Exhaust Upgrade

[Funky]

The initial message was deleted from this topic on 12 November 2023 at 02:28

[Heaveho]

There are no simple answers to this. A turbo car will generally respond better to changes such as these if given a remap to take account of them. But, it depends on how good the original parts are as to what gains replacements will yield in percentage terms. Cat removal I would say is generally beneficial to most cars, if nothing else mine have tended to be better on fuel, although just the cat removal alone is said to give 15 brake on my Evo for instance.

If you have a specific car in mind, you may get more informed answers by letting us know what it is.

The noise part is easiest to comment on, any car is generally louder with an aftermarket induction and exhaust, but again, you have choices to make as to how loud you want it and can tailor this to what you feel is acceptable. I hate loud cars, mine has the type of mods you describe, but the car makes very little more noise than standard, while still giving gains.

Edited by Heaveho on Saturday 11th November 14:43

[Scrump]

My own experience is that changing the induction often leads to increased induction noise (the engine sucking in!) whilst changing (or removing ) the cat or the back box leads to increased exhaust noise (the engine blowing out).
This is not necessarily a better noise it may sound worse but louder. Different cars will respond differently to the changes and different brand of things like back boxes will lead to different changes in sound.

Whether or not changing the induction, manifolds , cat or back box will lead to a bhp increase is again dependent on the car. In theory better flowing components will let the engine breathe easier and hence make more power, it in practice most manufacturers fit components which don’t overly restrict flow so fitting an aftermarket one may not see any power increases. Often multiple parts have be fitted together to see a power increase otherwise the breathing is still restricted further along the system.
Changing many components and then getting the car remapped to take advantage of the better breathing is more likely to see a return from the new parts.

[Heaveho]

Funky said:

HeaveHo - Thank you for your answer, makes a good bit of sense! Theres a few cars i was wondering in relation to but mostly a supercharged exige and a rover elise with a Larni! The poor elise you cannot even hear it startup which i think is a shame as they are such mini supercars they should have a bit of ooomh! I love the deep sound on tickover and driving with a few pops and bangs thrown in for good measure.

Do the manifolds make much difference to loudness or is that mostly hp?


Scrump - Thanks a million, yes i get you about induction! Again the question above about the manifold, i am taking it this only relates to a small % of the noice compared to the back box and cat?

So most if not all cars need the remap for the hp gains?

Most modern stuff will only really release the potential of decent mods after a remap, as the fueling and ignition can be altered to take advantage of an engine that can breathe better. I ported the standard manifold on mine, and have always wondered if I should have bothered, as I suspect I lost torque through doing that.

There'll be lots of info for well regarded upgrades ( as well as those to be avoided ) for both of those cars, as they've been around long enough to have been developed independently. I can't profess to know much about either, some generalisations will apply to them, but there are bound to be particular upgrades that will be of specific benefit.

[stevieturbo]

Funky said:

Hi all! Just a general question. When upgrading exhaust's there seems to be 4 parts which usually give the different sounds and hp. The Induction, Manifolds, Cat and Backbox. Can anyone tell me what does what and break it down a bit for someone not mechanically minded! Kind of like the below with the % in relation to the overall gain of the full exhaust system but actually filled out right!

Induction - % hp increase / % sound increase / sound change?
Manifolds - % hp increase / % sound increase / sound change?
Cat - % hp increase / % sound increase / sound more pops and bangs for decat
Backbox - % hp increase / % sound increase / sound change?

depends
depends
depends
depends

[Funky]

stevieturbo said:

depends
depends
depends
depends

Looking for a super average guesstimate, even if just on loudness considering you want loud and where to get it from

[Haltamer]

Funky said:

Induction - % hp increase / % sound increase / sound change? - Intake sound increase only; In many cases intakes will lose power due to poor heat management or throwing off MAF Calibrations on modern cars. Be careful what you choose; Will help release turbo noise on recirc'd turbo cars.

Manifolds - % hp increase / % sound increase / sound change? - Modification options shrinking here as most cars go to headifolds. Significant impact on "Tune" of sound; Beneficial if you're going from cast logs to signing and dancing tubular headers.

Cat - % hp increase / % sound increase / sound more pops and bangs for decat - Potential for big power gains and big MOT Problems When paired with a loud exhaust, this will often just serve to make the car far too loud and massively obnoxious / smelly. Some cars can make big power from a cat change.

Backbox - % hp increase / % sound increase / sound change? - Again depends on the car, can normally net ~10HP or so here. Less worry than the intake as you're not affecting metered values, But big potential to affect the tune and volume as you'd expect. Buy from a trusted brand and leave the chopped up cherrybomb option

Impossible to give an average for these really - It will wholly depend on the car in question.

For example, on my FK8, The frontpipe (Under the engine, between cat and exhaust) is more important for power than a decat, whilst there are many cars where you can decat & gain xxxHP without doing much else.

[Heaveho]

Funky said:

Totally get you!

So the manifold itself would not do much to enhance sound? Ported? Tell me more ....

Ported means I opened up the insides of the exhaust manifold where it meets the cylinder head so that the openings were the same size and shape, rather than have a step where one meets the other. It's generally regarded as a good thing to do, but there are instances where it makes little difference. I think if the car had been running more power to start with, the porting would have been more beneficial, as the exhaust would have become more of a restriction, as it is, I probably needn't have bothered.

I'm not complaining, it's all I need for a road car as is.

[Belle427]

The K series Elise responds quite well to a 4/2/1 manifold but i wouldnt like to suggest numbers.
Some info here.
https://wiki.seloc.org/a/Category:Exhaust

[E-bmw]

Funky said:

stevieturbo said:

depends
depends
depends
depends

Looking for a super average guesstimate, even if just on loudness considering you want loud and where to get it from

As the man said, there isn't one.

Depends on so many variables there is no way to comment.

[E-bmw]

Funky said:

Only question left is the manifold, if i forgo that hwo much difference on the sound will it make? The aim is deep sound/loudness and some pops and bangs, mostly. Should skipping the manifold and only doing the decat and back box lose much?

Why on earth would you be modifying for sound?

It is very likely that doing so may well remove power/torque.

Pops & bangs don't come from exhaust tuning they come from stupid mapping to inject fuel when it isn't needed.

[GreenV8S]

Funky said:

its actually an upgrade surprise for someone

I'd be wary of that. It's obvious you have no idea what you're doing, and the questions you're asking are so vague that you aren't going to get any meaningful answer. If you're using this to plan actual modifications to a vehicle somebody cares about, there's every chance you'll spend money pointlessly, or even mess up something that was fine previously.

[Funky]

GreenV8S said:

I'd be wary of that. It's obvious you have no idea what you're doing, and the questions you're asking are so vague that you aren't going to get any meaningful answer. If you're using this to plan actual modifications to a vehicle somebody cares about, there's every chance you'll spend money pointlessly, or even mess up something that was fine previously.

Thanks i obviously framed my question completely wrong. I have spoken to the experts about the specific exhaust we are looking at, including the makers and mechanic! However i was interested in the overall question of how different parts effect a car in general, as it may not be the only car i want to change parts on to get the sound i like. Obviously it did not come across but i intentionally made it vague so i could try and gain some knowledge about the 4 main parts of a system and how they worked together and what effect it had on sound, as i am not mechanically minded myself

[Funky]

It has been years and years since i was on pistonheads and i had heard some bad stuff about it over the past couple of years and how it had changed from when there was a great community. I thought it would be a good place to learn some things i can put my hands up and say, i dont understand. Its a pity some replies where less then nice about it all

Thanks to those who actually helped without shaming, i do appreciate it

[Belle427]

If its generally Lotus based head over to Seloc and read through the various threads.
If its K series related then this is your go to.
http://www.dvapower.co.uk/

[E-bmw]

Funky said:

It has been years and years since i was on pistonheads and i had heard some bad stuff about it over the past couple of years and how it had changed from when there was a great community. I thought it would be a good place to learn some things i can put my hands up and say, i dont understand. Its a pity some replies where less then nice about it all

Thanks to those who actually helped without shaming, i do appreciate it

I think you will find if you read the replies, every one is trying to be helpful, but as you have said yourself, your questions are so wooly that we can't be specific.

Rather than expecting everyone to do all the ground work for you, you need to do some yourself & ask some more realistic/specific questions.

[the-norseman]

OP what car?

[Funky]

E-bmw said:

I think you will find if you read the replies, every one is trying to be helpful, but as you have said yourself, your questions are so wooly that we can't be specific.

Rather than expecting everyone to do all the ground work for you, you need to do some yourself & ask some more realistic/specific questions.

Honestly i dont think so. I absolutely did not want anyone to do groundwork for me ....... I was simply trying to gain extra knowledge after speaking to multiple people experts and not already. The main piece of knowledge was what does the manifold add soundwise and i still have no answer to that. Please see above where i said the following:

Funky said:

Thanks i obviously framed my question completely wrong. I have spoken to the experts about the specific exhaust we are looking at, including the makers and mechanic! However i was interested in the overall question of how different parts effect a car in general, as it may not be the only car i want to change parts on to get the sound i like. Obviously it did not come across but i intentionally made it vague so i could try and gain some knowledge about the 4 main parts of a system and how they worked together and what effect it had on sound, as i am not mechanically minded myself

[GreenV8S]

Funky said:

what does the manifold add soundwise

What sort of answer do you think it would be possible to give to such a vague question about such a complex and subjective topic?

[Funky]

GreenV8S said:

What sort of answer do you think it would be possible to give to such a vague question about such a complex and subjective topic?

Call me crazy but i have already had people tell me a rough guesstimate about the % effects of sound level of a decat and backbox, i was looking for the missing piece of the manifold and its effects. I stated all the way through its just a total vague, "what do you think" kind of answer i was looking for.

Is it ok now to stop shaming my question, despite me apologizing for not being clear enough in the beginning, or would you rather continue? As for me i am done and sorry i bothered to try pistonheads again after so many years. Obviously you need to know exactly what your talking about in great detail to be able to post questions here