target air fuel ratio

[7M-KDL]

so i dont know if this has been covered before or not but if it has i cannot find it. does anyone have a chart for target AFR's at a given rpm on our motors or is that one of those things that will be different for every vehicle. i know that the ACTUAL afrs will be different for every car but what is a good target to shoot for when tuning? i also know that it should be around 14.7 at idle but what about at 2K rpm, 3K, 4K, etc. i am just trying to get a basic tune so that i can break in my rebuilt motor but i need toknow what afrs to be looking for as well. thanks in advance.

Matt

 

[supradjza80]

so i dont know if this has been covered before or not but if it has i cannot find it. does anyone have a chart for target AFR's at a given rpm on our motors or is that one of those things that will be different for every vehicle. i know that the ACTUAL afrs will be different for every car but what is a good target to shoot for when tuning? i also know that it should be around 14.7 at idle but what about at 2K rpm, 3K, 4K, etc. i am just trying to get a basic tune so that i can break in my rebuilt motor but i need toknow what afrs to be looking for as well. thanks in advance.

Matt

Target AFR is going to depend on quite a lot of things. Target afr will always be 14.7 at idle, and cruise - constant speed, as well as acceleration up to a set point that the ECU deems it neccasary to no longer used closed loop control (o2 sensor feedback) and it begins to use the open loop control.

Open loop control is generally going to begin at throttle angles above 50% and engine speeds above ~2500 rpm (on my car at least). Target AFR's in open loop when fully stock appear to be from about 10.5:1-11:1. If I were tuning the car I would shoot for 11.5:1-12:1 afr during this time. But you will need to make absolutely sure that doing so is not causing detontation or pre-ignition with the factory ignition timing, or if you can adjust timing that you are not causing det or pre-ignition with your timing settings.

 

[7M-KDL]

i hav an afpr to make big adjustments and plan on using safc for small adjustments so that i can avoid that timing advance issue. so your saying that basicall everything above 2500rpm i should try to get 11:1? that seems simple, i thought that there were gradual increments to go through. is that not right? also have a question about setting afpr by VF values. in the manual it says run the engine at 2500rpm and check the voltage. is that what im supposed to do to tune or is that just to check that it is working? thanks


edit.i should probably tell you the mods as you said that was for a stock car. i have a complete rebuild with stock CT-26(rebuilt), +.020 pistons, mhg, 660injectors, lex afm, safc, afpr, innovate lc-1, bic ddp. that should be all the things relevant to answering my question

 

[isnms]

http://www.supramania.com/forums/showthread.php?p=159348&post159348

 

[oldsking]

Your mods will be very good for when you up the boost to say 14psi The same concept applies though for the A/F you want the 14.1 in the idle range and with those mods there might be some tweaking needed to get the 14.1.. Under boost, well, make some passes and have someone log for you (unless that LC1 has the data logging feature) and start from there.

 

[grimreaper]

Hook the VF output from the ecu into the blue wire on the safc (google "safc blue wire mod", used by dsms to watch the o2 sensor voltage). You can then look at it on the safc and tune vf's. With the safc being tps/rpm based your not going to be able to tune vf's very well through out the rpm band. How ever at idle you will. This will help if you have to drop fuel pressure to avoid pulling to much fuel on the safc. Other wise dont bother with trying to tune cruise or closed loop operation. The ecu will simply over ride your correcetions.
I tune 11.2-11.5 afr and leave it at that.

 

[7M-KDL]

the lc-1 can datalog but it doesnt go by rpms bc i dont have the converter. it logs by time intervals. i had a friend help me tune it but now i have another issue. i think my fuel pressure might be too low. i lowered it to try to keep from pulling too much fuel with the safc but i think it is set at 15-20psi, which seemed to run fine when we were tuning. i do not have the car now, it is at my parents house but i will check my fp to make sure when i get home this weekend. also, the afpr doesnt hold pressure after the car is shut off and i am told that it should for a short period of time. another also, i still have the stock fuel dampener, should i remove that? could it be causing my fp gauge to read that it is set at 20 but actually be higher if i take the dampener off? thanks in advance. i will keep everyone posted

 

[oldsking]

Yeah man kill the dampener and the j-tube (if you have it) and run the fuel straight into the rail and through your afpr. Here's a trick to not have to worry about the closed loop... Unplug your stock o2 so the ECU doesn't need to correct what you are tuning and do away with what you have set with your SAFC.

 

[7M-KDL]

no j-tube, just the dampener at the rear of the rail. i didnt do any lo throttle/idle tuning with the safc. so i figured id leave the stock o2 so the tccs would take care of all the low stuff? also, i have heard about the "force into open loop" trick but ive also heard that that is not really a good thing to do.

 

[7M-KDL]

ok, got home and checked it. yeh, my base fp without the vacuum is 28-30 psi. with vacuum hooked up it drops to about 20psi at idle. is this right? still going to get the dampener bypass when i get some money, prolly a week or two.

 

[mkIIIman089]

You need to work out how to work with the stock ECU instead of fighting it. Many (most) people on here seem hell bent on fighting it; almost always with inconsistent, engine destroying results.

 

[grimreaper]

Hook the VF output from the ecu into the blue wire on the safc (google "safc blue wire mod", used by dsms to watch the o2 sensor voltage). You can then look at it on the safc and tune vf's. With the safc being tps/rpm based your not going to be able to tune vf's very well through out the rpm band. How ever at idle you will. This will help if you have to drop fuel pressure to avoid pulling to much fuel on the safc. Other wise dont bother with trying to tune cruise or closed loop operation. The ecu will simply over ride your correcetions.
I tune 11.2-11.5 afr and leave it at that.

Yeah man kill the dampener and the j-tube (if you have it) and run the fuel straight into the rail and through your afpr. Here's a trick to not have to worry about the closed loop... Unplug your stock o2 so the ECU doesn't need to correct what you are tuning and do away with what you have set with your SAFC.

How do expect to tune the other 98% of the fuel map? Have you tried this with a safc? Read below

no j-tube, just the dampener at the rear of the rail. i didnt do any lo throttle/idle tuning with the safc. so i figured id leave the stock o2 so the tccs would take care of all the low stuff? also, i have heard about the "force into open loop" trick but ive also heard that that is not really a good thing to do.

Its not that simple tuning closed loop with a safc, for one you have nothing to tune based on load. You can easily hit every load point from idle to boost in almost every tps range. What happens when you need more fuel at 80-100kpa then at 50 kpa? So you tune a perfect 14.7 at 2500rpms at 1.5v tps. Lets say thats at 50 kpa or some where in the 2-300hz range. What happens when you hit the same rpm and same tps value but now your accelerating at 90kpa or 5-600hz? You cant re tune for the higher load with out throwing out the lower loads tune.

 

[7M-KDL]

grim, im a little confused by your last post. there are a lot of quotes and bolded sentences. which ones are you agreeing with or disagreeing with? are you saying that allowing the tccs to deal with the low throttle is not a good idea? it seemed like the other threads i read about safc tuning said not to tune low throttle because the ecu will just fight it so you should use your set points to tune the higher throttle/rpm points.
im pretty sure that what i did/am doing is pretty much what you described in a previous post.(your first quote in last post) i just used a multimeter to check vf instead of watching on the safc with blue wire. i used the afpr to get the vf to 2.5 at idle and to keep from pulling more than 10% with the safc. then i used the safc to tune the open loop stuff(after 69% throttle?) i think my afr's are around 12-13 at wot around 5k rpms. i did pulls in 2nd,3rd,and 4th gear from about 2500-5000rpm and a friend watched my afrs and changed safc setting for me. since i am not running higher boost yet im told that i dont need 11s. i didnt have an signs or detonation or knock at these levels. my car was at operating temp and everything and i did multiple pulls and the knock sensors never registered anything and i never got any other sort of codes. obviously when i turn the boost up i will re-tune but do you think those afrs are ok for stock boost?

 

[grimreaper]

edited first post.
You still have timing to worry about, lower boost = more timing with a stock ecu. Then consider your running pump (assuming) and the chance of inconstancy with that. low 11's to high 10's afr regardless of boost but its your car.

 

[7M-KDL]

that is what i originally thought. i was thinking like 11-11.7 but then a friend said i shouldnt need it that low. can you explain the low boost/timing thing? thanks