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8v MK2 GTI runs rich. Help please.

Posted: Mon Aug 02, 2010 6:39 pm
by KingChile619
Hi, I'm new to megasquirt and this site, but have been having a few issues tuning my car. It has been an ongoing project for about 4 years, but now I've had more time and motivation to get this thing on the road. My father and I purchased the Tunerstudio program and have been making improvements on it, but can't seem to get it right. I would have used megatune, as I notice many people use, but for some strange reason my megasquirt ECU won't communicate with megatune. It does however communicate fine with Tunerstudio. I have an 87' VW GTI 8v, which was CIS, but converted over to EFI. I used the digi 1 injector rail and injectors. I also removed my cam and adjusted my cam gear to 0 to see if it made things easier, but not really. The car runs and idles, however it runs rich (plugs are black). I can drive the car around the block and not really have any issues if I am constantly putting my foot into it. However, once I try and hold my rev at a constant RPM value, even while stationary, the car spudders out like if it's misfiring. This causes my car to yank back and forth pretty significantly as if my car wasn't getting enough fuel. My father and I have tested the MAP sensor for adequate vacuum, sent out fuel injectors to be cleaned & tested, tried a new fuel pressure regulator, etc. The car revs well, whether cold or warm, but only idles superb when warm. I did notice my 02 sensor spiking while monitoring the values of the sensors, so I was going to swap that out. I am currently running a narrowband 02 but want to run a wideband 02 sensor as I've heard you get better tuning out of it, but am unsure of how to do so. I know my car is running rich because my plugs are completely black when I pull them out. What I want to know is if someone has a completed saved tune that they can share with me so I can experiment with that, or if someone can atleast point me in the right direction to helping me get it to lean out. Most of the numerical values and charts on the program are gibberish to me, so its a bit difficult for me to get it right. I am also willing to pay someone to help me get my vehicle tuned, if anyone knows of anyone who does megasquirt tuning in the San Diego area. Any tips, pointers, advice would greatly be appreciated. If there is any other info needed to know that was probably left out, feel free to let me know and I will do what I can.
Thanks.

Re: 8v MK2 GTI runs rich. Help please.

Posted: Tue Aug 03, 2010 4:53 am
by Matt Cramer
If the numbers and charts are, in fact, actual gibberish, that's you're problem. :)

Seriously, you need to read up on tuning MegaSquirt and get a better understanding of what's going on with your system. The main numbers that control fuel when the engine is warmed up are Required Fuel (your base pulse width) and the VE table (a percent multiplier that the computer multiplies Required Fuel by, then factors in air density corrections). The VE table is your primary tuning tool. You adjust the numbers in there at the RPM and MAP reading you're running at until it's not running rich. Bigger numbers = more fuel, so you're going to have to make them smaller.

Re: 8v MK2 GTI runs rich. Help please.

Posted: Tue Aug 03, 2010 7:50 am
by KingChile619
Ok, that's a start for me. I will definitely check that out and read up on that. Thank you