Calypso wrote:1. Compression stroke burn improvement: Hi speed jet in the middle of the chamber would cause 2 contra rotating swirls (intake and exhaust side) that improve the burn rate and make it more complete by throwing gas into the flames. Actually this mod would likely allow more compression by swirling the unburned detonation sensitive mixture from the area cylinder wall side of the intake valve. (based on the thinking that better ionized exhaust side mixture tends to burn first and compress the end gas to the intake side)
I don’t claim to be an expert on the topic of combustion but I have given this a lot of thought. The altered fluid flow ATDC of compression likely feeds the advancing flame front and creates additional mixture movement and improved squish flow placement. The fuel air mix contains 70% nitrogen. The additional movement and placement better exposes the air fuel to generate a hotter faster flame that burns more completely. If this is indeed the case it would explain the clean running oil and plugs.
I have found that the grooved engine is more detonation resistant; I’m running 10:1 compression in my modified tow truck. I agree with Calypso, swirling the unburned detonation sensitive mixture from the area cylinder wall side of the intake valve is the key.
Calypso wrote:2. exhaust stroke idle improvement. This is based on how I think reversion behaves. Most of the flow in the ports at low lifts is along short turns. Hi speed jet near intake short turn causes local pressure minimum pulling mixture to the chamber at overlap. Pressure recovery from the jet at plug side causes a local hi pressure region at exhaust port short side inhibiting exhaust flow into the chamber.
This I haven’t given much thought but I think you are on to something. When I ask about a second groove, Somender recommends one pointing directly at the exhaust valve on the opposite side of the chamber from the first groove.
Calypso wrote:#2 also would explain why bigger quench distance would improve burn: Low pressure area at groove would be able to more easily evacuate the unburned mixture from quench pad area.
Here we agree again. I have found with the grooves there is an advantage to open up the quench distance. I’m very interested to see how the burn pattern looks on the modified engine. When you look at the last picture I posted the burn pattern was very incomplete.
Calypso wrote:To me it makes sense. I think I'm going to try it... with couple of obvious improvements.
Please communicate obvious improvements. I’m grooving two to three sets of heads a month and I’m willing to try improvements and communicate results.