NefMoto

I remember hearing somewhere that logging a tuned car's maf values might not equate to real-world values like it does when running the original software. Any truth to this? Like as a maf-reading sanity check on an OE setup, you could assume the values in g/s would end up roughly 80% of the rated hp, and when flashed that ratio would be different. I understand this is done to get more range out of the maf (like using a larger housing) but what if the housing dia. is the same?

I think it might be ok for stock but on the hybrids I've seen you can easily log 275grms and only be making 310bhp! On my poorly TT the other week it ran 288grams and made 250bhp! Now fixed but goes to show its not that accurate! I think if you can dyno your car and get a maf reading you have a better ratio to work from.

I want to log a tuned but otherwise stock B5S4. I suspect the maf (bosch) is bad, but wanted to see if the values would be accurate because it has a flash.

There is absolutely no point. Honestly.

If you want an HP estimate, use ecuxplot's HP estimator, or get a gtech, or find a dyno.

Not trying to estimate hp (I'm not that crazy). Just trying to verify a maf is good.

If you aren't getting any codes, the most obvious symptom of a bad MAF is questionable fuel trims.

Ok. We originally thought the car got a bad tank of fuel because it came on so suddenly.New plugs.

How is AFR? Trims?

I will check the trims later today. What's the best way to check afr? I'm more familiar with later versions of me7 where you can look at blocks 30 on up for requested afr vs. actual..

if you have a narrowband car, you can only see open loop AFR via sniffer or aftermarket wideband.

However, your trims should reflect how far off AFR is during closed loop.

Is this because there is no measuring block, or the values of the narrowband will be so far off @ wot they are of no value? What if the trims are ok, but the car still misses hard on load..Fuel pump?

Because a narrowband sensor is good at what it's name implies: a very narrow band of O2 mixtures, namely lambda 1. Please research narrowband vs wideband. I'm not going to go into an in depth description of something you can find trivially on your own.

Speaking of trivially easy to find information:

Misfires could be due to any number of things. Coilpacks, POS/ECM, plugs, injectors, pump, filter, valves, rings .. blah blah.

The list is a very long one.

Thanks for your help, nyet. I realize the list is endless as far as possible causes for misfires. But this happened from one day being great, to missing (8-10 deg of timing pull on all 6) the next day only under high load. I doubt all 6 coilpacks died at once, or all 6 injectors, or both icm's, and there is no reason to suspect mechanical failure at this point. I originally started this thread to find out if I could expect maf values in a flashed ecu to mirror stock values to rule out the maf (which still has nyet to be verified by anyone unless I missed it), since at this point it's my most likely suspect. I also just wanted to know if there were any other less known/obvious ways to verify I was getting enough fuel. I will try and keep the trivial questions down to a minimum.  :)

My first guess is fuel pump.

You can actually see if you are going super lean w/o a wideband if you see narrow band voltages oscillating, and your req AFR is, say, <12

In any case, there are easier ways to debug this than to dick around with MAFs, imo.

A single log should be sufficient.

Every morning.

 :)