LS7Bird

iTrader: (4)

Please excuse my ignorance on the subject, but I really need some clarification on the benefits of using a 99+ Fbody computer in a 98 car.

The most I know is that tuning is easier on the 99+.

My questions...
1. In what sense is the 'tuneability' superior? In blower/turbo applications? Or just overall? I am swapping in a sleeved Ls7 and plan to run all-motor for the time being, with the possibility of a direct port setup in the future (if it becomes more readily available). I guess the question is, would it really be necessary to go 99+?

2. I want to keep the drive by cable setup. Does the 99+ require a DBW TB? Personally, I just prefer the mechanical nature of cable setups.

3. Question 2 also leads me into the next; can I still use a DBC 1998 ABS module if I have to use a 99+ computer/harness? I'd like to retain this if possible.

4. Fueling - Can I keep my steel tank? I don't really care about weight savings for the rear. Will I just need the Racetronix harness to adapt? I'm still foggy in this area, too.

5. Anything else I need to know about going from a 98 to 99+ engine harness, computer, and instrument cluster?


Thanks in advance for your time.

LS7Bird

iTrader: (4)

🤔 Bump

MontecarloDrag

iTrader: (3)

You can upgrade to a 99+ PCM and make everything work in your car. All modules and cluster are compatible with a little work.

Be aware that you need to do a lot of wiring changes, by a lot I mean most of the wires on PCM connectors.

LS7Bird

iTrader: (4)

I'm starting from scratch, the car was a 6 cylinder.

fast5speed

Hi there LS7Bird - funny coincidence, I actually logged in (for like the 4th time in 2 years) to post about the exact same thing. I am actually a tad bit more educated than you are after digging through 20 different threads in the past 2 days.

Here's the basics as far as I understand:
So, 1998 was a unique year for the F-body cars (in terms of the computer system). It was the 1st year that they sold them with the LS1, and in 1999 they overhauled the computer system to modern standards. Some details include being able to run multiple threads of data simultaneously. Also, the new PCM (which ran a completely new operating system) could run 8 bits of data PER THREAD, where the 1998 PCM could only run ONE line of thread at 3 bits.
I may not be 100% accurate on those numbers, but you get the idea. It's regular evolution with computers nowadays.

What does this mean for you? Well, the 1999+ PCM is much 'smarter' and can manage more data at once. With the 1999+ you can tune in "real time" and take advantage of other really advanced tuning functions. I think the 1998s also have a tendency to fry/break, and occasionally they may have to 'guess' air/fuel ratios if there is a hole in the data.
The 1998 OS is a bit more complicated for tuners to use.

So how do you switch from 1998 to 1999+? Well, it's not really that hard. You need to buy a 1999+ PCM and you need to *re-pin your harness*.
I believe the actual PCM connectors are the same (still trying to find this bit of info) but the pins are all mixed up. So you need to remove the wires from the connector, and re-insert them to a different pin location on the connector to correspond with the PCM.
Alternatively, you can buy a 1999+ engine harness and avoid all the work of re-pinning, BUT you have to swap the entire harness.
Other things you should know - some/alot of your functions won't work. The fuel gauge won't work apparently, and you will lose real data on your oil pressure gauge - it will become a dummy light from now on. I think there are also issues with ABS and traction control.

Here are some links
http://www.mrk-motorsports.com/wp-co...o-1999-PCM.pdf
https://ls1tech.com/forums/pcm-diagn...cm-99-pcm.html
https://ls1tech.com/forums/conversio...swap-faqs.html

Questions I still have:
Can I re-use my 1998 PCM connectors/plugs? Simply relocate the wire WITHIN THE ORIGINAL 1998 CONNECTOR?
What do I need to do about "reprogramming PCM to match VIN"?

LS7Bird

iTrader: (4)

Hopefully we both can get some answers.

Fortunately for me, I'll avoid all of those issues you mentioned above since I'm introducing all the necessary parts because technically I don't have any of them from a 98 Ls1 or 99+.

Thanks for answering my first question. It sounds like I should use the 99+ computer, in my situation. Now I'm just wondering if I can use other certain 1998 components like DBC throttle/cruise and the steel fuel tank with that 99+ setup.

My2000Z28

iTrader: (1)

I just emailed slowhawk about tuning my 98 and they said they didn't want to unless I converted it to 99+. Then he also assured me it was a plug and play swap. But I have read all that you guys seem to have read about it. So I'm lost. I don't know what the hell to do.

fast5speed

i think you just introduced something different. Previously I was talking about *converting* a 1998 harness to work with a 99+ PCM. This involves removing each wire/pin from the PCM connector and re-locating it to a different pin location on the connector. Each connector has 80 pins I believe.

What * I believe* slowhawk is referring to "plug and play" is to REMOVE your 1998 wiring harness and INSTALL a 1999+ harness.
It is easy, literally every single connector plugs in, but this requires you buying a harness which can be pricey.

My2000Z28

iTrader: (1)

Ah whoops. I'm trying to figure out how a 99 pcm operates a 98 cluster though. Serial data port and all that garbage. People say they lose TC and fuel gauge

My2000Z28

iTrader: (1)

Repinning the harness seems easy if you know the pinouts. I've been told the pcm swap Is what's a bitch getting things to work. But now that's twice I've been told it was plug and play. Last I was told I needed to swap out clusters and have fuel segments loaded before tune, and repin my harness for the 99

Slowhawk

iTrader: (12)

What I said was getting a harness from BP automotive or another good company that does the conversion parts in the harness. They make them plug and play. Everything works after as I said.

You can repin the stock harness but if you screw up it takes a ton of time to find the issue(costly)
It is cheaper for us to pull old harness, install new one than paying us hourly to re pin the stock harness. Nevermind the rat nest you are left with.

My2000Z28

iTrader: (1)

Yes, you did tell me that. I then contacted BP and asked them about it. I was very confused as to how a pcm that (I've been told) used serial data to talk to the gauge cluster, would function with a cluster that (I've been told) gets its signals from the sensors. I asked them a little about it but got one word answers. Your answer was their harness works. Now I don't expect them to divulge the secrets of their $750 harness, and I don't expect you to sit there and give me boat loads of free advice while your on vacation. Not trying to start a hassle, I was just looking for tech advice as to how this all even works. I threw your name out there so people would take it seriously and not assume I was simply misinformed. I just want to know how this all works. I was never planning on spending upwards of 1000 on harness and computers(and oil sensor according to BP). Just to have my car more tunable. I did find a write up on this finally after talking to you, but it's also being said that TCS goes bye bye. Again just trying to wrap my head around all of this from a tech perspective.

I realize there are more hack jobs out there than not, but if it is in fact an extension of (something like) 12 wires and a total repin, I'm certain I can do it right. I was going to reloom the harness anyway. And no, there will be no rats nest. You won't have to touch anything. My intention is to give you a good clean fully functioning vehicle.

If you tell me ill be sacrificing anything with a 98, I'll do it. If I do it, I will probably try to do it myself but can always fall back on the BP harness. Now This is all something I'm trying to jump on as soon as possible, my kmember and drivetrain are out.

This isn't a shitbox, Fresh rebuild 6.0 from a shop, new sensors,, fresh built stage 2 t56, all new control arms, bushings, ball joints, tie rods, springs, koni shocks, new wheels, new tires, new ujoints, axles, wheel bearings, brakes, reman/tested/matched injectors, all new gaskets, Car will be ready to rock when it gets to you.