Specializing in the 3g CSM
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PostPosted: Mon Dec 14, 2020 2:51 pm 

Joined: Fri May 08, 2020 1:11 pm
Posts: 59
Location: Germany
Hello y'all,

Flying Eagle encouraged me to start this thread. I don't know where to start so I'll dive right in.
No one so far cared about chip tuning for our 4G15 engines. So I decided to start on my own!

As I have a european model my engine (4G15 12V) and ECU have a knock sensor and associated circuitry. I had built a Palm cable to log stuff and did a few runs to get a feeling for the car's behaviour under certain conditions. But MMCdlog is slow as hell so I constructed an USB cable and wrote my own ADX file for TunerPro RT. I'm not affiliated with this software or its author(s) but I highly recommend it! Logging via USB on a laptop is much quicker that with a Palm. I can achieve apx. 40-50 samples/second with TunerPro rathen than the 3-6 samples/sec of the Palm. I will explain later why this is important.

Then I got ahold of an EPROM ECU and started digging through the code. I found many interesting things and can likely do as much as the DSM guys. But progress is slow as I'm a one man show here. To put it short what I can do or modify:

- timing maps
- AFR maps
- rev limiter
- idle speed
- injector size
- MAF scaling
- increase logging speed

I heavily modified my timing maps. This yielded much lower fuel consumption as the engine runs more efficient at part throttle. It pulls really hard and is - for a 1.5 liter engine - torquey. Mind you, apart from a 1.75 " exhaust this car has no engine mods! I run on the verge of knock. But it's safe as I have a knock sensor to rely on. Interestingly 100 octane fuel didn't help much.
But it didn't increase top end power. There are these mods with Galant MAFs, injectors, and throttle bodies but the car usually runs like a bag full of nuts as the maps don't match anymore. I didn't like that idea at all.

You all probably know the 1G NA MAF. I reckon it's the same as the Lancer GTi (4G67) MAF I got ahold of. I installled it, burned its scaling values into a fresh EPROM, started the car and... It purrs like a kitten! Or more like a dozen kittens as the induction noise got louder. The idle is rock solid and much better than with the stock MAF. The engine runs much smoother. I had to adjust timing and AFR tables anew though. I always log the load values from the ECU, as to know what load cell I'm in and I think I saw larger values with the larger MAF; a simple bolt-on modification,, no larger injectors needed.
The next bolt-on mod will be the larger throttle body off a Galant. I will keep an eye on load and airflow to estimate any power increase.

I also noticed that although the sample rate is 40-50 samples, some values simply don't line up. It looks like the ECU updated the revolution value and MAF Hz but not injector opening time (which is absurd), and other effects like that. It makes tuning a bit harder.
My approach against that is to increase the Baud rate from those slow 1953 bits/second to higher speeds. I tried that in the past on the bench but decided against it. Why? Because a 40 minute log file has like 80,000 lines to browse through...
I hacked the existing comms routine to a slightlly higher Baud rate and got 125 samples/second reliably.
I now need to test that on the road. Maybe someday I can log as fast as DSMlink.

What does that mean for you? Assuming that you have an EPROM ECU you now can:

- increase fuel economy and "torquey-ness"
- get the MAF/injector/throttle body combo to work right finally
- or get it to run right with E85
- run a knock sensor (with a euro ECU - or maybe a modded US ECU?)
- turbocharge your 4G15, 4G37, 4G6x SOHC safely (the ECUs are the same, only the EPROM contents are different)

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