MPGs run, Aspire SE

[TominMO]

Just made another run. Got good results yet? Nope, not this time. 143 miles, 44.7 MPG. Checked for codes; none. Re-checked cam timing. STILL looks retarded one tooth! Gonna tear into it tmw, after the engine (and I) cool down. After I pull the H2O pump sprocket, I will mark the block timing mark and the crankshaft gear notch to make them more visible. Shoulda done it when I changed the front crankshaft seal. So basically the last 550 miles of testing were a giant waste of time. Sigh.....

Edit: the last two tests were driving around St Louis, which is a bit more hilly than my previous tests in IL. Now that I have more confidence in the motor (i.e. fixed the O2 sensor issue), I will go back to testing in IL.

[TorqueEffect]

I believe since I changed all my filters (Fuel, air, tank) my MPGs have actually taken a nose dive.
My Gas gauge has never steered me wrong before, but it is saying I am well under 200 miles for a little more than a half a tank of gas.

Ever since I changed the pump strainer, it has been using fuel like crazy. I swear it is like I have a fuel leak when it is running, but I don't smell any gas at all.

[TominMO]

Please refer to my new thread in The Arena....

[sketchman]

^Wait, what? Anything everybody needs to hear?

EDIT: Never mind. Figured it out.

[TominMO]

Talked to Matt today about my MPG issues with this cam. I understood before that this is all new territory, his expertise notwithstanding. I will continue to experiment with this cam. He is finishing up my adjustable FPR and header, so they should come soon.

BTW I was wrong in thinking that my cam was still a tooth off. I did correct it properly before, and it is spot on. Rotated the crank a full 360 to make sure.

The best mileage I have gotten with this cam is 52.4, when the cam was a tooth retarded and ignition timing was 13 degrees. So now I am going to try it with proper cam timing and 13 degrees. My last two runs were at 10 degrees. If I don't get good results, I might go back to retarding the cam a tooth, since that has been my best result yet. Might also advance the ignition slightly more, although I think 13 is all I can get.

[jason_]

There's a reason race boys use a degree plate, they neve ever rely on factory marks made by the thousands...

Sent from my rooted HTC Supersonic using Tapatalk 2 Pro

[sketchman]

Kinda hard to find "absolute" TDC to even make the use of a degree wheel 100% accurate, though without having the head off, yes? Unless, do they assume the crank marks are 100% dead on?

[jason_]

Kinda hard to find "absolute" TDC to even make the use of a degree wheel 100% accurate, though without having the head off, yes? Unless, do they assume the crank marks are 100% dead on?

That's my point. Going blind unless knowing it's 100% from step 1, which requires a degree plate from the beginning.

Otherwise we're assuming factory is good enough. We might be 1 deg off everywhere, especially dizzy.

We're assuming crank pulley is broached and keyed accurate, pulley is marked accurate, gears casted accurate, and belt is rolling teeth in synch accurately, so dizzy shoots spark accurately.

Kinda shooting for the moon with a bow and arrow, unless like I said, wheel from step 1....

I'm just pointing out, there's a lot of work to do to make sure things are turning circles in our favor if you reallllly want to get accurate.

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[TominMO]

That's why I'm thinking of getting an adjustable cam gear. Then I can move it around and find the optimum MPG spot, and not worry about what the numbers say. Same with ignition timing, but it does seem to run better with it advanced a bit. Gonna do a run later today with 14 degrees advance and cam timed properly, i.e. meaning both marks straight up on crank and cam gears.

[TominMO]

Went on another test today. Because I know my gas gauge very well*, I knew I was getting very low mileage, similar to the last two tests. Didn't bother to fill up to verify; I'll just call it 45 MPG. Besides that, the CEL kept coming on every 8 or 10 miles. Checked it; yup, a code 17 again, and the system got kicked into limp-home mode.

Previously I had interpreted a 17 as a failed O2 sensor; but that is actually a 15. A code 17 points to a fuel or ignition issue, which is detected by the O2 sensor. So I had replaced a good O2 sensor unnecessarily; it did not fail after 21 months.

So here is a summary of my runs with this cam:

MPG......Ignition......Cam setup......Comments
52.4......13 BTDC.....7* retarded.....no issues
46.1......10 BTDC.....zeroed............code 17
44.7......10 BTDC.....zeroed............new O2 sensor; no codes
~45......13 BTDC.....zeroed............code 17

Apparently the EFI computer cannot deal with this cam, at least when it is set to zero degrees. At 7 degrees retarded and with ignition advanced to 13 degrees, it didn't throw any codes.

Matt said he had programmed in some lobe retardation, along with less lift and duration. I wonder if I should just go with his lift/duration and actually advance the cam a tooth? But before I do any more tests, I think I will install an adjustable cam gear. Makes tuning the cam a lot easier and more precise. A one-tooth cam gear change is 7.8 degrees, so wih an adjustable gear I can change it in much smaller increments.



* When my gauge's needle gets down to the "F" line, I have used between 1.30 - 1.35 gallons, based on computations from all my previous tests. And the 3/4 mark is actually 2.5 gallons used.

[TominMO]

Come to think of it, I might have problems with going down in fuel pressure too, if the system senses a too-lean condition and puts me into limp-home. So I think it will be a juggling act to get this down right. I need the adjustable cam gear, and the gauge on the adjustable FPR, and the ignition timing scale to try to pull this all together. Turning out to be a lot bigger job than just tossing a few parts at it.

It might turn out that I can either turn down fuel pressure or use Matt's cam, but not both; because it may be too hard to juggle the two parts and still keep out of what the computer perceives as too lean, and then kicks me into limp-home. And of course I will be adding his header! Which may put me back to square one. So perhaps I should put all this on hold until I have the header installed. Then the cam gear and FPR, and I can go for it.

At this point, do I need a wideband O2 sensor to monitor my adjustments, rather than go on long runs, since it's getting complicated? Whatcha think?

EDIT: I just answered my own question. At least with Matt's header I will get another O2 sensor bung so I can run both the stock Denso for the EFI computer, and the wideband to monitor stuff.

[sketchman]

I just hope the old system will not freak out like that.

[bhazard]

If you have a wideband then you can run narrowband simulation to the ecu and adjust the closed loop AFR.

[TominMO]

If you have a wideband then you can run narrowband simulation to the ecu and adjust the closed loop AFR.

Do you mean I could use the wideband in place of the narrowband stock O2 sensor? Hook it to the narrowband wire and somehow fool it into giving me the AFR I want? Pls explain in more detail, since I have never used a wideband before.

[sketchman]

It can simulate the narrow band being there to the ECU so it doesn't flip out, but you can still see what's really happening and adjust accordingly without the computer trying to save you from yourself.