bigger cams for a jeep liberty

[Bashgod]

If you actually manage 400 horsepower out of the engine your transmission is good as dead. That is assuming the transfer case doesn't grenade before the transmissino has a chance to.

And what is this "stage II" chip you are talking about? If you have a turbo setup with some custom ground cams you're gunna need to put the car on a dyno and get someone to custom tune the ECU with wideband O2 sensors - otherwise your A/F ratio will be *completely* out of wack - and you'll be lucky if the thing even starts/runs to begin with on 12 pounds of boost. You'll likely start/run on 5 lbs...but your A/F will be *way* out still and you'll end up with everything from bad O2 sensors (if you're lucky that's all) to holes in your cylinder walls and pistons.

the chip is just something to use before I really start adding horse power.

 

[turbodave]

Well, I'm suprised that a piston in a relativly modern engine made using relativly modern techniques is that close to the edge from the factory. If a company managed to break one at that low of a boost it's surprising it isn't occuring on some nat-asp motors aswell.

 

[Bashgod]

my friend insists i can run 5 psi with the stock pistons but im too afraid to lol. the hardest part is going to be getting forged pistons. this whole setup should cost no more than $1500.

 

[tjkj2002]

my friend insists i can run 5 psi with the stock pistons but im too afraid to lol. the hardest part is going to be getting forged pistons. this whole setup should cost no more than $1500.

Heck forged pistons will cost you at least $600-$800(if not more),PCM tune is about $400+,Higher flow fuel pump and injectors at least $600,The turbo set-up and fabricating/labor for all of this will be $$$ to,and the all the little things add up fast(hoses,extra piping,plugs,and so-on).Can't see doing it for much less then $3000 if you do almost all of the work yourself.Then you got to upgrade the drivetrain to and that's $$$$ also.

 

[Bashgod]

I meant for the initial setup. I'll run 1-2 psi just to make sure everything works, and then when I can get the pistons I'll really know where I stand. just about everything except for the tuning will be done by us. Again, I'm not worried about the drivetrain.

 

[Ry' N Jen]

Just ad a 100hp shot of Nitrous Oxide.
Add a system that you can dial in just how much go fast juice you want!

 

[indieaz]

my friend insists i can run 5 psi with the stock pistons but im too afraid to lol. the hardest part is going to be getting forged pistons. this whole setup should cost no more than $1500.

What qualifies your friend to make this statement - has he run a few 3.7L KJs on 5 lbs of boost for extended periods of time? Or is he just making assumptions?

 

[tjkj2002]

What qualifies your friend to make this statement - has he run a few 3.7L KJs on 5 lbs of boost for extended periods of time? Or is he just making assumptions?

I would have to agree with you,unless he has boosted alot of 3.7's then he does not know what the engine can or can't handle in stock form.


Oh and 1-2psi of boost will severly hurt you not help,the incoming aircharge will be so super heated at that low psi you will loose power,a min of 4 psi of boost is required to make power,anything under is hurting you.

 

[turbodave]

I don't agree ^^^ Only time this could possibly be true is if the turbo was running in such a low efficiency part of the map where everything was working against it - I can't think how this could even begin to happen dynamically though? It certainly wouldn't be 'superheated'... Air gets hotter the more it is compressed. Different compressors will heat air differently depending on flow and pressure ratio, along with turbine speed, but rest assured the air temp at 1-2psi is barely over atmospheric. Basic thermodynamic calcs will always prove this.

I have set engines up with the (internal) wastegates jammed open before now to establish a baseline map for off-boost conditions and will be doing this soon to set up injection timing characteristics for a siamesed port engine (that requires an injection map wrt RPM aswell as the regular duration requirements); In these 'open wastegate' tests, the engine always makes a little boost as the airflow through the wastegate peaks, and hence starts spinning the turbine.
I've never experienced a loss of power as boost comes in. Even low 'boost' measured in the intake is raising the efficiency of the motor over that of nat-asp... If the fuel and ignition is right, it'll make use of this increased airflow.

I don't mean to pi55 on anyones fire here, especially as a relativly new member of this great forum. I am surprised - but probably more sceptical - of claims that 5psi will wreck pistons in the 3.7... Under fuelling - and extreme over fuelling will kill pistons, aswell as incorrect ignition advance. High revs will usually kill pistons before a little boost done properly, hence my earlier question about any reported failures (or lack of?) in the stock 3.7...

 

[tjkj2002]

I don't agree ^^^ Only time this could possibly be true is if the turbo was running in such a low efficiency part of the map where everything was working against it - I can't think how this could even begin to happen dynamically though? It certainly wouldn't be 'superheated'... Air gets hotter the more it is compressed. Different compressors will heat air differently depending on flow and pressure ratio, along with turbine speed, but rest assured the air temp at 1-2psi is barely over atmospheric. Basic thermodynamic calcs will always prove this.

I have set engines up with the (internal) wastegates jammed open before now to establish a baseline map for off-boost conditions and will be doing this soon to set up injection timing characteristics for a siamesed port engine (that requires an injection map wrt RPM aswell as the regular duration requirements); These always make a little boost as the airflow through the wastegate peaks, and hence starts spinning the turbine.
I've never experienced a loss of power as boost comes in. Even low 'boost' measured in the intake is raising the efficiency of the motor over that of nat-asp... If the fuel and ignition is right, it'll make use of this increased airflow.

I don't mean to pi55 on anyones fire here, especially as a relativly new member of this great forum. I am surprised - but probably more sceptical - of claims that 5psi will wreck pistons in the 3.7... Under fuelling - and extreme over fuelling will kill pistons, aswell as incorrect ignition advance. High revs will usually kill pistons before a little boost done properly, hence my statement about reported failures (or lack of?) in the stock 3.7...

But that would only hold true when the turbo is next to the engine,remember he wants to put the turbo in the rear of the KJ,longer disteance+ low boost= more heat.Plus at low boost you are just senting just above normal atmosphiric pressure through a hot turbine which=heat.Call KenniBelle,there the one's that toasted the 3.7 and scraped the supercharger kit,kinda notice that no one makes a kit for the 3.7(Vortech,Paxton,or KenneBelle),even more so now that's it been put in alot of other platforms.Granted you are right about the over fueling and spark timing which all needs to be change for a boosted engine,stock timing and fuel delevery just won't do in a boosted engine.For that fact the stock fuel pump and injectores are rarely up to the task to.Just tuning a one-off kit for something like a KJ will cost some big$$$$ just in the PCM tuning and dyno time alone to make it work.The other kits availeable for other models already have had the R&D time into them and come with all you need,that's why most kits start out at $5000+.

 

[Bashgod]

1. a supercharger is much harsher on an engine due to its immediate power supply, A turbo must spool up before it delivers power so it is not as harsh.

2. 1-2 psi would be helping out the intake of air, so at such little boost you would be basically counter the engine having to suck in its own air.

3. the turbo being mounted back as far as it is wont send super heated air to the engine. this may go against the many years and exhaustive engine and turbo studies you have done but i'll risk it.

my friend could probably tear apart an engine and put it back together before you're done reading how to do it. his credibility is the least of my worries and should be none of yours. At this point you wont discourage me, so encouraging ideas would be most useful... I would have thought people would be interested in seeing a turbo mounted in a liberty, I may be a guinea pig but i have a genuine interest and the will to do it.

 

[Atrus]

Bash, I think it's going to be a very difficult project, but I am definitely interested in seeing what happens. Please keep detailed logs and pics and whatnot, and update us frequently.

 

[Marlon_JB2]

Yes, please do keep us updated. I haven't read through the whole thread, but there ARE issues with the Piston Rings on the 3.7L and 4.7L engines. The rings are mounted too high for emissions purposes and because of that, they simply blow.

If someone has said this already, disregard.

 

[Bashgod]

Yes, please do keep us updated. I haven't read through the whole thread, but there ARE issues with the Piston Rings on the 3.7L and 4.7L engines. The rings are mounted too high for emissions purposes and because of that, they simply blow.

If someone has said this already, disregard.

Lol, it may have been brought up once or twice. I'll try to keep a video log of the process.

 

[turbodave]

Crack on and do it. If you need any assistance on compressors or other turbo assistance - or just someone to bounce Ideas off - I'll happilly chip in

TD

 

[Bashgod]

Thanks TD, I will.

 

[04Liberty]

I'd drop a 4.7 in that bitch first, same engine plus 2 cyl. The hemi does fit (they shoved one into a Nitro) but would require a helluva lot more work. A 4.7 HO would shine in these vehicles!

 

[AJK381]

i just got done turboing a v6 mustang, its like people have said its not a big v8 power thing its just to say yea its a turbo v6. and really who turbos a kj? ive been pondering on it for a while, as well as on my brothers zj. turbos are alot of fun and have many benifits not just power. they increase the efficiency of your motor, ie using used exhaust gases to pressureize the incoming air thus making it not have to work so hard. everyone is talking like its a crime to want to do it, no matter what it is kj or not its still going to take work and things will need to be upgraded. and as for chips for the 300 you spend you can find someone that knows how to use hp tuners or such and have them custom tune it to your liking, then if you change something all they have to do is plug in and you gain more from it.

 

[Bashgod]

***** how life gets in the way of things but i still want to do this. i just to be in a better financial position first, lol.

 

[KYLiberty]

Wow, this is an old thread brought back to life from before I was a member over here. If you are really serious about getting big power out of the 3.7, I can give you some advice from actual experience, and get you in contact with the right people. You are going to need a hefty budget though.