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supercharging my xlr

drive2fast

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Dec 12, 2019
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bc canada
My XLR/V(s)
2007 xlrv black, 06 corvette vert, 70 amx black,08 xlr black
Just got a 2008 non v car. I have 2 brand new complete gm eaton superchargers that fit the v models. Will the stock v supercharger from the 4.4 northstar (2006 to 2009) motor physically bolt on to the 4.6 northstar motor ?.Yes I know about the specs on the internals of both motors and adding power can cause problems and I will need different hood, pullys, intake tubing ect. but I work on cars a lot and like to modify them. Just hope someone knows for sure before I pull the stock intake off to test fit supercharger.
 

Gord

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Montreal, Canada
My XLR/V(s)
2004 #67
Hi & welcome!

I'd wager the time it takes to lift the intake, that it would be a bolt-on. I'd also wager that the electronics etc may be a bit of a pita, so perhaps study all the necessary extras and engine management that the 'charger may require. Quite possibly, it may be less costly to buy a complete used 4.4 with wiring and electronics and the correct ancillaries. Sell a supercharger (or two) and buy an engine? ;)

From Northstar engine series - Wikipedia

LH2 (VIN "A")
The 4.6 L; 278.6 cu in (4,565 cc) Northstar was designed originally for transverse front-wheel drive applications. It was modified substantially in 2004 for longitudinal rear- and all-wheel drive use in the STS, SRX, and XLR, as well as receiving continuously variable valve timing on both intake and exhaust sides. The RWD (LH2) Northstar produces 320 hp (239 kW) and 315 lb⋅ft (427 N⋅m). An increased compression ratio of 10.5:1 enables most of the increase in power from the L37 and LD8 Northstars.


Year Model Power Torque
2004–2009 Cadillac SRX 320 hp (239 kW) @ 6400 rpm 315 lb⋅ft (427 N⋅m) @ 4400 rpm
2004–2009 Cadillac XLR 310 lb⋅ft (420 N⋅m) @ 4400 rpm
2005–2010 Cadillac STS 315 lb⋅ft (427 N⋅m) @ 4400 rpm
2007–2009 Cadillac SLS (China)

LC3
A 4.4 L; 266.7 cu in (4,371 cc) supercharged Northstar was used in the 2006 Cadillac STS-V and Cadillac XLR-V. The bore was reduced for increased strength and improved head gasket sealing. Variable valve timing is used on both the intake and exhaust sides. The STS-V engine produces 469 hp (350 kW) at 6400 rpm and 439 lb⋅ft (595 N⋅m) at 3900 rpm with 9.0:1 compression and the XLR-V engine produces 443 hp (330 kW) at 6400 rpm and 414 lb⋅ft (561 N⋅m) at 3900 rpm.


Year Model Power Torque
2006–2009 Cadillac STS-V 469 hp (350 kW) @ 6400 rpm 439 lb⋅ft (595 N⋅m) @ 3900 rpm
2006–2009 Cadillac XLR-V 443 hp (330 kW) @ 6400 rpm 414 lb⋅ft (561 N⋅m) @ 3900 rpm

HTH!

Gord ;)
 

pure zen

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Mar 12, 2014
Messages
830
Location
AZ
My XLR/V(s)
2005 Crimson Pearl XLR
If me, I would sell the 4.6 engine and both s/chargers and install a new crate engine:
.

19331507_B_540x360.jpg

.
.

Chevrolet Performance LSA 6.2L SC 556 Supercharged HP
 

Gord

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Montreal, Canada
My XLR/V(s)
2004 #67
If me, I would sell the 4.6 engine and both s/chargers and install a new crate engine:
Chevrolet Performance LSA 6.2L SC 556 Supercharged HP

Hmmm... couldn't do it. I wouldn't care what sort of horsepower an engine produces if it's still built with push rods. Maybe cool for lawnmowers, just too antiquated for the XLR (imho). Shocked it's in 'other' models currently...there must have been a surplus.

This is a really good read for anyone to understand current engine builds and one of the most clever bits that (hopefully) keeps them going. I bring it up because as we can read in the specs, the 4.4 was given plenty of attention to compression pressure and sealing ~ sealing reliability.

MLS Gasket Update 2017: Is there anything the MLS gasket can’t do? - Engine Builder Magazine

The durability of a 4.6 / 10.5:1 supercharged must have been pretty bad in testing or in math models for GM to make all the effort to do what they did. One would hope the 4.6 connecting rods were up to the task as well (I did not look if they are the same for the 4.4 / 9.0 S/C).

There does seem to be a patented head stud kit available for the Northstar - I know nothing about it. That mentioned, all the clamping pressure in the world isn't going to do it if the head isn't outright sturdy enough to remain flat.

I guess for 'modern day' compatibility, going to a Blackwing ( Cadillac twin-turbo V8 - Wikipedia ) would be more to what I feel the XLR might deserve. It is after all even today, quite a technologically advanced car, and wedging in something that yeah, makes some poop but has been around like...forever... I honestly wouldn't feel right doing. Blackwing...no personal experience and sad to say I've never been much for turbocharging. They just don't last - not yet. That said, I'd still try it - at least it would be something from this century.

Gord ;)
 

drive2fast

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Dec 12, 2019
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Location
bc canada
My XLR/V(s)
2007 xlrv black, 06 corvette vert, 70 amx black,08 xlr black
Swapping out with a 4.4 supercharged motor would be way more work than instaling the supercharger on the 4.6 motor. Average cost of the 4.4 motor that i can find is around $4500 (with low millage). A LSA with the supercharger is around $15000 and you still need all the bits and pieces to make it work in the xlr. The head gasket studs pulling out was addressed after 2000 and won't be a problem on my 2008. The supercharger only adds 120hp so its not going to kill the motor depending on how hard i push the car. The superchargers themselves are

almost worthless to resell as they only fit the 06 to 09 stsv and the xlrv cars and a used 4.6 motor might fetch $1200 to the right buyer. The eaton chargers are really durable and not many have failed . The superchargers i bought come complete with all the sensors, throttle body ect. I have a 2007 XLRV with 8000 miles on it and i LOVE that extra 120HP. I
will sell it if i can put the charger on my 08. The reason i would sell my XLRV is because they are selling for so much more money than the xlr's . I also have an 06 twin turbo corvette that makes 700 HP (300 hp more than the stock motor ) and have had no problems with it blowing up. I wish D3 cadillac was still around as they would know exactly what would work. Thanks for the replys.
 

long Tall Sally

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Aiken SC
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2008 xlr dove gray
yeah of all the parts gm dropped the ball on , taillights and headlights etc they seem to have made a zillion superchargers and still sell them at 2500 thru the dealer but ebay sold about 50-75 for 250$ -400$ I bought a couple just in case I ever get a tired V I can freshen it up cheap. I actually have an 05 engine tha tis low mileage and not worth anything 4 years ago motors brought 2-3000 for a 4.6 and they were hard to find . I saw a 50,000 mile 08 4.6 xlr sell for 700$ on ebay as there are maybe 100 motors on shelves now were people bought totals just for the headlights and taillights and a few other parts . I pulled this perfect 80,000 mile engine down to sell the VVT control valves and they are worth about what a motor complete is .I may pull the intake and compare to see if the supercharger looks like it will fit. swapping to a v motor would cost way more than it would be worth and the corvette is not an easy swap either. You would be ahead just to sell your car and buy a v or vette.
 

Gord

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Location
Montreal, Canada
My XLR/V(s)
2004 #67
Hi,
Geeze, yeah I just looked over on the eBay and $250 for one, less if you buy quantity?! Order up a gross, use 'em for doorstops or boat anchors! :lol:

So I borrowed some pics and it would be really cool if you do go ahead, to maybe make a thread here so others could follow along and perhaps do similar. From the pics... bolt on imho.

Eaton M122 SC lower.jpg
XLR intake manifold lower.jpg

That's quite a potent Corvette! Are you able to use all that power i.e. racing or decent places to get out and toss it around a bit?
Over this way, it's currently hopeless unless one decides to do track-days. Lousy and very, very busy roads with far too many distracted folks. :(

Have fun!

Gord ;)
 

Vetter

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Location
Michigan
My XLR/V(s)
2004 XLR
I've added a turbo to a small block chevy and a Ford straight 6 cylinder 300, the chevy is a common modification, but the 300 Ford was all done by scratch. Pressurizing cylinders in a engine all has about the same concept, the higher the RPM the higher the pressure which means the higher the pre-ignition problems. I can't imagine trying to get a 10.5 to 1 compression engine under boost running dependably on the street with pump gas, or even 110 octane for that matter. Obviously this is the reason GM dropped the 4.4 to 9 to 1 compression.
Depending on how GM dropped the compression on these engines, dished pistons or opened up the CC's on the heads, I would think at a minimum the heads would need to be changed if they would fit, because I'm confident they aren't the same on the 4.6. Dropping the compression would be a priority, among a complete computer re-program so the engine timing can be retarded per each lb of boost, which would require some form of boost sensor, which would be on the 4.4 but not the 4.6.
There's a lot to adding boost to a gas engine, especially if trying to make it a street driver.
 

Gord

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Location
Montreal, Canada
My XLR/V(s)
2004 #67
Cool projects!
I just looked for fun: rods, heads, pistons (obviously), all different by the part numbers. Indeed, to do a real sano job, it could be quite an undertaking today I'd think.

Unless perhaps there's some external method to be able to modify timing and boost pressure (pretty sure I've seen such a thing), and sort of side-step the existing controls. But now we're probably getting pricey sooooo....

I did find a 4.4 S/C engine for under $2K: https://modernimports.autopartsearc...ne-assembly?application=3748154988-2225320418

Makes me think after seeing that, (umm...ouch), a thread dedicated to XLRs 'definitely no longer in service' might be an interesting photographic record which the registry doesn't (yet?) cover.

Gord ;)
 

Vetter

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My XLR/V(s)
2004 XLR
Cool projects!


Unless perhaps there's some external method to be able to modify timing and boost pressure (pretty sure I've seen such a thing), and sort of side-step the existing controls. But now we're probably getting pricey sooooo....

Gord ;)

There certainly is a very good method to modify the timing with boost on non-computer controlled engines, I have a MSD 6 BTM box on my rock crawler with the 300 Ford, it works great and is only around $300. But these wont work on a computer controlled car, completely different animals.
Everything on a computer controlled car needs to interact together.
 

long Tall Sally

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2008 xlr dove gray
with worn out rings and leaky valves its most likely dropped from 10.5 to 9.5 by now on a well worn used engine. haha a good quality copper head gasket would most likely lower it to 10 to one but I really dont think its worth doing
 

Gord

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2004 #67
Interesting stuff!

Right, gotcha with that. Though if you could say, 'convince' the existing ECM that <whatever> is happening normally, then have the alternate unit do the real engine management. Of course it probably gets much deeper than that, especially with this car and I don't think I wouldn't go near an approach like that - I find it's 'fixing a symptom, not a problem'.

I'd be more the one if so determined to grab the complete 4.4 and it's appropriate ancillaries and do my best to do it right.

Gord ;)</whatever>
 

Vetter

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2004 XLR
with worn out rings and leaky valves its most likely dropped from 10.5 to 9.5 by now on a well worn used engine. haha a good quality copper head gasket would most likely lower it to 10 to one but I really dont think its worth doing

Not likely, compression doesn't escape small leaks as much as you may think even just ideling at 800 rpms. The pistons hit TDC and beyond far quicker than compression can escape. I've checked engines with 100,000 miles and they still have the specked compression as manufactured.
 

Vetter

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2004 XLR
Interesting stuff!

Right, gotcha with that. Though if you could say, 'convince' the existing ECM that <whatever> is happening normally, then have the alternate unit do the real engine management. Of course it probably gets much deeper than that, especially with this car and I don't think I wouldn't go near an approach like that - I find it's 'fixing a symptom, not a problem'.

I'd be more the one if so determined to grab the complete 4.4 and it's appropriate ancillaries and do my best to do it right.

Gord ;)</whatever>

Don't get me wrong, with the price of the superchargers right now it would be a cool project, I was considering doing it myself. I think if someone could get all the 4.4 electronics it could be done on the 4.6, but the compression would be the big obstacle. Even if changing the heads GM went to a smaller bore for a reason, and I wonder if they O-ringed the heads? But I'm not sure why that even would require a smaller bore, or perhaps they were worried about cylinder wall thickness? Under boost engines can require much more robustness.
 

drive2fast

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bc canada
My XLR/V(s)
2007 xlrv black, 06 corvette vert, 70 amx black,08 xlr black
My twin turbo corvette is 10.5 to 1 compression and the dyno tuners say its no problem as long as you don't go over 8 psi boost.The eaton supercharger only boosts 7 psi so with a proper tune it shouldn't be a problem, also both the xlrv and xlr cars use the same ecm and wiring but just a different loaded tune. There was 40 of these chargers for sale 2 months ago and there is about 10 left so if interested you should get one soon. The other thing to consider is how hard you plan to drive the car. When i drive my xlrv it is so much more responsive and fun to drive but i am not hammering it and taking it to the race track to beat on. So i don't believe this modification will cause any big problems.I am going to investigate this a little more before i start the swap.
 

Vetter

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My XLR/V(s)
2004 XLR
My twin turbo corvette is 10.5 to 1 compression and the dyno tuners say its no problem as long as you don't go over 8 psi boost.The eaton supercharger only boosts 7 psi so with a proper tune it shouldn't be a problem, also both the xlrv and xlr cars use the same ecm and wiring but just a different loaded tune. There was 40 of these chargers for sale 2 months ago and there is about 10 left so if interested you should get one soon. The other thing to consider is how hard you plan to drive the car. When i drive my xlrv it is so much more responsive and fun to drive but i am not hammering it and taking it to the race track to beat on. So i don't believe this modification will cause any big problems.I am going to investigate this a little more before i start the swap.

It's amazing to me what these computers can do with these engines nowadays, I never would of imagined getting 750 hp out of a car like they are on pump gas in some cases. What type of programming are you running on your Vette? Some how your ignition advance is retarding with boost, curious as to what type of turbo setup you are running, and who programmed the computer? Anything can be done with the right amount of money and expertise.
 

drive2fast

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Location
bc canada
My XLR/V(s)
2007 xlrv black, 06 corvette vert, 70 amx black,08 xlr black
I am running a APS twin turbo set up with meth injection to cool down the fuel charge. I have had it dyno tunned twice once at mopac in my area and once in bellingham wa. I have a boost a pump controller for extra fuel and just the stock ecm. I am at the limit of hp unless i upgrade the motor and everything behind the motor. When my car was built in 06 700hp at the motor was impressive and now guys are running 1000 hp at the wheels. My buddy has a new demon with 840 hp from the factory and he has run 9.65 in the quarter mile. I wonder where the factory hp wars are going, will the insurance companies put a stop to it like they did in the 70's
 

Vetter

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Messages
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Michigan
My XLR/V(s)
2004 XLR
I am running a APS twin turbo set up with meth injection to cool down the fuel charge. I have had it dyno tunned twice once at mopac in my area and once in bellingham wa. I have a boost a pump controller for extra fuel and just the stock ecm. I am at the limit of hp unless i upgrade the motor and everything behind the motor. When my car was built in 06 700hp at the motor was impressive and now guys are running 1000 hp at the wheels. My buddy has a new demon with 840 hp from the factory and he has run 9.65 in the quarter mile. I wonder where the factory hp wars are going, will the insurance companies put a stop to it like they did in the 70's

Very impressive! I would of never thought you could achieve even low numbers of boost with just adding a cooling charge and more fuel on a higher compression engine. Sounds like a cool setup.
It just shows how far different methods of technology have come, and I haven't been keeping up to date on the information.
I will be following if you decide to do this. I will do more research myself to find out why GM went to a 4.4 when supercharging, and see what type of tune they used. I would want to keep the driveability and dependability over speed atleast for my XLR. But maybe with adding a stock supercharger with a few mods that wont make much of a difference with the right tune?
 

Gord

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2004 #67
...My buddy has a new demon with 840 hp from the factory...

...It just shows how far different methods of technology have come...,

Hi guys,
In all truth I am / was, more of a bike guy than car guy, ...have either of you seen the current offerings from say, Yamaha or BMW? I really needed the 'facepalm smiley' as I read the specs the other day of the 2020 Yamaha R1 / R1M which for a liter bike, is now at 200 horsepower normally aspirated.

It fascinates me how quickly (bad pun) the technology is accelerating (sorry, bad pun again). And that's not just the engine what with bikes being a bit trickier handling-wise imho. Here's a link to the R1M if you're not aware and if it might interest you to read: 2020 Yamaha YZF-R1M Supersport Motorcycle - Model Home

See, I still can't believe that anyone with a wallet can walk in and buy one of these. For all intents and purpose, imho and in my ex-professional opinion, these sort of bikes should have always only be made available to people with appropriate credentials.

<sigh>Sadly, that's really not the case. Over on this end of the country, road-going motorcycles are all but gone due to the young go-fasters doing themselves in and causing the 'no fault insurance' scheme to become too costly, making street-able motorcycle riding pretty close to a thing of the past.

Anyway, take 200 hp / liter and do some math, and I think car manufacturers today may actually be holding back what could be currently possible. Gaak!

Gord ;)</sigh>
 

Vetter

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Michigan
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2004 XLR
Those bikes have to be crazy fast!
A friend of mine had a Hayabusa which he would frequently ride that thing above 200 mph at extended times, just crazy to me! I'm a Harley guy, like to cruise the speed limit and enjoy the scenery!
 

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