turbo vtec-e on 4 dr civic gas mileage - Fuelly Forums

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Old 10-08-2008, 07:39 AM   #1
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turbo vtec-e on 4 dr civic gas mileage

http://www.turbod16.com/viewtopic.ph...0+afr+not+very


currently ive been getting 30-32mpg combined.

my commute consist of driving to school 10km highway @80-100km/h then 16km city(more like alley streets here in the philippines) and it roughly takes me 45-60 min to get there, depending on traffic.

i think my tires and the transmission thats causing the bad mileage...are they?

2650rpm@62mhp on 195/50/16 dunlop fm901....
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Old 10-08-2008, 11:40 AM   #2
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There's some good advice in the thread you provided.
You have a good motor, good trans, but driving on goat roads while maneuvering around slower traffic obstacles will hurt FE. Like they said in that thread, afr's need to be richer at mid to open throttle. I recomend keeping the afr's very lean at the lightest loads.
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Old 10-08-2008, 09:17 PM   #3
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ahh yes i posted that 6 months ago and listend to that they were saying so i increased the fuel a bit

i took the afr to 16.5 light loads to a gradual 14 wot. the mileage went bad from 28mpg to 25mpg

now my afr are 18:1 light load...17:1 wot...20:1 cruising and been constantly logging 30-32mpg
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Old 10-11-2008, 11:27 PM   #4
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Here's a post I wrote on another forum. I think it applies to your car as well.

How lean you can go depends on how much airflow (grams per rev) is going through the motor. At light load you can go very lean without fear. As airflow goes up the A/F ratio should gradually get richer until around 5 in/hg vacuum where it should be around stoich.

From my experience the limit to how lean you can go will be misifires. If the motor misfires, it's too lean. Bigger plug gaps helps to reduce lean misfires, but you'll have to balance that against WOT misfires if the gap is too big. I've been able to run slightly leaner than 18:1 at very light throttle.

I also found that my motor doesn't have a smooth idle and it stalls easily if the A/F ratio goes leaner than around 16.0:1. So I've set my rolling idle A/F ratio at 16.0, then it goes to 18.0 just off idle, and gradually richens.

A side effect of running leaner than stoich is that the mixture burns slower, so knock is less likely, but the engine needs more timing to keep power levels from dropping, so I've also added one or two degrees of timing in the same parts of the map that are very lean. It's working very well!

There's some good info in this link. http://www.max-boost.co.uk/max-boost...ion_deeper.htm Scroll down to the bottom, there's a little chart that shows mixture burn speed at different A/F ratios. It'll give you an idea of timing changes needed for leaner A/F ratios. The whole site has plenty of good reading.

HTH
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Old 10-12-2008, 10:04 AM   #5
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Quote:
Originally Posted by koji_kabuto View Post
now my afr are 18:1 light load...17:1 wot...20:1 cruising and been constantly logging 30-32mpg
Yikes. That motor isn't going to last long.

At this point I'd do a compression test. Also look for burned or unseated valves. You may need to start looking for a replacement engine. Also check your cat converter. If you take it off and dust falls out of it then you cooked it.

Those air/fuel ratios are suicidal. It's not going to give you better mileage. You NEED power under load. If you run lean, you end up giving it more throttle so it doesn't do you any good. Not to mention the damage that it does to your engine. Besides abnormal combustion your engine needs fuel to cool down the valves.

Run it lean at cruising load but run it safely rich under heavy load and stoich at idle. Look at it this way. When you have the pedal all the way down, is saving gas your priority? No. Getting the car moving is. If you want to save gas, you'll never go into the heavy load portion of the calibration.

Idle needs to be stoich in order to be stable. If you run it lean it will hunt and occasionally stall (like when the radiator fan kicks on). It will force you to idle at a higher RPM, so it defeats the purpose.
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Old 10-12-2008, 10:15 AM   #6
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Quote:
Originally Posted by DRW View Post
How lean you can go depends on how much airflow (grams per rev) is going through the motor.
I don't think that's right. Air fuel ratio is different than fuel consumption. 18:1 at 3000 RPM is less fuel than 18:1 at 4000 RPM. If more air is flowing (ie lower elevation), you can have the same mixture of air to fuel, but you'll be using more fuel.

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At light load you can go very lean without fear. As airflow goes up the A/F ratio should gradually get richer until around 5 in/hg vacuum where it should be around stoich.
And you don't stop there. As load increases even further, you need to go richer and less timing advance or you risk engine damage.

Quote:
I also found that my motor doesn't have a smooth idle and it stalls easily if the A/F ratio goes leaner than around 16.0:1. So I've set my rolling idle A/F ratio at 16.0, then it goes to 18.0 just off idle, and gradually richens.
Mine hunts and stalls easily at anything richer than stoich. In fact, I have enough trouble with the idle even at stoich. The VTEC-E engines are designed to idle at an average of 14.5. There's no mpg gain from a lean idle. If there is, then the problem is that you are idling way too much.

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A side effect of running leaner than stoich is that the mixture burns slower, so knock is less likely
Abnormal combustion is MORE likely.

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but the engine needs more timing to keep power levels from dropping
It needs earlier timing to burn the mixture. If you wait to long to light it off, the high combustion temps are going to light it off spontaneously; and not evenly.

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so I've also added one or two degrees of timing in the same parts of the map that are very lean. It's working very well!
Try even more timing. 2 degrees for a very lean mixture is pretty conservative.

Quote:
There's some good info in this link. http://www.max-boost.co.uk/max-boost...ion_deeper.htm
Is that based on Max Boost by Corky Bell?
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Old 10-13-2008, 04:12 AM   #7
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Are you using an auxillary fuel? I think at those AFR something else would be beneficial.
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Old 10-14-2008, 06:42 AM   #8
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actually my egt's are lower from 850f to 700f at cruising

accelerating and dodging traffic doest even reach 600f granted the egt sensor is located 6 inches after the turbine...

timing wise... i cant really be sure of the exact # because im using obd1 ecu... but they are really low

hey suspended hatch.. saw your sig and im wondering about your set up man since i have an aem ems and im having trouble running it, way toooo different to what im used to
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