Power to weight Ratio: Why are XJs slow?

[88JeepXJ]

Did you use the craptastic auto from the ZJ or the AW4?

 

[5.2poweredxj]

I used the stock V8 auto. It was fine for it until I had very hard day in the woods trying to get through 3 feet of snow without any lockers are winch. That was the day I burnt up the reverse band in the tranny. My current tranny in the my Zj was built up so it won't do that again. Rebuilt it myself with help of a 20 year pro.

 

[88JeepXJ]

So we weighed the XJ. 1995 2dr 2wd AW4, we've gutted the interior of all but the driver's seat, dash and small things like doors skins, front seat belts etc. The exterior is still stock except for removal of the roof rack and this XJ still has stock 15" steel wheels with 225/75 tires, AC (working!), wipers, and all the engine bay stuff.

2865lbs measured with a four wheel racing scale (pretty accurate). Corner balance is pretty good (about 50.5%) but front to rear is a bit off (about 55% front). I'm really hoping to shave another 100lbs which should be easy.

 

[Dr. Dyno]

What are some 1/4 mi times from modified XJs? How difficult is it to get an XJ into the 13s?

My most recent was 14.70 @ 94.1 with my stock cam "poor man's" 4.6 stroker, full street trim, and 200rwhp/254rwtq on the dyno. Best ever with full street trim was 14.55 @ 95.2 when I had the Crane 753905 in my stroker (before one lobe and two lifters called it a day at 34k miles). This was with my XJ at a curb weight of 3450lb (all three skid plates and roof rack bars removed) with me at 175lb.
It's not impossible to get an XJ into the 13's with a naturally-aspirated stroker but your chances are much better with forced induction (including nitrous) on a stroker.

 

[88JeepXJ]

My most recent was 14.70 @ 94.1 with my stock cam "poor man's" 4.6 stroker, full street trim, and 200rwhp/254rwtq on the dyno. Best ever with full street trim was 14.55 @ 95.2 when I had the Crane 753905 in my stroker (before one lobe and two lifters called it a day at 34k miles). This was with my XJ at a curb weight of 3450lb (all three skid plates and roof rack bars removed) with me at 175lb.
It's not impossible to get an XJ into the 13's with a naturally-aspirated stroker but your chances are much better with forced induction (including nitrous) on a stroker.

That's not bad at all at that weight! What do you have for gearing and tires?

With my XJ at almost 600 lbs lighter it should get into the high 13s with a good run assuming same power. I'm thinking turbo on an otherwise stock engine. I just don't know how much boost i'll have to run to get 200rwhp.

 

[5.2poweredxj]

I know my jeep at full weight with the V8. The big bumpers, tires, tools etc... weighed 4875 on local scrap scale. Haven't weighed my ZJ yet but I'm sure it would be more than that.

 

[srimes]

It's not impossible to get an XJ into the 13's with a naturally-aspirated stroker but your chances are much better with forced induction (including nitrous) on a stroker.

what's the advantage of forced induction with a stroker vs a 4.0? I was under the impression that the power limits of both were about the same, but I'm no expert. :dunno:

 

[88JeepXJ]

Do you mean 3875?? I can't see you bolting on/ carrying over 1000 lbs!

 

[Dr. Dyno]

what's the advantage of forced induction with a stroker vs a 4.0?

More HP/TQ with a stroker.

That's not bad at all at that weight! What do you have for gearing and tires?

Stock 3.07 gears, AX15 5-speed, no lift, ~75lb weight reduction, and 27.4" tires (225/70R15H).

 

[88JeepXJ]

I kinda wish we had found a manual trans 2dr 2wd XJ but 2wd is RARE up here and this thing is as mint as I've seen a high mileage XJ be. We have some ideas though.

I can't wait to get the 8.8 fabed up and see what the extra gearing will do for us.

 

[Johnnie Walker]

My best time for my stock XJ was 17.4 @76mph, that was a Sac raceway

 

[CherBear]

My best time for my stock XJ was 17.4 @76mph, that was a Sac raceway

How many thousands of miles did you have on it?

 

[seanyb505]

Miles dont really effect it that much if you take care of it. The guts of my 4.0 were flawless after 200k, and it never showed signs of lack of power.

 

[CherBear]

Miles dont really effect it that much if you take care of it. The guts of my 4.0 were flawless after 200k, and it never showed signs of lack of power.

I used to have a engine with 155K on it. One day it decided to take a shit...
Swaped in a 4.0 with 77k on it. Seems to be noticeably faster. Better compression perhaps? Idk, not much of a gear head (yet)

 

[88JeepXJ]

Mileage doesn't necessarily mean the engine will have problems but the chances are greater that there is more leak down, more oil burning (lower octane), and the accessories are starting to draw more power to turn (bad bearing etc).