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2 1/2" or 2 1/4" pipe for a custom exhaust???


weetec

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any help wether i should have 2 1/2" or 2 1/4" pipe for a custom exhaust de-cat and back which i am having made for my mb6. it has a standard manifold which i beleive is 2 1/4". the manifold is not being replaced. which size pipe am i better off with. i have been told 1 gives more power where the other gives more torque.any help?

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I personally would stick with 2"1/4 for the MB6. I have a 2"1/2 on mine and I'd say it's too big, too loud and not worth the extra size. It's more powerful than the standard for sure, but I removed the cat at the same time and I think that's made the extra difference. I'm still running standard mani too.

From what I've read, the extra size of the 2"1/2 only really shows benefit above 9000rpm - a 1.8 just won't flow enough air for it to become a restriction, so any mention of the power vs torque is purely hypothetical.

I'd recommend the 2"1/4 and a good manifold (DC Sports are well rated for the price) and you'll notice a good improvement from that.

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the issue was to determine the size as i am getting a new custom made exhaust tomorrow,and i wanted to make plans for future manifold, my budget wont really allow for a dc manifold, i have had a cheap 4 2 1 in the past from ebay and like you said i did not really notice power gains until i took the cat out, hence why im leaving standard manifold in and get the rest made up, cheers mr cake

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The standard manifold is 2" .So 2.25" exhaust will be great , going up at a 2.5 will make it loader and you will see no more power from it . To give you some sort of idea you will need to be making around 250 bhp before a 2.25" exhaust will need changing . As for 2.5" you are looking about the 330 bhp mark . if your plans are all n/a a 2.25" exhaust will be great .Rich

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appreciate your help chaps, im going in the morning to get it fitted. 325quid with de-cat pipe vat inclusive,custom built jobbi,life time guarantee. if i got the lingo right its a 2.25" (two n a quarter) is what im going for. like rich says any bigger for my use ain really worth while as im not going to seriously tune it. there also going to make the de-cat exactly the same fitting as original so i can swop it if i get mot issues. the place is called mij performance in walsall.google it 4 more info. post some pics after i get it done.cheers

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well, i have had exhaust fitted. 2.25"( 2 and a quarter). stainless steel guaranteed to the moon n back.

sounds awesome. got there @ 9am, took us an hour from manchester.back home 4 4pm. i had exhaust de-cat made so that original de-cat would go back on without any issues. this took longer than making the exhaust. 2 and a half inch was massive and as every 1 said totally uncalled for unless your running 250bhp plus. 3 weeks from now im getting a japspeed manifold 4-2-1 @ a wkd price as 1 of the chaps working at mij's place happens to know japspeed very well. great hospitality, defo use them again for the money. ended up paying £345 total all in. noticed free revs, much better acceleration response, rev tone changes at 4400rpm??? i was gonna go for the HKS drager look tail pipe but it was huge. make some noise for MIJ exhausts, walsall, google it....(youd think i own shares in the place)

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new year new year, get on the video tomorrow. you want to get a de-cat fitted then the rest of the exhaust done. the original price was £275. then to add de-cat another £50. then the fancy tailpipe end was £25, but he did it for £20. a lot of the work was getting the original cat to fit back in, for future (MOTs)all in all it worked out @ £345done. cost me £25 to get there. the mid sport is what i recommend, sounds fabuluso. performance wise defo gains, keeps spinning up,cant put power down, and ive got 215/40/16, also you can take your own tail pipe down n get them to weld it on. no catches or knocks on chassis. the other bonus is that it is welded straight to the de-cat joint, so no 1 can unscrew the back box n nab it..... right,got to justify to the Mrs that the plasmas on hold for a while...

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