boost on factory ecu?

[evil_si]

currently doing a 1uzfe conversion into a s13 silvia which i want to supercharge using an eaton m80 due to availability.

what i want to know is will the factory ecu from a sc400 run with boost?
i heard a rumour it will run up to 9psi is that correct?
or
what mod's do i need to make?
different map sensor?

cheers si

 

[Lextreme II]

How does the stock ecu know there is boost? You should not run more then 8 psi on stock injectors. If you run something called Fuel Management Unit (FMU) would work with your stock ecu and stock injectors.

There are few companies claiming that you can run 7-9 psi with stock injector and un-altered ecu. I just wonder how smart is the stock ecu. Increase air, you must increase fuel and ignition. Stock ecu was programed for stock application. If you add a supercharger and add boost. The stock ecu doesnt know that and you will run very lean. Therefore, you must have a system to trigger more fuel with boost.

 

[rarson]

I'm very interested to see how your S13 turns out.

As far as fuel delivery, if you use some sort of unit to augment the stock ECU, I think you could get away with it, but like Lextreme said, you can't do it safely with just the stock ECU.

 

[Tonyd]

I'm getting a bit confused here.

I too had heard that you can run standard ECU and injectors up to 8 psi.

The ECU I was led to believe was as self learning ECU and together with the lambda sensors would compensate for the lean mix under boost conditions by increasing fueling.

With my Lexus powered Cobra I was planning on initially fitting a couple of low pressure turbos at sub 8 psi and then when I get a bit bored with that upping the boost together with an intercooler and a piggy back fueling computer triggered by boost running a couple of extra injectors in the inlet plenum to take care of the extra fueling requirement.

If a piggy back computer is needed to run low boost I might as well go the whole hog from day one.

Is standard ECU and injectors safe with sub 8 psi ?

Cheers,

Tony

 

[Lextreme II]

Standard ECU is safe at any boost, but you have to tell it what to do. The un-alter stock ecu can compensate about 15% of increase injector size, but its not smart enough to know how much more fuel to add from the boosted system. Like I said, you need to use a FMU or piggyback to compensate for the increase air volume.

The stock injectors are capable of 8 psi or less.

 

[Lambo]

Poor mans Boost mixture controller

Hi guys, one method i used on a Mitsi 2.6t Starion was to put a variable resistor in series with the temp sensor that went to the computer, basically this retarted the timing and said to the computer this is a cold engine give it more fuel, and it worked really well, ended up with a 2lt computer talking to a 2.6t with oversize injectors and an opened up air flow meter, could we not hook up say the traction control pot to vary the temp sensor and so increase the fuel when on boost, i realise it's the poor mans way of doing it, but it worked and the Mitzi was quick.

Best Regards
Lambo

 

[Toysrme]

That only adds 4% - 5% extra fuel to the long term fuel trim.

Doesn't work on Toyota's.

 

[evil_si]

in the past with other n/a toyotas bthat i have turbo'd, I have been sucessful by using a 2 bar map sensor from the likes of a 3sgte, upgrading the fuel pump, injectors and installing a rising rate fuel pressure reg.

this has worked well for me on different engines, but would like to know if any one has tried this on a 1uzfe

 

[Lambo]

Toyota ECU

Hi Guys, i have collected together some info on the inside of a toyota Ecu do we have anyone out there into Microprocessors, or serious fuel injection, that can make more sense of it than i can, it has exactly how the CPU operates, talks to the Auto, sets the Fuel amount etc serious stuff, block diagrams etc fairly large so will not attach pm me with an email address if anyone would like to have a look at this, it says
Sample
ie Calculation of Injecting fuel amount
Injected fuel amount is directly related to the injecting valve opening period. the base pulse width is determined by the total suction air volume per engine revolution, calculated by the intake air flow and engine revs, the final pulse width is processed by multiplying the base pulse width by such compensating factors as warm up enrichment, a/f feedback compensation and A/F learning compensation and lastly adding a battery voltage factor to compensate for the delayed start of injector opening the base pulse width is determined by Tp=k * q/ n where
tp = base pulse width
k = constant
Q = air flow volume rate
n = engine speed and then goes into lots of formulaes etc
17 pages it must mean something to someone , but every little bit helps unravel the Computer if you know what your looking at

Regards
Lambo

 

[jibby]

I wish I can break it down for you but I do not have that experience yet, currently studying up. However I was wondering is you know of a Lexus shop in or near the LA area that will install a stand alone ecu that rocks. I have a built 1992 sc400 running a nos application, my stock ecu with a piggy back keeps adjusting and gets my ride out of tune, fed up what to go with a stand alone to get the most performance out of the engine and transmition. Any shop other then TM Engineering?

 

[Lextreme II]

John,

This is the best place in Southern California. Tuner, Engineer and Go Fast Tech. DB Performance Engineering (626) 571-7126 Contact Danny and tell him David refer you.

 

[MaxPower]

That only adds 4% - 5% extra fuel to the long term fuel trim.

Doesn't work on Toyota's.

Long and short term fuel trims are only used in closed loop, if you make the coolant sensor read low it will run open loop only. It will however kill the cats and O2 sensors pretty quickly if you run it this way all the time.

 

[Toysrme]

Actually you're wrong, let me show you why.
OBD-I only has fuel trim. It is not used during open loop. That's part of the reason why older OBD-I Toyota ECU's will accept nearly any flow injector & fuel flows without having a problem.
Now for OBD-II
Long Term Trim is a learned value over time which changes gradually in response to conditions. Long term trim is a component of what Toyota refers to as the "Basic Injection Duration". BID data is stored in a nonvolatile RAM and is not erased even when the engine is shut down. This information is used during warm up and wide open throttle conditions.
Short Term Trim is instantaneous correction value determined from the oxygen sensor readings. Under normal conditions it cycles rapidly around the 0 percent correction value and is only functional during closed loop operation. Short term trim is a component of the "Corrected Injection Duration". CID is used only during closed loop operation and not during open loop conditions. When Short Term trim exceeds plus or minus 10 percent for too long, the Long Term trim begins shifting, changing the Basic Injection Duration to bring the Short term trim back within the plus or minus 10 percent range. Short term trim can vary as much as plus or minus 20 percent, but the above correction mechanism works to keep it within plus or minus 10 percent.
It should be kind of obviously... If LTFT wasn't used in open-loop, half the problems people have with ECU's "correcting" tuning changes wouldn't happen in the first place. It could change whatever it wants in closed loop, then in open loop everything would be like you want it.

If you make the coolant temp sensor output too low it will revert back to running open loop. Most of the time when the coolant temp is under 150-158*F the ECU goes back to open loop. It will also have horrible timing & the A/T transmissions will all shift poorly & lock out overdrive gears!
The coolant thing has been done for years. The most anyone ever logged with a scanner on any OBD-II Toyota to my knowledge (and I did research this a few years ago to do it myself) is +5% fuel to LTFT. I use to advise all of us car v6 owners to do the mod, but it simply didn't do anything of note. All of us with iron block v6's could get infinite times more simply leaning our old AFM cogs & advancing distributor timing 7-10*
I also use to do this mod on my older OBD-I engine. I never got it to jump a single fuel trim step. OBD-I steps are 0-2.5%, %5-10%, 10-20% closed loop only.

http://www.midiwall.com/4Runner/ect.html
http://www.yotatech.com/showthread.php?t=5537&highlight=coolant+mod
Notice Dr Z get's 3.9% extra fuel. Yea big change!!!


Doing the ECT mod is most decidedly something everyone should skip.

 

[MaxPower]

mmm, the point i was making, although reading back was not clear, was that the LTFT and STFT does not change in open loop, whatever the LTFT table is when entering open loop is how it stays until c/l is entered again (the STFT is always reset to 0 in open loop), there is no feed back from the O2 at this stage so the ECU will not correct the AFR by adding/removing fuel using the LTFT like you posted. It does use the LTFT in the fuel calculation but does not vary it to get the correct AFR.

At colder coolant temps the ECU is comanding a richer mixture, so in the final fuel calculation it includes a large temp compensation and whatever the LTFT for that particular load point is from the last time it was running c/l, id have thought it would add more than 5% extra fuel when cold?? But from the dataloging you have done maybe not. I have done this on GM ECUs and it has worked to get a decent AFR, although it is a band-aid mod, and it meant the vehicle could be driven until it could be tuned properly. I have not had much to do with the toyota ECUs, but it sounds like you have, would be good to see how much extra fuel is added when cold, but as you pointed out the trans locking out gears is a problem so not really a viable long term option to fool the ECU.

 

[Toysrme]

mmm, the point i was making, although reading back was not clear, was that the LTFT and STFT does not change in open loop, whatever the LTFT table is when entering open loop is how it stays until c/l is entered again (the STFT is always reset to 0 in open loop), there is no feed back from the O2 at this stage so the ECU will not correct the AFR by adding/removing fuel using the LTFT like you posted. It does use the LTFT in the fuel calculation but doe not vary it to get the correct AFR.

OK I see what you're saying, ya I was confusing what you meant! Exactly right. No fuel trim is corrected while in Open loop, but any changes stored in the LTFT are still used in open loop.

That's why most mediocre turbo/supercharged cars have minor/major lean out problems. Poor tuners.

The tuner adds fuel before open-loop is achieved, more so than the ECU will allow. The ECU tunes it back out quickly, because it's often a huge amount of fuel compared to what STFT's can quickly deal with - you get large changes to LTFT in a short amount of time. Then the tuner has to go back and add even more fuel during open loop because the ECU is already taking X amount of that fuel out!

It's seen on nearly every crappy dyno chart where you start out at stoich & stays there too long, then it goes down to 13-1 & holds that too long without transitioning. Then it jumps quickly down to between very low 12's and 10's.

It goes from way too lean, to way too lean for the power being made, immediately to being too rich!


Example:
This turbo is making 5psi @ 3200rpm Notice how long the engine stays at stoich & aat/above 13's!?!?!?