CRXFi Build Thread (Geo Metro XFi drivetrain in Honda CRX) - Page 30 - Fuel Economy, Hypermiling, EcoModding News and Forum

Christ · 05-12-2011, 04:08 AM

I forgot to mention that I was going to be in jc yesterday... Else I'm sure I'd have heard about this first hand. I probably wouldn't have been good company though, as tied and in pain as I was/am. Stupid teeth...

Wonderboy · 05-12-2011, 08:38 AM

Looks like the guy who does those 3tech cam sprockets is in ontario... Darin, if you go get one for me, maybe I'll make my first trip up there to visit!

MetroMPG · 05-12-2011, 09:40 AM

I think he's about a billion km away from here. (Ontario is big.) You're closer to me than he is!

But if I can help by having him ship stuff to me or whatever, happy to help.

Glad you didn't die! (Note to self: fix ForkenSwift underbody before it too "self-steers" somewhere...)

Wonderboy · 05-12-2011, 01:00 PM

O. Oh well! Forget that, I'll just have it shipped. Do you have a special cam sprocket on the flea? It's amazing what a dramatic difference happens within 18 degrees. What do you have your timing set to?

MetroMPG · 05-12-2011, 01:54 PM

I just have the XFi cam on the OEM sprocket. The XFi cam has a certain amount of timing difference built in, if I'm not mistaken.

Ignition timing is set by ear. I have no idea what it's at numerically. If it pings at Pulse Power levels, it's too far advanced.

I'm such a help, I know.

Christ · 05-12-2011, 01:58 PM

"pulse power", on my mark... 2... 1... MARK!

Engage hyper drive, stage 2...

It was there, and I'm bored.

robertwb70 · 05-12-2011, 02:32 PM

XFI cam has 6 degrees of advance built in already.

Wonderboy · 05-12-2011, 04:03 PM

ooOOooo, that's a helpful piece of information robert! Thank you. Is that advance in the sprocket or the shaft itself? If it's in the sprocket, I might be able to get away with using a stock sprocket. Talking through this will probably clear it up for me too:

With the crank and cam both pointing TDC, retarding the timing gets me just short of the timing I feel I need. The bottom end is strong, but the end of the top end is still a little weak for the highway.

With the cam retarded by one tooth, the top end is nice and smooth, and reasonably powerful (could be better), but the low end is very weak (for a g10) and revving a little before moving from a complete stop is necessary.

It's still very drivable under both conditions, but in both cases, I have to retard the distributor all the way to get the most desirable setting. This doesn't make sense to me though. When I had the cam sprocket at the stock setting, the most advanced setting of the dizzy resulted in a fast idle, rough vibrating engine on acceleration, and no top end. Now that the cam is advanced 1 tooth (18deg), the lowest setting on the dizzy results in in inability to idle (no bottom end). If I advanced the sprocket, shouldn't the...ohhhh. I knew writing this out would help. If the timing was just getting good by retarding from TDC, I should've retarded the cam sprocket! Ha! I'm pretty sure I retarded the belt. Why though is the top end so much smoother now with this way advanced setting? Even that little hesitation at 2k rpm is almost gone...what a wonder. This seems crazy though... How could advancing my cam by 36 degrees make the difference is if works "just okay" now?

robertwb70 · 05-12-2011, 09:23 PM

On the factory XFI cam the advance is in the camshaft itself, the sprockets are the same (actually there are 2 different styles, stamped(1989-1994) and cast(95+), but the alignment is the same, different tooth shape). The other "economy" cams (from 3 tech and delta cams) offered don't have the advance built in since they are re-ground on stock cam cores, this allows a little more flexibility when combined with the advancing sprockets.

After you put the belt on did you turn the engine and re-check the alignment? I usually end up 1 tooth off just about every time, and I've done it about a dozen times so far...it's just hard to account for the belt not having any tension on it when you're lining up the marks. From what you've said I think you're probably lined up right now and were off before, so you're not really 36* advanced, I'm not sure it would run at all at that point but then again it also seems like it would be much more obvious which setting was correct too. When you start talking advanced/ retarded and sprocket/ belt things can get confusing pretty fast.

Generally if everything is set right the dizzy is about in the middle of it's adjustment slot for the stock ignition timing (something like 5* BTDC IIRC).

metroschultz · 05-13-2011, 09:01 AM

Quote:

Originally Posted by robertwb70

After you put the belt on did you turn the engine and re-check the alignment?[/I] I usually end up 1 tooth off just about every time, and I've done it about a dozen times so far...it's just hard to account for the belt not having any tension on it when you're lining up the marks....Generally if everything is set right the dizzy is about in the middle of it's adjustment slot for the stock ignition timing (something like 5* BTDC IIRC).

In order to account for the belt slack during install;
I rotate the crankshaft backward about 10 degrees,
Then install the belt and rotate the crank forward to position,
This tensions the belt and puts it in alignment.
This works for me every time. YMMV