Hello all,

In the process of replacing the power steering hoses, figured it would make it a great deal easier if I removed the downpipes with cats which I'd wager has to be the most unpleasant job on the car. Anyway, my question is what is the recommendation for exhaust layout? I'm planning to remove both cats as they are not required in my area and I want to reduce the heat buildup in this area. I also consider the UK spec to be the intended form of the car for 1990 so I deem it an appropriate modification. I'd like to keep the car comfortably quiet, can stand a little more noise but not after a boy racer type deal. I'm looking at the following options:

1. Cut off the first cat on the stock downpipes, remove the honeycomb, have exhaust shop tie downpipes to rest of exhaust, keep rest of system stock
2. Buy new downpipes from UK performance shops to tie into intermediate pipe and rest of stock system

I'm leaning towards option 1 for the cost savings as the exhaust is not really important to me beyond doing its job and keeping the noise/drone down. My worry is to have a car at the end with an annoying droning sounds. Any thoughts on the two options or any other suggestions?

Thanks all,
John

 

Without a looooong story (I'm hard headed) I would suggest tracking down a set of OE CATless down pipes from the UK or European market on eBay or such other (unless ya have $ for aftermarket performance type) and keep it simple. The only thing needed after that is a longer intermediate (down pipe to mid silencer) pipe with a proper flange and olive. 2 inch olive that is. A muffler shop can sort that out cheaply.

If access and added HEAT are what you are trying to deal with in the area, leaving the gutted CATs in place doesn't really accomplish this.

Soundwise, although I never had a right running car OR a leak free exhaust with the OE CATs,,, the sound difference without CATs IMHO is negligible. No big deal.

It might take a while to track down the cats, a fellow member helped me with that, but worth it, I think...

 

I had a slightly different issue on mine- I needed the over axle pipes and could not find them. Finally found them with SimplyPerformance in the UK and ordered everything from the down pipe back, Reasonable, not too expensive for shipping, quick, and absolutely beautiful quality exhaust parts. They make a beautiful down pipe to replace the cats, but I needed to keep them.

Anyway, I would check them out- really great to work with and really high quality.

 

On the drone front the mid boxes are the place that gets addressed but because of their form they are also quite restrictive, I don't think you can replace the CAT down pipe without replacing the mid section due to the fittings used. I also have a SimplyPerformance system and the quality is definitely there - wasn't cheap though so I guess 'reasonable' is subjective. I'm pretty sure Ben at Simply can sort you out.

Car was never designed to have CAT's it was a legislation thing, the heat in that area is significant even without them so if you can do without them then that's a good move and the rack will thank you for it.

Plan to replace the studs and nuts on the manifold fitting, I'd use brass nuts, if the studs are OK you can leave them be but just have a plan. The one thing you do not want to do is break one off so keep the gorilla in check when removing the nuts and don't just apply more and more force - slow and easy, doses of release agent - which WD40 is not. In fact don't re use any of the exhaust fittings/bolts would be my recommendation on any vehicle.

 

Thanks all. Is there a difference between the OE catless downpipes and mine with the cat cut off? If a shop can weld a bend on it which would then attach to the intermediate pipe and the rest of the stock system, I'd be good right?

I'm hesitant to go the UK route due to how long it will take to get here. I'm at the end on the maintenance items and really don't want to wait another couple of weeks if there's a valid way around it.

Ben - hear you there on the price, that is the other thing steering me away from the route. And I did get the downpipe off the manifold, what a horrible job that was. Just have to drop the steering rack to get it off the car now.

I'd like to do as little exhaust work as possible, probably the only job I don't mind having a shop do on the car.

 

You can weld a piece in but fabricate it when the system is on the car - at least tack things in place while it is there as you don't want any stress or pressure on these things if it can be avoided. If a shop does it just put them back on temporarily so you don't burn the car down - (run it without the exhaust at night with the lights off and give it some throttle you'll figure out why not to run without the exhaust pretty quickly)

 

LOL, oh yeah, I've ran it without the 2nd cat on and she was loud. Would there be any issue with a 12 minute drive to the shop with just the downpipes? My intermediate pipes were rusted through and I started cutting the first cat off the car in an attempt to get better access to the mounting nuts. So I'd need to get a bit creative if that is not drive-able.

If so, I'm planning on bringing the shop just the rear silencers and over suspension pipe off the car with the downpipes attached and getting them to fix it. Also going to ask for a notch in the intermediate pipe where it covers those transmission pan bolts.

Cheers!

 

Hmm. A couple things.

Releasing the steering arm/rod off the steering rack tower SHOULD allow you to remove the the old downpipe. If not that, lossening the steering rack and or removing heat shields. At the most a tie rod and steering arm. In my experience you should NOT have to drop or move the subframe.

I would avoid cutting or welding of the downpipe unless you have a cracker jack welder... 1/4 inch angle, off at the connection point at the down pipe, multiplies in distance as the intermediate travels away from the front of the car to rear... Placement of bungs for 02 sensors, right curves in tunnel etc,,, not completely straight forward.

Get the performance stuff OR,,, the OE downpipes, if they can be found, will ship, surprisingly, faster than some domestic stuff... Lol,,, don't get me started on shipping times and suppliers, smh... Also, stay away from the "Weber" (I think was the manufacturer) downpipe. It just ain't right...

Wait a week,,, it's a part that will be in service once placed, maybe 20yrs. What's a weeks wait for getting it done?

 

These?

XJS V12 Front down pipe s, JagParts

 

Dangit Jay!! Just when I thought I had a plan...

So I'm not planning on doing this work but having a reputable shop in my area do it. I started cutting the downpipe right at the weld to the first cat so I thought I could reuse the O2 sensor.

I hear you on doing it once and doing it right. I'm open to buying new downpipes, I saw ones available domestically here: https://www.terrysjag.com/category/X...-CATALYST.html

The only thing is I really don't want to spend more on the exhaust than I have to! Not a priority system in my eyes as it was working fine before. Just want the cats out and gone the easiest way possible without creating a noise machine!

 

Will depend on the centre section I think - weren't some of the CAT downpipes pretty long I think there were two types, three if you count post 1993 6 litre

 

Side question as well before I work on this nut some more after work.. How important is it to center the wheel before undoing the universal joint? Mines at about 1 o'clock. Wouldn't imagine it would make a difference but better safe than sorry.

Also Ben, do you mean the intermediate pipe? If so, mine are rusted through and soon to be scrap. Figured the shop would replace them with what they need to be.

 

Check post 9...

 

Centre the steering wheel - trust me once you start and figure the challenges the reason will be apparent - I struggled in a big way and my engine wasn't even in the car. There's a special tool for locking the rack in a centred position but you will find the wheel has quite a bit of potential rotation even when the steering lock is set so getting spline perfect requires a few 'wooosa' sessions ..... (Bad Boys 2 Woosa Youtube will tell you what these are).

Can you just move the steering wheel a spline or two sure but then you need to mess with indicators and such ... depends how picky you are

 

Jay - Gotcha, I'll call and double check the local one, believe mine is the later version as just 4 studs used. Will also verify the p/n once the downpipe is off.

Ben - Man am I glad I asked... Does neutral turn off the steering lock?

 

I don't think it does - all mechanical - for sure mine isn't in park - not sure what gear it is in as it is disconnected presently

 

Steering lock disengages with ignition on, any gear. Turns out, with the downpipe removed, it was not too bad to undo the power steering lines.

I think I'll move forward with the OEM downpipes modded. I'm taking her to a reputable shop and will see if they have any qualms about it.

Last item would be whether or not its safe to drive with just the downpipes? Is the heat output enough to warrant looking at a creative temporary pipe to make the 10 minute drive to the shop?

 

It will be loud with just downpipes and you're putting a bunch of heat beside the transmission. For a short drive probably ok, as long as your don't get pulled over by the police for noise.

As an aside, I removed the cats from one of my V12's and put in the Euro downpipes and I wish I hadn't. The exhaust really smelled and I noticed absolutely no difference in performance.

 

Yeah I wont be leaving early, that's for sure.

I'm not after performance, though given how restricted the NA OEM setup is, I'd have to imagine there is some benefit there no? My main reason is to reduce heat buildup in that area and keep heat away from the transmission other parts in that area.

If it ends up being a poor choice, I'm planning on fitting a cat alternative.

 

The biggest benefit to ditching those things is heat management, it also makes a little more space for airflow.

For a 10 min drive you should be OK if you don't go all Le-Mans, keep the rpm down - the exhausts can and do spit fire. Make sure you support the remains of the exhaust if nothing is in place as it is heavy and not particularly well supported at the front.

I don't think it is a poor choice - heat is the enemy on these cars, it isn't unknown for the cats on them to catch fire if anything is out of order in the fueling system.