7AFTE, Tuning Question Options

[celicomx]

I'm currently building a 7AFTE, my question is, go FMU? or SAFC witch 350cc Injectors? I'm going to boost less than 10psi, so any advice is welcome.

[Syaoran]

I think the SAFC will be just fine... I would recommend you do the "gray wire" / "boosted safc" modification if anything. It's much better overall than tuning by throttle position.

http://www.alltrac.net/mods/boostedSAFC.html

This post has been edited by Syaoran: Feb 12, 2012 - 3:35 PM

[celicomx]

I think the SAFC will be just fine... I would recommend you do the "gray wire" / "boosted safc" modification if anything. It's much better overall than tuning by throttle position.

http://www.alltrac.net/mods/boostedSAFC.html

thanks!

[evo_lucian]

No need for bigger injectors when using a fmu. The fmu is meant to be used with stock injectors and it simply bumps the fuel pressure by a preset ratio for every psi of boost . So for example if you buy a 5:1 fmu and you have a base fuel pressure of about 40 psi, for every lb of boost your fuel pressure will go up by 5 psi .

0 psi boost = 40 + (0 x 5)= 40 psi fuel pressure
1 psi boost = 40 + (1 x 5)= 45 psi fuel pressure
5 psi boost = 40 + (5 x 5)= 65 psi fuel pressure
7 psi boost = 40 + (7 x 5)= 75 psi fuel pressure

Safc is a good cheap device if you on a budget but it has a really bad disadvantage. When you use bigger injectors and a safc to trim , everytime you take off fuel through the safc the ignition timing actually advances which is very bad. The more trimming you fuel injectors need the more you timing is advanced.

My suggestions if you cannot afford a proper standalone or proper piggyback (AEM FIC).

Option 1 : Fmu and better fuel pump on stock injectors.

Option 2 : 2 bar Toyota map sensor + fuel injectors approx 2x the size of your stock injectors and a good fuel pump.

[celicomx]

No need for bigger injectors when using a fmu. The fmu is meant to be used with stock injectors and it simply bumps the fuel pressure by a preset ratio for every psi of boost . So for example if you buy a 5:1 fmu and you have a base fuel pressure of about 40 psi, for every lb of boost your fuel pressure will go up by 5 psi .

0 psi boost = 40 + (0 x 5)= 40 psi fuel pressure
1 psi boost = 40 + (1 x 5)= 45 psi fuel pressure
5 psi boost = 40 + (5 x 5)= 65 psi fuel pressure
7 psi boost = 40 + (7 x 5)= 75 psi fuel pressure

Safc is a good cheap device if you on a budget but it has a really bad disadvantage. When you use bigger injectors and a safc to trim , everytime you take off fuel through the safc the ignition timing actually advances which is very bad. The more trimming you fuel injectors need the more you timing is advanced.

My suggestions if you cannot afford a proper standalone or proper piggyback (AEM FIC).

Option 1 : Fmu and better fuel pump on stock injectors.

Option 2 : 2 bar Toyota map sensor + fuel injectors approx 2x the size of your stock injectors and a good fuel pump.

Thank you very much!