Why is an SAFC II such a bad Idea with a Turbo Neon

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mahifish
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Why is an SAFC II such a bad Idea with a Turbo Neon

Post by mahifish » Wed Apr 30, 2008 11:09 pm

I have read countless threads and have had people backlash on me when I mention using a SAFC to tune my car when I go turbo. I never got a good response as to why. I have tuned 5 or 6 turbo'd cars with a wideband and SAFC.

So my question is Why is a SAFC II not going to work well on a boosted neon?

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Post by 6(sic)6 » Thu May 01, 2008 2:14 am

Dunno, prob most just go with MS. It IS the way to go :)
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Post by DOHCRT » Thu May 01, 2008 7:34 pm

It works ok on a lot of cars, just not the neon. One of the biggest problems is that the more fuel you take away with the SAFC, the more the PCM advances timing. Thats bad for boost. Real bad.

Another issue you run into is trying to get the engine to idle properly with big injectors and stock fuel pressure. In order to do this, you again have to pull fuel with the SAFC. The problem is that the MAP is already reading low kpa, and clamping the voltage lower causes it to be out of range. The PCM will never get a correct barometric pressure reading because of the same problem.

The ideal setup is to use an SAFC in conjunction with an FMU. The FMU will tune the basic fuel needs, while the SAFC can be used to "fine tune". I ran this setup for a while until I switched to MS.
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Post by 1fast2liter » Thu May 01, 2008 11:09 pm

a safc is ideal for a all motor car. but turbo cars with mass flow sensors work the best with them.....when the neion goes in to closed loop ie cruise it uses pre burned maps and ignores the safc... in boost and cruise thats bad. a 1:1 or if you use a rrfpr then you dont really need it just a wideband and a quality rrfpr and say a set of stage 0 injectors. ms would be the best way to go. but a rrfpr and stage 0 injectors would do. this is one area that you dont wanna skimp in.. you mite go boom.
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Post by Armstrong57 » Thu Aug 14, 2008 11:23 am

SAFC tunes fuel by rpms, not by boost. You want to be able to control fuel as it pertains to boost levels.
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Post by mahifish » Thu Aug 14, 2008 4:55 pm

Armstrong57 wrote:SAFC tunes fuel by rpms, not by boost. You want to be able to control fuel as it pertains to boost levels.
I've tuned many boosted cars with an SAFC, it doesnt tune by the rpms you control the amount of fuel pertaining to your AFR. I usually use a wideband and tune it at full throttle. It will run rich when your not at full throttle but its much safer then running lean.
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Post by Armstrong57 » Thu Aug 14, 2008 6:01 pm

Exactly...full throttle = xxxx rpm. So at that rpm you are pulling x amount of fuel. Has nothing to do with boost levels at all, and that's a pretty poor way to properly tune a boosted car.

Running rich enough not to blow the engine doesn't mean it's done right.
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Post by DOHCRT » Thu Aug 14, 2008 9:20 pm

Its basically alpha-n (RPM specific) tuning. The SAFC has no way to tune the difference between 5 pounds of boost and 15 pounds. It adds or subtracts the same amount of fuel regardless of manifold pressure. Since we obviously need more fuel at 15psi than we do at 5psi (at the same RPM, of course), you can see why the SAFC can be less than desirable.

The unit does, however, have the ability to adjust its tables based on throttle position. This is a way to infer manifold pressure at part throttle boost. Not a very accurate way, but it works to some degree.

There have been many people to do the "AFC hack" install. This is just wiring the SAFC up so that the MAP sensor is hooked to the units throttle position input. As manifold pressure changes, the SAFC sees it as a varying throttle position and adjust fuel accordingly. A high MAP reading would make the SAFC switch to the "high throttle" table.
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Post by mahifish » Fri Aug 15, 2008 5:18 pm

I've never ran over 7 psi with the safc tune. Worked great for the two months I used it. It wasnt permanent and I still put out 315 hp on a 1.9 GM motor.
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Post by Armstrong57 » Tue Aug 19, 2008 12:15 pm

You can tune the car with the SAFC, and it may be safe enough to run, but it won't be optimal. If you got that much hp tuning with SAFC alone, I'm sure you could get even more (and more stable) with the proper tuning method.

If it's working for you, do it! But all we're saying is that it isn't the most optimal way to do it for a boosted setup :)
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Post by mahifish » Tue Aug 19, 2008 4:24 pm

I knew that, thats why I went with MS. I just had a hard time finding out where I could get MS for this motor.
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Post by wesker » Wed Sep 10, 2008 12:00 pm

i have a 01 motor with a 63 trim 12 psi turbo,a fpr set at about 40-45 psi,a 10:1 fmu and missing link,450cc injectors ,255 wabro pump,spoolboy modded cannister and return line,and a safc.is that a reasonable set-up?

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Post by DOHCRT » Wed Sep 10, 2008 12:14 pm

wesker wrote:fpr set at about 40-45 psi,a 10:1 fmu and missing link,450cc injectors
Thats way to much base fuel pressure and way to high of a rate of gain for those injectors. You need about 10 - 20psi base fuel pressure with a rate of gain in the range of 4:1 to 6:1.
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Post by wesker » Wed Sep 10, 2008 1:28 pm

could that be why im smoking now.a guy on neon.org told me 49 psi on the fpr and a 10:1 fmu.im taking out this engine a putting a low,low mileage 95 motor in it.i want to do it right this time.

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Post by Ladi3sman55 » Wed Sep 10, 2008 4:33 pm

wesker wrote:could that be why im smoking now.a guy on neon.org told me 49 psi on the fpr and a 10:1 fmu.im taking out this engine a putting a low,low mileage 95 motor in it.i want to do it right this time.
get a rebuild kit from modern
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