Here's a question from the curious. From what I can tell, the computer ignores the MAF under WOT conditions on most chips. Is my understanding correct? Can one of the gurus explain why this is done? I would think using MAF and O2 readings would provide the best performance under all conditions, assuming all sensors are working properly.
MAF Ignore @ WOT?
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Thanks. I thought they offered something. I've been trying to get there, but for some reason the site won't fully load on my work computer. Just have to wait until I get home I guess. I'm actually more interested in simply learning how and why different systems work. A few guys in the club I'm in run FAST XFI while many others simply plug in a TT v5.6 chip. Then there's Eric's v6.0 chip with wideband control and this Extender Extreme which uses the MAF. Seem's like there's soooo many different ways to tune the car.
So if the MAF locks to 255 at WOT, is it basically becoming a speed density setup then? Anybody know any good things to read off the top of their head?
Thanks, Dave
So if the MAF locks to 255 at WOT, is it basically becoming a speed density setup then? Anybody know any good things to read off the top of their head?
Thanks, Dave
To be more precise, Eric doesn't have the Extender Extreme. That's strictly a Full Throttle chip which Bob Bailey designed. It's the only one that allows maf reads beyond the ECM's 255 limit.
A few things......... the erics wb chip with o2 correction will not work correctly with the extender extreme. The extender extreme has no wide band 02 correction. Fueling goes vs tps vs rpm(alpha N) after the maf is maxed out. The car has to be made richer mid range so at the top of 3rd it doesn; t lean out. Bring the boost to high and it will go lean at top end. If you have a real stout combo, like i have you will max out the extender extreme........Then you will need a XFI, dfi, which will NEVER get the same gas mileage and like a stock ECU, due to no DECEL fuel cutoff. and different fuel settings for different gears, and lack of MAF accuracy etc.
Sorry for the confusion. To clear things up, I was simply stating some different chips/tuning methods that I already knew of, but don't know all of the ins and outs. I know the TT chips and Extender chips are from different people. Both companies have been great to work with and I will continue to do business with them! To make my intentions more clear, I'm not necessairly looking to purchase anything, just wanting to get a better grasp on things, like what's best for my combo. I currently have a TT v5.6 chip in my car that I have yet to tune, but I am certainly not opposed to try a variety of different methods. That's what makes this hobby fun!
Norbs, you make a good point about maxing out the Extender Extreme's limit of 767 g/sec. Is this something that is fairly easily done with a big turbo, front mount ic, ported intake, GN1 heads, and 3" exhaust? See my sig.
Norbs, you make a good point about maxing out the Extender Extreme's limit of 767 g/sec. Is this something that is fairly easily done with a big turbo, front mount ic, ported intake, GN1 heads, and 3" exhaust? See my sig.
No, it is never a speed density setup with just the stock parts. With a non-extender, non-wb feedback, non-trans pro sd, non-tt sd chip, in other words old school stock style setup
-)), once the maf hits 255 or is locked at 255 the ecm has no way to tell how much more air is going in. It always uses the maf reading in the fuel calc, which is why it's good to lock it at 255 to prevent dropouts for those who don't run a tranlator which does it in hardware, but the number quits changing. There is no map sensor that the ecm reads, so no speed density calc. The ecm just dumps in fuel according to the pe-rpm and pe-tps tables (yeah, there's a couple other things but these are the biggies), and since we are talking wot here the pe-tps value will stay the same through a run so it is really just how much fuel is in the pe-rpm table. So to tune you can either set the boost and vary the fuel pressure to bring the fuel to the air or set the fuel pressure and vary the boost to bring the air to the fuel, but you only know if you got it right after the fact when you look at a data log. Chips like the adjustable tt ones let you shift the pe-rpm curve up or down instead of changing fuel pressure but there is still no real time feedback. It's all on the tuner to get this right and keep it right pass after pass as the air density changes.Dennis Leek has written some articles about ecm operation that are on the turbotweak website, and of course the gnttype site has the actual ecm code listing if you want the real nitty-gritty, along with a couple of spreadsheets with the data table info for the stock chip.
I gotcha. So under WOT the standard chip type ignores all sensors and just runs its program with the MAF pegged at 255. It's up to the user to set the boost, fuel, timing, alky, etc to obtain the proper A/F ratio with zero knock if the chip has that adjustability (which TT does). Makes sense to me.
So wouldn't the best option be a setup where the MAF sensor and computer could read a HUGE amount of air flow along with a wideband communicating back to the computer as a secondary check? Wouldn't this yield the best drivability and performance with the least amount of tuning? The only problem I see with this is when the alky injection kicks in. For it to work the computer would have to control that as well.
So wouldn't the best option be a setup where the MAF sensor and computer could read a HUGE amount of air flow along with a wideband communicating back to the computer as a secondary check? Wouldn't this yield the best drivability and performance with the least amount of tuning? The only problem I see with this is when the alky injection kicks in. For it to work the computer would have to control that as well.
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Like Jay just said. MAF Translator GenII or MAF Translator Pro take care of all of that just fine.
Click the Translator Pro link in my sig. and you can read all about it.
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The same as the Gen 2 but it also will run speed density.
Yes! Not only WOT (like GenII), but also has the ability to run PTT (part throttle tracking) during idle and cruise. So virtually WBO2 control over the entire spectrum of rpm/load. Or you can run the stock ECM closed loop (stock O2) during idle/cruise and WBO2 at WOT.
And yes, as Jay stated. Full speed density capabilities, closed loop boost control, double pumper pump control, etc.
