Nitrosobmw

Hi guys, im new to this forum, i bought my 2000 c2 6spd about two months ago.

I just got my ecu tuned by evoms, which included among other things the turn off of the secondary air injection sistem, after i deleted it and ran for about 100miles i got a p0410 and p1411 bank 1 and 2 below limit,

I talked to evoms and Todd assured me that he turned it off,

Please help, thanks

Imo000

What's your question?

redridge

is the cel light on?

KrazyK

Uh, yeh its SAI codes. What did you expect?

redridge

well, the OP said his tuner shut off the SAI codes OFF. But his cel is ON. Just because he got SAI codes doesnt necessarily mean its the pump or a valve or a blocked line in the SAI system it could be cat related.... or a related emmsision can trigger a cel light... that was my point, it may not be an SAI after all.

Macster

By "deleted it" you are referring to the the SAI hardware?

In the meantime, while the SAI activation has been disabled the code path that is responsible for verifying proper function of SAI appears to be still active and finding a fault or in this case faults.

P0410 arises from apparently the pump failing to come on when commanded and P1411 from the absence of oxygen in the exhaust gases of both banks which should be there if the pump (SAI system) was working properly.

Not sure why you wanted the SAI disabled. It really doesn't cost anything since it runs (almost always) just at startup and helps warm up the converters which means the DME can switch to closed loop mode sooner and more cleanly fuel the engine. This results in less unburned fuel contamination of the engine oil which is a good thing.

As for the weight savings -- if you removed the SAI hardware -- negligible....

Nitrosobmw

I wanted to simplify the engine bay and i thought that by the tuner disabling it i could delete (remove) the hardware,

I dont have cats btw, and i told the tuner to disable the secondary o2s aswell.

My question is; why am i getting codes when the o2s and sai is deleted?

Macster

Well, my first thought is because they are not deleted. That is the code in the DME that works the SAI is still functioning and as part of its job to turn on the SAI another part is to ensure the SAI system is working by among other things checking for the presence of excess oxygen in the exhaust using the #1 O2 sensors.

My 2nd thought is after thinking a bit more and giving the tuner the benefit of the doubt is the SAI is not being activated but there is still code that attempts to verify the SAI is working and the fails it because it doesn't see the increase in oxygen in the exhaust gases that would be there were the SAI operating properly.

Now about the removal of the converters and #2 O2 sensors: I'm not sure how well the engine will fuel given that the DME is missing 2 very important inputs that it uses to fuel the engine.

Another way at looking at the DME is its job is to fuel the engine in such a way the converters are protected from damage -- this is because 1) they are expensive, and 2) the factory warranties these for 8 years, 70K miles or something like that.

After keeping the converters safe the next job is to fuel the engine in such a way its exhaust gases are most efficiently processed by the converters. The converters have a very narrow band of efficiency and the exhaust gases can't deviate too much from the ideal until the converter efficiency really falls off.

The #2 sensors are used to monitor the converter efficiency. You have removed those. What the DME now does in response to this I have no idea but I would be surprised if it resulted in a better running engine.

The last job is to meet the torque demands of the driver.

In most cases with a proper functioning engine and sensors and converters this is not a problem. We all know how well these engines run, how tractable they are and yet how well they run at higher rpms. We know how clean they run, and for sometimes hundreds of thousands of miles. (My 02 Boxster still passes CA emissions tests every 2 years and the last one was with over 250K miles on the original engine and converters. I've replaced the sensors at least once.)

But an interesting feature is that in the event of an exceptional torque demand by the driver the DME is free to ignore emissions and for a while ignore the #2 sensors and fuel the engine with a richer more power producing mixture of air and fuel.

Ok but you've modified the engine, removed some sensors it uses for this.

So it could be the DME in seeking to get some kind of signals that it expects to get is adjusting the fueling and in doing so the engine is getting sub-optimum fueling?

The DME has considerable range of adjustment in this regard and it will use all of that. When everything is hooked up and working right it is the closed loop aspect that limits the adaptation that the DME will do.

Thus I can't help wonder if the engine is any better off than it would have been had you left the hardware you removed in placed, hooked up and functioning properly.

Imo000

As far as I know the secondary (downstream) O2s only monitor the efficiency of the converters and has no input on engine fueling. That engine control is done by the primary (upstream) O2s. The engine needs clean exhaust gas readings to know what is going on and that's why the upstream O2s exist.

Nitrosobmw

Thanks for the replies, when i bought the car 2 months ago it didnt have any cats and the "secondary" o2s had the extenders installed so they wouldnt trigger cel,

i have read hear and other forums based on my search that other have turned off the sai with no further issues, (

KrazyK

Nitro, this sounds like a bad idea for a street car. Depending on where you are, It may have been illegal to have sold you the car with the cats removed. On something like this you are not getting any more power, your just messing up the engine systems. I hate the EPA and think they have gotten absurd with regs but stripping functioning emission equipment on a street car is just nonsense.

Macster

No. The #1 sensors are monitored by the DME to know the DME has control of the fueling. The DME varies the fueling to be a bit rich and then a bit lean over a period of say a second or so at idle to less than a second at higher engine speeds.

One can see this with a code reader/data viewer by monitoring the voltage levels of the #1 sensors. The voltage levels will go up and down as the exhaust gases contain more or less oxygen than outside air in sync with when the DME subtracts or adds fuel.

The #2 sensors are used to monitor the performance of the converters but if the readings indicate unacceptable performance the DME will adjust fueling to try to bring the post O2 sensor voltage readings into an acceptable range. There is a limit of how far the DME can go. If it goes too far one or more error codes are logged and the CEL turned on.

(The DME does this adjustment at other times. For instance I observed it when the passenger side VarioCam solenoid/actuator failed on my Boxster. The short term fuel trims were quite strange as the DME varied fueling to try to get the #2 sensor readings it wanted. With the car in for repairs I mentioned this to the tech and he told me that in some cases this fueling adjustment can result in misfires though this didn't happen in my car's case.)

As I covered earlier the DME is there to ensure the engine is fueled in such a way the converters are best able to do what they are supposed to do. Convert noxious combustion chamber exhaust gases into less harmful gases before they are vented to the outside air.

It is a tip of the hat to the scientists/engineers that came up with this control/feed back system of oxygen sensors and 3-way converters to accomplish this and yet make this process transparent to the driver and to result in not only a tractable, clean running, fuel efficient engine, but an engine that puts out a goodly amount of power and does for reliably and for a long time.

Imo000

Any fuel adjustments done because of the secondary O2 is done for on board diagnostic and nothing more. It part of the routine to figure out what part of the system is or has failed. That's why the short term trims are adjusted. Your understanding of how an OBDII system works is flawed.

Macster

Funny but I was thinking the same thing about your understanding of how the OBDII system works as being flawed.

KrazyK

Imre and Mac,

If he removed the SAI wouldnt he have to have a program to erase the SAI codes each time the engine is started or the codes will just keep coming back? I still dont get what hes trying to do. The SAI does no harm or cost HP so what gives?