Fuel economy question

[TheProfiteer]

I have a civic with a B18B1 Swap.
I also have a alternator thats not putting off enough voltage at lower RPM
I know this because I can see my running lights and interior lights get brighter after I pass 3500rpm.

I the problem is that I am only getting around 23mpg average, and the LS motor should be getting around 26-28mpg.

Could my alternator be causing this?

If its not the Alternator what else could it be.

I also notice that my low end power is some what laggy as well, not enough to be a timing issue, but still kind of laggy.

Any one have any advice?

[Scotsman]

pm evasive , he is a well known LS guy

[AnthonyF]

hmmm....

[AnthonyF]

all seriousness tho, check to see if you have a short. Or while the car is running try tapping on the alternator and check your batter with a volt meter. Dont just go by what the lights are doing. Get some good readings.

[TheProfiteer]

Will do.

How do I go about finding a short?

and will a bad alternator cause a drop in power and MPG?

[TheProfiteer]

ok I got the Alternator test, and it while it supposed to be putting out around 13.4v at 2000rpm its only putting out around 10v

so once more, will this cause a direct loss of power and fuel efficiency?

[KurtzBoom]

Just Look in for your Car Manual Guide that would help.

[JDMirza]

ok I got the Alternator test, and it while it supposed to be putting out around 13.4v at 2000rpm its only putting out around 10v

so once more, will this cause a direct loss of power and fuel efficiency?
Checking for shorts: Once something is shorted out let's say your interior lights for example ......... go to the fuse box and pull out the interior fuse. Look at the fuse and if its split, cut, cracked, sacked, ****ed! .. then that means its shorted out. Usually once some thing is shorted out the fuse will blow, unless you dont have a fuse attached towards the power wire.

As for your alternator: It's suppose to be putting out about 13.6-14.3 volts at the assigned rpms you are talking about, did you try replacing your alternator ?

[TheProfiteer]

Yeah I need to replace it, thats what I am going to do.

[Tech5]

ok....the power to alternator is a constant battery voltage power, if you pull the green plug out, you short take a test light, an check the power, you should have one power 12.00 volts, an one is a 5.0volt reference, an a ground, then a signal wire where your ELD sends a signal out of the computer to the alternator to tell it to charge, hope this helps, most causes like yours its the alternator, an gas milage?, check your timing, since you put a used engine in with miles on it, its due for one, an if you put a timing belt on, then you might have it off a tooth, check your plugs, the gap,tune up, O2 sensor,fuel filter, Bad fuel preasure regulator, etc. hope that help you to go in a direction,

[RBS]

well if you tested the alternator and it puts out 10v then that means its bad lol, replace it and be happy

[Tech5]

No not all the times,,,,, your computer has a EDL in it to send a signal from the ECU to the alternator to tell it to charge...if it only shows 10 v your battery is dead,,,, check it like i stated, if you need a diagram ill send you one
well if you tested the alternator and it puts out 10v then that means its bad lol, replace it and be happy

[Tech5]

here is alink ...http://www.partsamerica.com/product_images/aap/WRW/626.pdf