fuel economy greatly improved...

[shorty123]

Had the pre cats removed by webbs a month or so ago and the fuel economy seems to have increased by around 25%, couldnt believe it but i have driven the car a lot over the last 6 weeks and the difference is really significant. Anyone else report a similar phenomenon?

shorty

[that daddy]

blimey,sure you dident do anything else,love your wheels by the way.was that main cat as well.

Edited by that daddy on Thursday 19th October 09:50

Edited by that daddy on Thursday 19th October 09:50

[big_jimmyb]

HI, how do u get away with having the pre cats removed? doesnt it make it un-MOTable??

thanks
Jim

[that daddy]

no,removing the main cats a problem though.

[M@H]

...whilst this sounds great was your MPG ok beforehand or is it now much as it should be? You should be getting about 25-26mpg out of a 400 if you're not hooning it arounds everywhere, so are you now getting 32 MPG !?

[poorpeet]

If you take out the pre cats should you not fit a cone to reduce the diameter of the pipe? Something to do with back pressure I think. If you don't does it matter?

[Nuggs]

poorpeet said:

If you take out the pre cats should you not fit a cone to reduce the diameter of the pipe? Something to do with back pressure I think. If you don't does it matter?

It doesn't make much difference with the 4's. The 5's need non-reversal cones though...

[2 sMoKiN bArReLs]

shorty123 said:

Had the pre cats removed by webbs a month or so ago and the fuel economy seems to have increased by around 25%, .....

...and?

[that daddy]

i must admit 25% that sounds alot,thats why i asked if anything else was done,oxygen sensors etc, did they receive the car running sick,just interested.

[tahiti450]

that daddy said:

i must admit 25% that sounds alot,thats why i asked if anything else was done,oxygen sensors etc, did they receive the car running sick,just interested.

If the pre cats were faulty / blocked as they sometimes can be that would probably not help the pre proceedure MPG and so exagerate any improvement. How did they look?

[that daddy]

thats a good point,as i said it must of been sick before.blocked cats equal running shite.

[GreenV8S]

Nuggs said:

It doesn't make much difference with the 4's. The 5's need non-reversal cones though...

I don't think it's a case of 'need', it works fine with or without, the non-reversal cones are just a nice idea which can take advantage of the spare room left when the precats are out. I'm not convinced the non-reversal cones actually make any difference at all, but if you have already cut the manifolds open it seems harmless to give them a try.

[shorty123]

The Car seemed to be returning an acceptable mpg before the pre cats were removed, but now the difference is amazing. No real performance difference, a bit better breathing, and sounds better.
i was advised on the MOT potential difficulties, but have read on PH that in some cases doesnt affect the MOT too much

that daddy said:

blimey,sure you dident do anything else,love your wheels by the way.was that main cat as well.

No just pre not mains... thanks about the wheels too, will get some better pics/more detail up soon.

[M@H]

..so what are you actually getting... 25-30-35 mpg..!?

[shorty123]

M@H said:

..so what are you actually getting... 25-30-35 mpg..!?

i worked out before the Cats removal that id relliably get around 25-27 mpg, and i recon its got to be around 34 now, i am driving to devon this weekend i'll do a more accurate calculation. Most of my observations have been usage around town over the last month, but the fuel use situation has definately greatly improved.

[.Mark]

shorty123 said:

...id relliably get around 25-27 mpg, and i recon its got to be around 34 now...

Are you driving it properly?

[shorty123]

It may sound crazy and all, but the car is definately returning a significant decrease in fuel consumption. I will be more scientific and get some figures together after this w/e.

[TVRmuppet]

Where in Devon?

[groomvroom]

How do you remove them fro the manifold? Do you have to cut them open?

[crazycraig]

No you don't need to cut them open.

Try this tread - www.pistonheads.co.uk/gassing/topic.asp?p=3&f=13&t=228906&h=0