I am having problems with my car at low engine load (cruising) generally at low speeds. The car is surging, and I believe this is due to the wideband o2 sensors that are connected to the stock ECU. I believe the stock ECU is making AFR corrections on the fly, but because I am running 650 cc injectors, the corrections are alot larger than if I were running stock injectors. As a result, this is causing surging, because the air fuel ratio is going back and forth between 12.5:1 AFR, to 15.5:1 AFR. I have done all kinds of things to try and get rid of this issue but at this point I haven't figured out how to fix it.

At this point I am considering unplugging the stock widebands, and plugging the holes in the exhaust. I am hoping that this will cause the stock ECU from making AFR corrections. Then I wanted to try and use the eManage Ultimate to optimize the AFR for cruising.

Anyone have any comments on this plan? Will the stock ECU freak out if there are no o2 sensors plugged in? (besides CEL) Also, has anyone used the EU to perform O2 sensor feedback?

Thanks

Chris

 

i definately would not pull the stock 02 sensors out. the ecu might see it as a lean condition and richen it up as far as the ecu can, or just go into limp mode thinking there is a greater problem. i get the surging also, but i am thinking it may be because the flywheel/clutch combo is so light, the stock ecu may be compensating by moving the idle throttle motor excessively. i have not had any time to hit the dyno or tune more with it to see though.
you may have a point, if you are pulling all your injector signal from the airflow table. i did a combination of parameter inj. cut and airflow map cut to run my 650's but i am getting it too a little bit at very low speed on/off throttle traffic situations. i should be doing another clutch and making all copper gaskets for the exhaust and a custom 3" exhaust next week. then i will be hitting the dyno and will have alot of time to play with all the different ways of cutting the injector signal and see if i can figure something out. will let you know.
it has been raining here or below 35 for awhile now plus traffic, so i never get a chance to do any road tuning on the car, sucks!!

 

I am pulling 40% from the air flow voltage below 0psi and 45% above. At low low load it doesn't seem to make a difference if I pull 40% or 15%, there is so little air flow and fuel in that area that it doesn't really matter - or so it seems.

I would think that a computer would just simply not make any AFR corrections if it received no data. It's not like the sensor is plugged in, and just dangling in open air. I may be wrong however, the only way to see is to try it I guess. I just have to throw it on the lift to pull them out.

By the way, I just installed the ATS tripple with heavy flywheel and it's great. I ran the Tilton Semi street for a couple weeks, and also the Star 6 puck, and the ATS is far and away the best. The Star 6 puck was decent though.

Chris

 

i was thinking of trying a few different preload settings on the bov too, just to see if it made a difference.

 

EU isn't a paralell ECM so by unplugging the O2 widebands u'll screw it up far more... If you had UTEC or full EM you could probably get away with it..but w/ Emanage..idk.. Emanage only takes over sometimes not all the time. You can try moving the wideband further down?? or use the help method to trick it into thinking its in a lean environment?

 

EU isn't a paralell ECM so by unplugging the O2 widebands u'll screw it up far more... If you had UTEC or full EM you could probably get away with it..but w/ Emanage..idk.. Emanage only takes over sometimes not all the time.

 

just buy some "o2 simulators" you wire them in between the sensor and the conection, they tell the ecu your running stock AF, or you can try and put some spark plug fossils in the bungholes with the o2 sensors sticking out a little bit

 

There are 5 wires that power the widebands, and they all go in to the ECU. It's fairly complicated, so I guess what I am saying is that it doesn't appear that there is just one wire that you can put a resistor on. Anyways, that would screw my gas mileage (which is already dismal) and not necessarily fix the problem.

I don't understand what plump is saying about the eManage however. I don't see how that would make any difference at all? The issue is the stock ECU's O2 sensor feedback...



Chris

 

http://store.summitracing.com/?targe...1&autoview=sku

simple huh?
this is what they look like, youll need two

 

Chris,

When you tuned your EU for light throttle driving, did you set the fuel map to where the factory feedback was as close to zero as possible?

 

Mike, I understand what you're saying, but it's near impossible to do because the stock ECU is constantly altering the AFR. I have play around with the settings to try and get them close to the stock ECU so it doesn't have to make the corrections, but it's pretty rediculous trying to pull that off.

 

The stock ECU would be looking for certain afr at idle and under light cruise. If you take the time (and it does take a lot of time) to zero the trims out we've been able to get the 05's happy at idle and low cruise.

More difficult to tune, however, is between 3-5psi of boost where the MAF may be pulled back so far the car is still in open loop (and therefore looking for 14/15afr's). If this is the case try decreasing the MAF pullback at these load sites to get the car to go into open loop.

Hopefully this helps out..

 

Mike, thanks for the information (and encouragement!)

What kind of MAF % were you taking out around light cruise? I set it back to around 20% or so this morning, but the AFR is still jumping back and forth between 12.5-13 to 15-15.5 or so. Currently I am pulling 20% MAF, and adding 5% to fuel injectors w/ 650cc's.

I noticed the light boost thing also, which had me kind of worried. I don't have the oscilation issue as there is alot more fuel and air at that point so o2 corrections don't make as much of an effect. I have it putting in enough fuel so that it goes to around 13:1 AFR, but then I noticed it would pull fuel to around 14:1 AFR after about a second or two. This has always made me worry when on the highway in 6th gear and giving it a little gas.

I am pulling 45% from the MAF in boost to prevent from going in to 100% duty cycle mode. What kind of % are you pulling in 3-5 psi range to go in to open loop mode but prevent the 'crap my pants' mode?

I understand if this is proprietary info, but any help would be appreciated.

Thanks!

Chris

 

Hey Chris, how much fuel pressure are you running? Typical with properly functioning injectors, and the EU trimming them, the car should idle at stioch, and your 02 sensor should be causing any oscilation. Is it possible that one or both of your 02 sensors may be fouled?

I scaled injectors up to 650cc with the EU without any issues before (one car was an 05 model...the rest were pre 05). Is your ECU currently flash stock?

 

Chris,

Let's see if we can tackle this one step at a time. What are you Long Term and Short Term fuel trims in vacuum (light cruise).

I am going to guess both the long term and short term trims are taking out fuel with -20% MAF & 5 add'l injectors with your 650cc injectors.

If this is the case, the E-Manage settings would be delivering rich 12-af's and the car is trying to lean up the mixture (which is why it is varrying back and forth).

Do you have a return fuel system?

 

Yes I have a return fuel system. The MAF is pulled 20% in all vacuum at this point, and I am pulling 8 from the injectors at light throttle, and -10 at medium load, and I think somethine like -8 from 0 psi. At 0 psi, I am pulling 18.5% which seems to keep it in open loop. I have the car tuned pretty well at low boost levels, so it stays around 12.8:1 AFR, however I notice some small ocsillation still at light throttle.

Chris