Les

You guys with all the fuel ratio performance mods may know, but it seems that stepping on the gas progressively and gradually(but harder than usual) gives as good or better results than WOT, and perhaps with alot less gas pumped into the engine and not used. The fuel economy is poor enough without dumping unused fuel. Does this make any since?

turbojeff

iTrader: (30)

If you look at some dyno graphs you'll see that at lower rpms it takes the computer a bit to figure out that the car needs to be full rich. This may be programmed to reduce emissions also.

In general the fuel injection system works on "speed density" information. That is the computer likes to know what the boost pressure (temp and pressure is needed for density) is and what rpm the engine is at. It will add fuel accordingly.

I don't know what type of "accelerator pump" type action the injectors give based on throttle position change rate. I doubt that you will notice the difference in gas mileage unless you plain old stay out of the boost.

oneflytrini

iTrader: (1)

If it brings a smile to your face, why not?

Les

I guess that is part of the answer, what happens based on just throttle position before the computer has a chance to read anything? If it was mechanical fuel injection there you might expect it to perhaps dump fuel based on throttel position(just a guess). It seem like it could be charted based on observed fuel read outs vs HP vs Throttle position. Don't some guys here read fuel richness under load, etc?

turbojeff

iTrader: (30)

Yes it runs rich under full load. It does not run rich under full load below about 2500rpm. Above that the cars run really rich in stock and mildly modded form, a/f ratios are below 10:1.

The throttle does not move without the TPS knowing it moved.

JONSKI

Do you have an automatic?

ijneb

WHY are you worried about gas milage?

jimlab

At WOT, the ECU switches to open loop and reads from the pre-programmed fuel maps based on rpm, boost pressure, and intake air temperature. At part-throttle and idle, the ECU is in closed loop and is reading from the O2 sensor to approximate the correct amount of fuel to maintain "ideal" or stoichiometric (14.7:1) air/fuel ratio for best mileage and lowest emissions. Closed loop is only intended for light load cruising.

What you're accomplishing by accelerating at part throttle is leaning out the air/fuel ratio, so of course it feels as fast or faster than stomping the gas. You're also running a very good chance of popping your engine.

oneflytrini

iTrader: (1)

So with the FD its better to be either off of boost, or WOT?? No in-betweens when driving?

dubulup

popping an engine because you weren't at WOT????? You've got to be kidding...right?

TIP # 49: Accelerating should only be done at WOT.

if you're not at WOT, then the butterfly valves in the throttle aren't wide open...i.e. not allowing maximum air in (yes, I understand a turbo blows air into the motor, but if the plates aren't fully open that air is "interrupted" some what and not as much is entering the chamber), so how exactly is not letting maximum air in going to lean out my engine enough that it blows?

Please fill me in on what I'm missing...

*edit* because I accelarated all day long at part throttle, with an open wastegate to keep it closed and I'm yet to see any harm.

maxcooper

Is this thread about getting maximum acceleration by rolling on the gas versus stomping it down in one quick motion?

-Max

jimlab

No, I don't believe I am. Did you see one of these ( ) anywhere in my post?

You're missing the fuel maps for use under boost. Closed loop is not intended to add fuel to compensate for boost. Re-read my post and see if it makes more sense the second time around.

Good luck with that.

KaiFD3S

iTrader: (37)

I have to agree with Jim, the person I bought my car from said he replaced the engine due to it blowing....I asked how did it blow and he said that he was in 4th gear at low rpm at abort 2500 and when he stomped on the gas it blew, I asked him if he was all the way to redline and he said that it barely reached 5500 rpm and it blew....

jimlab

Stomped on the gas in 4th gear at 2,500 rpm? That's about 45 mph with stock tires.

KaiFD3S

iTrader: (37)

Yeah, I did'nt ask him why he did it but that was the outcome...he was on city streets when it happened, might have been lazy to shift down...

PhoenixDownVII

I think what "Nailing it in 4th at 2500" is, is putting a heavy load on 4th gear, which is bad for the motor to attempt...and can be avoided by shifting down into 3rd. I almost never gun it from 2k rpm. If I am going 40-45 in fourth and the road changes to 55mph, I almost always drop to third to get moving, or I'll just cruise faster and faster...slowly.

Now, the question I'm assuming in the thread is: if you're not in a heavy load even, rather, you're going 50mph in third (should be higher)...from this point does it make sense to simply floor it? or press it "As you feel it wants more".

I dunno the technicalities, but I'm not one for "flooring" the pedal (100%) when flooring it 75-80% at that point doesn't make the car go any slower...why push the pedal past the "Response" you never get past that point? Until it meets it there? I guess Jimlab and others might say even though you don't feel any difference in power, what's going on in relation to how open the throttle is very different (figures).

dubulup

no, didn't see a smiley
no, didn't make more sense, but I have another question
THANKS!!! 5k miles and rolling...
so, you are saying the ONLY thing that brings the ECU out of closed loop is the WOT signal. Boost and rpms have nothing to do with this? Damn, I'd hate to think Mazda's engineers thought there was only one situation boost would be useful.

not that I really care...my stock ECU is in a box on a shelf. Just curious as to what led you to the logic behind this statement Personally, I thought this thread was more about what Max said.

how are you agreeing with Jim? You're situation, is the exact opposite of what Jim said. "If you don't stomp it, you will blow your engine"

jimlab

From Steve Cirian's web site...

The computer has a pre-programmed "map" of what it should be doing in terms of fuel injection for given levels of RPM, load, etc. If the computer is supplying fuel to the engine based on these maps, it is operating in what is know as open loop mode. This is the simplest mode of operation. It is also not the most efficient.

Closed loop is, as the name would imply, a feedback loop. The O2 sensor feeds information back to the computer, which then adjusts fuel injection based on the information it receives. Closed loop mode is used most of the time for normal operation. In closed loop mode, the computer uses the feedback from the O2 sensor to determine mixture. The ideal mixture is assumed to be 14.7 parts air to one part fuel. The 14.7:1 ratio will supply 14.7 pounds of air for each 1 pound of fuel.

At full throttle, the computer will drop into open loop mode (not using the feedback from the O2 sensor). This is done to ensure that the engine will be supplied with enough fuel so it doesn't lean out and experience detonation. The maps used for open loop mode typically assume that the mixture should be extra rich to prevent detonation. Open loop mode is also used during engine warmup since the O2 sensor may not yet be warmed up and won't be feeding back correct information.

Possibly. The fact remains that "rolling on throttle" (part throttle acceleration) under high loads is NOT a good way to ensure that your engine stays healthy.

KaiFD3S

iTrader: (37)

Yes, it may be the complete opposite of what Jim is saying, but from what I am saying is that, he was in such a low RPM that it did not eve reach over 5500RPM and engine blew, the point in which he started to go WOT at such a low RPM micht have had the engine in a close loop and that may have been the cause of blowing...

dubulup

this makes no sense.

dubulup

fair enough...

turbojeff

iTrader: (30)

Makes sense when you look at my post. In the range of ~2500 rpm and lower the stock ECU runs the engine relatively lean under WOT. I've used a wideband on my car and seen this.

I'm not sure what other experience you have but I don't think accelerating at part throttle exactly equals "a very good chance of blowing your engine".

poss

iTrader: (5)

Exactly.


People overplay how "fragile" this engine is. It's rediculous.

For anyone who has blown @ part throttle, there was probably more to the story.

mad_7tist

like the engine had 65,000 miles on it....

turbojeff

iTrader: (30)

Some more food for thought with the factory ECU and part throttle acceleration.

I ran a wideband for a few days in my then stock ECU'd R1 with Efini y-pipe, DP and cat-back. The car runs really rich in any boost condition. It is nearly impossible to get a seq twin car to boost anything less than 3-4 psi.

IIRC anytime the ECU sees significant boost it throws out any closed loop operation and goes into open loop. When running in open loop the mixture tends to go full rich.

This is exactly what part throttle acceleration will do, run the car full rich.