Author Topic: Data logging & understanding the stock ecu. Evolution of the TBI Monster to Mpi  (Read 41516 times)

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  • TBI Guy
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I have been data logging the stock Ecu for a while now, what do you want to know?

My logs show that Unbaffled ahp's cause erratic airflow signals using the a mitsu mas. This effect looks to be a major factor behind "fuel cut symptoms" when using the bigger bolt on turbos. And makes it hard to dial in the afr with an afc. The stock accordion pipe alone has a significant smoothing effect, but is some what restrictive.

So i am going to try this baffle with a shortened ahp.



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  • TBI Guy
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I am using innovatemotorsports Logworks 3. You can down load here.
http://www.innovatemotorsports.com/support.php

I have an LC1 wide band, x16 gauge and two SSI-4 logger boxes i picked up second hand on ebay for about $70 each. Good luck finding used ones. The lc1 is not required to use the ssi-4 input boxes.
Hks rpm converter . One can be made for less.
GM 3 bar map sensor.

Any wide band can be logged via a 0-5v input on the ssi-4. The x-16 gets it's signal on the serial data cable, so there is less chance of error compared to a 0-5v gauge.

Edit, i added more info on the data loggers on page 2 Oct 14-10 post

I shortened the ahp and put the baffle between the hard pipe and 4" x 3" coupler from the 2g mas.

Picture of the un baffled set up.

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The air flow hz is the line that looks like an earth quake in the first two pictures.

Stock Mas, Street pull probably 3rd gear @ 15-16 lbs  with ahp


1g Mas with ahp 1900 hz of air flow


Here is a picture of the 1g airflow signal when i put the stock accordion pipe back on and the baffle back in the air can.  Much stabler signal even at 1900 hz. I am starting to think there is a reason that baffle is in there.


2G Mas


"Fuel cut" On a 1G mas. It looks like the air flow went erratic and dropped out. Ecu cut duty cycle back to match the erroneous signal and afr when to lean to ignite.

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At the time i was using a hks fcon.

The Hks fcon has a smoothing effect on the injector pulse width ( maximum effect seems to require level 4 or higher.) I did not know that at the time the above logs were taken. So the effect of the chopply airflow on the duty cycle is less in some of those logs than it would be with out the fcon.
So does 100% duty cycle.  :lol: When i went to the bigger injectors it got a whole lot harder to tune.  :(

I know now the fcon was letting me run the 100% duty cycle with out load based fuel cut symptoms. Edited 10-12-10
The up down up down itself is not really a problem. It is when i get 2 or 3 downs in a row for no good reason and the ecu duty cycle tracks that, that it is a problem. In the logs the duty cycle dips lag behind the air flow dips a little

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Quote from: Shelby
were you able to log a stock mass with stock  air filter housing ,,it'd be interesting to see  the wave  pattern , i bet a stock set up would be a much smoother  line
I have not logged that combo of parts. The stock accordion pipe and stock baffle smooth the signal, but starves the turbo for air. I was hard pressed to get more than 18 psi at the track with both

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The mas i use is a 2g mas (609) from a second gen eclipse turbo or 3.5 montero. I have a translator here, but have not tried it yet. Zero tune drift with the weather with the 2g mas set up.  :wink:  Note the 2g runs 20-25% leaner so something to tune with is required.

Edit, 10-19-10 I did find i get some tune drift with this set up. From 65-95 degrees it will lean out about .3 afr The dsm guys say the 2g mas is better in this respect than a maft.

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The 2g mas is a proven upgrade on a 1g dsm. Requires about 20-25 % bigger injectors and or compensation with an afc. It seems the 2.6 is quite capable of exceeding the metering capabilities of the 1g with the bigger bolt on turbos.

I do not know to much about dsm's. It looks like the 2 gen went onto production 94-01-01 (95 model year) and 1st gen production ended a little later.

Looks to be part # MB183609 Search 2g mas or maf on ebay, used on some v6 models as well.

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A good picture of the change in duty cycle when the ecu switches from the primary to both injectors. (Stock size Mitsu injectors in these pictures)

The afr goes out of whack around the transition point if the size ratio is less than stock.With 2 secondaries the afr would jump up 1.5 to 2 after the transition to both injectors. I had my afc throttle points at 20% and 32%. The High throttle being my both injector tune and the low being my primary only tune. It worked to a point, but i still had to drive around the problem area.



A good screen shot of the secondary kicking in at low rpms in response to tps movement.


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Looking at the logs the secondary kicks in about 390 hz of air flow. The exception being if it is on in response to tps movement.

The secondary looks to shut down about 290 hz of air flow.

I am currently dialing in the tune on some new 850/1400 injectors. The size ratio is still off a tad, but they are working much better at the transition point from the primary to both injectors than the two secondaries were.

I purchased the injectors from Lower shores performance. Unmodified they are different lengths, he machined them so they could be used together with an extra seal on the 1400.



Well the baffle i made for the ahp seems to be working. Airflow signal is maybe not quite as smooth as with a unbaffled stock accordion hose, but much improved over just the ahp. I tried it horizontal and vertical. I think vertical is a little better for my 2g mas.

I picked up about 1.5 psi over the stock accordion hose.  :)  :)

I am getting the new injectors dialed in, and was hitting 22 psi and trapping  103 mph  at the track friday.


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Quote from: StarWolf
Wow this is interesting...

In fact it seems to me my bucking with my car started with my removing my baffle from my stock air can...before that i could boost much higher...now i can only boost about 15psi ...any higher i get a rich spike and jerk. I am also working on fixing up my distributor but obviously you have found some results. Im sure the Mitsubishi engineers didn't put that baffle in there for no reason...this could prove to be really nice. You could pick yourself up a stock air can just for the hell of it and do some testing  :P
I had the same thing happen when i went to a air intake hard pipe. It totally jacked the mas signal.

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This pic shows how injectors with a non stock size ratio afect the afr at the transition point. In this case i was running two secondaries.

 Secondary kicked in and than i backed off a little, but car stayed on both injectors. I was probably going up hill. 20% tps was my primary injector tune and 32% my both injector tune. You can see the afr rise as i backed of and than go back to normal when the ecu switched back to the primary injector.



A 13.65 @ 103 track run on my new 850/1400 injectors.  :D

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At light throttle near steady rpm the duty cycle of the primary goes from about 52% to 22% when the secondary kicks in. Ideally when we choose injectors we would want to know the flow rates at those duty cycles for the stock injectors and the after market ones to pick after market ones that give the smoother transition.

Stock injectors. I use 580 cc and 1000 cc for comparison.

580 + 73% =1003
850 + 67% = 1420 (my 1400 tested at 1420)

650 + 46% = 949  There is likely an imbalance here, but that is what you are stuck with if you have nothing to tune with.

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Quote from: StarWolf
Wow this is interesting...

In fact it seems to me my bucking with my car started with my removing my baffle from my stock air can...before that i could boost much higher...now i can only boost about 15psi ...any higher i get a rich spike and jerk. I am also working on fixing up my distributor but obviously you have found some results. I'm sure the Mitsubishi engineers didn't put that baffle in there for no reason...this could prove to be really nice. You could pick yourself up a stock air can just for the hell of it and do some testing  :P
There are two things at play here. One the signal is likely not as accurate. Two the turbo spools quicker with out the  baffle and the airflow signal rises quicker. The ecu throws fuel at the engine in response to the airflow and over does it. The  car goes too rich and misfires.

It was also suggested by the maft tech people that obstructions to the air flow around the filter can be a factor.

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It looks like the fuel map goes to about 2000 hz. That's about 20 psi with a bigger bolt on turbo. Not saying it was programmed to run right at that air flow, but just to throw plenty of fuel at the situation.

When  the ecu sees average air flow in that range the injectors are at 100 %.  I have also noticed at about 4800 rpm it seems the ecu adds extra fuel. Not sure if that applies at lower air flows.

The last time i had a stock mas on it did seem to run leaner under boost. Most of my older logs the hks fcon was influencing the duty cycle and afr. I would have to run the one g and stock mas with the fcon zeroed out to really see what the difference

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Another view of "fuel cut" using a 1g mas. This is actually mas over run. This crap blows motors.


For those who think there is no limit to stock injectors. Note the afr headed north. The more rpms the less time the injectors have to supply the needed fuel. The aborted run was at higher boost than the first 2. This car had a 274 cam, 17c turbo and everything kdm sells. Stock 80k bottom end.


Edit, bigger picture
Setting up a gauge in Logworks. The input box needs to be programmed with similar info.

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Quote from: funkyp
Just curious, in this Log it says 2G MAS @ 19psi. Care to share what other fuel and turbo mods where done? It has a very safe AFR.

That was the the first 2g track outing. 19c turbo stock Mitsu injectors. Tuned with Hks fcon gcc. I do not know what the fcon was set at. The gcc was full rich +16%.

I know now that was two rich, that was about .1 above misfiring.

That log is a good example of how smooth the afr was on that set up at when the injectors are at 100%  When i went to bigger injectors the choppy ness off the air flow and duty cycle became a issue again.