Few simple Lexus AFM questions

[CyFi6]

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.

So in your experience, you have a car that drives like stock? No noticeable difference at any point?

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.

Did you find that the adjustment screw on the LIPP meter was useful? Is there any way to get at the factory screw? I have read the factory screw is also shorter than the one in the LIPP, and doesn't allow for as much adjustability.

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

Not sure what you are referring to. Are you talking about the Fuel Cut Defender? Because that just clamps the AFM output at a certain max value. What I am talking about is scaling the AFM signal across the board to allow the stock AFM to work with the 550's. From my understanding this is scaling the AFM in an electrical way, whereas the Lexus meter does the same thing in a mechanical way, both resulting in timing being affected by the same amount. My only uncertainty is in the ability of the stock AFM/housing to measure the increased amount of airflow accurately.

 

[3p141592654]

I have not seen any plots of the stock AFM versus flow rate. Would love to see that data. Given it is smaller than the Lexus AFM, it seems reasonable that it would have a smaller peak flow rate. I would guess that for flow above some critical value other modes can exist that would cause the meter to lose accuracy. The GM frequency MAFs seem like a good alternative, but they have very different frequency vs mass flow rate curves compared to the KV AFM, and would require recalibrating the ECU algorithms.

The ECU clamps the upper limit on AFM frequency to 3333Hz, but I've never seen it get that high. Fuel cut typical happens around 1600-2000 Hz depending on conditions.

 

[Dan_Gyoba]

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 popped in injectors, swapped in the AFM and started it up. Everything else stock, including FPR, IC, BOV. Never saw an issue with it, but that's only one person, right?

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?

Yes, the Lexus unit has an adjusting screw. It's under a plug which you have to dig out if you want to adjust it. I haven't, though my injectors are 560s, which is just that little bit larger, so...

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?

If the SAFC does exactly that, then I see no difference. For flow potential, I believe that the turbo is going to be the biggest factor here.

Let's say for arguments sake that there's an additional 2 PSI drop in intake pressure at the turbo inlet for the stock AFM vs. the Lexus AFM. Is your turbo running so close to it's limits that making an effective additional 2 PSI of boost for the same absolute manifold pressure is going to overrun it? If so, then yeah, it'll be a limit. I don't think that most of us run our turbos that close to their limitations though.

One day if I'm bored enough, I'll see if I can get a static pressure reading from the accodrian hose on my '90 and compare it to the '89 at the same boost level/RPM. My feeling on the subject though is that the accordian hose itself provides a lot more drag on the intake than the AFM ever will, and if you're worried about intake drag to that level, then keep the MAF-T so you have have a nice smooth pipe from air filter to turbo intake.

 

[Poodles]

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

BS, modern standalaones have much more processing power than the stock ECU. Once tuned, they can be much better than the stock ECU (keep in mind this takes a lot of time and tweaking)

 

[Nick M]

So in your experience, you have a car that drives like stock? No noticeable difference at any point?

Yes, it doesn't hiccup or act weird.

Did you find that the adjustment screw on the LIPP meter was useful?

Yes, and it is longer than the Toyota unit. When I said the same to the naked eye, I was refering to the housing dimensions.

Is there any way to get at the factory screw?

You would have to drill.

Not sure what you are referring to. Are you talking about the Fuel Cut Defender? Because that just clamps the AFM output at a certain max value. What I am talking about is scaling the AFM signal across the board to allow the stock AFM to work with the 550's. From my understanding this is scaling the AFM in an electrical way, whereas the Lexus meter does the same thing in a mechanical way, both resulting in timing being affected by the same amount. My only uncertainty is in the ability of the stock AFM/housing to measure the increased amount of airflow accurately.

Not the FCD, but the other programs. That was the "alphabet tuning" that cost thousands of dollars. Which is why the Lex meter was popular. The PFC-Fcon, is a programable fuel computer. As is the VPC. They are both scaled. And, there was something called the GCC, graphic control computer, which scaled it even more. Of course the point of the PFC-Fcon was a longer pulse width, and the scaling was to fine tune it. Those that made the MAFT-Pro work seem quite pleased with it. I have no real comment on it, other than that.

 

[3p141592654]

BS, modern standalaones have much more processing power than the stock ECU. Once tuned, they can be much better than the stock ECU (keep in mind this takes a lot of time and tweaking)

Well duh! I mean Moore's law has been working for 23 years now. The point would be that the tweaking you refer to is beyond 99% of the tuner shops in the world. You need a test bench where coolant temperature can be held at any value, environmental control of temperature, pressure and humidity, and you need a team of programmers who can work around all the little gotchas to get good drivability and fuel economy, and compensate for all the dumbass antics of the customer base. It should be no surprise that the OEMs keep a tight lid on their ECU IP.

 

[Poodles]

Well duh! I mean Moore's law has been working for 23 years now. The point would be that the tweaking you refer to is beyond 99% of the tuner shops in the world. You need a test bench where coolant temperature can be held at any value, environmental control of temperature, pressure and humidity, and you need a team of programmers who can work around all the little gotchas to get good drivability and fuel economy, and compensate for all the dumbass antics of the customer base. It should be no surprise that the OEMs keep a tight lid on their ECU IP.

Yep, and that extra processing power also allows the ECU to do more by itself instead of set tables. Of course that adds cost that most people here don't want to spend...

It also helps to learn how to tune and do it yourself. Full standalone gives you tuning abilities that a piggyback could only dream of.

 

[Nick M]

I popped in injectors, swapped in the AFM and started it up. Everything else stock, including FPR, IC, BOV. Never saw an issue with it, but that's only one person, right?

That makes 4 that I know of, but wasn't counting.

 

[CyFi6]

Well I ended up going with the LIPP afm and the RC 550s and I am really happy with how it drives. I also have an AFPR so I had to fiddle with that a little at first, but it runs and drives really nice now. There is a conflict between WOT and idle, it seems to run lean at idle while running rich under WOT. When I say lean, it still is in the range of ECU correction, but vf is all the way to 5v. If I crank the fuel pressure up to make idle VF happy, the WOT gets very rich. I still need to mess with the AFM adjusting screw some more and I am sure I can work it out mostly, otherwise an SAFC will take care of it without any issues.

 

[thevork]

^ That is the correct way to set it up. Get the right combination of the afm screw and the base pressure to make the idle/cruise like stock and VF within spec.
Then tune your open loop sutiations with the safc.

 

[Nick M]

MAFT Pro Speed Density Conversion


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?

You don't run MAFT-Pro and the Lex meter. It is an either/or mod. A consensus doesn't make something so. There is nothing wrong with the mod, if the correctly sized injectors are used. Problems with the mod are with the install, or the car before the mod.

 

[grimreaper]

you can use the maft pro just like the safc and keep the lex afm. It can use quite a variety of air flow meters including custom voltage units. There is a table to map out the flow vs voltage in the software.

I think the biggest difference is that 10+ years ago when the lex afm and 550's where the main 'tunning' device, everything on the car was in better shape. The other issue is perspective. The definition of driveability varies from one driver to the next. Also makes you wonder about the standalone ecus. One guy theoretically has to replicate what manufactures spend who knows how much time and money on. The reason it works so well is only one person has to be appeased instead of a global population.

 

[Dan_Gyoba]

Personally, it seems to me kind of a waste to use the MAF-T Pro with the AFM, and not go to a MAP based solution.

Using one of these, or a standalone, the idea is supposed to be that you are tuning for your specific car, and not a range of manufacturing tolerances for a large number of components. That's the way that a standalone, or even a piggyback can make the car run better, right?

 

[Nick M]

If your idle seems lean, adjust the screw in further. It is a bypass chamber where the air is not metered. Toyota stock tune is very rich in boost in lieu of forged pistons.

 

[jetjock]

As long as it's not into lean misfire leaner than stoich at idle isn't a bad thing.

 

[CyFi6]

Random question...If my wideband shows air fuel switching back and forth between 14.2:1 and 14.5:1 with engine speed increased, is it safe to assume my wideband is incorrect, considering the engine will only switch back and forth above and below 14.7:1 which is a product of the zirconium sensor? In other words, the ECU will only switch above and below exactly 14.7:1 because the zirconium sensor by nature acts as the graph shows on page 21 here (http://www.autoshop101.com/forms/h24.pdf). So if my wideband is showing switching above and below 14.3 does that mean my wideband must be slightly inaccurate? I have calibrated the wideband according to instruction and it is manufactured by NGK.

 

[jetjock]

The WB is probably slightly off. Not the best instrument to use for checking stoich.

Either that or the engine really is a bit lean. What is the average voltage of the NB taken at Ox or Vf over a few minutes at a steady 2500? Unless it's 450mv or 2.5 vdc the engine is not at stoich even though cross counting is occurring. This is also a way of checking for small vacuum leaks.

 

[grimreaper]

Personally, it seems to me kind of a waste to use the MAF-T Pro with the AFM, and not go to a MAP based solution.

Using one of these, or a standalone, the idea is supposed to be that you are tuning for your specific car, and not a range of manufacturing tolerances for a large number of components. That's the way that a standalone, or even a piggyback can make the car run better, right?

I agree with your point for addressing specific setups. My car would have a standalone if the setup was a bit more extreme. I'd have to accept the trade off though of the potential issues that would bring. I just cant see how its possible to replicate what the OEM tuning can offer in terms of reliability, redundancies and flexibility. (flexibility in terms of climate, driving conditions, fuel, geography etc..) WOT tunning is a small percentage of where most cars spend there time. Everything else under the curve is where you'll spend all the time and money.

Take into consideration aftermarket and OEM failure rates on parts. 1% warrantied failure to an OEM will have a much larger impact then 1% to an aftermarket company. Id expect OEMS to avoid the failure where as aftermarket may be inclined to simply accept it.

 

[Nick M]

I was going to say the WB and stock sensor don't know what 14.7 even is. That is interpreted data. On the older sensor, like stock, you are going to see 450 mv (average), switching quickly when warm. Toyota WB's, they were calling A/F sensor when I was there, was 3.3v. And leaner increased voltage, not lower voltage. And it doesn't switch, becauase the catalyst was being updated.

 

[jetjock]

People often forget all an O2 sensor measures is the difference in oxygen between the exhaust stream and ambient. In fact having the ambient pathway blocked is a fairly common fault with NB sensors.