Section cut C20XE-C20LET head pictures?

[DarrenH]

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

[TELVM]

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 .

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.

[vxlgsi]

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

[lee303]

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!

[TELVM]

Thanks a lot for your efforts Lee , I'll wait.

[chip]

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.

[TELVM]

I would be worried about the effects at high RPM though ... its not something ive ever tried personally.

I'm not worried. I have tried.

[Brian_S]

Its THICK... This is an image from the slice lee303 was on about...

[TELVM]

That's exactly what I needed! Thanks a lot gentlemen!

[lee303]

ah, there she is, cheers for posting that brian

[doggart]

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

[doggart]

http://forums.turbobricks.com/showthread.php?p=1025830

http://somender-singh.com/content/view/68/49/

[automotivebreat]

... 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.

[Brian_S]

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.

[automotivebreat]

...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:

-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.

[Stefan]

As allways an interesting topic. The grooves or "squish jets" are well proven to increase in-cylinder turbulence resulting in improved output, fuel economy and reduced emissions. Amount of turbulence is dependent on the squish area and groove design. Most research has been conducted with the piston crowns grooved/machined rather than the cylinder head. This allows easy assessment of different groove/jet designs.
Engines with this type of modification for fast burn can use less spark advance and tolerate lower fuel octane/high compression ratios without knock.
Research in this field has been conducted since the 80's.

Two research papers worth looking at:

SAE 1999-01-3664 "An Experimental Investigation on a New Squish Jet-Turbulence Combustion Chamber for SI Engine"

SAE 921545 "Combustion Chamber Design for a Lean-burn SI Engine"

[rc]

very intresting read!

[automotivebreat]

...Two research papers worth looking at:

SAE 1999-01-3664 "An Experimental Investigation on a New Squish Jet-Turbulence Combustion Chamber for SI Engine"

SAE 921545 "Combustion Chamber Design for a Lean-burn SI Engine"

Thanks Stefan, I was able to read paper 1999-01-3664 on the in piston squish jet
combustion chamber here’s the results:

Compared to the engine with the bathtub combustion chamber, the experimental
investigation shows that engine with the squish jet turbulence combustion chamber
gives better comprehensive performance. The combustion process shortens, the lean
burn limit extends. At WOT speed characteristics, the maximum power output
increases by 25.7%, the average specific fuel consumption decreases by 12.9%
and the average emissions of HC, CO and NOx decrease by 31.4%, 91% and 5.6%
respectively

[djivesp]

wow thats incredible !!
I may even try this on mine when i whip the head off next !!
Do you guys reckon its relatively 'safe' to do, i mean is there much room to **** things up ??

I have read that 8v volvo heads really benefit, pulling from low revs increases dramatically, never knew people did it on 16v heads !!

I assume without skimming the head, the added cuts lower the CR ever so slightly, which counter-acts any peformance benefit ?? Or does that depend too much on mapping&fuel type etc ?!

Another thing - how would a standard motronic dizzy xe feel about this - is it too small a change for it to worry about

[spanishfly]

Good gen, any more about

[automotivebreat]

I found this picture of a modified 4V chamber on the net, I was very impressed with
the idea and quality of workmanship. I decided to give something similar a try on a
2V small block Chevy chamber.


For best results the grooves are combined with more compression, leaner air fuel
mixture and sometimes reduced ignition advance.

[TELVM]

I found this picture of a modified 4V chamber on the net, I was very impressed with the idea and quality of workmanship.

That's a Mitsubishi Eclipse head. The artist is the friend of a friend of mine, 'Synchro' from Clubjapo . He's currently finishing engine reassembly after turbo conversion and tons of mods.

More pics of this head, click to enlarge:

[Rs1]

I love diy mods like this A couple of questions though....what denotes the placement, angle, depth and amount of grooves? Ive noticed on the 2v head the cuts are angled more so toward the inlet valve, then on the 4v head you have more cut on the inlet than the exhaust side.....is there a formula/resoning behind this?

[B8 GHY]

I love diy mods like this A couple of questions though....what denotes the placement, angle, depth and amount of grooves? Ive noticed on the 2v head the cuts are angled more so toward the inlet valve, then on the 4v head you have more cut on the inlet than the exhaust side.....is there a formula/resoning behind this?

Not inlet valve dude... This mod is trying to do two things, 1) pin point the charge towards the spark plug. 2) create vortex near TDC and speed up & spread frame front.

[Rs1]

OK, yeah i get that its trying to focus the charge toward the point of ignition but just of looking at those pics i was wondering if there was an exact science to the placement of the cuts. If you draw multiple lines through each cut you'll notice they dont actually line up with the point of igniton...there close but as there are both not angled spot on and in both cases(2v&4v) the disruption of flow down each cut will....nulify the effect??