The original LS1 in my 98 A4 coupe is trashed and have decided to replace it with a gmmp LS3 crate motor. From my research the actual install is pretty straightforward, it's the electronics that require planning and leaves me with a few questions.

I'd rather not crack the motor open to replace the 58T reluctor with a 24T. The adapter module isn't ideal although from what I hear it works. Can the PCM be upgraded to a C6 PCM? If I install the LS3 wiring harness can I get it to work with my A4, can it be programmed to suit?

I really like the idea of a stand alone ECU as there's a ton of garbage I want turned off, VATS, C-LK, RTD and so forth. Will a stand alone work with the A4? Is it possible to still run the factory guage cluster?

If I end up having to keep the factory PCM, I may follow the DIY and upgraded it to the 2000 + PCM, any reccomendations on who to program it with a base tune for LS3?

I have the 2 fuel lines on my rail, supply and return, it's regulated on the rail. How will that work with an LS3? Will I have to drop the tank and move to the more modern style, reg in the tank?

Thanks in advance!

 

I've completed a few personal LS transplants.

In my '56 Chevy sedan I installed a WS6 LS1 with late LS ECU and a dual fuel rail, one is the fuel in and the other is the return to the fuel tank. The thinking was it keep the injectors cooler. This sort of swap is simple compared to your C5. Ten years later, I've never had to tough the engine nor the trans except fluids...

I'm currently building a frame up '37 Chevy Pro-mod Coupe. It is a carbon fiber body and on a custom frame we fabricated that's utilizing C4 IFS and IRS but with a Dutchman's 9 inch
IRS diffy center section. The engine is the new LS3 crate engine with a RPM level 5 Super Mag Tremic T56. Lots of C4 & C5 components.

But, what's important here is, no other computers what so ever in the '37 & '56 !!!!.

But because in the '37 build I'm using the C5 instrument panel, Steering Column and Dash, I must use the later C5 ECU. The ECU does a direct "DATA" link up via "GMLAN" that sends all the various data from the engine ECU, to the Instrument panel MPU. For me it is only the Fuel tank level inputs to the ECU,, everything else will be disabled.

The LS3 does have a single line fuel rail, it can be modified to the dual fuel rail, this would connect up to your dual fuel tanks. So, that soles the dual fuel line mod. Or you may be able to Mod the fuel tank pump assembly to a single I/O.

The '98 LS1 dual fuel rail will not fit the LS3 with the newer "higher intake manifold". and some differences in the sensor connectors. This particular early LS1 ECU is not going to get you the best performance that you might wish to obtain. Installing the intake manifold and larger throttle body onto the new LS3 would be,,,,, tragic IMHO

The Fuel injectors will, prob, have a different connector, use can obtain wiring adapters.

I'm using a later C5 ECU and will Mod the harness., but you'd have a few tedious wiring mod's ahead of you or this upgrade and not for the faint of heart !!

But there is an excellent post on this Forum for the SWAP to the later C5 ECU. You should read this post, over and over. it is very complete and very detailed.

So, you've now read the ECU Swap, that's the difficult part of upgrading to a LS3.

You can obtain fuel rails, wiring adapters etc prob from Marc @ Vette Nuts. Marc is an excellent supplier of parts and He is very up to date in these swaps. He is a performance NUT, well like most of us.

I've purchased many parts from Marc, the last order was on a crate, and I've got one more arriving next week. Marc prob has all the wiring adapters and parts that you might need, and He already has the experience, important to a new adventure like this one !! I much perfer getting the correct parts the first time !

To you question will a new GM ECU and simplified kit link COM's via GMLAN to your ECU. In several conversations that I have personally had with GM Engineers, Yes. is the answer.

BUT, nothing else will operate !! You might be able to get a few MPU modules to operate, but not likely enough.

So, its a must to utilize the later C5 ECU, and make the MOD's for full performance from a new LS3. I think the newer (and much better) ECU for the C5 is 1999 and up.

If you just can't complete the ECU upgrade and Mod's// Swap, then ask Marc what you need to swap out and purchase to install a LS3 Crate with your '98 LS1 ECU

We've got a '98 Vert with the early ECU and a 2004 with the newer, significant improvement. If I wasn't currently building my '37 Chevy Coupe, then I would make the ECU upgrade into my '98 Vert without hesitation. I just don't have the time. But, I am an Electric Engineer and I've designed many many microprocessor based systems over the years like these ECU's, and many swaps in Chevy's. So I have a slightly different perspective than perhaps many.

I recommend that you read the ECU swap and perhaps get in contact with the author.

Good Luck,

MC...