Tubular exhaust manifolds.

[The Original Tom]

Currently running standard range rover cast headers, with 1 clamp-on down-pipe (i.e 4-1).
After the y-piece the exhaust turns into a 2.5 petrol rear section. It's not that mush smaller because with some grooves cut it slots just inside the V8 pipe.
How much difference would tubular headers actually make? Will it be worth the money to get some.
As it's in a heavy Land Rover I'm after low-end torque, so would a 4-1 or a 4-2-1 be better?
I know running RV8 without much exhaust will fry the valves, but are the tubular headers and 2 straight pipes (1 for each side) terminating in a cherry-bomb style muffler be enough back-pressure for scavenging?

Cheers
Tom

[ramon alban]

How much difference would tubular headers actually make? Will it be worth the money to get some.
As it's in a heavy Land Rover I'm after low-end torque, so would a 4-1 or a 4-2-1 be better?Tom

Tom, you may find some of the answers here:

http://www.vintagemodelairplane.com/pag ... ust01.html

Ramon
http://www.vintagemodelairplane.com

[The Original Tom]

Very interesting read Ramon cheers!
So by what you say, I need manifolds with long primarys and narrow tubes (say 2" primarys?).
Do you know whether it's best to feed them into 2 then 1, or straight to 4? I'm more tempted by a straight 4-1 because there's lesss plumbing to seal!
From what you write about interfarance, it would seem that 2 straight pipes would do the job better, and fit some kind of absorption silencer to each pipe (I like the rrroooaaarrr!).
Would 2.5" be a good bore for the secondary pipes?

EDIT: Something like this?
http://www.v8tuner.co.uk/product.php?id=476
Then 2 straight rear sections that bend on the muffler and exit just before the rear wheels.

Cheers
Tom.

[kiwicar]

On a v8 with the firing order of a rover you want a 4 into 1. A 4:2:1 is for a flat plane crank (4 cyl or 8 cyl). Most recon for a reasonable tune 5.7 chevy 1 and 5/8 bore is about right so 2" is way too big for 3.5 rover. try around 1 1/4" o bore primarys. The best set up is meant to be a 4 into 1 into a twin system with a ballance pipe between the two sides as close to the collectors as possable, this ballance pipe can be anysize provided it is bigger than a primary pipe. 2.5 straight through system is again big but will work. Might be easier to package a 2 inch system though and get silencers for it. There are many headers about, I had a set of headerman from RS worked well on a range rover with a 3.5 in it, they were about £135 about 10 years ago so the ones you found seem a good price. you would do well to try and find a set made for your application though as it would be a pain to buy them and then have to cut and shut to fit.
Mike

[katanaman]

I cant fault 99% of what kiwicar is saying but he is wrong on the 4-2-1 not being for a rover v8 and only for flat cranks. SD1 had 4-2-1 as did all the Rangerovers from then on from the factory. It will give you more torque at low revs but can hurt ultimate performance but that's not what your looking for. It can be a packaging nightmare on the passengers side of the engine if space is limited. Ultimately it might not be worth bothering about and if its done badly it will do more harm than good. Done well though and it can make a good difference specially on a peaky motor.

[kiwicar]

Ok I'm clearly going to learn somthing today which cylinders do you pair together? the centers are 180 deg apart from each other in firing order and the ends likewise, neither sets are firing 360 apart so they can't pulse tune each other evenly.
Also the pairs a are only 90 degrees apart. Also the order will be reversed one side to the other really can't see how it will work.

I understand a 4 into 1 works on a double plane v8 because the two on each bank firing 90 deg apart effectivly give one big pulse that scavenges the other two cylinders and on a single plane inlet manifold with a carb on it the size of a small bucket as the americans tend to like it actually gets the carb to work a bit earlier in the rev range.

Yes I know the SDI and range rover had a cast 4 2 1 set up but I assumed it was to get the whole set up around the steering column/ shaft and still get it to flow while being able to use cheep to mass produce castings, didn't realise it actually did anything!
er help
Mike

[katanaman]

8-6 4-2 then join
7-3 5-1 then join

There would have been more space on the SD1 if it had been 4-1 especially in the left hand drive market.

[kiwicar]

I see, 270, 450 apart and scavange at different revs for each cylinder.

Mike

[Ian Anderson]

See also
http://www.v-8.org.uk/forum/viewtopic.p ... highlight=

Ian

[The Original Tom]

Cheers all!
Those V8-tuner manifolds don't look like they have too sharp bends in them, and the primaries are nice and long - after having a look around elsewhere I can't be doing with the hassle of 4-2-1, and any way even though it's in a landy, when it's done 1000 miles I'm going to be showing it the rough side of 5k fairly regularly so I don't want to pinch off all my top-emd performance!
When I have the cash I'll have to talk to them and see what size the primary and secondaries are.

Tom.

[ChrisJC]

Tubular manifolds are much noisier than cast iron manifolds. I changed back to cast in an endless quest for refinement........

Chris.

[ramon alban]

Tubular manifolds are much noisier than cast iron manifolds. I changed back to cast in an endless quest for refinement........

Chris.

You are definitely right there Chris. I think there is as much crackling going on under the bonnet as in the rest of my SS system.

However its possible to look at a different solution.

The general view is that tuned headers will be more efficient than cast manifolds, better gas flow, wave propogation etc, but they give out a lot more heat and they radiate more noise.

Hot gas is less dense than cold gas, so the colder the gas the heavier it gets and therefore takes more effort to remove it from the system. Cast iron manifolds retain the heat better, tubulars do not.

So if we could keep the tubular headers hot there would be a distinct advantage.

Exhaust Wrap might therefore solve both problems (noise and heat-loss) and at the same time improve engine efficiency because less effort is require to expel the gasses.

Trouble is its difficult to do and expensive to buy.

Still, it is a route to two key refinements.

In summary then: If keeping the interior of the exhaust system as hot as possible is an advantage, then coating the ENTIRE exhaust system with thermal insulation material, such as header wrap or a ceramic thermal barrier reduces the cooling effect significantly. Cost may be prohibitive but a bonus side effect would be a cooler engine bay and down-pipe area. less noise from the entire system and the best possible power output.

There is more on this on my website.

[The Original Tom]

Yeah I pretty much decideded that I'd order some heat-wrap with the manifolds. As I've used V8 Tuners before (boughts come +0.020" 9.75:1 pistons that it turned outt I couldn't use!) and found them to be very helpful, so I'll ask how much to have them wrapped before they're sent to me.
If not how hard can it be if I wrap them off the car?
I've also heard of some paint that is designed to soak into the fibres and a) waterproof it to reduce the accelerated rusting caused by wrap, b) make them easier to handle as the wrap can't slide about whilst fitting, c) help reduce underbonnet temperatures eben more. What is it called and where can I get it!

Cheers
Tom.

[katanaman]

A word of warning about wrapping your manifolds. Your manifolds will have a very short life, roughly a year or two because they will simply fall apart due to corrosion and erosion. If you want to find out why then please search the old forum section as there were some very in depth discussions on the subject along with links to external papers.

[v8man]

got wrapping on my exhaust and been there for last 4 years and is
perfect no rust
a link to where to buy ,

http://www.agriemach.com/