Few simple Lexus AFM questions

[CyFi6]

I just have a few simple questions regarding the Lexus AFM upgrade. I know a lot of people have done this upgrade, so I figure there will be a lot of input.

A list of my current mods to begin with...
Walbro 255LHP pump
Denso 550CC injectors pnp
Aeromotive FPR
3" exhaust
57trim CT26
2.5" Intercooler piping/larger intercooler
MAFT Pro Speed Density Conversion


To start off, I am currently running 550CC Denso plug and play injectors (from rx7) and the MaftPro with speed density conversion for tuning. I am running about 14 psi.
I have been on this setup for approximately 2 or 3 years, and ever since the day I put it in, I have been fighting with it to achieve exactly what I want. My NUMBER ONE priority at this point is drivability, power is lower on the list. With my current set up, I have been unable to achieve like-stock drivability, and I am fed up with it. No more do I want hesitations between shifts, stumbling at idle/returning to idle, random hiccups or any other issue that I do run into with this setup. I want my car to run like it did before I installed this system, which was perfect, the only difference is I want to raise my fuel cut.


1. It seems that the Lexus AFM+550 mod will get me where I want to be. Upon searching, I have found both instances where drivability was retained just like stock, and others where it was not. What is the overall consensus? With a properly set up Lexus AFM+550 injector setup, would one be able to tell the difference between that and a completely stock vehicle, drivabilty wise?

2. Is there a necessary difference between the LIPP AFM vs. the regular Lexus AFM? Research tells me that both have an adjustment screw to get the idle perfectly adjusted, but the ad for the LIPP AFM says that only the LIPP afm has an adjusting screw, who is correct?

3. Is there any difference between running a Lexus AFM mod and using a simple tuning device such as an SAFC to dial the airflow signal back 25%? In other words, instead of having a Lexus AFM, could one use a tuning device and stock AFM and achieve the exact same outcome? Does the size of the stock AFM restrict airflow to the point of a problem arising when running higher boost? Can the stock AFM accurately measure the increased amount of airflow?

 

[Backlash2032]

For #2 I'm pretty sure factory Lex AFMs have an adjusting screw. It might be hidden, but I'm pretty sure they do.

 

[grimreaper]

lex afm is physically larger ID then stock. Not sure if your wire harness is newer but rebuilding the wiring harness made a very noticeable difference in drive-ability. All of the wires running over the top of the valve covers where rock hard and heavily corroded when stripped on mine. This is with 100K on the harness.. zero idle stumble as well with stock coils and ignitor.

The maft pro benefited me quite a bit by tunning under the curve to give the ecu what it wants to see. Tune Vf's from idle to + boost and see if it improves. Keep transitions very smooth from one column/row to the next. High way driving makes this extremely easy but time consuming. After any changes are made, you must allow a few miles for the ecu to relearn and stabilize. Doesnt take to long though..

 

[jetjock]

Tweaking in closed loop? Shouldn't be able to.

 

[grimreaper]

^ adding or removing fuel to get the VF at 2.5v or close across the board. Not real closed loop tweaking by definition. Basically filling in bits on the maft pro fuel map to have it match what the stock ecu would expect to see from a stock afm.

 

[CyFi6]

Its little things. Keep in mind I am picky. I find there is not enough resolution in the VE table to get a really accurate tune. One example...I get a slight hesitation on light acceleration at a particular RPM/gear. The AF gauge is at 14.7 or so as I increase in speed and at the particular point where it hiccups the gauge spikes lean for a fraction of a second. OK so I go into my VE table and richen up the mix right at this point, still does it, richen more, still does it, but better, richen up a little more. OK now it seems like its mostly gone. Now I am cruising at the same RPM where the hiccup was in a different gear... gauge goes rich and VF goes close to 0v. I look in my table and what do you know, I am in the exact same cell that I was in before when I had the acceleration hesitation. This is just one example...

Another example... Sitting at the light with the AC on, AC cycles off, AF gauge goes lean and engine runs rough for a few seconds. Cant adjust this because it didn't even move cells from the rough running to normal idle. If I adjust to fix the rough run on AC kick off, then my regular idle is all screwed up. Also, I find that VF fluctuates a lot based on conditions such as outside temperature, and other times for no reason at all. I can have perfect 2.5v to 3.5v VF one day and under the exact same conditions have 4.0v the next day. I can do multiple pulls and each pull the WOT A/F ratio will be slightly different because of changes in intake temps or sensor heatsoaking or whatever the case may be.
Regardless, I tried setting up the user defined axis ve table to get more resolution but when that failed to work properly it was kind of the last straw. It seems that trying to generate an AFM signal from a map sensor and air temp sensor just does not work perfectly.

Keep in mind I have tried my hand at many of the features in the MAFT Pro such as part throttle tracking, where basically you disable fuel control for the TCCS and hand it over to the wideband and MAFT. This was a JOKE at best as there were HUGE delay times (im talking multiple seconds) and the ECU would over correct/overshoot the target. I don't see how this would be useful for anything besides driving the car from a trailer to the starting line.

I don't want to turn this thread into a discussion about the MAFT however, so I am still looking for help regarding the original questions.

I also suspected that the harness was the culprit, and rebuilt it last time I had the engine out which was around 10k miles ago, maybe a little more. Every connector on the harness is either brand new or in good shape. I found the same thing when I cut open my harness, the corrosion when so far back I couldn't believe it. I cut wires back and ran new lengths or wires to sensors where needed. It made little to no difference in the end result.

 

[89gte]

Lexus afm or HKS VPC w/ SAFC and datalogging capable wideband

 

[3p141592654]

There's a reason you don't see speed density on production automobiles any more, and they were only ever on the low end models even back then.

 

[mecevans]

Nothing wrong with speed density, MAF is just more accurate. Honda used it forever. In fact most all new cars have MAF AND MAP for tighter fuel and emission control.

What you need to do is tune the Lex AFM as best as possible, then use the piggyback for minor changes. The less you use the piggyback the happier the PCM will be.

BTW did you ever solve your missfire. Even a slight miss will make the car run like crap. Your best bet it to backprobe inputs at PCM and outputs at the other end. You could spend hours going through the harness and never find anything.

 

[jetjock]

It's the least accurate way and the fact Honda used it on their little POS cars is nothing worth bragging about...

 

[mecevans]

It's the least accurate way and the fact Honda used it on their little POS cars is nothing worth bragging about...

It gets the job done. The Maftpro is not the culprit here.

 

[jetjock]

So did carbs.

Neither of us can be sure but I think it is the problem. Or more accurately it's operator head space error...

 

[mecevans]

In a prior thread he had an issue with a slight misfire before and after installing Maftpro.

Personally, im waiting on 3p's pcm mod.

 

[CyFi6]

I have not solved the misfire yet, there are multiple problems here, but the Maft has so many hands in the thing at this point that I feel it will be much easier to solve the problem once it is gone. For instance, the Maft receives the TPS signal from the TPS and recreates a new signal for the ECU (For part throttle boost). It also interrupts IGF and recreates an IGF signal for the ECU so that it can have control of timing. Some of these things are complicating the issue. I do not believe that the slight miss under light loads is causing my drivability issues. Anytime there is a load on the engine, the miss is non existent. It seems to be more of an issue of the ability to get a 100% proper tune.

Besides these facts, I am unhappy with the MaftPro and want to go to something more reliable and more accurate. The point of this thread though is to figure out whether or not the Lexus and 550 mod is something that matches my needs. If not I am willing to go back to completely stock fuel and AFM, but it will just suck to have to sacrifice power for drivability.

 

[mecevans]

Then in that case, I agree with Jetjock. Rip out the maftpro or set everthing to zero if possible. Lex AFM and 550's and use fuel pressure and air screw to get it as good as you can get.

 

[Poodles]

If you want more accurate and tunable, there's only one answer...

 

[CyFi6]

That's just it. I don't want to get myself involved in more of a tuning nightmare unless I know for sure that it is proven to work and work well.

Good drivability means different things to different people. I have gotten in other peoples cars and they say it runs great, yet the thing is misfiring at idle and running rough. Like I said earlier I tend to be picky and I want my mother to be able to jump into this car and drive it as if it were a completely stock Supra and not notice a single difference or annoyance (well, getting my mom to drive a Supra would be a completely separate issue).

Thank you for everyone offering input, it is appreciated.

 

[CyFi6]

If you want more accurate and tunable, there's only one answer...

Are you suggesting standalone? As far as standalones go, I have never seen any in person that have enough adjustability to make a Supra run like a brand new Supra off the showroom floor driving around town. From what I understand, the amount of time and effort put into the stock ECU is superior to any aftermarket computer. Keep in mind I don't have a lot of experience with standalones so maybe I am just naive. And keep in mind this is a sub 400HP car so I am not looking to spend more on the computer than the total value of the vehicle itself lol.

 

[mecevans]

Standalone or piggyback will never have the reliability of the stock PCM. Thats why I'm waiting for 3p's mod.

 

[Nick M]

A list of my current mods to begin with...
Walbro 255LHP pump
Denso 550CC injectors pnp
Aeromotive FPR
3" exhaust
57trim CT26
2.5" Intercooler piping/larger intercooler
MAFT Pro Speed Density Conversion

You don't need an adjustable fuel pressure regulator at your power level and modification with the Lex meter. I bought a new Toyota FPR (I figured 20 years was long enough) and have done nothing else to it. Of course, the car is maintaned proffessionaly...by me.

I have been on this setup for approximately 2 or 3 years, and ever since the day I put it in, I have been fighting with it to achieve exactly what I want. My NUMBER ONE priority at this point is drivability, power is lower on the list. With my current set up, I have been unable to achieve like-stock drivability, and I am fed up with it. No more do I want hesitations between shifts, stumbling at idle/returning to idle, random hiccups or any other issue that I do run into with this setup. I want my car to run like it did before I installed this system, which was perfect, the only difference is I want to raise my fuel cut.

In my professional experience, "tip in" issues are A/F, and not ignition/timing. However, testing still has to be done with each issue.

1. It seems that the Lexus AFM+550 mod will get me where I want to be. Upon searching, I have found both instances where drivability was retained just like stock, and others where it was not. What is the overall consensus? With a properly set up Lexus AFM+550 injector setup, would one be able to tell the difference between that and a completely stock vehicle, drivabilty wise?

I wondered about it also, having read peoples problems and how they want to throw it in the toilet. On paper it should work, and it did. But then again, my car didn't have anyting else done, like adjusting fuel pressure away from stock.

2. Is there a necessary difference between the LIPP AFM vs. the regular Lexus AFM? Research tells me that both have an adjustment screw to get the idle perfectly adjusted, but the ad for the LIPP AFM says that only the LIPP afm has an adjusting screw, who is correct?

Toyota produced meters have the adjustment screw, but it is blocked off. I have an original 1UZFE meter and the LIPP meter. They are identical to the naked eye.

3. Is there any difference between running a Lexus AFM mod and using a simple tuning device such as an SAFC to dial the airflow signal back 25%? In other words, instead of having a Lexus AFM, could one use a tuning device and stock AFM and achieve the exact same outcome? Does the size of the stock AFM restrict airflow to the point of a problem arising when running higher boost? Can the stock AFM accurately measure the increased amount of airflow?

HKS used to sell things that would do just that. It would scale the airflow meter by large amounts. Be careful.

Tweaking in closed loop? Shouldn't be able to.

He has jacked up at least one radiator cap that I know about.

Its little things. Keep in mind I am picky.