2001 pre cats question

[Tobyspaw]

I'm not advocating removal of catalytic converters but,is there a way to move the precats under the hood to a different location? I understand the computer takes readings from these and adjusts fuel (I think). They are just so damn hot. The E-fan overide has helped my hot start issue immensely. ( Thanks Mudderoy). I have access to older style exhaust from jeep junkyard near me. Is there anything I should look for?

[bluedragon436]

The 01 had two O2 sensors prior to and after the pre cats correct?? I was thinking you might be able to run the older style that has only the one cat down stream... but trying to think how you'd run that to keep the computer happy.... You have the ability to weld in an extra O2 sensor bung into the piping?? If so, then you might be abel to just do that, so that the computer will be happy getting the four readings... or almost wonder if you'd be able to run the older exhaust setup, with a 97-99 ECU (like maybe one out of the same XJ you pull the exhaust setup), and then it'd be fine with just the two sensors like a 97-99 runs... I can imagine the heat under the hoods of the XJ is already pretty warm, can only imagine how much warmer it is with the pre cats there...

[tinythexj]

I woud rather keep the two O2 sensors on the underside of the jeep rather than closer to the engine and a huge heat source. You can try wrapping the exhaust manifold with header wrap to eliminate some of the engine bay oven like temps. I'm going to be contacting a local metal fab shop here shortly about making a custom hood vent similar to that of poison spyder's for the wranglers to help vent some of that heat while crawling.

[bluedragon436]

I was going to say another option you can go with is hood spacers or vents... or in my case I might be running both.. lol.. already got my hood vents sitting at home, and have spacers on the way... figure for now I'll run the spacers and see how that does for keeping the temps down and if more is needed then I'll run the vents too... Once I get down to SC I'll most likely be running both anyways... just don't know how the vents will do in teh snow up in DE..

[tinythexj]

I forget where I've seen it but someone posted the research of the best locations for the vents in order for them to have different effects on the motor. Does the jeep run hot now or are you looking to tame the temperatures at lower speeds?

[Tobyspaw]

I just want to eliminate some of that heat while keeping the computer happy. Running the e-fan has taken care of the misfire issue after hot restart,but I'm sure it will eventually shorten e fan and battery life. Thought about hood venting but I would like something waterproof as in open and close. Wondering if older computer would sync in correctly?

[xj-jake]

Okay a couple things here and I may be wrong but someone can feel free to correct me if I am. First I don't believe older computer will work. 97-99 engines had a distributer whereas the 00-01 run the individual coil packs on the top of the spark plugs.

As far as moving the cats and sensors. I just replace the cat in my Jeep and questioned the exhaust shop on the placement of the O2 sensor. On the cat that I installed the O2 sensor was nearly inside the cat. When I asked about it he said it was move in there to use the heat of the cat to help the sensor with it's reading. In a sense I guess what I got out of it they were "fooling" it to get a better reading to the computer...

Wrapping the exhaust is probably where I would start and then move on to vents. I haven't done vents and probably will not just due to the snow we get in the winter.

[bluedragon436]

Okay a couple things here and I may be wrong but someone can feel free to correct me if I am. First I don't believe older computer will work. 97-99 engines had a distributer whereas the 00-01 run the individual coil packs on the top of the spark plugs.

Wrapping the exhaust is probably where I would start and then move on to vents. I haven't done vents and probably will not just due to the snow we get in the winter.

You're correct.. I completely forgot about the distributorless setup of the 00-01's.. Only thing I worry about with the wrapping of the exhaust manifold is that it might cause more stress on our already crappy designed manifolds, even the 00-01's, and might cause more chance of cracking... I feel you on the vents w/ the snow... that's kind of why I'm looking at doing the hood spacers for now, then do the vents once I get down to SC where we dont' really have much snow if any at all..

[xj-jake]

You're correct.. I completely forgot about the distributorless setup of the 00-01's.. Only thing I worry about with the wrapping of the exhaust manifold is that it might cause more stress on our already crappy designed manifolds, even the 00-01's, and might cause more chance of cracking... I feel you on the vents w/ the snow... that's kind of why I'm looking at doing the hood spacers for now, then do the vents once I get down to SC where we dont' really have much snow if any at all..

By wrapping the manifold wouldn't it sort of force the heat down the exhaust and out the rear?

[bluedragon436]

By wrapping the manifold wouldn't it sort of force the heat down the exhaust and out the rear?

Could be wrong and most likely am.. but think that would depend on how flowing your exhaust is, as to how well it'd flow down the line...

[Tobyspaw]

I'd like to get some temperature readings from one of those temp scanner guns but I don't have one. I know it's very hot.

[Tobyspaw]

California is the reason behind those pre cats...am I right?

[tinythexj]

Wrapping the header shouldn't cause it to fail unless there was already an issue there. It will help insulate some of the heat from radiating to the surrounding areas and should help reduce engine bay temperatures. Most people just don't do it because they don't think to do it and depending on the application can get pricey.

[Carves]

Going by my experiences with rotted out motorcycle headers,

... wrapping is not such a flash idea - if things are going to get wet.

Probably be all right on a street driven car ... but not so good on a mud wallowing / submarining XJ .. ;);)


As for venting .....

Vent according to the vehicle use.

If you are never going to drive above 25mph ... then chop holes in the bonnet anywhere you want.

... but think about whether that rising, fan forced air ... used to provide a little cooling for the gearbox.

If you will be street/road driving as well ... The vents need to be in areas that dont introduce reverse airflow ... which can upset the radiator air flow.

e.g. spacers and cowl hoods etc.

... remember that, proper, camaro scoops - had ducting that directed air to the airfilter ... NOT, just let it waft all over the engine bay,
... coz they were a cold air intake ... NOT a vent.

http://i1143.photobucket.com/albums/n629/carves-oz/Vehicle%20Bits/Cooling%20Bits/Camaro%2001_zpsusvwl6xe.jpg

Spaced bonnet hinges work OK as a low speed vent ... turns the whole bonnet into a comaro scoop ... but needs a seal between the hinges for road driving - to prevent it becoming an intake.

Plenty of heat/hot air will rise out/blow out a 1/2" high gap, at the rear corners ... at low and high speeds, with the centre area sealed to the firewall.

http://i1143.photobucket.com/albums/n629/carves-oz/Vehicle%20Bits/Cooling%20Bits/3inchMarineVent_zps5785174f.jpg


Ideally, imho ... the best all round venting for the XJ - would be behind the wheel arch ... but I havent settled on a method of attack - that wont destroy the integrity of the inner sheet metal yet,

... so I'm still just relying on a quality fanclutch ... and driving the vehicle within its capabilities.

[Tobyspaw]

Thanks for all the replies. I won't be in the mud or water so I may look into wrapping.