Street Tuning

Recently my turbo engine blew up, so I installed a stock NA engine in my car, and hooked up the existing wolf ECU to run it. This is a write-up of my personal experience in learning how to street tune a car with a custom ECU and a wide band oxygen sensor.

Engine: Standard RB30E, stock injectors with Wolf 3D V4 ECU

Equipment used

Wolf ECU Laptop with wolf tuning software Wide-band oxygen sensor

Objective

Make the mixture 14.7 on idle and cruise, at around 40% throttle i think i want about 13:1 AFR, going richer to 12.5 from between about 50% to 100% load

Air fuel ratio under full load

From what my research tells me, the best full throttle mixtures for an NA for most power is 12.5:1, however 13:1 is ok for better economy.

A turbo should run at 12:1, or even 11.5-12 for a high compression engine according to some other sources. Although, people say that 12:1 is safe even for a high compression RB30E +turbo engine. That is what my old turbo engine was tuned to.

Step 1. Starting the engine

I made a guess with the cranking mixtures, set the injector opening time to 3ms, and 10 degrees timing. I had trouble starting the car, it would just keep cranking but not ignite. I realized that the idle air screw on the plenum was out way too far, so i screwed it in roughly half way, and tried starting the car again. The car started ok. Not perfectly but this will be tweaked later

Step 2. Setting idle mixtures

car was idling at around 10% load, so mixtures were adjusted to give 14.7-15 at this load at 700rpm. Need to keep in mind that adjacent load cells will also effect the mixture, so adjacent cells will also need to be fairly close to the currently highlighted cell in the fuel map I set the whole range of rpm to the same value as the idle AFR for now, at 10% load. At this time i estimated some values for the rest of the fuel map. i just increased the injector rate by 1ms for every 10% increase in load, with no change in fuel rate for the rpm at the moment.

Step 3. Setting the free revving mixtures

right through the free revving rpm range, the load stayed at 10%, so this is the load band that i am adjusting here, plus and minus 10%, as you need to tune adjacent cells at the same time. A little richer on the next load range up, and a little leaner on the next load range below.

Rev the car to 2000 rpm, set mixtures to 14.7 I then did the same for 3000 and estimated the rest of the rpm up to 6500. Gave the car a some higher revs, and the mixtures were fine. You could manually hold the revs at each rpm and set the mixtures, but i seriously couldn't be bothered.

I then set up the transient acceleration enrichment. This happens when you suddenly accelerate. If there was no transient enrichment the engine would run lean for a second and hesitate. The wolf uses a throttle position sensor as its transient sensor. To set this i just revved the car in neutral, pressing down on the accelerator very suddenly, it gasped before revving, so i bumped up the transient a bit, it gasped a bit less, kept going until i got that hesitation down to a minimum. I set the transient under all loads to be the same for now, which was around 400% additional fuel from the top of my head.

Step 4 is if you have an auto transmission

Step 4. Auto transmission stuff

put the car into Drive, and note the idle speed. If it drops too much, the currently selected cell will change in the map. you can open the timing map, and increase the timing in this cell +5 degrees or so, which should be enough to bump the revs up a little bit higher. May need to tweak this and/or the mixtures to get a consistent idle speed/idle mixture no matter if it is in Neutral or Drive.

Then, sitting in the driveway, i loaded up the car against the stall converter, to get the load up into the next 10% up range of cells, and adjusted the mixtures to around 14.7 I then pushed the car fairly hard into the stall converter (hard on the brake and accelerate in Drive) , which in my car is a 2800 rpm stall speed. I set this to about 13:1. Again, i set the whole rpm range at this load to the same injector rate for the time being. Have to work very quickly here, as the torque converter heats up a lot, very quickly. I then estimated the missing section in between.

Step 5. Driving

I set up the mixture meter on the dash directly behind the steering wheel so that i could see the mixtures without taking my eye off the road. I basically started driving around my streets, slowly, and tweaked the mixtures to get 14.7:1. I found myself pulling over and adjusting blocks of cells then driving again, etc. etc. Got to the stage where i was driving around on light throttle with the mixtures all looking good. I then started giving it small amounts of acceleration and adjusting mixtures accordingly. Under any of these "not normal cruising but still light-medium accelerations" i made those areas on the fuel map give me 13:1. I think this was around 50% load. I then gave it a bit of a full throttle run, but backed off as the mixtures were showing <10:1 So i leaned up the top section of the map a bit, and gave me 11:1, which was still way rich, the car didn't want to rev very quickly above 4000 rpm because of this. That was enough for today as I could not keep tuning full throttle with my eye on the mixture gauge, I needed to come up with a way to log data.

I ended up buying a USB to serial adapter, which then gave me 2 serial ports on my laptop. I plugged the wolf into one, and the mixture meter into the other, and ran both the wolf and the mixture measuring software at once. I then ran a screen capture program, which had a shortcut key to start and stop recording. It all worked quite nicely. This allowed me to continue tuning with different amounts of load (different gradient hills, accelerating with foot on the brake simulates hills quite nicely) and also full throttle. I could then pull over, and replay the screen capture seeing the load/rpm and mixtures on screen at the same time. Need to keep glancing at the meter a lot under full throttle still, just to make sure that the mixtures aren't going way off, such as the 15:1 that i saw once at around 80% load, accompanied with some severe pinging! Oh well, this engine is relatively disposable anyway... I suppose some pinging every now and then is inevitable while tuning from scratch on the street. You need to concentrate on the sound of the engine too, any rattles, back off immediately, check the logs and richen the mixtures if necessary, otherwise back off the timing a few degrees at that load/rpm point.

Thats how i worked out to get a basic tune down, if anyone has any more information to add, or any faults to pick out of what i said, please add it below, or let me know.

Compiled by

• Skaface