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Old 05-23-2013, 11:18 AM   #1 (permalink)
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"Downgrade" my cam for more MPG?

My engine offers two factory cams... the "95" version and the 96+ version. The 95 is known to be a bit more aggressive and gains ~4 horsies. The difference in the intake lobe, exhaust is the same. I originally tried to get my hands on a 96+ cam before rebuilding, but time wasn't on my side. Now, I'm considering swapping one out, if I should stumble upon one again.

Here is the difference in specs for those gear heads who would be able to use this information:



So I guess the question is this: Is there any noticeable gains in going back to the original cam? Getting the cam and the effort to swap them isn't the issue... I just don't know if any MPGs can be had from this swap. The original reason they changed the cams after 95 was to give better idle quality (so I've read). Since I draw the line of my knowledge with these cams, I figured it would be worth asking you guys.

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Old 05-23-2013, 12:16 PM   #2 (permalink)
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The camshaft in the more efficient Metro XFi was different from the garden variety Metros in that it had lower lift & less duration. That favours low RPM efficiency at the expense of high RPM performance -- the torque curve is shifted lower, and peak horsepower is reduced.

I'm no cam expert, but based on those facts, if you can get a cam with lower lift & duration, I'd bet it would help.

FYI: I put an XFi cam into my non-XFi engine: http://www.metrompg.com/posts/xfi-cam-swap.htm

I noticed a marked difference in low-RPM driveability. The car became much happier to upshift and cruise at lower RPM. I didn't attempt to A-B test it, though.
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Old 05-23-2013, 12:29 PM   #3 (permalink)
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Cool. I kind of figured lower lift/duration would be better for lower RPM, since that's kind of how V-TEC works to increase low end performance. I'll have to shop around for a good deal on said cam, as well as an adjustable cam gear to further make awesome low end torque.
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Old 05-23-2013, 12:29 PM   #4 (permalink)
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PS: also, I'd call it a cam "upgrade"
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Old 05-23-2013, 12:43 PM   #5 (permalink)
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I guess I'm used to dealing with the gearheads who are after whp, not mpg. I should know to breath a little easier on this forum... lol
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Old 05-23-2013, 01:32 PM   #6 (permalink)
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Old 05-24-2013, 03:08 AM   #7 (permalink)
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Quote:
Originally Posted by NoD~ View Post
Cool. I kind of figured lower lift/duration would be better for lower RPM, since that's kind of how V-TEC works to increase low end performance. I'll have to shop around for a good deal on said cam, as well as an adjustable cam gear to further make awesome low end torque.
With the better low-end torque, there's a lesser need to keep higher RPMs, therefore reducing the fuel consumption
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Old 05-24-2013, 03:21 AM   #8 (permalink)
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At this point, we would judge you for not going through with it!

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