Maft-pro and boost cut issues (logs/settings/mods included)

[Fozbo]

I went out and spent about 1/3 a tank of gas tuning the supra tonight. I ironed out some of my boost control settings, but fuel cut is starting to rear its ugly head. I have a 10 psi spring in the wastegate, and boost control is set to hit 12 psi.

Logs:

This one has two boost cuts (I know I shouldn't have kept on the throttle, but I wanted to make sure I got it isolated):

This one is a little farther down the road, identical setting:

This one shows no boost cuts, but it also wasn't WOT the whole time:

Maft-Pro export:
**Note: I know my AFR tracking settings are high, I'm just doing that to keep it from tracking while I'm tuning. Also, the aux. boost settings are not active, just remnants of when I was setting up boost control**

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TunerPro Bin Data Export
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Source File: 11_26_08_no_tracking.bin
Source Definition: TPro4600.xdf

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Constants
------------------------------

Vehicle Select: 00
Number of Cylinders: 6
Displacement: 3.00 Liter
Airflow Source: 0x00 Select
Manifold pressure source: 00
Density Comp Source: 0x00
Barometer Comp Mode: 01
Frequency Out Mode: 0x04
V Out1 Mode: 0 Select
V Out2 Mode: 0 Select
AFR Source: 1 Select
Freq In Mode: 0
Aux 1 mode: 00
Main Scale: 3.00
Volts Out 1 Setpoint: 2.51
Volts Out 2 Setpoint: 3.61
Afterstart enrichment: 0.00
Tune Load Point, Low: 36.40
Tune Load Point, Mid: 100.10
Tune Load Point, High: 143.00
Freq Out Max: 0
Timing Monitor, Base Adjust: 0.00
Timing Monitor, Correction: 1.27
AFR Tracking, Enable delay: 0.00 Seconds
FE Smoothing: 00
Boost control TPS Spool: 2.00
Boost control RPM Spool: 2400 RPM
Boost control TPS Start: 2.90 Volts
Boost control PSI Start: 8.00 PSI
Boost control DC% Start: 14.00 Percent
Boost control PSI Set: 12.00 PSI
Boost control PSI Aux: 12.00 PSI
Boost Control Gain: 12.00
Boost Control DC% Start Aux: 8.40 Percent
Boost Control Max RPM: 8160.00
AFR Min TPS: 5.10
AFR Min RPM: 8160
AFR Min MAP: 166.50
AFR correction lean limit: 5.00
AFR correction rich limit: 10.00
AFR correction gain: 4.00
AFR Aux %: 0.00
TPS Enrichment: 0.50
TPS Decay: 0.80
Throttle Body Size: 7
TPS MAP Max: 0.00
MAP Enrichment: 0.40
Boost Enrichment: 0.80
MAP TPS Min: 0.40 Volts
MAP RPM Min: 0.00
MAF Limit TPS Threshold: 0.00 Volts
MAF Limit: 0.00
MAF Limit / KRPM: 0.00 Grams/Sec


Mods:

Engine
(rebuilt head and bottom end)

Wiseco pistons
Eagle rods
Clevite bearings
ARP hardware
Cometic metal head gasket + ARP studs
5 angle valve job
Stainless steel 3rd valve cover
MKIV motor mounts

Drivetrain

Rebuilt transmission
SPEC stage 3 disc (6 puck) with stock pressure plate (SPEC PP exploded)

Exhaust

Modified 321 SS tubular manifold
Full 3" turbo back piping
Dual tip Magnaflow muffler
50mm HKS type external wastegate (10 psi spring)

Induction

Turbonetics 62-1 turbo (.68 hotside)
Full 3" aluminum intercooler piping
Godspeed intercooler
GReddy Type-S BOV
K&N filter
MAF delete

Electronics

MAFT-Pro with Speed Density and Boost Control options
Innovative LC-1 Wideband and controller
GReddy turbo timer
20 psi Autometer gauge

Thanks!

 

[JimR]

What size injectors are you running? What is your freq out (synthesized airflow signal) just before it cuts?

I'm curious if you are hitting the magic number (1500hz? I'll have to doublecheck that number) or if some other variables are involved.

 

[dumbo]

What size injectors are you running? What is your freq out (synthesized airflow signal) just before it cuts?

I'm curious if you are hitting the magic number (1500hz? I'll have to doublecheck that number) or if some other variables are involved.

yah i belive that is the number...you can change your F Out Max..but i would be VERY CAREFUL. if you put it to 1600 it wont make a difference, but put it to 1450 and you wont hit fc but could very well go lean and cause problems.
i didn't know exactly how to use it and put it at 50 couldn't give her gas..put it at 700 boosted to about 17:1:icon_mad:

 

[Adjuster]

I have not tried, but can you set the MAFT PRO max Hz rate to 1499? (1500Hz is what triggers part of the FC IIRC.)

Good news for me, I finally got my Supra running again.. it's been so many years, I actually do not know exactly when I ran it last. (Perhaps 4 years, according to my wife.. but I think it's more like 3+ v/s just slightly less than 4... LOL)

Anway, I have a lot of tuning to do still.

It will not build boost at all, and you can not hear the turbo at all... (I expected to hear it, but then again, the car is much more quiet than I remember..)

I'm just glad it runs.. and moves under it's own power finally!

OK, on point, I have 5.xx, but not 5.11, the one that has the part throttle tune. (I have downloaded the program from what I can tell, but it will not upload to the MaftPro for some reason. Likely user error..)

 

[dumbo]

I have not tried, but can you set the MAFT PRO max Hz rate to 1499? (1500Hz is what triggers part of the FC IIRC.)

Good news for me, I finally got my Supra running again.. it's been so many years, I actually do not know exactly when I ran it last. (Perhaps 4 years, according to my wife.. but I think it's more like 3+ v/s just slightly less than 4... LOL)

Anway, I have a lot of tuning to do still.

It will not build boost at all, and you can not hear the turbo at all... (I expected to hear it, but then again, the car is much more quiet than I remember..)

I'm just glad it runs.. and moves under it's own power finally!

OK, on point, I have 5.xx, but not 5.11, the one that has the part throttle tune. (I have downloaded the program from what I can tell, but it will not upload to the MaftPro for some reason. Likely user error..)

I thinnk it only goes in increments of 50--cant remeber its been a few months since i've seen my car, good to hear YOURS is running:evil2:

WARNING: Be careful when adjusting your F Out MAX, i'm not resposisble for any problems. but i think it works like a fuel cut defender.

 

[JimR]

I cannot think of any combination of factors where you'd want to clamp the output signal (aka fuel cut defender) with the Maftpro available. If you're hitting fuel cut, simply lean out that portion of your table (via direct VE edits, or the user tune) while watching your AFR's.

The most important question here is: What are your AFR's right before you hit fuel cut? If they are bogging down in the 8:1 or 9:1's, then you can certainly lean out a bit to reduce the output signal at that point and avoid fuel cut. However, if your AFR's are 12:1 or leaner, then your ECU is doing you a favour!

You have three choices at that point. 1. Reduce your max boost, 2. Bigger injectors, 3. Retarded timing. Injectors are the preferred route.

 

[Adjuster]

That is why I have 780cc injectors now, up from 550's that did not have the "headroom" I wanted.

I pull 42% mainscale, so it's going to take some serious pressure to have the MaftPro sending a Hz signal of 1500 to the TCCS.

 

[7MGTEsup]

That is why I have 780cc injectors now, up from 550's that did not have the "headroom" I wanted.

I pull 42% mainscale, so it's going to take some serious pressure to have the MaftPro sending a Hz signal of 1500 to the TCCS.

Isn't pulling 42% going to give you to much timing? As far as I'm aware scaling back the air flow signal that much will give you a bunch more timing (which is bad)

 

[dumbo]

Isn't pulling 42% going to give you to much timing? As far as I'm aware scaling back the air flow signal that much will give you a bunch more timing (which is bad)

mainscale on the maft pro is pulling fuel, not timing.

 

[Fozbo]

Thanks for the replies guys. I went ahead and bought what I had on my to do list for a while now: Aeromotive AFPR, Walbro pump, and Siemens 680cc injectors. Those should safely get me out of boost cut and allow me to tune it safer with higher boost.

My afr's read from the graph in the original post look to be just over 12.5:1. I recently did a reinstall of windows on my laptop, so I have to reinstall TunerPro to check out what my F out was (thankfully, I did save all the log files and everything before I wiped my computer).

 

[JimR]

mainscale on the maft pro is pulling fuel, not timing.

This statement is misleading. What the mainscale does is adjust the frequency that the maftpro outputs to the ECU in place of the Air Flow Meter, which the ECU uses to control the injectors, "pulling fuel".

HOWEVER, this is not the only thing the ECU does! It can also advance or retard timing at the same time, based in part on the airflow frequency it is receiving. This is what allows it to run 30 degrees advance (for example) at 4000rpm and minimum throttle, and only 18 degrees at the same rpm on full throttle. I'm talking about boost-sensitive timing control here.

I'll quote a single paragraph from an article by the VP of Engineering at Innovate Motorsports:

Many people with aftermarket turbos don't change the spark advance very much, believing that earlier spark creates more power. To combat knock they make the mixture richer. All that happens really then is that the mixture burns slower and therefore hits the peak pressure closer to the right point. This of course reaffirms the belief that the richer mixture creates more power. In reality the flame front speed was adjusted to get the right peak pressure point. The same result (with more power, less emissions and less fuel consumption) could be achieved by leaving the mixture at the leaner optimum and retarding the ignition more instead.

The entire article (Timing Myths Debunked) is here: http://www.innovatemotorsports.com/resources/myths.php

I highly recommend it.

My final two cents: Getting bigger injectors may solve the problem by slowing the combustion rate (which also keeps things cooler) through the use of excessive fuel, but setting the correct timing is a better way to go about it.

Cheers,
Jim

 

[Adjuster]

I have not made any timing changes yet, but in theory, the MaftPro will allow us to adjust timing while sending the modified Hz rate signal for aiflow to the TCCS to fire the injectors.

I have mine wired up to not only monitor timing, but control it as well from what I have read. (Again, I just have run the Supra a few times now on Speed Density with the MP doing the math.)

My PLX wideband died. I'm going to get a different WB, most likely the innovative one, but first I'm going to try pulling the PLX, and send it back to them to see if they can fix it easy/cheap. I only have perhaps 2500 miles of use on the PLX. Not a very good experience if it died in that many miles. (It's not a bad sensor, I've tried replacing the sensor, no improvement, it's the control/display unit. I have a M300.)

So, when I have the ability to actually see and monitor what the AF ratio is, I can start to boost more, and see what timing is doing as well. (I have boosted to the stock waste gate spring pressure of 11psi according to the Omori gauge. It has a peak/hold feature, so it's very nice to see it not vary from pull to pull. It's 11psi. No spikes. It's also an open dump pipe, and it's not as loud as I thought it would be either. A nice supprise.)

If I get some time this weekend, I might take the Supra out for a run with the laptop hooked up and saving the data. It's a very cold blooded car now. I still have the cold start injector, and it starts and idles up fine as long as that's on. I think I might need to richen up the idle mix, but the stock O2 is still in the loop, so trying to make changes with that there is pretty pointless unless I'm way lean for some reason. It idles really good when it's fully warmed up. It's easy to stall when it's not.

I'm sure it's some adjustment for tip in response, and the fact that I have not done any fine tuning at all yet.

The main reasons I tore back into this car again have been avoided so far, but at only 11psi, it was never a problem before at that pressure either. (Fuel cut on the 550's, and the lack of top end power with the bolt on T4.)

I will not push more boost untill the wideband is in the loop, making sure I can monitor it, and setup some fail-safe fuel ratios on the top end of the spectrum.

That is very interesting on pulling timing v/s just adding more fuel. It would be better for fuel economy, and they claim power too. Very interesting, but also sort of dangerous depending on fuel quality in my experience.

 

[dumbo]

good to know

 

[nikwal]

I've been searching for that frequency(1500hz) for weeks, can't believe I missed it until now. That's great news beacuse at 1500 the accuracy of the timer creating the frequency is still very good..(made my own air flow bodger). I've set the cut to have some hystereis, so it comes on again at a lower value.(If I set cut at 1400hz from the afm it might come on at 100hz or whatever is set).

(we're talking of the karman-vortex signal here right? or did I miss something hehe)