rpm so for everything after that we just did transient pulls from 2500 to redline.
The fuel map was already 90% good from road tuning so we focused on timing and boost control. From a baseline of 220whp at 8psi we ended at about 320whp and 325lbft of torque at 14psi. The day was cut short due to some scheduling conflicts with Neel so we ended it there. I'm going back in a few weeks to continue dialing in timing, boost control, and knock detection. There were no signs of detonation at 14psi so I'm confident the car is capable of 350whp or more on 91 octane pump gas.
I couldn't get the stupid embed function to work but here is a short clip I took of one of the pulls we did.
https://youtu.be/DeyrS2Kk1yY