Sportier Sound

[karlj0]

Hi Chaps
I was wondering if there was a low cost way of making my 95' 968 Sport sound a bit throatier without spending a fortune. Im happy with the performance but the standard sound at tickover doesnt sound much different to my girlfriends fiesta. I dont really want to have to start making major mods etc but wondered what the basic options were to make it sound more like the sports car it is.
Any suggestions would be most welcome.
Cheers
Karl.

 

[timward]

the first (and only) mod i made to my 968 cab was to replace the exhaust with a janspeed back box courtesy of promax motorsport. like you i was totally underwhelmed by the sound of the original and when the baffles went it was a cost-effective solution; note a replacement porsche exhaust is well over a grand + vat, whereas a decent stainless sports exhaust can be had for under £400. makes the car sound like it should. suggest you visit the promax site. my janspeed was an early model with a round exhaust tip which i'm unhappy with, but replacing it is too much of a hassle. later boxes should have the correct oval tailpipe. i cant fault the sound
regards
tim
p.s dont be tempted to change the air filter. teh combination of new filter + new exhaust proved too loud and boomy. dont ask me why but returning to the standard air filter calmed the sound down and now its just right

 

[chfs911]

I got a custom stainless exhaust from 968 specialist in Falkirk. The performance figures were up 14bhp.

Pm for details. It was only £400 cat back. Cutoff oval tailpipe is very close to original.

http://www.stainless-creations.co.uk/images/Work%20233a.jpg

 

[frogisland]

Hope you are keeping well.

14bhp

Was that quoted numbers or actual?

I'm aware of someone whom has undertaken quite a quest to obtain more n/a power out of a 968; heads, cams, mapping, throttle body, exhaust etc etc only to gain 25bhp! I know he would just love to get one of those exhausts. Also, having seen his dyno charts, exhaust changes have quite a profound change on torque and power, especially, mid section, cat and headers (combinations of and in isolation).

Still lurking,

JP

 

[chfs911]

It was with new sports cat.

I have calculated the torque figures from the rolling road graph and found no change upto 3500 rpm, but worth while gains from 4k upwards.

Torque = (BHP X 5252) / RPM

At 4k we measured 190 lbs/ft which was a gain of 10 lbs/ft, 4.5k was 189 up by 7, 5k was 188 up by 14, 5.5k was 186 up by 13, 6k was 175 up by 10, and 6.5k was 166 lbs/ft with a gain of 8 lbs/ft.

As expected the gains were higher up the rev range.

Sounds nice too!

 

[Slippers]

The "airbox mod" also makes the engine sound more throaty, and a US site measured it as giving +11bhp over the standard setup (with a K&N filter). I've not put my car on a rolling road since the airbox was changed (or ever, actually!), but it feels and sounds faster - again, though, only higher up the rev range. These cars were meant to be revved!

So this car only hit 205bhp at maximum power?

 

[chfs911]

I dyno'd the car at AVA in Glasgow and got a steady increase from 4k, 137 to 144, 4.5k was 155 to 161, 5k was 166 to 179, 5.5k was 181 to 195, 6k was 189 to 200, and 6.5k was 195 to 205 bhp at the wheels.

 

[Big Dave]

Slippers.
If you notice, the figures he has quoted are at THE WHEELS..
Most [factory],are flywheel figures.
I think rule of thumb is a 15% loss from fly to wheels... But it maybe more....

 

[frogisland]

I'm quite surprised at your results (but hasten to add not doubting) - it appears quite a challenge to get good results from exhaust changes on these cars, and can sometimes result in lower power/torque. I came across a car with exhaust, promax chip and airbox mod producing 250 bhp, and strong torque gains across the curve. I have an aftermarket exhaust plus 100 cell cat - never been particularly happy with it, and i am sure i lose torque for power gain. Have changed the cat back to the standard and (by the seat of the pants) felt as though it pulled better mid range!

JP

 

[Slippers]

ORIGINAL: chfs911

I dyno'd the car at AVA in Glasgow and got a steady increase from 4k, 137 to 144, 4.5k was 155 to 161, 5k was 166 to 179, 5.5k was 181 to 195, 6k was 189 to 200, and 6.5k was 195 to 205 bhp at the wheels.

Ah, at the wheels. As Big Dave points out, this explains it. The factory stats are of course from the other side of the flywheel...

 

[Mr968]

I think I am right in saying that exhaust ' tuners' are able to tune an exhaust along a scale dependent on tube lengths, headers, tube diameters, resonance, scavenging, heat dissipation etc. etc.
The scale(all other things being equal) being between bhp and torque, so if you do change the exhaust be prepared to sacrifice something!
In terms of performance, Porsche did their best to compromise midrange torque with high mph, while keeping emissions and sound levels down for normal street use.

 

[karlj0]

Thanks for your responses guys.
Dont really have a budget for much at the moment with arrival of baby boy last month. But quite interested in the airbox upgrade if that gets me a slightly better sound without spending too much or tampering with the exhaust. Where do i find out more info, prices etc ?
PS im not looking for a boy racer yobbo sound, just a nice revvy note that might sound good through the tunnels en-route to Le Mans 09. Cheers Karl.

 

[Red 3]

just a nice revvy note that might sound good through the tunnels en-route to Le Mans 09.

I take it we're going then.........Wahey!!!

 

[saintsimes]

On airbox upgrade/mods, there seems to be info around on putting holes in the front of the box to increase airflow, but not much about putting holes in the bottom. It would need holes in that thin plastic sheet underneath as well, but looks like that would allow extra cold air in from in front of the radiator, rather than the warm air around the front of the box. Does anyone have experience of this?

Note that I think someone mentioned the holes in the front of the box plus K&N filter can be too noisy (or maybe generates a boom sound), any comments?

 

[Mr968]

there have been many people saying that the holes in the front of the airbox is a good way to allow the intake to breathe better by allowing the incoming air to utilise more of the area of the air filter with less restriction, especially when teh air filter starts to get clogged with dust and flys etc., making the hole/s under the airbox in front of the radiator is a natural progression to utilise cold air rather than potentially warm air from the engine bay.
At any sort of speed it may not make any difference though as the ambient air in the engine bay is being changed constantly by airflow. Then again the airbox is sat on top of the radiator so placing the holes under the airbox may tip the balance in terms of air temperature getting into the engine.

 

[Big Dave]

I have an article all about this. When i find it ill post it....

 

[Big Dave]

Here you go. A bit of "bedtime" reading....

http://www.968engineering.com/pdfs/airboxmods.pdf

And

http://www.968engineering.com/pdfs/968%20air%20box%20flow%20modifications.pdf

 

[karlj0]

Thanks for the link.
That airbox mod looks very interesting indeed. Has anybody done it yet on here?
One thing im still trying to fathom out though (call me stupid). Is it purely a matter of putting these four holes in (as in the 2nd link) or is there lots of other fiddly stuff to do as mentioned in the first PDF ?

Cheers
Karl.

 

[Big Dave]

Hi.
Yes ive just done it to my "spare" airbox.
Cant realy tell you what difference it made, as i havnt had the car out since...
It is as easy as drilling out the box + hot glueing in the "port" tubes...
Just follow the info...Remove the snorkel + the thin rubber gasket at the front of the car ...
You have to cut the port tubes down...[Available from Maplins]... £1.90 each..
Its a cheap mod...

 

[Neil Haughey]

Hi Dave I will be interested to hear if it makes the car any noisier at cruising speeds or on part throttle daily driver stuff. I would prefer to keep that stuff as is, but if it gives a nicer growl on WOT then it sounds like a fantastic mod especially if the power claims are to be believed. That doc claims its as good as a chip but is cheaper still.

TBH IMHE sportier sounding exhausts is a bit of a phase you go through. I removed the cat from my S2 several years back and replaced with a just a straight section of SS pipe. It sounds great above 4K rpm when really on it but TBH is a bit of a pain when just trying to get from A to B at normal speeds because there is a constant drone that you don't get with a stock system. I quite like the balance of the stock 968 system actually, it has a nicer deeper sound and a better roar above 4K rpm then the stock S2 system but manages to not be intrusive at motorway speeds. Maybe I am in the minority but I think Porsche got it just about right.