Air Fuel Ratio after big exhaust installation
08-12-09, 03:04 PM
#1
Air Fuel Ratio after big exhaust installation
hi everyone
my normal AF ratio is about 14.1->14.5 but after I have Apexi N1 ExTi installed, the AF ration jumps crazy from 13.x -> 17.x
any thoughts on this? I haven't done the intake yet.
I'm trying to understand if I have any problems before moving on as it is my first mod :-D
thx
my normal AF ratio is about 14.1->14.5 but after I have Apexi N1 ExTi installed, the AF ration jumps crazy from 13.x -> 17.x
any thoughts on this? I haven't done the intake yet.
I'm trying to understand if I have any problems before moving on as it is my first mod :-D
thx
08-13-09, 04:15 PM
#14
This is why I asked if you had a wideband.... The stock narrowband is useless and gives you NO USEABLE information. You need to purchase a good wideband. I recommend the Innovate or FJO units. They have a good linearity to the low AFR's that we have to run on the rotary. AEM I have heard good and bad both, so I would go with one of the other units.
If all that is done is a downpipe and catback and you are only running 10psi of boost I would be willing to bet that you are ok on afr's. But if you have access to a shop with a dyno take it down there and have then confirm the afr's.
I do not mean to sound rude but try and read through the faq's as well as just general automotive modification notes you can find. It will give you a better understanding of how things work and what effects them. And don't say you know how it all works b/c obviously that is not true. Be as humble as possible and always try and learn more. If you hear something, research it to confirm/disprove it and then apply the new knowledge.
If all that is done is a downpipe and catback and you are only running 10psi of boost I would be willing to bet that you are ok on afr's. But if you have access to a shop with a dyno take it down there and have then confirm the afr's.
I do not mean to sound rude but try and read through the faq's as well as just general automotive modification notes you can find. It will give you a better understanding of how things work and what effects them. And don't say you know how it all works b/c obviously that is not true. Be as humble as possible and always try and learn more. If you hear something, research it to confirm/disprove it and then apply the new knowledge.
08-13-09, 04:27 PM
#15
This is why I asked if you had a wideband.... The stock narrowband is useless and gives you NO USEABLE information. You need to purchase a good wideband. I recommend the Innovate or FJO units. They have a good linearity to the low AFR's that we have to run on the rotary. AEM I have heard good and bad both, so I would go with one of the other units.
If all that is done is a downpipe and catback and you are only running 10psi of boost I would be willing to bet that you are ok on afr's. But if you have access to a shop with a dyno take it down there and have then confirm the afr's.
I do not mean to sound rude but try and read through the faq's as well as just general automotive modification notes you can find. It will give you a better understanding of how things work and what effects them. And don't say you know how it all works b/c obviously that is not true. Be as humble as possible and always try and learn more. If you hear something, research it to confirm/disprove it and then apply the new knowledge.
If all that is done is a downpipe and catback and you are only running 10psi of boost I would be willing to bet that you are ok on afr's. But if you have access to a shop with a dyno take it down there and have then confirm the afr's.
I do not mean to sound rude but try and read through the faq's as well as just general automotive modification notes you can find. It will give you a better understanding of how things work and what effects them. And don't say you know how it all works b/c obviously that is not true. Be as humble as possible and always try and learn more. If you hear something, research it to confirm/disprove it and then apply the new knowledge.
yes I read lots of faq and search before posting this. but anyway thanks a lot it's very helpful.
08-13-09, 06:44 PM
#16
If you read the fact then you would know you should be finding ways to control the boost with your mods. The factory tune is really too rich but Mazda tuned it this way to allow for some protection. There is enough fuel for all your common bolt ons ONLY if you keep the boost at 10psi. That's been proven in the past. You need to control your boost to be safe when modding with the stock ecu. Also the more you mod, the less protection you will have especially if you run 89 or 87 octane.
08-13-09, 08:38 PM
#18
No worries. There is an INSANE amount of good information on this site. The wideband is really a must have addition to your rotary. I would not even think of driving my car without one installed. Like I said, on 10psi and just your mods your AFR should be just fine as long as you are running premuim fuel. But it is a good idea to get that wideband on there and keep an eye on it. For now, definately hold off on the intake.
09-01-09, 03:27 PM
#20
ok. Finally I got the wideband installed. here what it looks like
most of the time it's between 14 and 15. when boost it's 12.5->13 but if I release the pedal it's 18.
what creep me out is one in a while it jump to 18 during normal cruising and then back down to 14.5 or so.
any thoughts?
I'm thinking about upgrade the PowerFC and secondary fuel injector then air intake and a SMIC.
thx
most of the time it's between 14 and 15. when boost it's 12.5->13 but if I release the pedal it's 18.
what creep me out is one in a while it jump to 18 during normal cruising and then back down to 14.5 or so.
any thoughts?
I'm thinking about upgrade the PowerFC and secondary fuel injector then air intake and a SMIC.
thx
09-01-09, 03:47 PM
#21
When you release the throttle pedal the injectors are cut off and AFR numbers get very high because it's "all" air. 14.5 cruising/no boost is fine, some people lean it out more for better mileage. 12.5-13 under boost is on the high side, but it's what you get with the stock fuel pump and map.
You better add some fuel. Incremental steps you may want to take
(1.) wire the fuel pump directly,
(2.) replace the stock fuel pump with a Supra pump,
(3.) get a PFC and increase injector duty.
With unported motor and stock twin turbos, you should be fine like that and there would be no need to upgrade secondary injectors unless you run at full boost for extended time - because the injector duty is very high under those conditions. (1.), (2.) and (3.) is what I have, I run 13 psi target with stock injectors and my AFR is 11
- Sandro
You better add some fuel. Incremental steps you may want to take
(1.) wire the fuel pump directly,
(2.) replace the stock fuel pump with a Supra pump,
(3.) get a PFC and increase injector duty.
With unported motor and stock twin turbos, you should be fine like that and there would be no need to upgrade secondary injectors unless you run at full boost for extended time - because the injector duty is very high under those conditions. (1.), (2.) and (3.) is what I have, I run 13 psi target with stock injectors and my AFR is 11
- Sandro
09-01-09, 05:14 PM
#23
A couple of other things to look at are:
Fuel pressure rise rate - if the pressure regulator is functioning properly the pressure should rise proportionally with the boost. Otherwise a lean condition much like you are seeing could occur.
Injector duty cycle - need to look at the duty cycle with a scope and look at all of the secondaries for sure. Old injectors seem to varnish up and not deliver the same mass flow and spray pattern as when new. The ECM will compensate with a higher duty cycle up to a limit then a lean condition will ensue.
Fuel filter - if flow limited during high demand obviously a lean condition will happen.
Fuel pressure rise rate - if the pressure regulator is functioning properly the pressure should rise proportionally with the boost. Otherwise a lean condition much like you are seeing could occur.
Injector duty cycle - need to look at the duty cycle with a scope and look at all of the secondaries for sure. Old injectors seem to varnish up and not deliver the same mass flow and spray pattern as when new. The ECM will compensate with a higher duty cycle up to a limit then a lean condition will ensue.
Fuel filter - if flow limited during high demand obviously a lean condition will happen.
