If you are wanting to start tuning your setup, and have a piggyback/chip burner/romulator/standalone, but don't know what you need to be aiming for, this FAQ with help answer your questions.

I have been tuning engines for friends and myself for a few years now. I'm by no means an expert, but I have a moderate amount of experience, I understand the combustion process very well, and have had very good results with everything I've tuned. I have the most experience with RaceTech's EM4-F, but I have also tuned motec, emanage, SAFC, and with a romulator.

Lets start with some definitions;
BDC: Bottom Dead Center. The position of the piston when it's at it's lowest point in the cylinder.
TDC: Top Dead Center. The position of the piston is at it's highest point in the cylinder.
BTDC: Before Top Dead Center. Usually in degrees of crank angle, this is the position of the piston in the cylinder bore before it reaches TDC.
ATDC: After Top Dead Center. Usually in degrees of crank angle, this is the position of the piston in the cylinder bore after it reaches TDC and is descending towards BDC.
NOT: Normal Operating Temperature. This is the temperature the motor stays at once it is fully warmed up.
WOT: Wide Open Throttle. The throttle is fully depressed.

OK, now that we understand what all of these words mean, lets move on to actually tuning your engine. All tuning starts with ensuring that the system is working as it should. This means checking that you have adequate sized injectors, a good fuel pressure regulator, proper fuel pressure, a good fuel pump, clean fuel filter, no kinked hoses or lines, and no leaks in the fuel system. Then, we want to make sure the intake system (everything from the back of the MAFS [IF YOU HAVE ONE] to the cylinder head) is sealed and not leaking. Leaks in the intake system cause all kinds of hard to fix problems that make tuning a pain. Next is the ignition system MAKE SURE YOUR PLUGS LOOK GOOD AND THE GAP IS SET!!! This is SOO important. I'm amazed at how often this is overlooked. Check your plugs, check your plugs, check your plugs! Next, if you have them, check the plug wires, cap, rotor, and coil. Now check that the ignition timing at the crank actually matches what's happening at the crank. Once again, this is a very simple step that is often overlooked. If the timing is off +5°, that can easily be the difference between a little knock from too much timing, and a bent rod, or a hole in a piston, or a blown HG from serious detonation. Last, but not least, is the oil. Make sure it's fresh, AND OF THE CORRECT VISCOSITY!!! There is little that will thin oil faster than a few pulls on a dyno.

(Note:I have a personal rule, that I don't do more than 4 pulls without shutting the motor off and letting the coolant and oil cool down for 10-15min or so. If you're REALLY confident in your engine cooling and oil cooling system, this doesn't have to apply, but be careful)

Now that we're confident the motor isn't going to have some mechanical failure, we can start the actual tuning process. I'm not going to get very detailed here, just cover the basics. First thing is to get the motor idling and up to NOT. Unless you're using a stock ECU, or a standalone that allows for closed loop at idle, you want your AFR'S to be around 12:1. This will vary for different motors, so just treat that as a starting point. We will also want to adjust the timing so that it gives a stable idle. What you may notice is that as you adjust the timing and fuel, you'll have to re-adjust the the other. This is normal. There is a relationship between timing and what AFR is showing up at your sensor. I'll explain why later. Just give the motor what it wants. It took me a long time to stop questioning why different motors like different things. If it runs well, and it sounds well, and it makes good power, it's right. The books and numbers don't matter. Results matter.

Ok, so now you should have the car idling well. First we want to set up a quick timing map. In most systems, you want to start with some sort of base map to work with. Building a timing map from scratch can be excruciating depending on the system. The timing should slowly ramp up from idle to around 30° (If I don't specify, all timing will be given in degrees BTDC) and reach maximum timing around 2500 rpm. Once again, these are just starting points.

Now for the fuel. As with the idle, we're going to aim for about 12:1 at WOT all the way to redline. This will probably take a few pulls to even get the car to make it to redline. Watch the AFR'S closely. For right now, if you see anything leaner than 13:1, get out of it. Add some fuel where it leaned out, and any rpm and load point above that an equal PERCENTAGE more. It's important to keep the idea in your head that if you change the number at a given load point by "5", you can't just add "5" everywhere above that. You need to find out what percentage change "5" was for that load point, and apply that change to every load point above that. Most standalones will let you do this easily. If they don't, it will just take a little longer to do the tuning. Once you've got the car capable of making a pull all the way to redline, start trying to get the AFR'S evened out so that your AFR'S look like a line around 12:1 all the way to red line. For now, we're done. There is more we can do with fuel, but for now, lets move on to timing.

The timing is a bit more time consuming, and you have to be careful here, especially if you're on pump gas. (excluding E85 and other alcohols, that is a "whole 'nother can o' worms", as they say)Basically, what I do, is start from an ignition timing map that I know needs to have timing added to it. I will start out by adding about 2 degrees of total timing at full load, and see if, and where it makes power. Usually it will make more power every where. Continue to do this until it stops making power. Then back it off 2 degrees. Also, listen VERY CAREFULLY for knock. ESPECIALLY AROUND PEAK TORQUE!!! Knock is most likely to occur at peak torque. Sometimes you have to pull the timing back around peak torque, and then bring it back up afterwards. What you may also find, is that after you've ramped the ignition back up after peak torque, you may have to start advancing the timing again around 6K and ramp it up as the RPM's increase. This is happens to some motors. If you're motor likes it, then so be it. If not, then that works too.

Alright, for now, that is a nice, safe, map that will get you down the road and not blow anything up. When we start tuning for peak power, turning up the boost, and other changes, I'll go into more detail about what to do, and what's actually happening inside the combustion chamber.

Awesome write up! Stickied.

ballin. i was looking to start doing my own tuning. this basic shakedown setup helped my understanding exponentially already. now i can go open up my 20 page file on tuning and maybe have some direction lol.

this is awesome man, keep it coming.

excellent, now to find one for E85 tuning !

E85 tuning is pretty simple. Just some basic things that are different than gasoline. If you're interested, I could do a writeup about that as well.

I dont like how it says to start with 12:1. Your starting and finishing idle/cruise/driving targets need to be around 14.5:1 no lower than 14's if you want any kind of fuel mileage and clean plugs. My driving a/f ratio is about 15.2:1 bouncing around 15.5:1 and as low as 14.9:1... stay as far from the 13's as you can until around 3" of vacuum on the sr20det motor, especially stock compression ratio engines. Once you hit 3" of vacuum you can gradually dip into the low 14's, 13.8's and 13.5's as you near 0psi. Once you pass boost threshold its okay to see 13.3:1 and gradually dip into the 12.7:1 as you pass 7psi. there is no reason to use 12:1 until you get beyond 7psi+

heres a log from years ago. I do better than this now that I have more experience, but this is a good idea of what I am saying.
10000 is 0psi
20000 is 14psi
Notice I dont touch 14.1:1 until around boost threshold (0psi), and also that we lower the a/f slightly on the way there (you see 14.3's~ leading up to that region) if you drive an OEM vehicle with the OEM computer you will see the same exact thing. Also note that at lower rpms the a/f does touch the 13's near 0psi, this is to assist throttle response (snappy crisp engine revs), those areas are commonly hit rapidly right off idle when you depress the throttle suddenly.



this motor had a T04E 50 trim and made 350rwhp at 14psi, I have a video of the car on the dyno as well


here is the final overlay of that engine with 2 different camshaft profiles and 2 different turbocharger compressor wheels.

I said you were aiming for 12:1 at WOT. I didn't address part throttle tuning.

it says, quote,

float_6969 wrote: "First thing is to get the motor idling and up to NOT. Unless you're using a stock ECU, or a standalone that allows for closed loop at idle, you want your AFR'S to be around 12:1."

You should re-word it to say 14.5:1 at least, or even 14.9:1 .

Also, Discussion of volumetric efficiency is part of tuning, a stock engine at 14psi of boost would be fine with 12.8:1 whereas a built motor at 14psi will produce an extra 100+ horsepower and should be around 11.8:1 for instance. discussion of why this happens and what VE is and how to tell where your VE is going to peak and fall is important but more advanced. Also timing areas for highway cruise and part throttle acceleration should be discussed. basically tuning methods is a 600 page book and cannot be covered with a single post. But I see you want to help others so these are suggestions.

My engine will not idle at that AFR. Not even close. I've never seen an engine that won't happily idle at 12:1. In my experiences, unless the engine has a closed loop strategy for idle (ie; it maintains closed loop, alters timing, and controls the idle control valve, and has interrelated maps to control all of this) it will not idle at an AFR that lean. The BSFC it idle is very poor, and so the engine requires more fuel at those revs. Obviously it can be achieved, but not all standalone/piggyback systems are able to accomplish this. I wrote this write up as a VERY basic intro. Something that most people could follow and get the engine running and driving well enough to drive it someplace to have it properly tuned. I PURPOSEFULLY didn't get into things like VE, BSFC, the relationship between AFR's and ignition timing, etc, because, as you said, it would take hundreds of pages to cover it all.

I hope I don't come off as thinking your input isn't welcome, because it is, but I feel that you think this post was supposed to be some sort of highly informative exposé on the intricacies of engine tuning and I feel like I made it obvious from the start that it was the exact opposite of that.

All engines idle at 14.5-14.9 that is what closed loop is

If yours will not, your wideband is wrong or something is wrong with the engine or electronics.

If you idle an engine at 12:1 it will foul the plugs and carbon up the combustion chamber. Very bad idea.
Also it will gradually wear out the piston rings over time, as the excess fuel washes the oil from the cylinder walls.

Most engines will idle fine at 15:1, or even 16:1.

Simply put, you're wrong. My engine ran for 40k miles with an idle AFR of around 12:1 (maybe it was 12.5:1 at the leanest) and I never changed the plugs or had them foul. Also, no carburetor equipped engine idles that lean. Know why? Because it can't idle that lean with out a digital system to control idle speed and ignition timing. If your EMS is equipped for closed loop idle control, then obviously you shouldn't run a rich AFR at idle. I can also tell you than ALL vehicles that don't have a heated O2 sensor idle rich. The KA24E and CA18DET are two examples off the top of my head that I have first hand experience with not idling in closed loop. They may TRY to idle in closed loop, but they won't usually be able too because the O2 sensor doesn't stay hot enough to work properly at idle.

float_6969 wrote:Simply put, you're wrong. My engine ran for 40k miles with an idle AFR of around 12:1 (maybe it was 12.5:1 at the leanest) and I never changed the plugs or had them foul. Also, no carburetor equipped engine idles that lean. Know why? Because it can't idle that lean with out a digital system to control idle speed and ignition timing. If your EMS is equipped for closed loop idle control, then obviously you shouldn't run a rich AFR at idle. I can also tell you than ALL vehicles that don't have a heated O2 sensor idle rich. The KA24E and CA18DET are two examples off the top of my head that I have first hand experience with not idling in closed loop. They may TRY to idle in closed loop, but they won't usually be able too because the O2 sensor doesn't stay hot enough to work properly at idle.

I've tuned several carburetors and always managed to hold 14.5:1. They will idle at 15.5:1 though if you try.

I think you are missing the point here. 12:1 is wide open throttle, balls to the wall air fuel ratio. Not an idle number. No factory car ever produced, ever, in the history of man-kind, since 1970's, has been tuned to run 12:1 at idle, nor should it be. You don't need an O2 sensor or closed loop to get close to that number, I run most of my cars in open loop to maintain a 15.2:1 cruise ratio, to save gas and clean the plugs. I think you had better do some research and come back later.

I think you're missing my point somehow. I'm not saying 12:1 is an ideal AFR to idle at. It's a a safe place to start from. All vehicles will idle happily at that AFR. You can lean it out from there until you have issues with idle stability. Every engine is different and there are a LOT of variables. I know it seems unfathomable to you, but not all engines will idle that lean without O2 and idle control feedback loops. And from experience, none of the Nissan ECCS systems will idle in closed loop with a single wire O2 sensor. Once the O2 sensor cools off, they go rich. Probably not 12:1 rich, but IIRC it was around 13:1.

As for part throttle, I run E85, and my wideband is calibrated for gasoline, but I had no issues running what read as a 16:1 AFR. I'm sure I could get it leaner, but the engine failed from a bad oil filter before I could tune it more. I also don't run closed loop at all as I don't have emissions testing in my state.

And just to TRIPLE iterate, 12:1 isn't the ideal AFR at all loads and RPMs. I never said it was. My point was that is was a safe place to start.

float_6969 wrote:but not all engines will idle that lean without O2 and idle control feedback loops. And from experience, none of the Nissan ECCS systems will idle in closed loop with a single wire O2 sensor. Once the O2 sensor cools off, they go rich. Probably not 12:1 rich, but IIRC it was around 13:1.

There is no difference between a person sitting there with a laptop adjusting pulsewidth, and letting the computer do it with closed loop. There is nothing magic about closed loop that suddenly allows the engine to idle at a proper stoichiometric air fuel ratio, such as 14.7:1

I am glad you do not see 12:1 as an idle ratio, but I dont feel that is a proper place to start either. I never want my 2.0L sr20det at 12:1 unless it is making 350+ horsepower. That is just a blatant waste of fuel, there is no reason any engine, unless its the biggest baddest large port cammed out huge injector engine to need that kind of idle air fuel ratio. And even then its a huge waste. Running rich is just to keep the motor healthy when making power, thats it, the end.

Your post makes it sound like 12:1 is where to be for idle characteristic. Well of course the idle will smooth out at 12:1, it will also be smooth at 11:1 and 10:1 in most cases. You can't say that 10:1 is a good place to start just because the engine will idle smooth there. I think 14:1 is a "good place to start" and lean it out from there.

Something else i noticed, I am not picking on you but I advise you check this video for proof of what i am about to say,



The phenomenon you describe here,

And from experience, none of the Nissan ECCS systems will idle in closed loop with a single wire O2 sensor. Once the O2 sensor cools off, they go rich. Probably not 12:1 rich, but IIRC it was around 13:1

Has nothing to do with the 1-wire sensor. As you can see in my video, the factory ECU defaults to a richer air fuel ratio as standard procedure. The O2 sensor being used in that video is a wideband, I used the analog output to simulate a narrowband to maintain a 15.2:1 air fuel ratio for cruise situations. The wideband never "cools off" yet the factory ECU still defaults to a 13.8-14.1 air fuel ratio regardless of whether the sensor is working or not. Its a factory feature for sr20det, and other, Nissan engines.

float_6969 wrote:First thing is to get the motor idling and up to NOT. Unless you're using a stock ECU, or a standalone that allows for closed loop at idle, you want your AFR'S to be around 12:1. This will vary for different motors, so just treat that as a starting point.

I'm tired of repeating myself. I don't know what it is about those sentences that is sooooo hard for you to accept. IMHO (opinion being the key word here), 12:1 is a good place to start from. I've never seen an engine that won't idle there. That's where I like to START. From there I lean it out until I have idle issue, and then richen it back up.

Clearly you have a different OPINION. That's fine. What I don't understand is your insistence upon changing my opinion. Why is that so important to you that I agree with you? I don't know you. You're a random dude on the internet. The vice versus is true for me.

kingtal0n - you're taking segments of float's post and choosing to take them out of context to make an argument against what he's posted, and when you take them out of context, you're missing the big picture of what he's illustrating.

Tuning rich is known to be "safe" to establish a baseline, and then you lean out to optimize points in the map from there. That's all I'm getting from float's post - it's explained fairly clearly. You're putting the cart in front of the horse with your argument and going down the rabbit hole, thus creating confusion.

This post was designed to be a simple, big-boxed starting point, creating a foundation for basic tuning concepts. I feel you're dissecting for the purpose of dissecting, and it's counterproductive.

What?

He says,

"First thing is to get the motor idling and up to NOT. Unless you're using a stock ECU, or a standalone that allows for closed loop at idle, you want your AFR'S to be around 12:1"

And then goes on to say nothing about leaning it out. There is nothing that says "oh by the way, dont leave your engine idling at 12:1 because no idle of any engine ever produced on planet earth should be at 12:1 for long". It isn't safe to leave an engine that rich, all the time.

It even says,

"Now for the fuel. As with the idle, we're going to aim for about 12:1 at WOT all the way to redline. "

As with the idle? You mean my idle AND WOT should BOTH be 12:1? thats what it says right?

here I made some additions, I hope you dont mind.


OK, now that we understand what all of these words mean, lets move on to actually tuning your engine. All tuning starts with ensuring that the system is working as is should. This means checking that you have adequate sized injectors, a good fuel pressure regulator, proper fuel pressure, a good fuel pump, clean fuel filter, no kinked hoses or lines, and no leaks in the fuel system. Then, we want to make sure the intake system (everything from the back of the MAFS [IF YOU HAVE ONE] to the cylinder head) is sealed and not leaking. Leaks in the intake system cause all kinds of hard to fix problems that make tuning a pain. The path air takes from the filter to the exhaust system is called simply "air path". The best way to determine if your air path is sealed up is to pressurize it using a home-made boost leak checker (insert link here to DIY boost leak checker using PVC and tire valve stem). Pressurize your air path to 15-20PSI and find all the leaks.


Next is the ignition system. MAKE SURE YOUR PLUGS LOOK GOOD AND THE GAP IS SET!!! A word about gap here. The larger the gap the better the performance, however, too large of a gap and spark will blow out when resistance in the cylinder climbs high enough. A spark starts combustion by breaking the bonds between Oxygen atoms, the same way lightning does, which allows the chain reaction of combustion to take place in the presence of an appropriate electron donor such as gasoline or ethanol. It is worth noting that liquid fuel will not participate, in fact liquid gasoline will not burn. It is only the vaporized form of gasoline atoms that participate in combustion. If you light a puddle of gasoline on fire it will not explode suddenly, but rather, burn steadily, as the gasoline molecules gradually evaporate and then burn when they reach oxygen atoms in the air, to produce heat and energy. Higher fuel pressure and better injector nozzles are more likely to give a finely atomized spray which leads to better performance. Spark gap tuning: The way I tune spark gap is to run the plugs with the stock gap and gradually turn up the boost until we blow out the spark. THEN you gap the plugs down. Typically you will need about .028" gap on a 400rwhp sr20det engine using stock ignition system. If you run an MSD or other ignition amplifier you may increase your gap to as large as .055" and this will result with improved performance and economy. This is SOO important. I'm amazed at how often this is overlooked. Check your plugs, check your plugs, check your plugs! Next, if you have them, check the plug wires, cap, rotor, and coil. Now check that the ignition timing at the crank actually matches what's happening at the crank. Once again, this is a very simple step that is often overlooked. If the timing is off +5°, that can easily be the difference between a little knock from too much timing, and a bent rod, or a hole in a piston, or a blown HG from serious detonation. Last, but not least, is the oil. Make sure it's fresh, AND OF THE CORRECT VISCOSITY!!! There is little that will thin oil faster than a few pulls on a dyno.


(Note:I have a personal rule, that I don't do more than 4 pulls without shutting the motor off and letting the coolant and oil cool down for 10-15min or so. If you're REALLY confident in your engine cooling and oil cooling system, this doesn't have to apply, but be careful) Good advice, never run an engine on the dyno back to back several times without a significant cooldown period.

Now that we're confident the motor isn't going to have some mechanical failure, we can start the actual tuning process. I'm not going to get very detailed here, just cover the basics. First thing is to get the motor idling and up to NOT. Unless you're using a stock ECU, or a standalone that allows for closed loop at idle, you may start with your AFR'S around 12:1. This will vary for different motors, so just treat that as a starting point. Once you acheive a stable idle at around 12:1 you will want to lean it out quickly, to around 14.5:1 or leaner. The more lean you run the engine the more efficient it will be, the more heat will be produced, the better economy you will acheive in general. We will also want to adjust the timing so that it gives a stable idle. What you may notice is that as you adjust the timing and fuel, you'll have to re-adjust the the other. This is normal. There is a relationship between timing and what AFR is showing up at your sensor. I'll explain why later. Just give the motor what it wants. It took me a long time to stop questioning why different motors like different things. If it runs well, and it sounds well, and it makes good power, it's right. The books and numbers don't matter. Results matter. It is worth noting at this point that just because an engine starts to idle rough at leaner air fuel ratios does not make it a bad place to be. Some engines with large camshafts will idle smoothly at 14.5:1 and lope at 15.5:1. There is nothing wrong with leaving it at 15.5:1 and letting the engine lope, in fact this is desirable to many individuals. You must remember that the oxygen sensor is reading the oxygen content, not fuel, so an engine with a large camshaft is likely to pass oxygen into the exhaust system during overlap, giving you a false lean reading on your wideband. The same thing happens if one cylinder is misfiring, the wideband will read lean because the misfire is passing un-used oxygen into the exhaust system. So again, results matter. If the engine has HKS 272 cams in it, and lopes steadily and happily along at 16:1 I would leave it there.


Ok, so now you should have the car idling well. First we want to set up a quick timing map. In most systems, you want to start with some sort of base map to work with. Building a timing map from scratch can be excruciating depending on the system. The timing should slowly ramp up from idle to around 30° (If I don't specify, all timing will be given in degrees BTDC) and reach maximum timing around 2500 rpm. Once again, these are just starting points. Your final cruise timing for most vehicles will be about 37* btdc. The process to finely tune ignition timing is given next (advanced):

Advanced timing tuning for best economy:

First clarification about the word average, When I say average I mean when driving the car like a normal daily driver out of boost, with 50% highway commutes.
Now, on to the gory details,
To achieve this kind of economy requires patience to say the least. There are several factors affecting fuel economy on all cars;
First let us tackle the tuning. My average air fuel ratio while cruising is 15.4:1, and I have developed a sort of "checker board hypothesis" whereby the fuel map gradually dips from high 14's (14.9:1) to mid 15's(15.7:1 max) in cruise situations, and to ensure engine longevity the fuel map resolution in those areas has been enhanced (a typical feature of many stand-alone ecu is you can decide what sort of resolution you would like by changing pressure/mass breakpoints) such that a slight movement outside of the cruise range (even just a steep hill while cruise control is set) will drop the air fuels quickly to about 14.5:1 which is much closer to the average closed-loop air fuel ratio you would see when using a narrowband sensor (they tend to flip from 14.3 -> 14.9 quickly). In the past I have used a simulated wideband analog output to keep my ECU in closed loop at these air fuel ratios ( 15.5:1 @ .002volts, 14.9:1 @ 1.002 volts) but I have found open loop to be just as effective when the engine is mostly stock (mainly because of the great vacuum a stock engine will produce, makes each load point more well defined)

Now, all of that is fine and dandy, but it does not have that great of an effect on fuel economy as you might expect. And I have discovered this because I data-log everything for hours of driving for years and years on different cars. The best way I have found to measure fuel economy is by comparing injectors duty cycle, engine vacuum, and road speed all at once. If you also include the injector flow-rate, you can write an algorithm to generate a real-time fuel economy display from this data, but it is un-necessary to simply find out if your changes are saving you gas. The more important tuning aspect of fuel economy is ignition timing. Finding the best timing for your highway cruise at different load points. And here is my method.
Load your car with luggage, full tank of gas, passenger, weight it down as heavy as it can be. This will ensure your load cell is just about as low-vacuum as possible for a highway cruise, this will ensure that if you tune your timing then later on decide to add all of this weight, you do not run outside of your intended cruise load cell and into the part throttle acceleration zone.
Now, set your cruise control to eliminate the movement of the tps to keep the acceleration enrichment out of the picture as much as possible. In my case, I simply disabled my TPS enrichment feature for this tuning session. Cruise along at a speed low enough that wind resistance will not factor in (yet). I usually start at 65MPH. Find your load cell, remember the vehicle is heavy, on my car this cell is right about 10" of vacuum at 65 MPH. Set your timing to a low number, something like 30* that is much too low to be the final result, and drive for 20~ minutes while logging your fuel injector duty cycle and engine vacuum. In my case, injector duty was about 8%. Now, advance your timing. I used 35* next. And repeat the above proceedure. My injector duty cycle dropped from 8% to 7.6% average, and my air fuels became slightly richer in fact, allowing me to remove even more fuel. If I had an EGT gauge I would have also noticed the temperature drop at the exhaust manifold around 50*F~. This is all a very good sign that the additional timing was a welcome change. You can now see where this is going; repeat the proceedure, adding timing and logging fuel injector duty cycle, and look for the signs of a welcome change, that is, reduced injector duty cycle, lower EGT, increased engine vacuum. At some point you will encounter diminishing returns, and then the application of the vehicle will tell you what to do next. For me, safety is number one, so I never run off into the deep end for that extra .2% (it took another 12* BTDC of timing to drop the injector duty only .2% so clearly the additional timing was unwelcome). My final timing is right at 37* btdc for this engine, some have appreciated as much as 45* btdc (big cam(s), big manifolds, large displacement engine usually)

Now, it is important to realize that before you start playing with the engine's tune, there are several other factors to consider when trying to get the best fuel economy, they should be taken care of first.
1. Rolling resistance. Do your brakes drag? grease the backs of your pads. Grease your wheel bearings. Spin your driveshaft by hand and feel it, does it feel rough or notchy? Push your vehicle by hand, often, get a feel for how easily it rolls. Update and maintain all of the aspects of driving straight, such as the alignment, toe and caster. Consider the tire compound.
2. rotating weight. Use the lightest wheels you can find. I also have a light weight flywheel (but not too light!). Anything in your drivetrain you can afford to have lighter is a fuel saving benefit. You do not want the rotating assembly too light on a street car (no knife edged crankshafts) though.
3. ride height / wind resistance. Speaks for itself, is your car suitable for high speeds? Get it lower to the ground if possible.

and finally, the way you drive is very important. use your brakes as little as possible. Every time you brake, you waste the energy that was extracted from the fuel you burnt and send money out the window. Engine braking for long distances pissing everybody off behind you that wants to speed up to the stop light is essential. My car will engine brake with zero fuel input from 60mph roll for about 1/4 mile.
/end timing tuning for best economy



Now for the fuel at WOT. On a turbocharged vehicle, We're going to aim for about 12:1 at WOT all the way to redline. A naturally aspirated engine will tolerate 13:1 or even leaner. Most LS-X engines will run 13.6:1 for instance. It depends heavily how much power per unit displacement you are making. This will probably take a few pulls to even get the car to make it to redline. Watch the AFR'S closely. For right now, if you see anything leaner than 13:1, get out of it. Add some fuel where it leaned out, and any rpm and load point above that an equal PERCENTAGE more. It's important to keep the idea in your head that if you change the number at a given load point by "5", you can't just add "5" everywhere above that. You need to find out what percentage change "5" was for that load point, and apply that change to every load point above that. Most standalones will let you do this easily. If they don't, it will just take a little longer to do the tuning. Once you've got the car capable of making a pull all the way to redline, start trying to get the AFR'S evened out so that your AFR'S look like a line around 12:1 all the way to red line. For now, we're done. There is more we can do with fuel, but for now, lets move on to timing.

The timing is a bit more time consuming, and you have to be careful here, especially if you're on pump gas. (excluding E85 and other alcohols, that is a "whole 'nother can o' worms", as they say)Basically, what I do, is start from an ignition timing map that I know needs to have timing added to it. I will start out by adding about 2 degrees of total timing at full load, and see if, and where it makes power. Usually it will make more torque every where. Continue to do this until it stops giving back SIGNIFICANT increases in torque. Then back it off 2 degrees. Also, listen VERY CAREFULLY for knock (if you can. Most exhaust systems will drown out any knock). ESPECIALLY AROUND PEAK TORQUE!!! (watch your knock sensor and look at the torque graph. If it starts getting jagged peaks and valleys that is another sign of too much timing. Always use Smoothing:0 when tuning on a dyno.) (insert example photo of a jagged torque from too much timing). Knock is most likely to occur at peak torque, because that is when cylinder pressure is highest and octane is the weakest link. Sometimes (almost always) you have to pull the timing back around peak torque, and then bring it back up afterwards. What you may also find, is that after you've ramped the ignition back up after peak torque, you may have to start advancing the timing again around 6K and ramp it up as the RPM's increase. This is happens to some motors. If you're motor likes it, then so be it. If not, then that works too. Most SR20DET engines will be happy around 9* of timing through peak torque on a given 280rwhp engine with mostly stock components, leading up to about 12* of timing by 7000rpm. Rarely on pump gas will any sr20det engine require more than 12* of timing anywhere during WOT, unless your boost is ultra low, say 4psi. always start tuning timing with the lowest boost you can, for me this is 0psi, you disconnect the wastegate arm so the flapper just hangs open and the engine will not build boost. This way you can tune the engine's 0psi area through WOT, which would be impossible otherwise. You will want as much as 15-18* in this area (NO BOOST). Once you re-enable the wastegate arm and build boost, usually you are stuck with 7psi minimum, and I recommend starting with 12* and making a pass, then adding 3* for a total of 15* and making another pass at 7psi just to see for yourself what the engine does. It should not pick up much more than 7 horsepower. Remember that anytime you add timing, it will always give you more torque and power somewhere, even if the timing is dangerous. It is important to realize that additional timing will almost always yield improved torque output (you are beginning to spike the cylinder pressure, which will generate more torque, but it will also hammer the rod bearings and put strain on the head gasket). That is why we tune for SIGNIFICANT increases in torque, like a gain of 15-20+ for an additional 2* of timing advance input.

Alright, for now, that is a nice, safe, map that will get you down the road and not blow anything up. When we start tuning for peak power, turning up the boost, and other changes, I'll go into more detail about what to do, and what's actually happening inside the combustion chamber.[/quote]

Timing example

Here is an example of a 2jz-gte I tuned, using the procedure outlined above to find the best timing for wide open throttle.




BLUE LINE:
This was my final tune, the 5th pass on the dyno I knew this was where I wanted to be from experience. As a general rule we want to make 10 or fewer passes on a dyno day to preserve the life of the engine. Here at this blue line, timing is about 12* BTDC across the board WOT.

RED LINE:

I added 2* across the board for a total of 14* BTDC timing.
What do you see?
First notice we picked up torque before peak torque, and lost power after peak torque. This is quite typical of 2jz engines that run too much timing.
The additional torque before peak torque is there because the cylinder pressure is beginning to spike, this is a bad thing for the engine because it means we are stressing the head gasket and rod bearings. That is why the torque appears to come and go in spurts, you see it sort of meander up and then down, and then up again? The timing is on the borderline for these conditions, borderline to being dangerous. And the drop in power across the board seals the deal. The engine did not want 2* of extra timing. Also notice how much more jagged the graph appears than the other runs.


Green line:

I removed 3* of timing for a total of 9* BTDC across the board.
what do you see?

Notice a massive drop in torque, and slower spool. Yet it STILL makes more power than the red line which has too much timing. Different engines react differently, but this 2jz clearly desired between 11-12* BTDC and not a penny more or less with this combination.

Running rich at idle is a good way to compensate for poor timing (ignition and valve), as well as compensating for big cams. You can get your timing squared away and lean out from there, or leave it and not really care. 12:1 really isn't THAT rich.

Also don't forget about cold start enrichment. You might start at 12:1 when the engine is cold and slowly start leaning it out to around 14.7:1 when engine is at normal operating temperature. And make sure you do all of your tuning once the engine has reached normal operating temperature.

the air/fuel ratio gauge on my 95 240sx ka was saying 16.8 at 75 miles an hour on the freeway, is this harmful to the motor? Its supposed to be built with rods and bearings pistons etc. I just bought it and its my first turbo charged car, and this is my first post so hi everybody and any help appreciated.

Do you know what type of O2 sensor it is, and gauge? Do you know how old the O2 sensor is/if it has ever been calibrated?
Does it read normally the rest of the time? Did it stay at 16.8, or did it just do that when you backed off the throttle or something?
If you're worried and want some quick feedback, you can pull your plugs and see if they look like your engine has really been running that lean.

Sweet post! I'm totally new to tuning.

I own a 2002 Q45, with the VK45DE engine. It's a great engine, making 340 HP factory. It came with OEM forged internals, and extremely durable pistons. There was a dealership in Beverly Hills, called Keuylian, that was selling supercharged '02 Q45's that with approximately 7.5 PSI was making 440 HP. With an aftermarket exhaust added, 540 HP. This setup was using an air-to-water screw type supercharger installed where the intake was.









I want to reproduce these numbers. Or at least, get up to 500 HP. That would be enough for me. I've read that the internals will support the power. I have not read any information on upgrading injectors, coil packs, etc. What I want to do is, add a pro-charger, inter-cooler, bigger race quality radiator, aftermarket exhaust, and flash tune the ECU. What I've learned is there is no piggyback device that will work for me.

What are some thoughts from some of you all with more experience tuning Nissan/Infiniti setups?

All the best,
~HollywoodJackson~

For that much gain, you'll need larger fuel injectors and therefore something to control them (like ECU reflash like you mentioned).
I'm not as familiar with that platform, but most Nissan fuel pumps suck, so you'll probably need to upgrade that as well. I can't imagine you'd need coil packs. I'm not sure how much the trans holds up to either...

Great read!!!

Thanks!