Jump to content
SAU Community

Recommended Posts

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

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 :)

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

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?

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.

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.

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


  • Similar Content

  • Latest Posts

    • Update 3: Hi all It's been a while. Quite a lot of things happened in the meantime, among other things the car is (almost) back together and ready to be started again. Things that I fixed or changed: Full turbo removal, fitting back the OEM turbo oil hardlines. Had to do quite a bit of research and parts shopping to get every last piece that I need and make it work with the GT2860 turbos, but it does work and is not hard to do. Proves that the previous owner(s) just did not want to. While I was there I set the preload for the wastegates to 0,9bar to hopefully make it easier for the tuner to hit the 370hp I need for the legal inspections that will follow later on. Boost can always go up if necessary. Fitted a AN10 line from the catch can to the intake hose to make the catchcan and hopefully the cam covers a slight vacuum to have less restrictive oil returns from the head and not have mud build up as harshly in the lines and catch can. Removed the entire front interior just shy of the dashboard itself to clean up some of the absolutely horrendous wiring, (hopefully) fix the bumpy tacho and put in LED bulbs while I was there. Also put in bulbs where there was none before, like the airbag one. I also used that chance to remove the LED rpm gauge on the steering column, which was also wired in absolute horror show fashion. Moved the 4in1 Prosport gauge from sitting in front of the OEM oil pressure gauge to the center console vents, I used a 3D printed vent piece to hold that gauge there. The HKB steering wheel boss was likely on incorrectly as I sometimes noticed the indicator reset being uneven for left vs. right. In the meantime also installed an airbag delete resistor, as one should. Installed Cube Speed premium short shifter. Feels pretty nice, hope it'll work great too when I actually get to drive. Also put on a fancy Dragon Ball shift knob, cause why not. My buddy was kind enough to weld the rust hole in the back, it was basically rusted through in the lowermost corner of the passenger side trunk area where the wheel arch, trunk panel and rear quarter all meet. Obviously there is still a lot of crustiness in various areas but as long as it's not rusted out I'll just treat and isolate the corrosion and pretend it's not there. Also had to put down a new ground wire for the rear subframe as the original one was BARELY there. Probably a bit controversial depending on who you ask about this... but I ended up just covering the crack in the side of the engine block, the one above the oil feed, with JB Weld. I used a generous amount and roughed up the whole area with a Dremel before, so I hope this will hold the coolant where it should be for the foreseeable future. Did a cam cover gasket job as the half moons were a bit leaky, and there too one could see the people who worked on this car before me were absolute tools. The same half moons were probably used like 3 times without even cleaning the old RTV off. Dremeled out the inside of the flange where the turbine housing mates onto the exhaust manifolds so the diameter matches, as the OEM exhaust manifolds are even narrower than the turbine housings as we all know. Even if this doesn't do much, I had them out anyways, so can't harm. Ideally one would port-match both the turbo and the manifold to the gasket size but I really didn't feel up to disassembling the turbine housings. Wrapped turbo outlet dumps in heat wrap band. Will do the frontpipe again as well as now the oil leak which promted me to tear apart half the engine in the first place is hopefully fixed. Fitted an ATI super damper to get rid of the worn old harmonic balancer. Surely one of the easiest and most worth to do mods. But torquing that ARP bolt to spec was a bitch without being able to lock the flywheel. Did some minor adjustments in the ECU tables to change some things I didn't like, like the launch control that was ALWAYS active. Treated rusty spots and surface corrosion on places I could get to and on many spots under the car, not pretty or ideal but good enough for now. Removed the N1 rear spats and the carbon surrounding for the tailpipe to put them back on with new adhesive as the old one was lifting in many spots, not pretty. Took out the passenger rear lamp housing... what do you know. Amateur work screwed me again here as they were glued in hard and removing it took a lot of force, so I broke one of the housing bolts off. And when removing the adhesive from the chassis the paint came right off too. Thankfully all the damaged area won't be visible later, but whoever did the very limited bodywork on this car needs to have their limbs chopped off piece by piece.   Quite a list if I do say so myself, but a lot of time was spent just discovering new shit that is wrong with the car and finding a solution or parts to fix it. My last problem that I now have the headache of dealing with is that the exhaust studs on the turbo outlets are M10x1.25 threaded, but the previous owner already put on regular M10 nuts so the threads are... weird. I only found this out the hard way. So now I will just try if I can in any way fit the front pipe regardless, if not I'll have to redo the studs with the turbos installed. Lesson learned for the future: Redo ALL studs you put your hands on, especially if they are old and the previous owners were inept maniacs. Thanks for reading if you did, will update when the engine runs again. Hope nothing breaks or leaks and I can do a test drive.
    • No those pads are DBA too  but they have colors too. I look at the and imo the green "street" are the best.
    • I’m not sure what happened I told them about sonic tunes free OTS tune and the next the I know .. I was booted..   To funny 
    • Yea - I mean I've seen my fuel pump which is decades old and uh, while I'm not saying this with real knowledge... but I sure get the ick at using anything in the fuel system that produced the state of that pump. Many years ago I went through multiple pumps (and strainers) before I dropped the tank to clean it out with extreme violence. I'm talking the car would do maybe 50km before coming to a halt, which resulted in me cleaning out the filter with some brake cleaner and going on my way. None of my stuff ever looked like what came out of your fuel tank. I don't think I'd be happy with it unless every single component was replaced (or at least checked/cleaned/confirmed to be clean here).
    • I'm not going to recommend an EBC pad. I don't like them. Just about anything else would suit me better. I've been using Intima pads for a while now.
×
×
  • Create New...