BigBird98

I'm replacing the LS1 in my 1998 Firebird with an LS3 crate engine.

I've been told I will need to increase fuel. Which PCM table do I change?

FYI, I will be using an ancient version of the LS1 Edit program to make changes.

macca_779

Fuel pressure is not controlled in the PCM. Its static at 58psi

BigBird98

After the post that pointed out fuel "pressure is not controlled by the PCM", I realized I didn't phrase the question well at all. :-(

What I'm trying to find out is "How do I make the fuel/air ratio richer?" I understand that when the fuel/air mixture is too lean it is possible to blow the engine and I sure don't want to put my new engine "at risk"!

redtan

iTrader: (5)

Firstly I would get a base LS3 tune from someone if you can and use that as the starting point.

Secondly, working oxygen sensors will get the part throttle AFR where you need it.

Otherwise you have to mess with the MAF and VE tables for fueling.

BigBird98

Redtan, Thank you very much!

Anyone out there have the "base LS3 tune" in LS1 Edit format?

I will not be making any changes to the new LS3 engine. Those days are over. Changes would surely void the 24 month/50K warranty.

jimmyblue

iTrader: (11)

Is it your plan to run the LS3 motor with an older
LS1 PCM? If so have you made sure things like the
crank reluctor tooth count is compatible?

As a rule, the LS1 tunes were too rich, not too lean,
when you're talking about the big end. Moving to a
crate motor with same injectors as before would
not change things much (unless you're also moving
up in displacement, in which case there's a data
field for that, that wants reality).

People will tell you all kinds of off-the-cuff things
when they have no knowledge or responsibility for
the outcome. What you want is tools to measure
AFR that can be relied upon, and take it from there.

BigBird98

Yes, I am using the original LS1 PCM with the new (2008 model) LS3 crate engine. I purchased the motor from Scoggin-Dickey and talked to the parts guys and the service manager. About 3 months ago they replaced an LS1 with the same LS3 engine I bought.

I bought a 58x-24x ignition convertor box. The LS1 crank has 24 teeth and the LS3 has 58 teeth. The convertor box makes the PCM think the LS3 has 24 teeth.

The LS1 has 5.7 liters and the LS3 has 6.2 liters. The crate motor was complete; injectors, MAF, etc.

daveS

I just fired up a new 430 hp LS3 in my hot rod. I bought an entire connect and cruise package with the engine, ECM and wiring harness, plus a new 4L65E trans, with a separate TCM and wiring harness.

You'll have to convert the LS3 to a mechanical throttle body, since the LS3 uses an electronic throttle body, that you have no wiring or computer to operate. There will probably be other items where the plugs on your wiring harness won't fit things like the MAF sensor, MAP sensor and oil pressure gage. The other option would be new wiring and computer.

Since I'm building a car from scratch, I bought an in-tank fuel pump from Tanks and used a corvette fuel filter/pressure regulator, that includes a fitting to return excess fuel to the tank. The pump is a Walbro brand that has the proper pressure and flow.

http://www.tanksinc.com/index.cfm/pa...=cat/cat61.htm

I just posted a stock LS3 tune on the HP Tuners website, but all you can do is read it, with the HP Tuners software. Any tune that's downloaded from HP Tuners requires their software and $100 in credits to use. It will take awhile before the tune shows up in the repository - someone at HPT has to review and approve it first.

http://www.hptuners.com/forum/showth...e-idle-problem

BigBird98

daveS. Congratulations on getting all the new parts for your hot rod. That looks like a great combination.

My mechanic immediately noticed the electronic throttle body and ordered the cabled throttle body. The wiring assembly that has the 58x-24x converter also has 2-3 pig tales. That assembly is supposed to address other wiring issues. I've got my fingers crossed.

I will look for the stock LS3 tune on the HP tuners website. The good friend who told me about Scotty's SW Corvette in Albuquerque is a member of the local corvette club. Maybe someone in the club has the HP software and would be willing to help me.

Thank you so much!

gagliano7

You have to make sure the injector data is correct before you fire it up. It could dump to much fuel and wash down the cylinders. The LS3 has bigger injectors than the LS1.

joecar

The other LS3 injector tables also need to be interpolated and copied over.

kyphur

iTrader: (5)

I just installed the 525HP LS3 crate engine in my 01 Camaro about a year or so ago. You'll need to change over a good bit of information for a decent tune.