4.0 Myth Busting

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Oct 23, 2014 | 12:51 PM

#31

SteveMongr

Beach Bum

Joined: Jul 2011

Posts: 6,123

Likes: 22

From: Cape Hatteras, North Carolina

Year: 2000 WJ

Model: Grand Cherokee

Engine: 4.0

I did the mythical 99+ manifold swap on my 96. 'Seemed' to pull a bit more when passing on highway, in the 3,000 RPM range. That was the only difference I noticed, and it was subtle.
Injectors (Chrysler #402) I did 6 months prior made a difference that was unmistakable.

Oct 23, 2014 | 06:10 PM

#32

Big David

CF Veteran

Joined: Jun 2011

Posts: 2,720

Likes: 44

From: Gainesville GA

Year: 1999

Model: Cherokee (XJ)

Engine: 4.0

I did the '99 up intake swap along with 703s & a Ebay header on my '98 almost 2 years ago. I owned the XJ more than 4 years prior to the swap. I saw a huge difference when starting off at a red light.

I don't care what anyone says, I would do this to any Jeep the intake would fit on.
I want to put one on my Renix. I've searched with no luck. Anyone have a link?

Oct 23, 2014 | 06:17 PM

#33

torque062

Seasoned Member

Joined: Apr 2011

Posts: 420

Likes: 1

From: Yuma

Year: 1993

Model: Cherokee

Engine: 4.0, APN header & 2.5" exhaust

http://mallcrawlin.com/forum/showthr...L-DYNO-NUMBERS!

Oct 23, 2014 | 06:29 PM

#34

BNJeepsta

Thread Starter

CF Veteran

Joined: Jul 2011

Posts: 2,164

Likes: 1

From: Warren, Pa

Year: 97

Model: Cherokee

Engine: 4.0L

Quote:

Originally Posted by torque062

http://mallcrawlin.com/forum/showthr...L-DYNO-NUMBERS!

Good read but, that 4.0 has been ported and polished and even has LS1 valves. Which, as we were discussing before, would definitely benefit from the newer manifold. On another note, how ****ing lame was that dyno??? All those mods and it made less hp and tq than a Ford Focus! They sure don't seem to be that low on power when driving

Oct 23, 2014 | 10:55 PM

#35

torque062

Seasoned Member

Joined: Apr 2011

Posts: 420

Likes: 1

From: Yuma

Year: 1993

Model: Cherokee

Engine: 4.0, APN header & 2.5" exhaust

Yeah Cherokees don't put much power to the ground. I also don't think the ls1 valves are worth bragging about unless the engine bore had been increased to help deshroud the valves. They are oversized for the bore imo. A better mod would have been porting the bowls and shaping the valve guides in the chamber. But, at least somebody has dyno proof of ACTUAL gains.

Oct 23, 2014 | 11:11 PM

#36

Outlaw Star

CF ADMIN

Joined: Sep 2010

Posts: 34,088

Likes: 257

From: Lantana, Fl

Year: 1996

Model: Cherokee (XJ)

Engine: 4.Slow

Quote:

Originally Posted by BNJeepsta

If you already had good, stock injectors, you won't really notice a difference. Injectors make very little difference to stock gasoline engines. Diesels on the other hand, are a totally different story. You have to look at it this way, the computer, only calls for the amount of fuel it needs so unless you up the required amount of fuel needed, the stock injectors are perfect. The different nozzle/spray pattern MIGHT help burn fuel better but, the difference will be marginal at best. If the neon injectors were really that good, mopar would have used them in the first place

The term you're looking for and trying to describe is called Duty Cycle. It's the amount of time your injector nozzle is held open. So without changing/altering the ECU programming or other sensors, larger injectors will do nothing. IE: if you have 19lb hr injectors and switch to 24lb hr injectors, the amount of fuel delivery will stay the same unless you hold the injector open longer. The flow rating is what it is capable of flowing if held open constantly.

Oct 24, 2014 | 06:45 AM

#37

CobraMarty

CF Veteran

Joined: Dec 2011

Posts: 1,777

Likes: 22

From: PA KOTUFU!

Year: 1998

Engine: 4.0L 162,000

Here is a collection of DYNO runs
http://jeepm62superchargerkit.blogsp...g-page_15.html

Oct 24, 2014 | 06:50 AM

#38

CobraMarty

CF Veteran

Joined: Dec 2011

Posts: 1,777

Likes: 22

From: PA KOTUFU!

Year: 1998

Engine: 4.0L 162,000

All the 'bolt ons' together will add about 15rwhp and 15rwtq total.

JP Mag showed that the 'TB spacer' which was included in 2 different CAI kits were the top performers and the spacer was worth about 2-3rwhp.

A supercharger will add 60rwhp and 70rwtq to a stock 4.0L and the 'bolt ons' are additive on top of that.

No Butt Dyno here.