bankspower...or not?

[mudslinginjoel]

So I'm torn on getting the banks stainless exhast or not,from the header to the tail pipe,possible thier air intake.Its said to give increased air flow,and less backpressure.....

Now I've always been told your engine needs some back pressure for your vavles to work properly,ya da ya da,my question is do you guys think this exhaust could cause problems in the future?I,d like the extra power,and sound to,but I don't want to have problems in the trail ethier.

Good swap,or not?-thanks.

[mudslinginjoel]

heres the link

http://jp.bankspower.com/


forgot to mention, I've got the 4.0L

[Gearhead]

I've got that system on one of my YJ's . It's very well made , fits perfectly , sounds great and will never rust .  A little spendy but in my opinion , quality is worth paying for , as well as only having to only do it once . I've had it with cheap exhaust systems that don't last. The Banks system doesn't come with a catalytic convertor so either get that seperately or , a high flow stainless cat is easy to find , I  use a piece of stainless tubing where the cat would normally be .

[BlackYJ]

I went to the local minute muffler and for $250 I had a 2.5" high flow mandrel bent exhaust system from the downtube back, including a dynamax super tubro muffler, with a LIFETIME warranty.  That was 7 years ago.  This past winter my muffler inlet nozzle had cracked, cost me $60 for labour and I got a new muffler.  In my personal opinion, all these expensive muffler kits are not worth it.

You basically have to do an upgraded exhaust if you upgrade the intake or you will not see any benefit.  As for backpressure, yes you engine needs some, and it is very nice to have offroad, but if you gearing is good, then you do not need to rely on backpressure.

It is your call.  On a side note, 2.5" exhaust was too big for the 4 banger, 2.25" would have been better

[Elsifer]

I'm no mechanic, but if the backpressure isn't enough with the new exhaust system, especially for low gear hill descents; do what the diesel guys do, add an exhaust brake. It'll create the backpressure on demand for when you need it, and allow for ear splitting roar when you don't.
Perhaps a true tech can confirm this, if an exhaust brake will work well in a fairly free flowing gas application.

As for spending the bucks for a big name kit, I'm kinda torn too. I like the fact that a local shop can do the work, and warrantee it; but then again, there is the satisfaction of buying something proven and backed up with some solid numbers in terms of performance.

Six one way, and half dozen the other.

[cLAY]

Backpressure is needed for proper scavenging of the cylinders on valve overlap(ie engine performance), has nothing to do with hill descents.

I typically bash my exhaust about once a year really good and find that every two years it needs serious attention. I usually have a complete stock exhaust system kicking around from XJs I've pated out to steal from.

Moral of the story, don't spend a ton of money on shiney things to mount undereneath your Jeep, you're gonna bash it eventually.

[Spinalguy]

On the Rubiconownersforum, there have been many a thread on exhaust and intake upgrades. From all the tech with actual realtime numbers not supplied by the manufacturer, the jury is in unanimous agreement that there is a PERCEIVED performance gain but there is no ACTUAL performance gain. Banks, Intakes, etc do very little if anything to give you performance gains!

i agree with Clay in doing it like he did.

TK

[mudslinginjoel]

Hey guys,I thank you all for your imput,but the biggest worry of mine is if this kind of up grade would some how shorten the life span of my engine, or cause other problems.Even if I did go with lets say,dynomax....or flowmaster....would there be any problems in the future?I plan on running (and I guess fixing)my jeep for a long time.Thanks.

[BlackYJ]

Hey guys,I thank you all for your imput,but the biggest worry of mine is if this kind of up grade would some how shorten the life span of my engine, or cause other problems.Even if I did go with lets say,dynomax....or flowmaster....would there be any problems in the future?I plan on running (and I guess fixing)my jeep for a long time.Thanks.

By freeing up the exhaust and/or intake you will not hurt anything, especially with the exhaust as you are actually improving the efficiency of the engine.  However, with improved efficiency comes more power which if used right will increase MPG, but in most cases it causes a decrease in MPG.

Joel, when I put my high flow exhaust on my 4 banger it DEFINITELY woke up that engine and the squirrels were now Angry Squirrels.  I gained a fair bit of power (for a 4 banger) and I increased my gas mileage by 2-4 mpg, these are real world numbers.

Now I disagree with Clays comment about backpressure and hills, because if you don't have the gearing for hills then you typically rely on backpressure, once I had done my exhaust, I was more prone to speed up going down steep hills as I did not have the backpressure to hold it.

[mudslinginjoel]

Thanks for the help "black yj",the more I think of it,I'm thinking of a mandrel bent exhast,it's cheaper,does about the same,and easier to replace(cheaper)if I/when I wreck it.Do you think 2.5 inch would be good for a 4.oL?

[BlackYJ]

My dad had a 2.5" on his XJ and I have 2.5" on my YJ right now and it works great.  I recommend Minute Muffler for the lifetime warranty.  Also take the cat out and put in a resonator.

[Spinalguy]

Scott,
i removed the cat from my 4 banger (now its back) and it woke the engine up but as many thread has stated it was a PERCEIVED wake up in power. MPG were better but actual power gains? Did you dyno it to prove the gain? Many have and there is no actual gain.
TK

[Bnine]

The reason for that Tom is the cylinder heads, and differences in the years.

Due to emissions, jeep changed the configuration of cylinder head ports on the 4.0 in 1999 for sure, and maybe the 2.5, I don’t know. The newer heads are significantly more restrictive then the pre 99’s.

That is why exhaust mods are not making a difference on these newer jeeps. You are trying to increase flow by changing components that are past the main restriction. Essentially a wasted effort.

Next time you come by, you should take our xj for a ride just for poops and giggles to see what pre 99 4 litre feels like. Over 300,000kms and it will leave our rubi’s in the dust.

The difference you and Scott noted on your pre 99 2.5 litres was very likely an actual difference.

So, to answer your question Joel, no you absolutely will not harm anything with an exhaust mod. You also will not see any real performance gain either. The only reason I do exhaust on late model TJ’s anymore is either for sound, or because of suspension mods.

To elaborate on what Clay said, just so you guys are aware. Any exhaust system bolted to the motor will provide enough back pressure for the engine to run properly. The only way you could drop the pressure enough to be detrimental to your engine is to actually run with no exhaust bolted to the motor at all. Just a bare head. That can definitely hurt things. I would imagine that’s the type of backpressure Clay was referring to.


HTH

[Spinalguy]

That makes sense Bill. The jeeps that were always discussed were TJ's. So Scott's YJ would have gains.
Thanks
TK

[yjcanibul]

following the 'when neccessary' rule I put a '91 4L ho head on my 89 yj 4.2L and cut the rotten oem exhaust off replacing it with a stainless borla '91 header/catback and oem '91 cat to match, all shiney and it all bolted right up ... 5yrs now and it still sounds great,  I've driven 1 other good shape ho (91 renegade) and this combo is way way more responsive 1st/4lo to 5th overdrive ...

in cgy city w/33 bfg , 410 gear I get 440km a tank with k&n and unlocked hubs ...

my decision to go stainless was cause I somehow think quality will pay for itself over years and cause I did this thing myself I was ok with putting the labour $aved into the part itself ... sometimes I am wrong and sometimes it works out ...