gearbox

iTrader: (95)

You know I've noticed on alot of cars (even civics) there is carbon buildup inside the exhaust pipe, like the tailpipe piece. I even found buildup in my stock header, enough to decrease performance. Since I started modding and tuned the fuel, I haven't noticed any carbon in the exhaust.

Jrfish007

iTrader: (3)

Carbon build up is a sign of one of two things, or a combination of both:

1. the motor is running rich (more common than you than you may think for stock cars) and
2. the use of higher octane than required and/or the use of to many cleaners in the fuel (this includes detergents)

gearbox

iTrader: (95)

i'm betting they were running rich. Even after the mods my car was rich in lower rpms. It's excessive tho and honda needs to tune better from the factory. I doubt the cars I saw had any mods, and I bet they used regular gas since they were all stock.

Titleist71

iTrader: (1)

our cars run rich in stock form.....thats ulev, fuel economy, and vtec for you!

pon55

iTrader: (19)

Lean= ulev. Stock should run slightly lean-never rich! (Thats why we get like 35+mpg)

gearbox

iTrader: (95)

I'll have to disagree. Our cars do run rich to prevent engine damage at lower rpms. I saw it on the dyno and it's true, even with mods. You're thinking about the HX which is a lean burn engine, different from the lx/ex.

Jrfish007

iTrader: (3)

^^^ yup

You get 35 miles per gallon because Honda has an extremely good head design that provides for a better flow of air inside the chamber (better for atomization of the air and fuel) and a more even flame wall unlike most engines. And of course things like gearing and all that come into play.

And yeah, the HX get such good gas mileage (my aunt get 48MPG in hers) because it has a reverse cyclic air flow pattern in the chamber that allows the engine to actually run lean. So why not use this on all Hondas? Because this air flow design robs power from the engine (the engine has to work harder to pull the air into the cylinder, hence less overall power is produced).

pon55

iTrader: (19)

I'll go away now! soory

Jrfish007

iTrader: (3)

^^^lol, that's not like to give up that easily. Anyway, most people think all Hondas run lean, you are not alone. I must have explained this to 25 people now, no big deal.

Excal

iTrader: (2)

dont you wish everyone on here give up that quick.

DaddyFatSacks

I heared even with nitrous, if your not detonating, you should stick with the lowest octane you can. Don't quote me on that, but it does make sense.

senseiturtle

In addition to decent air management, part of the reason you get 35 MPG on a civic is because it's got only 1.7L (or less) displacement. Small motor, less gas.


Now, as far as running lean goes...

Running lean causes an engine to heat up faster. When turbo guys go nuts with a MBC and crank it too high, the injectors max out, and a lean condition ensues. The engine overheats. Same with guys who shoot too much nitrous on a dry system.

The only time an engine should run lean is just after a VERY cold start, when the secondary air injection system (if equipped) crams additional air into one or more cylinders, allowing the engine to warm up faster, as well as get the catalytic converter up to operating temps faster. Its operation is required for proper emissions testing.

Jrfish007

iTrader: (3)

huh? lean makes the engine heat up? I think its the other way around, when you start your car in cold conditions, the engine runs even richer so that unburned fuel can actually reach the cat, which then burns on the cat hence heating it up. If you don't believe, go stand behind a car with a larger engine (or even my 4 cylinder Accord) when it is started and you will smell gas for about 30 seconds. This was one of the major advancements between OBDI and OBD II, the ability to heat up a primary cat at a faster rate. And the platinum catalyst used in the breaking of hydrocarbon is immune to coking problems, hence they moved it closer to the engine to break down unburned fuel and carbon to try and make the remaining two catalyst (located in your secondary cat) more efficient and last longer.

Jrfish007

iTrader: (3)

That's true, but as discussed before the worst thing from higher octane is that you get carbon builds and maybe a little more noisy engine (assuming you only run the higher octane when your on the bottle, you probably won't get much of either of these). The alternative, if you run lean is that your engine will knock, if you don't realize it is knocking (which chances are high since the human ear can not hear knocking above 4000 RPMs, and most knock sensors are only good to about 4000-5000 RPMs and knocking becomes more likely as RPMs rise) you will blow your engine. If the knocking becomes serious, you will blow your head gasket or crack your head(s). Personally I would rather chance a little carbon versus the head or head gasket. IF you would like I can try to explian the chemistry behind all this.

gearbox

iTrader: (95)

My car shakes back and forth at idle in drive when I slightly let go of the brake. Is this due to octane or just a higher compression problem with the head? Can you feel knocking or detonation?

Jrfish007

iTrader: (3)

detonation=knocking=pre-ignition, more or less the different words to describe all the same thing.

As for feeling it, I felt it once in my Camaro, but thats a 393 ci (6.4L) motor and it really wasn't that much, so I would guess with a 1.7L motor you wouldn't feel it, but at low RPM (below 3000) you will hear it. You say this is when you put it in gear and let go the brake and start moving, this sounds more like the engine is bogging down to me. If I remember your car right, you have an auto with a built head. My guess is that the idle needs to be brought up a tad. Sounds like the idle is to low, so when you put it in drive and give it gas, the engine just not producing enough power to push the car at the RPM it's at. That just what I think it sounds like, I had that problem on an older truck I had.

pon55

iTrader: (19)

I never give up! I talked to the honda factory tech that told me this. He said the engine should run lean, Lean meaning opposite of rich. Not as in very lean.
He says the computer is designed to provide a mixture of perfect mixture to lean, but not to rich except if the temperature goes very high!
???????????????????????????

gearbox

iTrader: (95)

Jrfish007 that's right. If I turn the ac on and the rpm goes up 100-200, the shaking stops completely. I've tried to up the idle from stock 700rpms, but I can only do 50rpms higher before the cel comes on.

pon55, this is my a/f ratio before and after tuning. Also note the car is not stock. That rich spike in the lower rpms is still there after pnp head work and header. So yes it does run very rich in stock form. Others who had tuning said the same thing. Around 3k is when it starts to lean out, so if you do alot of driving in the city and only take it to 3k, you'll always be running rich.

Jrfish007

iTrader: (3)

Yeah, I wouldn't trust a tech with more than a my dog's chew bone. Some of them really do know what they are doing, others are not that bright. I used to have a B16A in a '94 civic. I blew the head gasket in the middle of winter, figured I didn't want to deal with it in the middle of winter (about 10F out side), so I took it the dealer to have it done. I told the tech it needed a head gasket from a 1999 Civic Si, he said "but you have a '94 DX." I said I swapped the motors, he told me that was impossible, so I took him out side, showed him the engine in the car, he told me "you have preformed to many modifications to that D15 (D15 is the stock motor and it was a stock B16) and because of that they could not work on it." I went home and did it myself, I decided then that I would never let them do anything to my cars unless they showed me they knew something about cars. Sorry for the rant, but it still bugs me 4 years later, that the tech could even tell it was a B16A.

Jrfish007

iTrader: (3)

what's the cel?

How did you try to up the idle? There are a couple of way to do it.

gearbox

iTrader: (95)

Check engine light (malfunction). I turned the idle screw to make the throttle plate open more.

Mrs014dr

iTrader: (4)

Now I dont feel bad for using 87

S2000man01

iTrader: (1)

most hondas, due to their higher revving nature, run quite rich in the top rpm range. the S2000 itself runs a very rich 11.5:1 in the last 1000rpm or so.

at idle, the cars run VERY lean, as much as 17:1.

in general they run a bit rich if you mash the gas starting low rpm, lean out in the middle, and back to rich in the top end.

S2000man01

iTrader: (1)

lol did you show him the big *** engine stamp that said B16?

gearbox

iTrader: (95)

Ha oops I misread the a/f on that dyno. It's lean below 3k then starts to get rich in higher rpms

Derek-CEO

iTrader: (27)

if ur a premium member, check out this weeks premium news

http://www.7thgencivic.com/forums/sh....php?p=2889819

some inetersting tips in there about gas mileage, especially the one about using acetone?

gearbox

iTrader: (95)

Hmm maybe but acetone eats away plastic...but if it's diluted enough it might not. I sure wouldn't try it. Okay after reading some of that, I would not really try any of those things. Nothing has been proven to last, just to give better mileage. Best thing you could do is throw in some water remover like iso heet to take care of that. I wouldn't go nuts adding stuff to your gas and oil like that.

Derek-CEO

iTrader: (27)

rather discuss those findings in that thread.

senseiturtle

I was sorta wrong, and sorta right.

The air injection system doesn't put air in the engine... it puts it into the exhaust tract.

They go through a description about open-loop operation, but I'm not sure they employ it on later MKIV VW's. This manual was from 1993.

Therefore, you're right. You don't run lean when the air pumps on. I was right on the purpose of the system, to warm up the cat faster.

pon55

iTrader: (19)

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