PhilB81

Isn't the oxygen sensor past the throttlebody? So shouldn't it adjust the fuel going in for the proper mixture? Or do you mean the TB introduces turbulance?

I would assume that in any case a direct injection would have a better efficiency than one where the mixture occurs earlier in the manifold, correct?

Sorry, I feel like you need to spoon feed me, but usually I try to properly understand something before I 'go' with it. (I'm not implying I don't believe you btw)

I hate cars

Spoon feed, not at all.

It's not about the mixture. The computer calculates how much fuel to inject and the 02 checks that caluculation after it burns and corrects if necessary.

The engine suffers pumping losses when the TB is closed. It takes power to pull the air in and cause the vacuum in the intake manifold. Remove the TB or open it completely and you've made a small difference in VE.

Diesels for example are unthrottled. This is also the reason they go through air filters more quickly, they're pulling in the same air at idle as they do at wide open throttle. This is part of their reason for much better fuel economy though the super high compression ratio is the main reason.

PhilB81

let me bring up CAI for a second, I thought you didn't really go for all the mileage gains people claim. It has been a while since I read that thread though.
Now, to the TB valve, I agree with the engine needing to put some effort in generating the vaccume in the intake manifold. But, the engine will generate a certain amount of vaccume in its piston motion, and at some point there must be some restriction, either by a constriction of the TB valve or a smaller opening of the intake valves. (otherwise the engine will just rev up).
Tell me if this is wrong: The vaccume gets created by the piston, the intake valves are closed (so effort is already spent) now comes time to fill the combustion with a specific amount of air. So this is the part where I get confused. You already went through the effort of generating the vaccume, all you have to do is move air into the chamber, and wether you have a restriction on the TB, or a small valve opening, or a big valve opening but shorter in time the point is still that you only can move X amount of air, no more no less otherwise you'll either rev up or down. Basically, the restriction has to come from somewhere and I don't see why one is better than another. What it seems is we're saying is move the restriction as close as possible to the ignition chamber and it's better, and that I don't see why. Btw I'm only arguing constant velocity/energy output, because I can understand how one scenario could yield a more potentially more responsive engine.

SouthernBoy

Ozygen sensors are mounted on the head pipe which with our engines is just after the primary cat since there is no exhaust manifold.

PhilB81

I was refering to the o2 sensor in the header, on the intake side, not the exhaust.

SouthernBoy

???

Not to be viewed as argumentative, but our engines not only do not have headers, but they can't even have after-market headers due to the fact that there is no exhaust manifold. oxygen sensors are installed in the exhaust system, almost always in the head pipe.

Can you tell me which particular sensor to which you are referring? I'm just trying to understand for future reference/knowledge.

PhilB81

Okay I'm probably out in the weeds, so correct me where needed. I thought there a MAS (mass air sensor) on the intake, the followed by an o2 sensor, then the ignition chamber then the first catalytic convertor and then another o2 sensor. Is that incorrect?

Thanks

I hate cars

Our cars don't use a MAF since they're speed density.

It goes airfilter>throttlebody>intake air temp sensor>intake manifold>combustion chamber>then out of the exhaust port into the header and the primary 02>convertor>secondary 02.

Basically, the ECM calculates the A/F then it's combusted. The 02 is in the exhaust to check if that calculation was right based on the oxygen content. There's no 02 on the intake side. The sensor needs to be above 600 degrees to work.

The secondary 02 is only there to measure catalytic convertor efficiency. All the computer looks for is a difference between the primary and secondary sensors. If they read the same, the convertor is not functioning.

Only the primary 02 on each side is used for engine fueling calculations.

PhilB81

k thanks. I have not played with an engine recently as you can tell.

I was using what little I remeber from an old gen integra and crx.

SouthernBoy

Gentlemen, the 3G TL has no headers because it has no exhaust manifolds. The primary cats are bolted directly to the heads. The O2 (oxygen) sensors are affixed upstream of the primary cats just outside of the head (I was wrong in my earlier post about their location).

"I hate cars" is also right about the fact that the TL does not make use of a MAF, but rather the speed density algorithm. This is the same methodology use by Ford for their V8 Mustangs from '86 to '88, when they switched to a MAF system. Curiously, Chevrolet went in the opposite direction.

I used to think that O2 sensors were just sophisticated thermometers, measuring and comparing leaner mixtures (hotter) against richer ones (cooler), but that is not the case. They sense a change in the ion dispersion in the exhaust causing a voltage change in the sensor.

Learn something new all the time.

I hate cars

I remember the early one and 3 wire "narrow band" 02s. They were accurate at stoich but not higher or lower. The computer basically used it to check crosscounts to keep the convertor happy. We're lucky that our cars use a wideband that will read a wide range of mixtures and allow the computer to stay in closed loop at WOT.

I call the primary convertor/tube a header just because it's easier than explaining it to people. I guess technically the header is built into the head. It would be interesting to attempt a port job on one of these.

adrian_04tl

hell, when i bought the 6sp, i bouhgt it to have fun n rev high. worry about the gas milage when youre at the pump. by then...its to late to do anything about it. lol

94eg!

Honda uses TPS (throttle position sensor), IAT (intake air temp) and MAP (manifold absolute pressure) sensors to guess how much fuel & ignition timing to use. It's judgment is checked and corrected by the 2 primary O2 sensors in the exhaust (before the catalytic converters).

I hate cars: I was unaware that the TL used wideband 02 sensors that run closed loop at WOT. I have always wanted to build a system like that for my Civic. So long as the sensors function properly, you never have to worry about running rich or lean...

SouthernBoy

I had an '88 Mustang LX 302 which had the EEC-IV ECU, a real marvel at the time.. perhaps one of the best ECUs made back then. It would operate in a closed loop from startup to full operating temperature as I recall (corrections here are most welcome). One way to "fool" the ECU was to cool the intake stream and I did this by installing the largest transmission oil cooler I could find. It was made by Hayden and looked like a radiator for a motorcycle. I then routed coolant through it before the coolant entered the square block behind the throttle body which housed the ERG valve. With this little trick and a bump of the timing to 12 degrees initial, the engine was very responsive and ran better than the Hyper-Tech chip I had tried.

Ford went to a MAF for this engine in 1989. While MAFs allow a broader range of mods to an engine, they are fragile and I personally don't care for them. I blow one out in my last car, a modded 2002 Altima SE, to the tune of over $500 for a replacement.

SouthernBoy

I would bet that Honda did this to get the ULEV rating for this engine. Also, there is a benefit in the low to mid range throttle response. But it sure would be nice if they had real exhaust manifolds for the heads so that after-market companies could make headers for them. As for porting the heads on the TL... yeah that would be cute.

rockstar143

iTrader: (6)

update:
I drove my car a few times at the shift points listed previously and managed to bump up my mpg from 20ish to 22. And that is with quite a few "fun" drives on the tank mixed in. I'm trying this tank to be good and see what I can yield.

Nice to know you can get pretty good gas mileage by changing shift behavior!

PhilB81

did you use to hold gears longer or shift sooner before?