Why is there so much quench area? Honda is known to make on of the best n/a engines, but why is'nt the quench area better (thinner)?

Like my excellent graph shows more advanced ignition is needed to get all the a/f mixture to burn with such an quench area, cause the clearance between piston and combustion camber is too big, so there is burnable mixture everywhere. Would the clearence be thinner, there is no chance to get burnable mixture in the thinn space. When you would mill the head of, the mixture will be only consentrated in the middle above the piston, which would give more power and less chance to knock.

My tuner said, Honda did this, to give the engine tuners some improvements get more power out of the B18C.

 

I would assume that there is a large amount of quench area in the b18c motor to allow for better swirling, and thus a more evenly distributed fuel / air mixture. The quench area is one thing that engine builders are constantly fiddling with, and it will be different for N/A versus forced induction. A large quench area would probably be more detonation resistant because the heat from combustion has a better chance to spread out evenly, instead of being concentrated in one area. This is all speculation of course, I would suggest that you do more research before attempting to change something as important as this.

edit: I think your tuner is talking out of his ***, as I seriously doubt honda would change thier combustion chamber shape to help tuners "get more power"...


[Modified by Philly_NBP_R, 10:12 AM 12/18/2002]

 

found this link:
http://www.theoldone.com/archive/quench-area.htm
"When properly designed, the quench areas can have a tremendous effect on the quality of combustion, and allow higher compression ratios, and due to this they are considered "artificial octane" by scientific types.
Bottom line is "properly designed, quench is good". "

 

Somehow, I don't know why, I trust Honda that they know what they are doing.....

 

This brings up an interesting question: is the combustion chamber for the ITR shaped different from the GSR? I know there are a lot of differences between the engines, but there are also a lot of similarities.

As is frequently pointed out, major auto manufacturers must design their cars using a whole slew of compromises. When designing an engine, they usually must consider things like economy and emissions before raw power. Could it be that they didn't want to touch that aspect of the design when creating the C5? In which case, the combustion chamber would be a compromise shape and the quench area could be designed more for emissions than raw power.

I did a quick search and found a few references to reshaping the combustion chamber, but most of them were related to FI. Is anyone here familiar with any work that's been done with reshaping the combustion chamber for improved NA performance?

 

Yes, the combustion chamber for the B16/B18CR heads are shaped slightly differently than that of the B18C1 in a GS-R.

The B18C1 combustion chambers have more quench area and are a couple of cc's smaller. The C1 head also has a different shape to the intake ports.

 

The quench areas aid in keeping detonation to a minimum. You need that in a high compression N/A engine and in a turbo engine alike.

That is one of the reasons the new QR25 motor that Nissan has in the Spec-V Sentra most likely wont take too well to much boost. It has almost no quench area, while something like the SR20DET has plenty.

Kenton

Edit - I cant spell for crap


[Modified by 2.2, 11:53 AM 12/18/2002]