Greetings. I am an amateur petrolhead from Spain, and just have grooved the cylinder head in my '91 Opel Calibra 2.0i coupe:
Engine is a gasoline EFI 2 litre (122 cid) inline-four SOHC 2-valve:
I did many mods, intake and exhaust porting, chamber polishing, back-cut, stem-thinned and polished valves, fresh piston rings, new intake manifold, 10 ºC colder thermostat, etc. Then I milled the head from 10.0:1 to about 11.0:1 sCR and cut three grooves per chamber:
It has been a complete success. The engine now sounds and behaves like an inline-six of larger displacement. Oil and plugs remain clean. Never overheats under abuse, radiator fan is now unemployed. Can lug it at 2000 rpm uphill and pulls without hesitation, car is SUPERB now in hill climbing. Fuel consumption improved about a 15%.
I own another Calibra with a 223 bhp DOHC 4V turbo engine which will also receive grooves next summer.
Many thanks to Mr. Somender Singh and to Mr. Randy Naquin (Automotive Breath).
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Re:Grooved '91 Opel Calibra 2.0i coupe
Date: 2007/01/21 13:42
By: singh
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Karma: 4
Perfect Text Book Example ! Great job my Friends ! The doubt " Full " will be quite speech-less ! The " Swirl & Tumble " types will also realize some thing right is happening at the right time when the cylinder is the smallest to deliver this Torque !
" Idle " speed emissions alongwith no load constant higher RPM's spelt out in 5 gas readings will be the " Ice-ing " on the Cake of ICE " Combustion " ! Some call it ~ " Carbon Credit " !
sing !!!
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Re:Grooved '91 Opel Calibra 2.0i coupe
Date: 2007/02/07 07:43
By: John W. Kelly
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Karma: 0
Very nice workmanship!
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Re:Grooved '91 Opel Calibra 2.0i coupe
Date: 2007/02/22 17:50
By: TELVM
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Karma: 0
Thanks for your kind words gentlemen.
Recently a friend of mine has managed a fuel consumption of 5.9 litres/100 km (40 mpg US / 48 mpg UK) driving this car on a 100 km (60 miles) travel.
He was surprised as with his own car (same model and engine than mine, but unmodified), on the same trip and driving style, he only manages 7 l./100 (33.6 mpg US / 40.4 mpg UK). Thus 18% better mpg.
Although it was not my main goal, this fuel consumption improvement is a nice gift from the grooves and the CR increase.
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Re:Grooved '91 Opel Calibra 2.0i coupe
Date: 2007/06/22 11:07
By: TELVM
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Karma: 0
Dyno proof.
This engine left Opel Rüsselsheim factory in 1991 giving 115 CV/PS (= 113.5 BHP) & 170 Nm (= 125.5 lb.ft.) as standard.
In 2004, many years and many miles later, and well out of tune, I dynoed it with these poor results:
Just 107 CV (PS) = 105.5 BHP
Now, (with 16 years and 130.500 miles) after lots of tuning work plus grooved chambers, these are the results:
142 CV (PS) = 140 BHP 194 Nm = 143 lbs.ft.
Most definitely grooves do not harm :-) .
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