Supercharger and Fuel Map Discussion

[Romer]

I elected to restart this in another thread to eliminate the hijack on the previous thread.


I needed some springs and rear L shocks, so I went up to Slee (ain't I lucky) and Christo took me to his white board to explain the 80 series fuel system. As we know, the 80 computer is smart and can learn. So, when operating closed loop, the 80 monitors the sensors and adjusts the fuel trim accordingly. The 95+ computer is smarter, faster and uses better sensors and that is why sometime the 93/94 80's get lean, they are not able to compensate as quickly.
When the fuel system runs open loop, the system does not use any learned data, but uses a hard coded set (table of duty cycles)for fuel trim that cannot be changed. Running WOT tends to operate at open loop.

I think there are very few places on the fuel map where you can be in closed loop or open loop depending on circumstances. As I understand it, but I could be wrong, is that the open loop values are from a fixed map.

For example, under high RPM and high load, the truck will almost always be in open loop. So the fuel values for those cells will never be changed by closed loop fuel trim since you can not have those conditions (RPM & LOAD) while in closed loop.

Because which hard coded ROM data is selected is based on the sensor reading. a SC engine at WOT will have a different reading than a non SC engine and will take the "fixed" open loop input from a different spot in the table. At least, that was my understanding of how Christo drew it on his white board.
Fixed means hard coded, so two different hard coded data points

Other manufacturers fuel maps are not proprietary and can be modified (re-programmed). Toyota's can not be modified, as far as we know. Think of the fuel map as a duty cycle time for off/on.

Based on when the system goes WOT and I am at full boost, Christo theorized that my stock 130K mile fuel pump was not able to keep up with the demand and the pressure dropped. This is why my brand new Supra fuel pump was noticeable at WOT, it was able to maintain pressure, or do a better job at maintaining pressure. Again, this was theory.

With the addition of forced induction, the mass airflow meter is seeing more air, thus giving the fuel based on that air metering. That is where the extra fuel comes from. The airflow meter is part of the sensors that feed the calculation of load. The fuel map is load vs RPM.

The ECU is not adjusting for that, it is just getting a different set of lookup coordinates to look at a different area of the map.

Now adding a FPR or better injectors will not help in the above scenario during closed loop operation as the Toyota computer will adjust the duty cycle to be back with what it is now using the sensors.

Open loop will be just dumping more fuel in at the ROM values. Is this too much fuel??? My current setup does not appear to be running lean at all, so I would guess (GUESS) that larger injectors or an FPR may provide too much fuel. However, this is the part we don't know and actual measurements would help for the open loop operation.


So the bottom line is the FPR and other injectors benefit is what needs to be measured with hard data to see if there is added benefit.

Of course, if we could figure a way to tweak the Toyota Fuel Map, we could really improve the performance of the supercharger.

When Christo adds additional injectors in his turbo set-up, he has a piggy back computer controlling them. He uses his fuel mixture gauge (AWO) and adjusts via his laptop while driving to tweak it. This only controls the additional two injectors.


Here is info from a Toyota Spec Sheet Christo Linked to in the other thread:


Now the attached technician sheet does not quite jive with the above open loop explanation. It depends on what the other sensors are that it uses to determine the open loop fuel map selection. Anyone have the specific info?

What I would summarize is as follows:

• Closed loop operation would not be modified by different Fuel regulator or injectors as the computer will compensate back to optimum programming.
• If we could figure out how to reprogram the fuel table, we would be able to really tweak the performance.
• Open loop is the operation where a different Regulator or injectors would impact operation. It is unclear if a SC engine in Open loop is running a little lean, a little rich or "just right".
• Data will need to be taken in open loop operation before any theoretical discussion has any meaning, at least to me. e.g. if the fuel mixture is already optimum, then there is no benefit to add other items, if it is not, then there may be.

So, let the above be a new starting point for discussion and add/subtract or agree with whats above. I think the Closed loop operation is nailed and backed up by the Toyota Factory Sheet. The Open loop is not quite as clear.

 

[Scamper]

Ken,

My understanding is that in open loop, the system does indeed use learned data--it uses the Long FT values which are stored in the ECU, but it doesn't use the Short FT values. How it decides whether to use the Long FT or the base map is a mystery (to me at least).

That said, open-loop seems only to occur normally when the engine is cold, or if you give it the appropriate input (WOT), which would imply the inputs are at least the temp sensor and perhaps the TPS.

While Christo and others have said you can't reprogram the base mapping, I wonder if it's possible to modify the Long FT values, though this would only be temporary as the system regularly updates the Long FT values as you drive.

Does anyone know what the base map looks like? I wonder becuase even if the ECU uses some combination of base mapping and Long FT, the base map was not set up with the idea of a SC, and the Long FT was learned while not under WOT (i.e., in closed loop), so I can see where this might produce a lean condition under WOT, but that would happen even with a bigger fuel pump and a different FPR I think. Just specilatin...

 

[landtank]

From that and other posts from Christo it came apparent to me that the solution to our problem is quite simple, the execution is a little hard though.

That is we need to calibrate the MAF sensor for larger injectors.

This is actually a common practice. The idea is if you increase the injector size by 30%, you calibrate the MAF to report 30% less. The two cancel each other out and the fuel delivery is now corrected for the new sized injectors.

Here is a site that offeres calbrated MAF tubes for Mustangs.

The first step would be to identify the new injector to be used. From my calculations it needs to be around 400 cc/min for a SC and a little more for a Turbo. I recently bought some 380 cc/min ones but they will be a little small.

It seems that 87-92 Supra turbo injectors might work. They are 440 cc/min and look to be a physical fit to our injectors, not to mention very popular on EBay right now.

I've only just stated to investigate this and could use some help on the electronic side as that is where the mod would be.

 

[sleeoffroad]

From that and other posts from Christo it came apparent to me that the solution to our problem is quite simple, the execution is a little hard though.

That is we need to calibrate the MAF sensor for larger injectors.

This can be done with the SMT6 or 7. But for better control, the SMT7 allows for both open and closed loop programming and can also take the wideband o2 sensor input and use that for tuning.

Most piggyback systems will allow you to intercept a signal and then modify it before sending to the ECU.

 

[landtank]

Thanks Christo, I'll start reading up on those.

The solution might actually be a mechanical one. I read where some MAF sensors have tubes that are swapped out for the injector sizes. Basically you either enlarge of reduce the amount of air that the MAF sensor samples. This way it doesn't screw with the electronics of the sensor.

I'll yank my sensor later today to see how feasible this type of change might be.

 

[sleeoffroad]

If I had to do it, I would still do it with a piggy back since you have infinite adjustment and it is easily reversable. The MAF is a simple sensor that putts out voltage, and the piggy back computers are just devices that allow you to change the signals based on a setup that the user defines. Way easier than changing hardware.

Remember if you start messing with the mass airflow measurements, they are also used when calculating the fuel trim, so yes, if you fool it, you will fool the fuel deliver, but the 02 sensors still read what it reads and you have to take into account what the fuel trim is going to try and do.

 

[Waggoner5]

I've got many hours logged on my Dyno, so I understand what you guys are trying to do, but I am a little confused to why. The Supercharged 1FZs that I have driven and played with don't seem to be running out of fuel and running lean, they actually do remarkably well for what they are being asked to do. They are 4.5L engines and with a supercharger are supposed to make around 300 hp. Thats the same hp per liter as the 6.0L GM making 400hp so the SC 1FZ is in line with many other new engines. Granted you have to SC to get there. I do agree that there is a small amount of room for improvement, but I see the problem as that the trucks they are in weigh 6k+ pounds are are aerodynamic nighmares, not to speak of that they are also full time 4WD. Trying to optimize fuel programming is a great idea because there's always a little more to be had with finer tuning, but if you start messing with closed loop operation, your efficiency is going out the window and 10 mpg is hard enough to swallow. I have no idea of the 1FZs electronics capabilities, but I believe its probably not far off from being maxed out as far as smarts are concerned. The piggy back alternatives seem to be the place to start. If anything, I would only try to improve open loop fuel curves and timing curves to maximize power at mid to upper end load situations. You will only be able to tweak so much before you ruin the daily driveability. I love these topics and when some of the guys that live to spout out technical information jump in, there is an overwhelming amount of information posted so I mostly lurk, but as in the 3 link front end threads I am still a little confused to why?
G

 

[Romer]

Gary,
The why is because it's there. Why would anyone turn an 80 into a 45?

j/k, I love your 45 . . . . errr 80 ... errr truck!

The reason I started this is there were several threads and there have been a few long term discussions on this subject. Christo provided some info that clarified a lot of what people were saying and I felt it prudent to start a new thread to have a clean basis to start from. Besides, like you I love these kinds of discussions. There better than the , "what tire should I get, or what lift should I get, etc..."

 

[Waggoner5]

That...... I agree on completely.

 

[landtank]

Any time I look at modifying my truck I try to understand what the optimum way to do that would be. On this I'd like to understand how Toyota would do this if it was an option from the factory. I doubt they would use a piggy back.

From a commercial side of things I can see why supplying new injectors and a MAF sensor just isn't cost effective. That could be triple the cost of the piggy back option.

The idea of a set of used injectors with a mating MAF sensor which allows the stock ECU to work properly is rather inviting. Might be pie in the sky but it's something that I'm actively investigating.

If a combo seems to be a possibility I'll probably install a wide-band and plug everything into my N/A setup to evaluate it before adding boost.

 

[Cube Dweller]

Has anyone looked into what the tuner crowd does w/ similar year Supras? Wonder if it's analogous to what you're trying to do here? Bigger turbos, new maps...do they run piggybacks and take over the fuel and ignition control from the stock ECU?

 

[clownmidget]

$$$$ - full stand alone ecu's that they can tune on the dyno along with the wideband input, boost control, etc. Haltech is one I saw demonstrated to me. It would take over all the engine management and allow specific tweaks to each injector including additional ones. It was ~$4-5K installed.

Has anyone looked into what the tuner crowd does w/ similar year Supras? Wonder if it's analogous to what you're trying to do here? Bigger turbos, new maps...do they run piggybacks and take over the fuel and ignition control from the stock ECU?

 

[firetruck41]

Who's gonna toss the Toyota ECU and expirement with Megasquirt? At $400 for an assembled ECU, it is a hell of a lot cheaper than some other options...

 

[Whipp]

If anybody is seriously considering a new ECU or a piggy back computer, they might want to take a look at the site www.autospeed.com. They're an Australian e-zine that specialized in high performance cars. You can preview all articles. There are various subscription rates, you can also purchase articles individually. Their rates are pretty low.

A lot of their articles reference kits they sell or do-it-yourself projects for various performance or performance monitoring applications.

I've found that many previews have enough information to just give me an idea of what they're doing and then design the project myself.

Off hand, I'd take a look at their "Closed Loop Monitoring" article, the preview of which is here: http://autospeed.drive.com.au/cms/A_1716/article.html
I built this a couple of years ago and found that it works really well. The output LED indicates the rich/lean state of the O2 sensor. On when lean, Off when rich, and Blinking when in closed loop - as the ECU cycles the mixture around the ideal ratio. If anybody is interested, I can provide a schematic for the circuit and tell you how to set it up, though you'll have to wait for me to get home from work to scan it in and post it. I think it cost about $7 to build, including the housing I used. All parts were readily available from Radio Shack.

The limitations of this project are that it won't tell you how rich or lean you are, as just-slightly-richer-than-stoich may not be rich enough for running at high boost and high rpm. But it is cheap and simple.

Slightly off topic, this is a good, cruiser related article from the site: http://autospeed.drive.com.au/cms/A_1210/article.html

- Craig

 

[Lockd97]

I've run both an SMT6 and a Split Second FTC on my Tacoma. I am running bigger injectors and a Supra twin turbo MAF on it.

LT quote:
"That is we need to calibrate the MAF sensor for larger injectors."
LT you are right. You would have to do this and a piggyback is the easiest way to do this. Lowering the values in the piggyback fuel table will adjust the ECU output to the injectors since it intercepts and modifies the incoming MAF signal.
LT quote:
"Any time I look at modifying my truck I try to understand what the optimum way to do that would be. On this I'd like to understand how Toyota would do this if it was an option from the factory. I doubt they would use a piggy back."
Actually Toyota (TRD) did do this somewhat with the 3.4l S/C 7th injector kit . It has its own ECU and a harness that plugs it into the stock ECU.

'Wonder if it's analogous to what you're trying to do here? Bigger turbos, new maps...do they run piggybacks and take over the fuel and ignition control from the stock ECU?"
Cube, you have it right on the money, with the exception of full standalone.

 

[Romer]

Just want to keep the discussion in this thread so I will qoute a response that was put in the old thread

without a single wideband reading all this discussion may be wasted brain power. We don't have a single post with wideband data showing whats happening to a/f ratios of boosted 1fzfe's using the factory ECU. Please don't anyone start buying injectors and computers and other cool gadgets till this data is available. Scott why the hell hav'nt you done the data. you must have the equipment and you know this is true.

I was worried about leaning out with my motor after the turbo install so I baught a cheap narrow band which is useless for tunning but will let me know if things are lean. At WOT my gauge reads solid green (rich) suggesting im ok. I suspect I spend a lot of time running an open loop and am too rich which is costing me power. From watching my narrow band gauge I don't think my truck is leaning out. My egt has not ever got above 1600' so this is another reason I think I am ok. I have a supra pump. Is my narrow band telling the truth about the rich reading? I know I can not not offer any help beyond this without a wide band.

 

[Romer]

Man, you guys can't follow direction

Dusty,



Your right, I do have the wide band. I also have an extra piggyback that I will eventually put on. My only excuse to answer you is that I have monitored the short term and long term fuel trims for quite a while and they have been suggesting that it has been running stoch to slightly rich this entire time. If my STFT was high (10+) while I was in boost without being at WOT then I would be worried. That would mean the computer was adding a lot of fuel based on what the O2 was seeing ie lean. STFT's and LTFT's mean nothing in open loop.



Also, a contributing factor is that I live at 4300ft. and regularly go up to 8000ft.

Less air less fuel, but you know that.



I will get to it that is for sure. Building a turbo setup for the Tacoma has had me preoccupied but soon I won't have to travel for the job for the rest of the year and I can step up.

 

[Lockd97]

Just want to keep the discussion in this thread so I will qoute a response that was put in the old thread

Man, you guys can't follow direction

I was in the process of bringing it over here when you posted that.......

 

[SUMOTOY]

. As we know, the 80 computer is smart and can learn. So, when operating closed loop, the 80 monitors the sensors and adjusts the fuel trim accordingly. The 95+ computer is smarter, faster and uses better sensors and that is why sometime the 93/94 80's get lean, they are not able to compensate as quickly.
When the fuel system runs open loop, the system does not use any learned data, but uses a hard coded set (table of duty cycles)for fuel trim that cannot be changed. Running WOT tends to operate at open loop.

Specifically, WOT is open loop operation, always. Open loop however, is still a set tabling, usually based on a given increase in precentage over 50% injector duty cycle. IME, it's usually 70-80%. 80% is considered te max injector duty cycle, regardless of size.

Because which hard coded ROM data is selected is based on the sensor reading. a SC engine at WOT will have a different reading than a non SC engine and will take the "fixed" open loop input from a different spot in the table. At least, that was my understanding of how Christo drew it on his white board.
Fixed means hard coded, so two different hard coded data points

I don't think that's true. It could be, but normally, the ECU ignores MAF at WOT.

Other manufacturers fuel maps are not proprietary and can be modified (re-programmed). Toyota's can not be modified, as far as we know. Think of the fuel map as a duty cycle time for off/on.

Any chip program can be modified, they are all proprietary. It's a lot of work, but it can be done. The fuel map is usually 3D, i.e. it's a fuel map and a timing map.

Based on when the system goes WOT and I am at full boost, Christo theorized that my stock 130K mile fuel pump was not able to keep up with the demand and the pressure dropped. This is why my brand new Supra fuel pump was noticeable at WOT, it was able to maintain pressure, or do a better job at maintaining pressure. Again, this was theory.

It still is. IME, a lot of fuel pumps are replaced because they flunk the output test. This is where the Supra pump might have come into play, but there is 15-20feet of wire for the fuel pump circuit. The best test of FP is to take a voltage measure at the pump.

Now adding a FPR or better injectors will not help in the above scenario during closed loop operation as the Toyota computer will adjust the duty cycle to be back with what it is now using the sensors.

NO. You have increased the airflow, so you have increased the need for fuel. You can easily put in bigger injectors and/or FPR and the computer will operate just fine. The trick is making sure you don't go beyond the capabilities of the electronics, while still supplying enough fuel for the demands of the engine. If what you say is true, you should have a fuel code with the supra fuel pump.

Open loop will be just dumping more fuel in at the ROM values. Is this too much fuel??? My current setup does not appear to be running lean at all, so I would guess (GUESS) that larger injectors or an FPR may provide too much fuel. However, this is the part we don't know and actual measurements would help for the open loop operation.

Open loop fixes the DC of the injectors to some set point. It may or may not be .86lamda, that's a table estimate in the computer. Wide Band O2 sensors have the ability to track fuel under WOT, so the guessing is eliminated.

So the bottom line is the FPR and other injectors benefit is what needs to be measured with hard data to see if there is added benefit.

Always a help to measure, but you can calculate what minimum you need is. IME, a rising rate fuel pressure regulator should meet the needs of a low boost system with stock injectors. Especially since the Mr. T injectors are way oversized. What you want to target is .86 lambda at WOT. That's where the WBEGO comes into play.

Of course, if we could figure a way to tweak the Toyota Fuel Map, we could really improve the performance of the supercharger.

I don't think so at all. You would need to change injectors to do that, or add a FPR, in which case you'd need some way to have a MAP sensor input. That's beyond the capabilities of the 80 computer.

When Christo adds additional injectors in his turbo set-up, he has a piggy back computer controlling them. He uses his fuel mixture gauge (AWO) and adjusts via his laptop while driving to tweak it. This only controls the additional two injectors.

I don't think you need them, but they will work. At 15% DC, a bigger injector would probably work, as would better, just a single injector running 30% DC.

... summarize is as follows:

• Closed loop operation would not be modified by different Fuel regulator or injectors as the computer will compensate back to optimum programming.

This is not true. The trick is to add the components that increase fuel capacity, so that it stays within the design of the stock fuel system.

If we could figure out how to reprogram the fuel table, we would be able to really tweak the performance.

I don't think so at all. At low boost levels, you max the boost as early as you can, and you leave it there. Raise the fuel pressure, and/or change injector size, leave the tables alone. Remember, boost is 90% of forced induction power. That redefines 'really tweek' IMO/E

Open loop is the operation where a different Regulator or injectors would impact operation. It is unclear if a SC engine in Open loop is running a little lean, a little rich or "just right".

Not true, if you have boost below WOT, you have boost under closed loop operation. The SC engine is running a 'little lean' by my measures, but hardly dangerously so.l

So, let the above be a new starting point for discussion and add/subtract or agree with whats above. I think the Closed loop operation is nailed and backed up by the Toyota Factory Sheet. The Open loop is not quite as clear.

I'll read thru the factory sheet you posted. I don't think it's "nailed" at all. If you have boost and you don't have WOT, you have a closed loop boost issue. If you are WOT, you have an open loop operation. And it's quite clear to me, that you are just targetting .86 lambda (peak power output) with fuel injectors and fuel pressure regulator.

My concern is closed loop operation at 0-3psi, as I see that as the point where my concerns are on the SC 80

ST

 

[SUMOTOY]

From that and other posts from Christo it came apparent to me that the solution to our problem is quite simple, the execution is a little hard though.

That is we need to calibrate the MAF sensor for larger injectors.

I don't see any need for that. Why? The MAF doesn't care what injectors you put in. In the end, the issues of bigger injectors are DC limits (20-80%DC) being able to be controlled by the computer. A bigger MAF is only necessary if you put in more air than the MAF can measure or flow. That's not the case here.

Get Probst book Bosch Fuel Injection Manual.

I think you guys are jumping around too much. At vacuum, you want your truck to act like a N/A truck. At boost, you need more fuel than is available from the ECU. That's FPR and injectors, in that order.

It might be easier to think of MAF as the air input from which fuel is derived. Don't change that component, it's not going to solve any problems, only create more.

my .02

ST