one way of improving car economy is by changing afr's at low rpms/loads.
I hv two questions:

1- to what extend can I lean it out??
2- can i lean it out at idle too?? any problems with that?? i heard the car goes to open loop when it's cold, so that it richens the car at idle. Is this true?? will this function be affected in case i will go to open loop and lean it out at low rpms/loads??


thx

 

You can do this by inducing an open loop condition at cruise (and likely idle as well). This can be achieved by modifying the open loop load or open loop throttle tables. Those tables determine the crossover point from closed loop to open loop.

I believe the general consensus is that you shouldn't run too much leaner than 16:1. 15.8:1 is about ideal. You will likely not see an increase in MPG if you don't run leaner than 15.3:1 or so since you'll be losing the benefit of the EGR system while running in open loop.

Yes, the car idles in open loop when warming up. I'm not sure what determines that crossover point or if there is an additional modifier to the AFR tables that richens the mix for the warm up procedure. Some have seen that timing is reduced while the engine warms up ... that might apply to fuel as well.

In theory, you could modify the open loop load table to make the car idle in open loop ... just lower the first value to something below ~25 load and that should force open loop at idle. You can then tune the fuel map as needed.

 

yeah that should be all the info i need, thx...
i guess also when u increase afrs the amout of unburned fuel going to exst will also be reduced so the effect of cancelling the egr system will decrease...

hv an off-topic question:

I've seen in some posts over here that standard injectors capacity is 560cc/min,
at which duty cylcle is this calculated???


PS: what happens if i go over 16:1???

thx

 

Not sure on the injectors ...

Over 16:1 can cause increased EGTs.

 

It's calculated at 100% duty cycle at usually 43.5psi of fuel pressure. PTE usually varies with the level of FP. Hence why their x80cc flow more like x50cc.

*info given from multiple personal encounters where 680/780cc's were flow tested to be ~650/750cc respectively.

 

I Am New To This Too & Would Like Some Imput

 

If you lean too much you will get P0300 misfire issues as well.

 

You will get the P0300 for sure, but either WAY rich or WAY lean drops EGT's. Its when its borderline and running near 0" of vaccum or boost that the EGT's will rise.

The safe practical (keyword there) max seems to be about 16.2 with the IX (I think the MIVEC will help keep torque up as it drops when lean) and Lucas has stated 15.6 or so on his VIII.

 

can someone post up a example fuel map for an IX?

 

This is approximate as WB and mods will affect where you need to be of course

 

Just keep in mind that egr at 14.7 consumes much less fuel than say, 15.7 w/o egr. Cruise throttle response is more snappy w/o egr too which is only due to the greater volume of air moving through the charge without it.

Also, it probably would be useless to use the WB to judge fuel consumption while gas is recirculating, however you may be able compare the differences in fuel consuption (IPW) at a given cruise in a tall gear, or by your wallet when cruising constantly in open loop

 

Ahhh thanks Mr. Evo, that may be the cause of my PO300 all the time, did not know that lean condition could cause a probable PO300..

 

C6, thats a very valid point but how can we tell if that is true? Other than the fact that I personally have seen an increase in economy (while others have not seen a change or worse) I cant quantify whether or not I am really burning less fuel.

I am not arguing, just wondering on how we can test and see if its 100% accurate. You think simply measuring IPW will tell the whole story?

 

of course, cruising in a tall gear at a given rpm and comaparing IPW will give u a good idea abt the diff in consumption...

another way would be to watch your mpg's...

i didn't go to open loop yet, but i'll post the results once i do...
if the value of 16.2 can be achieved safely, i believe it would be more economical even without the egr system

Another way of comparing the two methods would be to find a study over the net on how much fuel, on average, is recirculated. Keep in mind that an afr of 16.2 means 10% less fuel. I doubt that there is 10% of fuel going unburned in the exst, this without mentioning that not all unburned gazes will be recirculated...

 

I would think you could, if somehow you were able to look at an average IPW over say one tank of gas. That would be a ton of logging though.

If your fuel pressure system remains unmodified during the course of two tank fulls of gas, one tank for non-economy and one for economy, your IPW's should decrease on the average because they aren't firing as long as with a 15.7 afr than a 14.7 afr.

I bet it could be quantified by IPW, but that a ton of logging, everytime you drive the car, for as long as you drive it, for two entire gas tank fulls.