Jump to content
SAU Community

Engine Management - Afr Variances In Other Gears

paulr33

By paulr33,
in Engines & Forced Induction

 Share

Recommended Posts

paulr33 Grand Master

paulr33

Posted
Posted

Hi All,

Am posting this based on something cubes has discovered whilst reading some tuning material.

He found that some ecu's tend to have the AFRS (tuned in) vary based on what gear is used.

Ie: have a range of cells set to say 12.1 AFR and then when done and tuned in 4th its fine.

When a subsequent run is done in 3rd or 2nd the AFRS vary slightly and could be leaner, say 11.8

It is envisaged that the ecu is looking at the previous snapshot of sensors and deciding injection amounts but when this is happening in real time in low gears it happens a lot quicker and thus, the ECU typically lags. The outcome is that the AFRS to lend to sway a little as its always looking at the previous set of numbers instead of predictive load checking, ie: check thats its on WOT and predict the load and precalculate the injection coming up.

Ive had some thoughts regarding this and the only way I would agree with it would be to see a dyno plot of AFRS side by side with both gears and a show of the map tracer plots showing the same block of cells were hit. it sounds like to me its simply a case of some alternate cells are being hit in the lower gears, as load varies compared to 4th. The main source of comments was found on another forum here -> http://www.innovatemotorsports.com/forums/...read.php?t=4109

Has anyone else heard similar comments or seen similar results? I've never checked my AFRS in other gears.

Cubes deserves all the credit, im just posting it up for discussion

:P

Sydneykid Grand Master

Sydneykid

Posted
Posted

I have logs of a couple of runs from the R33GTST down the ¼ mile at WSID, they are posted up in the Teach Edge thread. I can’t see any real differences in A/F ratios between 2nd , 3rd or 4th gears. Keeping in mind that I do most of the high load/rpm tuning in 3rd gear on the road, 4th gear is simply too many kph.

:) cheers :)

paulr33 Grand Master

paulr33

Posted
  • Author
Posted

yeah sorry i worded it wrong. meant to say richer. im not sure what ecu it was, but we were thinking the powerfc had the same problem and was possibly lagged in the lower gears. i havent seen any evidence, more just a thought

StockyMcStock Proficient

StockyMcStock

Posted
Posted

theoretically if the ECU was a bit on the slow side, in the first couple of gears where the rate of change of RPM is higher it could be slow in calculating what injector pulse to run at the next predicted RPM/load point.

i would have expected this to have been predicted by the ECU manufacturer though, and the processor speed upped enough to discount it. maybe i'm wrong?

Cubes Grand Master

Cubes

Posted
Posted

I'd think the pfc is more than capable.. They really are an awesome no frills ecu powerful ecu.

Mad082, check out the link posted, more likely with maf, apparently. :P

Leaner conditions in 1st and 2nd are very common with many ECUs. I've seen it more pronounced on MAF based systems. an ECU calculates the next injector duty cycle on the previous engine cycle(s). When RPM is fast rising, it is behind. Some higher end aftermarked ECUs and some OEM ECUs try to compensate either by looking at the current gear or trying to predict from RPM rise rate. That's why tuning should be done in higher gears.
MR331307 Experienced

MR331307

Posted
Posted

Yeah i think it is a MAP sensor ECU.

I think the ECU he is talking about is a Microtech.They need to be tuned in MATRIX mode to be most Effective on street cars.They USUALLY run off a LOAD MAP which is tuned in vacumm and PSI.They dont tune in Different RPMS unless in matrix mode.So i think that might be a problem.If you tune in matrix mode you will get rid of the problem.But the ecu only has a 16 x16 graph from what i remember.

Another Problem you might have is if you tune a car with a map sensor that has Multiple throttle bodys or BIG cams with low vacuum you will find it will change AFRS in different gears as well. To fix this problem you need to tune in a TPS x MAP screen which is usually found in the Settings page.

this isnt a problem with the ECUS its a problem with Who set it up and tuned it.

If you have a AIR FLOW METER ECU it wont have this problem to what i remember,Only map Sensor cars but they need to be tuned and setup correct to fix it.

Thunderbolt Rising Star

Thunderbolt

Posted
Posted (edited)

Interesting topic. On a related note, it can also vary when in the same gear:

For example, when I first had my tune, it was showing a rich mixture as it comes onto boost (about 11.3) before settling to almost bang on 12. Took it elsewhere with the same tune, and this one showed the rich patch going to 11 before settling on about 11.7. Air intake temps were showing the same, the runs were both done in third, so the consistancy was there, just showing different results.

Edited by Thunderbolt

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      From there, it is really just test and assemble. Plug the adapter cables from the unit into the back of the screen, then the other side to the car harness. Don't forget all the other plugs too! Run the cables behind the unit and screw it back into place (4 screws) and you should now have 3 cables to run from the top screen to the android unit. I ran them along the DS of the other AV units in the gap between their backets and the console, and used some corrugated tubing on the sharp edges of the bracket so the wires were safe. Plug the centre console and lower screen in temporarily and turn the car to ACC, the AV should fire up as normal. Hold the back button for 3 sec and Android should appear on the top screen. You need to set the input to Aux for audio (more on that later). I put the unit under the AC duct in the centre console, with the wifi antenna on top of the AC duct near the shifter, the bluetooth antenna on the AC duct under the centre console The GPS unit on top of the DS to AC duct; they all seem to work OK there are are out of the way. Neat cable routing is a pain. For the drive recorder I mounted it near the rear view mirror and run the cable in the headlining, across the a pillar and then down the inside of the a pillar seal to the DS lower dash. From there it goes across and to one USB input for the unit. The second USB input is attached to the ECUtec OBD dongle and the 3rd goes to the USB bulkhead connected I added in the centre console. This is how the centre console looks "tidied" up Note I didn't install the provided speaker, didn't use the 2.5mm IPod in line or the piggyback loom for the Ipod or change any DIP switches; they seem to only be required if you need to use the Ipod input rather than the AUX input. That's it, install done, I'll follow up with a separate post on how the unit works, but in summary it retains all factory functions and inputs (so I still use my phone to the car for calls), reverse still works like factory etc.
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      Place the new daughterboard in the case and mount it using the 3 small black rivets provided, and reconnect the 3 factory ribbon cables to the new board Then, use the 3 piggyback cables from the daughterboard into the factory board on top (there are stand offs in the case to keep them apart. and remember to reconnect the antenna and rear cover fan wires. 1 screw to hold the motherboard in place. Before closing the case, make a hole in the sticker covering a hole in the case and run the cable for the android unit into the plug there. The video forgot this step, so did I, so will you probably. Then redo the 4 screws on back, 2 each top and bottom, 3 each side and put the 2 brackets back on.....all ready to go and not that tricky really.      
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      Onto the android unit. You need to remove the top screen because there is a daughterboard to put inside the case. Each side vent pops out from clips; start at the bottom and carefully remove upwards (use a trim remover tool to avoid breaking anything). Then the lower screen and controls come out, 4 screws, a couple of clips (including 3 flimsy ones at the top) and 3 plugs on the rear. Then the upper screen, 4 screws and a bunch of plugs and she is out. From there, remove the mounting brackets (2 screws each), 4 screws on the rear, 2 screws top and bottom and 3 screws holding in the small plates on each side. When you remove the back cover (tight fit), watch out for the power cable for the fan, I removed it so I could put the back aside. The mainboard is held in by 1 screw in the middle, 1 aerial at the top and 3 ribbon cables. If you've ever done any laptop stuff the ribbon cables are OK to work with, just pop up the retainer and they slide out. If you are not familiar just grab a 12 year old from an iphone factory, they will know how it works The case should now look like this:
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      Switching the console was tricky. First there were 6 screws to remove, and also the little adapter loom and its screws had to come out. Also don't forget to remove the 2 screws holding the central locking receiver. Then there are 4 clips on either side....these were very tight in this case and needed careful persuading with a long flat screw driver....some force required but not enough to break them...this was probably the fiddliest part of the whole job. In my case I needed both the wiring loom and the central locking receiver module to swap across to the new one. That was it for the console, so "assembly is the reverse of disassembly"
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      But first....while I was there, I also swapped across the centre console box for the other style where the AV inputs don't intrude into the (very limited !) space.  Part# was 96926-4GA0A, 284H3-4GA0B, 284H3-4GA0A. (I've already swapped the top 12v socket for a USB bulkhead in this pic, it fit the hole without modification:) Comparison of the 2: Basically to do the console you need to remove the DS and PS side console trim (they slide up and back, held in by clips only) Then remove the back half of the console top trim with the cupholders, pops up, all clips again but be careful at the front as it is pretty flimsy. Then slide the shifter boot down, remove the spring clip, loose it forever somewhere in the car the pull the shift knob off. Remove the tiny plastic piece on DS near "P" and use something thin and long (most screwdrivers won't fit) to push down the interlock and put the shifter down in D for space. There is one screw at the front, then the shifter surround and ashtray lift up. There are 3 or 4 plugs underneath and it is off. Next is the rear cover of the centre console; you need to open the console lid, pop off the trim covering the lid hinge and undo the 2rd screw from the driver's side (the rest all need to come out later so you can do them all now and remove the lid) Then the rear cover unclips (6 clips), start at the top with a trim tool pulling backwards. Once it is off there are 2 screws facing rearwards to remove (need a short phillips for these) and you are done with the rear of the console. There are 4 plugs at the A/V box to unclip Then there are 2 screws at the front of the console, and 2 clips (pull up and back) and the console will come out.
×
×
  • Create New...