De-Cat, cat delete bypass, Resentor bypass

Or what ever you like to call it lol

 

Just spotted these for sale in the UK

 

http://www.prindiville.co.uk/products/lamb...lete-silencers/

 

I will admit I'm not a huge exhaust expert and usually just run OEM in anything I've owned, or at the most changed the rear silencer. However my Diablo already came with the rear silencer delete pipes and while browsing the net I came across the cat delete system above, so just wondering what are people's thoughts on going this route?

 

Less heat?

More HP?

How much louder?

 

 

 

I still have primaries with the Fabspeed exhaust and my car is very loud. I can't imagine without the primaries but it depends on what muffler you have. If you're deleting the all the cats but have the stock muffler I don't think it will be too crazy loud.

Hi,

 

This is all I have in my car,

 

 

 

You'll shave some weight and heat, but it will be LOUD. I added the secondary cat delete (US Spec) and muffler delete to the Murci, but kept the primary cats and it's still loud, especially on the motorway. It's okay around town but after a few hours it starts to get annoying.

Secondary cat delete plus some kind of sport muffler = loud. The O2 sensors are still chillin' in there at the primaries. You can carry on a semi-strong conversation inside or outside without yelling. With either a QS or Larini, the tones are still low and aggressive rather than F1-screaming, but there are some droning notes at certain low revs. I also agree that keeping the stock muffler is the main ingredient to less noise after hearing different cars with different setups (I still like the stock Diablo sound).

 

I thought my car might be too loud at first. After living with it, I have grown to love it and I rely on it sounding a certain way to let me know how it's doing. Despite its volume, the exhaust system seems to let the car communicate better. Everything has a clarity and an immediacy going through the exhaust that gets subdued on stock Diablos. Most of all, I love the bark and growl starting it up...like I just went out to the barn and woke up my dragon. It makes me say Fk Yeah every time I crank it. The cockpit noise probably isn't healthy, but fkit, it's outrageous.

Sudesh it looks like you have muffler deletes but you still have primaries and secondary cats. The FABSPEED still has mufflers albeit small ones. If you delete your secondaries I think you will be pretty loud.

Loud is good! I deleted all that crap and basically have straight pipes out the back!

Thank everyone for the advise.

 

At the moment, I don't think mine is that loud, well it's bearable anyway lol

 

Apart from creating more noise, is there mhc HP gain? The weight saving and heat issue is a bonus too.

 

 

Loud is good! I deleted all that crap and basically have straight pipes out the back!

 

Any pics Allan?

Thank everyone for the advise.

 

At the moment, I don't think mine is that loud, well it's bearable anyway lol

 

Apart from creating more noise, is there mhc HP gain? The weight saving and heat issue is a bonus too.

 

 

 

 

Any pics Allan?

 

Deleting all the cats is a big Hp gain, plus you lose some weight. Also, the cats are known to disintegrate and get sucked back up into the motor, which is very bad. Ill see if I have any pics. My system is straight pipes that go out to two tiny Burns mufflers that are actually part of the exhaust tips.

Deleting all the cats is a big Hp gain, plus you lose some weight. Also, the cats are known to disintegrate and get sucked back up into the motor, which is very bad. Ill see if I have any pics. My system is straight pipes that go out to two tiny Burns mufflers that are actually part of the exhaust tips.

 

Thanks Allan,

 

How did you get around the 02 sensors?

Sudesh it looks like you have muffler deletes but you still have primaries and secondary cats. The FABSPEED still has mufflers albeit small ones. If you delete your secondaries I think you will be pretty loud.

 

Yeah muffler is gone and straight pipes added there. I like the idea of weight saving, lower heat and more HP, but not sure on how loud Id really like to go.

 

What about Emissions and the 02 sensors?

Hi,

 

This is all I have in my car,

 

 

Looks like you have a quick silver muffler delete. Pretty loud if you remove the secondaries, basically just like what Chipster and I are running.

 

If you delete the primaries expect about 110 decibels.

 

I will honestly say that there is no way I would DD a car as loud as the Diablo is. I've gotten used to it but those who know me know I wear hearing aids and even with them my hearing still sucks. That being said, my drive up and back to NY for Bullfest in May....I removed my hearing aids lol. I have neighbors blocks away that tell me they known when I start the car. Just depends what you like! It does sound good though

Hi Sudesh.

 

The UK supplied Diablos have the system you have, the ones that delets the muffler. I belive it was done at either the factory or at Portmans Lamborghini, but I am not sure why?

The system is made from steel, and not with with a very nice nice finish. Also you will notice that these early UK cars have 2 or 3 fixing points for the exhaust/muffler, where the US/EU cars have 4 points. Atleast from the 5-6 UK cars I have seen. Something to concider if you go for an aftermarket sports exhaust.

 

When I got my car it had the same system has you have now. UK type muffler delete, stock cats, and stock quad tail pipes.

It sounded quite good, but not THAT loud.

 

I then added some stainless steel cat deletes pipes (test pipes), so basically a straight thru system. VERY loud, espeecially on cold start up. Really fun for some short drives, but so loud that the interior shakes and rattles. 106 db(A) at idle a meter behind the car.

 

I then had a second set of cats, but hollowd out and with a straight pipes in the center section. Compared to thin gauge stainless pipes, this dramatically reduces the noise, as the hollow barrel around the pipe also acts as a mufflers.

The power difference with the old cats deleted is also significant, even if they are not collapsed yet. A fair guess would be 30-50hp, and I would love to test that on dyno when I get the oppertunity.

 

Other mention pre-cats and secondary cats. Early cars only have the two big main cats, no pre cats. But they do fall apart inside.

 

I have modified the twin exhaust setup from Murci roadster, including the butterly vac. valves, to fit a Diablo. Togheter with the straight pipes and and cat deletes this exhaust is the perfect combination for me. Very loud when you rev the car and accelerates, but no drone at cruise.

 

Here is the stainless deletes pipes, which also adds some nice flames on the over run.

 

Here is the system in parts before it was cleaned and polished.

 

 

Going forward I think I would consider adding some aftermarket cats from Random Technology, to be welded into my ss test pipes. I have a set like that on my Corvette, and they did not steal any power, but kept the car legal for emission testing.

Hi,

 

Thanks for the reply, very useful info! Interesting there are so many differences between the cars depending on country of origin.

 

And correct on the sound, as my car stands, it's not that loud ; in fact when inside the car it doesn't sound loud at all. I also have the blocked off vent pipes that decrease the revs on start up, so now when I start my car in the mornings, it idles quite low and quite, I just let it sit until it reaches correct temp [fans come on] before driving it.

 

Straight through would be too much, don't fancy the interior shaking and rattling. How was the car at MOT? And what did you do with 02 sensors?

 

I'm still curious as to this setup http://www.prindiville.co.uk/products/lamb...lete-silencers/

 

Looks similar to the cats so maybe has better control on the sound?

 

 

Hi,

 

Thanks for the reply, very useful info! Interesting there are so many differences between the cars depending on country of origin.

 

And correct on the sound, as my car stands, it's not that loud ; in fact when inside the car it doesn't sound loud at all. I also have the blocked off vent pipes that decrease the revs on start up, so now when I start my car in the mornings, it idles quite low and quite, I just let it sit until it reaches correct temp [fans come on] before driving it.

 

Straight through would be too much, don't fancy the interior shaking and rattling. How was the car at MOT? And what did you do with 02 sensors?

 

I'm still curious as to this setup http://www.prindiville.co.uk/products/lamb...lete-silencers/

 

Looks similar to the cats so maybe has better control on the sound?

 

The O2 sensors are placed in the header 3-way collector pipe, before the cats. (pre OBD II car, so only 2 sensors total.), so the exhaust system from and including the cats is not affected by this. However, there is some thermo sensors placed in each cat that send a signal back to to ECU. When the cat temperatur gets to hot, it will put in the check engine light for that bank, and propplery go to limp mode, to prevent melting the cats.

The system is unaffedted if you leave the sensors out with test pipes.

 

The pipes in your link looks like muffled test pipes, which would propperly be a good choice, IF your are not concerned with the emission inspection.

Hi,

 

Thanks for the reply, very useful info! Interesting there are so many differences between the cars depending on country of origin.

 

And correct on the sound, as my car stands, it's not that loud ; in fact when inside the car it doesn't sound loud at all. I also have the blocked off vent pipes that decrease the revs on start up, so now when I start my car in the mornings, it idles quite low and quite, I just let it sit until it reaches correct temp [fans come on] before driving it.

 

Straight through would be too much, don't fancy the interior shaking and rattling. How was the car at MOT? And what did you do with 02 sensors?

 

I'm still curious as to this setup http://www.prindiville.co.uk/products/lamb...lete-silencers/

 

Looks similar to the cats so maybe has better control on the sound?

 

The O2 sensors are placed in the header 3-way collector pipe, before the cats. (pre OBD II car, so only 2 sensors total.), so the exhaust system from and including the cats is not affected by this. However, there is some thermo sensors placed in each cat that send a signal back to to ECU. When the cat temperatur gets to hot, it will put in the check engine light for that bank, and propplery go to limp mode, to prevent melting the cats.

The system is unaffedted if you leave the sensors out with test pipes.

 

The pipes in your link looks like muffled test pipes, which would propperly be a good choice, IF your are not concerned with the emission inspection.

Hi,

 

Thanks for the reply, very useful info! Interesting there are so many differences between the cars depending on country of origin.

 

And correct on the sound, as my car stands, it's not that loud ; in fact when inside the car it doesn't sound loud at all. I also have the blocked off vent pipes that decrease the revs on start up, so now when I start my car in the mornings, it idles quite low and quite, I just let it sit until it reaches correct temp [fans come on] before driving it.

 

Straight through would be too much, don't fancy the interior shaking and rattling. How was the car at MOT? And what did you do with 02 sensors?

 

I'm still curious as to this setup http://www.prindiville.co.uk/products/lamb...lete-silencers/

 

Looks similar to the cats so maybe has better control on the sound?

 

The O2 sensors are placed in the header 3-way collector pipe, before the cats. (pre OBD II car, so only 2 sensors total.), so the exhaust system from and including the cats is not affected by this. However, there is some thermo sensors placed in each cat that send a signal back to to ECU. When the cat temperatur gets to hot, it will put in the check engine light for that bank, and propplery go to limp mode, to prevent melting the cats.

The system is unaffedted if you leave the sensors out with test pipes.

 

The pipes in your link looks like muffled test pipes, which would propperly be a good choice, IF your are not concerned with the emission inspection.

Ah yes! Heat sensors, should have know better as these were also in the cat on my NSX and have the braided type wire coming from them.

 

I just had a look and on my car, the sensors arnt even connected? The sensor side is bolted into the the cat ok, but the other end isn't plugged into anything, was just taped up and tucked away.

 

I'm waiting for Prindiville to contact me back as I've sent them some questions.

 

MOT would be the only real worry, our MOT in N.Ireland is much more strict than UK, so not sure how that would go, suppose at the worst I could swap the cats back in, but becomes a pain even if it's only once year. I don't think pushing the "its a classic car" thing would work either, even though its 20 years old.

Ah yes! Heat sensors, should have know better as these were also in the cat on my NSX and have the braided type wire coming from them.

 

I just had a look and on my car, the sensors arnt even connected? The sensor side is bolted into the the cat ok, but the other end isn't plugged into anything, was just taped up and tucked away.

 

I'm waiting for Prindiville to contact me back as I've sent them some questions.

 

MOT would be the only real worry, our MOT in N.Ireland is much more strict than UK, so not sure how that would go, suppose at the worst I could swap the cats back in, but becomes a pain even if it's only once year. I don't think pushing the "its a classic car" thing would work either, even though its 20 years old.

 

The wire should go to a white plastic "control box" behind each rear wheel well. As said, the only thing that can happen is that you do NOT get a warning on the dash if the cats overheat. which is likely when the old stock cats collaps.

 

Try and remove your cats and shake them a bit, see and listen if any cat internals falls out. If so, do not drive with these.

The wire should go to a white plastic "control box" behind each rear wheel well. As said, the only thing that can happen is that you do NOT get a warning on the dash if the cats overheat. which is likely when the old stock cats collaps.

 

Try and remove your cats and shake them a bit, see and listen if any cat internals falls out. If so, do not drive with these.

 

Ok, im just back home again, so give me 15mins and ill pull the cats out.

So cats are now out, Nothing has come out of the cats or any old debris. But can I ask, are the cats supposed to be hollow? Im 99% sure there aint a thing inside there!

 

 

 

One of the bi-cone rings has some damage/cracks, so need to get a replacement, going to replace all the gaskets and get some new bolts too.

 

 

 

These are the gaskets I use on the NSX and actually fit the Diablo too

 

 

 

 

You should be able to see the honeycomb like catalytic material in there, when cats are good and healthy. Sounds like yours are empty, which could also explain the thermo couplers being unhooked.

You should be able to see the honeycomb like catalytic material in there, when cats are good and healthy. Sounds like yours are empty, which could also explain the thermo couplers being unhooked.

 

Ill give it a good check shortly, but I don't think there is anything inside the cats.

Just had a good check, cats seem to be empty, was able to put a twisty inspection bar straight through it, also put a ball inside and it bounced through it freely too. So guess Im running a straight through system of sorts.