Starting my na-t this week. Ill be running the vvti ignition coils, 440cc injectors, TT Map(2.3 bar) + Iat, But i found a 94 TT 6speed ecu. Is there a difference if i run jdm vs usdm ecu.? My car is Auto btw.. Let me know any info about this please

 

you cannot run a 6 speed ecu on an AUTO car. you can use an auto ecu on a 6spd but not the other way around.
I would suggest finding an aristo ecu, its a JDM auto ecu that will work perfect with the 440's. USDM requires 550's.

 

Are you sure about that? I believe the usdm ecu will run fine with the 440s, granted it's just a theory of mine as ive never personally done it. My reasoning is that the usdm mk4 uses the resistor box to allow the use of low impedance injectors. We also k ow the usdm550s work great with a stock 1j/jdm 2j ecu. Also, on my gf's 1j I've run an aristo ecu just fine with stock injectors, fuel trims were spot on same as when the 1j ecu was running it. I also know that you can assemble a 1.5j and toss in 440s and it fuels like stock 380s on a 2.5 bottom end. All this leads me to believe that the ecus are mapped differently timing wise, not fuel.

Additionally, I've been under the impression that the 2jzgte ecu will require an aristo/mk4 gte auto trans to work with an na/t auto setup using the tt ecu as the tt stuff is full electronic and lacks the kick down cable or what have you. Can you confirm this?

 

when you run 550's on the jdm ecu, it will work but you are running rich all the time. the engine can handle being a few afr points richer (if your wallet can with these gas prices) and over time it will learn to bring down the afr in closed loop only. In open loop you are dumping in almost twice the fuel you need, as there is no correction, unless you use a fuel controller to alter the signal. When the afr goes so rich your wideband just reads 10's you are loosing considerable power and you are probably gonna start getting misses from washing out the spark. its not dangerous though because the excess fuel actually cools the combustion chamber. its always safer to run rich than lean remember.

did you have a wideband to know that the afr's are spot on because thats hard for me to believe especially on a 1jz ecu which has the smallest injectors.

The reason why you can't do 440's on an ecu that calls for 550's is because you are running leaner than normal now, which is bad for a turbo car. it will learn over time in closed loop, but when you mash down the pedal and it goes open loop in boost, it will be injecting considerably less fuel from the stock map, you will get lean, and you will melt/break something in your engine. maybe not the first few times that you try it but with the right conditions you will detonate when cylinder temps get too high. All the ecu's are mapped for different size injectors, if anything the timing is more consistent. the hp differences are from exhaust and cams etc.

The 2jzgte ecu does not require a gte trans to operate. just because you install a gte ecu doesn't mean the kickdown cable currently connected to your transmission and your throttle body will magically disappear. It is mechanical in operation and the trans will shift fine either way. let the gte ecu send out whatever it feels like for line pressure its not important. the trans gets all the info it requires. to get rid of any CEL all you have to do is attach that line pressure sensor or a resister to the gte ecu, it wont need to be connected to the trans.

The reason people who swap gte motors will keep spitting out the same old information that a gte ecu needs a gte trans is because they have a gte motor with a gte throttle body. it does not have a spot to connect the trans cable. for na-t we have it all connected stock.

 

I said theory for the 440s on the usdm ecu, and asked if you were sure because I wasn't. It does make sense for the usdm ecu to be mapped for extra fuel since it is the same displacement engine and uses different sized injectors from japan to the US.

I wasn't regurgitating info from gte swaps other people have done, these were questions I was wondering about from all the auto boxes I've **** canned here recently. I personally have no first hand experience with an auto as I dislike the feel of a car equipped with them.

Also, yes, I was running a zeitronix at the time. 380cc stock injectors on a stock 1j with an aristo ecu runs fine as does a 1.5jz on 1j ecu with aristo 440s. The displacement demands the 14ish% difference in fuel. I believe the timing is a bit less aggressive due to the longer stroke of the 2j, but again. That is a theory of mine

But yeah, these were some things I had been wondering about, you seem to know some things, so I asked .

 

Personally I would just run the correct ECU for the correct injectors you are running - JDM Supra or Aristo (440cc).

 

Ali, I want you to tell me how an ecu controls injectors. You said you find it hard to believe that afr would be right because 1jz ecu has the smallest injector. That doesn't make sense. The engine has is factory equipped with the smaller injectors. Basically, the way you're putting it, the ecu controls how much fuel the Injector will dump. If that's the case, why do we upgrade injectors instead of ecu? We upgrade injectors because they are designed to flow more volume correct? 440s are chosen for the 2j because they flow more to compensate for the extra volume of air that the half liter larger displacement pumps.

With the usdm ecu, I can see how it could maybe be mapped to pulse the injectors a shorter amount of time to not run rich to compensate for the extra displacement of fuel that will pass through. But between the aristo/jdm supra ecu and the 1j ecu, I would like for you to disprove my logic.

 

No, the usdm wont really like the 440s.... im sure it will run but not ideally.
I just went from 525 cc injectors on a jdm ecu (ran way rich) to the stock 330 or w/e the n/as are and it ran even more like ****.
You could really avoid all this by just running the correct injectors.

The jump from 440s to stock n/a injectors is about the same as you running 440s in an ecu tuned for 550s.... it wont run how you want it.

You ask why we upgrade injectors instead of ecu.... nobody does that. They do BOTH. The injector rating is obviously just the max duty it can withstand and can be tuned to run less.... but not more.

but it seems you know this so im not sure why ask


in fact, instead of making a new thread why not contribute to the huge one already in development?


As for the auto it will work fine, you will just throw codes and your o/d light will flash whenever in overdrive. No big deal as it still seems to function fine.

 

Sorry i missed the whole 1jz part. the 1jz and 1.5jz are very unique situations. I was talking about 2jz's but let me try again.

The auto trans will work, but as for power wise will it handle you power I am not an expert on the ge auto trans, I have a 5 spd myself.

I see what you are saying with the aristo ecu on the 1jz with the 380cc. that works because the 1jz has less displacement and actually needs a little less fuel. this is a unique case where you would run injectors smaller than stock without any fuel controller and not run lean, because the engine actually wants less fuel than it delivers with the 440's.
When I say smaller than stock I am always referring to the size of what the ecu calls for, not the engine.

The 1.5jz runs on the 440's and the aristo ecu like a stock 2jz does because it has the exact displacement and the injectors the ecu calls for.

The problem is when installing smaller injectors than an ecu calls for, without having a smaller displacement than the ecu calls for.

So if you ran a 1.5jz or a 2jz on a USDM ECU which calls for 550's only you decide to install 440's, you are running lean because the engine needs that extra 110cc per injection that is now missing

ecu controls injectors by grounding the injector for a certain amount of time (msec) or what is called a pulse.
To deliver the same amount of fuel with 440cc injectors and 550cc injectors, the 440cc injectors will need a larger pulse because they inject less per msec.

So the aristo ecu actually has longer injector pulses than the USDM ecu, to make up for the injector size difference. You cannot change the injector pulse without a fuel controller.

 

i'm going to try to sum this up to save confusion.

the whole point is that the ECU uses input from the sensors (mainly the MAP/MAF) knowing what size fuel injectors its engine is supposed to have to calculate which pulsewidth to use to fire the injectors every RPM. if you change the injectors, the ECU has no idea you've done this, and it sends the same pulsewidth to injectors that have a totally different flowrate.

the USDM 2jz ECU was mapped to control 550cc injectors.
the JDM 2jz ECU was mapped to control 440cc injectors.

if you use a USDM 2jz ECU with 440cc injectors, say you're boosting and the ECU is firing the injectors at 6ms at full load; well, 6ms of fuel shot through a 440cc injector is 20% less fuel than 6ms of fuel shot through a 550cc injector, all other things equal (fuel pressure, temps, etc.)
if you use a JDM 2jz ECU with 550cc injectors, you're boosting and the ECU is firing the injectors at 8ms at full load because it was originally mapped to fire fuel through 440cc injectors, so it's really shooting 25% more fuel than it thinks it is.
there are things like o2 sensors that can make changes on the backend based on AFR, but they only do so much (like a few % over all, which is far from 25%).

the 1jz ECU controlling the 1.5jz using 440s gets fairly close because you increased the engine displacement (ie. fuel required) by an amount close enough to make up for the fuel you added by running a bigger injector with the same 380cc pulsewidth (fuel supplied). you added 20% displacement and 15% fuel, so it should be close, if not a little lean (there is more to the fuel requirements per displacement formula thing, but you get the point).

 

^^^^^^^^^^+1000000 You nailed it

 

Good explanation cartmill

OP check out this thread
https://www.clublexus.com/forums/sc-...-odb1-sc3.html

 

not to res this thread but ive never heard of using a TT ecu on an NA-T. I have an NA-T and just got a set of 550's for it, so if i use a TTUSDM auto ECU on my auto sc300 na-t it will work? would the maf still work or would i need the TT maf/map as well? or would this not work with the obd1 sc300 wire harness.... im very interested in this as i already have all these parts and thatd be great to use my TT auto ecu instead of a piggy back. it would be nice to use the TT maf as well. would i need MAP in addition?

 

yeah it will work, use whatever the usdm supras came with. i believe that had a map too just not as the primary metering device. Check out Ali's thread on it for any questions, ive been running it for almost 7-8k miles now at 14 psi and my car hauls *** and gets decent mileage

 

wow that blows my mind...after 8 years of trolling forums this is the first time ive heard that you can do that. pretty awesome tho since i already have the parts, ill be doing this later in the week to try it out. ill put on the TT MAF and auto TT ECU and take it for a test drive. i just got some 550cc injectors for the GE motor as well, was planning on redoing all my maps for the safcII but im just going to run it off the auto TT ecu first and see how it does, thatd be great to simplify it some.