No. H.o. Only

 

91 to 98 only.

 

I understand this thread was revisited regarding a '87 Renix but FWIW, here's a quote from JPMagazine's "Myth Busting" article regarding the intake swap on a '98 XJ and the dyno results were disappointing....

'99-Up Horseshoe Intake
Myth: According to that great wealth of information that is never wrong, the Internet says you'll get a 5-30hp gain thanks to the '99-up 4.0L's swooped, equal length runners and larger plenum volume.
Our Thoughts: While a free-flow intake manifold can deliver more power, it's only going to allow as much air to flow as the cylinder head and camshaft will call for. Upping the intake runner volume too much will cause the intake charge to lose velocity, killing low- and mid-speed power and torque. On a '98-earlier engine running a stock camshaft and unported cylinder head, it's wasted effort.
Claimed Gains: 5-30hp
Actual Gains: 5hp loss on Trasborg's '98 XJ (Project Mileage Master)

 

I did the intake swap by itself. 1996 XJ. Already had the 2.5" exhaust and upgraded injectors #403.
The Only difference I could tell was around the 3000 RPM range when passing on highway. 'Seemed' to have a little more pulling power.
MPG I cannot test because driving the beach just once ruins the numbers.
The injector upgrade had much better results than the intake.

 

I did the swap on my 95 ZJ and noticed the engine keeps pulling longer in the RPM range. Before it would fall off at around 4000 RPM. I also swapped the injectors with 703s and changed the location of the air intake temp sensor to the air box. The main thing about all of the stuff I changed was I did NOT LOSE any horsepower...as far as my butt dyno can tell anyway.

 

.......and butt dynos are the gospel. Just kidding.

 

Probably the result of more fuel from new injectors and the IAT reporting cooler than anything to do with a manifold.

 

Maybe, but I'm happy with the results. I only had about 75 bucks into the manifold swap, the other mods were almost free.

 

Manifold necessitates larger injectors to match the airflow.

It generates more power. Period. Jeep magazine frankly has some of the most misguided employees in the field.

 

Guess they use a misguided dyno when posting results.

 

While I agree that JP Magazine has their issues I don't see where this "more airflow" comes from... The head has not been ported. You let in the same amount of air through the throttle body. The old manifold is rated for a fair bit more air than the engine sucks down in the first place. Even with a more efficient (less turbulent) manifold, any theoretical change in flow is no challenge for the PCM through its normal MAP and O2 sensors. This isn't a supercharger lol.

The only even reasonably close to scientific result I've seen around this was a lad with a ZJ. Unortunately he replaced injectors too, but they were with refurb stock injectors. On dyno tests he saw about a 5 HP gain around 4500 RPM. This was in a post either here or on one of the other reliable forums.

Now you talk to anyone who works with chassis dynos and they'll roll their eyes at 5HP. So many things can cause that, plus it is within the margin of error. Assuming it's real, though, it is a very poor investment for a Jeep owner. I think I've gotten my engine to 4000 RPM twice before... (Not as useless as a throttle body spacer, however)

Seems like a good mod to do if you're tired of loosening the power steering pump to adjust the belt. Lol

 

The change in the belt tensioning setup is worth the swap in my opinion. That is if you get the needed parts cheap enough. I paid 23 bucks for the manifold, 19 for the pump and brackets, I got the injectors at a cargo shorts pocket discount, got a new belt and intake gasket at O'Reilly Auto Parts for a jobber rate.

 

More airflow comes from smoother flowing runners in the intake manifold. It doesn't have blocky corners to create turbulence.

And it holds twice as much volume of air.

When air can flow smoother, it will enter at a higher volume. The size of the manifold also helps play into expansion and contraction due to heat.

 

When swapping in the 99+ intake, what belt do you use? Is it all the same belt, just a different routing?

 

I always laugh when I see this article mentioned online. The arrogance of the guys at this JPMagazine is astounding. So these couple of guys who work for this second rate "magazine" know more about automotive dynamics than the engineers at Daimler AG? The intake manifold was redesigned by some of the best engineers in the automotive industry in 1999 to help restore some of the power lost by the recent emissions control requirements. Anyone who knows anything about street rods or drag racing knows one of the first things you do when you want to get more HP out of an engine is go to a larger better flowing intake manifold. Or maybe the engineers at Edelbrock need some lessons from the JPMagazine guys too.