Blackfly XFi? Geo Metro economy cam shaft swap! Update: swap completed
 

[ A full report of this thread appears here: International heart transplant: the Blackfly gets an XFi cam - MetroMPG.com ]

http://ecomodder.com/forum/attachmen...1&d=1512066213

Thanks to a certain website overlord who shall remain nameless, I now have in my posession a camshaft from a Metro XFi (year and mileage unknown).

This cam will find its way into the Blackfly's engine compartment in the not too distant future, replacing the extravagantly wasteful OEM cam that came with the car. http://www.gassavers.org/images/smilies/wink.gif

Metro aficionados know that the XFi cam was one of several mechanical differences between that model and the garden-variety Metros, which cumulatively gave it a significantly better EPA rating:

How much of a difference the cam will make by itself is anyone's guess.

I'd really like to do some A-B-A to get an actual number, but cam swaps at the side of the road on a hot engine may be problematic. Besides, the return of testing season is 3 months away at best. So I'm just going to install it and revisit the experiment question later.

Won't the car also need an XFi computer?

No. It's a mechanical thing: the different cam profile - lower lift & duration - raises the cylinder pressure and shifts the torque peak downwards, so less throttle is required at low RPM.

It lowers the XFi's HP rating from 55 to 49, but the torque value is unchanged (the RPM at which the max occurs is lower). (EDIT: The cam alone may not be the HP limiting factor - that could be ECU-related.)

A number of people have done similar swaps including GeoMetry on this forum, and 3 that I know of on teamswift.net. I don't think any of them also swapped ECUs.[/quote]

Reconsidering the ECU issue...

One thing the XFi ECU may do to compensate for the different cam profile is adjust timing differently. Higher cylinder pressure would mean more chance of pinging under high load / high temps. So a guess is there may be less advance in the XFi ECU under those conditions.

Something to keep an eye on. Or an ear.

Here's some more info about the XFi cam from the member who makes the "economy grind" cams:

What that tells me is that in addition to shorter lift & duration, the XFi cam timing is advanced compared to stock.

Note that I've swapped transmissions and have a much taller final drive. So the cam swap with lowered torque peak should be a better match to the gearing I have.

The Actual Unit - 6 lobes of fury:

http://images6.theimagehosting.com/a...xfi-cam.th.jpg

I'm itching to get this done, but it'll have to wait until winter retreats a little. It's -22 C / -7 F outside. That's frostbite weather, not Blackfly fixin' weather.

One potential effect of raising cylinder pressure too high is pinging/detonation.

RH77 offers some detailed info about the implications:

March 11/07...

Swapped cams this afternoon. Warmest day of the year so far: + 6C, sunny & calm. OK for driveway tinkering!

Haven't driven it yet (just started it up - sounded the same). I'll take it for a spin after supper and will report back...

How, exactly does changing cam lift & duration improve low end torque?

I'll be the first to admit I'm no a cam expert. Everything I've learned, I learned online... recently. Such as:

• Lower lift & duration, reducing overlap, and advancing cam timing for more low end torque has apparently been understood for a long time.

• Here's a description of an "economy cam" (designed like the XFi's to shift the torque peak to a lower RPM) in a special "efficient" 1960's era Olds 4-4-2 engine. It has the same effect: lower HP, shifted torque peak (so you can operate the engine more usefully at lower RPM), better fuel economy:

...

I can't defend the decisions of the engineers who made the XFi cam. But the proof is in the pudding - the XFi gets better fuel economy. And I suspect the laws of physics were respected.

A Metro expert suggested it would be perhaps a 30 minute job. It took me maybe 2 hours. It'd take me 30 minutes to do again though http://www.gassavers.org/images/smilies/smile.gif

1. I cut my timing belt cover with a dremel so I could remove just the top portion (the part that covers the cam sprocket). If you don't do this, you have to remove both the water pump pulley and the crank pulley to get the cover off (careful you don't cut the timing belt too!).

2. I was prepared for the challenge of getting the valve cover off. There are some spacer/gasket-y things under the nuts. They need to be spun off or the cover won't budge.

3. I had to go to a friend's house to use his vice (to hold the cam sprocket so I could get the bolt out and back in, tight enough). Need to buy a vice. Can't believe I've gotten away without one for so long.

Having said that...

WOW! I like it. http://www.gassavers.org/images/smilies/tongue.gifhttp://www.gassavers.org/images/smilies/biggrin.gif

• I was worried I wouldn't be able to detect a difference, or it would so small that I wouldn't be sure if I was just imagining it.
  .
• But the car definitely has more low end cojones. (Maybe more accurate to say it has "a cojone" now, because it had none before http://www.gassavers.org/images/smilies/biggrin.gif and I'm still not going to sign up for any tractor pull competitions)
  .
• I can shift at least 5 km/h sooner than I used to, and the engine just pulls smooth smooth smooth.
  .
• I'll have to back off the timing though. I was hearing some ping, and on my test drive I couldn't open the throttle as much as I usually do during P&G. But I was told in advance to expect this - since the cam effectively raises the cylinder pressure, uncontrolled combustion is more likely when you tune it near the edge (timing advanced beyond stock).
  .
• There's a tiny amount of lifter tap that wasn't there before, but hey, what could I expect from swapping out a cam with 12,000 kms on it for one from a car that is at least 4 years older, with who knows how many more miles on it (obviously enough that it was ready for the junk yard).

Anyway - on the test run, even without being able to use as much throttle as I would have liked, I was able to pull off a 84.8 mpg (US) P&G round trip - 9.8 miles, 1 hr EBH assisted start, 3C temp.

So it certainly hasn't hurt!

In fact, I think it's safe to say it's a perfect complement to the taller tranny. Like peanut butter and jelly!

OK, smartypants... if a cam swap can improve efficiency, why don't all Metros have this kind of cam?

Because the cam profile is not good for top end performance. Lowers the redline (valves are more prone to floating than with the stock cam).

Remember the XFi also has a taller than regular final drive, so its cam profile goes better with that.

Cam update (originally written March 14/07)

Have I mentioned yet how much I like what this has done to the character of the engine? I really like it. It's so much more suited to my driving style.

I would recommend this mod to any Metro owner, particularly in combination with the longer legs. If I had the chance to buy an XFi over a regular Metro, I'd do it just for the difference in the way (I imagine) it drives.

I'm starting to realize I'd probably also really like driving a manual shift diesel for the same reasons - low end torque, short shifting, quiet, laid back, un-fussy.

For anyone following this thread, I've updated MetroMPG.com with a post summarizing the issues, installation, and (predominantly subjective) results of installing the cam in my car. Most of what you've read here is included, with some new bits added:

International heart transplant: the Blackfly gets an XFi cam - MetroMPG.com

For those wanting another Metro owner's perspective on the cam swap, Frederick has a thread about his car: Another Metro to get taller final drive & XFi cam

Pretty cool thread you resurrected here! I never realized swapping a cam could resulting in any significant improvements.

What is the Lift/Duration (@.050" - Not Advertised #) for the XFi Camshaft ? :confused:

I have been driving Espresso for a few months.
It has the XFi cam and a taller gear, actually TALLER than a regular XFi. I got it from a 4 cyl, SOHC.

When asked by members of The Order Of Canada yesterday which car did I prefer: Vanilla Latte with a stock turbo swap or Espresso Nero. I could not lie, even though my lips were stained cherry red:
The XfI cammed one. Sirs.

Yes, Espresso Nero, is a joy to ride. Particularly when passing.................... gas stations.

I just installed the XFI regrind in my latest 92 Metro convertible. Stock gear ratio, 13" tires at 32psi, 8 degree cam advance, Mobile 1 synthetic ATF in my transaxle, seat of the pants ignition advance. With the top up and windows closed I used .78 gallons of fuel in 41.6 miles for 53.3 miles per gallon. I filled the gas right to the filler neck 1/2 inch above the flapper and shook the car to get any air out and repeated the procedure at the end of the trip. Top speed was 65mph for short periods and there were a few traffic lights before getting on the highways. Average speed was 60.

My previous best on the same trip was 44mpg stock with 90w gear oil in the trans. Only a long term average will show accurate results. But I am certain that I am using far less throttle opening and it has more torque at lower rpm. I will be trying Singh grooves in the head as soon as my gaskets and head bolts arrive. I like the feel of the XFI cam and really appreciate the fuel economy boost while I keep my same driving habits.

I'm curious if all xfi cams are the same? What should I look for to replace my 1997 metro?
thanks

Its 2-1/2 years later and my daily driver still runs well with the XFI cam. Around town with no unusual driving techniques it gets a solid 44mpg. On a recent trip of 400 miles each way it averaged 54mpg just by holding the posted speed limits. On the same repeat trip 2 weeks later but in a hurry to get home it averaged 49.5 mpg with speeds exceeding 75mph at times.

XFI cams should be all the same specs. I put syntheyic ATF in the trans and keep the tires around 35psi. Woops, no Singh grooves in the head yet. I will have .040 removed from the head when I do this but the car is so reliable as a daily driver that I don't mess with it. I love what this cam did for my car.

For those of you who remember, the 70mpg diesel Metro sits in storage, unable to be registered in the Republik of Kalifornia. It may get a mid engine 3.8 supercharged Olds V-6 sitting on my engine stand if I feel cheeky enough.....but the 6.5 turbo diesel going in my boat has my full attention right now. Click here if you want to see it...
http://www.youtube.com/watch?v=iEgsxCmpSZ0

Has anyone done the cam swap but still have the 12" tires? What will that do for your mpg? Thanks, Craig

I doubt that anybody still has the 12's
I installed 13's with the same diameter overall. The MPG should be the same.

Mine is an Lsi. Just wondering how much it would change the FE if I just did the cam swap and not the tires or trans. Thanks

You will gain a little.
I did not change the tranny in mine, just the final gear. I had to mill 15thou on the face and that was it. I have been saving fuel since then. Quite important these days as fuel prices in Quebec have skyrocketed to 1.45 a liter or about $6.00 a gallon.
Of course the gvnmt. is mighty happy. Taxes are on the total price not by liter.

Does anyone know if there's an "economy cam" like this available for the 4 cylinder engine - since I'm working on mine? It's the 1.3 liter engine in a '99 Swift.
Thanks,
Bill

Good question. I wonder if the 3 cyl and 4 cyl SOHC used the same cam profile. If so, you could get an economy grind done from a 4 cyl cam.

I can tell you will probably know: Mike at 3-Tech performance: http://www.teamswift.net/3tech/

Well, it looks like this question is definitely for real, now.... The mechanic had my car up & running and was about to call me to come get it when it died. Guess some oil passages got blocked somehow, and 3 cam bearings went out. He thinks the machine shop did it during the valve job. Need to replace the cam and some other stuff now. - dammit -

so - e-mailing "3tech" now...

Good overall Cam Swap posting! Nice site. MetroMPG!

The only thing here I see that makes an incorrect assertion is where it is stated that "the smaller lift and duration" is what makes the lower RPM cylinder pressure and torque increase. Generally, it has been found that higher lift will increase torque and HP without losing any low-RPM torque, and sometimes below-peak torque is also enhanced.

I'd like to think I could get a custom regrind based on a regular 3 cylinder cam that could handily beat an XFI cam in MPG, Torque AND Horsepower, but the HP might take internal engine mods. OEM engines are so far from optimized that a dedicated builder can easily make all aspects better with a little hard work and research. A great book (now out of print) Practical Gas Flow, by Dalton.

There is ONE Outstanding cam spec that determines engine responsiveness, torque and HP more than any other, can anyone guess what that is?

Lift?

Duration?

Ramp Rate?

Lobe Style?

...or something else? ;)

I'm not too terribly informed about cam profiles, but lower lift duration should (to a point) move peak torque lower in the RPM band, where almost everyone on this site drives, right?

:turtle:

Also, I'm willing to bet there isn't a better cam that could be made for my car. It seems Honda gave their engineers leave to go all-out for the first-gen Insight.

EDIT: Welcome to the forum!

3tech will give any cam an economy or "xfi" grind. Ive asked about my insight. Plan B was to give the vtec a wild grind, but I hear the gen 2 insight may have flat lobes on the vtec profile. :thumbup:

Fixed it for ya... ;)

The reason they almost always use lower LIFT with lower DURATION is due to Ramp Rates. High Ramp Rates equate to more lift with less duration, but more stress on the valvetrain components (guides, stems, rockers, lobes...)
The beauty of this here ECO-Modding Movement is that we can use some of these higher-stress arrangements to our advantage, because we run lower RPMs nearly all of the time!

As for your Honda Engineers, I'm willing to bet they were so "handcuffed" by EPA and cost constraints they felt fortunate to get the 50+ rating they got... I used to belong to an automotive engineering bbs in the engine forums, and the consensus amongst the engineers there was that the emissions BS was the biggest enemy to economy, and hence, created more pollution. Which is normally dealt with by catalytic converters.
I also read a statement by an auto-engineer that said they dump late-cycle fuel in just before the exhaust valve opens to, (and I quote) "Keep the cats up to optimum operating temperatures". End Quote. Meaning:
They waste fuel to keep the cats warm "just in case" they cool off and you get a happy right foot!

Thanks for the Welcome, Ecky!!!
Hope to see you around!

If you could manually control the VTEC, you could open/close up the LSA and have the best of both worlds... Economy AND MPG. David Vizard did a DOHC engine once, and with stock cams had a multiple personality 4 cylinder :D