horsepower for less $

[JeepSpeed]

where to get, or who makes, fiberglass hoods for the XJ?


Rusty's

Awesome thanks, very cheap too. Actually a little too cheap. There is no picture, no description, no weight. I would have to research that alittle bit further before I would invest in that.

 

[Mike@Accurate]

RE; new downpipe: The divits in the pipe clear the driveshaft yoke at full up travel. OK to put a new pipe in IF you don't wheel. Bottom it out and you will be looking for the old pipe.
RE; TB boring: 62.5mm made exactly 3.25hp on the dyno. Boring out the hump WON'T make three hp and going to 62mm WON'T make 2 more hp.
RE; air pipes: ours made 8.25hp on the dyno and knocked .2sec off of 1/4mi times. (no blind faith here)
RE; spacers: you probably will need to bore it to match an oversize TB. I don't think they work at all though.
RE; cannister: OBDII trucks will throw a code every time they try to purge, just like when you leave your gas cap open.
RE; belts: my '97 no-air motor takes a different length belt than my A/C equipped XJ. There are idlers, but I think you may need to buy a belt from the donor truck to make them fit .

I think the best mods are an air pipe and exhaust. Most real power. If you feel like taking your Jeep all the way apart, and not doing a stroker, a cam swap is the next biggest power adder. (NOS not withstanding)
MIKE

 

[Dr. Dyno]

I think the best mods are an air pipe and exhaust. Most real power. If you feel like taking your Jeep all the way apart, and not doing a stroker, a cam swap is the next biggest power adder. (NOS not withstanding)
MIKE

Don't forget about porting the head. I saw a good performance gain above 3000rpm after I home ported the head on my old 4.0 without losing torque lower down. I know a CNC ported head will produce better gains but a carefully done home port job can still produce good results. The exhaust side is particularly restrictive and opening up the exhaust port throat/bowl/short side radius probably produces much of the HP gain from porting the head.

http://www.jeep4.0performance.4mg.com/head.html

Since the head has to be removed for a cam swap, a ported head will complement the performance cam very nicely.
A combined 11hp from a free-flow intake and bored TB sounds about right. A bored spacer will slightly lower the HP/TQ rpm peaks by effectively adding runner length, and produce a small gain in gas mileage.
IMO, the most restrictive part of the exhaust is the cat forwards, so replacing only the muffler or the cat-back won't do much. Replacing the cat and crushed downpipe will do a lot more, and will help you get more out of a performance cat-back.

 

[Gridikal]

In the exhaust situation, I just had my flowmaster super 40 put on today, I gained back the lost power from my dynomax "super turbo" and then a little bit more- not to mention it sounds 300% better.

 

[Mike@Accurate]

Dino,
"Don't forget about porting the head" ... Good call. I forgot. We got 16hp on a 4.0 & 20hp on a 4.6L. Especially if you are doing a cam and have it sitting there anyhow. Straightforward to run as well, no computer issues. MIKE

 

[ColoradoDave]

tons of weight can be stored up in the carpet too. There is tons of foam insulation under the carpet that stores up water adds lots of weight and causes rust. At the very least, pull the foam and insulation crap from under the carpet. you'll be amazed how heavy all that stuff is when you pull it out.

 

[cruiser54]

Man, what an old thread!!!!!!!!

 

[stroked88]

rawr!!! zombie thread!!!

 

[NorCalChris]

Very old thread. but I'm going to add to it.

Keep in mind the jeep was dynoed to prove all this. I'm not going to lie to sound cool on a thread from years ago. lol


I have had lots of different exhaust systems. I had some where the pipe ended after the muffler, i had open exhaust, and now i run a full exhaust all the way out the back like the factory had it. I went from a open exhaust w/ cat to a flowmaster muffler (i hate them, but that's a different story for a different day) with full piping all the way out the back. I gained BACK 4hp and 6 ft/lbs of torque that i had lost from going open exhaust.
I installed a K&n dop in filter and lost 1hp and leaned out my AFR. my renix engine doesn't meter the air going in, just manifold pressure. Luckily I have an adjustable Fuel Pressure Regulator. Made some adjustments and brought my AFR back to where I wanted it. Gained back the 1hp lost plus 5 more.
I indexed my spark plugs, and gained almost ten more hp.

Heres some advice. From the throttle body towards the filter your ducting should all be the same size. so if you run 62mm tb you want all the piping towards your filter the same size. Same with exhaust. if you run a 2.25 down pipe, you can go to a 2.5in in/out cat, you now need a 2.5 in/out muffler. and 2.5 in piping out the back. you dont want a 3in in/out muffler necked down to 2.5in piping out the back of the jeep.

 

[NorCalChris]

My jeep is a 90 4.0/aw4/242 with under 5k on engine. but 268k on tranny. I'm normally run 35x12.5 mtrs on steel rims. I have STOCK gears. Don't laugh or make fun of me I know, i know, i know. The last dyno run conditions were 93.99*f, 21% humidity. I installed two stock sized tires. I laid down 133hp, 175 torque. Sucky right? Well, consider a 25-30% loss through an automatic tranny plus tcase. Now this isn't no drag car, but its pretty good because stock ratings are 177hp and 220 ft/lb? so 177hp*.3=53.1. 177hp-53.1=123.9hp. 220ft/lb*.3=66 220ft/lb-66=154 ft/lbs
123.9hp/154 ft/lb of torque is whats expected to be laid down on a stock renix engine. I make 9hp more and 21 ft/lb over stock. not bad at all in my opinion.
It helps out when the turty fives are on. lol. Before all this it only laid down 106hp with 35s. :bawl:

 

[urban yan]

I laid down 133hp, 175 torque.

No one should ever say "laid down" and 133hp in the same sentence.

 

[NorCalChris]

haha. Say what you will.

 

[badron]

A late model intake sould be good for a more HP then most of the mods combined. Then a cam/lifters. Then a hoged out TB. Then a new poop pipe.

 

[cruiser54]

A late model intake sould be good for a more HP then most of the mods combined. Then a cam/lifters. Then a hoged out TB. Then a new poop pipe.

I thought I read somewhere that the late intake was good for 3 horsepower or less.........

 

[CherBear]

I thought I read somewhere that the late intake was good for 3 horsepower or less.........

Are you talking doing a late model intake manifold swap onto an older model?

 

[NorCalChris]

Are you talking doing a late model intake manifold swap onto an older model?

I believe that's what he is talking bout. I have heard it is not worth more then a few ponies, and haven't heard of any torque gains (although I'm sure there is some)

 

[Dr. Dyno]

I gained 2rwhp/4rwtq with the '01 XJ manifold swap and no other changes on my 4.6 stroker ('92 XJ). The biggest torque gain was 6rwtq at 3400rpm where it now peaks. I also gained ~1mpg in gas mileage so for me the manifold swap was worth doing since the manifold itself only cost me $53.

 

[yossarian19]

Well, somebody has to say it...
The biggest performance gains you can get on most vehicles will be... a good tune up.
Before you spend money on after market parts or porting the head, be sure you:
Replace cap, rotor, wires & plugs
Make sure your catalytic converter is in good shape
Replace O2 sensors as necessary
Clean the TB
Replace fuel filter, if applicable, and make sure the pump is healthy
have a fresh air filter
Run some injector cleaner (I've used Sea Foam, though I hear BGK44 is good stuff as well)
ETC
On my rig, replacing the worn-out cat did a lot more than anything else I messed with

 

[tone]

Well, somebody has to say it...
The biggest performance gains you can get on most vehicles will be... a good tune up.
Before you spend money on after market parts or porting the head, be sure you:
Replace cap, rotor, wires & plugs
Make sure your catalytic converter is in good shape
Replace O2 sensors as necessary
Clean the TB
Replace fuel filter, if applicable, and make sure the pump is healthy
have a fresh air filter
Run some injector cleaner (I've used Sea Foam, though I hear BGK44 is good stuff as well)
ETC
On my rig, replacing the worn-out cat did a lot more than anything else I messed with

Isn't it BG 44K? BG = brand and the 44K = fluid type or whatever? I haven't seen BG44K in years or a BG guy for that matter, where can I get some at? Haven't seen it since I worked for Goodyear years ago and only thought you could get it from the BG guy in the truck...

 

[yossarian19]

Isn't it BG 44K? BG = brand and the 44K = fluid type or whatever? I haven't seen BG44K in years or a BG guy for that matter, where can I get some at? Haven't seen it since I worked for Goodyear years ago and only thought you could get it from the BG guy in the truck...

Sounds like you know more than me already. Google search for it, though, and you'll find it available online.