Go take a look at post #37 in this thread as well, it was posted by Steve and shows a run 2nd gear to 3rd gear at WOT and the AFR in that run is rock solid at about 13.0AFR. That seems to be a run from one of Steve's very nicely done tunes.

Sorry about the side track in this thread with the fuel tank, I'm done with that now. Just something that needed to be checked.

sub'ed

subscribed

I may be late on this thread and not have enough knowledge to total understand but I am wondering:

Is the best acceleration tuning only available when the WOT switch is triggered.

If this is the case would there be an opportunity to add a vacuum switch to the system that could close the existing WOT circuit upon acceleration at less than WOT?

This could run in place of or parallel to the WOT switch.

If there is not a vacuum switch that opens with vacuum or is calibrated correctly, then some type of electronic solution could be had using a standard vac sensor.


Keith in Sacramento
85 Carrera

not sure what you are asking.. the WOT switch is a mechanical contact switch... it knows nothing about vacuum....are you saying you want to "override" the WOT signal if the vacuum is above or below some level?

I'm sure the Steve Wong chips have some adjustments on the non WOT map to make the engine run smoother/etc. but you would have to confirm with him.

From the disscussion it appeard that the WOT switch triggers a different and more aggressive fueling and or ignition map which is where they get much of their total power improvement from. This is what we see in the dyno charts.

However, during cruse I belive the motor runs on a more consertive map.

Or, or-on-top-of-this, I think O2 sensor is part of a logic loop that modifies the maps untill A/F ratios achive a target level A/F level consistant with emissions and fuel economies with a stock chip.

The chip tuner could and may change the base map a bunch but it probably would not have much of an effect during cruse or part throtle as the O2 loop would modify it untill the goal A/F is achived.

I suspect that with a modified chip the tuner might play with this goal A/F level and set it at richer level to some degree. Then the O2 loop will work to maintain it. This would help part throtle response to a degree but at the possable expense of emissions and or fuel economy.

That is, if best emissions is at an A/F of 14.7 the stock chip will use the O2 sensor to maintain this. If best acceleration is at 12.8/1 then the O2 loop could be adjusted to achive this and throtle response would be at it's best.

This may be simplistic as the stock O2 works great at 14.7/1. However, I am not sure if is works well at 12.8/1.

However, if one drove a cruse all the time, a lot of fuel would be waisted and one may even end up with some carbon build up if this goal A/F was set to run realy rich all the time. I dought the tuners go this far.

In any event some type of comprimise would have to be reached here to ballance throtle resonse with efficency.

Again, if I followed correctly, when the WOT switch is triggered, the O2 senser is taken out of the equation and the base map or a more agreesive map is then used.

Thus, instead of having to push the throtle all the way to the floor to triger the WOT switch. A vacunm sensor could be added to the intake manifold between the throtle plate and intake valves.

At cruse there is a high level of vacunm and the switch would remain open.

However, when one begins to open the throtle plate the vacunm is reduced, this loss of vacunm could be used to triger the WOT circut and enable the more agressive map instead of waiting untill the throtle is opened all the way to triger the switch.

There are two options here. One is to add the vacunm switch in tandem with the existing WOT switch so ether one can triger the map. The other is to dissconect the WOT switch and just use some type of vacunm switching to triger the power maps.

As I think through this, I now understand that to get the most power out of my car, I need to pust the throtle all the way down to triger max power. If the carpet or poor adjustment is limiting throtle travel, maximunm power will be comprimized.

Again, I do not realy understand this to any great degree. I just want to make the 85 911 I just purchased go faster.

Keith in Sacramento.

I wonder, could one just put a switch on the dash that is wired to the WOT switch.

Then, stock or tuner chip, when running autox or track events the switch could be trigered putting one in race mode.

If needed a simple rpm activated switch could be added to the circut so it is only trigered above somthing like 2000 rpm.

Does unpluging the O2 sensor, do the same thing?

Questions, questions????

The WOT switch takes the system into open loop where the O2 sensor information is not longer processed. Why would you want to modify this? Think about it this way: If you are not at WOT you are not demanding maximum power from the engine to begin with. The power bottleneck is the throttle and NOT the timing map. You could depress the throttle more if you wanted more power. While not being at WOT a more agressive timing map would only make to back up on the throttle under similar conditions.

Once you need maximum power you quickly reach full throttle (WOT switch activates) and that's when the open-loop maps will be used. So there is really no point in making any changes or faking the WOT switch at lower throttle positions. Remember, this is not an RPM-activated transition but purely controlled by power demand (throttle position) - even at low RPM's the WOT maps are used when you put the pedal to the metal.

Ingo

Ingo,

I am not an expert.

If there were no differance between a stock or moded chip at WOT, would there be any reason to go to a moded chip?

What if the stock chip got better gas milage and was better for the enviornment.

What if the moded chip was more responsive at throtle onset and part throtle applications?

Yes you can push the throtle down all the way for max acceleration which is fine to get around somone on the street.

On the track, part throtle operation and response when dancing and balancing a car near the limit in a corner at 5500rpm, or trying to get a nose in on somone, is just as helpfull as WOT down the straight.

If I understand correctly, because of the design of the system, Part throtle O2 modified paramiters must be a comprimise, stock or moded chip.

You can get max effency, max part throtle power, or a comprise between the two at only some of the points between.

A race only chip could be done if the narow band O2 would function at A/F levels needed to support peak power, or if the O2 could be writen out of the equation, but then it would not work well on the street long term.

Using a vacunm refrenced switch in place of the WOT switch might reduce these comprimises.

There are still other comprimizes with the barn door AFM, but it could be better with out much more expense.

I may be off base here.

Now that I better understand how the 3.2 Motronic system works, I think I see the need for a chip.

To me the opertunitys become setting the system to work closer to ideals for the gas available. One that takes advantage of the better breathing capabilities available with modification on the exaust or intake side (though the AFM and O2 should compensate for this to a degree). And moving the comprimise from cruse effency to a setting that more favors part throtle power / response.

Keith

These chips (84-89 Carrera) have 3 fuel maps:
Idle Fuel Map
Part Throttle Fuel Map
WOT Fuel Map

It is not a good idea to run the WOT map (forcing it) while in part throttle, the WOT map was designed and calibrated for metering fuel for Wide Open Throttle and trying to use it in Part Throttle will NOT help performace.

If you wish to get better throttle response most tuners tune the Part Throttle Fuel Map for this. Basically, you can add fuel to the part throttle map in the higher load points of the map. Which will result in richer AFR (say 13.2 or so) when you step on the throttle for passing or quick acceleration needs. If this is the goal then it's best done by tuning the part throttle maps.

But tunning these can take many long hours even with a dyno, so if you really want better throttle response buy a chip from a tuner that knows these cars. Steve Wong at www.911chips.com has done this throttle response tunning with much success. I know first hand, I have one of his chips and have seen the results via my Wide Band O2 monitor, I have compared AFR readings from the stock chip and his chip + seat of the pants. His chips work! I'm also sure other tunners have chips that also work but I really have only tested Steve's so I can't comment on the others.

If you wish to try and cheat the Motronic system by going into WOT maps early you can try if you wish but I don't think you will improve much. The other thing folks do is muck with the spring tension in the AFM and some have had some sucess with this (Including myself) but you can't get the fine tunning that is achievable by tunning the maps.

Just my experience in this area, I have spent many hours toying with AFR in my car. Including burning my own chips to fine tune my 3.2L

as a reminder per notes from Steve W.. the chips are programmed to run too rich at WOT and upper rpm ranges. This was done to keep temps. down in the cat at high performance levels. This is, as I understand it, one of the "easy" ways to get more power on these cars. As evidence, I put a wide band in my car and got the AF's to go down in the high 10's as rpm's rose at WOT. I think this wastes fuel and reduces power. I would have a Steve Wong chip.. but right now I'm too cheap and fixing other things on the car.

hcoles.

Running in the 10's seems a bit much. I understand building in some safety by making a chip run a little richer at the top to account for variations in cars, for some cooling effect, and as a margin of safety. However, I suspect that if you can get the car to breath better at the higher rpms this might lower your A/F's some.

It would seem that the fuel maps may not be using the AFM at this point as it has maxed out. Thus the computer is just saying, under WOT at 6000 rpms send X amount of fuel. If there is not enough air, it will run rich. If his is true, a freer flowing exhaust or freer flowing intake system could add real power and lower the A/F readings.

Got to run.

911st - yes makes sense... I read that the PWM signal goes to max. that this is full 100% on I don't know. I have a break out box on my DME right now and as I get time I'm reading various signals.... right now reading in the garage with a big scope.. later will use the handheld one from work.

Agree, running in the 10s at WOT is to rich. My car ran in the 12s with stock chip. But the general notion that the stock chips seem to run rich (in the 12s) by design has been the experience of others as well.

Also, I have done testing of the AFR at WOT in my car and I know that the AFM does have some influence over the AFR at WOT. I did a WOT run and recorded the AFR with my WideBand O2, it showed the AFR around 13.0 across the RPM range on my tuned chip. Then I opened the AFM and simply moved the pointer up a notch (not the spring) to richen and then pulled the same run. The AFR was 12.5 or so. This to me implies the AFM signal is still being used even at WOT, just not sure how.

If you want details on AFM functionality see this other thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/312961-3-2l-air-flow-meter-calibration-research-prodject.html

I did a lot of testing and recording on my AFM, compiled all the data into a nice document. See post #2 of that thread.

Sal, great document.

New thought, if hcoles car is running in the 10's with a stock chip somthing might be wrong.

It could be the flaper spring needs to be adjusted tighter.

If the flaper spring is to loose, the flaper would move to far to fast with changes in air flow. Thus, his cpu would think the motor is getting more air than it is.

The cpu then will take the higher voltage signel and referance it agenst the current rpm on the fuel table and use this given value to determin the duty cycle of the injector.

With the ability to log data he could readjust the flaper valve spring to a higher tension and make some runs untill it gets closer to what is correct.

Flaper style AFM's have good fidelity at low air flows and register changes in air flow easily. At higher air flows the flaper does not move much with changes in air flow.

The differance in the AFM voltages you registered on two different cars could be because one was breathing beter and puting out more power per rpm or it could be that the spring tension in the flapers was different enough that one moved through it's range of adjustment faster with changes in air flow.

I suspect that at around 5250 rpm this flap reaches an equallibrium where is would take a lot more air flow to move it even though there is still some range left.

There might even be a test in this in that if one were to measure the voltage at 6000 rpm where we know the valve reaches a state of equalibremun. Then it is high or low, it could mean the spring tension is wrong.

Also another reasion to have Steve do a custom map for a car that takes into account the sensitvity of the AFM.

Further, I suspect that at the top end, changes in rpm's are used more to change how much fuel is delivered than changes in AFM voltages. This is all done with in the table. If rpm's re 5500 to 5250 and the AFM voltage is 3.2, then open the injector 60% of the cycle. If rpm goes 5250 to 5500 and AFM stays the same, then the injector cycle could go to 63% of something.

As to the WOT map, I think we might be better served in thinking of is as the "Acceleration Map".

The good thing about the Acceleration Map is it is not modified by the O2 loop. If the flaper spring is out of adjustment, the O2 will modify the paramiters of the part throtle map to run the correct A/F as defined by the cpu.

If I understand correctly, the narrow band O2 does not work well at A/F settings that are good for max power. Thus part throtle power and response may be some type of a comprimize.

With the 3.2 Porsche the Acceleration map is trigered at any time the WOT switch is trigered. If works any time we want to accererate no mater if we are at 2500 rpm's or 5200 rpms so long as me mash the pettel to the floor.

If we could substitute a vacunm switch, we could improve the part throtle response and still keep an effecent A/F at cruse.

I did a little poking around the internet today and the idea of using a reduction in manifold vacunm pressure to triger acceleration maps is not new.

Jag used a vacunm switch on one of there euro models in the 80's to triger their acceleration map. Many other systems seem to use this along with throtle position sensors to triger acceleration tables.

We could concider doing the same.

Quick update on my TechEdge WideBandO2 setup.

I just got the new software version for this device, the software is called WinLog and I really like the new version. It lets you fully customize the dashboard on the laptop any way you want. Here's a picture of what the laptop dash looks like while it's monitoring the inputs:

http://forums.pelicanparts.com/uploa...1220559969.jpg

As you can see I'm monitoring and recording the following:
AirFuelRatio
RPMs
AirFlowMeter signal (0-5volts)
WOT switch (closed or opened)
Vehicle Speed in MPH - this is new ability in the software and I'm still working on the circuit to create the speed signal from the speedometer signal.

With the new adition of recording MPH I now can record 0-60 times, kind of neat.

All in all this is the best project / addition to the car and it all cost about $300.00

Sal

Thanks for all the great work and write up.

Pardon me if I ask a foolish question, this is out of my area of knowledge.

Is it possible to access all the DME input signals (to feed into a PC) by placing a jumper in between the DME input cable plug and the DME. Thus eliminating the work you did by accessing the DME internally.

I remember doing this back in the '60s to monitor system signals with an oscilloscope on flight simulators while the equipment was in operation.

Yes, sort of a break out box. But I did not have a spare DME chassis and harness to build one. But in Theory, if you had a male and female connector for the dme plug it could be done

Sal

Thanks for the reply.

If the plugs could be purchased and the signals fed to the PC with the software you're using it would enable all of us using the early Motronic to have an OBD style diagnostic system.

Maybe the guys at Tech Edge would add a few more lines to their software to monitor all the input signals.

An OBD system for Motronic would have several DIY and shops standing in line to purchase a complete turn-key setup.

Do you have any idea what the plugs are selling for?