ctjkelley

What's a good deal $$ wise on a 99' intake for my 98. What differences have you guys seen that are running one?

salad

http://www.fourwheeler.com/how-to/en...ing-true-lies/

ctjkelley

That's a pretty nice write up. I figured they would have mentioned the injector upgrade in there as well. Oh well thank you

Cherockee

Unfortunately that article isn't completely accurate. It was one (in-experienced) person's opinion on the intake swap that happened to get published in an article. Those that have done the swap (like I have) notice an improvement and not a loss in power. People who don't really know like to refer to the article like it's some kind of definitive proof that it doesn't work. What's more likely is that in the case of that article something else was done that masked the improvements that the intake made.
Just be sure to bore the TB and run a more free flowing exhaust and better injectors.

mr white

Could it be that the bored tb and exhaust and injectors helped more than the new mani?
I'd like to see dyno results of just the mani, all else the same.

Cherockee

I think it follows the logic that the manifold should be part of a system. There are probably many examples of performance parts that independently bolted on won't make as much difference as being paired with other components to produce the desired improvement. So I think it would not be wise to assume that the manifold alone will make an improvement, but need to be complimented with other performance parts.
Read Go-Jeeps article about his swap. http://jeep-xj.info/HowtoIntakeManifold1.htm

salad

That's a nice article, I hadn't seen that before. I'll have to refer to it in the future. A few notes though:

The original note about intake volume vs. velocity still rings true. Go-Jeep even mentions throttle body spacers, which are well known to be a worthless scam. These engines are not carbureted: Greater intake volume helps a ton when fuel has to be mixed between the throttle plate and intake valve but really has no meaning to MPFI.

Also the graph's data starts at 3k RPM, up to 5.4. Redline starts at 5k. It's a damn Jeep not a race car... if I'm doing anything to improve performance it'd better present itself between 1 and 3k RPM. Not to mention the dyno run was taken after additional modifications and STILL is not an actual representation of the manifold's performance.

Tom95YJ

Jeep would have never changed the manifold design if it did not benefit from it

PumpinIron

Agreed. Car manufactures don't generally change something in order to decrease performance.

salad

Of course not... just saying that how much of a benefit there really is with just a change in manifold, and not the entire system, is vague, and probably not significant outside of a butt-dyno.

Take for example the "High Output" change in engines. A lot of work done. But are you going to swap a Renix for Chrysler HO?

PumpinIron

I agree! The manifold by itself is probably not worth many gains but combined with an intake, throttle body, exhaust, and maybe even some headwork and a cam I would think there might be some gains from it.

ctjkelley

I already have the spectre air intake with a TBS, and after market exhaust, and it possible has a performance header on it as well from the PO not sure. I plan to install the manifold and a set of 703 injectors, I hope to see a difference in my low end, I agree it's not a race car, I wheel pretty regular so I'm all about more low end torque and response.

investinwaffles

Does a port + polish really do much? I guess that I would at least a polish anyway to clean the intake up, but wondering if taking any material off would increase any gains.

But now that I think about it, Chrysler/Jeep had like 20 years to figure out the intake efficiency so they might have already maximized the flow patterns with the updated manifold in '99

ctjkelley

I believe like stated earlier, you would see those changes after installing a cam and a different head, you can increase all the external performance parts all you want but until you do some things to the inside to boost that air flow it doesn't really matter how much air you send to it if the parts there can't handle it, it's only going to use the max air flow needed or it can handle. Hope that makes sense.

cruiser54

What we need to realize is that the benefits are almost always in the form of lower emissions for the manufacturer, not performance gains for the customer.

That manifold, along with smaller exhaust ports and other things they did over the years, was to meet increasingly tighter emission standards...........