---------------------------------------------------------- Rocket-List Digest Archive --- Total Messages Posted Fri 10/05/07: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:04 AM - lean of peak injector balancing (Frazier, Vincent A) 2. 08:40 AM - Re: lean of peak injector balancing (Michael W Stewart) 3. 02:59 PM - Re: Update on Jim's Rocket (Don) 4. 07:59 PM - Re: lean of peak injector balancing (Jim Stone) ________________________________ Message 1 _____________________________________ Time: 08:04:01 AM PST US Subject: Rocket-List: lean of peak injector balancing From: "Frazier, Vincent A" Jim, Read this. http://www.swaircraftappraisals.com/MeyersForum/Engine%20Info/Engine%20O peration/Pelican's%20Perch%20Mixture%20Magic.htm It will tell you what you need to know. To balance your injectors only requires a few flights to get 'em pretty close. More if you really want excuses to test fly. The injectors that came with your engine are most likely all the same ID. But each cylinder has different flow patterns. IOW, the injectors should be matched to the flow, but they aren't. Assuming that you have a 6 cylinder EGT monitoring capability, fly at a fixed throttle and prop setting and altitude, start rich of peak and begin leaning and record the fuel flow vs. EGT every 0.1 gph. Just record the stuff near the peak EGTs, not all the way down from 28gph. No need for that much data! You're just looking for the peaks. The first cylinder to peak is the leanest, and so on. When you get back on the ground, call Don Rivera at Airflow Performance and tell him what you found. He can send you new injectors of varying ID to replace your existing ones. It's not that expensive and you'll easily save the money back in fuel savings. Basically, you're going to swap the leanest injector for one with a bit larger ID. Changing one injector changes the flow to the others since they're all drinking from the same well. So, you will have some trial and error involved, but not too much. You might need to swap the injectors around a bit, but when you get the peaks to happen within a GPH, or better yet, 0.5GPH you should have a smooth running, LOP, gas saving, clean plugs, cool temps engine. This is all from memory... hope I remembered the high spots. Vince P.S. Make sure that your EGT probes really are in the cylinder that you think they are or it'll get real interesting. ________________________________ Message 2 _____________________________________ Time: 08:40:53 AM PST US Subject: Re: Rocket-List: lean of peak injector balancing From: Michael W Stewart You may find this useful. MIke http://www.mstewart.net/super8/nozzles/index.htm "Frazier, Vincent A" Sent by: cc owner-rocket-list -server@matronics Subj ect .com Rocket-List: lean of peak inject or balancing 10/05/2007 10:59 AM Please respond to rocket-list@matro nics.com du> Jim, Read this. http://www.swaircraftappraisals.com/MeyersForum/Engine%20Info/Engine%20 O peration/Pelican's%20Perch%20Mixture%20Magic.htm It will tell you what you need to know. To balance your injectors only requires a few flights to get 'em pretty close. More if you really want excuses to test fly. The injectors that came with your engine are most likely all the same ID. But each cylinder has different flow patterns. IOW, the injectors should be matched to the flow, but they aren't. Assuming that you have a 6 cylinder EGT monitoring capability, fly at a fixed throttle and prop setting and altitude, start rich of peak and begin leaning and record the fuel flow vs. EGT every 0.1 gph. Just record the stuff near the peak EGTs, not all the way down from 28gph. N o need for that much data! You're just looking for the peaks. The first cylinder to peak is the leanest, and so on. When you get bac k on the ground, call Don Rivera at Airflow Performance and tell him what you found. He can send you new injectors of varying ID to replace your existing ones. It's not that expensive and you'll easily save the mone y back in fuel savings. Basically, you're going to swap the leanest injector for one with a bit larger ID. Changing one injector changes the flow to the others since they're all drinking from the same well. So, you will have some trial and error involved, but not too much. You might need to swap the injectors around a bit, but when you get the peaks to happen within a GPH, or better yet, 0.5GPH you should have a smooth running, LOP, gas saving, clean plugs, cool temps engine. This is all from memory... hope I remembered the high spots. Vince P.S. Make sure that your EGT probes really are in the cylinder that you think they are or it'll get real interesting. ======================== ============ ======================== ============ ======================== ============ ________________________________ Message 3 _____________________________________ Time: 02:59:13 PM PST US Subject: Rocket-List: Re: Update on Jim's Rocket From: "Don" To chime in here, Jims comment/dissertation on nozzle tuning is mostly correct. At peak EGT the engine is not necessarily running at peak efficiency. If you talk to people that have the equipment to actually measure efficiency, that is outfits that have dynos that measure air flow, fuel flow, torque, etc; not just a prop stand, BSFC and BSAC will give the efficiency of the engine. The point at which the EGT peaks is a specific fuel air ratio. This is what were trying to match. There are curves that show (Lycoming data) that even with different engines, naturally aspirated and turbo charge, the point at which EGT peaked was the same F/A for each engine and the F/A changed a specific amount to the change from peak EGT. This was again true of any engine they tested. Obviously the EGT number was different for the turbo charged engines and the naturally aspirated engines at peak EGT, but the F/A was the same. So a given change form peak EGT results in a specific F/A. For instance running 200 rich of peak EGT results in a F/A of .086. Peak EGT is a F/A of .065. This is pretty much true for any Lycoming engine, and probably most engines. So what Jim said is were adjusting the fuel flow to the cylinders air flow so that all the cylinders run at the same F/A. An important consideration when gathering the data is to not exceed 25MAP, keep the fuel flow above the point where the flow divider influences the flow division and let the EGT stabilize before changing fuel flow to get a new line of data. This means that if you use a data logger to capture data, slowing leaning the mixture control while gathering data will result in mostly worthless data, as the EGT does not respond as fast as the fuel flow indication. If you need more instruction on this process give me a call or email me off line. Don Read this topic online here: http://forums.matronics.com/viewtopic.php?p=138379#138379 ________________________________ Message 4 _____________________________________ Time: 07:59:47 PM PST US From: "Jim Stone" Subject: Re: Rocket-List: lean of peak injector balancing Great stuff, thanks Vince, Jim ----- Original Message ----- From: "Frazier, Vincent A" Sent: Friday, October 05, 2007 10:59 AM Subject: Rocket-List: lean of peak injector balancing > > > Jim, > > Read this. > > http://www.swaircraftappraisals.com/MeyersForum/Engine%20Info/Engine%20O > peration/Pelican's%20Perch%20Mixture%20Magic.htm > > It will tell you what you need to know. > > To balance your injectors only requires a few flights to get 'em pretty > close. More if you really want excuses to test fly. > > The injectors that came with your engine are most likely all the same > ID. But each cylinder has different flow patterns. IOW, the injectors > should be matched to the flow, but they aren't. > > Assuming that you have a 6 cylinder EGT monitoring capability, fly at a > fixed throttle and prop setting and altitude, start rich of peak and > begin leaning and record the fuel flow vs. EGT every 0.1 gph. Just > record the stuff near the peak EGTs, not all the way down from 28gph. No > need for that much data! You're just looking for the peaks. > > The first cylinder to peak is the leanest, and so on. When you get back > on the ground, call Don Rivera at Airflow Performance and tell him what > you found. He can send you new injectors of varying ID to replace your > existing ones. It's not that expensive and you'll easily save the money > back in fuel savings. > > Basically, you're going to swap the leanest injector for one with a bit > larger ID. Changing one injector changes the flow to the others since > they're all drinking from the same well. So, you will have some trial > and error involved, but not too much. > > You might need to swap the injectors around a bit, but when you get the > peaks to happen within a GPH, or better yet, 0.5GPH you should have a > smooth running, LOP, gas saving, clean plugs, cool temps engine. > > This is all from memory... hope I remembered the high spots. > > Vince > > P.S. Make sure that your EGT probes really are in the cylinder that you > think they are or it'll get real interesting. > > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rocket-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Rocket-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/rocket-list Browse Digests http://www.matronics.com/digest/rocket-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.