DIY 4200 sports cats

[philw696]

Thats useful to know, thanks. My emissions concern comes from my recent MOT - it took a minute or so at certain revs to get the machine to give the 3 green lights. Given my car is constipated with large cats in the manifold and then a further pair after the squish pipe, I thought perhaps they might all be necessary. Having said all of this, I have no idea how effective they are given they're 8 years old. I'd hate to spend that time and money and find myself stranded at the MOT centre with a car that can't pass the emissions requirements!

You need a mot tester like me mate. How do you think we get rally cars through the test. Might have to have a forum not testing day in the West Country and mine are only £35. Phil.

 

[MAF260]

You need a mot tester like me mate. How do you think we get rally cars through the test. Might have to have a forum not testing day in the West Country and mine are only £35. Phil.

I'm not well-versed in these things, Phil, but thought that the car still has to satisfy the machine when being tested? It's a long way to Weston!

 

[philw696]

Discretion of the tester and as long as it wasn't way out indicating a more serious engine issue.

 

[MAF260]

Discretion of the tester and as long as it wasn't way out indicating a more serious engine issue.

Didn't know that, Phil. Mine passed any 2 of 3 straight away, but took a minute or so for them to get all 3 green lights. Nothing was way above the limit, all only marginal.

 

[philw696]

My guess would be you had only done a short journey to the testing station and not fully up to temperature. The oil takes a lot longer to get to temp than the coolant.

Sent from my Nexus 4 using Tapatalk

 

[MAF260]

Bang on, Phil. Maybe a 10-15 minute ride first thing in the morning. I shall remember to make sure the car is fully warmed up next time, thanks for the tip.

 

[mjheathcote]

Quick thought experiment:
Hose pipe or same x-sectional area made up of capillary glass tubes. Which one will provide greater resistance to flow, do you think?
C

Bit extreme, but yes. Therefore better flow would be achieved with the twin larini pipes Siamesed together, you would then loose two walls in the middle for better flow!

I had the secondary cats removed last month but left the squashed pipes for now as the exhaust engineers said they think it isn't that restrictive being of the same diameter as the round pipe but just flat, and they don't think there would be a big benefit to having 2 smaller diameter pipes a la Larini....also they were actually impressed with the quality of engineering to make the 'squashes'.

The squashed pipe is not the same diameter but just flat, that would reduce the cross sectional area. Maserati if you look welded in a larger diameter pipe at that point, and then squashed it, hence why the difference in cross sectional area is not that different.

You need a mot tester like me mate. How do you think we get rally cars through the test. Might have to have a forum not testing day in the West Country and mine are only £35. Phil.

Being from Lotus circles, you get to know where the friendly MOT testers are!

 

[MAF260]

I will do a before and after rolling road comparison on my car when I've done some research and decided what to do.

 

[mjheathcote]

I will do a before and after rolling road comparison on my car when I've done some research and decided what to do.

With the different exhaust manifolds being fitted to later cars/GS, and obvious that the US spec manifolds are of poorer design, having smaller diameter primaries pipes stuffed into the primary cat built into manifold, the HP figures must be different between the two?
Are the published figures that of the superior EURO configuration?
Why does the UK and US owners manual list identical power outputs?

 

[MAF260]

It's an odd one, Mike. I believe that some UK GranSports don't have the primary cats, fairly sure there were a couple of owners on here who said they didn't. There doesn't appear to be any consistency to years or markets. All I know is that mine has the d@mn things fitted and I'm going to try to make her breathe more easily.

 

[2b1ask1]

My MOT tester is very 'friendly', given that mine went straight from the garage it had been in for over 7 months to the MOT (less than 100 yards) the gas test magically came up as almost pure air???

 

[mjheathcote]

It's an odd one, Mike. I believe that some UK GranSports don't have the primary cats, fairly sure there were a couple of owners on here who said they didn't. There doesn't appear to be any consistency to years or markets. All I know is that mine has the d@mn things fitted and I'm going to try to make her breathe more easily.

Nah, must be a mistake, whether US or EURO all have primary and secondary cats.
Maybe the owners when looking under their cars when they have the US cats, only notice the secondary cats and don't notice the primary cats....maybe!
The thing is, it's only the primary cats that are monitored by the ECU, there is no O2 sensor after the secondary cats on either the US or EURO models, so a primary cat is always required, or shall I say, a O2 sensor after at least one cat, and why with sports cats, a single cat after the squashed pipe area, the O2 sensor is repositioned to be after the sports cat.

 

[BennyD]

From what I can emember you can't miss the primary cats on a US spec car or a GS; it's that great big can at the end of the headers.

 

[MAF260]

Hmmm, confusion reigns! I've looked at the Eurospares site and it clearly shows 2 different exhaust manifolds - one set has no cat built in. Seems to go to the squish pipe and then has a cat each side. The other is like I have on my GS - great big ugly cats built into the manifold which then go to the squish pipe and secondary cats. I can source the manifolds I want easily, will then have to work out what to do after that, but reckon it'll be custom pipework with twin pipes like Larini and into some 200 cell sports cats. The only part of the original exhaust will be the pipes between the cats and the rear boxes.

 

[BennyD]

Hmmm, confusion reigns! I've looked at the Eurospares site and it clearly shows 2 different exhaust manifolds - one set has no cat built in. Seems to go to the squish pipe and then has a cat each side. The other is like I have on my GS - great big ugly cats built into the manifold which then go to the squish pipe and secondary cats. I can source the manifolds I want easily, will then have to work out what to do after that, but reckon it'll be custom pipework with twin pipes like Larini and into some 200 cell sports cats. The only part of the original exhaust will be the pipes between the cats and the rear boxes.

I hope you mean between the end of the centre box and the rear boxes, otherwise you will be keeping the crappy silenced X-pipe expansion box thing.

 

[MAF260]

I'm unsure about that bit. I really don't want a dragster sound from the car and think that changing this resonator would open up a world of noise I just don't want! I know mate, shame on me!!

 

[BennyD]

Man up and grow a pair, Princess!

 

[CatmanV2]

Bit extreme, but yes. Therefore better flow would be achieved with the twin larini pipes Siamesed together, you would then loose two walls in the middle for better flow!

'Probably'

C

 

[MAF260]

Man up and grow a pair, Princess!

I can take that from the forum's hairy-chested, macho commentator!!

 

[BennyD]

You are better off getting your back boxes modified like mine as you get to keep your valves and the tail-pipes look standard. Let me know if you do, and I'll help you get them done.