Intake, Performance

[sublime600]

So im looking to get a little more HP, and some better MPG. So ive been looking at TB spacers and intakes, exhaust, etc. So my questions is what are the good ones. Ive been looking at the airaid TB Spacer. Ive been looking at the Airaid intake and the K & N intake, which is better. Also im pretty set on the Dynomax cat-back system. Any info on better products would be great. Also some sites that have what im looking for, for pretty good prices. Is there anything else i can do to get more? please no SC or turbos lol

 

[j99xj]

The best peformance products are the ones you make yourself.

They will save money for mods you can't make yourself (like exhaust headers, air filters, etc.)

 

[streetpirate]

dont use a spacer, get an intake manifold off of a '99 4.0, pacesetter header, the dynomax cat back, and make your own air intake. if you search in the street 'n performance forum, Dr. Dyno is a user who has had great success making his own performance parts on the cheap, and he has a website where he tells you how he did it.


SP

 

[gradon]

Get the '99+ intake manifold, a bored out TB, a header w/downpipe along with your dynomax catback and whichever intake you choose/make(I got a good deal on my FIPK)and your XJ will be breathing easier, more responsive, and will get higher MPG once you get tired of your awakened 4.0. Ditto on skipping the TB spacer.

 

[raypla]

Get the '99+ intake manifold, a bored out TB, a header w/downpipe along with your dynomax catback and whichever intake you choose/make(I got a good deal on my FIPK)and your XJ will be breathing easier, more responsive, and will get higher MPG once you get tired of your awakened 4.0. Ditto on skipping the TB spacer.

He already has the newer intake on his 01'. Definately nic the spacer and go for a free flowing intake w/ a bored TB. I'm not sure who makes headers for the 01', they have those funky precats in the header. Maybe you can look into eliminating all that junk and get a Borla w/the downpipe.

Here is a link for a TB http://www.thefastman.com/Throttlebodies40.asp real good price, guy to deal with.:yelclap:

 

[sublime600]

Thanks for the info guys. Ill def be knicking the TB spacer for the bored out TB. Sorrry that i didnt say what year i had earlier. But the Dynomax is probably the best exhaust over flowmaster right. I was always under the impression flowmaster was more for sound then performance. If anyone finds headers for an 01 please post a link thanks again!

 

[gradon]

I dished out $750 for the Borla setup (header w/downpipe and catback), and $50 for the magnaflow cat and I would definitely buy it again--great sound and good power, not to mention ss. My brother has the Borla header/flowmaster setup and his has a deeper and louder exhaust note On my old Jeep I had just the dynomax catback, which I was satisfied with

 

[XJoshua]

I still need to do a good intake, but I got a good exhaust on.

List from engine to tailpipe:
Renix 4.0
Banks Headers
Summit Racing Flex Pipe(2.5")
Custom S Pipe(Down Pipe)(2.5")
DynoMax High Flow Cat(2.5")
DynoMax Super Turbo Muffler(2.5")
Custom Muffler Back Pipe(2.5")

Total Cost(excluding motor): $210

I got the headers used, and got a discount on all the pipes which were madrel bent. So It sounds good, with the cat, without it, it sounds like poo poo when you hold a gear way to long, which you souldnt do.

 

[j99xj]

Why does it seem that everybody on this forum hates throttle body spacers?

I agree that you shouldn't buy a spacer with the swirls, but the smooth bore ones work for me especially because I got it dirt cheap on ebay. If you don't want an ebay account summit sells the smooth bore spacers too.

Anyway you slice it, a throttle body spacer is a worthwhile addition to your intake if you can find a cheap price. The common agreement around here is that its worth about 2-3 hp at the peak and about 4-5 lb-ft at the low end. I wouldn't pay a dime over 50 bucks for one. I got incredibly lucky when I found mine for 30 bucks, including shipping. And I'm sure its paid for itself in fuel savings by now.

 

[gradon]

My FIPK won't allow me to add a spacer and I installed the 99+ intake which added 1700cc's more air volume instead of the 76cc's you got with the spacer.

 

[Beej]

Why does it seem that everybody on this forum hates throttle body spacers?

I agree that you shouldn't buy a spacer with the swirls, but the smooth bore ones work for me especially because I got it dirt cheap on ebay. If you don't want an ebay account summit sells the smooth bore spacers too.

Anyway you slice it, a throttle body spacer is a worthwhile addition to your intake if you can find a cheap price. The common agreement around here is that its worth about 2-3 hp at the peak and about 4-5 lb-ft at the low end. I wouldn't pay a dime over 50 bucks for one. I got incredibly lucky when I found mine for 30 bucks, including shipping. And I'm sure its paid for itself in fuel savings by now.

People crap on them here because they don't add anything. I don't know where you got that common agreement idea from, but I'm sure its from a butt-dyno, not the real thing. It can't hurt to add one, but they just add plenum volume, something that is done much better by utilizing a later model intake...

 

[RichP]

You will get better MPG improvement by running your tires at the correct pressure. I run my BFG AT/KO's at around 40psi and that upped my MPG about 2mpg on my daily commute, every day, both ways. Going to take that safari rack off too, I know that cost me 2mpg at the speeds I drive on the turnpike, 70-80mph consistantly. If maintained correctly the 4.0L 97+ XJ is capable of 23-25mpg, that includes cleaning the fuel system on a regular basis when you get gas. I usually buy valvoline fuel system cleaner at Sams club by the case so it's no big deal to add it on a regular basis which I use my 3,000mi oil changes to base it on..

 

[j99xj]

You will get better MPG improvement by running your tires at the correct pressure. I run my BFG AT/KO's at around 40psi and that upped my MPG about 2mpg on my daily commute, every day, both ways. Going to take that safari rack off too, I know that cost me 2mpg at the speeds I drive on the turnpike, 70-80mph consistantly. If maintained correctly the 4.0L 97+ XJ is capable of 23-25mpg, that includes cleaning the fuel system on a regular basis when you get gas. I usually buy valvoline fuel system cleaner at Sams club by the case so it's no big deal to add it on a regular basis which I use my 3,000mi oil changes to base it on..

I got 24 mpg a few times with the cruise control on at 65.

 

[j99xj]

People crap on them here because they don't add anything. I don't know where you got that common agreement idea from, but I'm sure its from a butt-dyno, not the real thing. It can't hurt to add one, but they just add plenum volume, something that is done much better by utilizing a later model intake...

Dr Dyno did some testing with a stopwatch some time back and his best number was 5 lb-ft around the low end.

 

[old_man]

Dr Dyno did some testing with a stopwatch some time back and his best number was 5 lb-ft around the low end.

OK, what is the transfer function to get from time to lb/foot????

 

[j99xj]

OK, what is the transfer function to get from time to lb/foot????

You'll have to ask Dr. Dyno. But I'm sure it was simple kinetics. This is where I got my info from http://www.naxja.org/forum/showthread.php?t=65212&page=3&highlight=stopwatch+spacer

 

[indianaXJ]

hello:

You shoulld look into a pre 98 head to take advantage of your 99+ intake. Then you could use a header for a 97/98 model. Check out the Kolak exaust kit, it uses a factory mopar header and 70 series flomaster. The mopar header is sweet and the 70 series has a nice tone, not too loud but a nice rumble. The Kolak kit is high quality plus the kit was dino developed. This setup will probably not be EPA legal but with the bored TB and FIPK will give you the most gain for bolt on type mods.

I have not tried one yeat but as I understand it a TBS will help out in the lower rpm range with the 99+ intake . I would only try this as an experiment after the mods. above though.

 

[Dr. Dyno]

The TB spacer DOES produce a small HP/TQ gain across the rpm range (my estimate is 2-3lbft at higher rpm, 3-5lbft at lower rpm) and a small gain in fuel economy (nearly 1.0mpg) in '91-'99 models with the older log type intake manifold. The spacer adds an extra 1.0" in length to the intake tract and slightly lowers the peak HP/TQ rpm points (by ~100rpm). Since it's sandwiched between the TB and the manifold, it raises the TB away from the manifold floor and acts like a velocity stack (especially if it's smooth bored to a 62mm diameter). A thicker spacer than 1" would be even better but there isn't enough underhood clearance for one.

 

[MaXJohnson]

The TB spacer DOES produce a small HP/TQ gain across the rpm range (my estimate is 2-3lbft at higher rpm, 3-5lbft at lower rpm) and a small gain in fuel economy (nearly 1.0mpg) in '91-'99 models with the older log type intake manifold. The spacer adds an extra 1.0" in length to the intake tract and slightly lowers the peak HP/TQ rpm points (by ~100rpm). Since it's sandwiched between the TB and the manifold, it raises the TB away from the manifold floor and acts like a velocity stack (especially if it's smooth bored to a 62mm diameter). A thicker spacer than 1" would be even better but there isn't enough underhood clearance for one.

Three areas to improve fuel mileage: driving habits, reduced load, increase efficiency.

Since a spacer has no effect on driver habits or load, so we can assume your quoted gains are based on an increase in efficiency.

For the typical XJ, fuel consumption is around 14 to 20 mpg, so a 1.0 mpg improvement in fuel economy represents a 5 to 7 percent improvement in volumetric efficiency. Consider your claimed torque improvement and the percentage would be even higher.

The cost per vehicle to increase the plenum volume of the intake manifold by 72cc (1" spacer) would only amount to a few pennies. I find it hard to believe that the Jeep drive-train engineering group would miss such an inexpensive way to improve their competitive advantage. We know they weren't distracted by cup holder placement.

 

[j99xj]

Three areas to improve fuel mileage: driving habits, reduced load, increase efficiency.

Since a spacer has no effect on driver habits or load, so we can assume your quoted gains are based on an increase in efficiency.

For the typical XJ, fuel consumption is around 14 to 20 mpg, so a 1.0 mpg improvement in fuel economy represents a 5 to 7 percent improvement in volumetric efficiency. Consider your claimed torque improvement and the percentage would be even higher.

The cost per vehicle to increase the plenum volume of the intake manifold by 72cc (1" spacer) would only amount to a few pennies. I find it hard to believe that the Jeep drive-train engineering group would miss such an inexpensive way to improve their competitive advantage. We know they weren't distracted by cup holder placement.

I'm far from a marketer, but back in the day Jeep didn't need to have competitive advantage, because I think most of their buyers were previous Jeep owners that were completely satisfied with the product. Nowadays, Jeep is trying very hard to attract new buyers with the additon of the Compass etc. 4wd minivans. But in the process they are disintegrating and softening their base of Jeep loyalists who demand capability, not a posh ride .

The only vehicles worthy of having "Jeep" on the hood in the 2007 lineup are the Wrangler and Wrangler Unlimited.

I think the 4 door Wrangler Unlimited was the best idea Jeep has had for a long time. Why do I think this? Because it attracts former XJ owners, and it fills the gap that the XJ used to fill. (a capable 4 wheel drive, 4 door vehicle with an off road oriented suspension, ie solid axles) Make no mistake, NO VEHICLE will ever be able to replace the XJ but this new Wrangler Unlimited does attract "the XJ type" of buyer.

Sorry for my rambling, but I stand by the throttle body spacer. Whatever it does doesn't matter, its the fact that it works that matters. Dr Dyno says it gained 3 -5 lb-ft of torque on the low end. So let's say for instance that he had a 50% human error in calculating those numbers (which is highly unlikely in my opinion). So that brings the numbers down to 1.5 - 2.5 lb-ft of torque. Those gains in my opinion are still gains that are worth 30 bucks. I know its not a big gain, but its 1.5-2.5 lb-ft more than the other XJ revving its engine next to you at a red light....