Saturated to Peak Hold Injector Conversion

[95red3000gt]

ok so how much do you think the TT ecu+ harness will run me?? I just today got all my tt parts in and am ready to start (minus some misc. bolts from the hardware store), but I'm realllllllllllly low on cash right now. I also just found out that I'm not gonna be getting my bonus till july instead of May 19th so now I don't know what the hell I'm gonna do about a clutch. I still have the stocker with 55k on it, so I have no idea whats gonna happen now.

[Import Power]

Don't really need a harness. The NA an TT ECU plugs/harness are the same. There are only a few pins that change over, like boost control. You can use the NA harness and add the resistor pack to it. This will save you money. Or you can do the whole thing. Either way you need to purchase the resistor pack. Your call.

As for how much? That really depends on the seller. Prices are all over from high to low.

I got a TT ECU, 91 CAS with CAS Bracket, complete 91 TT ECU harness, resistor box, and the TT oil cooler with lines and block attachment for $400 shipped.

[firebomb757]

I am not sure i am reading this right so a little clarification would be appreciated. The way i am reading this is that i cant swap out my injectors for larger injectors without doing this modification. Is that correct? Thanx.
Garry Hubbard

[95red3000gt]

you can, but you need some way to control them (ie- SAFC). But with the tt ecu, there is already set fuel maps for the 360 injectors so corrections arn't necessary.

So now am I understanding this correctly? I can just get the TT ecu and plug it into my NA harness. Do I absolutely need to change over the pins? Why would I need to change over a pin for boost control if I'm using a MBC ?? Since I'm a base, are there really any other pins I'll need to change over being that I don't have all the luxury items the tt has??

[Import Power]

Originally Posted by firebomb757

I am not sure i am reading this right so a little clarification would be appreciated. The way i am reading this is that i cant swap out my injectors for larger injectors without doing this modification. Is that correct? Thanx.
Garry Hubbard

Without the resistor pack you can not swap in larger low impedance peak hold inj.

Saturated Injectors (NA high impedence) can be used in Peak Hold (TT) systems, but not the other way around. So if you want to use the better (larger) injector you must do this conversion.

[95red3000gt]

ohh ya sorry, forgot to mention you need the resistor pack too...

[Import Power]

Originally Posted by 95red3000gt

you can, but you need some way to control them (ie- SAFC). But with the tt ecu, there is already set fuel maps for the 360 injectors so corrections arn't necessary.

So now am I understanding this correctly? I can just get the TT ecu and plug it into my NA harness. Do I absolutely need to change over the pins? Why would I need to change over a pin for boost control if I'm using a MBC ?? Since I'm a base, are there really any other pins I'll need to change over being that I don't have all the luxury items the tt has??

Jeff's ECU pin assignment pages

[Bob The Great]

That's great work, IPO. I started trying to do this with my TT conversion, but it looked to be too much work to get the harness to work with the resistor pack, too much custom wiring, and I was pressed for time anyway. I ended up just putting some 5.6Ohm resistors in series with each injector. So far, so good.

With regard to the different ECU pins, check Jeff's page, and also this spreadsheet listing the differences between N/A and TT 1st gen harnesses. --> http://www.stealth316.com/misc/3s_19...3_ecu_pins.xls

I'm using the N/A harness with the TT ECU, and it was not hard to modify the ECU plugs.

[Import Power]

Bob, I know what you mean.

I had three things going for me.

1. I worked in the automotive electonics field for 12+ years. I think in WIRING. I used to live and breath it 80+ hours a week.
2. I have my motor and tranny out! Easy access to the entire harness and easy to rip apart and put back together
3. I had a complete TT harness with stock resistor pack. How does this help? I was able to rip apart the NA and the TT harness and see where the TT was tapping off wires that were common in the NA harness. They literally have a section of wire stripped back then take a metal band to crimp together 2-4 wires.

Much easier having what the finished product should be to disect sitting in front of you then to guess or look at schematics. This made it a cake walk. I did refer to the shop manual schematic for the inj circuits to ensure what I was seeing in the harnesses was really what was going on.

Simply put both NA and TT ECUs put out the same inj signal. On the NA it just goes directly to the Inj. On the TT that signal just gets put thru the resistor pack first then to the inj.

Where my install got a little fancy is I stole some male/female connectors from teh 91 donor harness to add the new wires needed for the injectors. The NA has a 4 wire setup for the rear set as there are 3 firing wires and one common. The TT has 6 independant wires so I was short two wires. I left the existing 3 independant wires alone, used teh shared as #1 new independant and added the new two wire plug as #2 and #3

Here is the new 6 wire setup and the other side of the plug is wired into the harness in the car. Notice the middle plug has a new 2 wire plug above it.

[Bob The Great]

yeah, having the engine out and having the time to pull both harnesses apart would probably have helped