once you get goin, rent a dyno for a couple hours. thats the only way you'll ever learn what adjustments really do. street tuning via logs is painfully slow and is only good for making large changes.

the have the the perfect dyno, its cheap and close to you as well
http://www.sixsigmadyno.com/services/

 

You'll see the same terminology with NIStune, although it's referred to as the injection multiplier in the software and "K" in the community.

 

On a whim a while back, I looked into buying a hydraulic lift for the car so that I could stop using jack stands. I was pleasantly surprised to find out that I can get something nice for between 1k-2k. Not a bad investment to keep a car from falling off a stand while you're under it one day.

Buy Lift FTW

So, with your post i mind, I decided to look into the same thing for dyno time. Big difference, eh?

At 20k-30k initial purchase, it would take 400-600 dyno runs (@$50ea) or 40-60 full day rentals (@$500) from renting dyno time just to recover the purchase price. And that isn't counting any ongoing maintenance. Add in that you really need a qualified tuner on staff so that you can bring in the business… No wonder there aren't shops with a dyno around every corner.

Rent Dyno Time FTW

Thanks for the advice. I'm just including the info above as one of the things that I learned today. :-)

 

Awesome thread. I will definitely be reading here as well as giving any information that I gain as well. Tuning is something I would really like to learn, even just for my own use.

 

Yea there are a few things that are more specific to one ECU or another. K is actually very simple... it's just a multiplier/constant for the final fuel calculation. For example, doubling the K will double the fuel delivery for your entire map. Typically after dialing in all the constants, you start off adjusting K so the damn thing will at least run... oh and another thing is that lowering the K won't always work if you hit the injector minimum...gotta make sure you dial in the injectors correctly (if aftermarket) first thing

 

Before Logging/Tuning Basics
-----------------------------------------
Your vehicle must be working properly with ZERO issues in order to tune effectively.
You do not "tune" to resolve issues - that is what diagnostics & troubleshooting is for.
The minimum checklist before tuning:
- Sparkplugs: Must be in good condition. Preferably replaced. Correct heat range for NA. 1 range colder for FI.
- MAF: Element must be clean.
- Fuel pump/filter: Do a fuel pressure/flow check. At a minimum do a baseline run and check AFR.
- Ignition Timing: Check with a timing light. Don't trust the value in software, confirm it.
- TPS: Make sure "TPS close" comes on when idling
- Fuel: Need fresh fuel that hasn't been sitting. Full tank. Preferred that you always stay loyal to the same station/brand and octane.
- Codes: You should not be throwing any new codes
- Drivability: Your car should be driving well before the tune. If not, you need a full diagnostic done and need to resolve the issue before tuning.
- Clear the learned fuel settings so that you are running as close as possible to the tune itself.

 

IMO street tuning is a very necessary part of nailing down your tune. Dynos are great for the high power portion of your tune but aren't neccesary (or even practical sometimes) for dialing in low load and long term trims -- the area of the tune where you are in most of the time.

Rather than sift through logs I wrote some scripts that parse hours of my driving logs and 1/4 mile runs and suggest subtle (or even larger) changes... it's worked very well. After getting my low load dialed in and boost A/F's to a safe (rich) spot, I went to the 1/4 track last weekend to get my boost A/F's nailed down and get a sanity check on the overall power based on trap speeds... more fun and way cheaper than a dyno. Took only a couple runs to get it right where I wanted it.

The only reason I would need a dyno is for the 'moar power' ****, which I'm not to interested in to be honest. I've got knock headphones so I can tell I'm already close to my peak power for a given boost level and my trap speeds confirm it.

 

Injection Multiplier "K"
-------------------------------
Nissan ECU tuning first involves adjusting the Injection Multiplier "K Constant" to get mixtures roughly correct.
Then you adjust the fuel and ignition maps to obtain the correct mixtures and timing throughout all of the RPM and load points.
If you are running standard injectors and MAF, the K constant is rarely adjusted and most tuning is just done with the fuel/ign maps. However, if you are FI or have changed your injectors/MAF, you will start tuning with the K constant adjustment first.

 

Once I get to that point, I may need some guidance on how you went about building these scripts. I'm assuming that you have something written to identify sudden shifts/differences in the data or items falling outside of your preferred ranges. And maybe something else that evaluates the overall trends/averages? I'm an IT guy and a decent programmer, so I'd love to put something similar together (once I get to that point) that will help me analyze my logs. If I ever build something in the way of a log analyzer, I'll be making it available to the community, so just don't share your info with me if it's proprietary/sacred to you.

 

I already shared it actually, I started a thread on it and give the link to anyone interested. I use it for dialing in the MAF... It takes the average of your actual A/f, vs target A/F, and ECU corrections vs MAF voltage. Based on the calculations you can see exactly where to add/subtract on your MAF table. After only a few rounds it gets you really dialed in good.

I don't really mess with the fuel tables at all except for idle and start up -- the rest is done to the MAF table. In fact, I've found that for F/I tuning large adjustments on sections of your fuel table will sometimes cause some timing issues in boost. They are still there from time to time (seems like an inherent issue with Uprev + turbos on a DE, at least), anyways that's news for another thread sometime soon.

 

For those interested in some great reading, the link to djamps's thread about the log analyzer scripts is here

 

More about the "K Constant"
--------------------------------
The Injection Multiplier "K Constant" is one of the primary values that an ECU uses to calculate injection times for all parts of the maps. By adjusting this value, we will affect everything else.
Your K Constant should not change unless you are using different injectors or MAF.
If changing injectors or MAF, the new K constant can be calculated based on the ratio of old vs new.
You can calculate a rough estimation on your new K constant when making changes to get you "in the ball park" -
- For injector changes: New K Value = (Stock K value) * (Stock injector size) / (New Injector Size)
- Bigger injectors will result in a smaller K value.
- MAF are compared based on max horsepower reading.
- For MAF changes: New K Value = (Stock K value) * (Stock MAF max HP) / (New MAF max HP)
Since the formulas are a rough starting point, you will need to verify/adjust your K constant by running the engine and checking the AFR in a region of the fuel map that is running in "closed loop" (AFR = 14.7:1).
However, while in "closed loop", the O2 sensor will be active and the Engine will "chase the O2 signal" unless we:
A) Physically unplug the O2 sensor
B) Turn off O2 feedback in the cells of the fuel map
C) Disable the O2 Sensor
You may also need to disable knock sensing if the ECU is jumping to the knock maps while you're trying to get your K constant set correctly.

 

That makes me wonder, are Knock maps still built into these later ECUs?

 

I'm not sure, but knock maps is what I'm reading/learning right now, so that was a well timed question. I'll see what I can find out...

EDIT: From the Uprev Osiris documentation, it looks like Uprev has two Ignition maps for our ECU, so logic dictates that the stock ECU works the same way. Osiris calls them "Timing Low Det" and "Timing High Det".

So,It looks like they do have separate Knock map.

 

Things to consider before tuning fuel maps
----------------------------------------------------------
Coolant Temp:
The ECU will vary mixtures depending on coolant temperature, so it is important to keep the coolant temperature stable in order to get consistent readings. This means monitoring coolant temp, warming the engine before a run, and letting it cool down between runs if necessary. If tuning a street driven car, it is best to aim for 85 degrees C as this is the average temp in normal driving conditions. Track cars will run hotter, so check mixtures at higher temps that are representative of the average during a session.
If you have made changes to your stock thermostat, be sure that the engine does not drop back into the "cold start area" below 70 degrees where the ECU will be compensating for the low coolant temperature.

Main vs Knock Maps:
There are two types of fuel maps, "main" and "knock". Sometimes these are referred to as "premium" and "regular" maps referring to the type of fuel. The engine should normally run on the "main" map with an appropriate tune and the correct octane gas to prevent engine knock. However, if knock is sensed, the ECU will jump into using the "knock" map. With most tuning systems, the tuning is done on the "main" map and the "knock" map is generated as a copy that is a bit richer. This is so that when knock is detected, the knock map will richen mixtures to help alleviate knock.
If your changes while tuning are not having any effect, be sure to check that the ECU hasn't jumped to the knock maps.
Also, some vehicles with worn engines and/or high boost will detect engine noise as knock and may require that you disable knock sensing.

 

Excerpt from Osiris manual:

"There are two timing tables to consider for each map slot. TimingHighDet and TimingLowDet. The TimingLowDet table is the one that the ECU runs during normal operation. The TimingHighDet table is what the ECU will switch to if it thinks there is something wrong, for instance if the ECU detects too much noise from the knock sensor, or if it detects too many misfires. For most naturally aspirated applications you need not pay any attention to HighDet table, but for forced induction applications make sure that the HighDet table is set to values lower than those in the LowDet table."

 

Sweet, fueling knock table as well?

 

Just hi and low 'det' timing tables. To be honest it takes a **** ton of knock to kick you to the hi det table...in all my tuning (and mistakes) I've never been kicked to the hi det map... but from what I've heard from Uprev the ECU does pull timing temporarily for occasional knock, and only switches to the hi det map if there is constant knock, such as bad gas, 87 octane ect.

 

Is there any indicator to know that this is happening while you are tuning? Is it just that it is switching over to the high det values and switching back? How does the ECU determine how much timing to pull if it's not using the ign maps?

I would hate for the ECU to change timing during a tune based on factors completely out of my control, for me to tune based on that, and end up with bad results afterwards.

 

Subbed to obtain new knowledge Keep up the good work sparkle