Fuel System Chaulk Talk - Long Term Fuel Trim

[landtank]

using your numbers in their injector work sheet I get 38lb/400cc injectors.

In that same sheet if I use our stock values it calls for 305cc injectors, which is what we have so I think I'm doing it correctly.

 

[jerseyfzj80]

Rick,
just an aside/parallel to your above calculations
Porsche 996 TT
Two upgraded T-04 ball bearing turbos
3.6 liter motor
6X440cc injectors
stock MAF
Stock Porsche fuel pump (independently tested, response to us was and I quote" Is this thing for some type of offshore racing boat cause it's really got some snot") Us- "No"
This motor with NO internal changes in the motor and so real nice proper tuning yielded 772 hp @ the crank with the correction factors off of a mustang 4wd dyno


I make this statement to the point that a 400 cc injector will probably cause the 80's to fall flat on there faces and be lethargic at best under no/light boost. I am in complete agreement with ST on the 29 lb injectors with a RRFPR to "clean" the whole deal up. On the Porsche we originally started with 800 cc injectors (had to get from japan, rc and no one else even had them) these things literally had two holes in the injector head you could stick fat pencil lead in and still have room to wiggle it around. the car once it got up to full boost and was @ WOT went very fast and beahved well (ran rich but behaved ok) up till the turbo started to really deliver boost the thing was a pig my 4 cyl auto 4wd tacoma would lunch this thing @ a stop light. we pulled motor and went to RC 440's and then had the datalogs shipped to our ECU programmer and then the car came alive. literally would eat a yamaha R1 for lunch with out even working hard (i know most of you won't believe that but it will) AFR's are just about perfect on the dyno etc.

Bigger is not always better, Great starting point if you want to err on the side of safety but you final iteration wether on an s/C or a T/C should be with some thing less than what you have listed above. this concept is very hard to grasp because there is math that states that this should infact be the given injector for a given amount of horsepower but the reality is that sometimes it is actually a lesser value (inj size) once in the vehicle and on the chassis dyno.

 

[landtank]

I'm just going by the calculations on the RC site and the fact that a single turbo'd 3.0L Supra runs 440s as well.

The RC spread sheet jives with what the toyota engineers have done. I realise that manufacturers tend to not tune for performance but instead for longevity which is OK with me.

I'm not sure what your definition of falling flat is but the 3.0L Supra must be a dog.

 

[Lockd97]

Not really a big mystery here either. People are bolting the TT Supra MAF to everything. It's a large bore high flow MAF calibrated to 440cc injectors. 4Runner tuners are installing them all the time and they plug right in. However they stop short of the complete install IMO and don't add the matched injectors. They start tweeking their piggybacks to compensate for the small injectors size, and they readily admit it .

Landtank,

The answer to your question is the 440cc injectors are way overkill on an S/C 3.4l. It would just drown the motor. The main reason I added the TT Supra MAF is to eliminate the small stock MAF. Sure, the MAF will flow more air than the 3.4l will use but it is no longer a limiting factor plus it plugged right into the harness.

They start tweeking their piggybacks to compensate for the small injectors size, and they readily admit it .

The tweeking of "our" piggybacks is to compensate for the larger injectors that are installed. This is the only way to bring the fuel trims back to zero. The stock ECU cannot compensate for the 318cc injectors I am running. Stock was 270-280cc. I cannot recall the exact value.

I had to add fuel to my whole map when added the Supra MAF to compensate for the different voltage slope at the MAF compaired to stock.

 

[SUMOTOY]

I share the concern regarding the different MAF output voltage, not so much under boost, but under vacuum.

Rick, if you use the calculation for RR FPR

(PR2 x static pressure) + boost = new fuel pressure

(1.51 x 43.5) + 8.5psi = 74.18psi

That's well within the design limits of the injectors, the RR FPR, and the 330hp target you believe to get.

This is given the stock 29lb injector, which means exactly under vacuum, there will be no change to your fuel. I personally believe that the boosted fuel pressue number is quite a bit on the high side, but it maths out to the RC site. My own thinking is that for a add-on SC, you probably don't change the BSFC number nearly as much as a factory sc/turbo application.

This I verified by putting in the known 212HP of the stock truck into my spreadsheets. RC comes up at 19.99, as does my spreadsheet. Adding 8.5 boost back into the equation I hit slightly over 26lb injector at 43.5psi and 80% DC (add the 10% increase in BSFC you only get 29lb/Hr), which is a lot less than a 42lb injector. This appears to be further supported by Dusty having no changes or CEL on his turbo, and Christo drowning the SC truck in fuel with 6.5psi boost and a RR FPR.

What you might want to do now, is get some data off your stock truck. Again, this would require an OBDII scanner. If you go to measuring blocks for injector duration, you can translate that into duty cycle. It might also be good to know what the highest voltage is off a stock MAF.

ST

 

[jerseyfzj80]

Land tank,
i agree that the supra is NO dog, and like I said each car will acts slightly different. there are other factors involved that we have not discussed yet, grams per second past the MAF, boost pressure, many different variables. I am in no way stating that what I say is fact. The only I can offer info on is what i have done with my own two hands. I think that the long and the short of this problem is that:
People want more power in order to go faster and what have you. The only real way to do this properly is to spend $$$$$ and get a stand alone system and program it to suit the needs of the truck/engine.

 

[SUMOTOY]

Now Colin, there you go thinking outside the box....

I really think the 80 is quite capable of producing low boost without changing over to standalone. The real advantage to standalone is the limitless power, and limitless tweeking of the tables. It also takes out the MAF which *can* be the restriction in HP (I don't think so for a low boost app). The downside to stand alone EFI is that you lose knock sensing capability of the stock truck, which I find a useful safety feature on a boosted engine. Here, I really think the OBDII boys with datalog function can tell us enough about the air/fuel system and FTU response to enable us boosted boys to put in the proper tweeks.

If we have some baseline numbers of MAF and Injector Pulse Width, we can reverse engineer what exactly the FTU is doing (or would do with a change). With these numbers, we can also match fuel injectors and pressure to meet the needs of the FTU. From my in depth look and measures so far, I only see a couple hiccups to this being straight forward.

1) The 1FZFE uses a fuel pump resistor. I suspect it's for low rpm, and maybe just for idle, and I also suspect it might even be eliminated with a properly set RR FPR.

2) The OBDI trucks (93-95.5) with AFM will either have an easier time or a much harder time getting the 4-5000rpm fuel correct. It might be easier to give that high boost high rpm function fuel assignment exclusively to the load based RR FPR. Then again, if the voltage output of the OBDII MAF isn't maxed out at high rpm (I suspect not), then it really doesn't matter to the computer if you boost the truck or not, it's looking for MAF input with injector output up to the 5volt value of the truck.

3) SC vs Turbo. I venture that the SC will be easier to tweek and tune, since the onset of boost is faster, and it's linear rpm vs airflow requires less correction. I'd certainly put forth that a pre OBDII truck will be easier to tune with an SC, since it can't measure increased aiflow over xxxxrpm (a known issue with a vane type AFM).

One of you boys with OBD II readers can help, SC or stock truck.
MAF values vs rpm
injector pulse width vs rpm
Max values of each


ST

 

[landtank]

I realize that I'm the odd man out but that hasn't stopped me before.

Right now I'm kind of in limbo but do have a battle plan. First thing is to get the parts together and prove out the changes on my NA truck. Those results will most likely make or break the project.

later

 

[SUMOTOY]

I realize that I'm the odd man out but that hasn't stopped me before.

Right now I'm kind of in limbo but do have a battle plan. First thing is to get the parts together and prove out the changes on my NA truck. Those results will most likely make or break the project.

later

Rick
I resemble that remark. And I hardly think either one of us is 'out', maybe just odd... I certainly think a couple different approaches documented here can be a big step in the right direction in terms of the options to consider.

I hope this thread continues with a couple OBDII guys popping up some numbers off the MAF and injectors, stock or tweeked.

Cheers

ST

 

[landtank]

just realized I can read both Short and long fuel trim levels, air intake in Lbs and more through my laptop.

And those 2 sets of injectors I bought are low impedance LOL, that lesson cost a few bucks.

 

[Romer]

Ok, here is some OBD II data I took today

Condition - Idle
Load Value - 14.5%
Fuel System - Closed Loop
LTFT - -1.6%
STFT - 0.7%
Air Intake - 105 Deg / 0.54 lb
RPM - 645
Coolent - 190 deg
Speed 0

Condition - Floored
Load Value - 88.2%
Fuel System - Open Loop
LTFT - 3.9%
STFT - 0%
Air Intake - 111 Deg / 14 lb
RPM - 2637
Coolent - 190 deg
Speed 43

Condition - Steady Drving
Load Value - 52.5%
Fuel System - Closed Loop
LTFT - 3.1%
STFT - -3.2%%
Air Intake - 110 Deg / 4.84 lb
RPM - 1765
Co0lent - 190 deg
Speed 35

I tried the floored condition sveral times and the STFT is always 0 in that condition.

The only thing I get from this is that the STFT is not used in open loop driving like previously theorized. I am not smart enough to relate any of the other data.

 

[cruiserdan]

I am so lost I could not find my ass with both hands and a flashlight, at high-noon......













I just want to not have to run methanol and I want it to have perfect driveability in all conditions.......

 

[Big_Moose]

Ken,

Did you data log any of the data on idle prior to closed loop / operating temps? This is were the STFT comes into play, I think....

What does the "111 Deg / 14lb" mean overall? I know the Intake Air Temp is 111 Deg, but what is the 14lbs associated with -> Air Density or converted MAP figures

Finally, what about floored readings at 4000+ rpms?

Are you using diagnotics / OBDII software on your new Dell?

Joe

 

[Romer]

I am using a scanner, so the data logging is minimal. I can take 2 samples and then I pulled over to write them down.

The air includes the temp at the intake and the air pressure. I am guessing it has something to do with how much air gets shoved in there.

Sure I can go back out and capture 4000 rpm, but I want to see if this stuff is meaningful for before I do anymore.

 

[landtank]

I am so lost I could not find my ass with both hands and a flashlight, at high-noon......













I just want to not have to run methanol and I want it to have perfect driveability in all conditions.......

I'm with Ya Dan. From my readings there are 3 or in your case 4 things of concern when adding a turbo or SC.

1. the flapper on 93/94 trucks

2. saturated injector driver. If you look closely at the performance models that Toyota sells they have peak and hold style injectors. These injectors run cooler and are more reliable at higher DCs. When you read where at WOT the truck floods out that could be do to the fact that the injectors begin to float and never really close so you get an always on condition. There is a name for it but I can't recall.

3. As you raise the load on the engine the ECM will continue along the MAP adjusting for it. However the MAP does have a ceiling and once hit the values for DC and timing will remain constant. With this condition adding more boost will only make the truck hit this ceiling earlier in the RPM. Sound familiar Dan?

4. fuel cut off. As the MAF reports greater and greater flow eventually it will hit a point where the ECM will cut the fuel. While this is a ways off on a NA engine, adding boost and having that limit still at the same point will actually bring it closer to operating conditions.

Currently the main response to adding boost is adding fuel through a piggyback and injectors or a RR FPR. Both will lower the DC of the injectors avoiding all but the fuel cut off issue. Right now if that ends up being the only options I have I'll probably scrap the idea of a Turbo as neither really appeal to me.

 

[landtank]

air temps on a SC truck would seem to be erroneous to me as they are read pre-compressor and since there is no intercooler you can bet they are a lot hotter than reported.

 

[Whipp]

air temps on a SC truck would seem to be erroneous to me as they are read pre-compressor and since there is no intercooler you can bet they are a lot hotter than reported.

They're inaccurate with regards to the temperature of the air going into the cylinders, but they're accurate for use with measuring the mass of the air going into the engine as a whole.

 

[landtank]

They're inaccurate with regards to the temperature of the air going into the cylinders, but they're accurate for use with measuring the mass of the air going into the engine as a whole.

OK, that makes sense. It was something that was in the back of my mind that I hadn't worked out yet.

 

[SUMOTOY]

I'm with Ya Dan. From my readings there are 3 or in your case 4 things of concern when adding a turbo or SC.

1. the flapper on 93/94 trucks

Both the MAF and the AFM will have this problem, unless recalibrating the MAF. Over a certain airflow, the MAF/AFM voltage will be maximum at 5volts. On the AFM it's at a lower rpm (usually 4000).

2. saturated injector driver. If you look closely at the performance models that Toyota sells they have peak and hold style injectors. These injectors run cooler and are more reliable at higher DCs. When you read where at WOT the truck floods out that could be do to the fact that the injectors begin to float and never really close so you get an always on condition. There is a name for it but I can't recall.

Injectors are referred to as disc type or pintle type. Mr. T uses disc type, which allows a higher duty cycle before going semistatic or static (above ~80% DC, the injector open time exceeds the ability of the spring to return the injector to a closed state). A pintle type (bosch are mostly pintles) has a max injector DC between 5-10% lower than a disc type.

3. As you raise the load on the engine the ECM will continue along the MAP adjusting for it. However the MAP does have a ceiling and once hit the values for DC and timing will remain constant. With this condition adding more boost will only make the truck hit this ceiling earlier in the RPM. Sound familiar Dan?

See voltage above. Basically what happens with the AFM is that once it's fully open, you have 5 volts. All airflow increases above fuly open, are considered the same. This is where some other presence of MAP load measure causing increase fuel (RR FPR) is a must.

4. fuel cut off. As the MAF reports greater and greater flow eventually it will hit a point where the ECM will cut the fuel. While this is a ways off on a NA engine, adding boost and having that limit still at the same point will actually bring it closer to operating conditions.

I don't think you will ever see it in a low boost truck. Romer saw 91% max load so far, which means that the MAF isn't reporting full 5 volts yet. IME, I see a lot of normally aspirated MAF cars get to 3-3.9v at WOT, which makes it mathmatically impossible to get to 5 volts without forced induction.

Currently the main response to adding boost is adding fuel through a piggyback and injectors or a RR FPR. Both will lower the DC of the injectors avoiding all but the fuel cut off issue. Right now if that ends up being the only options I have I'll probably scrap the idea of a Turbo as neither really appeal to me.

I see potential problems with a RR FPR and a piggy back injector setup. You can math out the fuel pressure required for a stock injector to provide the needed fuel. I did this calculation on the 1FZFE at 8.5 PSI it was 74.5psi fuel pressure in the rail. I'm not convinced you are dialing back the stock injectors DC with a piggy back. What's more consistent with the physics of the problem, is you don't need to raise the fuel pressure as high to acheive the same amout of fuel. Again, this is lb/hr of fuel vs demand. If you add 2 more injectors or 8 more injectors, the total fuel demand doesn't change. The added injectors just allows you to lower the system pressure to achieve the same lb/hr of fuel.

ST

 

[clownmidget]

So has anyone with just a s/c'd truck and stock fuel pump and stock fpr provided what fuel pressure is being generated at vacuum, zero, boost, etc? These threads are all very interesting reading but at some point there needs to be some data logged to substantiate the differing views/opinions.

Another thought about the behavior of the boosted trucks under WOT would be to know how far the timing gets advanced and is this too much or too little given the air/fuel ratio under those conditions.

It still seems that even if none of it is optimized you still end up with better effects by adding the piggyback ecu and even an extra injector or two.

You can math out the fuel pressure required for a stock injector to provide the needed fuel. I did this calculation on the 1FZFE at 8.5 PSI it was 74.5psi fuel pressure in the rail.