More HP from the 4.0

[chaser9478]

Ok usually it is suspension but you need HP to have fun too. I have the normal bolt ons on my 97 4.0. I am thinking of adding a 99+ intake, a 62mm TB and 24lbs hour injectors. Has anyone done this? Is it worth the $300 it would take? What have you guys got the best results from?

 

[CanMan]

I noticed smoother ecceleration through the powerband with the 99+ intake, but not much else. It can help in conjunction with other mods. Didn't notice anything when I bored out my TB either. TB spacer is useless as well.

Free flowing exhaust(get rid of the crimped factory down pipe at the header collector).

An intake is useless without routing it somewhere other than in the factory spot. It'll just suck the hot manifold air, so something to the other side of the engine bay would work best.

Larger injectors wont do much if the engine doesn't demand more fuel. Stock ones are rated at 23.6 or so anyways.

A teardown of the engine with a cam replacement, headwork, more compression, ect.. can land you more power numbers but will result in emptying your wallet.

No bolt ons that are cheapish will net you huge gains in power numbers(exc. NOS, its cheapish).

 

[chaser9478]

Thanks for the input. I have the THOR intake. I recently added it and I really like it. It replaced an AFE rig so I could put the 2nd batt under the hood. I also have 2.5 exhaust with a banks header and flow master. I plan on a stroker when this motor goes but untill then I want to squeeze all the power I can. I am also getting things I can transfer to a 4.6. I think your right about the injectors. I will probably go with the intake and tb. I mainly want a tb that doesn't whistle. Did you bore your own or go with an aftermarket one?

 

[CanMan]

Bored it myself, easy enough to do. Had a few extras incase I screwed it up, but it went well the first time.

 

[chaser9478]

Does it still make that whistle? Did you replace the butter fly? I saw a kit some where that had a dremel bit and a new butterfly. Either way any instruction to offer?

 

[Talyn]

You can't use a dremel to bore the throttle body out correctly. You need to have it machined correctly for larger that 60mm. At 60mm you are just removing the taped under the butterfly.... you go into where the butterfly sits and you are screwed.

The 99+ intake woul dbe a good upgrade... and the throttle body is nice too... i don't know what a thor intake is though.. No reason for the larger injectors until you do a stroker

 

[CanMan]

Well, guess it wasn't 'bored', just took down the lip or step under the butterfly. Doesn't whistle. A bigger TB doesnt do too much if the manifold isn't matched to the same size.

THOR intake system:

http://trailheadoffroad.com/html/xj_cowl_induction.html

 

[PapaPump]

is there a whistle w/ a bored throttle body? i know my fipk whistles like crazy around 3000...not sure where the turbulence is, but it'd be nice to get rid of that.

 

[Talyn]

It depends on the air flow a lot. Most bored TBs will whistle if you don't round off the Idle Air Controller ports. I've also heard unmodified TBs whistle with just a CAI.
But, yes you can bore your own by removing the taper under the butterfly. You will only get 60mm, but it is still an improvement over the stock 55mm.

 

[chaser9478]

I am looking at the BBK TB. It is $230, the painless one is around $400. There is a guy on E Bay who has them for $175 guarannteed not to whistle.

By far the biggest difference I have felt so far was doing the exhaust. I like the gas mileage I pick up as well with the mods. Horsepower comes from effciency. Every little bit helps in both areas.

The tb kit had a sanding drum not a dremel bit......sorry

 

[Talyn]

www.strokerjeep.com I used him and I know several other people that have. Screw paying 230-400 for a throttle body.

 

[chaser9478]

Thank you! Thats what I wanted to hear! I was leaning that way but I wanted to hear from someone.

 

[chaser9478]

A little off topic, but I notice you too are in VA, I am on the Eastern Shore. I like to go to Edinburgh to play. Do you go out there?

 

[tbburg]

Here's a writeup on home-boring the TB. He mentions rounding corners to stop that whistle, but doesn't have a closeup of the work area;
http://www.go.jeep-xj.info/HowtoTBboring.htm

'Rest of Go-jeeps writeups are worth a read too.
http://www.go.jeep-xj.info/

 

[chaser9478]

I think I will bore mine tonight. I can blow $10 before the first. I already have most everything and the jeep is all tore apart anyway. So this is definitely a "why not?" thing.

 

[Ronbo]

www.strokerjeep.com I used him and I know several other people that have. Screw paying 230-400 for a throttle body.

"Sorry, the website www.strokerjeep.com cannot be found"

 

[chaser9478]

Money is the largest restriction of power for my XJ........Being a disabled vet sucks.....but I guess the same goes for everyones HP problems.....

 

[chaser9478]

Okay. So for the boring should I only bore the bottom or the top and bottom? I have a drill press, so I am going to get a sanding drum for it. I think a dremel will put a fix to the whistle.

 

[Talyn]

"Sorry, the website www.strokerjeep.com cannot be found"

Oops.. thought I corrected that. Its www.strokedjeep.com

Okay. So for the boring should I only bore the bottom or the top and bottom? I have a drill press, so I am going to get a sanding drum for it. I think a dremel will put a fix to the whistle.

If you are doing it yourself then only the taper below the throttle body.

I haven't gotten out to Edinburg yet

 

[XJRubicon]

Ok usually it is suspension but you need HP to have fun too. I have the normal bolt ons on my 97 4.0. I am thinking of adding a 99+ intake, a 62mm TB and 24lbs hour injectors. Has anyone done this? Is it worth the $300 it would take? What have you guys got the best results from?

When I built mine, I took a 98' 10kmi. 4.0l motor, added the larger intake, 24lb mustang injectors, 62mm with the spacer, aftermarket TJ airfilter re-locator (cooler side of engine), K&N big cone, MSD 6al with a blaster 2 coil, MSD fuel pump, header, 2 1/2" flowmaster.

I no-longer wanted a v8.

Still don't.



XJR:us: