another exhaust thread - top gear 200 cell cats difference

[Phil 997]

opcorn:

Osh

Hi Osh, Guess you knew I would pipe up eventually :grin: how are you getting on with options did you go to Wales to hear the dansk's 8)

Hi Phil

i'm really well but haven't had the time, yet, to do the upgrades on my car. Been massively busy at work and not enough hours in the day to get things done.

She's going in in two weeks time to have the front bumper and wing done that the neighbour scratched before Chrimbo. And then i've got a whole host of mods to do over the next few months.

Hopefully have the exhaust sorted over that period, too.


Osh

Osh,
So your the one that's working hard, I had heard a rumour that some people still did :floor: It will be good to get the paintwork sorted and then MODS through the summer if your planning to do Simply Porsche at Beaulieu on 5th June I will catch up with you there :thumb:

 

[Phil 997]

I have also done the gt3 throttle body and plenum upgrade you will need a remap with it so choose you mapper carefully based on rep. Its a very good mod and makes a big difference to the power and way the car breaths and performs, more air in more gas out equals more power, Its the next performance mod to do after the exhaust. Have you already done the induction pipe and BMC filter upgrade. :thumb: :grin:

I'm always a bit skeptical with claims of big improvements on a naturally aspirated engine's power from just induction and exhaust mods.

What I've typically found in the past is that the standard induction on sports cars, despite often looking restrictive, is actually more than adequate even at moderately increased power levels. For example, the tiny airbox on the 290 bhp Evo VIII was retained on the 400 bhp tuner produced Evo VIII FQ-400, i.e. the standard induction could provide enough air for a 40% increase in power.

You find the same with many other forced induction models - puny looking inductions are easily capable of supporting 10%+ more power.

Seems to me that most of the claimed gains from aftermarket induction kits (at least those that aren't completely made up!) are from the kit changing the airflow and tricking the car's air sensor into believing less air is flowing than really is. The ECU therefore leans out the AFR and this is where power gains are obtained - from leaning out the fuel mixture, something that could be done with a remap and leaving the standard induction in place.

My history with fitting aftermarket exhausts to big engined NA cars (4.0L M3, 5.2L S6) is even worse - at best there is no power increase, at worst you actually lose power.

Getting back to fitting the GT3 throttle body, the GT3 engine is chalk and cheese to the 996.1 engine, not just in capacity, but cooling method, materials used and rev limit. I struggle to believe that bolting on one fairly minor part from it can lead to any substantial gains.

You are of course entitled to you opinion and that's how we all obtain a fair view of things and performance gains are one of those personal subjective things.
To a track orientated guy 25/30 bhp is hardly worth having and a good driving course could give you skills that would be worth more than 25 bhp on the track.
But to a road driver 25/30 bhp mostly in the usable part of the power curve is very noticeable and adds greatly to the smile factor, it's not how much gain its very much where in the curve it is.
60 bhp all top end would hardly benefit a road driver at all and he would be better off with 30 bhp in the lower mid range.
I have added the full exhaust induction, throttle body and remap and I estimate supported by DMS who did the remap 25 to 30 bhp gain total but its mostly in the lower mid range so it makes the car much more responsive and fun to drive.
It also feels like it breathes more freely, and the weight difference between a stainless set up and the steel original alone will make the car lighter therefore faster with the same BHP.
I am sure if the regular filters, cats etc were as good as it got ,the racing teams wouldn't use BMC or K&N Induction etc and as they have the re-sauces to know what will work then I am inclined to believe them.
Of course everything has a price and some would think spending £3k to get 25BHP not cost effective as a supercharger would be the answer but if you want a bit more poke but keep the car road usable and can afford 3k then why not.
Yes for the track spending 8k to get 100 bhp more from a supercharger would make sense but not really for my daily driver. As I say I have actually done these mods to my 997 and can tell you without any doubt it makes a difference to the performance and sound of the car.
In some respects you are correct and the mods are a combination of reduced weight , adjusting (fooling) the ECU , improving air flow in and exhaust gasses out.
The gains are not all added up so its not 20bhp for the remap 18bhp for the exhaust , 15bhp for the throttle body plenum, and 5bhp for the induction kit and sports filter. total 58 bhp it doesn't work like that as it's adding in difference parts of the band. so you cannot just assume you now have 413 bhp from your stock 355 BHP engine.
I hope that has clarified some points :thumb:

 

[Phil 997]

Have you already done the induction pipe and BMC filter upgrade. :thumb: :grin:

I havn't followed up on any of these mods as soon as I started reading about MAF fouling with non standard panel filters. Figured it was a can of worms that didn't need opened

Other forums have also talked about an 'orange cap mod' which looks to be the poor mans version of the induction pipe but only results in a little intake noise. I was planned to address it all from the exhaust

I take it you'd honestly recommend induction and BMC


Back on the topic of cats a call to topgear is in order. The x-pipe would want to be right at nearly double the cost. Or a full kline setup? yes please :thumbs:

The induction set up is interesting as I along with many were sceptical of what a bit of silicone hose would do :?: regarding the sports filters this is what happened in my case.
first attempt got a K&N filter and as many said it killed my Maff so new maff £130 and back to stock filter.
second attempt called pipercross tech support as they do a foam type filter to see if they also use oil on the filters the reply was yes they do but you can special order a non oiled one takes a week from the factory so that's what I did fitted it and it breathed nicely more air flowed etc like the K&N but there was no induction howl :nooo: it was the same sound as the stock filter but with the better breathing of the sports filter (some would say that was perfect) but I liked the howl so I lived with it so a few months.
third attempt , knowing I had a fall back position to the pipercross after more research I found the BMC use far less oil than K&N and there filters are more highly regarded so I fitted one of those the nice howl returned everything was great and I have stayed with BMC since with no maff issues, I don't ever reoil the filter I class it as a disposable item and buy a new one every time. improving the air in as well as the exhaust gasses out seems logical and for me it has worked.
The silicon pipe and resonator cap are only cheap don't do any harm, add to the howl maybe improve the air flow so why not :thumb:
Personally after much reading and research I came to the conclusion that the stock cold air intake box was hard to beat without spending £1500 on a used X51 carbon airbox or maybe £500 on a used gen 2 twin intake airbox, but with mods needed to the deck lid to accommodate twin intake the gains seemed low as the stock airbox had the ability to take more air but the stock filter was reducing it from happening. all the other options fabspeed etc cone type could not isolate only cold air and allowed warm air seep from the engine to filter in so that was not an option for me, although some will say they work great again each to there own and that's the nice thing about forums there are lots of different opinions and that's great as everyone is looking for different results.

 

[youngsyr]

Of course everything has a price and some would think spending £3k to get 25BHP not cost effective as a supercharger would be the answer but if you want a bit more poke but keep the car road usable and can afford 3k then why not.

My point is that I think you'll struggle to get even 25 bhp from those modifications, mainly because with the X50 package that was specifically designed to increase engine performance, Porsche themselves only got 25 bhp from the following:

- modified cylinder heads,
- uprated camshafts,
- improved exhaust manifolds,
- ECU remap, and
- aluminium-intake system.

I'm willing to bet that the bulk of the power increase in the X50 package comes from the engine modifications (camshafts and cylinder head).

 

[Phil 997]

Of course everything has a price and some would think spending £3k to get 25BHP not cost effective as a supercharger would be the answer but if you want a bit more poke but keep the car road usable and can afford 3k then why not.

My point is that I think you'll struggle to get even 25 bhp from those modifications, mainly because with the X50 package that was specifically designed to increase engine performance, Porsche themselves only got 25 bhp from the following:

- modified cylinder heads,
- uprated camshafts,
- improved exhaust manifolds,
- ECU remap, and
- aluminium-intake system.

I'm willing to bet that the bulk of the power increase in the X50 package comes from the engine modifications (camshafts and cylinder head).

DMS in Southampton do not have the same view as you, Porsche have to be very careful that they comply with world wide emission regs that vary hugely from region to region, so they have to come up with an engine that is compromised on what they really would like to offer in order to be compliant.
They also in addition have to make the entry level cars not compete with the more expensive options. So in order to do this they restrict a number of items across the car.
The aftermarket sector does not need to be compliant to the worst case scenario so can offer upgrades for example in the UK our legistation is very different to parts of the USA Califonia etc. so UK aftermarket companies can do things that would be fine for the car and improve the performance but would fail tests in California etc.
This is why these cars are never optimum and always compromised because they have to suit a great range of different legislation, a prime example is the new 991.2 it has lost most of the things that made the 911 such an iconic car, but they have to comply so the car is seriously compromised and Porsche would never have produced a 911 like this had they had any alternative.
So I can see how small batch custom pieces can be more performance enhancing than mass produced compromised to fit all legislation pieces. This is also why the X51 kit and the like are good but not perfect as Porsche still had to comply with legislation, so all they really did was tweak the existing engine, which is exactly what the aftermarket does.
If Porsche did not have to tailor the engine to the most restrictive legislation and to NOT make the C2S out perform the GTS gt3 etc they would produce a very different vehicle and would adopt many of the options used by the aftermarket sector. Why would you spend 25k more on a GTS if the C2S did the same, so they have to restrict the cheaper cars to allow them to command premium money for the flagship models. some of the easiest ways to restrict an engine is reduce induction air flow reduce exhaust out flow and modify the maps amongst other things.
Why do Porsche not put a lightweight stainless steel exhaust on their cars from the factory and knock lots of weight off the cars why do they use heavy steel systems :dont know: .
This is always a difficult subject as there will always be differing opinions and you fall into one camp or another all I can tell you is What I have done has worked for me and exceeded my expectations this is not theory this is FACT ,I have actually done these mods and know what the car was like before and after each mod so I can confidently state my case.
SURE THERE ARE REASONS NOT TO MODIFY A CAR, warranty is the prime one and also why spend 3or4k on things that change an already great car that has outstanding performance that are more than most people need any way.
And the only answers I can give you is" BECAUSE I CAN " and I enjoy researching and doing these things.
Do I need too NO .
Is the car fantastic without the mods YES.
Is it more fun than golf "bloody hell yea".

:grin: :thumb: :thumbs:

 

[youngsyr]

Fair enough, obviously opinions will differ, but let me elaborate a little on mine and perhaps answer one or two of your queries.

First of all, mild steel exhausts and their use by manufacturers. For me, this is purely a cost/benefit decision. At best you can save 15 kgs by using stainless instead of mild steel exhausts, which (remembering that it's on the lowest point of the car) offers as near as zero performance benefit - do you notice any performance difference between having a full or empty fuel tank?This is about 4x the weight differential than stainless vs mild.

However there are noticeable downsides to stainless systems - cost and greater noise (less mass = less material available to absorb sound).

Now onto needing to tailor to different legislative markets - the strictest market in the world for car engines is California, both in terms of extent and frequency of testing. Typically European and Japanese sports cars aren't designed (and wouldn't meet) Californian test standards, but cars destined to be sold anywhere in the American market are.

For example, Mitsubishi developed particular engine and exhaust modifications (less aggressive camshaft profiles and a second cat) specifically for the American version of their Evos, which didn't feature on the JDM or UK versions of the car. Mazda did something very similar with the MX-5. This is why "JDM" is such a big thing in the American tuning world - Japanese versions of the cars sold in the US are typically more powerful.

There is also US legislation about crash beams etc that have in the past even altered the way US models look compared to models in the rest of the world.

To sum up, I don't buy your point that Porsche design their cars to the "lowest common denominator" market as manufacturers typically tailor their cars to the individual market.

I completely understand and agree with your point about manufacturers deliberately limiting a car's power output for marketing reasons, I've seen it time and time again, particularly with Audis, where identical engines are reported to produce different power outputs, with the more expensive car's engine always producing more.

However, I keep coming back to the same point though - why would Porsche redesign and fit camshafts and cylinder heads to get 25 bhp out of the X50 package, if simple (and significantly cheaper) bolt on induction and exhaust parts will do the same job? It simply doesn't make any sense on any level.

 

[Phil 997]

I do understand and appreciate your views and as you say we are at different ends of the argument on mods.
All I can tell you is that the performance gains in the areas of the power curve I mostly use which are low to mid are real and noticeable and add to my enjoyment of my car.
I recommend these mods because it worked for me, but always point out that one persons good is not always the same as the next persons.
I do also understand that to a purist my car would give them a heart attack and they may drop a sandal or two at the sight of what I have done :grin:
but I enjoy doing these things and some will want the feedback I have to offer. And if someone enjoys as I do personalising cars then if I can suggest what IMO works and what doesn't and they can avoid spending money on some of the things that didn't work that I did and are now cluttering my garage then that's good.
So each to there own and it's always good for others to read all the opinions and views on a given subject, that's what makes these forums work, most of the things I have done to the car were things that were discussed on this and similar forums and I formulated my opinion from the points in the discussion. Some I have done , some I intend to do and others I don't think will work for me ,and that's great and how it should be between enthusiasts sharing info.
Hopefully we will catch up at one or another of the events this year :thumb:

 

[youngsyr]

Good stuff. :thumb:

When you say the gains are real and noticeable - have you tested this on a dyno?

I know from experience that louder exhausts make a car seem faster, as does lowering the suspension or putting in stiffer bushes. :drive:

Unfortunately though human beings do not make great objective testers and many mods that are very common do not actually offer their quoted improvements when objectively tested on a dyno.

 

[Phil 997]

Good stuff. :thumb:

When you say the gains are real and noticeable - have you tested this on a dyno?

I know from experience that louder exhausts make a car seem faster, as does lowering the suspension or putting in stiffer bushes. :drive:

Unfortunately though human beings do not make great objective testers and many mods that are very common do not actually offer their quoted improvements when objectively tested on a dyno.

You are right the butt dyno as the yanks call it does make things seem better. but I did each mod one at a time and the car was lowered before the exhaust and throttle body and each thing made a difference some more than others. I remapped the car then had to go back for a modified version after I fitted the throttle body plenum etc. I did not bother with a dyno as I was already into the mods before the remap and chance to dyno and as it was 8 years old I have no idea what it was producing before the mods so there wasn't really a comparator. Had I set out with the intention of doing all these things I would have got it dynoed at the start, but as with many people it just grew from ideas I got from the forums etc. and as things were working I looked at other things to do. I have found that adding stripes does not make it go faster so they were removed :floor:
:grin: :thumb: