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Old 09-18-2008, 09:36 AM   #21 (permalink)
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Quote:
Originally Posted by Geebee View Post
The data and anaylis in the second pdf don't seem to agree.
Look at the HP rating through out the range and the non grooved head is almost always higher sometimes dramatically.
Please notice the graphs in the second pdf aren't horsepower curves, but in-cylinder peak pressure curves.

Less peak pressure at the right moment of piston travel can make more torque than higher peak pressure at the wrong moment of piston travel.


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The testing was also flawed because the data on combustion chamber size is smaller for the grooved head.
Two cylinder heads were used. The highest difference in combustion chamber volume is 3.3%. No two cylinder heads of same type are identical due to casting and machining tolerances, see that the intake runners had larger volume in the non-grooved head. I don't think that's enough to discard the experiment as dramatically flawed, but that's just my opinion.

He could have used just one and the same cylinder head, first without grooves, then grooved. But he didn't.

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Old 09-18-2008, 10:58 AM   #22 (permalink)
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Thanks for the link, TELVM. I downloaded the file and am still reading through it.
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Old 09-18-2008, 11:59 AM   #23 (permalink)
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Well, I went over the pdf files, looked at the bsfc values and I have a problem with the findings. I have a hard time believing that the grooves will lower bsfc at low/medium loads and rpm by 10 to 20%.
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Old 09-18-2008, 01:15 PM   #24 (permalink)
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I put grooves in the chambers of my Calibra 2.0i 8V engine seeking not better fuel mileage, but resistance to detonation and more horsepower (I raised CR from 9.2:1 to 11.0:1, plus several other pinging-prone mods).

Then to my amusement I found that the fuel consumption had decreased at partial throttle. To me, more HP at WOT and more mpg at partial is a fine deal. But that's just me.



This forum is also about lower fuel consumption ...

mpg Research • Index page

... and they have a sub-forum dedicated to the grooves:

mpg Research • View forum - Somender's Grooves


Here's a thread on the subject at the TeamSwift forum (Suzuki Swift = Geo Metro):

TeamSwift • View topic - Combustion chamber grooves=better economy??
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Old 09-18-2008, 06:15 PM   #25 (permalink)
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Quote:
Originally Posted by TELVM View Post
Please notice the graphs in the second pdf aren't horsepower curves, but in-cylinder peak pressure curves.

Less peak pressure at the right moment of piston travel can make more torque than higher peak pressure at the wrong moment of piston travel.




Two cylinder heads were used. The highest difference in combustion chamber volume is 3.3%. No two cylinder heads of same type are identical due to casting and machining tolerances, see that the intake runners had larger volume in the non-grooved head. I don't think that's enough to discard the experiment as dramatically flawed, but that's just my opinion.

He could have used just one and the same cylinder head, first without grooves, then grooved. But he didn't.


I was refering to the tables/charts showing brake horse power and corrected horsepower as stated in the test result units.
As for the differing combustion cambers, it stops any decompression effect from showing and even with that the grooved head HP dropped.

Last edited by Geebee; 09-18-2008 at 06:25 PM..
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Old 09-19-2008, 08:25 AM   #26 (permalink)
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My apologies Geebee, I'm not a native English speaker and didn't understood your words correctly. You are right, the grooved head made less power at WOT in this experiment.

Did you also see that the grooved head made more power, with better thermal efficiency and better brake specific fuel consumption, at partial loads? Also the EGTs were lower at all conditions.


I'd like to remark that in this test the grooved head was standard compression ratio. To maximize their effects the grooves should be accompanied with a raise in CR.

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