Topic: Weight and Horsepower

[chrisfranklin]

I was reading something at the Turbo city site which suggested that 100lbs weight reduction on a vehicle = 10hp increase.

So I was thinking about weight reduction on a Wrangler (Im in LA, so I am on the road frigging all the time in parking-lot-speed traffic, so I have a lot of time to consider things like this).  Frankly, other than the back seat and spare tire, I couldn't think of much to get rid of (and my backseat got removed a long time ago).  Can you think of anything else that weighs something that should take a hike?

So, I guess you are left with doing things like replacing your hood, fenders, grill, gate with kevlar or fiberglass parts. Heck, you could replace the whole body with a kevlar unit if you wanted to.  Can you think of anything else that should take a hike?

(Yes, I agree, we should start manufacturing/mass-producing Carbon-Fiber CJ/Wrangler bodies and Titanium CJ/Wrangler frames in China; this might keep them affordable).    

And, keep in mind that you can get ludicrous performance out of the new Lotus Elise and that is nothing more than a light car running a 190 hp Toyota engine.http://

[Jeffy]

Problem with that idea is that with a Jeep, you're not only dealing with just the weight but also wind resistance.   Wind resistance will progressively work against you the fast you go,

I played around a little removing a bunch of stuff from my Jeep for a month.  I didn't notice much of any difference.  That was with removal of the front and rear bumpers, winch, rear seat, no spare, passenger side mirror, etc...

Another problem with your idea of carbon fiber and titanium is that stuff is expensive.  You're also sheding weight at the cost of strength.  Ever smack carbon fiber against something hard?  It's not pretty.

The reason why the Elise is able to do so well is that it weighs in under on 2 ton.  Aluminum chassis with a light weight engine and only room for two.

[Chowmaster]

the wind kicks my jeep's butt

if you must remove weight-
top, doors, carpet, dash, tailgate, rollbar, rear and passenger seat, fender flares, power steering pump, exra leafs in leaf springs, bumpers, etc
you could probably get by with only half the bolts on the chassis.
wiring harnesses. how many wires does it really take?
gun-drill the axle shafts.
speed holes in frame and body
the cool thing is you could sell all this stuff on ebay for a profit.

on a serious note, i did ditch my track bars and sway bars. that was maybe 30lbs?

[SMC4WD]

It's a question of having one without the other...

Dana 60 weight compared to a D35...  
Adding a winch...
adding steel rockers...
Desperately wanting to add a roll bar...

All that stuff adds weight...  

So if your building a truly trail worthy Jeep, weight can't be a huge concern.  If you building a competition rock crawler, weight is an issue.

If your driving it daily on the city streets, I guess that all you could hope for is better fuel mileage.  

It's tough comparing a Wrangler to a Lotus Elise

[Chowmaster]

i think the best thing to do is be sensible with add-ons.
a stock jeep is probably pretty light
keep tire size down to as small as you can stand.
huge bumpers, skid plates, tube fenders, rocker protection, spare tire racks, roll cages, etc are really cool but add a lot of weight.  only get what you think you will need. try not to bash into rocks, unless thats your thing.

[chrisfranklin]

Yeah Jeep Aerodynamics kinda subdues any gain brought on by dumping parts for weight savings.  Sounds like Jeffy has already walked that path.
Thanks for saving me the trouble.  

Don't know much more about Carbon Fiber other than what I've read in magazines that detail use of it in performance cars or airplanes.  Was under the impression that it was especially light and rigid.  Crashworthy? Yeah, well, probably not. Manufacturers probably haven't crashed a bunch of McLaren cars or smashed the floors on the latest Z06 Vettes.

But, I could go for a 2000lb SWB Wrangler that had all creature comforts, features, durability and avail. aftermarket mods of CJ/YJ/TJs (and aerodynamic adjustments).  Maybe you'll be able to buy an affordable, fully-built one by the time Haley's Comet comes around again.   Such a Jeep would probably have some excellent performance and efficiency advantages in addition to Jeep trail/rockcrawling strenths.

[lutzke21]

Then there's always the possibility of going on a diet... :?

[jagular7]

I placed this info under "TJ Pulling Camper Observation"

'Well, with yesterday off, I went and pulled my Scamp camper out of winter storage (basically I just hooked it up, secured any lose items inside, and pulled away). Took it to the scales to weigh it out with the TJ. My TJ w/out me in it and a 60# dog in it scaled at 3540#s. I've got a winch up front, stock front bumper, no rear bumper and a tow hitch frame. I've got 4+" lift, D30/D35 combo, 4.88's&lockers, 5 - 34" LTBs on 15x7 steel rims. Soft top with 1/2 doors. No AC. Rear seat. Maybe 10#s worth of tools.

My Scamp weighed in at 2060#s with a tongue of 240#s. Anything larger than 2000#s it really would kill the 4-popper. Even though I have a tired auto, I had to keep it up to 4500rpms just to keep the acceleration into 3rd gear at highway speeds. I couldn't make OD but I kept at 65-70mph at 3500rpms. Once I hit a hill, the little engine couldn't keep the rpms up nor the momentum. Slight hills was ok, but anything with an incline, forget it. Get down to 2nd gear and hold up to 4500 rpms till acceleration warrants to upshift to 3rd. There was some wind gusting, at some point it was hitting from the side. The TJ had to be corrected but it felt like no more than usual with a side wind. Rear locker I didn't feel either way. Only time I really took notice was on take off. The Jeep hood would be at an angle...cool, maybe lifting a driver's front tire when launching it...hehe.

I probably drove only 30-40 miles, but lost better than a 1/4 tank. Without the camper I wasn't getting anything close to 12 mpg if that. I've check codes and nothing shows on the speedo. However, I can't put no more than 12 gals in!!! Once winter is over, I'll be pulling the tank to check the inside out and get the 19 gals out of the 19 gal tank with the return fill line.

Hope this info helps.'

Do note the: weight of TJ, weight of camper, gas mileage, and rpms needed!!!

[jagular7]

Where is all that 3300# weight? Probably in the engine block and heads, trans, box frame, and sheetmetal.

In comparison to another small 4cyl 4x4, a Samurai, the Sami weighs in at ~2200#s loaded. The stock engine is nothing, but swap in a 1.6l and get nearly 1.5 times hp and torque. Swap in a 4.3l with tranny, run stock/ mod'd t-case, and better axles and have something small but comparable to a YJ/CJ/TJ with a V8, trans, tcase, and axles in performance to weight ratio, yet still weight near ~2600#s. Tires/wheels play a big impact on weight, so assume near same size. Samis frame is boxed and has crossmembers just like the TJ. Sami owners swap in D44 axles, Toyota axles, Wrangler leaf springs, etc. similar to some TJ owners.

Sami stock t-cases weigh 43#s. I just shipped one that I probably should have kept for an axle swap I'm thinking about.

So where is the weight on a 3300# TJ?
(3540#s -60# dog -100# winch/plate -80# tire/wheel difference from stock)