gpbeau

I'm working on installing a GMPP LS3 crate engine and a Gearstar 4L80e into my '67 Impala. A TCI TCU will be used to control the trans, not the GM ECU that runs the engine.

This engine uses a DBW throttle. The TCU needs a TPS signal. I've read a few posts that mention tapping the TCU's TPS signal wire into the rising TPS signal on the DBW throttle. Is that the generally accepted solution? If so, do the 5V and common wires from the TCU just get tied back or should the common be tied to the ECU's signal wire for that TPS circuit, too? Does tapping into that rising signal cause any problems for the ECU? If this doesn't work, what is the solution?

Many Thanks!

mrvedit

What is your reason for not using the GM TCU?

gpbeau

Quite honestly, I haven't checked to see if the GMPP ECU is capable of running the Trans. The engine/Trans packages they sell all have a separate TCU so my assumption is that the ECU doesn't have the capability.

So, with the assumption that the TCU is required, any direction regarding the TPS signal and the TCU's reference line?

THANKS!

JoeNova

4L80e?

mrvedit

Yes, the ECU is just that - the Engine Control Unit. You need a TCU to control the 4L80E.
While I don't know what model/part# TCU you need, many new/refurbished ones are under $150; even just $80.

The TCU gets all its engine signals directly from the ECU; there is no splicing.

gpbeau

Thanks for the feedback. I'm using an old-like 2009--GM TCU that was made by TCI/FAST (uses the same T-COM software). Picked it up from a friend for exactly $0/ There is no serial/CAN input for this unit and it needs a TPS signal (as well as tach and VSS) like the TCI units do.

So then maybe two questions:

1) Same as before--can I just splice into the TPS rising signal on the DBW throttle body and leave the TCU's 5V and ref lines open (tied back)?

2) you're suggesting a refurb OEM TCU or something else? If that's the case, a) how do I determine what part number and b) what software/system is used to modify the calibration?

Learning every day!

THANKS

JoeNova

I understand, but when did the 4L80e come with a TCU?

mrvedit

Hmm, not sure why we aren't on the same page.
The 4L80E never "came" with a TCU but needs a controller.
The pre-2006 PCMs can control a 4L80E or 4L60E.

Starting around 2006 with the E38 ECM, a separate TCU controls the 4L80E or 4L60E (which was later renamed to 4L70E).

gpbeau: I suggest you start a new thread in the PCM Tuning section - post the part number of your ECM and ask for the part number of a TCM to control a 4L80E.

We just had a thread there were the OP spliced into the TPS circuit for NOS controller and it lead to still-unresolved problems. See my post #5.

https://ls1tech.com/forums/pcm-diagn...ltage-tps.html

gpbeau

mrvedit,

Thanks for the clarification. Sounds like certain GM vehicles used a separate TCU with 4L80e trans at some point.

I don't have the ECU yet--waiting for the crate and ECU kit to come in. Just getting prepped at this point.

The issue related in that post about the NOS switch is exactly my concern. There are two separate 5v circuits at work (the ECU and the TCU) and I don't know if they're using chassis ground as their reference or if it floats. And, as you mentioned in that post, each system now has to deal with another circuit in parallel of unknown design and impedance. Seems like it's a bit of a crap shoot as to whether both system will work after tapping in like this.

I'll post as you suggested once the ECU comes in.

In the meantime, if there are others who have had luck (good or bad) splicing a TCU into a DBW throttle, let's hear the stories and the results.


THANKS

poorhousenext

I believe TCI may sell what you need. works with carbs, should be adaptable for DBW too. I'm sure what you need is out there as DBW and 4L80E have been around for a while.

I'm 73 yrs old, so understanding how to word internet search should be a challenge for me, but it's really simple logic, but then again, I'm a Smart Phone user, I use a Dumb Phone because that is simple logical thing to do also...LOL

Try "Drive by wire tps installation" web search. Should find Mag write ups and different forum threads on subject.

http://www.tciauto.com/tc/4l60e-4l80...s-w-mounthtml/

forcd ind

iTrader: (7)

My suggestion was a stand alone TPS switch as the one shown above if all else fails

mrvedit

gpbeau: do you plan to use tuning software like HP Tuners or EFI Live?
If yes, definitely get the GM TCU as that gives you much better tuneability than anything else.
However, if you don't plan on buying one of these $650 tuning packages, then the TCI TCU might be the better choice as it comes with the software/ability to tune basic parameters like shift points.

JoeNova

You need a T42 TCM.
You can score them used for $100, they will work with most Gen 4 ECUs and a 4L80e, but will need to be reprogrammed to run the 80e similar to the way a Gen 3 ECU setup for a 60e needs a segment swap.

Cpt.Derrek

iTrader: (13)

seeing that directly on the EZ-TCU page it says "*Requires a Throttle Position Sensor (TPS)" http://www.tciauto.com/tc/ez-tcutm-t...85e-to-09html/ so getting it to work with the DBW may not be possible unless you get a TPS sensor and mount it directly to the hinge on the peddle or something similar.... which could work....

But really the TCI EZ-TCU is pretty limited with its tuning and using the old fashion serial handheld unit to program it is a pain, HP tuners with a 4th gen TCU would be the best option.

gpbeau

Thanks for all the replies.

Cpt Derrek and forcd ind: Most of these aftermarket TCUs need a TPS signal, whether it's from existing hardware or new. The DBW TB doesn't offer an opportunity to add an additional TPS (I don't think...) and the idea of linking one to the throttle pedal had occurred to me, but there is no guarantee that the DBW throttle position will match the command from the pedal.

mrvedit and joe nova: As this will be my first LS engine, part of my purpose for buying a GMPP crate engine is to take advantage of their calibration work. Yes, I'll eventually start to play with something like HP Tuners, but there is plenty to do just to get the engine installed and running! Ditto with the TCI TCU I'm using (this is a much older unit than the EZ-TCU--more flexibility and no goofy hand held). It's a place to start so long as I can come up with an acceptable TPS signal. Migrating to a GM TCU (thanks for the T24 callout!) makes lots of sense if it can integrate with the ECU and provide calibration flexibility. Any suggestions for people/shops that have the experience to reprogram the TCU to play nice with the GMPP ECU?

So much to learn! Thanks to all the educators here!

poorhousenext

Is the old TCI TCU you have the one called the RED BOX due to it' color?

That's the one I know about that came before the EZ one. If so your probably going to have a problem trying to tune it unless you have access to a Computer with a Hardwired Serial Port built into it. Never been able to find a USB to Serial adapter cable & software that will allow communicating with it, and it uses TCI tuning Software with very easy setup.

gpbeau

poorhousenext--great handle, sounds like a guy with a car problem!

Well, the TCU I have is about the same vintage as the TCI red box. This is a grey box from 2009 that was offered by GMPP under their brand, but it was a TCI box. It uses software by FAST with which I'm very familiar as I have two other cars running FAST XFI boxes. It took a while, but found the right T-COM software on a dead TCI page (thanks, Mr. Google!).

I use a MacBook Air running windows to run the FAST and TCU software. I've had really good luck with a particular Kensington USB/Serial converter--had my engineering staff use these exclusively because they were great. Also using the converter that FAST now provides with their kits. Plugged in and worked off the bat. I can send the model no. if you would like to try it.

poorhousenext

Thanks for the offer, but I have a Disc with the original software on it, that came with the Trans for my 2nd build while still trying to work though the 1st one that led to "Poorhousenext" that you guessed right for reason behind it.

I have an old IBM ThinkPad I can use when a serial port connection is needed. All my other computers are IBM ones since I'm also a Hard Core Gamer. I started out with an Apple II in early 80's, then a Mac, then IBM when I started gaming as most games up until the last 7 years did not support Apple Computers, but I do have an IPad, but no Smart Phone of any brand...LOL

The more I re-read you post the more confused I become. You say DBW, but your question(s) seem to indicate you have "mechanical/cable throttle linkage". DBW would be and easy splicing into DBW throttle body wiring. The TCI 6X that uses the old RED BOX to control required splicing into the DBW throttle body electrical wiring between throttle pedal and electrical driven throttle plate. That's a no-brainier.

Sounds like you have a mechanical throttle pedal actuating a mechanical throttle plate. Reading between the lines, it also so sounds like the mechanical throttle body on you car is not an Aftermarket one that all appear to have a provision for installing a throttle plate position switch on the opposite side from where the motor that actuates the plate is installed, but a GM production one with no such provision.

If above is correct about your car not being DBW but Mechanical/Cable operated you have two options, trying to adapt a TPS switch to linkage to give provide throttle plate position to TCM or Aftermarket Mechanical one with switch as you have no DBW wiring to splice into.

I'm lucky as I all three of my LS swaps into 60's model cars have been DBW, swaps so I have the wires needed to splice into. Splicing into existing DBW wires is a no-brainier.

If I'm wrong and you have a DBW Throttle Pedal, splice into the wires between it and the TB at the most convenient place for routing and test to make sure the needed voltage readings are correct at full and closed throttle pedal positions.

gpbeau

Poorhousenext--the engine is GMPP's LS376 engine which definitely uses a DBW throttle. No cable, no mechanical pedal. It sounds like you're splicing into the throttle pedal signal and not the TPS signal on the throttle body (between pedal and TAC)? [The pedal signal connect to the TAC which talks to the ECU which then controls the DBW throttle--there isn't a direct connection between the pedal and the throttle that I know of,] Is that the case? I've seen posts stating to splice into the rising TPS signal on the throttle body (there are two, one rising, one falling) for the TCU, but some posts indicate this can cause problems with the ECU reading that TPS signal. If you have any detail on what specific signal you used with success, I'd be very interested to learn!

mrvedit

This might be a useful description of how the GM DBW system works:
http://easyautodiagnostics.com/gm/4....hrottle-body-2

According to that the throttle body may have two TPS sensors which return a simple 0-5Volt signal according to how far the throttle body is open.
The signal between the Throttle Pedal and the Throttle body is a more complex PWM (Pulse Width Modulation) and you would not want to splice into that.

I still think a stock TCU will be your best bet, although it would need to be tuned to your axle/tire ratios and desired shift points.