Supercharged LS3 crammed into an XJ

[Skruffy]

Been out of town.
Update on the exhaust.
The shop found a way to get all four camaro cats in which is tough. Then they ran the two sides into a y and then into a twister muffler. It is nice and quite which is what I wanted although having a single pipe is too restrictive, I can feel a significant lost of power. I am going to take it back next week and delete the y then run a dual system to improve flow.
Below are some photos of the work. For most folks doing something like this it won’t be that hard, my setup is difficult because of the rear long arms and air suspension. They really make the rear end difficult to navigate.

Here is the very back, passenger side. You can see my relocated charcoal canister. Had to move it for the longarms too.

Looking rear. You can see how tight it is with the Clayton rear long arm bracing and arms .

Passenger side. If you are needing to meet CA standards you won’t be able to do this since the cats need to be very close to their position and orientation from the donor vehicle.

Drivers side

 

[Skruffy]

I have about 20 miles on the new setup and have a couple problems. Primarily the transmission wants to shift into higher gears way way too early. It will be in 4th gear at 15 mph. The GM computer was reprogrammed with the correct tire size and axle ratio but the transmission didn’t get the message. My tap shifting function is also not working, likely a programming error as well. The wiring for the tap shift module is super simple an all checks out.

I found a shop locally that can reprogram the transmission control module without me having to remove it which is good because taking it out requires removing the pan and is a pain.

The other problem I am having is a code P0452 which is low voltage for the gas tank pressure sensor. Not too worried about that one for now but will fix it eventually.

Still have the problem of the hood too...

 

[notAhoser]

That exhaust is mean. Glad I don't like in Cali Are you getting any other codes at all or what's all turned off? As far as trans tuning goes, a 6L80 is a different beast so don't let just any id10t tune it. You never have to take the TCM out of the trans to program it, either. Do you have HPT or EFILive?



At low load they shift at low RPM and lock the converter up to keep RPM low. FWIW tap shifting isn't going to make you happy - it's slow as balls if you're trying to go fast, but if you just want manual control it's fine for that. But it will not hold gears like you might want (again without tuning for it).

 

[Skruffy]

That exhaust is mean. Glad I don't like in Cali Are you getting any other codes at all or what's all turned off? As far as trans tuning goes, a 6L80 is a different beast so don't let just any id10t tune it. You never have to take the TCM out of the trans to program it, either. Do you have HPT or EFILive?



At low load they shift at low RPM and lock the converter up to keep RPM low. FWIW tap shifting isn't going to make you happy - it's slow as balls if you're trying to go fast, but if you just want manual control it's fine for that. But it will not hold gears like you might want (again without tuning for it).

A couple other codes related to the same gas tank pressure sensor.
I don’t have any way of programming the TCM myself. If I had to send it off for programming I would have to remove it, that’s why I was happy to find a local shop. I don’t know much about the transmission at all. What should I be on the look out for as far as programming competency?
I wanted the tap shifting for controlling downhill speeds while towing other than that it is useless. I have it in other cars and never use it.

 

[Skruffy]

The first casualty from all those horsepowers. Didn’t expect it to manifest here but it did.
Gave skruffy a little throttle on a straight away and ripped the sway bar up so hard it bent the brackets and cracked the welds on both sides. This allowed the links to twist and when it came back down bent this one.
It is clear that the stock mounts won’t be up to the task. Will have to fab up something stronger. Then break the next weak link. No doubt this cycle will continue for quite some time.

 

[Anak]

Dayum...

With that kind of power you need to be thinking about some serious chassis bracing.

What kind of frame reinforcement have you done already? Any sort of cage that you could tie in up front?

The situation you have is reminiscent of what guys were doing with big blocks in 4wd square body Chevy trucks. The factory didn't build big block 4x4s because they knew better than to do that, but guys went ahead and dropped them in anyways since you could pretty easily swap them in. But the chassis really couldn't handle it. Guys would end up shattering their windshield if they got on the skinny pedal in 4wd. You can pretty much bet that if they shattered the windshield there was a whole lot more that got rearranged all of a sudden and the truck was totalled. I paid attention to all this because I had a big block swapped Suburban (454 with nicely ported heads and good cam). I had to remember not to be stupid with it.

Point being, make sure you beef up the things that you can't afford to break. The unibody construction certainly isn't up to the hot supper you are giving it. There are some macro level considerations here.

 

[Skruffy]

I welded on a full frame stiffening kit a few years ago, and the Clayton’s off road fourlink rear provides some serious cross bracing in the middle. On the very front I strengthened the cross bracing when I installed the intercooler heat exchangers.
So I am a bit better off then I would be without any of that.

 

[Anak]

That should help.

I think what you really need is something to box in the front of the chassis, and by box in I mean something like a torsion box, strengthening the unibody between the firewall and the front "frame horns" (if I can call them that).

I know some sports cars add braces between the shock (or strut) towers. That might be helpful.

What would probably be most ideal would be tubular bracing running across the front (upper radiator area), tied in to the "frame horns" and tied in to the cowl area, and then that tied in to a larger cage structure to give rigidity to the entire vehicle.

There are aftermarket cage options that can be ordered pretty much off-the-shelf. As far as I know those are just for the sake of protecting the occupants in the event of a rollover. One of those could work as a starting point though. From there you would need to add everything for the sake of the engine bay, and much of it probably needs to be built such that it can be unbolted for servicing purposes. Not a casual endeavor, and probably more than you intended to bite off for the sake of this build.

You can try just adding engine bay bracing, but my fear is that if and when you find out that was not adequate you willl also find yourself looking for another chassis to transfer everything over to. I think that is a less pleasant prospect than fully bracing what you have already built.

FWIW, I own a similar conundrum in the form of a '68 Camaro with a built 396. I did the motor over 25 years ago. Since then I have put less than 1,000 miles on the car. It currently sits buried in a corner of my shop and will remain there until I have kicked out the last Varmint. Once I tear back into it a full cage and seriously upgraded steering and brakes are on the agenda. The objective was to build a fun car. The problem is I went too far and the result as it sits is a destructive force. Taming that is going to cost more than what I have already put into it.

 

[Skruffy]

That should help.

I think what you really need is something to box in the front of the chassis, and by box in I mean something like a torsion box, strengthening the unibody between the firewall and the front "frame horns" (if I can call them that).

I know some sports cars add braces between the shock (or strut) towers. That might be helpful.

What would probably be most ideal would be tubular bracing running across the front (upper radiator area), tied in to the "frame horns" and tied in to the cowl area, and then that tied in to a larger cage structure to give rigidity to the entire vehicle.

There are aftermarket cage options that can be ordered pretty much off-the-shelf. As far as I know those are just for the sake of protecting the occupants in the event of a rollover. One of those could work as a starting point though. From there you would need to add everything for the sake of the engine bay, and much of it probably needs to be built such that it can be unbolted for servicing purposes. Not a casual endeavor, and probably more than you intended to bite off for the sake of this build.

You can try just adding engine bay bracing, but my fear is that if and when you find out that was not adequate you willl also find yourself looking for another chassis to transfer everything over to. I think that is a less pleasant prospect than fully bracing what you have already built.

FWIW, I own a similar conundrum in the form of a '68 Camaro with a built 396. I did the motor over 25 years ago. Since then I have put less than 1,000 miles on the car. It currently sits buried in a corner of my shop and will remain there until I have kicked out the last Varmint. Once I tear back into it a full cage and seriously upgraded steering and brakes are on the agenda. The objective was to build a fun car. The problem is I went too far and the result as it sits is a destructive force. Taming that is going to cost more than what I have already put into it.

I had no intention of ever having a supercharger in here, but when I cut the hood off that camaro I couldnt resist. I dont have any sort of cage right now and never had any intention of making one but the thought of transferring all this to another chasis only to put a cage on it is repulsive. I am considering buying a throttle control module that will detune the trhottle response making me have to work a little harder to break things.

 

[Anak]

I get it.

I could not have resisted either.

I have built myself into corners like this time and again. At least they make life interesting. And they inspire creative thinking and sometimes really cool solutions.

I look forward to seeing what you come up with.

 

[Scrubber3]

Any updates on this beast?

 

[Skruffy]

Been out of town.
I welded up some new sway bar mounts yesterday. Will take it out on a shake out trail today and see how it does.

Monday I will get the exhaust finished and try to get my transmission reprogrammed so that I can manually select gears. I also need to take it to an ac shop and have some poor guy plumb in the remainder of the ac lines. That is gonna be a miserable job for somebody.
Still need to get off my butt and take care of the hood. I called around a few places in San Diego and nobody would touch it.
If any of you folks know a good shop that could do it let me know!

 

[Anak]

Give GA Coachworks a call (Midway district, corner of Hancock and Hicock). I know he has guys who can shape metal (English wheel and such) and takes on custom work. Just a hood might be too small of a job though.

You could also try calling Merlin's Auto Body out in El Cajon/Santee. That was Gale Skinner's business. Metal shaping was very much his thing, but he may be fully retired by now. OTOH, a small job such as yours might be a good match for him. However, I doubt he would paint it, though he may be able to connect you with someone who would.

 

[Skruffy]

Give GA Coachworks a call (Midway district, corner of Hancock and Hicock). I know he has guys who can shape metal (English wheel and such) and takes on custom work. Just a hood might be too small of a job though.

You could also try calling Merlin's Auto Body out in El Cajon/Santee. That was Gale Skinner's business. Metal shaping was very much his thing, but he may be fully retired by now. OTOH, a small job such as yours might be a good match for him. However, I doubt he would paint it, though he may be able to connect you with someone who would.

Thanks Anak. I will give these guys a call Monday.

 

[Skruffy]

I took Skruffy on a shake out trail yesterday. We went to the Minnewawa Truck trail. Not a hard trail by any stretch of the imagination, although there are some steep routes that are covered in loose rocks. At any rate Skruffy cruised through it like it was a mall parking lot. No over heating problems. The only real issue is the lack of programming for the transmission. It wants to shift all over the place when it is in four low. I really need to get it sorted so I can manually select the grears.


I also just posted a 5 second video of a little throttle blip. Super fun.


https://youtu.be/0BeBxsLCLos



I seem to be getting around 18mpg too. I need more data to get a better estimate but so far that is a 50% increase from the 4.0 with a 500% increase in power. Pretty good deal!

 

[Skruffy]

I took my Jeep to Transmasters in escondido and they were able to reprogram the TCM to accept the tap shifting inputs. It is working now and for that I am very grateful.


If one of you is crazy enough to try this the problem was that the TCM was programmed to receive the input signal on pin D4. It needs to be programmed to receive on pin D6.



This shop also has a dyno and man oh man and I tempted! I dont think I will be able to resist.

 

[Skruffy]

I took my Jeep to Transmasters in escondido and they were able to reprogram the TCM to accept the tap shifting inputs. It is working now and for that I am very grateful.


If one of you is crazy enough to try this the problem was that the TCM was programmed to receive the input signal on pin D4. It needs to be programmed to receive on pin D6.



This shop also has a dyno and man oh man and I tempted! I dont think I will be able to resist.

 

[Anak]

Nice!

I don't think I want to change my XJ so much, but I could be tempted to swap an LS into a V-8 ZJ. Watching Vanimal's ZJ with his front and rear long arm suspension has left me wanting to build something along those lines. The Bride will probably be upset with me if the right ZJ comes across my path needing a motor.

 

[Skruffy]

If I were to start all over I would absolutely go with a ZJ. ZJs are much quieter and generally less Spartan than the XJ. I would also consider going completely hog wild (again!) and buying a totaled wk2 with the eco diesel and putting straight axles on it. If that was done correctly it would be an amazing vehicle. Especially if the thing already had body damage then I would never have to worry about that.

I got my new sway bar links in and that makes a huge difference. No longer weaving all over the place.

I locked the rear axle and gave it some throttle yesterday too. Achieved burnout nirvana. A life long goal of mine is to do a four wheel burn out. I fear that I will snap a driveshaft collar but will have to try it eventually. I am pretty sure skruffy will do it with out much effort.

 

[Skruffy]

Folks,
I will be headed overseas for about 7 months so there won’t be any updates until I return. I appreciate all of the interest, enthusiasm, support and advice!
Still have that problem of the hood....