just noticed that a guy i was talking to on the teamswift.net forum lives in SLC too.
he just ordered a custom ground cam for his 99 metro 1.0 from a machinist who's also a teamswift member. it's ground specifically to increase fuel economy - the machinist makes several different profiles (turbo 1.0, performance 1.0 n.a., and economy 1.0).
i was thinking of doing the same thing next spring/summer, but i'll gladly let this guy do the research for me
he's scangauge equipped, understands the importance of controlled testing and said he'd get back to me with the results once he's got it set up.
That is awesome! How much does he charge to do a stock cam? Hmm, very interesting, I wonder if something like that can be done in conjunction with vtec-e and the whole changing cam profiles thing...Can't wait to here the results.
price this guy paid for the 1.0 economy cam was $165 - $205 for the cam and a new cam sprocket to adjust its timing, incl. a $40 core charge you get back if you send him your OEM cam after the swap (he uses the original to re-grind for the next guy).
not sure if the price is set - it's a new kind of a new thing for him.
not sure if he does custom work, but you can check his page here:
Would anyone mind explaining a little about this mod to the engine illiterate?
caveat: i'm no expert on cams/valve timing - learning as i go. please all, feel free to jump to this thread with corrections. last thing we need is more psuedoscience presented as "fact" for all cars in all situations...
1) start with the assumption that valve lift & duration is a compromise between low and high rpm performance. the manufacturer tries to find a sweet spot somewhere in the middle which satisfies everyone.
2) one way around this compromise is to offer variable valve timing, with both low rpm efficiency and high rpm power - e.g. vtec, vvti.
3) the economy cam this guy makes apparently shifts the powerband lower - it sacrifices high end performance for low rpm performance
4) the cam is machined for lower lift and shorter duration. the result is slightly higher compression, because normally, the intake valve is not fully closed as the piston begins its compression stroke.
evidence of #4 comes from a compression test done on a 1.0 motor before & after the cam swap...
A hot compression test on the engine before the MPG cam:
#1 - 182, #2 - 178 and #3- 180 lbs.
The same test after the new cam was installed: The hot compression test was:
#1 - 195, #2 - 185 and #3 - 190 lbs.
The compression increase is probably because of shorter duration which should help the low and mid-range power. (source)
the idea is similar to adding a turbo. more power means you can shift up at a lower RPM and improve MPG through reducing your average RPMs (lowering internal friction). the tester's anecdotal support for this is that he can do 2nd gear "roll-outs" from stop signs much easier with the MPG cam than with the stock cam.
the million dollar claim:
in 5 tanks of fuel, the economy cam alone showed an improvement of 8%-9% in fuel mileage. (source)
however tank-to-tank testing is fallable, so you have to take that claim with a very large grain of salt. i personally wouldn't accept it as "proof" of the cam's effectiveness.
e.g. if he did the cam swap in the spring, his next 5 tanks would have been affected by increasing ambient temperatures - fuel economy at 70F can easily be 8% better than fuel economy at 50F, all else being equal.
and guess what - i just checked the dates on the postings i quoted above and the swap reported in march 05 and the "results" were posted in may 05.
so i'll reserve judgment on this until i hear from the SLC metro owner who is scangauge equipped and who can measure results more accurately.