What this applies to: Primarily to tuning the Honda K-Series engines used in the Acura RSX and Honda Civic Hatch with a Hondata K-Pro ECU and Hondata K-Manager software.
Concept and goal: Most people will not create a K-Pro calibration from scratch. Instead, they will start with one of the many library calibrations that come with the K-Pro's K-Manager software. Most, but not all, are the result of extensive development and tuning by Hondata. However, Hondata developed them on a particular car with particular modifications. Yours may be different and by adjusting the air-fuel ratio, tweaking ignition advance, and perhaps trying out different cam angles, you can customize and finetune an existing calibration for your car. This can be done in an hour or two on a dyno.
How it's done: If you decide to start with an existing map you will not do all the steps required to create a calibration from scratch (like doing fixed cam angle runs to create your own composite curve). Instead, you'll use the existing cam angle maps of a calibration and then tune fuel, ignition timing and make perhaps a few changes to the cam angle maps.
1 Tuning fuel maps
The fuel maps are tuned first because having the proper air-fuel ratios is very important for best power and also for engine health and durability. To start the process, do a dyno run and see what the air-fuel ratios are through the rpm band. Then adjust fuel to get to the proper target AF ratios.
- Columns 1-6 are part throttle and there we want 14.7 AF (which the ECU corrects to anyway when it is in closed loop).
- In column seven we want an AF ratio of around 13.8-14.
- Columns 8 to 10 are full throttle for normally aspirated engines, and we want the AF ratio to be around 13.
- For super or turbocharged vehicles, the boost columns 11-16 should be 11.5 to 12.
If you can't be on a dyno, you can use a datalog as the basis for fuel map tuning. I always recommend a full throttle 2,500 rpm to redline run in third gear.
When tuning, always select and change rectangular areas in the tables. That way all fuel lines remain parallel. Smooth fuel curves run a lot better than bumpy ones. Once the curves are all done and the next dyno run shows the air-fuel ratios we want, first increase and then decrease fuel for the entire table by 5% and do additional dyno runs to see if you get more power.
2 Tuning ignition advance maps
The goal of ignition tuning is to have ideal ignition timing advance with minimal knock count.
Getting the optimal ignition advance is key to getting the most performance. For that, you highlight columns 7-10 for all rpm (boost columns 11-16 in turbo or supercharged engines), then add two degrees of ignition advance and see if performance increases, and whether or not the engine is knocking. If power increases without knocking, add another two degrees.
Once best power is found, reduce ignition advance by two degrees for optimal reliability. To be right at the point of maximum power puts substantial extra stress on components. Do this for each cam angle, both low-speed cam and high-speed cam (if you're familiar with the K-Manager maps, you can determine which maps are actually used and only make the changes to those cam angle maps).
Knocking is caused by too much ignition advance and bad fuel. It is also worst when going uphill when the engine gets hottest. To eliminate knocking retard ignition or get higher octane fuel. To eliminate knocking, locate the knock areas on a datalog, then select a rectangle of data points at that area, and reduce ignition by 2% or so. Test to see if the knocking is gone. For a step-by-step tutorial on how to eliminate knocking, click here.
3 Tuning cam angle maps
The cam angle can have a significant impact on engine performance. While tuning, it is therefore a good idea to see how the engine reacts to lowering and increasing cam angles across the entire cam angle tables, both low-speed and high-speed.
First increase all cam angles by five degrees from the default values by selecting all values and then use either the Ctl-I function to incrementally increase or the Ctl-J function to enter a value. Do a dyno run and record the results. Then decrease all cam angles by five degrees from the default and do the same. If you are only concerned with full throttle performance, perform the above cam angle variations only on columns 7-10 for normally aspirated engines, and columns 11-16 for turbo or supercharged engines.
4 What is most important for power gains?
Tuning is a very time-consuming business. It therefore makes sense to know what parts are most important when it comes to generating extra power. According to Hondata, optimizing ignition advance is most important. Next is picking the proper cam angles for each part of the table, then setting the proper VTEC point or window, and finally setting the correcting air-fuel ratio. So:
1 - Ignition advance
2 - Cam angle
3 - VTEC point/window
4 - Proper fueling
5 Where should I set my VTEC point?
Getting the VTEC point right, and setting the cam angles at the cross-over right, is very important and one of the most difficult tuning tasks. If not done right, the power curve is bumpy and performance suffers. In theory, the VTEC point should be at the intersection of the low speed and the high speed torque curve. Another issue to look out for is the cam angle at VTEC. If the low speed cam angle at the VTEC switch-over is far apart from the high speed cam angle, the cam needs to rotate by a lot (it takes the cam about 1/10th of a second to rotate by ten degrees). This can result in a power dip for a few hundred rpm after VTEC while the cam rotates into proper position.
So, ideally you do a low-cam-only and a high-cam-only dyno run and see where the torque curves intersect. That is your VTEC point. If you can't do that, normally aspirated k20a2 engines like the VTEC point at 4300-4500 (much lower than the stock VTEC point of 5800). Turbo engines usually have their torque crossover at a much higher rpm, Use a fixed VTEC point at around 6,000 rpm. With supercharged engines it is the opposite. They like the VTEC point between 3,000 and 4,000rpm.
6 Where should I set my rev limit?
Set it to about 500 rpm past your power peak. That way, when you shift near the fuel cutoff, you drop back to a point where you already have lots of power, but also still have a couple of thousand rpm ahead until you reach peak power in the next gear. How high can you set the fuel cut-off? That depends on the strength of the rods and the pistons, and springs that are not up to the job can result in valve float and damage to the pistons.
Questions? Email me at conradb212@mac.com
