Re: [DML] Stainless Steel Exhaust Resonance

[Martin Gutkowski <webmaster@xxxx>]

Hi Kayo

> My audio system sounds great when the engine is not running. Once the engine
> is running, I have to crank up the volume several notches to override the
> cabin's resonance as the O.E.M. exhaust's resonance do interfere with the
> cabin's acoustic environment. I am anticipating the idea of the present
> audio sound quality being compromise by the new stainless steel exhaust
> system. Since the new stainless steel system is louder and it has a
> different tone then the O.E.M. system, is the noise level, as in the decibels
> with the resonance generated by this system much more louder then the average
> O.E.M. exhaust system???

First off, here's some "credentials" on which I base my reply:

I've heard both the "medium" system and the "loud" system produced by stainless exhaust,
though not when driving. The "quiet" one is designed to match the OEM exhaust note. My
friend Rich owns a non-catted Island twin turbo which is a bit loud IMO. Another friend,
Chris Hawes has a pair of "free-flowing" silencers which attach to the stock manifolds by
a pair of crossover pipes and run the length of the engine bay from front to back. These
are clearly designed to produce a deep bass note to the exhaust. My own car with OEM
system suffered from severe road and engine noise when I first got it running. Leaky
manifold gaskets didn't help and neither did the accumulator access hole to the rear of
the centre console which only some cars posess.

On my own car, I have now fixed the manifold gaskets, plugged the accumulator access hole
and replaced the cat with Ed Uding's bypass pipe (www.dmc-service.nl). I also spent $105
on a box of Dynamat Extreme from eBay and covered the interior of the rear of the car
plus centre console - if this is not something you've tried, I highly recommend it. I can
hear my engine still, but I can't *feel* it if you know what I mean. I get more noise
from my doors now than I do from the whole of the rear of the car. I'll be dismantling
the doors for a complete rebuild later this year, and will add some dynamat to them then
(it'll make a neat replacement for the original plastic liner).

As to the note of the Stainless systems - they are much more "european" in sound than the
Island kit. If you ever hear a Ferrari in full song, you'll notice it doesn't sound
particularly bass-ey except at idle, but more of a high pitched rasp when revved. The
medium system sounds like this, only clearly not quite as "big" :-) At idle it's about
the same as an OEM system. The Loud system is impractical for road use - it's basically
an echo chamber, and you need earplugs if standing behind it. It too is more raspy than
bass-ey. Chris Hawes' system is, in my opinion, awful (sorry Chris!). It encroaches on
the cabin waaay too much and it's hard to have a conversation if the revs have settled at
a certain resonant point. The Island turbos are better, though about as loud - from this
I guess that it depends on where the silencers are mounted - The Island kit's "shoe
boxes" are right at the back of the car, as is the stock back box and therefore
stainless-exhaust's system.

So in summary, the new system should be quieter at revs because it doesn't produce as
much bass. This is only my guess, but I think you'd have excellent results with the
Dynamat, as I did with the stock system. There're some photos of my Dynamatted interior
(and new rear speakers) here.

www.delorean.co.uk/1458and2727d.html

Also, for those who haven't read about it yet, the page on the free-flow stainless
exhaust system for the DeLorean is here

www.delorean.co.uk/exhaustmod.html

Best Wishes

Martin
#1458
#4426
(DOC UK)