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Does anyone know how Jeep squeezed the 9 extra ponies out of the 99+ 4.0L?


MossGreen98!

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Does anyone know how Jeep squeezed the 9 extra ponies out of the 99+ 4.0L?

I know the intake changed after 98’ and they repositioned some of the belt driven accessories, but I wouldn’t see that alone getting another 9hp.
 

Skylinessuck

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Head casting, intake, tune. Nothing really to worry about. If your are looking to improve it with your rebuild, stroke it it just leave it alone.
 

Chris

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A slightly more optimistic dyno on a different day with better variables.

That has something to do with it, I guarantee it.
 

bromel

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Not sure why the Wrangler lagged behind, but my 95 Cherokee is also rated at 190 HP.
 

Jerry Bransford

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A slightly more optimistic dyno on a different day with better variables.

That has something to do with it, I guarantee it.
Exactly, most dynos are too erratic to get an exact HP reading. There are so many variables going on and any of them can cause a significant difference.
 
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Jerry Bransford

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There used to be ads on late night TV for the Tornado air intake that "swirls the air fuel mixture for more power and better fuel economy!" They even had a vehicle hooked up to a dynamometer showing simultaneously the before and after HP on a big dial that was easily read. Yes the engine with the Tornado installed did show more HP. But if you looked carefully to another gauge behind the HP gauge, you could see the tachometer. Yes the engine rpms were higher in the higher HP example. They weren't very careful in that ad but I figure they figured nobody would notice the difference in the tach readings.
 
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Mike_H

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A slightly more optimistic dyno on a different day with better variables.

That has something to do with it, I guarantee it.
You're assuming they only tested one engine, once. I can assure you they tested way more than once and way more than one block. That number is probably the average power output over all those tests.

There have been court cases about power output of engines and automakers being optimistic. Now, I gaurentee there is a bunch of data to support the claim. This isn't some shady, fly by night aftermarket company... It was Chrysler, with billions in resources.
 

AndyG

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There used to be ads on late night TV for the Tornado air intake that "swirls the air fuel mixture for more power and better fuel economy!" They even had a vehicle hooked up to a dynamometer showing simultaneously the before and after HP on a big dial that was easily read. Yes the engine with the Tornado installed did show more HP. But if you looked carefully to another gauge behind the HP gauge, you could see the tachometer. Yes the engine rpms were higher in the higher HP example. They weren't very careful in that ad but I figure they figured nobody would notice the difference in the tach readings.
Reminds me , in the dirt bike world, less intake turbulence has been discovered ...wings are inserted into the carb. But, fuel injection has taken over , even my 300cc 2 stroke woods bike is direct injected. Crazy.
 
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CharlesHS

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There used to be ads on late night TV for the Tornado air intake that "swirls the air fuel mixture for more power and better fuel economy!" They even had a vehicle hooked up to a dynamometer showing simultaneously the before and after HP on a big dial that was easily read. Yes the engine with the Tornado installed did show more HP. But if you looked carefully to another gauge behind the HP gauge, you could see the tachometer. Yes the engine rpms were higher in the higher HP example. They weren't very careful in that ad but I figure they figured nobody would notice the difference in the tach readings.
Many years ago when the Tornado was first produced (around 1999); I tried one in my '98 XJ 4.0L.
I reset the ECM and let the vehicle relearn...
My MPG went down by 4-5 mpg, there was a dramatic drop in performance and I discovered that the stainless swirl mechanism obstructed the air flow going into the throttle body.
I contacted the Performance shop in Forest Hills and talked to the manager; he informed me that the majority of the people who bought this item returned the item with in a couple weeks complaining about similar problems. He was gathering the returned items and was in the process of returning them to the original manufacturer.
I didn't realize that this product is still in production....
 

Brianj5600

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In some cases but let's not overgeneralize a tune's ability. We're not going to gain 20 hp from our 4.0, for example, by a just tune.
My bad it is not 20 hp.

From Flyin Ryan performance

" We pick up approximately 15 whp and 22-25 wtq across the curve on 87 octane"

1593409638242.png


My Jeep had a best 0-60 of 14.15 with stock tune and 12.75 with only changing the timing table. This was on the same day, back to back. Tuning software is probably my favorite mod I have done. There are several members that have seen real performance gains from both DIY
tunes and from FRP.
 
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MossGreen98!

MossGreen98!

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Well I think all that confirms no need to waste time and $ on the newer style intake. Was a pain getting it back on the first time when I replaced the headers
 

CharlesHS

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Around 2001 there were several 4.0L XJ owners on NAXJA that were testing the swap of the new style intake manifold. Some reported performance increases, but when their Jeep was tested on an actual dyno; there was about a 2 HP difference. In those years there were no tuners available for the 4.0L; only the performance modules with preprogrammed parameters. The only times the newer style intake manifold really showed an increase in performance was when it was used on a stroker engine.
Russ Pottenger owner of Bishop-Buehl Racing engines is the guru of Jeep stroker engines; he knows about performance increases on the 4.0L.
 

MyotherrideisaJEEP

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There used to be ads on late night TV for the Tornado air intake that "swirls the air fuel mixture for more power and better fuel economy!" They even had a vehicle hooked up to a dynamometer showing simultaneously the before and after HP on a big dial that was easily read. Yes the engine with the Tornado installed did show more HP. But if you looked carefully to another gauge behind the HP gauge, you could see the tachometer. Yes the engine rpms were higher in the higher HP example. They weren't very careful in that ad but I figure they figured nobody would notice the difference in the tach readings.
 

Brianj5600

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One of the reasons I laugh when people claim they gained 5 HP with an air intake install.

Yeah... in your head you did 🤣
Have you tried modifying your timing tables? It really is a noticeable difference. The extra torque really helps with the 42rle. I don't remember the last time I turned of my OD, and there is no flat land where I live.
 

Chris

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Have you tried modifying your timing tables? It really is a noticeable difference. The extra torque really helps with the 42rle. I don't remember the last time I turned of my OD, and there is no flat land where I live.
Fortunately my new TJ is a NSG370, which I am enjoying much more than the 42RLE. However, that's interesting about the timing tables. I assume you get to a certain point in modifying them where it makes it run worse though, no?