Hey all;

If you've got a SC'd 3.4L (auto or manual) with an ECU piggyback (SMT-5, -6 or FTC), I'd like to have ya' try something. I promise you wont' break anything (but if you do, I ain't responsible! )

• Go play with your truck a bit. Let it get warm and do some (safe!) jackrabbit starts, 30-50mph accels, highway passing, etc. Note how it runs during this play period.
• Pull over, pop the hood and pull the EFI fuse (it's in the box on the driver's side fender) for a few seconds and put it back in. This will reset the ECU.
• Go play with your truck again.
• See any difference?
• if you don't, please put about 40-50 miles on the truck and try again.

What you're testing for me is something that I've always thought was happening but I need more data.

The bottom line for me is that immediately after an ECU reset, my truck will run with a LOT more power. Then over the next 2000-3000 miles, it will slowy start loosing oomph. This usually shows up with it loading up at idle, making it pretty hard to start on a damp morning (excess fuel left in the cylinders when the engine dies).


I'm pretty dern sure that what's happening is that the piggybacks can't continue to fake out the ECU in closed loop (i.e., non-WOT). Over time, the ECU will push the fuel _and_ timing adjustments to a point that negate the piggyback fake.

Now, we know that in closed loop the ECU will always push to run at a 14.7:1 A/FR ("Stoich") but the piggyback _should_ be adding fuel on the accel _slope_ where the ECU won't be sitting long enough to build a correction factor for it. i.e., the piggyback should be helping the ECU to get to Stoich faster, and the ECU shouldn't be fighting against it. This isn't what I see happening - I see the ECU fighting the whole map, which makes my truck run rich, which causes boggy performance and lousy gas mileage.

Now the weird thing for me is that it seems that the ECU will also work around my timing adjustments. This was new to me... though in hindsight it may make sense.


Lemme know what you find out in your rig.

Thanks!

 

I have been noticing some lousy mileage.
I have 285s with 4.30s and drive conservatively....

Interesting.
Sometimes my idle is lower than normal too. Not sure if that has anything to do woth anything, but I will ge tback to you...

 

My Supra does the same thing. I repeatedly see recommendations for people to pull their EFI fuse before a race or a quarter mile pass, but I can tell you first-hand what's happening...the engine is running lean. My car is tuned for 11.8:1 at 16 psi and after an ECU reset it runs closer to 13:1 for a short time. Car is much quicker, but we all know 13:1 is really pushing it.

The ECU seems capable of adjusting +/- 20%. My car idles around 14.7:1 per my PLX wideband. I can slowly add fuel and after 20-40 seconds the ECU subtracted the fuel I added and I'm right back to 14.7:1. Once I pass about 25-30% on my fuel computer (Apexi S-AFC), the stock ECU seems incapable of removing any more fuel and the fuel ratio finally begins to dip. I can do the same by turning up the fuel pressure to an excessively high level. I'm still not sure whether or not the ECU would take those fuel trims and apply it to open loop (WOT). So in other words, would the ECU take the 25% correction in closed loop and add 25% to the 16x16 map that comprises the open loop table? Supposedly it does, but I haven't been able to prove it yet.

 

Mark, I don't have any experience with the SMT units. Compared to the FTC, I found them to be a lot more complicated and harder to wire and tune. I have experience with the FTC however and out of the dozen or so engines I have been involved in tuning, none have "slipped". In fact Gadget, as per instructions in his U-Tune guide, says that after tuning is complete, you should reset the ECU and recheck to make sure the tune held.
On my personal truck, I have noticed no difference after resetting the ECU but then again I have the 7th injector kit. I do have the TRD piggyback and also the URD additional injector controller (AIC) piggyback.

 

Might have to give this a shot - but not today, as I am hauling an Accord transmission around (don't ask).

 

Opposite to you, my truck runs like CRAP before and perfect once it learns My fuel trim is +/- 2% i didnt have the time to tune it any better and the cams have thrown that off a bit because of the airflow so i gotta get back at it.

 

Hmmm... So the fuel table is basically all 0's? THAT's interesting. I wonder if this is a "feature" in that the global fuel trim adjustment won't get "unlearned" since it's a global offset to the baseline in the cells?


Oh darn... Ya' know Johnny, if that becomes a real issue for you up there, I'd be happy to bring my truck up and you can swap my stockers back into your engine.


(thanks to others for looking into this!)

 

The fuel table isnt all zeros i have tuned it to so the ecu's fuel trim reads close to zero
And...i think the cams are quite nice ill keepem for now I enjoy the exhasut note and little power surge that happens at 3800rpm+

 

Have you thought about adding URD's A/F ratio calabrator? http://www.customtacos.com/forum/showthread.php?t=51193

 

I'm gonna skip most of those threads. I know I suck.
Concerning Midi's first post. Yes, every piggyback, unless very, very carefully tuned will experiance re-learning from the stock ECU. (A problem with OBD-II).

The problem is that long term fuel trims are carried into open-loop.
If you have to re-tune ANY rpm/load that you will possibly be driving in during daily driving, or common driving. You're going to experiance some amount of LTFT change.

When tuning the main load sensor - this causes a huge problem because at some level, a choice ahs to be made.
Don't tune into closed-loop & run really lean for normally atleast a thousand rpm, or tune closed loop & have it lean out the entire thing gradually over time.



There are three ways around this:
1)
Screw tuning the load sensor
Add extra injectors, and tune them via boost - or ATLEAST activate said tuning via boost. The stock ECU can't tune what the stock ECU thinks is perfect
2) if you are going to tune the load sensor, you need to do exactly as #1. Either scale it via a MAP sensor, or only trigger your changed tuning UNDER BOOST.
eBay has pleanty of 0-30psi trigger switches for $15 shipped. Take advantage of that.


Lastly. The best of them all, and my personal favorite...
3)
TRIGGER OPEN LOOP BY YOURSELF

I've said it several times (IDK about on this forum), and I came up with it first!
Welcome to Toyota EFI - the most important paramiter to triggering open loop is the TPS sensor.

The quick break-down.

Boost pressure switch @ 1-2psi + STDP relay. Run TPS supply voltage from ECU through one side of relay. Run TPS output signal through the normally closed side.
Boost pressure switch triggers relay via boost - relay flips to TPS supply voltage which is the highest voltage that can be sent to the ECU without being out of spec.

The ECU jumps into open loop as instantly as possible.






Even better, with an SMT you can use that to trigger your boost tuning at the same time.

 

man toysrme...thats old news we (96runner, midiwall etc) have went through that during the HUGE smt thread

 

That's fine, but it was still mine first.

 

Hey Mt.. Sorry, I didn't mean to blow off your suggestion, I just needed time to look at it more.

Umm, according to Gadget (here) that box is only for trucks with an A/FR sensor up front (wide band), I'm narrow band. Though it looks like he has something for that as well, which runs down the lines of what Toys is talking about.

It's unclear to me if the ESC1 will work in front of a piggyback... I still need to be able to control my timing in closed loop in order to get a handle on ping, and I'm pretty happy with my tuning as is in open loop.

hmmm... I'll dig through SplitSecond's site.



Hey Dave... you were pretty active in that thread that Mt pointed to (on Custom Tacos). Any input on if the ESC1 is basically the NB version of the AF/R calibrator?

 

i wanna see someone try a MAP ECU w/ a supercharged 3.4

i can't wait to start tuning my setup. must resist maxing out credit card. . .

 

hmmm. THE A/FR might be the ticket. I have a wideband o2 sensor....

 

Oh yeah, I forgot about the early 5VZFE not having an A/F sensor to calabrate. Bummer for you guys, my donor is a 2001 so I'm putting one on.

 

I have the ESC1 on my tacoma for the last 2 years open loop at 1psi

I just got some extra cash on my end so i will be furthur testing the SMT7 on my tacoma and going for the MAF elimination

I also want to try to do that full throttle switch that will get the ecu to put it in open loop, the only problem that was discussed about 3 years ago in the giant SMT6 thread, was that for the auto tranny guys the ecu will shift the tranny at very high rpms even tho your not pushing your foot to the ground. I want to try to figure out how the ESC1 can do the same thing as all it does it interface the 02 sensors and thats it. If i can figure out how it works then I am sure i can get the smt6/7 to mimic this.

 

How much boost do you guys see in the normal driving rpm ranges at light throttle in the manifold?

 

dependingo n the pulley
at like 1/4 throttle im alrady in boost
anything before that not in boost no matter the rpm

 

hmmm....


Yeah, I'm thinking that the 3rd map would come into play here. The problem is that "real" Open Loop comes from a combination of things, not just a single point trigger - right? Doesn't the ECU balance what it sees from MAF, TPS & O2 to figure out that you have your foot in it and it should get out of the way?

...plus, I plan on using that map to drive a mister.


I actually see vacuum most of the time when cruising around town or highway. With a touch of throttle, say to move around a car in front of me making a right turn or to get up a small hill, then I'll see 1-2psi with a 2.2" pulley. If my foot's in it, then 7-8psi comes on pretty dern quick.