Fuel cut options

[Chris Andrews]

Jovan, have you logged your car?

Bucking is what I had, and when I looked at the airflow, it had a kind of ragged appearance.

Maybe you're just over-running the MAS......

Back to your orginal question, and my original answer.  The 2G mas will most likely solve your problem, and give you an easy to tune, no driveability issues car.  No, its not the cheapest solution.  But its one of the best, at least in terms of a good fast street car with upgraded turbo.  

If you plan on huge-ass monster turbo drag strip killer, then its not for you......

[Jovan Ceklaj]

yeah, I logged my car (on my mother's advice :laugh: ) and thats what it showed.  The Karmen frequency was at 1606 but it wasn't dropping and going haywire ala typical MAS overrun.  The only thing was a sharp spike in the Injector duty cycle to zero momentarily.

The bucking I'm talking about is just one 'buck' at a time, not rocking back and forth over and over.  I can't explain it that easily, so that's the best I have

Jovan

[Chris Andrews]

Well, the cheapest would be John's advice.
The most expensive would be Ryan Croft's advice.

If you aren't planning more mods, then hacking the mas makes the most sense.

If you still thirst for more power, sooner or later you'll need more fuel, afc's and the like,  well then its time to open your wallet..............

[Jeremy Clarke]

Here is what I logged when I first hit cut last week. I wasn't logging airflow at the time though and haven't since. I will probably do that tomoorow before the 255 goes in and after will of course be much more logging and tweaking.


I was going about 140 and it felt like I hit a deer or somthing I must have dropped 20Kms in one second. When I checked the log though it did not show (to me) any major problems but I'm still new at logging.

[Mike Schmid]

The MAF measures pressure too, barometric pressure sensor...  It has to measure everything you need to calculate air mass, otherwise it couldn't deliver fuel properly.  The 14.7:1 stoicheometric formula is derived from air mass, ie: 14.7 pounds of air to 1 pound of fuel.  The ECU has to be able to tell the difference between 1600 Hz @ 10*  at sea level and the same at the top of Roger's Pass.  Where is Yves when we need him!?   :wink:

Does the 2G MAS read the same Hz for the same conditions?  I don't think it does, because a 2G MAS works great with 550s, not 450s... I think at say 1000Hz the 2G MAS is flowing X % more air mass than at 1000Hz in a 1G MAS, so when you start flowing big air masses through a 2G MAS the 1G ECU reads it like it's a smaller mass than it actually is, thus you never hit fuel cut...?  And the car runs on this altered information because in actuality it's delivering more fuel than it knows about because your pump and injectors are bigger than stock.  So say you're sucking 15 lbs of air in reality, the ECU only reads 10 because of the 2G MAS, then it delivers 2/3 lbs of fuel, only in reality it delivers 1 pound of fuel so your a/f is still stoich.  Now I know it doesn't run at stoich, it serves the example.  That's my theory... which assumes the fuel cut is in the ECU.  I don't have any proof but yeah, I would assume Todd has actually seen the code, which should make his info reliable.  That and the MAS is just an air flow sensor... it doesn't control fuel, the ECU decides what to do with the fuel, the MAS just measures air until it flows so much the karmens get screwed and it overruns.

[Kimyee Lai]

You've hit the nail on the head Mike.  Basically the 2G MAS has a lower corresponding Hz reading, so when you put it into a 1G, the ECU thinks there's less air going into the car than actual, so it'll lean things out.  Then the 550s richen things up and it balances out.  

I've posted the question on the DSMlink forums, trying to see what the actual airflow cutoff point is.  I mean, if you can't trust people who've actually read and modify the ECU code, the only alternative is to download the code off the chip directly...

Basically, from my understanding, fuel cut was implemented to prevent airflow in excess of what the mitsu engineers felt the fuel system could reliably support.  So, the only way around it is to lower the perceived airflow and richen it up via bigger injectors, ala SAFC, MAF hacking, or take the limit directly out of the ECU, ala TMO, DSMlink.  

If you hack your MAF, make sure you have a way to compensate, i.e. higher fuel pressure or bigger injectors.  BUT, then you are looking at a non-linear flow bypass, i.e. you'll get different proportions of the flow by-passing the measurement volume at different flow regimes, which makes it hard to tune right.

[Ryan Coft]

The most expensive would be Ryan Croft's advice.

heyyyy.... get the name right at least  :cry:

[Ryan Coft]

:evil:  *beats the submit button  :evil:

[Chris Andrews]

The most expensive would be Ryan Croft's advice.

heyyyy.... get the name right at least  :cry:

I'm sooooo sorry.....  :cry:

damn r.....what the hell was I thinking? :?

[John Hartman]

never seen the idc drop off like you describe.  I have had gentle bucking tho, but I have been able to tune it out.  Not stop listening to it, tune the car.

Did you try blocking off some of the upper plenum Jovan??

[Jovan Ceklaj]

I don't think I'm going to block off the upper passage.  I guess I'll just dish out the money for one of the better solutions.  Besides, I need injectors and a 2g MAS anyways

Jovan

[Jeremy Clarke]

I've often wondered about a simple mod for the 1G MAS but have never tried it and have no idea if it would work.

Here is the theory:  If we can agree that a disproportionate amount of air enters the filter from the top side because of the lack of flow to the bottom, then we can see that the fact that the metered side sticks out so far it is blocking at least some flow to the unmetered side. If this is true, which I'm not entirely sure it is :? Then why have we never installed the MAS the other way around? As far as I can deduce it would be easy enough to do.

Now I have seen on my filter that the bottom side stays cleaner, this supports my theory and is also why I rotate the filter halfway between cleaning it.
So once you have hacked your MAS and it's still not enough and you are thinking of either covering the top a bit or completely sectioning it or simply getting a 2G MAS, wouldn't this maybe be a final thing to get another little bit out of the poor old thing?

This is just my mere ponderance. It may have been tried before but I have never heard of it. It may also just be a dumb or impossible idea for some reason I haven't thought of yet. Sooo let me know K  :wink:

[John Hartman]

the thing is, the turbo sucks it in, kinda doesn't matter how its in there.

Jovan, you don't have to cover the whole top part off, just the thickness of a piece of masking tape should do it.

Its not permanent, and if your maf is easy to get at, an easy mod to do.  It would be worth trying, I'd say.  Like I said earlier tho, I havnet had to.

[Andrew Scott]

Stop arguing, everybody, and get a MAF-T already Jovan.

[Chris Andrews]

I would consider the MAF-T if someone here can:

1. Prove that its a smooth, easy to tune daily driver.
2. Self-tune it into a consistent low 12 second car.

This is the advantage of the 2G mas.   For example,  using a 2G MAS + 650 cc injectors, all my setttings on the afc are the same.

High Throttle,   all rpm points set to -30.  
Low Throttle,  all rpm points set to -8.

Doesn't get any easier than that, does it?  

Drives pretty much like stock, except way faster....  :wink:

Also,  I would avoid having anything that can come loose (such as tape, flappers) and get sucked into the compressor blades..... :!:

I'd like to add that this is a great disscussion on the subject .....