well see the issue is that even if you have MORE air than we do, the MAF is still counting it. so it's still telling the ECU "hey guess what use this much gas" which could still cause it to run rich.

 

'Counting' = linear signal rise to the end. Go and measure ... If not -then- NOT.

Choking:
Choke is an unnecessary relic, cheapest way in 30's to ctrl ratio. Why double the flaps? Take mercury outboard: from 80's theres no choke flap in its small engine carbs. FYI: as they sell their small line, 6 to 20hp engines, theyre all the same except carb diameter. To get half price 20hp, buy the 6 hp and bore the carb as I did. Dinghy speed initially was 10km/h, now 50km/h. Needs some 'tuning' with the main nozzle (cant get from shop ... plus propeller is far from stock.

I am afraid getting my max 5x stock top speed might be above my abilities...?

And I want to keep VG guts stock - as they do work.

----------------------------------------------------------

The VG/VE development story details must have (?) been like this:

1988: They got the new engines to be tested: VE produced paltry 140, VG 250hp. !? "Now here is a problem... bosses say it has to be vice versa!" Ok. Down tuning VG was easy, just give it to the poorest intake designer. But getting VE to 190 was tough: First, Valves ... "double em" (ala$, no help). Next, "adj cams"! (ala$ no help here neither). Next, "coilpacks." (alas no help) ...

Here executive branch visited the factory... and told design floor to put these coilpacks to the hottest spot - to create fried coilpack revenue... Then somebody said: "throw that blk rubber belt out --->chain it!" ... well, no help there neither.
The last -92 resort: kick in more pressure... Designers winning team 1992 -report to executive branch: "Well, we got it! ...plus 30hp now ready to roll out" (...psst, with double production costs...)

Forgive me VE folks, that was just a VG nightmare

 

Well - my sarcastic smiley unfortunately didn't make it into that earlier post - yet, while that particular mixture meter may not be accurate or perhaps even usable for this particular experiment, that is in effect the sort of thing you are looking at if you are serious about finding " suspected deficiencies" in Nissan's design implementations - you need to define what it is you currently have and experience and then must have a way to evaluate efficacy of any change made and detected.

I suspect I am leaning toward Matt's approach - ie - Nissan got it pretty close if not spot on if all is working as per design.

Screwing around with the ECU needs a controlled environment and a very systematical approach to analyzing what it is that is happening at the hand of good engineering knowledge of the exact product parameters.

Doing it this way (asking what an individual's opinion is wrt a proposed mod) is bound to get you a range of different approaches to solving a particular problem .................. the issue is you need to first define what problem you are trying to address.

Atm I see you suspecting that the ECU is running the motor lean causing a drop in expected possible power output - I cannot confirm that to be the case and I don't think anybody else without engineering data on the ECU can really do that either.

What we all can do is to individually all sod off to a dyno, to make the proposed changes, and to report back here to collate the results and to then dream up a possible successful mod to address the problem ................. unfortunately I am not going to be doing that as imo its just not worth the effort when looking at the performance history of the Max's ECU (however primitive) design and its durability.

 

Generally yes. I have also bagful of real life examples how that approach brings disaster... this is called paralysis via analysis. Typically Besserwissers will be lost there [pls note that I am not speaking of any persons/situations here]

Empirical tst to adjust fuel mixture is not dangerous per se, can give insight what is the situation w/o scientific approach.

 

so what you're telling me is that you have SO MUCH intake airflow that it exceeds the readable capacity of your MAF? I'm still not convinced that the MAF is ignored after 4000rpm either... if that were the case and the ECU shot the same amount of gas at, say 4500rpm regardless of throttle position (or even between 50% throttle and WOT) the AFR would be totally bonkers

but since the only test i saw of your MAF was when the car was parked... the real question would be locking it in 1st gear and getting it up to 30mph, then play with the throttle while watching the (road, as well as the) scope. a quick rev to redline in neutral doesn't give the signal enough time to show its true colors so to speak.

 

MAF is not ignored above 3000rpm. ECU goes into open-loop by design at WOT and/or high rpm. That means MAF, TPS, and CPS are the only sensors working above 3000rpm.


IF you think your MAF is killing you, stick a multimeter on it while running. it'll scale 0-5V based on 1-100% calibrated flow. If you hit more than 5V on it while driving, then you need a bigger MAF and to reprogram the ECU. If you get a bigger MAF, then you need bigger fuel injectors too, since they both run out about the same power levels- which is around 300HP.


No, the pin 43 thing will not work. running the engine in simultaneous injection will only cause the duty cycle to go lower, which means less fuel.

 

Not really.

If you take our South African situation where we don't have O2s and yet the motor performs well living off of a pre programmed factory map, then one could easily use the engine speed and TPS signal to fairly accurately determine engine load and as a result fuel requirements without even having to look at the MAF.

Also - I suspect that with huge throttle openings, one effectively transfers distinct "gulps" of air via the inlet to the MAF and those gulps are not what the MAF will accurately/timeously be responding to - iow - those gulps may very well setup a funky oscillating compensating reaction with the fuel quantity control in the ECU that could completely screw the air-fuel ratio.

There is but one way to confirm what is really going on - get a meter and stick it in your Max's butt

 

This is how it has to be - thus kills any 'benefit' ...even to test.

Stationary, as can be seen, my MAF currently gives out 3.5V at 6.5krpm

 

then your MAF isn't maxed out. you need to shove more air through the engine via porting, better manifold, positive pressure, etc..

 

ooo I hate it when that happens. feel so violated.

 

Sorry - didn't realize your middle name was Max

 

All folks: Thks for good brain wrestlin exercise... Matt, I like your insight - hate it killed a pinhead dream43.

Still, must test that effect [if any] as time is ripe..

 

Feel free to test... but I'm pretty sure you know what results will be at this point.

..... And I'm not trying to be pessimistic. just realistic. Dreamers see an orange a grove of orange trees. Engineers see an orange as a simple snack.. Just a snack... It is what it is. It won't ever be a grove of orange trees, even if it wanted.

 

now will an SA ECU resort to the MAF if the TPS is unplugged or faulty? Also do you know why the m/t and a/t TPSs are supposedly different?

 

Haven't got the foggiest on either score.

I suspect the TPS is critical though - way more so than the MAF which is why you can unplug the MAF and still have a working and drivable vehicle. With MAF and no TPS there is no indication of experienced load on the motor to the ECU and I thus suspect the motor will just die.

M/t and A/t TPS differing? - just don't know - suspect there is the involvement and dependency of the TCU on this baby in the case of the auto so that may explain it.

Either way - not going to unplug the TPS to see if the MAF alone can make the ECU keep the motor running

 

well, I will try it once i get my car back together. I'd always thought that the hard TPS was for m/t's ECU, and that both hard and soft were used in the a/t ECU. I actually didn't know that the TPS was the main source of map info. Which means that i may now have an idea of what's causing the abominable stumble i have.... so kudos if cleaning out my tps harness fixes the my openloop stumble.

 

FSM says neither TPS switch is used. "Zero pos switch utilized only in TCU test". Easy test is unplug and see if this claim is true...

 

Well - to be honest I don't either. I am talking from a purely engineering standpoint and related experience - no Nissan design info at all.

 

well for me it wouldn't matter about the TCU anymore since i don't have a/t anymore. but i could see if it does weird stuff to the engine.

and to LVR
hmm well i mean, if you tested TPS-free operation on your car what's the worst that can happen? it shuts off? runs weird? plug it back in and it's fine. my max won't be crankable again until much later in the month. long story about that.

 

Let sleeping dogs lie My TPS has undergone major heart surgery - if its possible I prefer not to disturb it unless absolutely necessary

Nothing to do with anything technical or my unwillingness to experiment or help out

 

Thats about it. No harm - just confirmed info.

 

...then MAF has been fried ...

FSM EF&EC 140:
- At idle, output voltage is 1V-1.3V
- At 3000rpm 1.8V-2V
- No mention wassup at 6000rpm ... but if linear, then 3V.

 

oh ok. can't blame you there. well then i'll just report back in a few weeks when i get around to testing it.

 

Ok, did the actual measurements:

Note that following numbers are for reference only, because:
- Each stock MAF's components do vary from unit to unit
- Charge Voltage varies between engines ... alt, batt, harness condition etc
- Digital multimeter error margins between multimeters is quite wide.
- Airflow: filters, tubing etc differ between vehicles

My modded MAF measurements; measured from MAF Pin B.

Note: Ground probe has to be on batt GND, FSM warns of possible transistor damage...:

Engine OFF, ACC, 0.3V
1.3V - idle steady
1.67V - 2000rpm steady
2.01V - 3000rpm steady
2.34V - 4000rpm steady
2.54V - 5000rpm steady
3.5V - one push to wide open throttle 6500rpm

 

I think that you should state the exact load on the motor at the time of those measurements
- any change/different load will have a huge effect on the measured (required) airflow to maintain/reach those revs.

Also - I would suggest a better way to determine the actual "stressed" state of the MAF (with the view to seeing if you are indeed even able to supply as much or too much air as you suspect you are) is to get those measurements at WOT while only passing those rev positions (in a single pass from bottom to top revs), because only then will one be measuring the amount of air the engine is consuming at worst case fuel consumption (full load).

 

Havent seen any of your actual measurements. Waiting...

Measurement were made the garage, were made like this so they can be used as reference for MAF output voltages using dmm. Steady is best, pumping gas gives flow rate fluctuations. No repetition errors...

Best way would be a memory scope and diagrams printout. Most ppl like me dont have such, thus it would be not of real value. Interesting, yes ... maybe youll provide?

A piston sucks the same amount of air regardless how much stuff is in the trunk. How much gets in? ... all depends on rpm, how much engine is choked.

 

Exactly - throttling is used to govern the engine speed and the engine load will effect the amount of throttling required directly to maintain a given engine speed (read here all IACV to a certain extent with such low loads at stationary conditions) - hence my suggestion of the requirement to do this at WOT where absolutely no throttling is present, the IACV's effect (throttling bypass) is basically nullified and the only real thing governing the amount of air flow into the motor is the speed of movement of the actual swept volume of the pistons and the design of the plumbing to and from those cylinders - ie - motor is using as much air as it possibly can to produce all its power at that speed without any variable throttling.

Note that I am not criticizing your method of measurement - I am just trying to help you get to a point where you can confirm that your motor is indeed running lean at WOT as you suspect ................ keeping in mind what the thread topic and goal is.

I will measure and post also at stationary conditions for you, but as I said, those results cannot possibly be used to reach any conclusion wrt the mixture quality and the suitability of the MAF to measure the engine's maximum airflow accurately or the need to possibly add extra fuel.

 

I did measure the intermediate values b/c I suspected MAF is flattened out - like O2 is lots before 6.5k rpm. And thus presented my wrong suspicions flattened here by the numbers...

At WOT theres the rpm limiter dropping engine intermittently dead. This causes fluctuation unproportional increase seen in the last measurement.

IACV can be easily clamped out, in my case its effect is below maybe 3%.

 

Ok - my measurements of the same parameter then...............

Environment parameters:

Vbatt = 13.8V

Valt=13.82V

Temp of metal of inlet tract just before TB = 62C

Car driven for about 40 minutes and engine sitting at 82C (thermostat outlet housing - IR thermometer)

Ambient = 19C

1426M above sea-level


Engine OFF, ACC, 0.2V

Measurements with AC and all other electrical drains off - cooling fan on radiator off, auto in park

1.12V - idle steady
1.57V - 2000rpm steady
1.88V - 3000rpm steady
2.11V - 4000rpm steady
2.38V - 5000rpm steady
2.89V - one push to wide open throttle 6500rpm

FWIW - auto in D or R gets me an idle value of 1.33V demonstrating exactly what I was talking about earlier - ie - exact engine load and throttling influencing the measurement tremendously.
Sorry - but I don't yet see any theory being "proven" wrong because of these particular measurements ....................

Again - see my observation re the load on the motor influencing the airflow rate, and as a result of that, by implication, me saying that at WOT load at those particular revs, you will have a complete shift of the whole curve to much higher air flow values

 

My theory of MAF signal flattenin was wrong.

I know all theory-kings claim the 'load' -issue that way. Still its not true... Also, idle issue doesnt apply here:

The rpm would drop radically down when u put in gear. But it doesnt. Why? IACV... Test how it goes after disconnecting IACV.

The 6x500cc displacement is stupid steel company of buckets. It knows just 'his' own steely barreling pain just like me, dont care about anyone else

When piston goes down, its pulled via the rod. 'He' cant help being pulled down

What happens 'behind' the rod (contrary forces against the crank rev) ... it doesnt 'know' wassup. Piston is just being pulled down. Regardless of what...

As piston goes down, the displacement becomes under vacuum. The vacuum is filled from intake vacuum cacophony with its fluctuating bangs, air currents. At idle, this vacuum is influenced via IACV during idle. IACV has tremendous effect... on all forces incl airflow - as it adjusts to keep rpm level in all situations - controlled by ECU, watchin rpm.

After IACV is left into the horizon, =throttle opens, its effect is about nil.

 

No man - come on now.

Putting it in gear increases load - ye?

With no IACV engine revs would drop (assuming throttle is not touched and ECU doesn't try to perform miracles with timing tweaks) - yes?

IACV opening effectively says you need more air EVEN THOUGH THE REVS STAYS THE SAME - yes?

So if all is yes, then LOAD DEFINITELY DETERMINES AIR FLOW AND THUS THE SIGNAL THE MAF WILL GENERATE .............. AND IF LOAD DETERMINES AIR FLOW REQUIREMENTS AT IDLE IT STANDS TO REASON THAT IT HAPPENS AT ALL REVS - whether the IACV is there or not.

 

Putting it in gear increases load - ye?
- yes

With no IACV engine revs would drop (assuming throttle is not touched and ECU doesn't try to perform miracles with timing tweaks) - yes?
- yes

IACV opening effectively says you need more air EVEN THOUGH THE REVS STAYS THE SAME - yes?
- ECU is the one detecting rpm drop. Increases injection, airflow is increased via IACV to fit the change. MAF is not the decider, ECU 'ignores' it at idle.

So if all is yes, then LOAD DEFINITELY DETERMINES AIR FLOW AND THUS THE SIGNAL THE MAF WILL GENERATE .............. AND IF LOAD DETERMINES AIR FLOW REQUIREMENTS AT IDLE IT STANDS TO REASON THAT IT HAPPENS AT ALL REVS - whether the IACV is there or not.[/QUOTE]

- no capital letters pls, takes all fun from communication, I'll drop out.

- IACV is the dummy part of an adjustment circuit for idle, keep it level on changing load. IACV is not used when MAF & flow kicks in above idle.

- MAF gives signal related only to drawn buckets of air. Buckets can be calculated from rpm.

- Load depends on granmama's stuff in trunk... pistons dont care.

- Used air volume is always constant at same rpm, WOT. Pulling a fly or a train wont change that.

 

LvR i suppose it depends on your definition of "load" as to whether "load" influences the MAF signal. Yes, putting car in gear requires more power for the engine to maintain its RPM. Your definition of load is 'any amount of resistance against the engine'. So putting the a/c on means more load, same with locking the steering wheel. But if you are at WOT then then your definiton of load doesn't change based on how heavy the car is. WOT will pull x volts at x rpm no matter what, if at WOT.

Wiking's idea of load is more static, in that load always depends on the weight of the car in motion. Which means if the car is sitting still the load is therefore zero, by his definition, because you aren't really doing anything. By his definition, you can put tons and tons of junk in your car, but when not moving , the car has 'no load'.

as far as i am able to tell, the power valve's idea of load depends only on hitting 50% throttle or higher at a low RPM. The way I see all this is that increasing load influences the MAF signal indirectly. MAF signal is a byproduct of throttle position, and more load requires more throttle position to maintain RPM. Putting car in gear increases how much load the engine has to spin against, and in order to maintain idle, IACV bumps up the amount of air coming in, MAF sends more volts. So "load influences MAF signal" is only true in the sense that "increased load requires more air and more air means higher MAF signal".

Which makes both of you right. Say you're at 10% throttle level at 45mph and start climbing a hill, open it up to 15%... load goes up (gravity), throttle position goes up, revs stay the same, maf signal goes up. That's a good non-idle, non-WOT example.

 

Its better to keep IACV plus idle on separate discussion, that issue is not really MAF related...

Of course MAF signal is affected by throttle butterfly angle.

The load issue... can be best explained when no throttle at all - like in diesel direct injection is the case. Air amount is directly tied on the asphalt flowing past...

 

Another try. 1st: Keep Idle adj out from MAF.

Idle adjustment is computer controlled environment. There rpm fluctuation kicks ECU in action. Actuator is IACV stepper motor. Smallest drop in rpm, is followed by ECU drivers supplying each stepper motors 3 wiring coils, one after another. This closes/opens the idle valve.

BUT. You cant see it. You have to be measuring with a scope. Done that. Seen it. No connection with MAF.

----------------------------------------------------------------

Lets forget the idle, please.

Simplifies Flow Example w/o throttles of MAF's:

Two diesel trucks connected with a bar, a. and b. Driving all the time constant exact 50kmh. The front truck a. has same gear always connected. All pure piston up down mechanics connected to asphalt...

1. The front a. is pulling the b., the one behind. Air flow sucked through a. intake has value F.

--->Swap from pull to push, 180 degree load change:

2. Front truck a. fuel supply is cut. The rear b. starts pushing. Air flow sucked through truck a. has its intake flow value exactly at F.

 

hmm, true. tho you do come up with an extreme-ish example. i assume you meant that it's like a manual transmission.. if in motion then engine is forced to spin, rather than a/t where if the engine loses fuel then the engine brake will disappear and rpm will drop to zero.

 

The 'breathing' is pure mechanical process, and xtreme simple in that.

Mixed in this simple process is typically fuel delivery, vacuum ctrl this and that like ign, valve advance, carburettors, computers, filters, A/T & whatever... ALL this gives the feeling discussed. The feeling is true feeling

When all those adjusting appliances are counted, of course the load has an an true effect in fuel delivery and airflow. But pure cylinder breathing is directly and only related to rpm.

Fisherman thinking like a fish gets plenty fish: Pure mechanical piston up/down never feels but heat and 'his' constant fly direction reversals. Ask 'him'

 

In that case I dont know what it is we are discussing.................

I never said MAF is the decider - it is simply reporting ito voltage what it is measuring when the air mass moves past it - whatever determines the load (work required to make the engine do what you want) to have increased and tells the IACV to open more, is irrelevant. The fact is that more air is entering the motor as a result of load increase on the engine - the MAF may measure it but its a response to the load change and is not the governing factor at all.

Measuring air or fuel consumption for a static "load" (ito weight of the vehicle) while stationary serves no purpose at all (because the weight of the vehicle has no bearing on that measurement) - you are basically measuring how much air/fuel you need to overcome engine friction and losses - that is all.

Way too much said on the topic as it is.

Simple fact is you need fuel to make X amount of power - you want more power, then you gonna need more air to make the power during combustion - I cannot force anybody to understand that - its just a fact of life.

 

If this mechanical example [see above part1.] is taken nearer to gasoline, then... b.


b1. First we add MAF into the equation (vehicle no1. engine intake) seen above. I name the resulting signal maf_F. This signal stays precisely the same throughout our new tests; the both cases 1&2. MAF output doesnt give out any LOAD change -signal.

b2. Second, we add a choke butterfly, and start choking. Lets put the choke at halway and keep it there. Now the maf_F -signal has been changed. But during comparative pull/push -load tests 1&2 --->NO CHANGE. MAF output doesnt give out any LOAD change -signal.

This added choking variable vacuum b2. is used as gas delivery control method quantity in gas injection -or- carburettor engines (stupid relic from 30's). It results in the user feeling of load, and as such is true. Still MAF doesnt give any LOAD-signal, because there is none. MAF output doesnt give out any LOAD change -signal.

maf_F is all rpm -and- throttle opening. Be it measured at garage or hiway - NO LOAD signal no.

 

but would you agree that in most normal driving situations, they correlate? that's what LVR meant by all that. you can find ways to make it untrue, but very rarely will someone have a vehicle towed while in gear.....

you're just being what we call the "devil's advocate". if you've never heard that term in the land of Wikings before, it has nothing to do with the real devil.. just a figure of speech.