2 5 Is VERY underpowered What more can I do? JeepForum com

17 Апр 2014 | Author: | Комментарии к записи 2 5 Is VERY underpowered What more can I do? JeepForum com отключены

This isn’t rocket science. You need Spark, Fuel and Air for combustion. With my 2.5L I did all of

the above and noticed a hugh difference. But that’s the key, you have to do them in conjunction

with each other. Doing one will only net small changes and you might notice a small gain but

you still have choke points in the complete system.

1) Open up your air intake by getting rid of your stock air box. There are two choke

points or restrictors in your stock air box. By doing so you will greatly increase the air

flow and temp of the air being mixed. This is where a cold air intake comes into play and

allow cooler, more dense air into your system.

2) Open up your throttle body and port your intake to match. If you just throw

your 4.0L (larger)TB on your intake, there is a restriction of the Intake being smaller. If you

look down through it, you will see the extra surface area that has to be ground down to

match the TB. A TB spacer doesn’t do much to the equation but I have found that it does have

a cooling effect with the helix design and therefor does increase the HP upgrade a bit.

3) Increase your fuel delivery to match your larger air flow This is where you upgrade

your stock 17lb fuel injectors to a better 4 pintle Bosch Type III EV1 19lb injector. This

allows more fuel to be mixed and atomized with the cooler, more dense and higher air flow

volume. Stock injectors have only one pintle or jet hole. Bosch type III EV1 19lb injectors

have 4 pintles or jet holes for a better spray pattern and mist. Depending on how you drive,

this equates to a more efficient burn for better gas mileage or a hotter burn for better

power and throttle response at the top end.

4) Hotter spark to burn the mixture. By upgrading your coil-wires and plugs, you allow your


system to burn off the better spray for more power. I used a super coil (Screamen

Deamon) coil, Live wires and Champion Plugs gaped to .080 for a much hotter burn.

5) Open up your exhaust for your new system to breath. Getting rid of the stock muffler

and cat and replacing them with high flow units allows your system to aspirate

(breath) much better and allows your system to move the exhausted gases out at a

quicker rate.

I also went to an 14 electric fan. By eliminating the belt powered fan, it reduces drag

on your little 2.5L 120Hp motor. Here are a few things to think about. Approximately

for every year old your motor is, you loose 1 hp due to age wear and tear. Stock your

new 2.5L motor is only 120Hp. My YJ is 19 years old. Theoretically, i’m around 101 HP.

small gains of 4-5 HP is noticeable on this size motor. Someone that has the 4.0L at 265Hp

probably won’t notice a 5 Hp gain. I have not tested my motor but I think I’m in the 143 Hp

Yesterday a 4.0L TB from a ’98 Cherokee arrived by UPS — to be installed on a 2000

2.5L TJ. With the help of a neighbor who teaches auto mechanics at the local high

school (absolutely cool woman who decided to make it a day project for some of her

students), I dyno-ed everything in stages. Checked the air flow, too.

Results, with stock (2.5L TB no spacer)as baseline:

(1) Poweraid spacer only — +2 HP, 8% less airflow (Evidently, the helix bore, lips

of which extends beyond intake TB opening, actually cuts down on airflow. But

the spacer does cool and extend air volume, hence horsepower increase.)

(2) 4.0L TB only — + 6 HP, 16% more airflow (no surprise here)

(3) 4.0L TB grind out intake opening to match lower TB opening — + 13 HP, 29% more

airflow (Wow! Grinding out the intake opening did make a difference!)

(4) 4.0L TB Poweraid helix spacer grinded-out intake opening — +16 HP, 2% less

airflow from #3 above(overlapping helix bore is still cutting off airflow, but spacer

is still cooling increasing air volume)

(5) 4.0L TB grind out helix bore in Poweraid spacer to match lower TB opening

grinded-out intake opening (the Big Kahuna) — + 24 HP, 39% more airflow (Wow

again; the optimal configuration, obviously)

It should be noted that grinding out the helix in the Poweraid spacer still leaves

a partial helix in the walls — the main difference being that the helix now has rounded

edges rather than sharp ones. My auto mechanics-teacher neighbor suggests that

these rounded edges are actually more aerodynamic than the original sharp ones,

and will still spin air — so perhaps the pulse-organizing effect I mentioned in an

earlier post will be retained, if in fact there is such an effect.

So, to reiterate, I ground out on the helix bore of the Poweraid spacer, and ground

out the intake opening, both to match the lower opening of the 4.0L TB I swapped

in. Dyno-ed tested airflow, results: +24 HP, 39% more airflow.

Seat-of-the-pants impression: idles smoothly, more torque on the low end, smoother

acceleration through the midrange, and better performance above 2700 RPM. No

hesitation, no engine codes.

One MAJOR suggestion: if you grind out your intake opening, be VERY CAREFUL

about aluminum filings in the intake manifold. We stuffed everything with tack cloth —

sticky cloths which can be purchased at a hardware store — rather than shop towels.

The tack cloth caught about 95% of the filings, but there was still a small mess

in the intake. We vacuumed a lot of the leftover out with a shopvac, but we still

had to use tack cloth attached to a long, thin screwdriver to mop out the runners.

On the TJ there are also four open plugs/hoses attaching to the intake below the

TB — you’ll have to clean those, too. It took longer to clean out the intake than

it did to bore out the opening, but it can and needs to be done.

Finally, should say that the TJ has a two-stage KN filter system, an MSD ignition

system coil, high-gapped Champion truck plugs, a Flowmaster delta-40 catback,

and a case-full of Mobil 1 synthetic oil. All or part of which may have a synergistic

effect on my results, since mods usually affect each other.

Cheers, GP

More Info: (1) The intake is soft aluminum, so we used a medium tungsten rasp,

followed by a fine fluted grinder bit, followed by a fine polisher. I’ll admit it’s not

even — hard to get consistency around the runner walls which are nearly flush

to the intake opening. The spacer is a harder grade of metal, and trickier, even

when clamped in a vise. Doesn’t look pretty anymore, at least on the inside.

(2) Tested at 1800 RPM and 2800 RPM with an average between the two — but

the results were fairly similar.

(3) We figured the following: At 2800 RPM, torque was up by about 16% with #5

option above. At 1800 RPM, torque was up by about 14%.

Again, folks, consider the mods and the synergistic effects — your numbers may

be different depending on what you have your rig, mileage, mechanical conditions,

altitude, etc. I give this just as a general indication.

Ambient air temperature: 74 degrees Humidity: about 35%

First, let me say hello to the group. I am a tech for Jeep and Chrysler, electrical

General Motors EV1

and drivability are my areas of expertise. Now I’m going to add my .02

1. I have done this mod on my own 92 wrangler with a 2.5L engine with incredible

results. The 2.5L has a KN stock replacement air filter w/ a stock air box. the

restrictor in the air box cover removed, a tri-y design header (manufacturer unknown,

was given to me), stock exhaust minus the cat, an Accel super coil (direct OEM

replacement) w/ Belden spiral core wires and factory plugs gapped at .035. I have

4.10 gears w/ 35×12.50 General MT’s and I can say this motor screams. The motor

in stock form would not pull the jeep w/ 33 tires. I did all the mods except the

throttle body and put the 35’s on. At 65 mph into a 15mph headwind, I would have

the throttle pushed to the floor just to maintain speed in 4th gear, with the throttle

body swap, it was like putting a 4.0L under the hood. Under the same conditions,

I could maintain speed w/ 1/4 to 1/3 throttle opening, and my DRB III confirmed

it. It felt like I added 15 to 20 hp. bottom end torque improved and overall drivability

improved. Fuel milage remained constant, or slightly better depending on how heavy

my foot was.

2. Now on to the AIS motor. If you look at the AIS motor and housings on th 2.5

and 4.0L engines, you will notice tha the idle air passage seat where the AIS needle

seats is considerbly smaller on the 2.5L than the 4.0L, so is the needle on the AIS

motor itself. You must transfer the AIS motor and housing from the 2.5L throttle

body to the 4.0L throttle body, if you don’t and you use the 4.0L housing and motor,

you may not get your idle speed down to where it should be. Your AIS motor will be

fully closed or close to it (0 to 2 steps). On TJ’s this can be a problem with the OBD

II, since it can trgger a code in the PCM (target idle not reached), so be sure to

transfer it to the 4.0L throttle body. Be careful with the gasket it is not available

separately. If done right and you have access to a DRB II or DRB III or a code scanner

your idle steps should be around 14 to 18 steps in neutral, air off, if not you can fine

tune to get it in that range by adjusting the throttle stop screw, if you turn it more

than a 1/2 turn in either direction, you better check your installation.

3. Yes you do have to trim the intake manifold opening, mine had a 1/8 lip around

the base and it does have a profound effect on air flow, enough to cancel the gains

of doing the conversion. I used a … grinder with a wide fluted aluminum bit, on the

vehicle wuth rags stuffed in the intake runners. A shop vac to remove the filings

was used and make sure all filings and rags are removed. I trimmed the hole to the

size of the gasket (4.0 and 2.5L gaskets are the same).

4. The PCM’s adaptive memory after 100 miles of driving was practically unchanged

after the swap meaning the PCM saw no ill effects from the swap. Keep in mind

that the MPI fuel injection is a speed/ density based system and does not see an

increase in airflow like other systems that use a mass air flow sensor, instead it

sees changes in MAP value and intake temperature (density in the intake manifold)

crankshaft speed and throttle position, coolant temperature in all modes plus the O2

sensor at idle and part throttle and then using complex alogrythims calculates the

injector pulse to provide the correct fuel/air raio. For all practical purposes you do

not need to worry about it, the computer seems to compensate for the swap with

no problems.

5. For those of you who still feel the need for more fuel, you can try injectors from

a 4.0L engine. These run approx. 10% richer, single cylinder displacement is about

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