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Old 08-10-2006, 07:39 AM   #1
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Default why the scoop in the button head for modified engines ?

hey guys
ive noticed in some of the modified engines lately that they put a small scoop in the bottom of the button head.

what does this do to the engine ?

i did it to one of mine and i noticed that i get a larger burn across the face of the piston. I guess it actually ignites more fuel ? i did notice a small increase in power across the top end
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Old 08-10-2006, 04:42 PM   #2
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witch way dos it face
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Old 08-10-2006, 04:47 PM   #3
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it points towards the exhaust port
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Old 08-10-2006, 06:18 PM   #4
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If im not misaken I think it helps the air/fuel mixture and allows to burn/be more efficient.


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Old 08-10-2006, 07:12 PM   #5
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This should shed a little light on the subject...

http://somender-singh.com/

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Old 08-10-2006, 07:27 PM   #6
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Default

Quote:
Originally Posted by mxwrench
This should shed a little light on the subject...

http://somender-singh.com/

BK
this is totally new to me... OMG this is so cool.
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Old 08-10-2006, 09:12 PM   #7
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lol and to think its old
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Old 08-10-2006, 11:46 PM   #8
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By adding this groove, how much is this affecting the compression ratio? What is the way to calculate the volume of the combustion chamber after this is done?
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Old 08-14-2006, 08:31 AM   #9
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Quote:
Originally Posted by GrandeGixxer
By adding this groove, how much is this affecting the compression ratio? What is the way to calculate the volume of the combustion chamber after this is done?
This groove definitely effects the head volune and therefore the compression ratio in general. The best way to counter this is to cc or measure the head dome volume with a liquid dispensed from a fine syringe with a range of 0-1ml. Using a piece of small plexiglass with 2 small holes cut, 1 for fluid inlet the other for air escape, and a little dab of grease for sealing. Place the plexi up against the head bottom (with plug installed) and fill the combustion chamber with fluid from the syringe till all the air is out. Measure the amount of fluid expelled from the syringe. Do the same after the modification. The difference between the two will be the amount of volume you will need to lower the head to regain the same compression ratio as previously had before the modification.

new clearance=new volume modified by removing shims to equal old volume where:

Pi*R^2*T=area of 1 shim (R= radius of the bore T=thickness of shim being measured)

Old volume-New volume= amount of area needed to be removed by shims

Note* keep in mind not to lower the head more than 0.3mm piston to head clearance or the piston will surely hit the head during running. And it still may kiss at 0.3mm depending on the condition of your con rod bushing.

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Old 08-14-2006, 09:47 AM   #10
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What would the pro's and con's be of this mod.
I saw above it can make engine more efficient but surely thats not all.
Mxwrench can you explain please.
Would benefits justify the mod for a club racer?
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Old 08-14-2006, 12:05 PM   #11
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Default Another...

Another nifty thing to do to heads is to shave them in order to place near the plug of the piston. JP Racing does this on their chamber heads (so everyone is warned about exchanging the chamber heads of a JP for a stock Nova one).

I'm doing them on some of mine engines, but going at a very small pace (0.1mm each step). For this thing a lathe is mandatory in order to keep the combustion chamber squared on the sleeve.

EDIT: You can see another use of the scooping on the link I've put. This time done on the pistons dome.

http://www.popularhotrodding.com/eng...05/0604em_emc/
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Old 08-20-2006, 06:19 AM   #12
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Default weird tune problem after scoop..

hey guys my engine had a weird day of running today..
it did 3 qualifying heats with crazy power running no more than 95-100 degrees celsius (os vz-r .21)

then in the final it blew 2 plugs straight away. the engine came out fast as hell for about 2 minutes then just went slower and died. this when it blew the plugs. we tried to go richer on the top end but it blew the second plug to..

now im wondering if the turboscoop has made more volume therefor maybe i shuld remove a shim ?

what do you think

thanks..
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Old 08-20-2006, 06:48 AM   #13
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Quote:
Originally Posted by mrgsr
hey guys my engine had a weird day of running today..
it did 3 qualifying heats with crazy power running no more than 95-100 degrees celsius (os vz-r .21)

then in the final it blew 2 plugs straight away. the engine came out fast as hell for about 2 minutes then just went slower and died. this when it blew the plugs. we tried to go richer on the top end but it blew the second plug to..

now im wondering if the turboscoop has made more volume therefor maybe i shuld remove a shim ?

what do you think

thanks..
Take the engine apart and check for damage. Usually whan an engine starts to wear badly the internal parts can rub and create microscopic particles of aluminum. This aluminum gets on the glow plug filiment and will cause it to blow rather quickly. Even repetedly.

I'd especially look for wear on the conrod (big end and small end), crankshaft, and backplate as this is usually the suspect area.

Many times an engine will run it's best right before it blows up, so this is definitely a possibility. Take it apart and let us know how it looks inside.

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Old 08-20-2006, 06:55 AM   #14
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yeh i will
ill take it apart tomorrow and see how it looks..
could a lean low end cause plugs to blow?
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Old 08-21-2006, 03:25 AM   #15
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MXwrench:

You also need to take the squishband into consideration. You will get ignition knocking if just lower the combustion chamber to regain the right compression ratio.

You need to change the whole comustion chamberof this is to be done right.
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