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Discussion Starter · #1 ·
Well. I've had it. My car has been getting piss poor gas mileage lately. Worst then when I had my B16 and was in VTEC a bit. The new enigne (B18) sucks the gas back and leaves black sout behind my car. I don't get it cause I never beat on it.

Right now the best I got was ~520kms for a tank. I got ~600 with the B16 and ~625 with my SOHC ZC. The B16 and B18 share the same injectors/rail/fuel pressure regulator on my setup. They also share the same tranny (YS1). How can .2L and no vtec ruin my gas mileage?

I've changed spark plugs and wires, I've also downgraded my tires for winter to smaller lighter winter rims. What else can I do to improove the mileage? The car has perfect timing at the moment aswell, but I do hear alot of backfire as if gas was burning in the exhaust. I'm gonna turn down my fuel pressure regulator.
 

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I'm pretty much a n00b to this whole thing, but from the "black soot" you mentioned, I'd say it is a mixture problem. Now, as to it being too lean or too rich, is another matter.

I guess it could also be a problem with whatever regulates the mixture as well, but I'd pull out the old service manual and go through the procedures for tuning your mixture.
 

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Well afterburn through the exhaust can be characteristic of a lean or rich condition. Either wayt here is either too little fuel, or too much fuel, in the combustion chamber to alllow for combustion to take place. Black soot (carbon) in the tail pipe is also an indicator of fuel burning in the exhuast rather than the combustion chamber.

Are you runnign a stock ecu? if so then turn your fuel pressure down to the stock pressure. Are you using an adjustable cam gear? Is your cam degreed properly?
 

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Discussion Starter · #4 ·
Well, my cams are properly aligned. I pulled my valve cover and triple checked it all. The ecu is for a D15B7 (OBD1 non vtec). It was the only OBD1 non vtec ecu I could find. And no, I am not running adjustable cam gears.
 

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And the ECU is unchipped/tuned? That's probably your problem right there man. Either get the right ECU or chip it and run a B18 basemap and see how it does for you. OBD0 B18 ECUs are easy to find, why not go back to OBD0 and use that?
 

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Discussion Starter · #6 ·
downest said:
And the ECU is unchipped/tuned? That's probably your problem right there man. Either get the right ECU or chip it and run a B18 basemap and see how it does for you. OBD0 B18 ECUs are easy to find, why not go back to OBD0 and use that?
Because this motor is temporary. Infact, I doubt it will be in my car in 6 months, I'm just trying to get as much out of it without spending large amounts of money. And I would think the D15 ecu would be better on gas then the B18 ecu. Basemap for basemap I beleive the P06 is better on fuel.

Only a few more months before my GSR can go in.
 

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Get it running correctly (not too lean, not too rich). Then, shift at 3000 whenever you're driving (keep it off of VTEC). Coast to red lights with the clutch in. You'll get great gas mileage.
 

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Discussion Starter · #8 ·
tubafreak said:
Get it running correctly (not too lean, not too rich). Then, shift at 3000 whenever you're driving (keep it off of VTEC). Coast to red lights with the clutch in. You'll get great gas mileage.
I do that right now only I go up to 3250-3500rpm. I'm trying to make the engine burn cleaner so it needs less fuel. Is there any tricks to help it even more that someone mighth have hiding up there sleeve?
 

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a statement like 'basemap for basemap its better for fuel' makes no sense.

you need to be running the appropriate map for your engine, then your mileage will be normal, all other things correct.

I get over 40mpg on highway trips with my GSR motor, and a minimum of 25mpg beating on it around town.

What ECU you have in there, a p06? It would be farily trivial to socket it and run a correct B18 basemap.

I succeeded in making my car fuel efficient by leaning out the idle as much as possible, and running at about 15-16:1 part throttle. I run right off the maps I made, the ECU uses no oxygen sensor input.

[email protected]
 

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ludesrv said:
The new enigne (B18) sucks the gas back and leaves black sout behind my car.
As stated already, sounds like it is not getting the correct amount of fuel, either to rich or too lean.

Find the correct ECU and see if that fixes the problem since the Ecu yoiu have in there now was never meant to run a b18.
 

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Discussion Starter · #12 ·
Well I am getting my P28 chipped by CRXTOAD soon, maybe I can get my brother to burn the basemap. But still, the engine just doesnt seem like it likes to run right. I want to remove my adjustable fuel pressure regulator (was tuned to the B16) and put the factory one on, but that requires me to get fuel on my hands, and my skin doesn't like gas.
 

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If its leaving black soot then that means its too rich.....whitish blue smoke is too lean if I'm not mistaken. I dont know how to go about adjusting that but as everyone else has stated I would assume the ECU......but then again we do all know what they say about assuming stuff so..........
 

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This might sound dumb but I will ask anyways because it goes along with this. Isn't common to have some carbon in the tail pipe if you don't have a stock exhaust and intake? Sometimes when I wash my car there will be carbon that comes out with the water that sat in the tail pipe till the first start after washing it. Maybe I am running rich too?
 

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I'm not exactly a knowit-all when it comes to cars yet but I'm pretty sure some is normal. But one thing I know for sure is that it's better to be too rich than too lean. If you're car is running just a hair rich it's ok........but if it's running too lean it will mess up your motor. I wouldn't worry about it unless it's making a lot of black smoke when you get on the gas.
 

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george34 said:
This might sound dumb but I will ask anyways because it goes along with this. Isn't common to have some carbon in the tail pipe if you don't have a stock exhaust and intake? Sometimes when I wash my car there will be carbon that comes out with the water that sat in the tail pipe till the first start after washing it. Maybe I am running rich too?
stock ecu's are set up to run a tad rich thats why youwill see a little black soot in your exhaust.

but as for ludesrv not only are your fuel maps different so is your ignition timing becuase your running the wrong ecu. you need to find yourself a stock ls ecu. or chip your current one.
 

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Alright, look, since I can't find anything about the chemistry/physics/thermodynamics of lean-ness and rich-ness, I'll just post what I remember from pilot's lessons about the effects of lean and rich on aircraft engines, so take it with a grain of salt, and maybe someone can find material (or I will later) to back me up.

Lean: The oxygen to fuel ratio favors oxygen. The foremost of this effect is that there is more of a high temperature, clean burn, and less fuel to be exhausted. This should result in less fuel going into the engine, and a more complete energy use of what is in there. Possibly more power, but that's going out on a limb. The downside is the increased heat and other wear-and-tear factors. This is supported by cold air intakes giving more power, as the air is more dense than usual, resulting in a more oxygen-rich (lean) mixture. Also why its a bit more enjoyable to drive on nice cold days. The engines love it.

Also why I liked to fly the "slow" Cessna 152 on days that were cold, took forever to get to altitude in that one. But that is another story...

Rich: The oxygen to fuel ratio favors fuel. As far as I know this means that less of the fuel overall is burned for lack of oxygen, therefore the engine is "wet" and overall temperature is reduced. This has the side-effect of reducing power and exhausting more unburned fuel. This references a warm air intake, mentioned above, causing thiner air to be mixed with the fuel, thus resulting in a more rich mixture.

Disclaimer: the air intakes thing is pure conjecture.

So, to re-cap, lean makes for a more complete, hot burn and rich makes for a less complete but cooler burn.

In all cases, not 100% of fuel is combusted, just one more thing that drags on the efficiency of our engines.

Also, go too lean, and you starve the engine of fuel. You could also cause overheating, and other crazy problems I'm sure. Too rich and you risk detonation, backfiring, and depriving the engine of oxygen altogether.

In keeping with this, and the old trick to clean off the plugs in a airplane engine (forcing the engine temperature up to burn off carbon), when my car is working again, I plan on leaning out the mixture just a tad, and driving it around for a while, then putting it back to normal. That is assuming I can find the procedure in my manuals again.

If I've made a mistake, please, someone point it out to me. Otherwise, take this with a grain of salt. A balanced ratio is probably better than going too lean or too rich on accident. Please don't blow your engines on my pseudo-scientific theory.

Again, at this time, I cannot find anything to support what I just said, but I'll work on it. Everything is based on what I learned from airplanes.
 

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AngryUndead said:
This is supported by cold air intakes giving more power, as the air is more dense than usual, resulting in a more oxygen-rich (lean) mixture.
My CRX likes a cold day as much as the next (which is lots) but I think the reason for this is that the ECU computes air density from the temperature and pressure in the manifold, and changes the fuel to match that. Cold start enrichment aside, it shouldn't be running a lot leaner when it's cold out. For example:

http://en.wikipedia.org/wiki/Density_of_air

From the table, the air density is 15% greater going from 30C (86F) to -10C (14F) .. so the ECU says "hmm, 15% more fuel, add a tad more for WOT" and I say 8)
 
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