?'s on 1jz (bpu mods, 2jz turbos on 1jz, & single turbo on stock ecu?)
#19
Instructor
iTrader: (5)
Meh. Since nobody else jumped in, here's some material from various other forums, some 1JZ specific, some Supra specific, some just MAP tuning specific for other cars.
All courtesy of Google
https://www.clublexus.com/forums/6488425-post6.html <--moderator on here mentions the fuel cut/SAFC relationship
http://soarercentral.com/sc-forum/me...75/132586.html <----3rd post from the bottom, in particular
http://www.supraforums.com/forum/sho...-need-for-BCC&
http://www.supraforums.com/forum/sho...7403-Fuel-cut&
http://www.supraforums.com/forum/sho...=1#post4503312
http://performanceforums.com/forums/...sing-SAFC-(2jz)
http://www.dsmtalk.com/forums/showthread.php?t=97849
http://www.toyotagtturbo.com/forums/...moves-fuel-cut
http://www.galantvr4.org/ubbthreads/...page=4&fpart=1
I'm not speaking some magic theory. It's been reproduced many time since the last 2 decades. If you understand how a SAFC and any of the boost cut devices work, you'll see why they are virtually interchangeable.
blk&blu*j,
I'm not sure why it didn't work for you. If your car is MAP based and you are overfueled, then I see no reason why it wouldn't. Because you appear to be a Supra guy, the only guess I can make is that your car was a USDM spec motor that ran a MAF sensor in addition to the MAP.
All courtesy of Google
https://www.clublexus.com/forums/6488425-post6.html <--moderator on here mentions the fuel cut/SAFC relationship
http://soarercentral.com/sc-forum/me...75/132586.html <----3rd post from the bottom, in particular
http://www.supraforums.com/forum/sho...-need-for-BCC&
http://www.supraforums.com/forum/sho...7403-Fuel-cut&
http://www.supraforums.com/forum/sho...=1#post4503312
http://performanceforums.com/forums/...sing-SAFC-(2jz)
http://www.dsmtalk.com/forums/showthread.php?t=97849
http://www.toyotagtturbo.com/forums/...moves-fuel-cut
http://www.galantvr4.org/ubbthreads/...page=4&fpart=1
I'm not speaking some magic theory. It's been reproduced many time since the last 2 decades. If you understand how a SAFC and any of the boost cut devices work, you'll see why they are virtually interchangeable.
blk&blu*j,
I'm not sure why it didn't work for you. If your car is MAP based and you are overfueled, then I see no reason why it wouldn't. Because you appear to be a Supra guy, the only guess I can make is that your car was a USDM spec motor that ran a MAF sensor in addition to the MAP.
#20
Lexus Test Driver
iTrader: (3)
So the 2.3 bar you speak of is 15psireally cause in my world 2.3bar is more like 33.35 psi but what do I know. I play at 29-31 psi virtually every weekend.
Also just to set you straight I was running over 20psi on 1j twins with a AFC and FCD before you probably could drive.
Since when does an SAFC touch timing the curve in timing is limited by the thresholds in the stock ECU.
I on a AFC about 6-7+ yrs ago was controlling a set of precision 680cc injectors on a 1J with a 67mm single turbo at 30psi of boost and making 600 ish hp on 110octane and without the FCD could only get to between 12-14psi before the cut showed.
But I digress I am getting old and my memory apparently is clouded.
Also just to set you straight I was running over 20psi on 1j twins with a AFC and FCD before you probably could drive.
Since when does an SAFC touch timing the curve in timing is limited by the thresholds in the stock ECU.
I on a AFC about 6-7+ yrs ago was controlling a set of precision 680cc injectors on a 1J with a 67mm single turbo at 30psi of boost and making 600 ish hp on 110octane and without the FCD could only get to between 12-14psi before the cut showed.
But I digress I am getting old and my memory apparently is clouded.
just to set you straight, the world you live on is Earth, which has an atmosphere. so when we refer to MAP sensors being 2.3 bar, one of those bars is "used up" for atmospheric pressure.
so a 2.3 bar map sensor uses 1 bar for atmosphere, 1 bar for boost, and .3 bar for more boost.
so a 2.3 bar map sensor can read up to a little under 19 psi.
so i'm guessing you have a 3.5 bar map sensor.
"Q. How is boost measured? (Bar, mmHg, PSI) and How do you convert from one to another?
A. Boost is measured as the pressure that the turbo creates above atmospheric pressure. Normal Atmospheric Pressure (1 atm) = 14.7 psi = 760 mm Hg 1 Bar is not actually equal to 14.7 psi, but rather it is equal to 14.5 psi, = 0.9869 atm = 750.062 mm Hg" -- Garrett Turbo FAQ
The 2.3bar sensor is 0-5v ref range. Without any manipulation of MAP voltage, fuel cut hits right around 4.3v which is around 14psi.
I can't speak for other cars but because the recommended wiring for 1JZ's w/SAFC taps into MAP voltage (as per Apexi website, page 6 http://www.apexi-usa.com/manuals/ele...eo_diagram.pdf ) , it does not directly control the fuel injectors. Also, because the ECU uses this same MAP voltage reference for boost cut, the SAFC can skew this value percentage-wise. It's the same concept as running a 3bar MAP sensor to raise boost cut. You lower the voltage seen by the ECU. If you tune down an injector via SAFC because you are running too large of an injector for your setup, you are in effect lowering what the ECU will 'see' for boost pressure.
I can't speak for other cars but because the recommended wiring for 1JZ's w/SAFC taps into MAP voltage (as per Apexi website, page 6 http://www.apexi-usa.com/manuals/ele...eo_diagram.pdf ) , it does not directly control the fuel injectors. Also, because the ECU uses this same MAP voltage reference for boost cut, the SAFC can skew this value percentage-wise. It's the same concept as running a 3bar MAP sensor to raise boost cut. You lower the voltage seen by the ECU. If you tune down an injector via SAFC because you are running too large of an injector for your setup, you are in effect lowering what the ECU will 'see' for boost pressure.
what a lot of people don't realize about this concept is that your fuel and timing map stops at that max MAP reading, so if you cap that MAP sensor voltage, the ECU thinks you're still running 13.5psi or whatever you capped it at. so your fuel and timing maps are exactly the same no matter how high you turn the boost up past that threshold. the more boost you run, of course, the more fuel you want and the less timing you want.
this is why OEMs map their ECUs to do a fuel cut below the max MAP sensor voltage, so you don't go over that max voltage and run lean and run more timing than you should.
Last edited by cartmill; 07-24-12 at 09:16 AM.
#21
Lexus Test Driver
iTrader: (3)
also, OP, keep in mind (after reading all that i just posted above) that INTIMAZY's recommendation of getting 550s and an SAFC2 that you're going to have almost 50% additional injector there, and an AFC can only alter your MAP signal.
what i'm alluding to is that your stock ECU has several supplemental maps, mainly for intake air temp, coolant temp, and cranking (and cranking based on coolant temp probably) that can't be changed by your AFC (ie, not based on the MAP signal), so for all of these maps that are "locked," you're going to have 50% too much fuel (same pulsewidth shot from the ECU with 50% bigger flowing injector = 50% more fuel). this is not a huge problem when you're going from 370s to 550s (ie, not huge injectors), but definitely noticeable, and the tuning/AFRs will be sloppy.
air temp correction usually doesn't get to crazy (like within a few % change unless you have big climate swings) but coolant temp correction can be drastic, like for cold starts, cruising before warmed up,etc.
and INTIMAZY, did any of those links include actual testing of the MAP sensor to show at what PSI it stops reading? (can't click them at the moment)
i was thinking it was 22 psi for some reason.
what i'm alluding to is that your stock ECU has several supplemental maps, mainly for intake air temp, coolant temp, and cranking (and cranking based on coolant temp probably) that can't be changed by your AFC (ie, not based on the MAP signal), so for all of these maps that are "locked," you're going to have 50% too much fuel (same pulsewidth shot from the ECU with 50% bigger flowing injector = 50% more fuel). this is not a huge problem when you're going from 370s to 550s (ie, not huge injectors), but definitely noticeable, and the tuning/AFRs will be sloppy.
air temp correction usually doesn't get to crazy (like within a few % change unless you have big climate swings) but coolant temp correction can be drastic, like for cold starts, cruising before warmed up,etc.
and INTIMAZY, did any of those links include actual testing of the MAP sensor to show at what PSI it stops reading? (can't click them at the moment)
i was thinking it was 22 psi for some reason.
Last edited by cartmill; 07-24-12 at 09:43 AM.
#22
Instructor
iTrader: (5)
Thanks for the support cartmill, I agree it's not a great way to tune because you simply trick the ECU into seeing less voltage but I do think that of the two options, FCD or SAFC, that SAFC accomplishes the task more safely and predictably. Here's my reasoning:
Two cars. Both MAP controlled and identical in every way.
Car A uses a fuel cut device of some sort that physically clamps voltage below the ~4.3 volt area.
Car B uses a SAFC that linearly (%age-wise) cuts down the MAP signal seen by the ECU, regardless of how high or low voltage it is.
Both cars running at say 60% injector duty cycle with plenty of headroom.
Both accelerate to the maximum PSI that the MAP resolution allows for. Let's say its 22psi for arguments sake.
When car A passed the 13psi boost cut area, the ECU only saw ~4.2 volts to avoid boost cut, despite now actually pushing 22psi. The car is now at 22psi but the ECU is really only fueling for the 13psi it sees. In my opinion, this is a BOOM waiting to happen.
Car B however, linearly reduced the total voltage the ECU sees from the MAP. When the MAP is sending 4.3 volts to the ECU, the SAFC tuned down say, 20%, intercepts it and only sends 3.4volts. The ECU thinks it's WELLL below fuel cut still and can still linearly increase fueling as psi increases even past the resolution of the MAP sensor. If combined with an AFPR, you can relatively safely make sure you don't run out of fuel in the top end.
Granted, this skewing is NOT a great idea on a big boost car but for smaller setups on smaller 550cc injectors like cartmill said, it's not bad.
The issue that comes up with this linear skew is with timing. Although the SAFC can't directly control timing, because it controls the MAP, it DOES affect timing. Why do I think so? Lets start with a stock timing chart courtesy of some forum guy that owns a PowerFC.
The only general trend you really should notice is that the map generally pulls timing as PSI increases. More boost = more conservative timing. With a SAFC you bypass this because you can be running say, 18psi when in reality you're ECU is timing it as if it was for 10psi.. (these are numbers I pulled out of my a$$, I'm NOT saying that that's exactly what's happening) This can be a problem since the timing could be almost DOUBLE the degrees it would normally be without a SAFC.
Why aren't all 1JZ's ticking car bombs above 13psi? Our ECU's are very conservatively tuned so there is sooo much room to 'trick' the ECU before something bad happens.
phew... that took a while
#23
Lexus Test Driver
iTrader: (3)
I think you just said the exact same thing I said in the previous post. But with some more detail. :-)
Hopefully people appreciate all this info! Even if they don't, I guess it's a good thing to have this info more easily accessible on this forum. We need an EMS/tuning sub forum...
A lot of people on CL seem to not have a good understanding of how engine management typically works. Maybe I just got spoiled by rx7club and my local car forum over the years.
Hopefully people appreciate all this info! Even if they don't, I guess it's a good thing to have this info more easily accessible on this forum. We need an EMS/tuning sub forum...
A lot of people on CL seem to not have a good understanding of how engine management typically works. Maybe I just got spoiled by rx7club and my local car forum over the years.
#24
Lexus Test Driver
iTrader: (4)
As for the map sensor hitting cut at 4.3, that's pretty damn accurate. I did a lot of logging with my emanage in stock trim and holset trim last winter purposely inducing fuel cut. Ended up clamping at 4.20 volts because iirc the lowest I got under certain conditions was about 4.23v. Luckily with the emanage you can safely manipulate the ecu above cut using their 3.5 bar map sensor. I wish I had all those logs still. It's become a pain in the anus as of late.
#25
Instructor
iTrader: (5)
Just want to bury this once and for all so maybe people will refer back to some of this in the future instead of posting "oh hey i want to get SAFC is this gud"
Why isn't there a tuning subforum??
You would figure with all the NA-T's and swaps on here running standalones and piggybacks that it would be useful.
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