Supercharger and Fuel System Discussion Thread Take 2

[cruiserdan]

I wish I was smarter than I am but I guess we all do.

I can say that my vehicle will knock, somewhat violently, at WOT, above about 3600 RPM, if I do not "inject" it with a dose of 50/50 distilled water/methanol at a rate of 14 GPH.

This "result" tells my feeble mind that I am either lean or my intake temp is too high. A further observation tends me to believe that I am a bit of both. If I inject plain water, I stop the knock. When I make it a 50/50 cocktail, I get a "kick" in the seat of my pants when the methanol comes on line.


Clearly the 93-94 fuel management system is not enough. That is a simple fact. The complexity lies in how to resolve this simple problem in a manner that results in a modified vehicle, producing a significantly greater ammount of power, with the overall driveability, and reliability, of a stocker.

 

[firetruck41]

I doubt I will ever have the spare $$ to do forced induction, but this is an interesting thread. I was looking at the megasquirt site a little more, and found a section which talked about "Turbocharging and Megasquirt" (could relate to SC as well).

Excerpt below, a lot more at this link: http://www.megamanual.com/

Turbo Tuning with MegaSquirt

To set up the fuel curves for your turbocharged engine with MegaSquirt, you have a number of parameters to work with. The most important of these are the Req_Fuel value and the VE table (8x8 volumetric efficiency table). You are aiming to achieve 11.0-12.5:1 air/fuel ratios at full boost, and 15-17:1 under light loads for a turbocharged engine.

If you did not have MegaSquirt, you would need an add-on fuel controller, a rising rate fuel pressure regulator, or some other trick to add extra full when the boost comes on. With MegaSquirt, though, you simply program in longer pulse widths via the VE table.

Having an O2 sensor makes tuning much easier, as you can datalog and use MegaTweak. With a turbocharged engine, the oxygen sensor can be placed either in the exhaust manifold, or downstream of the turbo. Frequently, the outlet housing that bolts to modern turbochargers (and that cover the wastegate port), provide both a 90º bend in the exhaust path (making the fabrication of an exhaust system a great deal simpler) and also often have a suitable threaded bung for an oxygen sensor.

To get the VE table set, adjust the boost as low as you can, if you have an adjustable wastegate. Turn on datalogging in MegaTune. Take a few easy drives up and down the street, keeping the revs down and the throttle light. Adjust the VE table according to what MegaTweak tells you. A bit more tuning, and you are ready to go a bit harder. Increase the revs, or increase the boost a bit. Do not go harder if there are any problems [typically a back fire means too lean, sluggish revving means too rich]. Read the Datalogging and MSTweak3000 section for more information.

 

[clownmidget]

Ok I've got a headache in my eye from reading this stuff on a Friday evening and mixing ethanols...

http://www.3si.org/forum/archive/index.php/f-103.html

 

[landtank]

Clearly the 93-94 fuel management system is not enough. That is a simple fact. The complexity lies in how to resolve this simple problem in a manner that results in a modified vehicle, producing a significantly greater ammount of power, with the overall driveability, and reliability, of a stocker.

I'm all over this Dan and am quite sure I have the answer to your problem.

I'm more convinced than ever that approaching this from a TUNER point of view is coming at it from the wrong end.