Tuning Guide

[mike300zxt]

I noticed there are a lot of AFR and tuning questions in the forums, but no tuning guide/FAQ, so I thought I'd start one. This isn't meant to be a DIY guide, but just a thread to share tips and experience. I've had the chance to learn a lot from various tuners over the years, and I’ve helped build a fast GT-R or two, so I thought I'd share a few insights.

Disclaimer: This isn't meant to help you tune you car on your own, it's simply to give you an overview of how a car is tuned. There are many specific issues that may affect your specific setup, so talk to a qualified tuner.

Those with first-hand knowledge and experience, please feel free to add/edit/correct this information as this is mostly off the top of my head.

”It’s not running right, it needs a tune.”
I always hear people say that, but does it? Tunes don’t change. If your car is not running right, then something is wrong and you need to figure out why and fix it before tuning it. You can't tune out mechanical issues! If you think it's running rich of lean, figure out why. Which leads us to the 6Ps…

The 6Ps
[u]Proper Preparation Prevents Piss Poor Performance[u]. I’m borrowing this one from the 300ZX (Z32) world courtesy of Ash. It really applies to any turbo Nissan. (http://www.twinturbo.net/nissan/300z...ormancegt.html)

What this means is, you can't just show up at the dyno and expect to make power. Especially on an older car, you need to make sure that it's ready to be tuned. There are several steps to this.

Check and replace your plugs. I usually go with NGK Irridium XI for Zs/Skylines/Gs/Zs and even R35s. At least NGK something! Save the economy plugs for your winter beater. Make sure they are gapped correctly for the boost you want to run, and that they are the correct heat range. More boost requires a smaller than stock gap, and also a colder heat range plug. Ask if you're not sure what plug/gap to use. Change them at least every 1-2 years…I don’t care if they are long-life, old plugs will cause you to lose power after a year or 2. If your car doesn’t pull smooth and hard under boost, old/worn/wrong plugs are often the cause.

Timing. Check and set your timing to the factory spec. Note that many Nissan models require putting the car into base-timing mode before checking or setting timing because the ECU can change timing on the fly at idle. Check your service manual for how to do it properly, and for the spec (some engines are 15degrees BTDC, and others are 20). On older models, your CAS should typically be set roughly in the middle of it’s range. If it’s off to one side, either you set it wrong, or your timing belt is off a tooth.

Intake system. Turbo cars use an air-tight intake system. Or at least that’s the idea. If your car is 10-20 years old, you probably have vacuum/boost leaks. These can cause issues with everything from AFRs (Air Fuel Ratio) to laggy boost to lack of power. If you have access to compressed air, remove your air filters and pressurize your whole intake to 6PSI MAX (NO MORE). If it won’t hold 6PSI, find and fix any leaks. Replace old vacuum lines, replace loose worm-gear clamps, check your turbo and IC piping for leaks.
Filters. Air filter and fuel filter. Clean, check, replace. If you don’t know when you last changed your fuel filter, change it.

Fuel system. If you’re running more than stock boost, realize that you may need larger fuel injectors and a larger fuel pump. More air volume requires more fuel. If you don’t have enough fuel, you will run lean, which can cause excessive heat and engine damage. We’ll talk about monitoring fuel during tuning below.
Boost controllers. If you’re going for more than stock boost, get a proper dual solenoid controller. If you have a single solenoid Greddy/APEXi and want to run much over a bar, toss it in the trash and buy a dual solenoid Blitz/HKS unit. They cost $$$, but you can’t buy cheaper power than a boost controller that gives you faster boost response and holds peak boost properly without spiking.

Compression Test. If you’re going for big power, don’t bother unless you know your engine has solid compression. On turbo cars, it can be hard to tell when compression is low because the turbos keep pushing. But pushing an engine with weak compression is just going to push it over the edge.

Fuel Pressure. Turbo Nissans use a rising rate fuel pressure regulator. What this means is that for each 1psi of boost pressure, the fuel pressure also rises 1psi. You can use a 100psi fuel pressure gauge to check that fuel pressure rises under boost.

A wideband AFR sensor and gauge is required for tuning. Most dynos will have one, but if you are tuning on the street, you will need to install one since you can’t tune safely without one. Innovate widebands have proven to be the most accurate.

Trouble Codes. Check for fault codes or sensor failures. On older models, the computer only checks for a complete failure of a sensor circuit, it doesn’t check for valid information from the sensors. A lot can be wrong without the check engine light coming on. Ideally, you can use a consult program to monitor sensor readings, or use the service manual to manually check values with an ohm meter.

Turbos. If you have upgraded turbos, keep in mind that running 14.7psi/1bar on larger turbos is not the same as running 1bar on stock turbos. A larger turbo can push more air (CFM) at a given pressure than a smaller turbo can, which means when you change to larger turbos, you need to adjust your fuel system and tune to provide more fuel. A lot of people think 1bar=1bar no matter what the turbo, and they forget that it’s the airflow volume that matters, not the boost level. More air simply requires more fuel!


Tuning Overview:
When you're tuning a turbo-charged car, there are several things to be aware of. Achieving maximum power is a matter of balancing engine compression ratio, fuel octane, boost level, timing, EGTs (Exhaust Gas Temp), AFRs, etc. While you need to be conscious of how much power your engine can physically withstand, it’s just as important to understand how to prevent detonation, which can kill even the toughest engine.

Normally, fuel burns in a controlled and expected manner within your engine. But when pressure/temperature exceed a certain point, the fuel can detonate, or instantaneously explode. This can cause extreme heat and stress on internal engine parts, and can lead to pitted or broken pistons, flattened bearings, or even total engine failure. If you don’t understand how to detect detonation, do a lot of research before you start tuning.


Detecting Detonation
Bad detonation can often be detected audibly as a faint knock, tick or rattle under boost, but even inaudible detonation can do damage. Most dynos will have a detonation mic and amplifier, and there are also electronic detonation monitors you can buy. Other hints of detonation can include un-even acceleration or power (as detonation is a miss-fire), or short puffs of smoke from the exhaust under full-throttle acceleration. If you are driving the car, the easiest way to hear detonation is to boost beside a concrete wall with the window down. You will hear the sound echo off the wall.

Long story short, you never want to hear detonation, so you need to tune to prevent it, which we’ll get into below. Detonation is also the reason that many engines have low compression. If you simple turn up the boost without proper preparation and tuning, you risk engine damage.

[mike300zxt]

Types of Fuel:
The type of fuel you have access to affects how much boost you can run, and how much timing you can run on your tune, which leads to how much power you can make safely.

Race Gas (up to 120 octane) – available in different octanes, generally lets you run the most boost and timing without fear of detonation. Quite simply, race gas is awesome, and is generally the safest way to push extreme power!

Pump Gas (usually up to 94 octane depending where you live) – The higher the octane, the more detonation resistant the gas. 16-18PSI (1.1-1.2bar) is typically the max on pump gas. Larger cams may lower your compression ratio which might let you run more boost. Larger turbos also run cooler than smaller turbos, and larger ICs (intercoolers) will also let you run a little more boost…ass long as your fuel system and tune can supply enough fuel. Husky/Mohawk carry 94 octane with 20% ethanol. See E85 for the good/bad of ethanol.

E85 (100-105 octane) is a fuel that is 85% ethanol. Easy to find in the US, not so easy to get here. While it’s very detonation resistant, it also has a much lower power/volume ratio than standard pump gas (like 25% less) or race gas. E85 will let you run more extreme amounts of boost and timing advance, but a lot more fuel is required to make power than with pump gas or race gas. This is exasperated by the fact that E85 needs to run richer AFRs than pump gas. You will need a big fuel pump, and huge injectors to make serious power with E85. You should also be aware that not all older fuel system components are compatible with alcohol fuels. Ethanol is slightly acidic, and early-model NISMO injectors on the Z32 are one example of fuel system parts not compatible with Ethanol. Long story short, do some research before using E85 to make sure that your fuel pump, filter, fuel lines, fittings, injectors and FPR are all compatible with Ethanol.

Water/Methanol Injection – It’s like cheap race gas! By using a water/methanol injection system (from SNOW/Cooling Mist/AEM/etc), you can effectively raise the octane rating of pump gas, while also cooling the intake charge and cleaning the engine. This equates to higher detonation resistance, and typically means you can run 6-8PSI more boost than you could on pump gas alone. The benefit over E85 is that methanol is easy to find at any home hardware store, auto parts shop, or Canadian tire. And because it uses its own injection system, you don’t have to worry about it being compatible with your fuel system. Like E85, effective use of Water/Meth injection requires proper tuning. It’s also a good idea to go with a system that can detect flow problems and cut boost if such problems occur.


Dyno Tuning!
By now, you’ve noticed there is a lot to think about before tuning! We haven’t even talked much about engine or bolt on upgrades, but that’s something better left to the model-specific tech forums. So before you tune, make sure you know what the safe power levels and target boost is for your current engine.

If you’re thinking about tuning for power on the street, forget about it. Beside the obvious safety issues of doing repeated 200Kph 4th gear runs on the street, a dyno is the only way to properly measure and tune power safely.

So lets get to tuning, specifically, I’m talking about WOT (Wide Open Throttle) tuning, or “power pulls”.

We start at a moderate and safe boost level, and gradually increase boost while adjusting AFRs (air fuel ratio) and then adding ignition timing.


Target AFR at WOT:
At WOT, you generally want to head towards 11.2:1 at WOT under boost with pump gas. This keeps things cool and safe, while making good power. If a car runs hot (i.e. High EGTs which can come from high boost/small turbo, or intake/exhaust/head restrictions), the tuner may make it a little richer (11.1 or 11.0). Depending on the type of fuel (or combination of fuels), your target AFRs may be different than they would be on pump gas. Not all fuels are the same!

At lower RPM/low boost, AFRs can be leaner. With pump gas, typically 13:1, and they richen to 11.2:1 as the car builds boost. We can get away with being leaner because until we make enough boost, the intake air is cool, and the engine is much less prone to detonation. At the same time, we can often add more timing at lower RPM. Being leaner before boost or at low boost builds more power and heat which improves turbo response (turbo is spooled by difference in air pressure/volume/heat between the head and the turbo outlet). Less lag, more power sooner! This is especially important on cars with larger turbos. With small turbos that spool fast, you may need to get rich quicker and avoid adding too much timing at low RPM to keep EGTs down.

As the car goes into boost, AFRs are brought to around 11.2:1. When the car runs happily at a boost level with the right AFR, the tuner will try adding more timing. As long as adding more timing adds more power, and there is no sign of detonation, you’re safe. When you add timing and you don’t get more power, that’s when you stop adding more timing.


If you get detonation:
If you get detonation during a dyno run, immediately back off the gas. You have reached the detonation threshold of the engine at that boost level with that type of fuel. You either need to reduce the boost, or reduce the timing advance and add more fuel (if you are too lean). You should have a safety margin of a few PSI of boost, or a few degrees of timing below the point where detonation occurs.

The engine will typically be the most prone to detonation when it hits its peak boost or peak torque as that is when it is the most stressed. When you find your safe torque peak, you may still find that you are able to add more timing at RPM below and above the torque peak to get more power before and after the torque peak.

When tuning with water/methanol injection, you might find that you are running too rich under boost. This is because the methanol is a combustible fuel, so in some parts of your tune, you may need to reduce fuel.

When everything is done right, you should end up with a car that makes good reliable power, and a dyno sheet that proves you’re not just another pretty skyline!


MAF tuning vs. MAP tuning
Stock, Nissan’s use a MAF (Mass Airflow Sensor) to measure the air coming into the engine. While this works ok in stock form, the stock MAF can only read so much air, and tends to become inaccurate on cars with larger turbos that sometimes experience turbo shuffling (air reversing through one turbo, then the other).

Many modern tuning systems use a MAP (Manifold Absolute Pressure) sensor to measure the actual air pressure in the intake manifold. This system tends to be more reliable, and is also less susceptible to the inaccuracies caused by boost leaks.


Choosing a tuning system
There are many tuning systems to choose from. Typically the cheapest and least reliable are piggy-back systems that intercept signals and over-ride the stock computer.

Next up is Nistune, which can be used to tune the factory computer, and works well for cars with minor to moderate upgrades. Nistune uses the stock MAF sensors.

A MAP-based stand-alone tuning system like the APEXi d-jetro, or similar systems from Wolf/Haltec/ViPec/etc offer the most flexibility and tuneability by bringing more modern tuning features to our older cars. These systems are ideal for moderate to extreme builds. Most modern systems will more than meet your needs, some tuners just have their individual preference.


Conclusion
So that’s a rough overview of tuning. There is certainly a lot more to know, but the key points are:
- Educate yourself! Don’t bother with tuning until your car is properly ready (the 6P’s).
- Slowly work your boost up bit by bit.
- Adjust your AFRs as you go, making sure they stay safe and rich.
- Slowly add timing as the engine responds by making more power.
- Be conscious of any signs of detonation, and back the boost or timing down to a safe level if detonation occurs.
- If the car isn’t running right, get off the dyno and go back to the 6Ps. You can’t tune-out a mechanical issue.
- Only a dyno can tell you if you have a 300HP car, a 600HP car, or a 1000HP car!


Anyone want to add a section on tuning cam gears?

[louis110]

Great post. This should be stickied.

[Zacho]

Check the bolded stuff

Fuel system. If you’re going for more than stock boost, get a proper dual solenoid controller. If you have a single solenoid Greddy/APEXi and want to run much over a bar, toss it in the trash and buy a dual solenoid Blitz/HKS unit. They cost $$$, but you can’t buy cheaper power than a boost controller that gives you faster boost response and holds peak boost properly without spiking.

Dual solenoids have advantages, but NOT enough to throw out a single. In my experimentation I have found the second solenoid usually just acts as a vent. The solenoid itself won't cause spiking but what is controlling it (settings on unit) or wastegate exhaust flow issues.

If you ask me, a 3 port MAC solenoid for $25-40 controlled in open or closed loop by a standalone is unbeatable in almost all applications except the extremes.


Detonation is also the reason that many engines have low compression.

Can you share your thoughts/thinking on this?

Nice post. Some of it is very general, but I'm pretty sure that was your intention. I think the best advice you gave is to educate yourself. If you go adjusting settings on the ecu willy nilly without knowing what they do/change/cause/effect you are just asking for engine damage. There was no discussion of MBT(a key tuning idea in my eyes), but that is specifics I guess.

[GTR-Dad]

Mike,
Good job covering key factors without blowing smoke!
The toughest thing about Internet forums is sorting out the BS from the good advice. The post above is consistent with everything I know about tuning, and is easy to read as well!
Stickied!
Cheers,
Dan

[archaeic_bloke]

Boost controllers. If you’re going for more than stock boost, get a proper dual solenoid controller. If you have a single solenoid Greddy/APEXi and want to run much over a bar, toss it in the trash and buy a dual solenoid Blitz/HKS unit. They cost $$$, but you can’t buy cheaper power than a boost controller that gives you faster boost response and holds peak boost properly without spiking.

I've been saying this very same thing on these forums for months, and received nothing but greif about using a profec B... I held out until i found a good dual solenoid, I picked up a BLITZ SBC Spec R finally.

arent you the tuner who used to work at Z-tune in BC?

great write up mike, appreciate you sharing your knowledge!

[M13]

Mike was one of the owners of Ztune.


Thanks Mike, your tune has been great for my little 2 Litre!

I've changed a few things and am planning to retune before Spring.


Great read also.

[LIGHTSPD]

Thanks for not trying to confuse people with the usual crap about Stoich values changing etc and recalibrating AFR etc. Just nice and clean.

Cheers Cam

[Dragon Humper]

This is good for the Newbs who show up to a Dyno Day with their car in a sorry state and expect miracles.......


One thing I would like to point out though is you should never, EVER retune for Water/Meth injection to correct a rich condition while you are using the spray. If you lean out your tune to compansate for the added fuel from the Meth you are only asking for trouble when the Meth tank runs out. I don't care if you have a failsafe in place to prevent you from going into high boost without it, it's just a very bad idea. Your failsafe could fail, Murphy's Law rules.

It's best to tune to a certain level of boost with race fuel to perfect your AFR's and timing map, then switch to pump fuel. Run the car up to the max boost with the pump fuel, then back off .1 bar from the first sign of det. to set the NON-Meth boost level. Turn on the Meth kit and let her go to the max boost level with the race fuel to make sure the Meth flow rate is good enough to stave off det. I wouldn't mess with the fuel tune, a 50/50 mix of Meth and water won't drop the AFR very much but it will virtually kill any and all det. even with a very aggressive timing curve. The more aggressive timing curve with the race fuel (but used with the pump fuel) at the lower boost level will make the car much more responsive and fun to drive, boost will come up quicker and the off boost torque will be much better for guys with larger turbos and a touch of lag.

All I am using is a 10% Ethanol, 10% Methanol, 10% Tolulene mix in my fuel (94 octane) and I can run 32 deg. of total ign. timing at 1.4bar with no knock, it works very, very well........so well that I don't even change the fuel tune with the added alcohol to drop the AFR's back down to where they were with straight gas, 11.8 to 12.1 is just fine. That's the power of alcohol as a fuel, you can run it much leaner than you think and still be safe. You can also be pig rich and it won't affect power output much as it has oxygen in it to keep the fires burning.........So there is really no such thing as too rich with E85 or Meth (well there is, but it's freaking rediculous) so you don't even have to worry about it.

I have been using 10% Ethanol and up to 15% Methanol (when it's really hot out) in my fuel for 2 years now and have had no issues whatsoever with my fuel system. I don't leave the Methanol in the fuel over winter but I will leave the Ethanol in there with no worries. Any vehicle made after about 1986 can handle alcohol just fine, NADM, JDM, EDM........

The Irridium plug thing is a little unessissary as well, they cost ALOT and won't make you any more power than a really good and cold copper plug. In fact you might just make a little more power with the copper because they will handle more heat than a Plat./Irrid. and let you get a little more aggerssive with your tune before they start to "glo-plug" and give you det. like the more expensive plugs will. Leave those to your Corrolla so you don't have to change them for 160,000km.


NOTE:

*I should point out though, after my input, that a "tuner" will be VERY conservative on your tune. The last thing he wants is for you to be stupid and run your car hard when it's hot with a tankfull of "Costco" gas because that was all that was open at the time. Your car, with an oil puddle under it in his parkinglot at 7am Monday morning is not a heartwarming sight. With a "crisp" tune comes some common sense responsibilities. You can't be a boob.*



Jon.

[GTR-Dad]

With a "crisp" tune comes some common sense responsibilities. You can't be a boob.*

Quoted for truth!

Thx for the whole post that reflects real life experience.

Dan