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Info in 2.5 evolution and revisions


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this a nice doc i found about the changes of the 4.0 over the years

 

JEEP 4.0 PERFORMANCE TECH SPECS\


4.0 Engine Power Ratings
The Jeep 4.0 litre I6 engine is a pushrod overhead valve design with 2-valves/cylinder. The
factory power ratings are as follows:
'87...... XJ: 173hp at 4500rpm, 220lbft @ 2500rpm, redline 5000rpm
'88-'90 XJ: 177hp at 4500rpm, 224lbft at 2400rpm, redline 5000rpm
'91-'95 XJ: 190hp at 4750rpm, 225lbft at 3950rpm, redline 5250rpm
'96-'99 XJ: 190hp at 4600rpm, 225lbft at 3000rpm, redline 5300rpm
'00-'01 XJ: 193hp at 4600rpm, 231lbft at 3000rpm, redline 5300rpm
'91-'95 YJ: 180hp @ 4750rpm, 220lbft @ 3950rpm, redline 5250rpm
'96-'99 TJ: 181hp @ 4600rpm, 222lbft @ 2800rpm, redline 5300rpm
'00-'06 TJ: 190hp @ 4600rpm, 235lbft @ 3200rpm, redline 5300rpm
'93-'95 ZJ: 190hp @ 4750rpm, 225lbft @ 3950rpm, redline 5250rpm
'96-'98 ZJ: 185hp @ 4600rpm, 220lbft @ 2400rpm, redline 5300rpm
'99-'05WJ:195hp @ 4600rpm, 230lbft @ 3000rpm, redline 5300rpm

 

The '87-'90 engines had Renix electronic multipoint fuel injection, electronic ignition, a single
51mm (2.0") throttle body, and a rather inefficient low port cylinder head.
In 1991 engines received Chrysler sequential MPFI, a larger 60mm throttle body, revised
intake and exhaust manifolds, and a more efficient high port cylinder head. As a result, these
engines produced 13hp more than their predecessors and gained the "High Output"
designation. In 1996 engines received noise, vibration, and harshness fixes. The blocks were stiffened with
extra ribbing, a main bearing brace was added, and lighter cast aluminium pistons were
introduced to reduce cold start piston slap. Engines also received revised camshaft timing for
more low rev torque. In 2000 a distributorless coil-on-plug ignition system was installed, intake and exhaust
manifolds were revised, and a more efficient water pump was included.
Injectors

 

Some of those specs that are hard to find in any workshop manual.
The following is a list of the injectors used on the 4.0L since 1987 along with their rated static
flow:
Model Year, ...Part #, ...........Colour, .....Fuel Pressure, ...Static Flow,
'87-'90, ........53003956, .........Black, ...........39psi, .................18.6lb/hr
'91-'93, ........33007127, .........Brown, ..........39psi, .................21.0lb/hr
'94-'95, ........53030343, .........Tan, ...............39psi, .................21.0lb/hr
'96-'98, ........53030778, .........Grey, .............49psi, .................23.3lb/hr
'99-'04, ........04854181, .........Blue tip, ........49psi, .................22.5lb/hr
'05-'06, ........53013690AA, ...Brown tip, .....49psi?, ...............23.3lb/hr?


The injector flow rate varies as the square root of the pressure drop across the injector. The
stock '91-'95 4.0 injectors are rated at 22lb/hr @ 43psi fuel pressure, so at 39psi they flow
( sq. rt.(39/43) x 22.0 = 21.0 )


Cylinder head


The stock cylinder head is cast iron and weighs 60lb. The valve head diameter is 1.91"
intake/1.50" exhaust. Casting numbers are as follows:


Year............Casting No
1987-90......2686
1991-95......7120
1996-99......0630
2000-01......0331


Cylinder head flow figures (cfm) at 28inH2O pressure drop are:


Non-HO head #2686 (Courtesy of Greg Friedman)
Valve lift (in)..... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 122.0 168.0 186.0 189.0 192.0
Exhaust flow....88.0 114.0 130.0 134.0 138.0
Ported non-HO head #2686


Valve lift (in)..... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 124.0 183.0 197.0 207.0 216.0
Exhaust flow....87.0 113.0 138.0 153.0 159.0


HO head #7120 & #0630 (Courtesy of John Brown)
Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 66.0 128.0 179.0 206.0 209.0 209.0
Exhaust flow. 55.0 100.0 120.0 136.0 141.0 141.2


HO head #0331
Valve lift (in)..... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow..... 59.4 122.6 171.1 201.1 214.3 218.4
Exhaust flow...47.1 93.4 123.3 140.9 147.0 149.7


Ported big valve 2.02/1.60 HO head
Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5
Intake flow.... 73.9 142.4 197.8 229.8 247.0
Exhaust flow. 65.3 114.0 135.9 146.3 157.1


The early '87-'90 non-HO heads have low intake ports that flow rather poorly. The later HO
heads have higher intake ports that flow more air by allowing a straighter shot into the
cylinders. The '91-'95 HO heads with casting no.7120 have the highest intake and exhaust
port airflows, especially at lower valve lifts where it is most important, and are the best for
performance. The '96-'99 0630 heads are almost identical except that they don't have a port
for the coolant temp. gauge sending unit. The '00 and later HO heads with casting no.0331
have smaller exhaust ports to produce a faster warm-up of the catalytic converter and
improve emissions, but performance also suffers because the ports don't flow as well as
those of the 7120 and 0630 castings.


Intake manifold


The '91-'99 intake manifold is aluminium and has equal length 24cm (9.5") long runners. The
runners are rectangular with internal dimensions of 1.625" x 1.375" and a cross sectional area
of 2.234 sq. in. (14.4 sq. cm). The '00-'06 intake manifold has smaller diameter curved
runners with internal dimensions of 1.53" x 1.26" and a cross sectional area of 1.928 sq. in.
(12.4 sq. cm), and is clearly designed to produce more torque at lower rpm. The distance
from the intake valve to the port opening is 3.5" (9cm), making the total distance 13" (33cm)
from the manifold plenum wall to the intake valve.


For a given intake manifold design, the cross-sectional area of the runner and the runner
length affect the location of an engine's torque peak in the RPM band. According to the
Helmholtz tuning model and the formula shown here, the intake runner area and length are
tuned to resonate and produce an inertial supercharging effect at 5000rpm for the '91-'99
engine and 4650rpm for the '00-'06 engine. That's very close to peak horsepower rpm for all
High Output 4.0L engines.


Exhaust manifold


The same design principles for the intake manifold also apply to the exhaust manifold. The
cross-sectional area of the primary header pipe affects the location of an engine's torque peak
in the RPM band. The pipe length generally will not change the peak torque or the RPM at
which it occurs. A length change has the effect of improving the torque on only one side of the
peak by "borrowing" it from the other side. A shorter pipe improves torque after the peak
(reduces it at lower RPM), preventing the torque curve from falling off so quickly as speed
increases. A longer pipe extends the torque curve backwards to improve the engine's
flexibility, at the expense of after-peak torque.


The stock exhaust manifold and the Borla header have a primary pipe internal diameter of
1.375" and a cross sectional area of 1.49 sq. in. Using this formula:


Peak Torque RPM = [Primary Pipe Area (sq. in) X 88200] / Cylinder Volume (cu. in.)
the stock exhaust manifold and the Borla header are tuned to a peak torque of 3265rpm.
That's right at the peak torque rpm of the 4.0 engine.


Block Casting Numbers
Year............Casting No. ...........................Part No.
1987...........53005535 (8933002665)....83503400
1988-90.....53005535 (8933002665)....83505110
1991...........53008405..............................4626155
1992...........53008405..............................4638959
1993...........53008405..............................4728988
1994-95......53008405.............................4778882
1996-99......53020569.............................4883025
2000-01......53010449AA.......................5013166AB

 

i wonder if the 2.5 had  asimilar evoultion and if so, where`s the data?

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1984-85 ... XJ: 105 hp at 5,000 RPM, 132 ft-lb at 2800 RPM

1986 ......  XJ/MJ: 117 hp at 5,000 RPM, 135 ft-lb at 3,500 RPM

1987-90 ... XJ/MJ: 121 HP at 5,250 RPM, 141 ft-lb at 3,250 RPM

1991-2000 XJ/MJ: 130 hp at 5,250 RPM, 150 ft-lb at 3,250 RPM.

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www.4bangerjp.com will have more info, though its a little difficult to become a member there, have to go through forum owners facebook page and message him there for access. As far as I know, there werent near as many updates to the 2.5 as there were for the 4.0. Youll see crank snout length differences depending upon the drive system used, and obviously the differences between the carbed version, the renix versions, and the Chrysler version of engine management. 

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