wot stock fuel map?
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wot stock fuel map?
hey all, its been a while since i made it to the board. my internet has been rather flakey.
anyhow, got the sleeper legacy running, finally. here are the specs to date
short block and head work by paeco
11-1 cr ceramic coated pistons
torque cams
ported and polished heads
port matching
engine balanced and blueprinted
370cc jdm nissan injectors
255lph walbro fuel pump
super afc-II
autometer a/f and egt gagues
the car runs good and idles ok, but not real well. with the oversized injectors i have found that i have to run around 45% leaner with the safc. this works fine for normal throttle positions, but when i hit wot the gague always goes rich. im pretty sure that the computer reads wot, or anything above 80 % throttle and goes to a stock fuel map, and no longer relies on the maf or o2 sensor data.
is this understanding of how the ecu works under wot conditions correct? and if so can i employ a voltage clamp to trick the ecu into never thinking the throttle is more than 75% open?
also, i have been running 93 gas, but i would like to try to run 94 and see if it runs any better, is this a good idea?
once i am done with this project, i am hoping for around 200+ hp. (with exaust) is this a reasonable goal? right now i am running the stock exaust and i can only imagine how much aftermarket would help the porting and polishing show up.
thanks for listening to my rambles, and also thanks for any replies
josh mould
anyhow, got the sleeper legacy running, finally. here are the specs to date
short block and head work by paeco
11-1 cr ceramic coated pistons
torque cams
ported and polished heads
port matching
engine balanced and blueprinted
370cc jdm nissan injectors
255lph walbro fuel pump
super afc-II
autometer a/f and egt gagues
the car runs good and idles ok, but not real well. with the oversized injectors i have found that i have to run around 45% leaner with the safc. this works fine for normal throttle positions, but when i hit wot the gague always goes rich. im pretty sure that the computer reads wot, or anything above 80 % throttle and goes to a stock fuel map, and no longer relies on the maf or o2 sensor data.
is this understanding of how the ecu works under wot conditions correct? and if so can i employ a voltage clamp to trick the ecu into never thinking the throttle is more than 75% open?
also, i have been running 93 gas, but i would like to try to run 94 and see if it runs any better, is this a good idea?
once i am done with this project, i am hoping for around 200+ hp. (with exaust) is this a reasonable goal? right now i am running the stock exaust and i can only imagine how much aftermarket would help the porting and polishing show up.
thanks for listening to my rambles, and also thanks for any replies
josh mould
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no fpr yet
yeah, i havnt upgraded from the stock unit yet. i am not sure as to wether i will want an adjustable fpr or a rrfpr. i believe i am going to have to drop my fuel pressure to make up for the monster injectors... does this sound right? any recomendations on what/where to find what i need...
thanks,
josh mould
thanks,
josh mould
Sarcastic Jackass
Joined: Dec 2002
Posts: 622
From: Western Washington
Car Info: i drive a beater
Well, you COULD learn more about your AFC because that will help you our, or you could get a new FPR (adjustable, not rising rate!).
Is this an early legacy engine you've got in there, one of the turbos? If it is, those injectors aren't THAT much larger then stock.
Is this an early legacy engine you've got in there, one of the turbos? If it is, those injectors aren't THAT much larger then stock.
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safc-II
well, i think ive got a pretty good understanding of how the safc works, and its limitations as well. if there is something that i have missed, please let me know. i have already got the maf signal decreased to the maximum the safc will alow (-50%) and still have too much fuel. this is why i believe that i need an adjustable fpr so i can set it lower than the stock fuel system pressure.
btw, it is a 2.2 liter naturally aspirated engine
thanks,
josh mould
btw, it is a 2.2 liter naturally aspirated engine
thanks,
josh mould
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You keep refering to a gauge that you're tuning your a/f by. Are you relying on a standard a/f gauge hooked up to a narrowband O2? If so then you're lucky your engine is still in tact. Narrow band a/f sensors are useless in reading any a/f levels except at or near 14.7:1. They are simply inacurate at any other levels. So when your gauge says you're running rich, you might actually be running 13.5:1 or something which is actually too lean.
-- Ed
-- Ed
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also, in open loop (WOT) the ECU ignores the O2 sensor and relies only on the MAF reading to calculate fueling. The reason for this is stated above 
Thanks
-- Ed
Thanks
-- Ed
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Originally posted by vaus
You keep refering to a gauge that you're tuning your a/f by. Are you relying on a standard a/f gauge hooked up to a narrowband O2? If so then you're lucky your engine is still in tact. Narrow band a/f sensors are useless in reading any a/f levels except at or near 14.7:1. They are simply inacurate at any other levels. So when your gauge says you're running rich, you might actually be running 13.5:1 or something which is actually too lean.
-- Ed
You keep refering to a gauge that you're tuning your a/f by. Are you relying on a standard a/f gauge hooked up to a narrowband O2? If so then you're lucky your engine is still in tact. Narrow band a/f sensors are useless in reading any a/f levels except at or near 14.7:1. They are simply inacurate at any other levels. So when your gauge says you're running rich, you might actually be running 13.5:1 or something which is actually too lean.
-- Ed
I agree and disagree. You are correct the narrow bands are inaccurate, but to say they are useless is not true. I was actually able to tune my RS-T with only a narrow band O2. How you might ask, well it is simple, you find out how far off the narrow band can be, which is what I did on the dyno. Now that I know that, I take that into account while tuning. Usually the amount they are of stays consistent. So I then was able to choose the A/F ratio I wanted and make lots of power. Here is the narrow band tune I used on the RS-T a long time ago.
http://www.i-speed.us/tuning/
As you will note the A/F ratios did fluctuate but you can make pretty good power still with the narrow band. You just need to run a little safer then you usually would.
Cheers,
Bill @ I-Speed USA
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Bill,
yes, its possible to get a rough tune using a narrow-band while taking other precautions. But its deffinately a lot less safe than tuning with a wideband IMO.
The problem is that as the a/f aproaches richer numbers, the voltage/air fuel curve flattens out very quickly. This means that a slight variation in the recorded O2 sensor voltage corresponds to a fairly large a/f ratio change, making it difficult to predict the actual a/f ratio.
When I was playing around with this exact issue in my SC'd VR6, I found an interesting product. It was just a standard a/f gauge, modified to read a very narrow range of voltages from the O2 sensor in the range of .810-.900v and lit up the LED's apropriately. So basically it was only active during 12.5:1 - 11:1 a/f ratios (guestimate) and attempted to provide similar data to a wideband a/f sensor. I actually bought one and sold the car before I could try it out.
-- Ed
yes, its possible to get a rough tune using a narrow-band while taking other precautions. But its deffinately a lot less safe than tuning with a wideband IMO.
The problem is that as the a/f aproaches richer numbers, the voltage/air fuel curve flattens out very quickly. This means that a slight variation in the recorded O2 sensor voltage corresponds to a fairly large a/f ratio change, making it difficult to predict the actual a/f ratio.
When I was playing around with this exact issue in my SC'd VR6, I found an interesting product. It was just a standard a/f gauge, modified to read a very narrow range of voltages from the O2 sensor in the range of .810-.900v and lit up the LED's apropriately. So basically it was only active during 12.5:1 - 11:1 a/f ratios (guestimate) and attempted to provide similar data to a wideband a/f sensor. I actually bought one and sold the car before I could try it out.
-- Ed
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a/f gague
yes, i am relying on an a/f gague that is hooked up to the standard o2 sensor. i had realized this is inaccurate, but i didnt realize that there was a good chance for running lean...
knowing this, i am going to fatten up my fuel curve before i drive the car anymore. i am also going to talk to a shop with a wideband to have my car tuned better
sorry i havnt replied recently, ive been off line for a while\
thanks
fast legcy
knowing this, i am going to fatten up my fuel curve before i drive the car anymore. i am also going to talk to a shop with a wideband to have my car tuned better
sorry i havnt replied recently, ive been off line for a while\
thanks
fast legcy
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Ed,
Very good points, I guess I have my own techniques I use when relying on a narrow banf O2 sensor. Though they do require EGT's guage, A/F readings via a laptop for a better average of what the A/F ratio's are, what parts are installed on the car (cats etc), where the O2 sensor is located, where the EGT is located, fuel pressure, injector size.
I guess with all that other information I am able to daignose a pretty good map without the need of a wideband O2. Though don't get me wrong a wideband O2 is a great item to have for tuning, if not the best thing to have.
I am just saying a pretty decent tune can be done without the need of a wideband with all the other parts required though and a knowledge of what things should eb where and the values of what "things" should be. Also what to expect out of a cars performance based on engine design. A lot more can go into tuning then just a wideband O2.
I was able to get a pretty good map with the Link Plus running on anarrow band O2 sensor and make some good power.
Great conversation here.
Cheers,
Bill @ I-SpeedUSA
Very good points, I guess I have my own techniques I use when relying on a narrow banf O2 sensor. Though they do require EGT's guage, A/F readings via a laptop for a better average of what the A/F ratio's are, what parts are installed on the car (cats etc), where the O2 sensor is located, where the EGT is located, fuel pressure, injector size.
I guess with all that other information I am able to daignose a pretty good map without the need of a wideband O2. Though don't get me wrong a wideband O2 is a great item to have for tuning, if not the best thing to have.
I am just saying a pretty decent tune can be done without the need of a wideband with all the other parts required though and a knowledge of what things should eb where and the values of what "things" should be. Also what to expect out of a cars performance based on engine design. A lot more can go into tuning then just a wideband O2.
I was able to get a pretty good map with the Link Plus running on anarrow band O2 sensor and make some good power.
Great conversation here.
Cheers,
Bill @ I-SpeedUSA
iClub Silver Vendor
iTrader: (12)
Joined: Mar 2003
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From: 631 Railroad Ave. Fairfield, CA
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Bill,
Indeed, a skilled and knowledgeable tuner such as yourself can get a tune close w/o a wideband. I just want people to understand that its not as easy as looking at a regular narrow-band a/f gauge and tuning based just off that. That gets people in trouble. I think that point has been well established and your input is deffinately beneficial as well. Always enjoy a good tuning chat (especially when its about unorthodox methods ).
-- Ed
Indeed, a skilled and knowledgeable tuner such as yourself can get a tune close w/o a wideband. I just want people to understand that its not as easy as looking at a regular narrow-band a/f gauge and tuning based just off that. That gets people in trouble. I think that point has been well established and your input is deffinately beneficial as well. Always enjoy a good tuning chat (especially when its about unorthodox methods
).-- Ed
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Ed,
Indeed when it comes to a tuner that does not know all to much of what he/she is doing, then a wideband O2 is the best way to go. I would also suggest a EGT probe so that 4th and 5th gear puls in higher RPM's can be checked to make sure they don't run to hot.
Bill
Indeed when it comes to a tuner that does not know all to much of what he/she is doing, then a wideband O2 is the best way to go. I would also suggest a EGT probe so that 4th and 5th gear puls in higher RPM's can be checked to make sure they don't run to hot.
Bill