AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 25,809
- Reaction score
- 13,117
I'm with YellowRose who doesn't much like Hydraulic rollers.Does the numbers also look better AJ?
I have a FTH (Flat-Tappet/hydraulic) 230* cam in my 367 and it makes great WOT power. But it is impossible to make good fuel economy at a cruise rpm of 2240. A hydraulic roller will only be worse, with it's longer acceleration ramps, stealing duration from the power-stroke, and giving it to overlap.
If fuel economy is important to you, rather;
If fuel economy was important to me;
and I was looking to cruise at 2250ish rpm,
there is no way I would choose a performance Hydraulic Roller cam.
I'm also with Wyrmrider who doesn't like cams for which he cannot compare rates of lift, such as the ever secretive Hughes cams. and I'm also with
Rumble who knows his chit too, and who has already published his minimum size.
Here's the thing; the more overlap your cam has, the faster you will have to spin the engine at cruising-speed to help prevent that cycle from pushing raw fuel thru the exhaust. Ok, so; you can overcome that part.
But what cannot be compensated for, is the very short power duration of hydraulic roller cams, that release high-energy exhaust gasses into the pipes. It might seem trivial, but consider that every mile you drive at 2250 rpm=60 mph, your engine is sparking 9000 times. Every mile. It doesn't take much of an imagination to see that, for fuel economy, any energy not going to the crank, and/or any fuel passing thru the engine unburned, and/or any gasses still burning when they leave the chamber; is serious business. Consider that 9000 sparks per mile,at 60mph, is over half a million sparks per hour.
Lets say that on every one of those cycles, just 1/20 of a gram of fuel goes thru the system not contributing energy to the crank. That comes to 450grams per mile!. Or for Americans that is 1 pound of gas.. One pound .... per mile..... that contributed nothing to energy production. At 6 pounds per gallon, 1 pound is 1/6 of a gallon or 22 ounces. You know how many guys could get drunk on 22 ounces of whisky per hour? Me either, I quit doing that in 1993.lol.
To put that 1/20th of a gram into perspective; Lets say your car makes 15 mpg with that stroker. Had those 22 ounces contributed their share, that 15 mpgs would have been 18.1 mpgs
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