Section cut C20XE-C20LET head pictures? - Page 3

B8 GHY · 04-03-2007, 18:14

Quote:

Originally Posted by 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??

The multiple lines hve two purpose, 1) to direct charge towards spark plug during the compression stage. 2) to spread the flame on the combustion stage

Rs1 · 04-03-2007, 19:28

Quote:

Originally Posted by B8 GHY

The multiple lines hve two purpose, 1) to direct charge towards spark plug during the compression stage. 2) to spread the flame on the combustion stage

Isn't that what you said before

I know what its meant to do but i'm asking about the degree of accuracy in the actaul machining with regards to 1) The amount of cuts. 2) The angle of each cut.
Basicly what i'm saying is, if your wanting to direct the charge at the point of igniton then do exaclty that, the pics in this thread are......not exactly pin point accurate, will this make any differance? If the cut direction disects one or more other cuts will the flow of charge be disrupted at all? I'm only thinking along these lines as the combustion chamber design is quite critical in the first place, surly any mods should be done with the same attention to detail/accuracy as the original design??
Also how do we know the spead and spread of the flame front is not already at a optimal amount and what we would be doing by making the cuts isn't actually taking away from the end result....in my case maximum power??

Stefan · 04-03-2007, 19:44

In research, the grooves are milled. Best cutter would be a ball end. Depth starts off 0,5-1.0mm. Angle of groove depth is around 5 degrees. Sharp edges should be dressed. Other shapes have been tried to increase turbulence further or to induce swirl within the piston bowl or chamber.
Speed of the flame front is measured using special equipment and in all tests show an increase in flame speed. Power is always increased over base output.
Read the research papers if you are more interested.

Rs1 · 04-03-2007, 19:47

Cheers Stefan, need to read more into this.

B8 GHY · 04-03-2007, 20:02

Believe or not on the 2v heads it defo works, as most 2v heads have a squash band one or both sides. If you look at a normal 2v head you'll notice it has a D shape chamber, whereas a lean burn has a half a circle curve that points to the spark plug.

On the 4v head the spark plug is bang in the centre but it does two small squash band, which force all the charge to centre of the chamber but rob vortex(turbalance). The bigger the chamber the longer time it takes to for the flame front to spread...

top gear is on so I'll explain after

Rs1 · 04-03-2007, 20:08

Cool, with pics if you could.

automotivebreat · 05-03-2007, 02:32

When I first got involved with this several years ago I would cut one groove pointed
directly at the spark plug. I did about twenty engines this way then decided to copy
ideas from others and add a few of my own ideas. More grooves provide more benefit
especially when the squish area is large. I have reduced ignition advance requirements
as much as 6 - 10 degrees with the one groove layout

I use a 1.5 mm ball end mill to cut the initial groove. Finishing is done by hand with
a file opening the outlet into the chamber to 3 mm. I carefully check deck thickness
before deciding on groove depth, normality I cut 1-2 mm deep, deeper at the chamber.

This head is running on a low 9 second drag race car.

automotivebreat · 05-03-2007, 02:45

Quote:

Originally Posted by Rs1

I...the pics in this thread are......not exactly pin point accurate,
will this make any differance?

As I learn more about combustion I learn what effect in cylinder swirl has on flame kernel
development. Large scale flow (swirl or tumble) will stretch the developing flame, this is
good for combustion to a point , too much large scale flow can cause flame quench and
misfire.

With many of my current groove layouts I try to determine large scale flow and aim the
grooves into the area of the flame stretch as opposed to in the area of the spark plug.

Quote:

Originally Posted by Rs1

...how do we know the speed and spread of the flame front is not
already at a optimal amount and what we would be doing by making the cuts isn't actually
taking away from the end result...

A good indicator is ignition advance requirements for maximum torque. The lower the ignition
advance requirements are the more efferent the chamber and faster the flame speed is.

automotivebreat · 05-03-2007, 02:47

duplicate

B8 GHY · 05-03-2007, 20:17

Hello mr automotivebret... If an 4v chamber such as LET has a small squish area, how about grooveing the piston top?

It is nicely dome/dish!

Will this benefit the burn?

Rs1 · 05-03-2007, 20:47

Cheers automotivebreat(h)...lol. I thought you were angled slightly off point of igniton, now i'm begining to understanding why.

automotivebreat · 06-03-2007, 18:12

Quote:

Originally Posted by B8 GHY

... If an 4v chamber such as LET has a small squish area,
how about grooveing the piston top? It is nicely dome/dish!

Will this benefit the burn?

Yes, benifits can be found with piston modifications, got pictures?

Need pictures of piston and head.

automotivebreat · 06-03-2007, 18:26

Quote:

Originally Posted by Rs1

Cheers automotivebreat(h)...lol. I thought you were angled slightly off point of igniton, now i'm begining to understanding why.

By now you may have guessed, I occasionally step "out side the box".

Here's a few of my own layouts, designed to balance combustion temperatures and
enhance combustion in "dead" areas of the chamber.

The administrator decided not to leave room for the (h)... Tull, showing my age!

B8 GHY · 06-03-2007, 19:41

Whats heads are you showing us?

They have bloodly big squish band, I can see these heads will benefit loads with grooves.

As for pictures of a LET piston... I dont have any but im sure someone here does

automotivebreat · 06-03-2007, 23:45

Quote:

Originally Posted by B8 GHY

Whats heads are you showing us?

They have bloodly big squish band, I can see these heads will benefit loads with grooves.

Yes more grooves provide more of the same benefit.

Most of my work is on after market wedge heads for American made V8 engines, primarily
small block Chevrolet. Those seeking high performance utilize every bit of the available
squish area to their benefit.

The OEM would reduce the squish area and lower the compression ratio with a dished
piston. These pictures are from the production engine in my tow truck.

TELVM · 07-03-2007, 07:25

C20LET pistons:

C20LET chambers:

This is a turbo engine with 0.6-0.8 bar (8.7-11.6 psi // 17.7-23.6 inHg) standard max boost pressure.

**Nobbie** · 07-03-2007, 09:40

Do you not have to worry about possible 'hot spots', which may lead to det in a turbo engine?

philip2 · 07-03-2007, 10:12

looking at one of the last few pics, you have one where you have three grooves, going towards the valve....it looks aloost like your on the seat? couldnt that cause potential seat failure, after a certain time?

i may be wrong on this!!

spanishfly · 07-03-2007, 10:17

Enjoying this thread!

TELVM · 07-03-2007, 18:20

Quote:

Originally Posted by Nobbie

Do you not have to worry about possible 'hot spots', which may lead to det in a turbo engine?

The opposite is true, detonation threshold is raised.

Volvo turbo after grooving with this pattern:

Quote:

Originally Posted by Morten VJ from Turbobricks

After 2 weeks of driving with the groves.
This is my results.
I'm able to use the same boost pressure on regular, as i had with premium petrol before.
220 kpa with the same timing.

Fuel consumption.
Before 28 Mpg Imp. Best.
After 32 Mpg Imp and i'm still tuning.

AFR before at cruise 16-1
After at cruise 17.5-1 and nothing strange drivability problems.
I'm going to try 18-1 next week if i can burn it.

So far i'm Happy.

http://forums.turbobricks.com/showth...t=74370&page=3

Please notice that Volvo 2V open bathtub chamber with parallel valves is far more detonation sensitive than the C20LET 4V pentroofs.

automotivebreat · 07-03-2007, 18:25

Quote:

Originally Posted by TELVM

C20LET chambers:

If I were modifying this engine, I would groove the cylinder heads to direct squish flow
high into the roof of the chamber. The valve angles of this design creates a tall chamber,
this is undesirable for optimal flame travel. Benefits can be found by encouraging
additional mixture motion in the vicinity of the spark plug.

Additional mixture motion in the dish of the piston of this engine design will generate
improved combustion, to what extent I don’t know.

Quote:

Originally Posted by Nobbie

Do you not have to worry about possible 'hot spots', which may lead to det in a turbo engine?

The spark plug ground electrode glows red at sustained peak torque, next comes a
poorly seated exhaust valve. Most other surfaces provide sufficient heat sink to avoid
pre-ignition.

Quote:

Originally Posted by philip2

looking at one of the last few pics, you have one where you have three grooves, going towards the valve....it looks aloost like your on the seat? couldnt that cause potential seat failure, after a certain time?

i may be wrong on this!!

To an extent, I share the same concerns. I am a brave soul.

**Nobbie** · 07-03-2007, 19:05

Interesting!
But i suppose to find out the optimum, without trial and error you need to see where the current squish is happening, so you can 100% find the best angle for your grooves.

automotivebreat · 07-03-2007, 19:45

Quote:

Originally Posted by Nobbie

Interesting!
But i suppose to find out the optimum, without trial and error you need to see where the current squish is happening, so you can 100% find the best angle for your grooves.

Unfortunately we don’t have the resources needed to “see” what’s happening inside the active
cylinder. This forces us to use the work of others and fill in the void with our “imagination”.

TELVM · 07-03-2007, 19:46

Some possible groove patterns for the C20XE/C20LET head I'd suggest. From left to right, conservative to all-out.

Mongo · 07-03-2007, 21:03

Interesting subject

04-03-2007, 20:02	#55
B8 GHY MIGWeb User Join Date: Apr 2003 Location: NORTH LONDON Drives: Calibra Turbo iTrader: (1) Posts: 2,195	Believe or not on the 2v heads it defo works, as most 2v heads have a squash band one or both sides. If you look at a normal 2v head you'll notice it has a D shape chamber, whereas a lean burn has a half a circle curve that points to the spark plug. On the 4v head the spark plug is bang in the centre but it does two small squash band, which force all the charge to centre of the chamber but rob vortex(turbalance). The bigger the chamber the longer time it takes to for the flame front to spread... top gear is on so I'll explain after Last edited by B8 GHY; 04-03-2007 at 21:26.

07-03-2007, 09:40	#67
Nobbie Central Regional Coordinator / Moderator Join Date: Nov 2001 Location: Hemel Hempstead Drives: Mk3 Astra GSi XE iTrader: (3) Posts: 10,560	Do you not have to worry about possible 'hot spots', which may lead to det in a turbo engine? __________________ Central Region Co-ordinator Central Region Forums/Events

04-03-2007, 19:44	#53
Stefan MIGWeb User Join Date: Dec 2001 Location: Braintree, Essex Drives: Mk3 Astra iTrader: (4) Posts: 1,560	In research, the grooves are milled. Best cutter would be a ball end. Depth starts off 0,5-1.0mm. Angle of groove depth is around 5 degrees. Sharp edges should be dressed. Other shapes have been tried to increase turbulence further or to induce swirl within the piston bowl or chamber. Speed of the flame front is measured using special equipment and in all tests show an increase in flame speed. Power is always increased over base output. Read the research papers if you are more interested.

04-03-2007, 19:47	#54
Rs1 MIGWeb User Join Date: Dec 2004 Location: Newcastle Drives: LET...coming soon iTrader: (10) Posts: 7,803	Cheers Stefan, need to read more into this.

04-03-2007, 20:08	#56
Rs1 MIGWeb User Join Date: Dec 2004 Location: Newcastle Drives: LET...coming soon iTrader: (10) Posts: 7,803	Cool, with pics if you could.

05-03-2007, 02:32	#57
automotivebreat MIGWeb User Join Date: Mar 2007 iTrader: (0) Posts: 14	When I first got involved with this several years ago I would cut one groove pointed directly at the spark plug. I did about twenty engines this way then decided to copy ideas from others and add a few of my own ideas. More grooves provide more benefit especially when the squish area is large. I have reduced ignition advance requirements as much as 6 - 10 degrees with the one groove layout I use a 1.5 mm ball end mill to cut the initial groove. Finishing is done by hand with a file opening the outlet into the chamber to 3 mm. I carefully check deck thickness before deciding on groove depth, normality I cut 1-2 mm deep, deeper at the chamber. This head is running on a low 9 second drag race car.

05-03-2007, 02:47	#59
automotivebreat MIGWeb User Join Date: Mar 2007 iTrader: (0) Posts: 14	duplicate

05-03-2007, 20:17	#60
B8 GHY MIGWeb User Join Date: Apr 2003 Location: NORTH LONDON Drives: Calibra Turbo iTrader: (1) Posts: 2,195	Hello mr automotivebret... If an 4v chamber such as LET has a small squish area, how about grooveing the piston top? It is nicely dome/dish! Will this benefit the burn?

05-03-2007, 20:47	#61
Rs1 MIGWeb User Join Date: Dec 2004 Location: Newcastle Drives: LET...coming soon iTrader: (10) Posts: 7,803	Cheers automotivebreat(h)...lol. I thought you were angled slightly off point of igniton, now i'm begining to understanding why.

06-03-2007, 19:41	#64
B8 GHY MIGWeb User Join Date: Apr 2003 Location: NORTH LONDON Drives: Calibra Turbo iTrader: (1) Posts: 2,195	Whats heads are you showing us? They have bloodly big squish band, I can see these heads will benefit loads with grooves. As for pictures of a LET piston... I dont have any but im sure someone here does

07-03-2007, 07:25	#66
TELVM MIGWeb User Join Date: Nov 2004 Drives: Calibras 8V & Turbo iTrader: (0) Posts: 50	C20LET pistons: C20LET chambers: This is a turbo engine with 0.6-0.8 bar (8.7-11.6 psi // 17.7-23.6 inHg) standard max boost pressure.

07-03-2007, 10:12	#68
philip2 MIGWeb User Join Date: Nov 2005 Location: chester/n.wales Drives: class 7 corsa;) iTrader: (8) Posts: 3,109	looking at one of the last few pics, you have one where you have three grooves, going towards the valve....it looks aloost like your on the seat? couldnt that cause potential seat failure, after a certain time? i may be wrong on this!!

07-03-2007, 10:17	#69
spanishfly MIGClub Member Join Date: Oct 2002 Location: South London/ Surrey Drives: ACT Nova TBs &more;) iTrader: (35) Posts: 25,526	Enjoying this thread!

07-03-2007, 19:05	#72
Nobbie Central Regional Coordinator / Moderator Join Date: Nov 2001 Location: Hemel Hempstead Drives: Mk3 Astra GSi XE iTrader: (3) Posts: 10,560	Interesting! But i suppose to find out the optimum, without trial and error you need to see where the current squish is happening, so you can 100% find the best angle for your grooves.

07-03-2007, 19:46	#74
TELVM MIGWeb User Join Date: Nov 2004 Drives: Calibras 8V & Turbo iTrader: (0) Posts: 50	Some possible groove patterns for the C20XE/C20LET head I'd suggest. From left to right, conservative to all-out.

07-03-2007, 21:03	#75
Mongo MIGWeb User Join Date: Jul 2003 Location: Near Oxford Drives: E30 24v Turbo, BTCC iTrader: (0) Posts: 4,093	Interesting subject