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Is it gonna be left at just the slits thought? Or is he gonna machine it away to make the chamber completly round....upto the marking on the face? Therefore there will be no slits when its finished perhaps, just a larger combustion chamber??
Good **** though, crack on.
 

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surely they slits, left like that, provide a way for the mixture to escape from the combustion chamber and generally a leaky combustion chamber. or am i not thinking straight here:

rodgerq
 

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i see your thinking rodg. if they channel charge into the plug on the compression phase why not back out on the fire/expansion phase.

having said that, it might actually help distribute the expanding force over the piston face
 

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Discussion Starter #27
not yet, will be up there this weekend though so should be able to get some snaps then
Thanks Lee, I really appreciate your attention to my concerns :beer: .



whats the cut for?
1) Enhance in-chamber turbulence at low and middle rpms, so improving combustion speed & quality, thus increasing torque and mpg. Detonation threshold is raised, with same octane fuel you can up the sCR or the boost without pinging. As a matter of fact the recipe for N/A engines is to raise sCR one half to a full point when cutting the grooves. EGTs are lowered (more complete combustion). Partial throttle AFRs can be leaned. Spark plugs remain clean (old dirty plugs are cleaned by the grooves).

2) Provide the flame kernel a straighter path to the piston ring under the squish pad zone, thus improving ring seal. Oil remains clean for longer.

A slit like that would also have several sharp edges = det hotspots.
A legitimate fear that I shared before testing, but the empirical fact is grooves raise detonation threshold.

if they channel charge into the plug on the compression phase why not back out on the fire/expansion phase.
They work both ways depending on the phase, compression or expansion.

having said that, it might actually help distribute the expanding force over the piston face
You can bet they do.


A Google search with 'singh + grooves' will render more information and feedback from users, from racing dragsters to heavy pick-ups.
 

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wow, that my learing for the day over!! nice info.
 

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had a look for the head today, one half has been thrown away, but the other one is believed to be at a mates house, so you may have to wait another week but i will find it and take pics!
 

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Nice to see someone trying something a bit different on the XE/LET

I would be worried about the effects at high RPM though, but can see the potential for benefits for economy.

Definately keep us updated with how you get on as its not something ive ever tried personally.
 

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ah, there she is, cheers for posting that brian:beer:
 

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ive seen a massive thread on this on an american volvo forum ( yes cutting edge of tuning lol ) but im buggered if i can find it again
 

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... i think the other thread with these modifications to kidney shaped 8v heads...
I run a small part time porting shop for the local drag racers, southern Louisiana. Nearly
100% of my work is on kidney shaped combustion chambers of after market heads for
American V8 engines.

With this design the grooves work extremely well. Allows higher compression on the fuel in
use, leaner air fuel mixtures and reduced ignition timing advance. The idea has caught on
so well I now groove nearly 100% of the heads that come into the shop.

 

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hmmm, I see the point of it now, after seeing it in an 2valve chamber. That's pretty ingenious.

Probably not much advantage on a 16v pent head though, as 0ddball says.
 

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...Probably not much advantage on a 16v pent head though...
I have zero experience with the pent roof design. Here's what someone else had to say
about his grooved pent roof:

mike_belben on speed talk said:
-first engine ive built that started and idled on what seemed like the very first spark on
initial startup. it was 35 degrees outside and it ran like the car was daily driven and shut
off just a moment before. normally takes me a few starter cycles to get them running
during warm weather, harder in the cold.

-during a very basic a/f ratio street tune, the throttle position log would show about 8%
tps angle while cruising. it would go to 11% and the car would accelerate as if it was
given a quarter throttle. the driver/owner was saying he thought something was wrong
with the cruise control, the car was taking off on him and he hadn't stepped on it yet.

i am convinced that grooves are the cat's ass with respect to cold starts, part throttle,
low load, economy, emissions and so forth. im anxious to build a test mule for myself and
see how it does on 87 octane with a good dose of compression, before and after grooves.
 
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