Urgent Cam Specs NA BP 1.8 - Page 2

Drift Thorpey · 08-11-2011, 05:20 PM

I take it the specs were in order (intake then exhaust)?

Cheers fella, much appreciate the numbers.

Orion · 08-11-2011, 05:38 PM

Quote:

Originally Posted by tc3_racer_001

What does the base number mean?

Sorry I'm a total noob

Means base circle size. It will be important when determining the size of the shims

You will not that the better cams have a smaller base cirlce than the OEM base circle, which generally means regrind.

project.r.racing · 08-11-2011, 05:48 PM

Kinda...

Base circle is were the valves sit when closed.
Lift is how big the lobe is that moves the valves.

In some applications if you increase the size of the lobes (ie more lift), then the lobe will foul with the head. So by making the base circle smaller, then the intial start point is further from the head.

Read this:-
http://www.maruhamotors.co.jp/miata/parts/na8fcam.html

---

Any increase in duration/lift is gonna increase fuel usage. You put more air into the eninge. then the O2 sensor is gonna go, "Hey, I'm running lean here, add more fuel you mofo ecu!" More fuel + more air = powaaahhh!

TheMAN · 08-11-2011, 08:49 PM

fuel economy changes depends on driving conditions and/or the cam profiles
a mild cam setup that increases duration and overlap slightly helps improve exhaust scavenging while the car is cruising, which improves fuel economy... but as with any more aggressive cams, it reduces off the line power/torque and thus fuel economy suffers if you drive in heavy traffic constantly

now obviously, when you actually drive the **** out of the car, the power increases from the cams obviously will cause the ECU to add more fuel to make up for the added air.... however, if your driving normally is mundane, a well matched set of cams with exhaust can improve fuel efficiency greatly... I know this from experience

08-11-2011, 08:49 PM	#24
TheMAN Senior Member Join Date: Feb 2010 Location: USA Car: . Posts: 2,623	fuel economy changes depends on driving conditions and/or the cam profiles a mild cam setup that increases duration and overlap slightly helps improve exhaust scavenging while the car is cruising, which improves fuel economy... but as with any more aggressive cams, it reduces off the line power/torque and thus fuel economy suffers if you drive in heavy traffic constantly now obviously, when you actually drive the **** out of the car, the power increases from the cams obviously will cause the ECU to add more fuel to make up for the added air.... however, if your driving normally is mundane, a well matched set of cams with exhaust can improve fuel efficiency greatly... I know this from experience __________________ Protege FAQ, the best 323/Protege/Mazda3 resource enjoyed worldwide for 10 years Last edited by TheMAN; 08-11-2011 at 08:52 PM.

08-11-2011, 05:20 PM	#21
Drift Thorpey Junior Member Join Date: Aug 2011 Location: Radelaide's WestSide Car: 89 Astina BG DOHC Posts: 172	I take it the specs were in order (intake then exhaust)? Cheers fella, much appreciate the numbers.

08-11-2011, 05:48 PM	#23
project.r.racing Senior Member Join Date: Sep 2004 Location: n/a Car: n/a Posts: 10,929	Kinda... Base circle is were the valves sit when closed. Lift is how big the lobe is that moves the valves. In some applications if you increase the size of the lobes (ie more lift), then the lobe will foul with the head. So by making the base circle smaller, then the intial start point is further from the head. Read this:- http://www.maruhamotors.co.jp/miata/parts/na8fcam.html --- Any increase in duration/lift is gonna increase fuel usage. You put more air into the eninge. then the O2 sensor is gonna go, "Hey, I'm running lean here, add more fuel you mofo ecu!" More fuel + more air = powaaahhh!