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05-25-2001, 07:07 PM
#3
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And look at that piston weight. Holy Mac'l Batman! Dropping 300 g off of 631 g? Yow. No wonder they can raise the redline. That's some serious unobtanium. I'm curious about how the stock piston tops look more rounded. I would imagine the sharp-edged Spoons are more likely to detonate? UL?
05-25-2001, 07:49 PM
#5
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On the Spoon cams, everything I've _heard_ says they're designed for more midrange with no additional top end gains (some even say they lose a bit). Looking at the specs, that doesn't sound unreasonable. These things have similar lift and duration numbers as the Toda A cams for the B-series VTEC engines (Toda As run 250/240 on duration and 11.6/11.2mm on lift I/E) The A's usually peak out at around 8000-8300 rpm on a 1.8 liter engine. On a 2 liter engine, these sorts of specs should result in a power peak below 8000 rpm, although there are other factors that come into play. (while you're over there Greg, see if they'll tell you who makes their cams, odds are its Toda - and see if they'll give you stock specs!)
In terms of the pistons, I too would like to know how they lost so much weight since the shape is very similar. I'm guessing they use a different alloy. Penforhire, you're correct about the sharp edges. Any good engine builder would break all those edges before installing the pistons.
Which brings up a good point. Shiny stuff looks nice inside an engine, but it isn't always the best performing, particularly on headwork where some texture is often preferable (interesting anecdote I read somewhere, head porter said that even though a mirror finish didn't do a thing for hp, and might even hurt it a bit, his customers preferred it because it made them feel like they were getting more for their money, so he did it).
UL
In terms of the pistons, I too would like to know how they lost so much weight since the shape is very similar. I'm guessing they use a different alloy. Penforhire, you're correct about the sharp edges. Any good engine builder would break all those edges before installing the pistons.
Which brings up a good point. Shiny stuff looks nice inside an engine, but it isn't always the best performing, particularly on headwork where some texture is often preferable (interesting anecdote I read somewhere, head porter said that even though a mirror finish didn't do a thing for hp, and might even hurt it a bit, his customers preferred it because it made them feel like they were getting more for their money, so he did it).
UL
05-25-2001, 08:00 PM
#6
Registered User
Oh, and thanks for posting the cam stuff Richard, now I can estimate the stock cam lift (not duration yet).
The stock cam lobes measure (I/E) 36.533 mm and 35.928 mm on the big lobes. The Spoon cams measure about 0.1 mm more on each cam, which would equate to 0.004" at the cam. The follower ratio is probably around 1.5, so that would equate to around 0.006" at the valve.
On the small cam lobes, Spoon does almost nothing on the exhaust side (at least lift wise) changing the lift by
-0.016 mm and 0.012 mm at the cam. On the intake, they add 0.1 mm and 0.01 mm respectively. Of course, duration may vary significantly (and probably does).
So, stock cams look to have lift of around 11.4 mm and 10.5 mm at the valve. Rather small actually considering that the Prelude Type-S cams have over 12 mm of lift at the valve, albeit with smaller valves to begin with. Heck, even ITR cams have lift of 11.5 mm/10.6 mm at the valve. All this assumes that Spoon does not change the base circle at all. Also, with rollers in the F20C, Honda can run a more aggressive lift ramp, but even so...
As I've said elsewhere, lots of room for power with cams in this engine.
UL
The stock cam lobes measure (I/E) 36.533 mm and 35.928 mm on the big lobes. The Spoon cams measure about 0.1 mm more on each cam, which would equate to 0.004" at the cam. The follower ratio is probably around 1.5, so that would equate to around 0.006" at the valve.
On the small cam lobes, Spoon does almost nothing on the exhaust side (at least lift wise) changing the lift by
-0.016 mm and 0.012 mm at the cam. On the intake, they add 0.1 mm and 0.01 mm respectively. Of course, duration may vary significantly (and probably does).
So, stock cams look to have lift of around 11.4 mm and 10.5 mm at the valve. Rather small actually considering that the Prelude Type-S cams have over 12 mm of lift at the valve, albeit with smaller valves to begin with. Heck, even ITR cams have lift of 11.5 mm/10.6 mm at the valve. All this assumes that Spoon does not change the base circle at all. Also, with rollers in the F20C, Honda can run a more aggressive lift ramp, but even so...
As I've said elsewhere, lots of room for power with cams in this engine.
UL
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05-25-2001, 09:44 PM
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[QUOTE]Originally posted by ultimate lurker
[B]On the Spoon cams, everything I've _heard_ says they're designed for more midrange with no additional top end gains (some even say they lose a bit).
[B]On the Spoon cams, everything I've _heard_ says they're designed for more midrange with no additional top end gains (some even say they lose a bit).
05-26-2001, 12:26 AM
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Originally posted by S2K Fan
Does everyone in jpn button their shirt all the way up?
Does everyone in jpn button their shirt all the way up?
I saw that article in a S2000 book last time I was in Tokyo (about a month ago). I caught the shirt thing too, and thought "if all mechanics dressed like that...."
They wanted 2000 yen for the book & I think I'll buy it next time I'm over (next month). I'm sure it's got some great articles regarding tuning, although I'll just buy it for the pictures!
Cheers -
[Edited by ironwedge on 05-26-2001 at 01:31 AM]