This is an article for noobs all the way up veterans still tuning on inertia dyno’s. I will go threw some very noobish stuff and make my way up to the actual tuning itself.
- AFR or air fuel ratio is referred to as a # of air to 1 part of fuel or some#:1, (like 14.7:1 which is 14.7 parts of air to one part of fuel) 14.7:1 is stoichiometric. Stoich is where you get the most complete burn and is only used for emitions. Performance tuners use AFR for heat control. Leaner AFR can get you higher power but not enough to make a difference. Example if you are on a dyno and are tuning wide open throttle or WOT and you change from a 12.5:1 to a 14:1 there might be at the most a 10 hp difference. This small difference is not enough to put your motor at risk of catastrophic failure.
- First, the reason that they refer to timing as advancing timing is because when your motor ignites its air/fuel or a/f mixture it is BEFORE top dead center. The reason for this is that fuel takes a long time to burn so igniting this mixture before top dead center, you achieve peak cylinder pressure sometime after TDC. What degree doesn’t really matter and every motor is different. More on this part later.
C/R or compression ratio- This is the difference between the amount of volume that is in a cylinder compared to volume when the piston is at TDC. Basically it is how much the motor squishes the air fuel mixture together. (Example 12:1 C/R this is a pretty high C/R for the street and a lower C/R is 9:1, this is turbo friendly)
DETONATION- This happens from a couple different things. One is a hot spot in the cylinder like a piece of hot carbon or a thin spot in the piston that ignites the fuel before it is ready. This is not that likely it usually has to do with bad tuning. Like timing if you advance timing to much you get peak cylinder pressure BTDC. If you raise the C/R you are forcing molecules closer together and that means the flame front travels faster and creates faster ignition and getting peak cylinder pressure BTDC. Same thing with a turbo or supercharger, you are forcing more air into the cylinder so the piston will compress it more because you are forcing so much more air than it normally receives. This is combated by a lower C/R, retarded timing, or both.
- Dynamometers- there is three main types of dyno’s that are used, AssDyno’s, inertia dyno’s and load type dyno’s. AssDyno’s are where you sit in your car and try to feel the difference in HP and should NEVER be used not only for safety (hard to see the road and gauges you need at the same time) but your ass can not tell the difference between 300 and 310 HP. Inertia dyno’s like Dynojet use heavy drums that the tires spin. It calculates how fast you accelerated these drums to calculate horsepower and from that get torque. Load type dyno’s use some kind of brake to slow or stop acceleration and even can even make the car decelerate. These dyno’s are superior to inertia dyno’s and is reflected by the price to use them. The RIGHT way to tune car can only be achieved on a load type dyno. More on this later.
- You need a datalogger of some type, try to get a program with both tuning and datalogging incorporated into one nice package, it saves lots of time and as far as I’m concerned this is the only way to go. Map tracing also aids in tuning.
- Wide Band Oxygen (WO2, Lambda, Uego, AF/R meter…) Sensor. The main tool used to tune along with a Dynamometer. This TOOL is used to find your AFR. If you don’t know for sure what you want to set your AFR to then keep reading this article to gain some knowledge then pay someone to tune your car.
TUNING
You have a way to change fuel and ignition maps, a datalogger with map tracing and some time at a Load type dyno. Lets go threw the steps of tuning a Honda VTEC motor.
For this example I will be using Crome Pro(because it has tons of features making it easier to tune) and a Moates Ostrich Real Time Programmer because that is what I use but this will work for any software (uberdata, Hondata, AEM EMS, Autronic, Haltec, ect.) When tuning you want to tune your AFR first and your ignition second.
Your engine will run on a 10:1 AFR all the way up to a 18:1 so set your basemap up conservative, both fuel and ignition. Also set your VTEC at 6000 rpm to tune your low fuel map first.
When you get your RTP (real time programmer) and your data logging hooked up it is time to start tuning your idle. Just watch the map tracer and select that cell it settles on and adjust the fuel up or down to where you want it. With Crome all you have to do is press (Ctrl+Up) or (Ctrl+Down) to make that cell add or subtract fuel.
Now to start tuning load... In Crome the rpm is on the left going top to bottom, vacuum and pressure is on top going from left to right. This is where having a load type dyno helps tuning. You can keep it at a certain rpm but change the Load (throttle or vacuum/boost). Start at a low rpm and work your way up. Choose a number that is in the column not in the middle of two columns; this is important because if you don’t get it exactly on the cell it will not be accurate because they use percentages of the surrounding cells too fill in between the cells when moving between cells; so if one cell gives you 10:1 and the one right next to it gives you a 16:1 and you are right between the two you would get a 13:1 AFR.
Lets say you start at 1000 rpm, put a really light load on the motor and see where the map tracer sits and tune that cell until it is at the AFR you want. Then add a little throttle until you get the map tracer centered on the cell just right of the one you just tuned and then add or subtract fuel till you get your desired AFR. Keep moving the cell right, after you tune that cell. Do this until you get to WOT (Wide Open Throttle or full throttle)
Now you have all of your 1000 rpm tuned and it is time to go to the next cells down. On the JDM P30 rom it would be 1250 rpm. Start at a light load and work you way up to WOT just like the last row.
Do these steeps for all the rpm’s in the low fuel maps.
Now set the VTEC point at 3500 rpm and start tuning your High Cam fuel map just like you did for the low cam fuel map.
Smooth your fuel maps.
Now that you have setup all of your fuel maps it is time to go on to timing. This is where ALL of your power will be made. Also everyone says that timing affects your AFR but it does not, you have to ask yourself does timing really have anything to do with how much fuel was squirted into the cylinder; regardless of when you ignite that cylinder your AFR has already been chosen by how much fuel your injectors just squirted out.
Set you VTEC point back to 6000 rpm.
Tuning your timing is just like tuning your fuel except instead of watching your WO2, you watch how much HP or Horse Power your car is making. Start at 1000 rpm, put a really light load on the motor and see where the map tracer sits and tune that cell until you get the highest HP. If you add ignition timing you will see the HP from the dyno go up and when it stops getting higher stop or if it goes lower subtract some timing until you achieve the highest HP out of that cell and move on to the next cells until all of the cells in that row are finished. Move to the next row and repeat those steeps until your entire low ignition map is finished. Tuning timing like this is the only right way to tune timing because not only do you get peak power everywhere but getting peak HP is far from getting detonation. If you are getting detonation and tuning timing this way it is probably from a hot spot in the cylender (most likely a hot piece of carbon) so check your AFR and richen up your fuel to cool down the cylinder.
Raise your VTEC point back to 3500.
Tune your High Cam ignition map just like your low cam map.
Now smooth ignition maps.
With your VTEC point still at 3500 do a power run.
Now raise it to 6000 rpm and do another power run.
Look at your dyno charts and see where the torque curves meet; set your VTEC point where the lines meet.
That’s it, now your car is tuned.
Last edited by ickyhonda on Thu Jun 08, 2006 12:04 pm, edited 2 times in total.
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