That is the higher compression helping to tame large cams. Engine may idle smoother due to the guy detonating before the grooves. I know one article states that until he cut 2 additional grooves per cylinder he got severe detonation

 

So saying that it calms down the rough idle of a large cam is completely incorrect, it's just a band-aid for a badly designed motor combo.

 

So if this does improve effiency of combustion, why do head porters not do it, especially if it has no adverse effects on dyno results? I'm porting my heads and IF it could help squeeze an extra 1 or 2 mpg out of my F13 cammed car, it sounds like a good idea.

 

Pictures look good, and theory is sound, but I would not do it to a customers motor based on information found on the internet from an unknown source. It would require some r&d before actually using it. For the kind of motors I do, it never comes down to the extra 1-2hp or mpg so I don't plan on trying it.

 

A big reason is ya haven't gone to the porters that do it and it has not been well advertised. It is also not a proven thing.

M1,
There are guys down here that are using it. One guy when he stopped the detonation he found so much low end the car had to be adjusted to get it out of the hole.

 

Sorry if i was a little vaque but on the last link the guys writes

"The engine will idle smoothly to below 500 rpm, but is limited to 650 rpm by the ECM. I can idle it while driving in 2nd gear below 500 rpm without it complaining too much."

Would this be caused by better low rpm flame propogation?

I have a stand up ski from the early 90's that i ride and tune alot. Manual states to set the idle to 1250 rpm. Mind you it is a 2 cycle but i would love to bring the idle down some and i just cant get the thing to idle right bellow 1100. i was wondering if this might help.

 

How can a more efficient burn not be accompanied by greater power?

 

I wasnt aiming for MPG but since my buildup is for my DD, if there is an easy way to add a little more effeciency I'd like to. Since I'm upping my compression ratio a bit from decking the heads, I think I'll try it and let you all know in a month what the dyno results are.

 

Concurrent discussion that gets into this deeply on another site. Some of you may be following that one as well but for those that have not here goes.
http://www.speedtalk.com/forum/viewtopic.php?t=3652

 

The first rule of speedtalk is you do not talk about speedtalk.

 

That is Soooooo CORRECT.

 

LOL - I figure if guys can follow what is being said over there and understand it, then there's no harm.

 

Somebody might catch a snag and run with it.

 

Well larger cams are usually happier running rich at low rpm. When you lean them out you get that stupid off idle hesitation.

Maybe this modification burns more efficiently at idle and takes away some of the problems?

 

yea, i was thinking about that too, Gripenfelter

and also cold starting with a chokeless carb, gotta pump her to get her to fire, then if ya shut down without it warming up sometimes cheap plugs foul,

maybe this efficiency thing could help make larger more aggressive cams more streetable, maybe less warmup time, maybe one less pump on the accelerator to get her fired up, maybe even be able to let my foot off the pedal earlier while i warm it up?

on the other hand, i'd be worried that the thing wouldnt run at low idle with my cam anymore lol, it's interesting, gotta get some surface flow and hotspot data on that chamber surface.

but what i really wanted to post about is in the first link of the original post i believe, the guy grooved the walls of the intake port, it looks like almost THE WHOLE THING!! now i understand scuffing the port, but this looks like it would turn the entire flow of the port into the equivalent of 'whitewater rafting', i doubt it would flow at all at high rpm