Direct C51
Well-Known Member
To get to the point, I have a Corvair powered Sonex with about 10 hours on it. I have spent a good portion of those 10 hours diagnosing a rough running condition and am hoping I can get the collective input of the crowd here and maybe we can stumble upon something I haven't thought of.
Engine: 3.0L Corvair with all WW/SPA conversion parts, built exactly as the conversion manual suggests. WW Electronic/Points ignition. MA3-SPA carb.
Problem: Mixture full rich, DA above 3000 or so. Advancing the throttle from 2700 RPM - wide open throttle, I get rough engine operation. Reducing throttle through that same range, I get rough engine operation. 2700RPM and below, the engine runs smooth. WOT the engine runs smooth. below 3000 DA the problem is less severe to almost not noticeable. Mixture leaned aggressively, the engine runs smooth.
Troubleshooting: I have noted the #2 EGT is not responding normally. It is roughly 150 degrees F below the average of the other 5 cylinders when the mixture is full rich. The #2 EGT decreases another 100 - 150 degrees when advancing the throttle from 2700RPM to WOT, then increases at WOT. The same is noted when reducing throttle from WOT through that range, the #2 EGT decreases 150 degrees or so, then increases once below 2700 RPM. All other EGTs respond normally. When leaned aggressively, the #2 EGT will increase significantly and settle right in the average of the other 5 EGTs. Advancing or reducing throttle through the range of 2700 RPM - WOT again result in drastic decrease of #2 EGT followed by an increase once out of that range.
It seems my #2 cylinder is running very rich, or otherwise not combusting correctly. Compression check is normal at 76/80. Spark plug looks slightly richer than the others but not so much as to be a concern, and certainly not fouled. Has anyone seen these symptoms before? I'm not sure if this is a mixture issue or ignition issue. I plan to further test on the points ignition (so far I have only tested on electronic ignition, and possibly change the spark plug and wire.
Engine: 3.0L Corvair with all WW/SPA conversion parts, built exactly as the conversion manual suggests. WW Electronic/Points ignition. MA3-SPA carb.
Problem: Mixture full rich, DA above 3000 or so. Advancing the throttle from 2700 RPM - wide open throttle, I get rough engine operation. Reducing throttle through that same range, I get rough engine operation. 2700RPM and below, the engine runs smooth. WOT the engine runs smooth. below 3000 DA the problem is less severe to almost not noticeable. Mixture leaned aggressively, the engine runs smooth.
Troubleshooting: I have noted the #2 EGT is not responding normally. It is roughly 150 degrees F below the average of the other 5 cylinders when the mixture is full rich. The #2 EGT decreases another 100 - 150 degrees when advancing the throttle from 2700RPM to WOT, then increases at WOT. The same is noted when reducing throttle from WOT through that range, the #2 EGT decreases 150 degrees or so, then increases once below 2700 RPM. All other EGTs respond normally. When leaned aggressively, the #2 EGT will increase significantly and settle right in the average of the other 5 EGTs. Advancing or reducing throttle through the range of 2700 RPM - WOT again result in drastic decrease of #2 EGT followed by an increase once out of that range.
It seems my #2 cylinder is running very rich, or otherwise not combusting correctly. Compression check is normal at 76/80. Spark plug looks slightly richer than the others but not so much as to be a concern, and certainly not fouled. Has anyone seen these symptoms before? I'm not sure if this is a mixture issue or ignition issue. I plan to further test on the points ignition (so far I have only tested on electronic ignition, and possibly change the spark plug and wire.
