leaner or richer?

[xlMcMlx DsM]

im still new with dsm's and was just wondering, what is the difference of running a car with a leaner a/f ratio and a richer a/f ratio. which is better for street driving and which is better for racing? thanks

 

[femmeDSM]

To directly answer your question, neither is really 'better' for either.

More specifically, running either too rich or too lean can and will damage your car. Granted, the negative side-effects of running too lean are drastically worse than running too rich would be, but as I said, neither are good by themselves.

The main goal in tuning a fuel system is to maintain a stoic (technically speaking, as close to a 14.7:1 ratio as possible) mixture. The higher your boost, however, the more you will need to fine-tune this mixture by way of an S-AFC, DSMLink, or combination of the two.

Running too lean (too much air in relation to fuel) will cause big, big problems (i.e parts of your engine on the ground). Running too rich (too much fuel in relation to air) will also cause problems but usually not the "drastic and fatal engine death" variety.

 

[dherron]

Lean= Makes alot of heat just think of it as a torch when you crack up the oxygen it gets hotter, then booom to much oxygen kills everything, think of that as your motor.

Rich= Back to the torch, Makes a whole bunch of little black flyer guys and wont cut ne thing at all and just makes everything dirty surrounding it. Think of that as your oil, it will probably get contaminated by the fuel.

If you ever run a torch you find that there is a perfect place to have everything set and it will be safe and all good. And also with the torch act like you are driving your car and with the perfect mixture you are heating up the biggest V8 guy on the street and then you press the lever (oxygen), think of that as your gas pedal, you press it and you blow him away haha. I found this a funny way to write this.

 

[xlMcMlx DsM]

cool. thanks. im asking this because this is probably the first thing im going to do 2 my DSM.(after the DSM cheap mods)

 

[GSTealth]

Usually people will go a little more on the rich side to give themselves a larger safety margin when running high-than-stock boost levels.

The main question to ask is, how are you measuring your a/f levels? The stock O2 sensor is imprecise and only good as a general indicator if you are running rich or lean, but not really good for precision tuning purposes.

Really depends more on your mods and boost levels and what makes your car happy (getting excessive knock already?) as far as target a/f ratio. Also combustion chamber characteristics (one reason why a particular number doesnt necessarily transfer well between different car models).

 

[femmeDSM]

Usually people will go a little more on the rich side to give themselves a larger safety margin when running high-than-stock boost levels.

The main question to ask is, how are you measuring your a/f levels? The stock O2 sensor is imprecise and only good as a general indicator if you are running rich or lean, but not really good for precision tuning purposes.

Really depends more on your mods and boost levels and what makes your car happy (getting excessive knock already?) as far as target a/f ratio. Also combustion chamber characteristics (one reason why a particular number doesnt necessarily transfer well between different car models).

This is correct.

The only way to truly monitor your AF ratio is via a wideband O2 and datalogger. All the A/F gauges are good for is a light show and not much else. If you are actually running dangerously lean, the A/F gauge will tell you, but by the time it does, chances are the damage will have already been done and you will be on the side of the road calling a flatbed... It's a good indicator of *why* your engine took a crap, but is not to be used as any kind of warning that it's "about" to take a crap....if you get what I'm saying.

All that being said, the fuel system is a great place to start when beginning to mod your car, provided you do things in the right order. I always recommend an upgraded (or at the very least rewired) fuel pump as one of the first performance mods for DSMs because it opens the door for more safe modifications and eliminates the worry associated with not getting enough fuel to the engine (which can be disastrous).

Have fun modding your car -- and remember to make sure the car is in excellent running condition before you start throwing more power at it.

 

[xlMcMlx DsM]

ok cool. because i was thinking of doing the fuel system first and like FemmeDSM said, it will open up a bigger area to mod and things such as tuning and what not. I also have another question. Will a downpipe with an O2 emilinatior help with boost leakage? i've heard they will but are a little expensive. does it have anyeffect on the stock O2 sensor? or does it replace it?I know turbo back exhaust systems will replace the O2 housing entirely, but does a downpipe do anything to that? thanks