[Diy_efi] direct injection

James Holland j_holland
Tue Oct 4 08:21:21 UTC 2011


I just had a quick Google, it is a rather strange looking piston:
http://www.hotrod.com/techarticles/engine/hrdp_0909_direct_injection_guide/photo_07.html
?
regards
James




2011/9/23 Phillip Kuhn <pmkls1 at yahoo.com>




I know that this topic has gone kind of cold, but I spoke with a field engineer that came to the shop today and he had some information I thought I would share with you. When I told him about your inquiry and the information that I had been unable to obtain he also had some additional information that I was unaware of as well. He told me that the injector placement was critical and that was one of the major obstacles that took GM engineers some time to overcome. Evidently, the location of the injector in the combustion chamber and more importantly where the spray is focused is crucial to the engine performing properly. Since they were modifying existing?engine designs with the intention of making as few major modifications to the cylinder heads as possible it was quite difficult to get the injectors spraying fuel into the right part of the cylinder for the engines to run right. As a matter of fact I have replaced a cylinder head on a DI 3.6 v6
 recently.?I noticed the injector actually came in through the side of the combustion chamber ( this was probably due to the only available location to mount the injectors ) and the top of the piston and combustion chambers were very specifically shaped. They were profiled so that the fuel spray focused into a recess in the middle of the combustion chamber directly under the spark plug. I am guessing that this was to get the flame to start in the middle of the chamber and spread outward in a controlled manner. Anyhow, I thought this information was important enough to pass on. Don't get me wrong, I would love for you to successfully utilize a DI system on your project and anyone else for that matter. I just want to provide enough info so as to aid in this being completed successfully without running into so many obstacles that anyone who attempts this will not give up. I also don't want to see someone ruin a possibly rare and/or expensive cylinder head
 just to mount the injector and find out that the rest of the project is too difficult to complete. Good luck and feel free to ask anymore questions that come to mind.
?
Phil




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