mefi tuning question for experts
08-02-2008, 05:07 AM
#1
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mefi tuning question for experts
I was out this morning doing some fine tuning on my boat with my new mefiburn software and I am starting to get a basic understanding of how it works. This was the second time out with it,last week I went out and ran it from idle to partial boost and slightly tweaked the fuel tables. Tyler Crockett did a pretty good job on the dyno last year doing the intial programming,we found a few areas where boat was running 10.8-11 afr at light cruising and leaned them out to 13-1,we were pretty happy with ourselves,I will say there is no way someone should try to do a complete tune to a blower motor without initially having their motor tuned by a expert on the dyno,mainly under boost because you will chance damaging your motor plus it would be awfully difficult to make enough high speed passes under boost while monitering everything and making adjustments. The next day we took the boat out and ran it with the air fuel meter on it to moniter the corrected afr's. To my surprise the afr's we had tuned in at part throttle cruising suddenly were in the high 13's close to 14-1. We went back out this morning and did a re-tune and I found that while motor may be at 12.8-1 to 13-1 let say at 3200 cruising trimmed up with a light load if you leave the drive dug in deep and tabs down deep the map reading goes in the high 80's vs the low 80's and runs off the 90 map fuel trim ve the 80 map trim at a higher percentage throttle opening. So we ran boat AGAIN thru all the rpm ranges both ways and adjusted the fuel accordingly with good results.
My questions for the experts is this-I thought with a 2 bar map sensor and mefi 3 or 4(I'm running a 4a) that there were fuel tables that went all the way to 180 map,not just multiplier tables above 100. If there is I couldn't find them. I have always avoided cruising at 1-4 psi of boost because my boost referencing fuel regulator doesn't really bring fuel pressure up much from base until your pretty far into the boost. I confirmed this today by taking boat to only 5000-5200 at part throttle,it was showing about 1-2 psi boost on gauge and scanner pro was showing map readings of around 100-110. Fuel pressure was bumped up to about 50 psi from base of 40 psi,my afr's climbed to the high 13's which I thinkwould melt the motor down eventually. I bumped up the 5000-5200 rpm/100map fuel trim by about .3 and increased the fuel multiplier table at 105 and 110 by about .05,on the next identical run my afr's were down in the mid 12's.
Do the multiplier tables above 100 multiply the fuel trim at 100 map?
Lets say you were far into the boost and you were at 140 map,would it still be multiplying on the last fuel table at the same rpm at 100 map?
My cam is fairly large,what other adjustments can I make at IDLE and just off idle other then timing and the fuel trim bpw at the map setting it happens to be running at to get better throttle response and idle quality? Thanks for any info,Smitty
My questions for the experts is this-I thought with a 2 bar map sensor and mefi 3 or 4(I'm running a 4a) that there were fuel tables that went all the way to 180 map,not just multiplier tables above 100. If there is I couldn't find them. I have always avoided cruising at 1-4 psi of boost because my boost referencing fuel regulator doesn't really bring fuel pressure up much from base until your pretty far into the boost. I confirmed this today by taking boat to only 5000-5200 at part throttle,it was showing about 1-2 psi boost on gauge and scanner pro was showing map readings of around 100-110. Fuel pressure was bumped up to about 50 psi from base of 40 psi,my afr's climbed to the high 13's which I thinkwould melt the motor down eventually. I bumped up the 5000-5200 rpm/100map fuel trim by about .3 and increased the fuel multiplier table at 105 and 110 by about .05,on the next identical run my afr's were down in the mid 12's.
Do the multiplier tables above 100 multiply the fuel trim at 100 map?
Lets say you were far into the boost and you were at 140 map,would it still be multiplying on the last fuel table at the same rpm at 100 map?
My cam is fairly large,what other adjustments can I make at IDLE and just off idle other then timing and the fuel trim bpw at the map setting it happens to be running at to get better throttle response and idle quality? Thanks for any info,Smitty
08-02-2008, 07:17 AM
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I have a fast system. I do not know about the Mefi system. When I make changes I look at the other cells close to the one that is in effect at the time and check where they are at. I have found when I make a change I make a small change, then go back and check later.
The good part about with efi is you can change the map to compensate for when the fuel regulator is not pumping up the pressure.
You can also make a number of changes to your IAC. With the fast system you can change gain controls. I have pasted what fast has in their help file.
The IAC "P" gain value can be set from 0 to 255. Raising this value will cause the IAC motor to open or close further in an attempt to correct the idle speed. The IAC "D" gain value can also be set from 0 to 255. Raising this value will cause the IAC motor to open or close faster in an attempt to correct the idle speed. The default values of 32 for the P gain and 4 for the D gain are generally close to correct for most applications.
An excellent way to better understand these settings is to liken them to a sensitivity control on a cruise control circuit. If the circuit was set for maximum sensitivity (gain values both set to 255) the accelerator pedal would go to the floor as soon as you dropped below the target speed, and the pedal would drop to an idle as soon as you were going too fast. If the circuit was set for minimum sensitivity (gain values set to 0) the accelerator pedal would hardly move if you were going too fast or too slow, and you would almost never be traveling at the desired speed. This same concept applies to how your IAC motor will regulate idle speed.
The "Max. TPS for Idle" field is used to set the threshold where the ECU no longer considers the engine to be idling. It is recommended to observe the TPS reading at an idle and setting this field to that number plus one. In other words, if your TPS reads 10% at an idle, set this value to 11. When the TPS percentage exceeds the value specified in this field, the IAC motor will be "locked" into the position specified in the throttle follower graph, and the Timing Trim graph will not be used.
The good part about with efi is you can change the map to compensate for when the fuel regulator is not pumping up the pressure.
You can also make a number of changes to your IAC. With the fast system you can change gain controls. I have pasted what fast has in their help file.
The IAC "P" gain value can be set from 0 to 255. Raising this value will cause the IAC motor to open or close further in an attempt to correct the idle speed. The IAC "D" gain value can also be set from 0 to 255. Raising this value will cause the IAC motor to open or close faster in an attempt to correct the idle speed. The default values of 32 for the P gain and 4 for the D gain are generally close to correct for most applications.
An excellent way to better understand these settings is to liken them to a sensitivity control on a cruise control circuit. If the circuit was set for maximum sensitivity (gain values both set to 255) the accelerator pedal would go to the floor as soon as you dropped below the target speed, and the pedal would drop to an idle as soon as you were going too fast. If the circuit was set for minimum sensitivity (gain values set to 0) the accelerator pedal would hardly move if you were going too fast or too slow, and you would almost never be traveling at the desired speed. This same concept applies to how your IAC motor will regulate idle speed.
The "Max. TPS for Idle" field is used to set the threshold where the ECU no longer considers the engine to be idling. It is recommended to observe the TPS reading at an idle and setting this field to that number plus one. In other words, if your TPS reads 10% at an idle, set this value to 11. When the TPS percentage exceeds the value specified in this field, the IAC motor will be "locked" into the position specified in the throttle follower graph, and the Timing Trim graph will not be used.
08-02-2008, 11:23 AM
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Smitty,
You are correct in that the boost compensation table does multiply the 100 map bpw at whatever rpm you are at. That is the only table to control fuel while in boost. You only have your 200-1200, 1200-3600, 3600-6000 rpm etc versus map from 20-100. Then you have the boost compensation table to go from 100 kpa to 200 kpa, every 200 rpm.
You can get away with low 13's when the motor is in vacuum. I do this to increase the economy. When the motor gets into boost, you need to bring it down. The higher the boost, the richer it needs to be. At full boost, you need to be less than 12. How much less than 12 depends on the amount of boost, compression ratio, etc.
You need to first tune the engine in vacuum. Get your 100 map numbers on the money in vacuum and then leave them alone. DO NOT change them to tune the engine in boost. That is what the boost compensation table is for. A good place to start with the boost compensation table is to set it at 1.05 for 105 kpa, 1.10 for 110 kpa, 1.15 for 115 kpa etc....
This will get you in the ballpark. Change those numbers as needed to tune in boost, not the 100 kpa numbers.
You can also play with the AE (acceleration enrichment). This will richen the engine under hard accel. The harder you accel, the more fuel it will give it. I haven't used the Mefi burn, so I can't tell you where to find it.
For idle, you want to open the throttle blades just enough so the engine idles without using much IAC. You have to be sure to reset the tps if it is not at 0 after you move the throttle blades. You also need to check for as close to a 100% reading on the tps at wide open throttle. You can change the ratio of the tps to make it read 0 when its closed and 100% when its open. It takes a little playing around. Hope this answers some of your questions. If you have any more, post them or give me a shout.
Eddie
You are correct in that the boost compensation table does multiply the 100 map bpw at whatever rpm you are at. That is the only table to control fuel while in boost. You only have your 200-1200, 1200-3600, 3600-6000 rpm etc versus map from 20-100. Then you have the boost compensation table to go from 100 kpa to 200 kpa, every 200 rpm.
You can get away with low 13's when the motor is in vacuum. I do this to increase the economy. When the motor gets into boost, you need to bring it down. The higher the boost, the richer it needs to be. At full boost, you need to be less than 12. How much less than 12 depends on the amount of boost, compression ratio, etc.
You need to first tune the engine in vacuum. Get your 100 map numbers on the money in vacuum and then leave them alone. DO NOT change them to tune the engine in boost. That is what the boost compensation table is for. A good place to start with the boost compensation table is to set it at 1.05 for 105 kpa, 1.10 for 110 kpa, 1.15 for 115 kpa etc....
This will get you in the ballpark. Change those numbers as needed to tune in boost, not the 100 kpa numbers.
You can also play with the AE (acceleration enrichment). This will richen the engine under hard accel. The harder you accel, the more fuel it will give it. I haven't used the Mefi burn, so I can't tell you where to find it.
For idle, you want to open the throttle blades just enough so the engine idles without using much IAC. You have to be sure to reset the tps if it is not at 0 after you move the throttle blades. You also need to check for as close to a 100% reading on the tps at wide open throttle. You can change the ratio of the tps to make it read 0 when its closed and 100% when its open. It takes a little playing around. Hope this answers some of your questions. If you have any more, post them or give me a shout.
Eddie
08-04-2008, 02:57 PM
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uuhh yeah, what Eddie said! How are you driving and tuning at the same time?? Eddie got me boosting this weekend and a blew a lower unit. I swear this thing is gonna be the death of me.
Hey Smitty, what is your prop shaft to keel measurement. At even trim I'm at 8" depth. What should it be?
Hey Smitty, what is your prop shaft to keel measurement. At even trim I'm at 8" depth. What should it be?
08-04-2008, 08:41 PM
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I decided to buy the Mefiburn program and do the fine tuning on the water myself this time. Tyler did a pretty good job last time on the water but I don't have time to pizz around this year and never had time last year since coming off the dyno so I'm learning to do it myself a few hours at a time. I drive and try to watch the o2 meter,my son runs the laptop and watches what map setting we are in at each rpm band then writes it down, We stop for a few minutes,go thru the fuel tables upload the new changes then try again. I'ts running real clean now,I just have to get rid of a off idle stumble. I still might pay tyler to do it if I cant get it to work but again,I don't have spare time to make the trip to his shop (90 miles each way) then go out to the water for the day based around his schedule. I'll post any new findings,Smitty
08-04-2008, 08:55 PM
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I was out this morning doing some fine tuning on my boat with my new mefiburn software and I am starting to get a basic understanding of how it works. This was the second time out with it,last week I went out and ran it from idle to partial boost and slightly tweaked the fuel tables. Tyler Crockett did a pretty good job on the dyno last year doing the intial programming,we found a few areas where boat was running 10.8-11 afr at light cruising and leaned them out to 13-1,we were pretty happy with ourselves,I will say there is no way someone should try to do a complete tune to a blower motor without initially having their motor tuned by a expert on the dyno,mainly under boost because you will chance damaging your motor plus it would be awfully difficult to make enough high speed passes under boost while monitering everything and making adjustments. The next day we took the boat out and ran it with the air fuel meter on it to moniter the corrected afr's. To my surprise the afr's we had tuned in at part throttle cruising suddenly were in the high 13's close to 14-1. We went back out this morning and did a re-tune and I found that while motor may be at 12.8-1 to 13-1 let say at 3200 cruising trimmed up with a light load if you leave the drive dug in deep and tabs down deep the map reading goes in the high 80's vs the low 80's and runs off the 90 map fuel trim ve the 80 map trim at a higher percentage throttle opening. So we ran boat AGAIN thru all the rpm ranges both ways and adjusted the fuel accordingly with good results.
My questions for the experts is this-I thought with a 2 bar map sensor and mefi 3 or 4(I'm running a 4a) that there were fuel tables that went all the way to 180 map,not just multiplier tables above 100. If there is I couldn't find them. I have always avoided cruising at 1-4 psi of boost because my boost referencing fuel regulator doesn't really bring fuel pressure up much from base until your pretty far into the boost. I confirmed this today by taking boat to only 5000-5200 at part throttle,it was showing about 1-2 psi boost on gauge and scanner pro was showing map readings of around 100-110. Fuel pressure was bumped up to about 50 psi from base of 40 psi,my afr's climbed to the high 13's which I thinkwould melt the motor down eventually. I bumped up the 5000-5200 rpm/100map fuel trim by about .3 and increased the fuel multiplier table at 105 and 110 by about .05,on the next identical run my afr's were down in the mid 12's.
Do the multiplier tables above 100 multiply the fuel trim at 100 map?
Lets say you were far into the boost and you were at 140 map,would it still be multiplying on the last fuel table at the same rpm at 100 map?
My cam is fairly large,what other adjustments can I make at IDLE and just off idle other then timing and the fuel trim bpw at the map setting it happens to be running at to get better throttle response and idle quality? Thanks for any info,Smitty
My questions for the experts is this-I thought with a 2 bar map sensor and mefi 3 or 4(I'm running a 4a) that there were fuel tables that went all the way to 180 map,not just multiplier tables above 100. If there is I couldn't find them. I have always avoided cruising at 1-4 psi of boost because my boost referencing fuel regulator doesn't really bring fuel pressure up much from base until your pretty far into the boost. I confirmed this today by taking boat to only 5000-5200 at part throttle,it was showing about 1-2 psi boost on gauge and scanner pro was showing map readings of around 100-110. Fuel pressure was bumped up to about 50 psi from base of 40 psi,my afr's climbed to the high 13's which I thinkwould melt the motor down eventually. I bumped up the 5000-5200 rpm/100map fuel trim by about .3 and increased the fuel multiplier table at 105 and 110 by about .05,on the next identical run my afr's were down in the mid 12's.
Do the multiplier tables above 100 multiply the fuel trim at 100 map?
Lets say you were far into the boost and you were at 140 map,would it still be multiplying on the last fuel table at the same rpm at 100 map?
My cam is fairly large,what other adjustments can I make at IDLE and just off idle other then timing and the fuel trim bpw at the map setting it happens to be running at to get better throttle response and idle quality? Thanks for any info,Smitty
MEFI 3 only has a Boost compensation table at 5kpa intervals, starting at 105kpa. MEFI 4 has a few rpm points, 4A and 4B both have Kpa compensation tables from 100-200Kpa. All MEFI's use boost as a multiplier of the 100Kpa base run fuel table. MEFI 3 is a bit tougher, you need to compensate in some areas for the lack of tables, but it gets the job done.
To map properly, it helps to have a oversized and undersized prop, as well as adjusting trim up and down.
Timing has a big effect on idle. You can adjust the butterfly a bit, close the air down, and give it more timing in the base table.
There's thousands of other ways to make it better but you have to get far deeper into the software. Without being able to program on the fly, trial and error takes forever.
Dustin
08-04-2008, 08:58 PM
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I decided to buy the Mefiburn program and do the fine tuning on the water myself this time. Tyler did a pretty good job last time on the water but I don't have time to pizz around this year and never had time last year since coming off the dyno so I'm learning to do it myself a few hours at a time. I drive and try to watch the o2 meter,my son runs the laptop and watches what map setting we are in at each rpm band then writes it down, We stop for a few minutes,go thru the fuel tables upload the new changes then try again. I'ts running real clean now,I just have to get rid of a off idle stumble. I still might pay tyler to do it if I cant get it to work but again,I don't have spare time to make the trip to his shop (90 miles each way) then go out to the water for the day based around his schedule. I'll post any new findings,Smitty
Dustin
