MPGs run, Aspire SE

[TominMO]

How's the car running overall? Are you just fine tuning it or does it have an issue?

I'm having trouble getting it to run right. Maybe it is a vacuum issue; I will look into that tmw.

[zoom zoom]

How's the car running overall? Are you just fine tuning it or does it have an issue?

[TominMO]

The factory service manual says the intake manifold vacuum should read greater than 17.7 inches.
And to subtract 1 inch from the specified reading for every 1000 feet of elevation above sea level.

Thanks. Looking forward to results tmw.

[TominMO]

that's your Vac gauge port!!! USE IT (muahahahaha)

As you command......:notworthy:

[rmoltis]

The factory service manual says the intake manifold vacuum should read greater than 17.7 inches.
And to subtract 1 inch from the specified reading for every 1000 feet of elevation above sea level.

[FestYboy]

that's your Vac gauge port!!! USE IT (muahahahaha)

[TominMO]

^ yes, but not terribly accurate.

Off to HF in the morning then....you say to tap into a port that the EVAP system uses. I have an unused vacuum connection with a rubber plug on it at the rear driver side of the upper intake mani, next to where the vacuum hose is for the FPR. Will that unused connection do?

[TominMO]

HF has a fantastic unit for $20 ( i have 2) of that very same model. just tap into a vac port that the EVAP system uses on the intake, and you're good. you should see 20" or better (higher is better). Scrappy pulls 23" with a factory cam, 10* timing, full exhaust, full port/polish job and 700 rpm idle speed (B6). I'll have to check what Skippy does with the FMS cam, FPR at 42psi and head work on an otherwise factory B3.

I'm also wondering if the design of the cam itself is leaving me with less vacuum, due to having more valve overlap. Is that a possibility too?

Tom your boost gauge from your festiva will serve as a vacuum gauge

Oh right. Just pulled it out to see the range. Goes up to 30" Hg.

[FestYboy]

^ yes, but not terribly accurate.

[eurotiva]

Tom your boost gauge from your festiva will serve as a vacuum gauge

[FestYboy]

HF has a fantastic unit for $20 ( i have 2) of that very same model. just tap into a vac port that the EVAP system uses on the intake, and you're good. you should see 20" or better (higher is better). Scrappy pulls 23" with a factory cam, 10* timing, full exhaust, full port/polish job and 700 rpm idle speed (B6). I'll have to check what Skippy does with the FMS cam, FPR at 42psi and head work on an otherwise factory B3.

[TominMO]

Compression recently checked and is excellent, 179 - 190. How do I check for vacuum? Does HF have a cheap vacuum gauge kit I can buy, for example? Or go to a McParts store?

Edit: here is one from HF. Good enough? What pressure or pressure range should I expect to see at idle?

http://www.harborfreight.com/fuel-pump-and-vacuum-tester-93547.html

[FestYboy]

still think you need to ADD FP (higher then stock)... just as a for instance: Skippy has head work and FMS comp cam and yielded 44+ mpg on my trip to Mass. this was at 70mph. I run 42 psi.

have you run a compression test since the cam install? and what does your idle vacuum look like?

all of those adjustments should have netted a wider range of results than what you've been posting. something is asque.

[TominMO]

Went on another drive today. Cam at +2, ignition at 13. This time I also lowered fuel pressure, for the first time. I went down to 28. After driving for 50 miles or so, I pulled into a rest stop and upped it to 33, because it was running a bit lean and was hesitating noticeably. Also it tended to die when off the gas. Drove back home, and on the way stopped to adjust pressure up a bit more, to ~37, because I was still getting the previous symptoms, but not quite so bad. So basically it likes stock FP. Looking at the gas gauge, it seems about the same as on previous tests. This config was not an improvement. At this point I'm starting to think about just going back to the stock cam, and calling it a day. But I'll do one last test at +2 and 15, with stock FP, because even with FP at 37 it tended to die; so I think it needs a little more ignition timing.

[TominMO]

Hate to see this happen but i was afraid that the ecu fights mechanical parameters built into the cams specs. The gains advertised were on a non california carbed model. I think aspire ecu sees more of the picture if you will trying to feed fuel and timing based on incoming air then trimming as needed via o2. Safc tweaks those, efie and voltage out the o2 tweaks the back end but its still not optimum. Your aspire is getting a lot higher mileage than i am getting and i never go over 65. Buy a 88 festiva, swap in b6. Simple haha

Two other issues with trying to get better mileage are (1) engine RPM @ 60 MPH (gearing), and (2) the displacement of the motor, coupled with a programmed "need" for a certain AFR of 14.7 or numerically lower. In other words, if it was a 1.0 liter motor like the Metro 3-cylinder, it would require less fuel to do the same basic job. But in all cases, whatever the gearing or displacement, there is a limit to what can be done, and this design may be close to that limit. And bear in mind that part of the ~52 MPG it's getting is due to the chin spoiler; that seems to be worth 6 MPG by itself.

Edit: Oh duh, just realized I don't need to pull the cam gear, just move it over so it isn't off two teeth. Then adjust to +2.