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ive just had my right hand cat failed and its rattling like a bastard and is blocking exhaust gases badly. so i need new cats. ive looked on here and see that lotus originals are expensive and crap so it doesnt take much working out. so i see you can buy higher flow cats for less money and there better for performance. anyone had any experience on what to buy and where from ?

steve

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Hi Steve,

PNM do some very sexy 200cpi SportCats, which would be my first recommendation.

There are other options if you want to spend more money - Ramspott & Brandt / PUK Esprit.

I need an exhaust and cat arrangement for my project car and I

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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Hi Steve,

I didn

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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the cheapest way to go would need some skills, but this arrangement passed even he strictly emission & car test (T

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to name the things if I see them, that's what I call integrity..

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thats good stuff. doing a bit of fabrication and welding is not a problem. looking at the pics i think i could get away with fitting just the rear cat inserts. just to clarify if i cut off the rear section, do i weld the new cat insert to the section i just cut off and then insert that assembly inside the old casing and then weld the two together. you say the rear is 120mm diameter do you know the length ? steve

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as said, I have used some from the after-market (e-bay) ... .

You can undo your old catalyst, look from the silencer side into it ...and what you will probably see is broken ceramics -or even nothing left (apart from white powder & the two black metal rings who have hold the ceramic-monolith).

Measure the 'inner'-length of the rear section on your existing casing (mention the ability to fit the rear O-2 probe, and the step in the casing (98mm/120mm). Compare that with the drawings in the internet.

If you cut (only cut the weld, not the entire casing !) along on top of the 'weldline', the rear part of your original casing will go off. You can see that it is fitted into the end, and was then welded together.. . Chose one of the aftermarket catalyst with right diameter to fit it onto the casing-endsection (cut the ends off the aftermarket parts..) . But be carefull, don't cut into the steel mesh !! You will need some metal overhang anyways, to hold the welding/weldspots in an sufficiant distance from the steel mesh (it would melt , of you go to near onto it..). fit all toghether (mark the depness/position of both original casing ends). And ready to go for an emission test.

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to name the things if I see them, that's what I call integrity..

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hi dave thats an interestiging option are these standard lotus items. i must admit i have been eyeing the 200cpi sports cats on your site. i had to knock the cat centres out effectivly making them straight through. i didnt realize how restrictive the standard cat are but on the down side it does increase the noise levels. so sports cats are looking very appealing. its just a case of puting forward my expences claim to the mrs and see if they get rejected or not. timming is allways key in this process ! :P

Edited by braziers
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300GBP for a pair of functioning V8 catalysts is really a great offer ! The only advantage of my advice is that you get more skills on welding, and you can chose the cell/in^2 rate...

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to name the things if I see them, that's what I call integrity..

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that's bringing some different light into the story.. .

Lotus-OEM ceramic catalyst are rated in the 400+ (probably 600 cell/in^2) ?! Would mean still a lot of backpressure and the same lifetime as of the one fitted in his car earlier.

But on the other hand 300GBP and no welding -why not ! :P

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to name the things if I see them, that's what I call integrity..

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  • 1 month later...
  • Gold FFM

hi dave thats an interestiging option are these standard lotus items. i must admit i have been eyeing the 200cpi sports cats on your site. i had to knock the cat centres out effectivly making them straight through. i didnt realize how restrictive the standard cat are but on the down side it does increase the noise levels. so sports cats are looking very appealing. its just a case of puting forward my expences claim to the mrs and see if they get rejected or not. timming is allways key in this process ! :D

Hi Steve,

What is the current status of your CAT problem?

I have a good driver side (pretty sure that is correct, I will double check) original Lotus CAT which I would swap for one with damaged innards if that is of any interest?

On another note, what is the general opinion of running a system with a high flow CAT on one side and a straight through pipe on the other temporarily?

I managed to chew up a metal CAT on the motorway which was interesting to the BMW following as something resembling a red hot brillow pad bounced down the road infront of him (it was sparking enough to catch my attention ;) ) This was a knock on effect from my standard rear box developing the common stress cracks in the outlet causing it to wobble. I swapped this for the sports box as a precaution which then caused popping and crackling on deceleration. While I like the popping and crackling I think the CAT likes it much less. :)

cheers

-Chris

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the problem is with different internals -as we all know on some markets you need to have 4 sensors and 4 catayst-lements to pass emission tests. On the other hand, if an 02-sensor gets older the variations on reading of the O2 content will not be as exact as it was on the first day. So there can be a lot of false-regultions on air/fuel-mixture for the related engine bank. Under normal conditions the ECM should be able to verify that the starter-catalyst (the first small one..) is working well by noticing of the different reading between first & second o2-sensor in the pipe. If the second or the first O2-sensor is not working right the ECM does not have an exact information on how to calculate the mixture in real-life condition. Same is for the possibility of an not working starter-cat , if the readout of the second sensor looks exact like the data from the first...as this would mean : no catalyst fittet, or catalyst aged , or fuel-mapping not right.

Now imagine your car is programmed/maped for US-standarts ....and you run with *one side catalyst option* -and *non catalyst option* on the other pipe. Think this will give a lot of irritation in the ECM , causing an steady misfueling on one bank (ECM gets back on 'open loop mode' eventually) ...what means unstable running condition, and higher stresses for the engine?

So I would allways prefer an equalised arangement for both sides.

US-calibration with 'fouled' O2-sensors in the rear, or with 4x 200cell metal race catalyst. Or even for the early European cars just one O2-sensor in front of each side ...and no catalyst at all (optional with one bigger 200cell metal catalyst per bank in the bigger casing section to pass any emission test later on...)

Edited by Günter

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to name the things if I see them, that's what I call integrity..

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Hi Gunter,

The metal CATs are a single 200 cell unit after the primary O2 sensor and the secondary sensors are ignored by the ECU (I am sure you can guess why :D )

So in my case the O2 sensor readings should both be identical even if one side has a CAT and the other doesn't. So the only real issue might be different back pressures.

In any case I was hoping to have the car on the road for today (I have a business meeting at Lotus Racing ;) )but the weather is crap so I am in my aging Seat Ibiza instead, so now it is a hypothetical question.

cheers

-Chris

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As you say: with a 'rear sensores ignored by ECU' car -you have an stock Euro2 rated emission calibration ....or one of the Johan/Marcus chipped Race ECU by chance :)

Anyway, sounds similar to my actual setup [per today] with main sensors, 200-cell metal on each side -and rear sensors 'unplugged'/removed... . With 200cell setup I would gues there isn't a real notable pressure difference if one side is hollowed ?! As long as the signals feed into the ECO do not show any 'iritational' signals -OK, why not run this option :thumbup:

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to name the things if I see them, that's what I call integrity..

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  • Gold FFM

So my next question is how do I weld stainless steel pipes and CATs together?

I have an Oxyacetylene torch which I suspect is not suitable but perhaps it is with the right rods?

Or do I need a Mig or even a Tig welder to replace the knackered CAT?

I am not too bad with the gas torch when it comes to welding but I haven't done any Mig or Tig yet but I would relish the challenge. :)

cheers

-Chris

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stainless is basically some sort of *Chrome or Nickel* steel, or similar alloys to hold the reactions within the *metallic crystal structures* down... .

But if you look closely onto the tail-pipe tips on an Lotus stock V8 silencer, you will notice that the silencer is ordinary metal -and only the pipe-end is stainless. It is welded together with ordinary MAG system and universal wire.

You can see it in detail by the 'crystalline structure insufficiencies' -or lets name it 'rust' on the welding, and in opposite the stainless end is not rusted. All in all -it means you can weld stainless steel in a basic level with an MAG and ordinary wire, but it will rust and the weld lines can break over the years as for the structural imperfections.

Same effect is there if you weld something with wire that was not stored dry and had rusted on the coil wile in use... . The welding will be imperfect on those points.

For perfect welding on stainless to stainless: -use MIG [or WIG] systems ...together with the right type of wire on the coil in the MIG welder [in terms of WIG - should say: 'with the right type of metal stick' .. as it is not a coil in this case.. rolleyes.gif ]

Ordinary metal to stainless: -use any type of MIG/MAG welder as you like ...the imperfections in the alloy structure will make it 'rusty' anyway.

Acetylene systems (traditional plumbers work) will do the weldings on simple steel too. But the amount of heat transfered by the flame could harm the metal mesh in the catalyst. Mention that an Acetylene flame goes seriously over 1000°C , and the catalyst does have an safe working temperature reaching from 250°C up to around 600°C (nearly..)

An MIG/MAG welder is only hot in short times, and you can use it precise as an spot-welder (I would advice fit the aftermarket catalyst core into[!] the original casing. This way you have all mountings in the same direction and precise as concepted by Lotus. Additionally there is nothing to fear about 'incorrect classifications/labeling' on the aftermarket parts... :stuart:

Edited by Günter

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to name the things if I see them, that's what I call integrity..

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  • 4 weeks later...

well i took the do it myself avenue. the total cost was £210 which i think is great value. and the job took an hour to do once the cats were off. i cut off old cat section and welded in a pair of 200cspi sports cats and a section of stainless tube. these pics were taken before all welding was completed. they fit perfectly. not a lot off money for a pair of sports cats and i didnt think they look too bad !

post-6032-127248867953.jpg

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all the new bits of pipe and cat are in a dead straight line so i measured the length reqired before cutting to ensure correct length. then i welded all the sections except the front part of the cat to the old front pipe ! ie in the photo you can see it is only spot welded at that joint. this is where i was when i took photo. jumped under car to ensure lamber sensors were in correct place and both sides fitted perfectly first time so then welded up completly.

Edited by braziers
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