nmp0098

I just joined here because it seems like this is something that might be of interest to this community based on some other threads I've seen here. Here is my original post over at grandprixforums.net:

http://www.grandprixforums.net/f20/s...dod-24080.html

I tried to put together a pretty complete list of what I did, and it isn't perfect by any means, but hopefully you all find it useful. I don't have any performance numbers, but the tune is way out of whack. When I get it tuned (which may be a while cause I need to borrow a wideband), I'll take it to the track see what she does.

GXPJAY

Good job!!!

blackhawk0251

iTrader: (6)

Sweet write up man!

AlabamaGuy

iTrader: (5)

Sweet!

DP 08 GXP

iTrader: (3)

since you live up north of me you wanna do that to my car lol?

JDMC5

iTrader: (3)

who's tuning your car? You live like 10 minutes from me. BTW, I have a wideband.

Now that I'm thinking about it, your tune shouldn't be THAT far off by just swapping the intake. Was it dialed in before the swap? Your main adjustments should be to the timing and VE tables.

TiredGXP

iTrader: (2)

Nice.

Now get it tuned and on the dyno!

AlabamaGuy

iTrader: (5)

+1 qft

blakss

iTrader: (4)

Great job but I was wondering instead of getting a new vally cover could we use that adaptor to rotate the OPSU and use the throttle body from watever intake we choose using the the wiring harness and rewiring it from a 8 wire to 6 wire and also can some explain the modifying asside from getting clearance for the opsu, the maf next to the power steering pump and extending the DOD harness..
Ps. And also wouldn't we be able to use a aftermarket fuel rail designed for watever intake?

nmp0098

LOL, my work is not so good that I want to hack up some else's car. Seriously, that was a lot of work and it wasn't so fun that I want to do it again anytime soon. I did it all with hand tools so it's not like I could bang out another one any quicker. But I'll gladly answer any questions you have.

nmp0098

Yeah, you are right around the corner. I was planning on learning myself, but if you are interested in helping me tune that would be great. The HP Tuners intro recommended having a mentor when you start out. I have HP tuners, and while I don't have the pro I do have some other tools that will help me get the wideband onto the CAN bus. There are some guys at work who do some tuning, but I don't know any of them personally so I was going to ask around and see what turned up. I'll PM you.

I haven't touched the fuel or spark tables yet. I've just done a lot of TCM tuning and played with DOD thresholds a bit. Right now, it starts and idles fine, and when cruising it seems to do OK. I can easily accelerate up hills in top gear (TCC locked). But when I go WOT, it seems to fall on its face. I seem to get better pick up at 50% throttle, and if I take it to the floor it almost seems to lose power. I just think it is grossly rich or lean at WOT, so I haven't run it there much. This is all really subjective, which is why I want to get tuned before I lay out what's going on. But, at times 3rd gear feels like 2nd did before the gear change. I have high hopes for this swap.

nmp0098

The OPSU has M16x1.5 threads, and I wasn't able to find a 90 degree that would work. If you are talking about the 90 degree I think you are, that is a different animal all together and won't attach to our VLOMs. The other issue is that the DOD oiling feed is raised up instead of being cast flat. So you can't just cut the whole thing off and plug it without tapping a line. It's not impossible to do something else, but what I did was the easiest for me.

I really didn't look into a different throttle body and what if any electrical issues there might be, but using one that bolted up would make things a lot easier. In the end, I didn't spend much money on my aluminum plate and those bolts.

I'm not sure that there are any aftermarket fuel rails for this application. We have short injectors, and I don't know why anyone with an LS6 would want to install shorter injectors when there are tons in the stock size. Doesn't mean it's not out there, I just didn't look cause I figured I had to make what I had work. I didn't want to get stalled out and not finish.

The big steps:
1) Remove vacuum attachments from the back of the LS6 intake and plug the hole. Mount the MAP sensor next to it (you have to drill two holes), seal it up good with a gasket and whatever else, then extend the MAP sensor connector's wires.
2) Adapt your TB to the LS6 or adapt your TB of choice to the LS4's wiring harness. There are tons of ways to do this, and they all have their merits. A different TB might require some more work getting the vacuum lines hooked up.
3) Adapt the VLOM to clear your intake. You could plug it and use a different OSPU location, or delete DOD too. I thought what I did was the best idea that I had seen or heard.
4) Either mangle your fuel rail, mangle your alternator mounting bracket, or find an aftermarket fuel rail solution that fits. I fully intended to use the LS6 fuel rail until I figured that I needed new fuel injectors and a carbide grinder to get it to work.
5) Figure out what you want to do with your vacuum lines. My brake pedal feel has suffered from stepping down my brake booster vacuum line, so if anyone has a better solution in mind I'm open to suggestions. You also have to worry about the EVAP canister and the two PCV lines if you want to keep it legit.

That's about it. A ratcheting 6mm wrench would be nice too. I tried to plan ahead as much as I could, but I was committed to getting the mod done so when things didn't go according to plan I used parts and pieces I had on hand to get it done. I really do hope that someone takes this basic recipe and tries some different ingredients, cause there is room improvement.

JDMC5

iTrader: (3)

yeah, I wouldn't mind helping out at all. I can definitely give you a good base for learning how to tune. I've tuned two other GXP's so I'm familiar with the LS4.

Have you been scanning for KR? How do your fuel trims look? Shoot me a PM.

DavidGXP

iTrader: (14)

so are you using ls4 injectors or ls6 injectors? im planing on using ls6 injectors with a c5 fuelrail (no built in fpr) with pig tail adapters im also thinking we could use the c5 tb. how exactly did you plug the rear manifold and how exactly did you relocate your map sensor? did you glue it on?
more details please. good job btw! tuning will make a world of deference my engine was way to lean from the factory.

nmp0098

I'm using the LS4 fuel injectors. Just be aware that if you use the LS6 fuel rail and injectors they won't clear the alternator bracket without some serious modification to the bracket. In my post (pic 15) you can see that the LS6 fuel rail is about 1" taller. The mount points on the intake manifold are the same height. Go out to your car and check the clearance between the fuel rail and the alternator bracket and you'll see what I mean (see pic 1). It's not impossible, but it is a major road block.

Mounting the MAP sensor was a total hack job, so take it for what it is worth. After I cut off the rear vacuum fittings, I sanded the surface flat. First I mounted the MAP sensor there, but the connector wouldn't clear even though the sensor itself would. I then made a round aluminum plate, cut out a round gasket, and drilled four small holes. I attached the plate with the screws, but before I did I used RTV between the gasket and the plate around the edges to help it clamp. I drilled two holes for the MAP sensor (one for the fitting and one for the screw (slightly too small)). I then made another gasket for the whole area, but I didn't like the clamping force so I backed the gasket with epoxy putty and tightened down. The gaskets looked good and clamped, but I didn't want to mess with it again if it did leak so I covered the whole operation with RTV, let it dry, then coated a second time before install just to be sure.