Tuning EFI
02-08-2006, 09:59 PM
#1
Burning Brakes
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Tuning EFI
I street tune my car, but today I took my car to a dyno 60 miles north of Atlanta - Dyno4mance. They use a Dyno Dynamics dyno that has all the bells and whistles. It can dyno 4wd cars, map ignition, boost, AFR and hold nearly any kPa and RPM. Wow was it great tuning the car on this thang.
We ran through nearly every cell from idle to full boost and mapped the exact AFR for each cell (remember, I've been street tuning) - what fun. It took nearly 2 hours to map the AFR's, so we did not get to the ignition.
I watched them set ingition on a WRX - on one cell, they advanced timing until HP peaked then dropped off. They backed off the timing to get back to best HP then moved to the next cell. This took a lot of time and I had to leave before they were finished, but I did see them reach peak torque. It was interesting to see they backed the timing off directly after reaching peak.
If you live near North Georgia, I highly recommend the guys and their dyno at Dyno4mance in Calhoun.
One last point - why do some dyno operators use a corrected value and some don't? If you decide to use a correction value, how do you determine what that value will be?
We ran through nearly every cell from idle to full boost and mapped the exact AFR for each cell (remember, I've been street tuning) - what fun. It took nearly 2 hours to map the AFR's, so we did not get to the ignition.
I watched them set ingition on a WRX - on one cell, they advanced timing until HP peaked then dropped off. They backed off the timing to get back to best HP then moved to the next cell. This took a lot of time and I had to leave before they were finished, but I did see them reach peak torque. It was interesting to see they backed the timing off directly after reaching peak.
If you live near North Georgia, I highly recommend the guys and their dyno at Dyno4mance in Calhoun.
One last point - why do some dyno operators use a corrected value and some don't? If you decide to use a correction value, how do you determine what that value will be?
02-08-2006, 10:10 PM
#2
Nordschleife Master
Don, that is the proper way to determine the optimum ignition angle for a given engine combination operating with a certain octane fuel and at a give intake air temp and engine temp. The WRX engine is actually more responsive to ignition timing than the Porsche engine and on those, I'm very careful not to reach the point where the torque drops off. When the torque is dropping off, the engine is detonating whether you hear it or not.
The correction relates to correcting the air density and air temperature to standard conditions, whether corrected to standard temperature/pressure, or SAE Adapted, or any other standard that you want. By using the correcting method, you can compare dyno numbers from one day to the next and theoretically from one dyno to another. Where it is useful is when you use the same dyno and want to compare numbers from different dyno sessions. Personally, I use STP correction.
I have found that only the Dynapack and Dyno Dynamics chassis dynos capable of holding a load within a 1hp range so you can adjust the ignition timing and see the result.
The correction relates to correcting the air density and air temperature to standard conditions, whether corrected to standard temperature/pressure, or SAE Adapted, or any other standard that you want. By using the correcting method, you can compare dyno numbers from one day to the next and theoretically from one dyno to another. Where it is useful is when you use the same dyno and want to compare numbers from different dyno sessions. Personally, I use STP correction.
I have found that only the Dynapack and Dyno Dynamics chassis dynos capable of holding a load within a 1hp range so you can adjust the ignition timing and see the result.
02-08-2006, 10:45 PM
#3
Formula One Spin Doctor
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Hello Don,
I have found that Some dyno operators will tend to use the correction factor that gives the highest readings , So unless you request or specify to use a correction factor ( eg. SAE or Din rating ) most will not do so.
What is really great at this time , is the fact that a dyno is available in most parts of the country and regardless of brand or type there is no reason for not getting on one and making correct adjustments, as they are worthy tools.
www.tpgproducts.com
I have found that Some dyno operators will tend to use the correction factor that gives the highest readings , So unless you request or specify to use a correction factor ( eg. SAE or Din rating ) most will not do so.
What is really great at this time , is the fact that a dyno is available in most parts of the country and regardless of brand or type there is no reason for not getting on one and making correct adjustments, as they are worthy tools.
www.tpgproducts.com
02-08-2006, 11:33 PM
#4
Burning Brakes
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Thank you
For today's session, the operator used "0" as the correction factor. He input the temp, humidity, altitude into the unit before the tuning. Is this his baseline? The owners are Brits, so they say they like looking at dyno numbers that are corrected to common Euro format. Since he was on the clock, I did not ask for an explanation.
Is the STP, SAE or DIN factor a number or a set of conditions?
For today's session, the operator used "0" as the correction factor. He input the temp, humidity, altitude into the unit before the tuning. Is this his baseline? The owners are Brits, so they say they like looking at dyno numbers that are corrected to common Euro format. Since he was on the clock, I did not ask for an explanation.
Is the STP, SAE or DIN factor a number or a set of conditions?
02-08-2006, 11:43 PM
#5
Formula One Spin Doctor
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Originally Posted by DonE
Thank you
For today's session, the operator used "0" as the correction factor. He input the temp, humidity, altitude into the unit before the tuning. Is this his baseline? The owners are Brits, so they say they like looking at dyno numbers that are corrected to common Euro format. Since he was on the clock, I did not ask for an explanation.
Is the STP, SAE or DIN factor a number or a set of conditions?
For today's session, the operator used "0" as the correction factor. He input the temp, humidity, altitude into the unit before the tuning. Is this his baseline? The owners are Brits, so they say they like looking at dyno numbers that are corrected to common Euro format. Since he was on the clock, I did not ask for an explanation.
Is the STP, SAE or DIN factor a number or a set of conditions?
02-09-2006, 04:58 AM
#7
Burning Brakes
Interesting. I just went on one the EFI101 classes here in the UK. It was excellent and they showed you tuning a car in the same way and also on a Dyno Dynamics one.
So was your 'street tuned' table way off or close? Also how did tune it on the street? - what benchmark did you use whilst tuning the ignition timing?
Before, I was thinking about street tuning but then after this course you could do your base maps in a good few hours- worth the money I would say. Then you can adjust the off base stuff yourself on the street and take as much time as you want.
So was your 'street tuned' table way off or close? Also how did tune it on the street? - what benchmark did you use whilst tuning the ignition timing?
Before, I was thinking about street tuning but then after this course you could do your base maps in a good few hours- worth the money I would say. Then you can adjust the off base stuff yourself on the street and take as much time as you want.
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02-09-2006, 01:03 PM
#8
Burning Brakes
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The reason I'm asking all the questions about correction is that they would not give me me any HP numbers until I told them what correction number I wanted to use - the session was to set AFR so HP was not important. Otherwise, I would be shocked at how low the result is. What a potential scam - don't like your HP numbers? Here, let me dial in a different correction factor. There, how is 720 rwhp? This kind of explains the suspect high numbers.
My next visit will be to set the ignition, so a HP reference will be required.
I did not go to do full power pulls - I went to tune drivability. When loading the engine on this dyno, the inlet air temp and oil temps rise quickly. Once we hit 40 C inlet temp, I stopped the tuning to let the heat soak reduce. We put a large fan on the IC but it could not keep the temps down during the tuning like driving on the road. So, two hours were dedicated to the cells between 2500 rpm/55kPa and 5200rpm/150kPa. Let me tell you, the 150 kPa tuning had to be fast - I bet the turbo and headers were cherry red.
Miles - my street tuning numbers were damn close, but only in the cells I spend the most time in. For example, 2500 - 3500 rpm and 40 - 80 kPa were very very close. Everywhere else needed adjustment to get the AFR I wanted. By doing this on the dyno, I found my fuel enrichment tables needed to be adjusted (increased) because I found that I was using the VE table (partially) to add fuel where the accel tables should have been doing this. By adjusting the accel tables correctly, I found that I have better throttle response. I can now say with sincerity that there is a benefit to the 8.0:1CR and the 964 crank.
So, the question is, did I waste a lot of time and effort on street tuning? Not really, because I had nothing extra invested and I learned a lot about tuning, albeit the hard way. When I got to the dyno, I knew what I wanted and I was able to make it happen on my own - pretty rewarding actually. I feel I understand not only my engine's characteristics, but also the EFI software and how relational all the tables are.
My next visit will be to set the ignition, so a HP reference will be required.
I did not go to do full power pulls - I went to tune drivability. When loading the engine on this dyno, the inlet air temp and oil temps rise quickly. Once we hit 40 C inlet temp, I stopped the tuning to let the heat soak reduce. We put a large fan on the IC but it could not keep the temps down during the tuning like driving on the road. So, two hours were dedicated to the cells between 2500 rpm/55kPa and 5200rpm/150kPa. Let me tell you, the 150 kPa tuning had to be fast - I bet the turbo and headers were cherry red.
Miles - my street tuning numbers were damn close, but only in the cells I spend the most time in. For example, 2500 - 3500 rpm and 40 - 80 kPa were very very close. Everywhere else needed adjustment to get the AFR I wanted. By doing this on the dyno, I found my fuel enrichment tables needed to be adjusted (increased) because I found that I was using the VE table (partially) to add fuel where the accel tables should have been doing this. By adjusting the accel tables correctly, I found that I have better throttle response. I can now say with sincerity that there is a benefit to the 8.0:1CR and the 964 crank.
So, the question is, did I waste a lot of time and effort on street tuning? Not really, because I had nothing extra invested and I learned a lot about tuning, albeit the hard way. When I got to the dyno, I knew what I wanted and I was able to make it happen on my own - pretty rewarding actually. I feel I understand not only my engine's characteristics, but also the EFI software and how relational all the tables are.
02-09-2006, 01:34 PM
#9
Nordschleife Master
Don,
It is true that you can manipulate several different factors on the dyno to get the results you want. The key is to pick a standard and then use this all of the time. I would suggest using STP or SAE correction factors here in the US.
On a dyno, your engine WILL run hotter than on the street unless you have a very well thought out dyno cell with proper cooling. You NEED to have your air temp correction table correct or your car will run lean once you are in a street or track environment and your tuning will a waste of time. This is where data logging and a wide band O2 sensor is helpful because you can data log the AFR and then look at the RPM and load site the engine is operating at. If your air temp correction table is set properly, then little to no adjustment is required on the street. THIS is where I have seen many engines melt down due to excessively lean conditions on the street but a dyno sheet that looks safe.
The Acceleration enrichments only need to be adjusted once the main fuel table has been completed and can be done on the street. They are irrevelant during steady state dyno tuning.
On a dyno, you'll not be able to reach all of the cells, but if you use 1st gear you'll be able get to some of the lower load sites. I think that validating AFRs after the dyno session is a very valuable exercise. You can do it in car with a wide band meter or ideally using data logging.
It is true that you can manipulate several different factors on the dyno to get the results you want. The key is to pick a standard and then use this all of the time. I would suggest using STP or SAE correction factors here in the US.
On a dyno, your engine WILL run hotter than on the street unless you have a very well thought out dyno cell with proper cooling. You NEED to have your air temp correction table correct or your car will run lean once you are in a street or track environment and your tuning will a waste of time. This is where data logging and a wide band O2 sensor is helpful because you can data log the AFR and then look at the RPM and load site the engine is operating at. If your air temp correction table is set properly, then little to no adjustment is required on the street. THIS is where I have seen many engines melt down due to excessively lean conditions on the street but a dyno sheet that looks safe.
The Acceleration enrichments only need to be adjusted once the main fuel table has been completed and can be done on the street. They are irrevelant during steady state dyno tuning.
On a dyno, you'll not be able to reach all of the cells, but if you use 1st gear you'll be able get to some of the lower load sites. I think that validating AFRs after the dyno session is a very valuable exercise. You can do it in car with a wide band meter or ideally using data logging.
02-09-2006, 01:48 PM
#10
Don or Geoffrey,
I thought that the process of tuning cell by cell on a dyno usually involved adusting fuel input to achieve the the correct AFR, then immediately adjusting timing to optimize torque (and maybe double checking each again) all while running at constant speed and load. Then you move to the next cell and do it again.
It sounds like you're doing the fuel and ignition tuning in separate sessions. How typical is that and why are you doing it that way?
I thought that the process of tuning cell by cell on a dyno usually involved adusting fuel input to achieve the the correct AFR, then immediately adjusting timing to optimize torque (and maybe double checking each again) all while running at constant speed and load. Then you move to the next cell and do it again.
It sounds like you're doing the fuel and ignition tuning in separate sessions. How typical is that and why are you doing it that way?
02-09-2006, 03:29 PM
#11
Burning Brakes
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Originally Posted by Geoffrey
Don,
On a dyno, your engine WILL run hotter than on the street unless you have a very well thought out dyno cell with proper cooling. You NEED to have your air temp correction table correct or your car will run lean once you are in a street or track environment and your tuning will a waste of time. This is where data logging and a wide band O2 sensor is helpful because you can data log the AFR and then look at the RPM and load site the engine is operating at. If your air temp correction table is set properly, then little to no adjustment is required on the street. THIS is where I have seen many engines melt down due to excessively lean conditions on the street but a dyno sheet that looks safe.
The Acceleration enrichments only need to be adjusted once the main fuel table has been completed and can be done on the street. They are irrevelant during steady state dyno tuning.
On a dyno, you'll not be able to reach all of the cells, but if you use 1st gear you'll be able get to some of the lower load sites. I think that validating AFRs after the dyno session is a very valuable exercise. You can do it in car with a wide band meter or ideally using data logging.
On a dyno, your engine WILL run hotter than on the street unless you have a very well thought out dyno cell with proper cooling. You NEED to have your air temp correction table correct or your car will run lean once you are in a street or track environment and your tuning will a waste of time. This is where data logging and a wide band O2 sensor is helpful because you can data log the AFR and then look at the RPM and load site the engine is operating at. If your air temp correction table is set properly, then little to no adjustment is required on the street. THIS is where I have seen many engines melt down due to excessively lean conditions on the street but a dyno sheet that looks safe.
The Acceleration enrichments only need to be adjusted once the main fuel table has been completed and can be done on the street. They are irrevelant during steady state dyno tuning.
On a dyno, you'll not be able to reach all of the cells, but if you use 1st gear you'll be able get to some of the lower load sites. I think that validating AFRs after the dyno session is a very valuable exercise. You can do it in car with a wide band meter or ideally using data logging.
Good points.
I have the temp correction tables set and adjusted. I verified everything we did on the street going home. I have a wide band in the car and the cabability of data logging. Good stuff.
The dyno shop is well thought out, but not for my 930 where I have oil cooling in the front and a big IC in the back. He only had one 22,000 cfm fan and we used it for oil cooling. The smaller fan was put on the IC. Ben has used this facility for the EFI 101 course.
Once the VE table was set with the new values, I tweeked the enrichment tables accordingly, again on the way home. Fortunately, I had over 60 miles of freeway to set the enrichments.
Rgds
02-09-2006, 03:54 PM
#12
Nordschleife Master
you'll find that beyond about 3500 there is enough air velocity and you won't need much if any acceleration enrichments at all. 8.0:1 is nice huh? I think that is about the optimum compression ratio for this engine.
02-10-2006, 12:55 AM
#13
Formula One Spin Doctor
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Hello Don,
40 C would not be considered high intake temperature, as you will find it is about average, when you are running the car on the street in boost it will get higher than that , unless you have a really large intercooler setup, or it happens to be a pretty cool day. You should data log your intake temps after a few hard passes on the street thru the gears , this will give you an average baseline of your intake temperature. When on the dyno you can use this info to make your adjustments.
40 C would not be considered high intake temperature, as you will find it is about average, when you are running the car on the street in boost it will get higher than that , unless you have a really large intercooler setup, or it happens to be a pretty cool day. You should data log your intake temps after a few hard passes on the street thru the gears , this will give you an average baseline of your intake temperature. When on the dyno you can use this info to make your adjustments.
02-10-2006, 12:18 PM
#14
Burning Brakes
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Yes, the 8.0:1 pistons seem to work real well now that the tuning is nearly complete. Just stab the throttle a bit at nearly any RPM and you will get an immediate kick. I've found the engine likes that quick juice immediately (manifold and throttle position enrichment), but nearly as quick, start taking it away gradually and let the VE take over from there.
A Wayne - thanks again.
A Wayne - thanks again.
