Another Crazy Idea (LS4 Swap?)

[04BlackGXP]

Hey everyone. It's safe to say that I have too much time on my hands thinking about this kind of stuff. Considering how well my last post like this went , I figured I would give it another go.

This thought was spurned by it recently coming to my attention that I have a bottom end oil leak (crankshaft seal I believe) in my Northstar, rough cost estimate was $3000+. I have some time on my hands, some extra funds and access to another daily driver. So, naturally, my mind jumped immediately to putting that money towards putting an LS4 into my car!

I do have a few questions, though. For example: how much does the PCM control in our cars? I'm thinking that this whole thing wouldn't be too difficult if the engine mounts are right and I just used most of the modules from the donor. I'd buy a wrecked GP GXP for the swap for the tapshift. Would it be possible to use the engine and trans control modules from the donor car and then all of the other modules from the Bonneville? If not, I wouldn't be entirely opposed to doing a dash swap as well.

Another crazy idea that I had was adding an F40 manual trans from a G6 GXP to the business end of an LS4 (since the bolt pattern is correct as per the Fiero forums) and rigging up a stick in the cockpit of the Bonneville.

Fun stuff; probably prohibitively expensive, but also the way that the Bonne GXP should have rolled off the assembly line in my humble opinion.

Has anyone else pondered this?

[CMNTMXR57]

No idea. You would need EVERYTHING. Engine, trans, driveline, PCM, network (I.E. Harness), sensors, etc...

At the end of the day, you'll probably spend just as much, if not more $$$ and a lot more in pure time trying to make the swap work, than just fixing what you have.

[04BlackGXP]

I see. That's kind of the feeling that I was getting. The problem is that I've spent most of my time around third gen Camaros. They're great because you get the benefits of EFI without the drawbacks of all of that integration. Because I've worked with that mindset, I think in terms of everything being modular and functioning separately. The more that I research, though, the more that I realize just how much integration there is going on.

I've never owned anything newer than this. I would imagine that the integration on newer cars is 10x worse.

[CMNTMXR57]

Yea, even going from your '04 Bonneville to any Grand Prix GXP, you go from regular OBDII to CAN (still OBDII). Which is two different styles of networks. But even your cigarette lighter is run through the PCM now.

[04BlackGXP]

Oh wow, that's interesting.

My main interest is in getting more power. I know that it's been an old adage around here that you can't tune the Northstar PCM. I'm finding, however, that some folks are saying that they can flash the PCM:

http://www.pcmcalibrators.net/supported-vehicles.html

I'm also finding that people on the Cadillac forums are getting randy about using an LS1 PCM with an external transmission control module on the Northstar:

http://www.cadillacforums.com/forums/ca ... 1-pcm.html

Any thoughts? This car has basically turned into a weekend cruiser for me. If I could get more horsepower out of it, I would be really happy.

[CMNTMXR57]

Anything GM 2005+ uses CAN network. The first Grand Prix GXP was 2006.

Not sure on the other things, never looked into them, and since I don't have a GXP anymore, not a core interest.

[sandrock]

LS4s MUST use the appropriate 4T65...these LS blocks have no starter bosses like the others do, the starter is actually located on the transmission on that drivetrain.

Going with that...replace the DoD lifters with standard roller lifters and basically use an LS1 intake turned the opposite direction. Guess what...you now have a transverse LS1.

Now, take a '98 F-Body PCM (or use a later model PCM with modded tables that deletes DBW). Still Class II. Mod the trans tables to control the 4T65e.

Not as easy as it sounds, but entirely doable I think.

[04BlackGXP]

That was the thought that I was having, but there are fuel delivery issues and body management as well. Do the rest of the modules need to 'see' the PCM from the Bonneville or would I be okay using just the PCM for the LS4?

Also, the starter issue can be worked around--I've seen a thread where a Fiero guy built a starter bracket for an F40 and mounted it to an LS4.

[sandrock]

Fuel delivery...use an L67 pump and an '01 Corvette fuel filter. This is the filter to use when converting to a returnless injection system, as it has the FPR built into it. Mount in same location as stock. You will need to build new fuel lines to accept this system.

Body management...you might have issues with the instrument cluster as it reads the PIDs in the info stream to get all the vital information. I'd have a custom cluster built with all the gauges you need. My best guess is that most of the cluster will work as the PIDs are the same, aside from oil pressure, which the LS1 I think uses the same system as the pre-2k Bonnevilles (PCM doesn't see oil pressure so it can't put it into the datastream)

[CMNTMXR57]

A lot of work and a lot of $$$. Well more than the money to fix an oil leak.

[repinS]

And the power gains wouldn't be that much. You'd also be gaining a weaker transmission.

[2003 SSEi]

Sell Bonneville, Buy car equipped with LS4

[CMNTMXR57]

I was gonna say that, but I think we had that discussion in the last thread.

[excessive81]

I have been doing research on the exact same topic. I think install will be pretty straight forward besides motor mounts themselves. The electronics between the ls4 ecm and tcm and bonn will be the largest head ache. I love my gxp so the idea of much better ls setup is very appealing to me. Dont care as much about power increase as if wanna go fast will drive camaro or vette

[04BlackGXP]

Haha, yes. We did cover that in the last topic.

Selling the car isn't an option right now--I don't want to get into the reasons, it's just not in the cards.

I've found a guy on the Cadillac forums who does PCM tuning (AJ at PCM Calibrators) and I'm asking him what his gains tend to look like on a stock engine. The price is a bit high, but if we're talking 20-30 hp gains then that would put me in LS4 territory. That would be with a car that I already have, love the styling of and has a transmission that won't blow up.

I've also asked if PCM Calibrators can tune for a forced induction environment. I know that there's no supercharger for the 04-05 GXPs (PLEASE PLEASE PLEASE correct me if I'm wrong since that's my ideal solution), but turbocharging might be an option (albeit an expensive one).

UPDATE: PCM Calibrators can do forced induction tunes. I'm also onto madtuners right now. Their prices are a bit better and I know that there are a couple of GXP folks who have gone with them. I'd like a really aggressive tune since this is mostly a cruiser now, so I might contact them about that.

Can anyone provide me with links for some 04-05 Bonnie GXPs or DeVilles that are running a forced induction set-up?

And has anyone ever put an exhaust cut-out on a GXP?

[CMNTMXR57]

Wait4me is another popular Caddy tuner. I can't say to these as I have a multitude of local shops that tune, on a chassis dyno nonetheless, so I go that route.

As to forced induction on Bonneville GXP's, I have not seen any. Cutouts are cutouts. Nothing major to do.

[00Beast]

Here's my take: Fix the car and drive it.

[04BlackGXP]

Beast, I respect your encouragement to make the responsible choice but I'm not really looking for advice. There's a 95% chance that I won't make any changes to my car, a 2% chance that I'll fix it and then a 3% chance that I'll actually do anything performance wise. I know what I should do, but that's not what I want to do. I talk about what I should do at home, I want to talk about what I want to do here.

I've sunk a lot of time and money into pumps and gaskets (including valve cover gaskets which already need to be replaced) and I'm sick of it. I don't want to spend over $3000 just to fix a seal when I can top off the oil every week instead and be happy.

I'd like to get some more horsepower since I can't quite afford a joyride and I already have this car. If I could get a new engine that's moddable with more horsepower and no oil leak then great. If I can't, then I want to know what my options might be for more power and for making this the car that I want.

Sandrock, it sounds like you've thought about this once or twice...

[sandrock]

Sandrock, it sounds like you've thought about this once or twice...

What gave you that idea?!?!

It started with my '97 when I was building it up. I had everything thought up and then came time to look at the subframe...which made the swap a total no-go. Not to mention the engines have an inherent issue with oil consumption, and that made me just stick with an L26 swap.

[CMNTMXR57]

Beast, I respect your encouragement to make the responsible choice but I'm not really looking for advice. There's a 95% chance that I won't make any changes to my car, a 2% chance that I'll fix it and then a 3% chance that I'll actually do anything performance wise. I know what I should do, but that's not what I want to do. I talk about what I should do at home, I want to talk about what I want to do here.

I've sunk a lot of time and money into pumps and gaskets (including valve cover gaskets which already need to be replaced) and I'm sick of it. I don't want to spend over $3000 just to fix a seal when I can top off the oil every week instead and be happy.

I'd like to get some more horsepower since I can't quite afford a joyride and I already have this car. If I could get a new engine that's moddable with more horsepower and no oil leak then great. If I can't, then I want to know what my options might be for more power and for making this the car that I want.

Sandrock, it sounds like you've thought about this once or twice...

So you're interested in sinking a lot of time and money, trying to retrofit and make work, something that wasn't initially designed that way. I'm not against your initial ideas, but at the end of the day, as frustrating as N* leaks are, in the long run just fix them, and move on. I get you want more power. We all want more power. But the amount of power you're getting (33hp), in return for the money spent, and headaches to make it work, along with a weaker transmission, just doesn't seem worth it. Trust me, you don't want ain LS4 and a 4T65E. I'm hoping the LS4/4T65E I have gets through another 5 years without any headaches.