quick question - is it normal ?

mops · Post by **mops** » Thu Feb 02, 2006 2:19 am

Hello.

Have a look on the screenshot attached, just after the vertical line.

is it normal, that on throttle relase (even small decerase), afr's go rich for a moment ?

at higher rpm's, on moderate throttle movement's, my afr's basically go rich off the scale.... for a split of a second. Decel enleanment is active only below 1500rpm's I believe.

on this particular pic, the afr's go to 10.5 on the very slight throttle relase...

aswell on the enrich side... accell enrich provides extra fuel only for 0.2 seconds (can do more of course), after which engine goes lean for a moment.

Just wondering whether it is normal/desires/ego reading error/should i be concerned, etc. ?
ms specs in sig.

bimmersquirt · Post by **bimmersquirt** » Thu Feb 02, 2006 10:19 am

Mine shows 10.2 AFR after throttle release too M8, I had associated it wit the dump valve I'm using but thinking about it, with no fuel cut yet enabled it has to go rich.

BTW almost the same ride !, not seen you on the Zone for ages either.

naprotejay · Post by **naprotejay** » Thu Feb 02, 2006 5:43 pm

hmmm not sure if this will help answer, but..... before I installed MSII, I had installed an LC-1/XD-1 . it was interesting to watch the a/f as the stock ecu made adjustments.... one of the things that I noticed is that when letting off the throttle, the a/f's would momentarily go rich, and then off the scale lean. on the other hand, when applying throttle, it would go lean, before it would richen up......

so, I think what you're seeing is 'normal'?? ;)

mops · Post by **mops** » Thu Feb 02, 2006 6:53 pm

naprotejay wrote:hmmm not sure if this will help answer, but..... before I installed MSII, I had installed an LC-1/XD-1 . it was interesting to watch the a/f as the stock ecu made adjustments.... one of the things that I noticed is that when letting off the throttle, the a/f's would momentarily go rich, and then off the scale lean. on the other hand, when applying throttle, it would go lean, before it would richen up......

so, I think what you're seeing is 'normal'?? ;)

i'll review my logs.

I aswell have some logs of etock ecu with MS2 logging map, rpm and afr via LC-1. I'll have a look and reposrt whats going on.

the other thing I'm thinking it might be just error in sensor readount or something similar... many sudden inrush of gases casues sensor to show rich or lean.... or something...

keithmac · Post by **keithmac** » Fri Feb 03, 2006 3:07 pm

Way too much fuel can show up as lean on a wideband in some circumstances, may be an issue?

Post by **grippo** » Sun Feb 05, 2006 10:01 am

OEM and university research shows that when fuel is injected into the port some of it goes onto the walls and some of the fuel on the walls vaporizes into the air stream, so there is a balance. In transient operation (accel or decel for example) this balance is upset temprorarily. The rate of fuel evaporation into the air becomes slower at high MAP, so when you accelerate, the rate of fuel coming off the walls is less than the amount going in, so until there is an enrichment shot, the afr goes lean. But even if there was no enrichment shot it would eventually straighten out (provided the motor doesn't die and your ve is properly tuned for the changed map at the higher throttle opening.) Think of a glass with water going in and out at the same rate. Then all of a sudden one of the rates changes quickly to a new value. It takes time for the other to catch up so the glass is temporarily either half empty or overflowing, but if the rates are proper the glass will again go into equilibrium. We have modeled this in version 2.6 and initial testing with a simulation looks good. What you do is change the fuel whenever map or rpm change in accordance with a user input table which can be tuned. This table is used in a very simple algorithm that provides a smooth fuel change as soon as it sees a change in rpm or map and gradually tapers off the fuel change automatically without requiring a lot of coding. For example it easily takes care of the fact that you need less enrichment for accel that starts at hi rpm than you do starting at low rpm.

naprotejay · Post by **naprotejay** » Tue Feb 07, 2006 2:33 am

grippo wrote:But even if there was no enrichment shot it would eventually straighten out (provided the motor doesn't die and your ve is properly tuned for the changed map at the higher throttle opening.)

that's exactly what I noticed with the Denso stock ecu in my mazda (AFAIK it does not do accel enrichments....) - when applying throttle, it would go lean, and usually would take ~2, maybe 3? seconds to richen up and 'stabilize'.....

grippo wrote:We have modeled this in version 2.6 and initial testing with a simulation looks good. What you do is change the fuel whenever map or rpm change in accordance with a user input table which can be tuned. This table is used in a very simple algorithm that provides a smooth fuel change as soon as it sees a change in rpm or map and gradually tapers off the fuel change automatically without requiring a lot of coding. For example it easily takes care of the fact that you need less enrichment for accel that starts at hi rpm than you do starting at low rpm.

sounds

!!

mops · Post by **mops** » Sun Feb 19, 2006 11:09 am

Thanks for input.

i have been datalogging my stock bosch motronic ecu, and all tho it does the same thing, it's much less pronounced...