I have no real evidence of this I'm just asking a question.

But I was doing a compression test a few days ago (which turned out fine BTW) and it seemed like the electrode on the spark plug for cylinder number 4 was a good bit whiter than the rest.

does it make sense that cylinder number 4 would run leaner since It's the farthest away from the fuel pressure regulator???

just wanting to get opinions on this if anyone has experience with it.

thanks,
John


BTW this is the cylinder that I had to repair some of the wiring for the fuel injector for. But I soldered the connection like a SOB lol....I know that would make a difference if it wasnt getting a good connection...BUT I'm pretty sure the connection is good....is there anyway to check for just that injector in the AEM ems?

 

The #4 runner (closest to throttle body inlet) in the stock intake manifold flows the most air so it would make sense unless Mitsu some how compensated for that with additional fuel. A stock VIII intake manifold was flowbenched locally and I was very surprised at the imbalance between runners.

 

I think it does. Over the years I have seen many examples of failed pistons with the most common being #4. When my engine popped, it was the #4 that had the detonation.

 

I would imagine an intake manifold with better flow balanced runners would be a benefit.

 

it doesn't really matter what plugs look like from running at idle. if it was white at full load then i would worry.

 

^^^ yeah I'm aware of that, In general the 4th spark plug is a whiter color. I'd have to put another set of plugs in to see if it's still real white during WOT...BUT I'm untuned right now so that'll have to wait

 

#2 runs leanest . it receives most air. #4 runs richest. It receives least amount of air.

when you run alky injector you can reverse above as the incoming air is now filled with alky . #4 leanest, #2 richest.

 

^^^^ hmm, thats weird...ya think it depends on what intake manifold your running also?

 

What ecu are you using, stock? 4 egt sensors and an ecu with individual fuel trim would be a good way to even the cylinders out, or could you do it just by reading th plugs and adjusting the ecu?

 

im using the aem ems... wonder if there is a way to check the number 4 cylinder injector somehow in the aem???

as in voltages, pulse width, duty cycle. to make sure it's firing ok since its the injector I had to solder the connections on.

 

Putting fuel in the air flow coming into the intake would simply increase the available fuel in the same proportions as the flow to the cylinders in the first place. If #2 got the most air to start with, it would also get the most additional fuel, which would tend to richen it up some. #4 gets the least air, so it would get the least additional fuel, causing it to go a little leaner.

Is that about it?

In order to make #2 and #4 switch positions completely, how much alcohol would you need?

 

I see how you looking at it. If I'm understanding it right it doesn't work that way. On a maf car the maf reads the air flow in return tells the computer to fire the injectors for this amount of air. All the injectors are fired at the same duty cycle (injector flow rate) witch in returns means the same amount of fuel. So with that being said the computer will not correct for the amount or air in each intake runner just the the air that is flowing through the maf.

Now on a stand alone like a aem. You can adjust each injector duty cycle (injector flow rate) to flow the amount of fuel per cylinder. But you would need to set it up by having 4 EGT's so that way you can tell witch cylinder is getting the to much air or not enough air. I am in no means a expert in this. This is how I understand it to be. If I am wrong please let me know.

 

#4 (runner closest to the throttle body) gets the most air and #1 gets the least. I have seen the flowbench data and the CFM difference is larger than I would think.