Haha I know that sounds weird but I am not getting the technical expertise in the wheels&tires section that I am used to in the forced induction section.

I have a 4000lb target weight Jaguar XJ6 that's in the process of an 346ci LS1 turbo, designed for about 625hp and 550ft/lb of torque, A4 trans and 2.88 Dana 44 rear (considering a change to 3.07 or 3.31) I know I can sneak C4 ZR1 17"x9.5" wheels on all four corners, but am pretty sure I cannot get 11" wide wheels in the rear wheel wells. I see a lot of you on this forum are running those or similar wheels.

How much is this going to hurt my traction when I jump on it at a red light, or my times in the 1/4 mile? Any advantages w/wider vs. taller? I know forced induction cars generally have more low end torque than built up N/A cars. Wish I could find an FAQ to explain some of this but your personal experience is probably more valuable.

Thanks, -Dave

 

not if youre talking turbo....they have to spool up....so youre torque kicks in as the turbo spools, so you might have traction at 40, then the turbo spools, and your sideways until 90 mph when you regain traction. off the line na has all its power, so its going to be way more torque-y off the line aka down low.

 

I meant more torque lower in the RPM range.... a tuned N/A setup will hit peak torque (say 550ft/lb) high in the RPM range while a turbo setup can be deisgned to hit that number around 3500rpms. I'm also running an auto so no winding it up and dumping the clutch, either... I see what you're saying but it doesn't really have to do with my setup.

What I'm really lookin for is the tire/traction info.

 

I dont think it would make much difference at that power level on a regular street tire. Good luck with the project though.

 

Keep the 2.88 gear. At that vehicle weight the car will be fast but you should be able to hook it. That's pretty heavy.

 

Really? you're right... 4000lbs is VERY heavy for a car you're trying to make fast... and it's more torque you're going to need to pull that weight around. That's why I thought deeper gears would give me the torque I need to haul all that weight around.

After I have it up and running I will wind up taking the rear out anyway to get a locking rear end in... right now it has an open carrier.

Thanks for the insight though!

 

I had a 95 XJ6 that I absolutly loved and am even considering a new one again. There's just something ageless and sexy about a Jag

Your 85 body is almost identical in dimension to the 95 XJR that came with 18X11 rubber, so I don't think fitting big rubber will be your biggest hurdle. Unless you are going to replace the entire driveline I doubt the stock piece is up to the task.

I'll be following this project

 

Keep the 2:88's and see how it pulls..... If you need a deeper gear do it later. I would be more worried about keeping your 4L60E together in a turbo 346 setup and that weight....

I would keep your eyes open for a 4L80E. You may need it.....

Nitto DR's are good for the street and drive well even in the rain. They last longer than BFG DR's and M/T DR's however they don't hook as well. The car will never be a corner carver so Drag Radials should be fine on it all the time. My car with Nitto DR's actually handled pretty well... then air them down... do a big burnout... and launch hard.

In 3,000lb RX-7's with Buick GN powerplants a 3:07 gear was about perfect. Didn't blow the tires off and put it at a nice RPM range when crossing the line. Another guy tried a 2:59 gear in his GN powered RX-7 and managed some high 10's with a 1.6x 60ft.... Turbos work well with more engine load.... meaning less gear multiplication.

Sounds like a cool project. A 9.5" wide rear tire should provide good traction paired with a drag radial. On a true radial street tire and 600hp/550ft/lbs you can forget about traction in 1st and 2nd most likely.

You should look into alchy injection for the beast.

What size compressor wheel on the turbo? Homemade kit?

 

The M/T drag radial (275-40-17) hooks way better than a Nitto (315-35-17). I use the fatter Nitto for the street and the M/T for the track. I am amazed at how the M/T bites. The weird thing is you don't want to heat them up, either a small or no burnout, otherwise they spin.

 

Yea, the 2.88's will be the last thing I change. I will almost certainly go to a 3.07 because I will have no problem picking up a used ring&pinion/locking carrier set for a bargain price. A V-8 converted Jaguar message board I chat on finds the 350ci/700R4 setup with the original 2.88's to be a good combination and offer excellent fuel economy, so at least I know I'm in the ballpark.

Haha and yes, I am a little worried about that 4L60E too, but I plan on dealing with that when it becomes a problem. I also hear hooking up/traction has a lot to do with whether or not your 4L60E lasts.

Finally, I just don't think I want to use drag tires. There are a lot of twisty roads where I live and the Jaguar's fully-independent suspension makes it surprisingly nimble for such a large car... so I definitely want to keep road tires. The converted car with turbos will also be closer to about 3800lbs if everything goes properly. Will there be a big difference going from 9.5's to 11's on street tires?

Alky is out... I would rather stick to pump gas. I am on a strict budget!

And yes a homemade kit. I bought the engine mount adapters I need but will still have to do some fabrication. I have still not mapped out any compressors yet because I am not sure whether I am going single or twin. I will make that decision when the stock crank/forged rods&piston shortblock is mounted in the engine bay.

Feel free to hit me with any suggestions!! Even if I can learn one little thing to make a difference on my system, it's worth it! Thanks!!

 

That's an interesting project.

I use Bridgestone RE750's. Real nice tire, especially for the price. I've had 245/50-16, and now have 275/40-17. There's not a whole hell of a lot of difference between the RE750 sizes, but even the RE750 245's were a lot better than the 275's with Goodyear F1's, or 245 GSC's. I hear good things about KDW's, but they cost, and all the comparison's I've seen had them the same as RE750's.

I'm not into drag racing, and I plan to do more road racing this year. These were surprisingly good around Lime Rock (for street tires). I embarassed quite a few very expensive cars through the turns.

Whatever you get, street tires will spin heavily with that torque. Drag tires would cure this, but you don't want that, and I agree. The only other thing is autocross/road course tires, and those won't last. They will probably spin too. That open diff absolutely needs to go.

625hp/550tq would be strange. Why would you think you would get that with a turbo? Those are supercharger numbers. Turbo LS1's with stock engines, and especially autos would have a much higher tq number than hp. 550hp/625tq is more like it.

As an example, I have 480/525 right now. Right now, from a roll, I can get spin in 2nd at 4,500 and up. Not uncontrallable in a straight line, but you can't floor it in second through corners. 3rd is fine. In 30deg temps, I can get a hint of spin in 4th at the same RPM. Reason is the tires are colder, and the car makes more power.

The other thing to think of is the transmission. With any kind of sticky tires, it will not last 10 seconds of WOT. Its not an exageration. With street tires, at least you get spin, instead of a broken trans.

Sounds like a fun car.

 

If you don't plan to run drag radials keep the 2.88 gear.

 

Thanks... a lot of people have said that To sum things up I want AN M5 KILLER and to get that I can't compromise with drag radials!! I did expect to have some traction issues from the start. Thanks for the tire info, I will need to go back to that when I am ready to put the tires on. Looks like it will be 9.5's (AGH) and not 11's.

As far as the HP and torque numbers, that is what I am finding with my calculations. Of course they are crude and I had to estimate some things, but that is the kind of output I am preparing the car for. The rear independent suspension needs improved radial arms to keep the wheels in toe during heavy acceleration, etc.... so I am just building with those numbers in mind. If it's more, GREAT!! If it's less, well then I will keep tweaking. I am trying to stay under the 1000CFM (or about 512g/sec or something like that... I did the conversion once already and it's 100CFM) of airflow that the computer is limited to... above that it's more guessing and hardcore tuning, and the motor stops adjusting for atmospheric and weather conditions.

I think you're right about the trans, too... maybe not being able to hook up real well will be better for it.

ProStockJohn: note taken and thanks.... I just might be sticking with the 2.88 or something very very close to it.... but I need to find a locking carrier... I think everyone will agree with that!

 

My f'law has a 83 Jaguar Sedan and I can tell it's pretty heavy. It has a T400 trans stock.

 

Hey Boss...

I think you've got a cool sounding project. Should be capable of pulling off the sleeper role, if you want to, or look really cool dressed up.

I don't know that I have any good tire suggestions. I would be looking at as much tire as I can stuff in it, even if that meant mini-tubs / wheel-well mods. More tire is rarely a bad thing, especially with the weight you've got.

Somebody earlier suggested alky injection, and it was summarily dismissed as too expensive. I don't think you followed the suggestion. I don't think anybody is suggesting you convert to alcohol only. Rather, they're suggesting you use alcohol (and probably water mixed 50/50) as a boost fluid to help prevent detonation under boost while using pump gas. Search for water injection. Or check out SnowPerformance.net's website. They've got a fair bit of info available on water injection.

Lastly, I'd be real concerned about how long the 60E is going to live behind that kind of power and any kind of traction. Until you fix the traction, the trans will have some protection, but once you fix the traction issues, the tranny is likely to live a short period of time with that level of power and weight. The 80E is really the solution, but its heavy, takes a bit more power to spin, and is more expensive than a 60E. But for most folks who get tired of breaking 60E's and don't view a 3 speed as an alternative, its about the only choice (besides running a TH400 & gear vendor's overdrive box).

Good luck with the project, post pics when you can.

'Dreamin'

 

Thanks man! I am probably going to put some plastic fiberglass bumpers on it so we'll see what it looks like

The alky injection is always an option but I am not designing it into the system. I am going to start to consider it if I run into heat or knock/detonation problems. I plan on intercooling and running moderate boost between 10 and 14lbs. I also plan on cooling everything very well, so I am optimistic. Jaguar also used a fuel cooler that was integrated into the A/C system and I am considering that as well.

I am considering modifying the insides of the wheel wells and am definitely going to dolly the inside of the fender lip around a little to avoid any harmful contact. I have a feeling I am going to need all 11 inches of tire haha

That T400's were stock on V12 cars, but I want 4 gears. The 4L80E is good but heavy, and more importantly would not be an easy fit in the chasis. I am considering a 4L65E... let's see if I can come accross one at a bargain price! Would a good rebuild kit do me much good on the 4L60E?

check out the current pics at:
http://www.buyrcars.com/jag.htm

I just pulled all of the leather interior for reconditioning, so you will see some mroe pics soon!

 

No my f'law has a 6, and it has a T400. Or a T350.

 

I have (2) stock used working Buick GN turbos (T3/T4 hybrids) that make about 350-375rwhp each max. Spool on a 346ci V8 would be excellent if not instant.

email me for more info if you want to buy them: gnx7@hotmail.com

Get a 4L80E or rebuild the 4L60E a few times a year for more $$$. The weight tradeoff is worth the reliability aspect. 3800lbs is very very heavy.

You can flip the 6.0 truck manifolds around and make a turbo system that way (either twin or single). They have been proven to be good to over 1000rwhp+.. plus being cast they won't crack like headers you TIG'd up out of tubular s/s or mild steel. The stock manifolds (cast) would work well also.

Alchy injection is injected under WOT in conjunction with your normal pump gas. It is like having 100 octane in the tank vs. 91/93 which allows more timing and lots more boost. Boost makes power... and without it you'll be pressed to meet your goals. A good kit is about $400.... and worth it on any turbo car driven on the street. You don't use any alcohol until you go WOT anyway. Pays for itself if you were to run 100 octane in the tank instead.

You have a big project ahead of you. Take breaks when needed so you don't get burnt out.

Good luck,

-Mark

 

He doesn't need alcohol injection to make 620 HP on a 346" LS1.

 

Looks like you're well on your way to getting a fresh bullet in the chamber!

I'd suggest that you think seriously about tranny choices. I don't think the 60E will put up with 600+ hp and similar torque for long if you get it to hook, especially dealing with the weight. If you want proof, check out the truck section of this site, there are a number of trucks with turbos busy breaking 60E's & 65E's and getting frustrated about it. They do have a bit more weight (you're looking like 4000, they're probably in the 5000+ range) but probably similar power levels. The 65E is an upgraded unit, but it still lacks the brute strength of the 80E.

I'm pretty sure some later model Jag's came with the 80E (the 80E didn't come out until 91, so I'm sure it was after that, probably mid 90's, but I'm just guessing there). Whether it'll have any chance of fitting your Jag without serious floorboard massaging is something I don't know.

And if you go looking for a tranny, later is definitely better (you probably knew that). I'd be looking for the newest lowest mile tranny you can come up with (for the 65E or the 80E / 85E). I don't know about the 60E / 65E, but for the 80E / 85E you want a 00 or newer tranny, thats after their last major round of revisions.

And as regards alcohol injection: Most people think of it as a band aid. It doesn't need to be. You probably can get all of the benefits of a huge front mounted intercooler without the weight and plumbing. But that's just my $0.02, it your project.

Good luck under the "bonnet"

'Dreamin'