Lexus AFM Question

NewGen

New Member
Apr 6, 2007
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I'm trying to decided if what I got was a true lexus afm or if i just got riped off. The problem i'm having is the cars still fuel cutting at 15psi, That might be normal i'm not sure maybe someone can tell me. I'm running stock injectors and yes i know that i'm way over powering them with an apexi safc 2. So the next thing on my list is new injectors. Is there anyways to tell by looking at the maf?

thanks

matt
 

hellraiser456

New Member
Dec 29, 2006
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well the lex afm is bigger(physically) to the supra one....just compare the two and you should be able to see right away as they are very different in size.

Do you have a WBO2?
 

hellraiser456

New Member
Dec 29, 2006
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if you are going to use the lexus afm and NOT upgrade the injectors....you will need to be able to tune...and thus a wide band oxygen sensor is almost necessary...aside from lots of dyno time.

The point of adding the afm and injectors was because both were about 25% bigger than stock. so in other words...because you are increasing the amount of air coming into the engine by 25%...you will need 25% more fuel. Now because the electronics are the same...the ecu doesn't know the difference between the two....and that is why the injectors were necessary...because the computer wouldn't compensate for the extra air(more unmettered air is allowed to pass before the sensor triggers fuel cut). the consequence is you will run extremely lean.
lexusvsstock.jpg


There is a lex afm compared to the stock one.

if you do have a lex afm...i would check to insure you have no boost leaks.
 

NewGen

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Apr 6, 2007
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I have an aem wide band and i'm running an apex safc II. K I think it is a lexus afm then. I just havnt had time to pull it off to compare.
 

NewGen

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Apr 6, 2007
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its alittle lean. I've been taking it easy at the moment. it bounces back and forth from 12-13 then after a second will drop to 10.5. Its kinda odd but i think its probley just because my injectors are to small. Another question maybe you can answer. My cars how having idleing problems. I'm thinkin it could be my altornator because my battery is lit up very dimmly. It also has problems when you let off from cruizing it just tries to die. I dont maybe a boost leak to?
 

Shytheed Dumas

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Mar 6, 2006
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NewGen said:
I have an aem wide band and i'm running an apex safc II. K I think it is a lexus afm then. I just havnt had time to pull it off to compare.

You should have noticed when you installed the Lex. I had to heat the end of the accordian hose in warm water to get the larger diameter fit. Stock AFM slides right in.
 

jtran8

Supramania Contributor
Mar 29, 2007
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wichita kansas
what turbo are you running ? i'm running 17psi on 57trim + lexus afm/550cc and not anywhere near fuel cut . some people run 22psi on 57trim don't even get fuel cut . sure you have big boost leak some where , unless you're running big ass turbo or 450rwh . wideband meter will tell you all.
 

bountykilla0118

In Pursuit of 500rwhp
Jul 16, 2005
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You can not be a mechanic. What do the injectors have to do with you hittin boost cut? I have an idea search and here is the hit "AFM" and the type we have is called a karman vortex ......

People are making 400+rwhp on the stock 440's.

found something .... i searched yahoo for 7mgte karman vortex and after a few second i found this

http://www.novogate.com/exco/thread.php?forumid=15002&threadid=103821

Myth 6:


Fuel cut woes

Fuel cut, or technically ignition cut is a protection system used in the 7M-GTE and numerious other Toyota
engines. Unless we get information directly from the Toyota development team who designed and built the
7M-GTE, no one really knows the precise reason why fuel cut was implemented and why it triggers at certain
boost and RPM levels.

One reasonable purpose of fuel cut (actually ignition cut) is to circumvent excessive turbo boost pressure.
This will protect the turbo from reaching excessive PSI levels in case the actuator or related parts fails.

Many would argue that the conditions that trigger fuel cut is set in relation to capacity of the stock
440 cc injectors. Yet given the known injection duty values and combined with the flow rate of 6 x 440 cc
injectors - the reasoning is preposterous.

Considering that parts fail over time, some kind of mechanism is needed to protect the engine. Toyota has
no legal obligation to allow their production engines produce as much power as the parts allow, but
they do have the obligation that these engines produce the rated 232 HP give or take 5% of this figure, and
that these engines remain fit for purpose through their warantee period.

So this means that fuel cut could have set to be triggered at a lower boost @ RPM level, say for example:
just above 8 psi @ 5600 RPM had Toyota wanted to, although it doesnt mean that the engine cannot handle the
extra PSI boost level, more likely to the reality that not all actuators and wastegates, CT-26 units,
intercoolers, the pipework, air flow meters of the thousands of 7M-GTE's out there all function exactly the
same, some reasonable tolerance needs to be applied to take this into account.


Fuel cut often is triggered when the AFM values x RPM + air temp & altitude readings accumulate past a
set point seen in the ECU. Often people would think fuel cut is merely triggered by boost, but that is not
the case otherwise 13 PSI would trigger fuel cut as soon as these pressures are reached regardless of what
gear and RPM you are in.

It is important to realise this "trigger value" whenever using the Toyota ECU at any state of tune. The
most extreme examples of modified 7M's using the standard management system often manipulate the AFM signal
as far as it can, this is the only parameter that can be reasonably adjusted without causing running problems
and avoiding fuel cut at the same time.