43 replies to this topic

[Skortchio]

I think a 5+bhp power difference will be noticed. After all, most people fitting a so-called 'Stage 1' kit will gain about that much extra and say they notice the difference.

More than likely it will prove to be an increase in power from his current (3" Playmini).

Not to drift off topic again but the 5ish bhp loss compared to an RC40 in KC's testing was based on a budget 2" full system, not a 1.75" silencer with 2 end tips.

[Mini_Magic]

I think it's more a psychological thing. I've got both a standard backbox and a twin pipe system for my Mini and I can't feel a difference in performance. If your on a race track or something then it will be noticeable on your lap times. Just my opinion on the subject.

[Cooperman]

I think a 5+bhp power difference will be noticed. After all, most people fitting a so-called 'Stage 1' kit will gain about that much extra and say they notice the difference.

More than likely it will prove to be an increase in power from his current (3" Playmini).

Not to drift off topic again but the 5ish bhp loss compared to an RC40 in KC's testing was based on a budget 2" full system, not a 1.75" silencer with 2 end tips.

But the overall result is the same. If larger tail pipes were better then race and rally cars would all have them, including F1 cars. My son works in F1 and WRC design and he says that the exhaust systems must remain the same diameter and be the correct diameter for their full length.
I'm not going to argue this point any further as it's a bit tiresome to keep on repeating the basic design criteria for performance exhausts. Why anyone would want a larger tail pipe, lose power and make much more noise is quite beyond logic, unless it's to say "Look at me, I've got a noisy car and that makes me ace". Well, it doesn't, it just sounds anti-social. Sorry if that offends anyone and it does not mean that the sound of a good proper performane exhaust is in any way bad.

[oltonlad]

I think a 5+bhp power difference will be noticed. After all, most people fitting a so-called 'Stage 1' kit will gain about that much extra and say they notice the difference.

More than likely it will prove to be an increase in power from his current (3" Playmini).

Not to drift off topic again but the 5ish bhp loss compared to an RC40 in KC's testing was based on a budget 2" full system, not a 1.75" silencer with 2 end tips.

But the overall result is the same. If larger tail pipes were better then race and rally cars would all have them, including F1 cars. My son works in F1 and WRC design and he says that the exhaust systems must remain the same diameter and be the correct diameter for their full length.
I'm not going to argue this point any further as it's a bit tiresome to keep on repeating the basic design criteria for performance exhausts. Why anyone would want a larger tail pipe, lose power and make much more noise is quite beyond logic, unless it's to say "Look at me, I've got a noisy car and that makes me ace". Well, it doesn't, it just sounds anti-social. Sorry if that offends anyone and it does not mean that the sound of a good proper performane exhaust is in any way bad.

i agree, just let them get on with what they want, i really dont understand why people put posts up to ask advice..............than ignore the advice that they are given, these guys obviously know a lot more than vizard does............... .

[minimarco]

I think APEX designs exhaust systems (for R34 GTR's) that are made so the diameter changes gradually though the system. Not like going from sections to bigger sections but the pipes are made so its a cone shape. They attribute it to sound waves influencing the exhaust gas to exit quicker.

I've always been skeptical about that, sounds like a gimmick, but it does sound interesting. They had figures to prove increased performance, but it's their own test.

I also wonder if the consistent diameter exhaust used in F1 and WRC is an FIA rule. And if not, if they've done tests with cone shaped exhaust systems. Though it would be difficult to make a manifold like that for v10-v8s.

[minimarco]

Also, I think to further explain this instead of using a spray gun example(where paint is forcefully pushed out), a better example would be a straw(where you want to promote suction, not only pushing force to move gases). water travels out a straight tube easiest with the least amount of turbulence. You wouldnt want to drink out of a straw with a tapered end. Designers have to think not only about expelling gases efficiently but a shape that will draw it out instead of solely relying on the engine to push it out. If the tube is not straight, then it looses the advantage of the negative pressure in the atmosphere to draw exhaust out. a bigger end or change in shape would theoretically diminish that effect.

p.s. I dont know anything about physics and have not studied it. I'm only using logic and common sense.

Edited by minimarco, 25 July 2012 - 08:17 PM.

[Skortchio]

The result may be the same but markedly reduced in this scenerio, without testing it's unknown how much by but if a whole oversized system causes 5bhp then only 5% of the system being oversized would, logically, cause a much reduced loss.

In this case the larger tip and it's increase in cross sectional area is more akin to shortening the total exhaust length than the suggested it equals fitting a full length large bore system.

F1 cars spend a large portion of their time at high rpm exploiting the enormous bhp they have.

Road cars don't. They spend a majority of the time in stop start driving. low in the rev range far below peak power. Torque plays a larger role in the percieved performance of the vehicle on the road, not to mention that asthetics and audio enjoyment may or may not play a larger role than potential bhp which only comes of use on rare occasion.
How often is a road car driven at max power aside from on motorways where aerodynamics will play a large role in the speed attained.

i agree, just let them get on with what they want, i really dont understand why people put posts up to ask advice..............than ignore the advice that they are given, these guys obviously know a lot more than vizard does............... .

The posted question was nothing to do with optimum performance, only the difference between a budget 3" exhaust and Maniflow.
No one has suggested they know more than anyone, Vizard hasn't even been mentioned thus far.

I think the crossed lines here are that the OP was asking for comparison between 2 sub optimal exhausts and the thread lost track and ended up debating the potential power losses against an RC40. Even then there was miscommunication as the study shown was on full systems both 1.75" and 2", not the end section only.

I don't think anyone will contest that a side exit, twin box, RC40 is the best option for the Mini. But that is far removed from what was asked, not to mention that the difference of opinion was mostly down to apparent misunderstanding in what was being said.

/hugs

Edited by Skortchio, 25 July 2012 - 08:24 PM.

[konyo]

I think a 5+bhp power difference will be noticed. After all, most people fitting a so-called 'Stage 1' kit will gain about that much extra and say they notice the difference.

You can notice the difference I did anyway?

[mingy]

Contact Maniflow for an unbiased and experienced answer to this question, DV used maniflow to good effects on his test engines.
I gave them my engine specifications and it,s planned use and they were more than helpful in providing me with the optimum exhaust specifications needed for as near as dammit perfect gas flow removal.
I would accept Coopermans theory is, as good as you could get.
But at the end of the day us older chappies are probably a bit more traditional than you young uns.
Try two clothes pegs and a couple of Brooke Bond PG Tips cards clipped to your back wheels for a sporty effect ( This one,s for Cooperman !!!!!!!).

[Cooperman]

Try two clothes pegs and a couple of Brooke Bond PG Tips cards clipped to your back wheels for a sporty effect ( This one,s for Cooperman !!!!!!!).

We used to do that on our push bikes when we were all 11 or 12. Remember it well!
I still can't understand why anyone wants to make their car noisier and just draw attention to themselves for no real reason. It's a 'logic-free-concept'.
It seems that the science of exhaust gas flow velocities is still not being grasped by some, so I'll just leave it there and those who want to believe their own theories rather than the true physics can do so in peace. They clearly know so much more than the likes of Keith C., Vizard, etc.

Edited by Cooperman, 25 July 2012 - 11:03 PM.

[Skortchio]

It seems that the science of exhaust gas flow velocities is still not being grasped by some, so I'll just leave it there and those who want to believe their own theories rather than the true physics can do so in peace. They clearly know so much more than the likes of Keith C., Vizard, etc.

The science is grasped without difficulty and hasn't been questioned.
The difference of the effect of end tips alone upon those velocities is what has been debated and as far as I can summise misinterpretted. Because the presented material only relates to full overbore systems and not tail tip changes, and thus far no data has been made available on the documented differences of those alone. However if a full system gave a, for example 5bhp difference. Then it is fair assumtion that a smaller change in the set up, would then manifest a smaller difference also. No?

No one, and I assume you mean me, has suggested they know more than Vizard / Carver in tuning or performance engineering. All I have done is considered that the differences in exhaust tip choices only, would cause a smaller variation in power than those found in comparing entire exhaust systems, based upon the information given. The report by KC.

Why the discussion of potential power variance based on alterations in the exhaust system has become what is now feeling like a personally directed condescension, I do not know. But for whatever reason you feel I've offended you, I apologise.

My intention was only to confirm how much variation was caused by a change in exhaust end tip, as a whole 2" system falls short of an RC40 by approx 5bhp, I have my answer that a twin tip over single on the end of an RC40 would yield a smaller loss.

[Jakeclubby]

Got to be honest i like the sound and look of the twin dtm end and i only use my car for short journeys and never really rag it so i think ill have one.....

[EngineerDaisy]

Try two clothes pegs and a couple of Brooke Bond PG Tips cards clipped to your back wheels for a sporty effect ( This one,s for Cooperman !!!!!!!).

We used to do that on our push bikes when we were all 11 or 12. Remember it well!
I still can't understand why anyone wants to make their car noisier and just draw attention to themselves for no real reason. It's a 'logic-free-concept'.
It seems that the science of exhaust gas flow velocities is still not being grasped by some, so I'll just leave it there and those who want to believe their own theories rather than the true physics can do so in peace. They clearly know so much more than the likes of Keith C., Vizard, etc.

Why would you want to put something in your bike wheel that causes it to (kinda) sound like a motorbike when moving when it would create (albeit a tiny fraction) extra friction on a vehicle that you are personally powering......because it sounded good to you at the time. Not everyone wants to eek out every last bhp and mpg out of there cars. Some people like them to sound nice or raspy or what ever sound they get from there exhaust. Maybe drawing attention to yourself when driving a mini isnt a bad thing these days. There are so many cars that are way bigger and many people who arent all there when at the wheel that i personally would rather have a loud mini and have people realise i was there than get squished....if it means i get less performance so be it :) as the bikers say loud pipes save lives :) Me personally i will be ditching the side exit rc40 off my mini for a side exit DTM because i like the look and have wanted one for years :)

[Mini_Magic]

Exactly, the sound my twin exhaust system makes is worth the minuscule loss in power (if there is any, I can't even tell).