pgmfi.org

Im finding tons of info on tuning boosted motors.

Not so much on NA motors, trying to do some research. Can anyone point me in the right place?

Im looking for what AFR's im going to want to shoot for. 14.7 is obviously stoich, but is that okay for a higher compression. The motor will be about 12:1. Some good reading material would be great!

Thanks.

-Coreytehtuningnewbb

At WOT, I usually aim for 13.5:1, depending on the fuel as a starting point.

Back from the grave. I see this post and since I have a B20vtec self tuned on Chrome I feel I should add to this subject for any further inquiries. First let me say that my first tuning experience was a B18ls with b16 pistons, and a Gsr head with type r cams. Not a beginners tune, but a learning step for sure. 1st once I had ran the motor on a stock ecu (not very well) and purchased the equipment to tune with, I had good luck, everything was going good... I made lots of power on the butt dyno. Then as a sudden drop in air temp occurred, I also lost an injector (partially) but with limited experience I was stuck on thinking it had something to do with IAT fuel multipliers. So once the air was warm again... several months latter, I realized my problem was mechanical. By now the damage was done, the motor ran, but just wasn't what it was before. So Now that brings me to the B20vtec. Same GSR head, with Type R cams, and now I used the B20 block with dish pistons. One day it will be High Comp, but for now it is what it is.... Stock.

The previous reply is miss leading. 13.5 is good for idle, but if one is looking to make good power with any NA setup, you need to be closer to 12.5 on pump gas. this will vary +- .03 or so depending on your motors eating habits.

So lets get some things out first. These are some positions that you need to know in your maps. These are the Columns, with the rows being your RPM.
1. WOT= Wide open throttle typically the last 2 columns with the lowest vacuum #9-10 12.5 afr
2. High Load= #7-8 and sometimes 6 depending on your motors efficiency. This is a moderate acceleration, but not WOT 12.5-12.8 afr sometimes close to 13.2 if you are looking to save fuel, and not have the greatest response.
3. Cruise= #5-6 but typically 5, this being going down the road not up or down hill. without Accel/Decelerating, No E Brake LoL Here I like to go around 13.5-13.8 afr you can go leaner, but if you have an issue, or your multipliers aren't set up great, then you can run lean and theres no room for error.
4. Negative/Low Load= #1-4 with the highest Vacuum. This is when you are decelerating, or the cars momentum is turning the motor. Typically you want to gradually go from the 13.5 at cruise and lean out to 14.1 at the lowest point on the map, but you can also stay around 13.5, though if your afr's jump richer you may get some backfire while you shift gears. so its best to have it lean a little, but if it starts to pop like a cherry bomb muffler, then you are too lean, and need a little more fuel.
5. Idle= There are two types of idle. High idle, and Low idle. When the car is cold it typically idles around 11-1500 RPM, this also can happen while rolling with your foot off the accelerator and the clutch in, which is good if you have a light weight Flywheel, and is what I would call a high idle. Like wise the Low idle is when the motor is warm, and you are sitting still. This is important because when the car idles high with the throttle body closed the vacuum is higher and it will read in columns 2-3 while when the idle is lower it will have less vacuum and read in columns 3-4.

If you use an ostrich or you just burn chips, you always want to do the same thing. Only using an ostrich with real time tuning is less time consuming, but with time you can end up with the same results.

Step one is to tune for idle. This is rather easy, but you will find in some cases with larger injectors the smallest adjustments will make a big difference, and its easily gets frustrating here.
Typically you want to get it to run safe with afr between 12.5-13.5 until the motor is warmed up, then make adjustments making sure that fuel at idle in Advanced tables under Tools are set at 1.00 for anything above 70 deg. This is to make sure your adjustments are correct, and since IAT is involved with your fuel mixture as well, theres not much needed if the air is cold you will run richer. This is good as it adds lubrication to parts that are not warm, and not expanded to there desired specs, and will make your rings and cylinders last longer by doing so, but for now we want it to run the way it should warm, then change the tables afterward to get the results you are looking for. Once the engine is warm, you can get it to idle around 13.5 both while sitting and while rolling. Keep in mind that there are a lot of tables for idle in the Advanced Tables section under Tools. you can adjust the speed of the engine for ECT, and the Fuel Multipliers as well. Keep in mind that every set up is different, and you will have to play around. Key note. The higher the flow of fuel, and the higher the pressure, the smaller some of these values will have to be.

Next if you dont have a ostrich, you will be guessing a lot, so the best way to do this is to go out and drive, and split everything up. check your afr's at 2500 rpm, and at 4000 rpm. then 5500, and keep notes as to what changes you need to make.
Some things to note. If you go rich when you first rapidly accelerate, or decelerate then it goes back to where it is supposed to be, and you dont see this type of issue when you gradually climb into it or let out of it very slowly, then you need to go to Plugins and add fuel tools to you rom. This will then become available under Tools, Fuel Multipliers, and Advanced. you will see Tip in, and Additional Tip in. Tip in typically changes the response during acceleration, and Additional Tip in is for Decelerating. I have always had my values set for 0.450 for both, but with the addition of a 255lph fuel pump, I have now set the additional to 0.250 due to what I think is the injectors having more resistance and taking longer to close. I dont know thats only a guess, but as always it doesnt matter what you do, if it makes you engine run right, then your doing something right.

Just be patient, and get your Afr's right, then you can tweek the timing, but on NA set ups, the timing typically doesnt change much from the base map, if you are confident you know what you are doing thats fine, but I would sugjest going to have it tuned if you want to safely squez out 5 more hp. Though you should always check for audible knock by putting it in 5th gear at a very low RPM, and mashing the throttle. listening as the rpm rises for that ping of bad gas. Its not bad gas, your timing is just to high. You will have to take timing out in the lower rpm's of a High Comp motor, and you should do this test about 3 times in a row to get the cylinders warmed up as if your in traffic. Also another sound of knock I describe as the sound of valve float. It will occur when Vtec engages, and you will notice as it goes away that you feel more power. This is never good for B20's but stock NA can endure it a bit as you get your Afr's where they should be.

A note on Detonation, and knock... If your Afr's jump around at all ie. from 12.1-12.6 back and forth, you will here knock, and if it goes too lean or rich ie. 11.8 or 13.8 in WOT you will hear knock or detonation. So unless its just so bad that you think your motor is going to throw pieces at you, just focus on getting your Afr's to be smooth, and most of any detonation will go away, then tune the timing, and check Afr's again. As you change timing, you will change your Afr's as well, though its usually not noticeable, it can be. This is because you are telling it to start the burning of the fuel sooner or latter in the cycle and there for there is more or less fuel available to be detected down stream at your o2 sensor.

All in all learning to tune yourself is a long process, and if your have mechanical problems along the way you will be led into thinking its something you did in your tune, so hopefully you start on something that has been working rather than that fresh build, and can be patient, you will be rewarded for your efforts with a car that you not only built, but tuned yourself.

If you have to run a naturally aspirated engine at 12.5:1 to make maximum power on gasoline, your combustion chamber sucks or your ignition timing is too advanced or both.

I'd say YOUR post is misleading since you seem to have a handle on some of the basics of tuning, but probably don't have a good idea WTF is actually going on inside the engine.

The only way to find out what AFR the engine really prefers is to tack the car to a track where you can have a mostly controlled environment to get some repeatability into your runs, or tune on a dyno and see where MBT is developed at what particular combination of AFR and ignition timing.

13.5:1 AFR is patently stupid for (warm) idle, especially if you have to pass emissions testing. The only except to this is some very beefy cams may need overly rich AFRs at idle because the gas velocity is so poor that the fuel sprayed doesn't really make it into the chamber easier, and what does get into the chamber isn't usually atomized as well, or, with a highly developed engine with an extremely efficient exhaust manifolds, you could possible over-scavenge on overlap and draw a lot of mixture through the engine, but that is rarely the case with any Honda engine with an off the shelf header.

So . . . I will completely disagree with you on what you suggest as "safe" or effective AFRs, especially since I tune most low pressure turbo engines to 12.5:1 AFRs and they like it quite a lot. Higher RPMs (7.5K+) and high boost (above 1BAR) should get a bit richer, for sure, but even on a stock engine with at turbo, 12.5:1 is more than enough to be safe if you aren't being a douchetard with the timing maps.

Agreed All stock internal engine that I tune under 10 psi are tuned NO richer then 12.3:1 Its the honey spot for making power and giving longevity to the engine.