horrible mpg's when can i lean out?

[rocklizzard91]

hello all. im wondering why im getting only 20mpg on my VW 2.0 16v
i should be getting at LEAST 25ish. and im getting 20 every time.

i turned off ego correction and tuned so that below 50kpa im running pretty lean (15-17 on my wideband)
however, i cant get the car to maintain constant highway speed at or under 50kpa
its usually at 55-60kpa where i can keep it constant.
is it ok to be that high and be leaning it out? right now it only sees maybe 15afr max at 55-60kpa


im also wondering how rich i need to go when i get into higher rpm and under load. it'll dip as low as 11 sometimes. its an NA motor. i just tuned it to be pretty rich up there to not melt stuff. but now im tired or commuting 50+miles a day and getting 20MPG

thanks for any help

[Matt Cramer]

You probably need to get your spark table tuned if the MS is controlling timing. This can have a huge effect on mileage.

[rocklizzard91]

You probably need to get your spark table tuned if the MS is controlling timing. This can have a huge effect on mileage.

how do i tune the soark table ive only done the fuel map

[rocklizzard91]

You probably need to get your spark table tuned if the MS is controlling timing. This can have a huge effect on mileage.

how do i tune the soark table ive only done the fuel map

the guy who base tuned me did my map. i can post a pic of it if you would like to see to help me out. 20mpg is killing me!

[Matt Cramer]

Feel free to post it - I don't have a well tuned VW spark table to compare it to, but I may be able to spot a table that clearly needs tuning. We generally get better results dyno tuning spark maps.

[rocklizzard91]

Feel free to post it - I don't have a well tuned VW spark table to compare it to, but I may be able to spot a table that clearly needs tuning. We generally get better results dyno tuning spark maps.

hmmm ok i'll have to look for a dyno tuner locally
will a honda dyno tuner know how to tune a mesagquirt system?
i think there is one who specializes in hondas somewhere over here

heres one i downloaded and am testing out now. just started today

here is my old one i had before

[rocklizzard91]

???

[Matt Cramer]

The first one looks more like a real spark table than the second, but I can't tell if it is your engine's spark table or not.

[rocklizzard91]

The first one looks more like a real spark table than the second, but I can't tell if it is your engine's spark table or not.

HMmm ok. How would I go about tuning this then?
Also how does the spark map affect gas mileage?

[Matt Cramer]

The best way to tune the map is on a steady state dyno. Set it to conservative values, hold it in each load cell, and increase the timing till you don't make any more power.

You want to time the spark so that you get peak cylinder pressure around 10-12 degrees after top dead center. If it's advanced too much, the burning gases will push back too hard on the piston as it comes up. Too retarded and the pressure doesn't start building until the piston is too far down the cylinder. Either way results in less than optimal efficiency.

[rocklizzard91]

The best way to tune the map is on a steady state dyno. Set it to conservative values, hold it in each load cell, and increase the timing till you don't make any more power.

You want to time the spark so that you get peak cylinder pressure around 10-12 degrees after top dead center. If it's advanced too much, the burning gases will push back too hard on the piston as it comes up. Too retarded and the pressure doesn't start building until the piston is too far down the cylinder. Either way results in less than optimal efficiency.

oh right on. thanks!
i need to find a steady dyno then

[drmiller100]

I am NOT a megasquirt expert. I have not even run a system, I am just researching and reading and learning.

I am REALLY surprised at how high of an RPM before the advance kicks in. I would have expected advance to climbing at 2500 to 30 degrees or so for high vacuum.

Am I out to lunch, or just used to really old engines?

thank you for opinions.

[cygnus x-1]

I am REALLY surprised at how high of an RPM before the advance kicks in. I would have expected advance to climbing at 2500 to 30 degrees or so for high vacuum.
Am I out to lunch, or just used to really old engines?
thank you for opinions.

Every engine is different but it does look like the timing comes in pretty late. The 2500RPM column in the new table should look like the 2600RPM column in the old table, especially at MAP levels below 60kPa. My old 2.0L Honda likes lots of timing advance at lower RPM due to the combustion chamber design.


C|

[rocklizzard91]

I am REALLY surprised at how high of an RPM before the advance kicks in. I would have expected advance to climbing at 2500 to 30 degrees or so for high vacuum.
Am I out to lunch, or just used to really old engines?
thank you for opinions.

Every engine is different but it does look like the timing comes in pretty late. The 2500RPM column in the new table should look like the 2600RPM column in the old table, especially at MAP levels below 60kPa. My old 2.0L Honda likes lots of timing advance at lower RPM due to the combustion chamber design.


C|

hmmm im sure i probably could. i only have basic tuning done to it

[drmiller100]

funny, i always justified lots of ignition timing for cruising around for really crappy, poor combustion chambers!!!

on a chevy 350 or even vw bugs, one way to tune them is to remove vacuum advance line, rev them to 3000 rpm, set total advance at 30 or 35 or so. Then check they back off to around 0 or 10 BTDC at idle, then go drive it.

brute force I know, but it was a place to start.

[drmiller100]

also, go learn about pinging or knock. If you get too much advance, the engine will ping or knock. This is really bad for the engine, but fairly easy to hear and recognize on most engines.

a few seconds won't hurt an engine, but a few minutes will destroy one. so, advance the timing until it knocks, then back it off 2 to 4 degrees. Quality of gas has a HUGE impact on knock, so make sure you tune it with the gas you will be running.

[rocklizzard91]

also, go learn about pinging or knock. If you get too much advance, the engine will ping or knock. This is really bad for the engine, but fairly easy to hear and recognize on most engines.

a few seconds won't hurt an engine, but a few minutes will destroy one. so, advance the timing until it knocks, then back it off 2 to 4 degrees. Quality of gas has a HUGE impact on knock, so make sure you tune it with the gas you will be running.

i dont have vac advance so i cant do that
but i will see about learing about knock and ping
i dont want to get too expiremental with it because i dont know how to identify it

[Matt Cramer]

It can sound like anything from rocks in a coffee can to a metallic pinging sound. Note that while pinging does mean you're too advanced, sometimes engines can make best power well below the knock level, sometimes 10 degrees or more before it. It depends on the engine.

[drmiller100]

vacuum advance on old distributors are replaced by the MAP kPa on the graph you posted above.

so, to me, 95 kPa on the map above is the same as vacuum advance unhooked - you need less advance at WOT, and can use more advance at high vacuum, part throttle.

[rocklizzard91]

vacuum advance on old distributors are replaced by the MAP kPa on the graph you posted above.

so, to me, 95 kPa on the map above is the same as vacuum advance unhooked - you need less advance at WOT, and can use more advance at high vacuum, part throttle.

why do you need less advance at wot?
thought you wanted advance