Electronic Shift Kit (homemade)

Thanks so much for coming over! I'm looking forward to a great discussion.

It is a bit of an unusual situation as you are not a supporting vendor and I expect much of the discussion to be centered around a product of yours. Just for some ground rules I believe you will be held to all the constraints of vendors and members and more. It was a first post so we'll go from there. For the Tech Only discussion we don't need mention of other vendors, your pricing or costs or your motivations. In that vein I've edited your post. I hope you don't mind.

On to the transmission. (I know little to nothing about auto transmissions). You make the distinction between line pressure or "base" valve and the shift valve. Could you explain the different function of the two? and/or how they interact?

 

So basically the box gives a sport (Feel) but offers no performance gain??

 

I wouldn't expect anything measurable. No significant effect at WOT.

 

Some questions that came to mind. This modifies a control input into the transmission.

1) Is all the control logic for the transmission within the TCM? or is there some logic within the transmission itself?

2) Are there other inputs to the transmission? Either control or data? If so are the other control or data visible to the TCM and factored into the generation of the signal that's being modified?

3) If there are other inputs into the transmission are they related or have any interaction with the input signal being modified?

 

EXACTLY... the NAG1 is PWM @ 1000HZ 12VDC per Chrysler
This is why you can't simply supply 12V or Ground to the solenoids.

1-The pressures that are modulated are ALWAYS kept within factory limits as defined by the booster valves that are controlled by the solenoids...you NEVER get more pressure than the factory engineers designed into the system...you just get the higher pressures SOONER. Again: base line pressure is preset with those wonderful old-school springs at around 125 psi...the solenoids control the booster valves that add UP TO ~100 psi on top of this...as requested by the PCM and TCM.

2-Setting 1 is stock...it technically disconnects the box and takes it out of the loop.

3-The solenoids will actually live a longer, happier life...

For you old-school guys...yes you CAN simply go into the valve body and
S-T-R-E-T-C-H the stock spring out (or replace it with a stiffer one) on the line pressure valve and the shift pressure valve and get a good bump in pressure. It may take you a time or 2 to get them just right...but it is still a cheap, viable solution...but it IS non-adjustable.

I was actually going to ask you to delete some of the info...good job...I am glad we're on the same page...

Pressures:
Line pressure is the "MAIN" hydraulic pressure that is running thru the passages of the valve body...it is the pressure that all of the other pressures are regulated off of.

Shift pressure is a modulated pressure that is adjusted to accomodate the "shift sequence" phase of clutch engagement. The NAG1 trans does not have the "spring-loaded accumulators" of the old trannys that acted like a hydraulic shock absorber during gear changes... The NAG1 uses electronics to control how much, how fast...and how long the pressure takes to get to where it needs to be by the end of the "shift". This is all of the wizardry that takes place in that "expensive to crack" TCM...unfortunately.

Your question implies that there is no "performance gain" to be had a part throttle... I think that if you really, truly thought about that question...and the fact that you drive at part throttle 99% of the time...you might look at it a little differently... just my .02

Your valve body already gives MAX pressures at WOT...my box...or a valvebody...or springs...aren't going to give a measurably better 1/4 mile time on a properly working trans...period. There are very few "milliseconds" to be shaved off of a WOT shift sequence...unless your trans is already slipping...

see above

1- The trans has no cpu other than the TCM...as a matter of fact, there is actually a "stand-alone" controller that can operate these trannies...bet you didn't know that...!!! It is not 100% effective on the DCX cars...but it has been running the Benz version for quite a while now...

2-The biggies are speed sensors on various components. The NAG1 has 2 speed sensors to calculate an output speed...and measure the shift sequence timing (part of the problem). The trans adjusts for "wear" on the clutches based on how "long" a shift takes to complete (yes, that bastard can measure in milliseconds...dangit)...and part of the lookup for data is centered around temperature. If you car is cold...the TCM wants to command a slower shift until temps are up...but you have purposely made the temps colder by using a low-temp T-Stat...on top of this...you are tricking the trans into shifting FASTER...by bumping the pressures sooner than commanded...so you have to do a balancing act of "how cold can I make it run...and how quick can I make it shift...before the PCM thinks there is a problem..." If you look at the "calculated coolant temp" in the Predator datalog section of the handheld controller, you will see what temp YOUR car wants to run at... mine is 190 F MINIMUM. (realize that this is still about 25 degrees cooler than the stock TStat...). I have found that some cars with a 170 or 180 TSTAT will throw codes because of this...whether they run any trans mods or not...!!!

My "MAGIC" number seems to be around 187 F...keep above this and I get all the benefits of a cooler TSTAT and no issues whatsoever with the trans. (So there is apparently a "tolerance window" for the ECU vs operating temps for everything to be considered OKAY"...

whew...

and 3- I have found it only necessary to work with line pressure and shift pressure to attain the desired results without having to undo a single bolt from the tranny. The only other "wish list" item left is shift points higher than 6600 rpm. Right now, the alternative is manual mode (paddle hold) or an expensive TCM reflash (that may or may not stay calibrated). I will be looking into the stand-alone item mentioned earlier as an alternative after the first of the year.

On a side note...to give you a better idea of what kind of tinkerer I am:

I have made in the past: (not for profit...simply to show others how to do it... ;-)
A Junkyard valve notching tool for like 30 bucks for cutting valve reliefs with the pistons STILL IN THE BLOCK...

I have a plan for slotting your own brake rotors...with a skill-saw...!!!

Modding the R/T brake caliper mount to accept the SRT rotor without any other mod...!!! (and getting HOTTTT pads to give better than stock SRT performance...)

Plans to upgrade the clutch paks inside the NAG1 and use HP clutches to hold 2x the stock TQ...

I just don't have the necessary time and/or money to get all of this stuff going...

So when I say I do this stuff for the community...you can understand my passion for these cars...and the people that take the info seriously...

Take care...gotta go make some stuff...!!!

-Freak

 

I think you have a good chance of floating the stock valves/springs at about 6700 or above.

 

There are times at WOT where my stock NAG1 takes a good 0.5 to 1.0 second to find the next gear. I know I can't be the only one to have this weird "problem".

If I understand correctly David's awesome box does NOT adjust at WOT. Right?

What solution do you guys have? David, comments?

 

Your shift lag is fixed via Chryslers TSB.

 

Who has stock springs anymore? Most stroker motors could withstand 7000 or higher.

It does adjust at all phases of the RPM band.

On your problem, are you sure you aren't hitting the rev limiter pre shift...up your rev limit and see...if it's raised, lower your shift point and see.

Very good info here, i've learned more about the NAG1 in 5 minuets than in 4 years of owning the car.

 

I'm so fricking lazy... I still haven't bothered to find that TSB hahaha

But I'm pretty sure I know the one your talking about.

 

SHAZAM!!!

hahhaahahha thanks Quick. Guess this means I need to take my car in now. I'm so fricking lazy (hint hint)