Will adding 550's raise fuel cut?

[twinturbozs]

I have a lexus AFM and thought i installed a set of 550's. i bought them used, but now im wondering if they were actually 550's and not stockers. Im getting premature fuel cut. So will 550's help raise fuel cut? or will the stock 440's contribute to premature fuel cut?

 

[Shytheed Dumas]

Lex should have eliminated fuel cut if I'm not mistaken.

 

[twinturbozs]

I understand that, but im looking for an answer to my original question thanks.

 

[Shytheed Dumas]

I guess I didn't follow your original question... You said you have a Lex AFM, and even with 440's you should not hit fuel cut. Should I have understood that you haven't installed the Lex?

 

[steven89]

Lexus AFM doesn't eliminate fuel cut, it raises it. To my understanding, because of the bigger area for unmetered air to pass through.

So for this problem, if hes still on 440s. More air, not enough fuel for it. [someone correct me if im wrong]

 

[Shytheed Dumas]

I've got a Lex AFM with 440's and the warning I had was to be sure to keep my boost down under about 12 - 14 psi, because "fuel cut is gone" (well at least as far as running safely goes on that size of injectors).

The idea of going to 550's is not because they will raise fuel cut (Lex took care of this already), but because they will be capable of delivering enough fuel to keep from reaching dangerously high a/f ratios - especially if coupled with an upgraded fuel pump. This is how I understand it, but I may need to be corrected too.

 

[CarlosPTR210]

I have a lexus AFM and thought i installed a set of 550's. i bought them used, but now im wondering if they were actually 550's and not stockers. Im getting premature fuel cut. So will 550's help raise fuel cut? or will the stock 440's contribute to premature fuel cut?

The Lex is 25% bigger, so the ECU don’t measure around 25% of the incoming air, so that why the fuel cut change from 12 to 22psi in some causes. But you need to be sure that install a 550cc injector to compensate the 25% more air. You need to check the flow rate before use them.

If you are not sure of your injectors flow, you will kill your engine. Like me

My solution, buy an RC 550cc injectors.

Also is better to use a wide band OX sensor to verify your Air fuel ratio

I suggest the following:

Send the injector to flow

Search for any air leak

Use a wide band OX to verify you’re A/F under boost.

I hope find your problem before is to late!

By the way, sorry for the grammar !

 

[The1]

From my understanding, I thought that the Lexus AFM raised fuel cut to 21psi but keeping the stock injections would mess with the Air/Fuel ratio, still making it a pain to drive...but I may be wrong. *shrugs*

 

[CarlosPTR210]

From my understanding, I thought that the Lexus AFM raised fuel cut to 21psi but keeping the stock injections would mess with the Air/Fuel ratio, still making it a pain to drive...but I may be wrong. *shrugs*

Nop that true, at lest need to rise your fuel presure but is not tthe best way, I sugest install the stock AFM, buy a 550cc inyector thae install all and thats it!, oh! and don't forget the tune :biglaugh: .

 

[twinturbozs]

Guys, please keep with the topic on hand. We all know that the lexus afm raises fuel cut, we also know that it should be run with 550's.


Im asking, if for some reason i have 440's and lexus afm, will it have a lower FC point than one of 550's and lexus AFM?

 

[Shytheed Dumas]

The idea of going to 550's is not because they will raise fuel cut (Lex took care of this already)

If the 550's aren't going to raise FC, then 440's shouldn't lower it either. I.e, injector size does not influence fuel cut. If this isn't right, please feel free to correct me.

 

[GrimJack]

Guys, please keep with the topic on hand. We all know that the lexus afm raises fuel cut, we also know that it should be run with 550's.


Im asking, if for some reason i have 440's and lexus afm, will it have a lower FC point than one of 550's and lexus AFM?

No. The fuel cut point will be at exactly the same point, your injector size alone has no effect whatsoever on fuel cut.

 

[bowsercake]

^^^ Correct.

To add to that the reason that you run the 550s instead of the 440s is because the 440s will run very lean while the 550s will run a little rich. The 550s A/F ratio can be corrected with an after-market Fuel Pressure Regulator or better yet, some sort of air correction computer (SAFC, Emanage, MAFT).