Trying Lexus AFM with 440's on stock CT26 for benefit of community

[jboyle83]

Ok guys, before the "gotta use 550's" flaming begins, please read what I'm doing here.

My inspiration comes from the older articles I read of the guy who ran this setup in multiple cars including a Celica with a 7m swap (cannot remember his name or the link for the life of me), and iirc even with a 60-1 CT. If anyone can pass that link to me it would be much appreciated.

I am doing this as safely as possible with my setup. I am using a wideband to watch my A/F's and have all supporting mods (ie... FMIC, Full 3" exhaust, AFPR, etc.) on top of forged internals and MHG/ARP's. I will be sending my CT26 off to Aaron in a couple months for a 57-trim build and will be going to EVO 560's and MAF-T Pro at that point. But I wanted to get an idea of what numbers and the saftey of doing this as so many people jump on the "don't do this" bandwagon from nothing more that hear-say.

I made a few pulls this morning to get an idea of what kind of boost and FP will be do-able with this. I began with 43psi base FP. As of my last pull I have it hitting around 14psi and falling to around 10-12 by redline. The AFR's are starting somewhat lean 13ish while building boost <7psi at but are then richening up nicely as boost climbs settling at 11-11.3 at WOT and full boost. This is generally the same area I tend to tune my cars to when using a piggyback setup, and am extremely happy that I have gotten these with nothing more than an AFPR. It does idle a decent bit leaner (15.3 ish as opposed to the 14.5 it did prior to the AFM).

I will be tweaking this over the next few days and take it to our local 1/8 mile drag strip to see how she does.

Feel free to ask an questions, or make a comment.

 

[hvyman]

Buddy melted a piston at 17-18psi without 550's.

If your monitoring it you can be somewhat safe but then again your running high fp through 20 year old injectors...

 

[jonahs_supra]

i bought a 90 supra a few months ago...mainly for parts
i began parting it out and found it had a lexus afm housing with stock injectors
catless exhaust and everything else was stock
actually pulled pretty good

but idk what the afr was

 

[87targa]

awesome info. it would be interesting to see the duty cycle.

 

[Nick M]

Why are you even trying to see what you can get away with? Why not just do it right?

 

[IJ.]

A bud here did this way back, cranked base pressure then pulled fuel as needed, it works but you have 0 room for error and the slightest hitch in fuel delivery will melt down your engine... :nono:

 

[Dan_Gyoba]

I remember that guy from the supras.com mailing list. He fought rather hard for the 440s being adequate with the Lexus AFM, and did a lot of data collection to prove his point, on the basis that the TCCS wants to run way too rich in the first place, and that more power was available at a leaner AFR. (Can't remember his name at the moment either.)

Yeah, he got away with it, and other people following his example did too. Except some who did not. There were a lot of reasons given why those who melted a piston had done so. They didn't monitor EGTs close enough, or they didn't do something, or they reset the ECU's learned fuel curve and didn't allow time for learning before putting the hammer down...

There was an awful lot of data collection done, and those with actual knowledge never accepted that this was anything better than a crap shoot which might not blow up your engine so long as nothing went wrong.

Really, if sticking with the stock 440s is what you want, just get an HKS FCD instead of the Lexus AFM. It's safer.

 

[jonahs_supra]

Oh and that car I purchased for parts also had a rod knock and smoked a lot
Lexus Afm with stock injectors was probably the main reasoning for the motors issues

 

[7MGTEsup]

The guy you are thinking of is John Lunsford here is a link to his site. http://www.jblmk3.com/

 

[speedfreak426]

I also have a celica with a 7m swap, I ran a 57 trim CT with 440's for a while at 15ish psi. It ran amazing, I just bumped up the fuel pressure a little bit. It ran better with the 440's than it did with 560's...
AFR's were 11.2-11.4:1
Never had any issues, until I switched to bigger injectors



I am now running a megasquirt so I got rid of the AFM altogether... 560's with 18psi on a HY-35 Holset now

 

[Suprapowaz!(2)]

supras.com mailing list.... John Lundsford... Old school right there.

I'm still a Member on supras.com. http://supras.com/06/members/viewmember.php?memberid=523

I'm old school. Anydody else a member there?

 

[gsxr141]

wow. after reading what mr lunsford did with the 440's, it seems like for anything under 400hp the 550's would be overkill. it's definitely an interesting read.

 

[Poodles]

Keep in mind the main reason things like that were done in the old days (along with extra injectors) was because custom injectors either didn't exist or were extremely expensive. These days it's a totally different story...

 

[Nick M]

It ran amazing, I just bumped up the fuel pressure a little bit. It ran better with the 440's than it did with 560's...

At lower power levels, you don't need that big of an injector. If yours ran bad, you had other problems. You do need the bigger injectors with the different airflow meter, which is what the question is.

AFR's were 11.2-11.4:1

That is risky with cast pistons.

Never had any issues, until I switched to bigger injectors

Then you had something wrong or did it wrong, as 550's on a stock engine won't change anything.

 

[Dirgle]

I think there is a fundamental misunderstanding as to why Reg chose the 550 injectors for this mod. It was not to have bigger injectors for more duty cycle head room. It was to have an comparable increase in fuel flow to match the increase in air flow. This preserved the scaling for the fuel tables in the TCCS.

With the Lex AFM there is somewhere in the neighborhood of 25% more air is entering the engine, at any given time, that the TCCS does not know about. With the TCCS metering out fuel to what it thinks is a 440cc injector, when it is actually a 550 you get the 25% increase in fuel. Keeping the scaling the same means the fuel maps remain correct, and the TCCS is better able to deal with other changes. Running 440's with the Lex throws things out of whack, The TCCS may be able to adjust, but it's flying blind and the margin for error is really small.

 

[Dan_Gyoba]

I'm still a member on supras.com.

@gsxr: And I still maintain that an FCD is still safer than the Lexus AFM, since it doesn't mess with the TCCS learning function. Putting on the Lexus AFM is putting on a part that is WAY out of spec. The learning function is there to allow for parts to be out of spec somewhat and it will adapt. JBL got away with what he was doing, and made some good power. Other people followed his example and also made decent power. His story is that if everything is in the kind of condition that it needs to be in to make that power, it'll be fine. Some people thought that they were at that point, but broke stuff. Maybe they would have broken stuff anyway with the 550cc injectors, but I'm thinking that at least some of them wouldn't have.

I'm NOT a gambler by nature. Though there's always increased risk with any kind of power adder, if there's a safer route, I'd rather take it.

 

[gsxr141]

cool. i have a lex afm, walbro 255, an afcII, and 560's right now. the injectors actually flowed around 620. i was waiting to get a afpr before i install everything. i also have a fcd that i could use right now.
i'd be happy to get 10-12psi out of it before hitting fuel cut. i just took it out on the highway and it was holding 10 steady. it pulled hard and never hit fuel cut.
as soon as i tried to go from a light, it hit fc in 2nd and 3rd. it's so intermittent.

 

[Poodles]

FCD was NEVER meant to be used alone. It was meant to be used with the full suite of HKS piggyback controllers. Without it, it's far more dangerous than the lexus AFM...

 

[Dirgle]

FCD was NEVER meant to be used alone. It was meant to be used with the full suite of HKS piggyback controllers. Without it, it's far more dangerous than the lexus AFM...

Very true, the FCD clamps the air flow signal right below fuel cut, irregardless of how much more air enters the engine, the signal will continue to indicate that it is the same as when it hit the set point. What this means is that as you push the boost past fuel cut, the TCCS has no idea how much more air is entering the engine, and only meters out fuel called for by that lower clamped signal. This is a sketchy way of doing things and the only way to keep from running lean is by using a fuel adding piggyback, like one of the HKS piggybacks poodles mentioned. After the signal clamp point the TCCS has no idea how much air is entering the engine, so it is up to the tuner to adjust. And no tuner is as dynamic as the TCCS when dealing with weather and temperature changes. But the Lex/550 keeps the learning and safety features of the TCCS intact. It has its limitations, but it is a far more stable and safe choice than the FCD.

 

[Dan_Gyoba]

For clarity, I would personally never use the FCD. At all, ever.

I would ONLY recommend its use as an alternative the Lexus AFM with the stock injectors. I would ALWAYS recommend the Lexus/550 over the FCD.

The case that JBL made for the Lexus AFM with stock injectors was that it was safe with lots of monitoring, and being really certain what you have. His contention was that the stock system runs so "pig rich" that there was lots of room for more power above that. With either FCD or Lexus AFM, you are basically allowing what the unmolested TCCS would consider an overboost condition to go undetected, with the fuel injectors running at or near their maximum capacity.

In the case of the Lexus AFM with stock injectors, the injectors aren't even at their peak capacity at the point where this overboost begins, so at any and all times in open loop mode the car is running leaner than stock, including the time until the TCCS starts reading the O2 sensor on cold start. In order to even run correctly at part throttle, this absolutely depends on the TCCS learning function and feedback from the O2 sensor. While the TCCS is still learning and adapting, the open loop behavior is inconsistent, and could easily result in an engine running lean even below the FCO point. In otherwords, careful monitoring and maintenance of the system is required to make this work properly. (This is all per JBL's arguments as I remember them.)

In the case of the FCD, up until the point where the FCD kicks in, everything runs as stock. The TCCS doesn't need to learn anything more than what it already did. Plenty of adjustment room for the TCCS to be able to know what fuel it's delivering. At the point where car goes into overboost, the fuel stops increasing, and therefore you start running leaner. At some point, this will increase to dangerously lean, and your motor goes "bang". My point here is that where this happens will NEVER be at a lower airflow amount than the Lexus AFM with stock injectors would be.

Let's look at a few scenarios, consider all to be at WOT, and around 6000 RPM, with a turbo capable of delivering with reasonable efficiency.

8 PSI boost:
The FCD AFM says... Full stock boost. The TCCS delivers apropriate fuel. (Very rich though it is.)
The Lexus AFM says... 25% less airflow than stock boost. The TCCS delivers something less for fuel, at whatever it's learning function has determined.) Maybe a bit leaner.

10 PSI boost: (Just below FCO)
FCD AFM says... Lots of boost, but still okay. The TCCS delivers as much fuel as it can. (Still really rich.)
The Lexus AFM says... Well into boost. The TCCS delivers what it thinks is appropriate with margin for more. Definitely leaner, but still okay.

14 PSI boost: (Definitely into FCO)
FCD AFM says... Lots of boost, but still okay. (Same as at 10 PSI.) TCCS delivers as much fuel as it can. (Less rich than before, but most probably still okay.)
The Lexus AFM says... Boost! The TCCS delivers a higher percentage of its fuel, but not as much as it can. (Probably still okay, but still leaner than FCD.)

16 PSI boost: (Chicken, anyone?)
FCD AFM says... Lots of boost, but still okay. (Same as at 10 PSI.) TCCS delivers as much fuel as it can. (Okay? Not okay? Yikes.)
Lexus AFM says: approximately full stock boost (If I did my math right. Still definitely okay.) TCCS delivers lots of fuel, but I would bet on it not being enough.

18 PSI boost: (Danger Will Robinson!)
FCD AFM says... Lots of boost, but still okay. (Same as at 10 PSI.) TCCS delivers as much fuel as it can (Probably too lean, and bad things will happen.)
Lexus AFM says: Lots of boost, but still okay. TCCS delivers a bit under maximum fuel still because that's what it's being told. (If the FCD was too lean, then this is even worse.)


So, somewhere near 16 PSI of boost, both systems were into the land of detonation. I would argue however that the Lexus AFM system did so sooner. For one, it's been running leaner the whole time, therefore EGTs were hotter, and at ANY point in this scenario, it's always delivering less fuel. Shortly after this, the lines cross, and the Lexus AFM hits FCO. Too little, too late, and didn't save the motor.

So, at this point, the benefits of the Lexus AFM are: 1. Will FCO in the event of a major boost leak. 2. Will lean the fuel curve to potentially make more power at 10-14 PSI boost. The trade-off for this is that you should never push the car to WOT without at least an hour's worth of closed-loop driving after resetting the ECU, since this can cause dangerous lean conditions at stock boost levels.

Again, to reiterate, I would never use either of these setups. I personally have a Lexus AFM with PTE 560cc injectors, with which I am quite happy. I want to be able to get to the 16-18 PSI levels at least on occasion with some security that I'm not going to do really bad things to my motor.