Simple Cheap Exhaust Update?

[JamesRGUK]

Hi all,

I am probably going to re-do my exhaust at sometime in the future and have been mulling over some ideas.

I know there are numerous 'performance' exhausts for the DMC which are available for £800-£1000 + Install, but I wondered if anyone had ever thought of going for a more cost effective option.

Would it be possible to get a tube smith to bend 2 pieces of pipe so that you could connect them directly to the OEM manifold and loop straight round into 2 inline silencers?

Surely this would offer similar benefits to the more expensive replacement exhausts but at a fraction of the costs, I know that you can get good quality inline silencers for about £45.00eac.

Also if you utilised the original manifold the installation time would be significantly reduced.

I would be interested in people’s opinions; I think this could be a suitable option for those on a more limited budget, perhaps around £300 for the system.

My crude sketch below will give you an idea, I welcome all comments.

James.

[Chris Williams]

Is this not was Chris Hawes did?? I'm sure he can post some pics of his set up
Chris

[Dan6457]

I think this would help the sound of the car, but don't think it would do much for performance because it still has the highly restrictive and poor designed manifolds :?

[JamesRGUK]

Dan1986 Wrote:I think this would help the sound of the car, but don't think it would do much for performance because it still has the highly restrictive and poor designed manifolds :?

I used to think that was the case, but I'm not so sure that the manifolds are really that restrictive.
It's more the actual layout of the pipes which forces the two exhausts toghether in a sort of bottleneck & the old cat (if you still have one), I would be very supprised if the manifolds themselves actually restricted the flow much.

Again it's not so much trying to get the best performance, but more trying to achive similar results at a fraction of the cost.

Interesting feeback though, I'm sure they'll be more

James

[JamesRGUK]

Chris Williams Wrote:Is this not was Chris Hawes did?? I'm sure he can post some pics of his set up
Chris

Yep Chris H did originally have this set up, it was on his car when he purchased it.

I think it was mild steel and eventually lost out to the tin worm, however from what I recall aside form the corrosion problem, the actual layout was sound.

But I'll look forward to Chris chiming in.

James

[bozzzydmc]

Dan1986 Wrote:I think this would help the sound of the car, but don't think it would do much for performance because it still has the highly restrictive and poor designed manifolds :?

That is exactly the problem with the OEM manifold set up. No matter what exhaust is added to these all your really doing is making the car sound different.

I appreciate the new stainless exhausts are pricey but then with the replacement manifolds you get with this you are actually seeing some performance gains along with a nice exhaust note.

There is a lot of info on the net re exhaust design, it would be worth doing some homework before throwing chunks of cash at something that doesnt really work or takes performance away from your car.

http://www.sbdev.co.uk/Exhaust_Manifold ... ifolds.htm

Regards

Mike

[Dan6457]

Better tubular manifolds should also help improve fuel ecconomy a little bit as the engine will be more efficient.

[NickT]

Dump the original exhaust system it is constrictive and convoluted, unless you are going to put a turbo where the CAT is.

Ideally the primary pipes (ie from the cylinder head) internal diameter should be slightly larger then the exhaust port. This step acts as an anti-reversal for the flow.
The length of the primary pipe should be determined from the volume of spent exhaust gas and should be approx 0.8 * volume of swept cylinder from when exhaust valve just opens to when inlet valve just opens.
This aids 'exhaust scavenging'.
The exhaust flow is not a continuous flow of gas but are pressure pulses.

The problem with the exhaust on the D is that you haven't got that much room to work with so some bending of the pipes is necessary.
Any bend more than 45 degrees will greatly impact performance.

At the end of the day you can bung on a 'performance sounding' exhaust that sounds sporty, or you can put a designed system on to improve the efficiency.

Another note, mandrell bend pipes are the best, anything made of lopped off scaffold pipe re-welded will not aid flow as curves will always flow better than marked steps. Also, sound absorption type silencers flow better than 'baffled' types.

NickT

[Chris Hawes]

The original manifolds are restrictive as the difference between performance of the old and new system is certainly noticeable.

The original manifolds are ported incorrectly for the DeLorean PRV and you can see this upon removal.

James' approach is indeed how my old system was although there was a breather pipe bridging the two sides of the system together (same on the new system too).

The pictures of the new system when it was fitted August 2006 can be seen here (you need to be a Yahoo member to access these):-
http://autos.ph.groups.yahoo.com/group/ ... rowse/fcfc

The new system is the same setup as the old one except the original cast iron manifolds were replaced with 21" headers to help the car breath even better.

The old system lasted with me around five years (not sure how old it was when I bought the car) but when the back box broke free due to rust at Eurotech 2006 it was then I found upon my return that the system had been welded numerous times before...

[bozzzydmc]

Thanks for the great explanation Nick

Hence the need for something like these



I applaude anyone wanting to make their own system but with what you you have said and research i have done in the past, you could very well be making things worse by not coming up with a system that is correct and fit for purpose. The last thing a D needs is less performance.

[NickT]

BTW James, do you already have a CAT bypass installed ?

This is probably the cheapest mod you can make exhaust wise

NickT

[JamesRGUK]

NickT Wrote:BTW James, do you already have a CAT bypass installed ?

This is probably the cheapest mod you can make exhaust wise

NickT

Hi Nick,

Thanks for all the info, and I'm glad chris H chimed in as I know he has had both systems.

Yep I have a cat by-pass pipe.

My manifolds are ticking now anyway so if the manifolds are off for a gasget change I might as well go the whole hog.

I was just thinking out loud.

Thanks for all the info

James