Engine Dyno testing of Renesis
08-23-2006, 03:36 AM
#329
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Originally Posted by Wildcard
... Understanding and controlling the ECU seems to be the key to reliable performance. ...
08-23-2006, 04:29 AM
#330
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Originally Posted by Wildcard
I recently did a 3200km road trip, mostly in remote parts of Australia, so I had plently of opportunity to look at the top speed of my RX-8 under different conditions. Here is what I learned:
Over time the long term fuel trim (LTFT) in my car seems to gradually creep up. It was at 11% at the start of this trip. The result was that above (160km/h) 100mph, AFR's were pig-rich (<0.75). This not only effected fuel economy, but also max speed. Under this condition, I only got a max speed of 205km/h. Running that rich must really kill the power.
Seeing this, I reset the ECU by disconnecting the battery, and immediately my AFR's leaned out by 10%. My top speed also increased to 216km/h. As the trip progressed, I found that the LTFT would stay at 0 for about 3 hours max, and then it would start increasing gradually - first 2%, then 5% etc. This also resulted in the AFR's becoming richer and economy getting worse. In all I reset my ECU 3 or 4 times during the trip to reset the LTFT back to zero.
Note that these AFR problems only seem to be an issue in Closed Loop. I have found that the cruising speed needed to be in closed loop varies - anywhere from 130km/h to 160km/h. So most people aren't going to encounter this LTFT problem at all. Unless you are trying for max speed. I have no idea what criteria the ECU uses to adjust LTFT.
The second thing about top speed is that I think wind direction and speed make an pretty big difference. On this drive, I had headwinds all the way, and the fastest my car ever got to was 220km/h. 6 months ago in exactly the same configuration, it got 240km/h with a slight tail wind.
Over time the long term fuel trim (LTFT) in my car seems to gradually creep up. It was at 11% at the start of this trip. The result was that above (160km/h) 100mph, AFR's were pig-rich (<0.75). This not only effected fuel economy, but also max speed. Under this condition, I only got a max speed of 205km/h. Running that rich must really kill the power.
Seeing this, I reset the ECU by disconnecting the battery, and immediately my AFR's leaned out by 10%. My top speed also increased to 216km/h. As the trip progressed, I found that the LTFT would stay at 0 for about 3 hours max, and then it would start increasing gradually - first 2%, then 5% etc. This also resulted in the AFR's becoming richer and economy getting worse. In all I reset my ECU 3 or 4 times during the trip to reset the LTFT back to zero.
Note that these AFR problems only seem to be an issue in Closed Loop. I have found that the cruising speed needed to be in closed loop varies - anywhere from 130km/h to 160km/h. So most people aren't going to encounter this LTFT problem at all. Unless you are trying for max speed. I have no idea what criteria the ECU uses to adjust LTFT.
The second thing about top speed is that I think wind direction and speed make an pretty big difference. On this drive, I had headwinds all the way, and the fastest my car ever got to was 220km/h. 6 months ago in exactly the same configuration, it got 240km/h with a slight tail wind.
)You must have something broken, maybe the new recall problem? maybe the cat?
09-01-2006, 02:08 PM
#332
Hymee,
Do you plan on putting this engine back into a RX and dynoing it at the wheels or have you already done this and I just missed it? Do you plan on testing a second engine to see if there is discrepancies. One engine test is not a good representation of all rotary engines.
Please don't take this wrong, I really like what you're doing and hope you can capture even more data on this engine. It's nice to see real data that is documented.
Do you plan on putting this engine back into a RX and dynoing it at the wheels or have you already done this and I just missed it? Do you plan on testing a second engine to see if there is discrepancies. One engine test is not a good representation of all rotary engines.
Please don't take this wrong, I really like what you're doing and hope you can capture even more data on this engine. It's nice to see real data that is documented.
09-01-2006, 04:31 PM
#333
Thanks Raptor.
No plans to test multiple engines to see if there is such discrepencies. I would think (cough, "hope") that there would not be much physical discrepencies between fairly precision made components that would equate to more than a couple of HP, if that. It ain't like the parts are made in the back-yard or anything
The aim is to baseline with this engine, then test power enhancements against a stable baseline.
Cheers,
Hymee.
No plans to test multiple engines to see if there is such discrepencies. I would think (cough, "hope") that there would not be much physical discrepencies between fairly precision made components that would equate to more than a couple of HP, if that. It ain't like the parts are made in the back-yard or anything
The aim is to baseline with this engine, then test power enhancements against a stable baseline.
Cheers,
Hymee.
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