RX8 Renesis Rotary eSC
- Thread starter brettus8
- Start date
I use Mazdaedit as a tuning tool and that has 'virtual dyno' as part of its software. I've also had numerous RX8s on a real dyno and have learned how to get the virtual dyno results within 5% of that. VD is fraught with traps for the unwary and you can easily get ridiculous results so It pays to treat results with some skepticism. This is why I will back up these results with a real dyno at some stage but in the meantime it's a great way to check on my progress.
r.brown.bayliss
Member
Yea, I played with an app Called Virtual dyno, https://barnhill.bitbucket.io/ a few years ago, and UpRev, a a tool for nissan ecus, I captured data on a run on a dyno, but couldn't get it anywhere near close to the what the dyno run chart said using the exact data from the run.
That's one of the ways that you don't use it ....lol Dynos use a ramp rate which tries to match what actually happens on the road but is never exactly the same. So no - you can't do that.
r.brown.bayliss
Member
I can't remember what data it wanted, but weight was a big part of it, which was a guess, and like you say accelerating the wheels on a dyno isn't the same as accelerating a car by turning the wheels
Went for a really good long drive Sunday which included about 1/2 hour of twisties where I got a chance to test the system.
Some observations :
Battery : got down as far as 44v and found it still performed well without noticeable engine power drop. Temp got up to 40C which is quite acceptable.
Motor : Got too hot to touch but no issues
Wiring: None of the wires got hot but the main 2AWG wire to the ESC got a little warm right where it ran next to the other wires on the battery/charger but nowhere else - weird. Also noticed a smell - like the carpet getting too hot which I need to investigate. Doesn't make sense that it was the wiring as it wasn't that hot at either end.
Charger: outputs 500W straight after a pull then settles to 400w - working well but takes around 30 mins to recharge from 44V
Alternator: Measured at 88C after charging for 30 mins. Getting pretty hot but don't think that is too high.
ESC/relays/capacitor : enclosure still cool to the touch
Overall: Pretty stoked that I could drive at pace for that long and the system survived with no major issues.
Some observations :
Battery : got down as far as 44v and found it still performed well without noticeable engine power drop. Temp got up to 40C which is quite acceptable.
Motor : Got too hot to touch but no issues
Wiring: None of the wires got hot but the main 2AWG wire to the ESC got a little warm right where it ran next to the other wires on the battery/charger but nowhere else - weird. Also noticed a smell - like the carpet getting too hot which I need to investigate. Doesn't make sense that it was the wiring as it wasn't that hot at either end.
Charger: outputs 500W straight after a pull then settles to 400w - working well but takes around 30 mins to recharge from 44V
Alternator: Measured at 88C after charging for 30 mins. Getting pretty hot but don't think that is too high.
ESC/relays/capacitor : enclosure still cool to the touch
Overall: Pretty stoked that I could drive at pace for that long and the system survived with no major issues.
I had this experience once while diagnosing an engine performance issue on a stock vehicle. It turned out to be a fueling issue that resulted in a glowing catalytic converter well beyond normal limits. The smell of transforming carpet prevented me from unknowingly pressing on toward a potential disaster.
Don't have a cat. This car has seen multiple track sessions pre eSC also and I've never noticed the smell before.
r.brown.bayliss
Member
Despite no cats it could still be something near the exhaust getting toasty, extra air, extra fuel = extra heat
You could try routing some air to the alternator, some 50mm flexible hose to a high pressure point behind the grill, like a brake cooling duct and dump the output in the alternator. I think despite having the fan on the 'front' alternators suck their air in from the back rather than blowing air through the front. The fans look super inefficient too
. 80c might be too hot for any of the 20 cent solid state parts for the voltage regulator. Google didn't help, it gave one result saying 60c was too hot and a few saying 120c was the upper limitYou've got a sensored connection between your motor and ESC right? This should allow you to log the motor temperatures, did you check those? Please note that the magnets cannot really handle high temperatures, and it will demagnetise them as a result. Probably good to check this and maybe consider adding additional (forced) cooling.
Alternators heating up are a common issue with RVs etc I believe. While lead acids regulate their charge current intrinsically lithium batteries / chargers ask much higher currents, also at low engine RPM. While the alternators dont have issues with delivering 50A at higher engine RPM, their built-in fan simply isnt able to cool the alternator at lower RPMs, eventually killing the alternator.
I was already looking at alternative alternators for my build.. maybe even go with a 48V alternator and just converting that down to 12V to charge the 12V battery. The intake manifold kinda limits the space though.
I wouldn't risk the step down voltage to 12v for vehicle use given all of the attached 12v accessories. I had an alternator failure once in the form of excess voltage. In this case I smelled burning electronics which drew my attention to the voltmeter and then the radio which along with the dash lights since it was approaching darkness appeared very bright.
I was about 100 miles into a near 500 mile trip home and turned on everything in the car at that point and amazingly that pulled the voltage down enough to keep driving only needing to stop for gas. The regulator was delivering what looked like about 18 volts, that was in an 80s model sports car. Modern cars with their sophisticated electronics would probably implode with that kind of voltage surge.
I would add additional protection in this case, yes. And I would go with a Victron solution which is pretty well known for the quality of their stuff. It's still risky though..
You would say that a modern car has some form of voltage clamping on their 12V system, a sudden disconnect of the battery will result in a similar voltage surge.
You would say that a modern car has some form of voltage clamping on their 12V system, a sudden disconnect of the battery will result in a similar voltage surge.
No I wouldn't, I'd say there's potential to do even greater harm. I learned that manufacturers actually appeared to have built profit generating features into many cars to support the repair industry, as well as possibly set traps for DIYers.
The most notable I recall is a starter relay behind the in dash stereo, a cooling fan relay inside the front bumper cover area instead of the under hood fuse box where it would be plug and play.
GM some years back put out a TSB specifically identifying the cable disconnect with engine running to test the charging system as being responsible for causing an internal ECM short that prevented the system from shutting down completely, that would drain the battery overnight.
All of the above is why I would never start my car in order to give someone a jump, between the body control module and powertrain control module there are too many wires and potential for too many problems. Isolate, isolate, isolate. You don't want to hit 7 psi and then have your car burn down.
I'm not peddling pessimism, I've built a lot of motors, wiring harnesses and traditional turbo setups and made a lot of mistakes along the way that cost time and money that I no longer have the patience to repeat. I'm encouraging better safe than sorry from my experiences. I enjoy building, but repairing not so much.
Interesting conversation. Was talking to a friend over the weekend who races his rx8 in our local series. He had a faulty isolating switch recently and it resulted in almost every electrical component on the car being fried - who would have thought!
wkerstens, no I don't have the sensor cable hooked up so no record of motor temp. Will carry my temp sensor ...next time
Re the alternator .... I do have underdrive pullies on - might remove these for that reason. Also, I have set idle at 950 (vs 800 stock) and it idles much smoother than stock there.
wkerstens, no I don't have the sensor cable hooked up so no record of motor temp. Will carry my temp sensor ...next time
Re the alternator .... I do have underdrive pullies on - might remove these for that reason. Also, I have set idle at 950 (vs 800 stock) and it idles much smoother than stock there.
Put Bluey on the dyno today . Was hoping to break 300whp but didn't quite get there.
peak power of 282whp with impressive (for a rotary) midrange torque of 204lb/ft. Note to boost decline 6.5 down to 4psi at peak which was a little disappointing. Black trace on dyno was same car N/A so an increase of 73whp with only 4psi! Battery was outputting 360A @ 44v at peak power.
peak power of 282whp with impressive (for a rotary) midrange torque of 204lb/ft. Note to boost decline 6.5 down to 4psi at peak which was a little disappointing. Black trace on dyno was same car N/A so an increase of 73whp with only 4psi! Battery was outputting 360A @ 44v at peak power.
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Great results! It’s exactly what I calculated a while ago, probably pure luck that I got to around the same number but i’ll take it 
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What’s the main reason for the voltage drop in your pack? Cells themselves?
My BMS can go to 24S, and I got 24 cells, but decided to stick with 20S for now to protect the 12S Li-poly ESC.
Kinda makes me want to upgrade to the 16S ESC variant and upgrade to the new castle motor, that might be a decent upgrade. But first will have to finish my build as is, haha.
.What’s the main reason for the voltage drop in your pack? Cells themselves?
My BMS can go to 24S, and I got 24 cells, but decided to stick with 20S for now to protect the 12S Li-poly ESC.
Kinda makes me want to upgrade to the 16S ESC variant and upgrade to the new castle motor, that might be a decent upgrade. But first will have to finish my build as is, haha.
When I specd. everything I was only aiming for an extra 30-40whp and anticipating around 250A. But you know ..... 'moar powa baby' kicked in and It's actually at 360A and pretty much everything is on the small side. The batteries themselves are only 20Ah LTOs as I wanted to keep the weight down (because sports car). They do have a 'C' rating of 30C but in reality I don't think they are grunty enough.
Impressive and encouraging.
So I can actually run a few cells more voltage than a 12S ESC is spec'd for without destroying it instantly?Great results! It’s exactly what I calculated a while ago, probably pure luck that I got to around the same number but i’ll take it
What’s the main reason for the voltage drop in your pack? Cells themselves?
My BMS can go to 24S, and I got 24 cells, but decided to stick with 20S for now to protect the 12S Li-poly ESC.
Kinda makes me want to upgrade to the 16S ESC variant and upgrade to the new castle motor, that might be a decent upgrade. But first will have to finish my build as is, haha.
I've been wondering about the limits in an effort to make things a little more flexible to avoid a major hardware expense while experimenting. I have a 67v fully charged 16S hybrid battery, but 16S ESCs are not common locally or attractively priced. 12S seems to be the common high voltage ESC and battery range as far as hybrid batteries go.