mx5 mods: new exhaust?
Discussion
folks,
I have put my car (UK 1.6 1990 model) in to have a greddy turbo fitted and the suspension changed for Gaz units.
[am very excited!]
one thing that the chaps suggested was to have a sports exhaust fitted as well. it's another 350 quid but they mentioned that it would lower the back pressure and allow the turbo to spool up at lower revs, which would improve the power band over which the turbo is active.
what do you folks think? a worthwhile mod - or one that will make marginal difference?
Thoughts and advice much appreciated.
-ace
I have put my car (UK 1.6 1990 model) in to have a greddy turbo fitted and the suspension changed for Gaz units.
[am very excited!]
one thing that the chaps suggested was to have a sports exhaust fitted as well. it's another 350 quid but they mentioned that it would lower the back pressure and allow the turbo to spool up at lower revs, which would improve the power band over which the turbo is active.
what do you folks think? a worthwhile mod - or one that will make marginal difference?
Thoughts and advice much appreciated.
-ace
Hmm, judging by the noise my otherwise stock Eunos 1.6 makes, I'd say taking the cat out (£45 from mx5parts.com - and a total doddle to fit - comes with gaskets too so don't order any more) - will free it up plenty.
Totally MOT legal too, since car is a pre 92, so no need to slot the cat back in for MOT's!
Totally MOT legal too, since car is a pre 92, so no need to slot the cat back in for MOT's!
I've been told that Jap imports have different emissions requirements - such that even later Eunos' don't need the cat? Or perhaps it's that they will pass the 94- emissions test without it...
My Eunos was imported with a sports exhaust sans cat - passed all its MOTs until last November when the garage failed it on the emissions. Cue complete standard Mazda system fitted from manifold to tip including cat at 1100 quid
My Eunos was imported with a sports exhaust sans cat - passed all its MOTs until last November when the garage failed it on the emissions. Cue complete standard Mazda system fitted from manifold to tip including cat at 1100 quid
Edited by nicecupoftea on Monday 16th April 14:29
nicecupoftea said:
I've been told that Jap imports have different emissions requirements - such that even later Eunos' don't need the cat? Or perhaps it's that they will pass the 94- emissions test without it...
My Eunos was imported with a sports exhaust sans cat - passed all its MOTs until last November when the garage failed it on the emissions. Cue complete standard Mazda system fitted from manifold to tip including cat at 1100 quid
My Eunos was imported with a sports exhaust sans cat - passed all its MOTs until last November when the garage failed it on the emissions. Cue complete standard Mazda system fitted from manifold to tip including cat at 1100 quid
Edited by nicecupoftea on Monday 16th April 14:29
why on earth would you do that when there are so many cheaper, better quality options available
Reducing the back pressure will allow your turbo to spool up earlier and quicker making more power available at lower revs and reducing lag.
However, just changing the rear box will do next to nothing. You need to work from the other end.
Make sure you have a good downpipe from Turbo to cat and then replace the cat (fine on a jap import as they are rated on SVA rules not UK market rules).
The next step would be to replace the mid-pipe and back box (might as well be done at the same time).
Go for 2.5" pipes or failing that no less than 2.25". Anything less won't make a lot of difference.
Your exhaust will then be a fair bit louder but not as loud as it would be with a supercharger as the turbo itself adds a restriction.
However, just changing the rear box will do next to nothing. You need to work from the other end.
Make sure you have a good downpipe from Turbo to cat and then replace the cat (fine on a jap import as they are rated on SVA rules not UK market rules).
The next step would be to replace the mid-pipe and back box (might as well be done at the same time).
Go for 2.5" pipes or failing that no less than 2.25". Anything less won't make a lot of difference.
Your exhaust will then be a fair bit louder but not as loud as it would be with a supercharger as the turbo itself adds a restriction.
I partly disagree with you Lazza. I agree it's all about flow going backwards, but too many people have failed to see any gain, or even seen a loss with a cat replacement pipe, where as the back box is quite restrictive.
One thing though - if the car has now been remapped/tuned for the present turbo setup, then on changing exhaust components this will need redoing. The MX5 engine is strong and cheap, but it's still not worth taking the chance (ok my F/I these days is rotary (still have the '5 though) so tuning is even more critical).
One thing though - if the car has now been remapped/tuned for the present turbo setup, then on changing exhaust components this will need redoing. The MX5 engine is strong and cheap, but it's still not worth taking the chance (ok my F/I these days is rotary (still have the '5 though) so tuning is even more critical).
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