Maniflow 2 1/4" System

[edbar 6]

Spoke to longmans today and had a chat about exhaust system for my 309 trackday/sprint car. It is a 1.9 8v with 300 deg cam, headwork, 45's, high comp, lightened and balanced etc... Told them my requirements for a trackday friendly 2 1/4" system and they quated me over £400 for a large bore twin boxed large rear box maniflow system in mild steel. Now i plan to get one of their two stage manifolds in the future but for now i will have to make do with a modified standard mani but will put a large bore sytem on now. So my questions are as follows...

 

Are there any cheaper systems that fill the requirements?

Are they really worth the money?

Ashley system seems tempting but would it be too loud?

 

Any help appreciated, Edd.

[pete1986 2]

£400 for mild steel! That sounds like alot, im no expert though.

 

I recently had a stainless system made up for me, 2 1/4" bore, centre box and backbox with tailpipe of choice for £320. Not sure if it will be trackday friendly though, it fcuking roars up the top end! The exhaust fabricator said its the best sounding one hes ever done.

 

edit. just to add, the company was Autowise, but i think they have stopped making exhausts now

Edited March 18, 2009 by pete1986

[edbar 6]

Yeah thought it sounded expensive as the ashley is just over £200 in mild steel. Would want to be special for over £400!!

[Cameron 16]

You get what you pay for really. £400 sounds pretty reasonable for a one-off even in mild steel if the quality is right. An Ashley system will be cheap for a reason - cheaply made from cheap materials, so depends what you want from it and how long you want it to last. A mild steel exhaust is regarded as a throwaway item so you need to bear in mind that neither will really last that long.

Try giving BTB a call, we do a 205 system (although we haven't made them for a while) but the price is likely to be very similar to the Longmans. I could try and sweet talk the boss and get a group buy going if enough people are interested, would need at least 5 though.

[Cloverleaf 1]

I went to Maniflow workshop when I was at University as they made the exhaust for our Formula student car...their work is top class. Seen a few other systems they have made on road cars since and they are really good (also had one of their systems on my mini).

 

If you're having a bespoke or one of system made most of the costs are in setting the benders up etc.

[GTI6BOY 29]

Maniflow are top class exhaust builders.

 

Mate on the 306 forum paid £1200 for a touring car exhaust but as said you get what you pay for with them

[edbar 6]

Had a btb manifold on my old saxo vts which was very good. The car is a 309 btw, dont know if that makes a difference in length etc? I'm not afraid of spending the money on a top quality product, just dont want to throw money away.

[Miles 331 1 Cars]

I had a system on my 309 made by them out of SS that was £500.00 for a centre exit which I still have for sale if any use, it just can't be used with a std tank.

I don;t use Maniflow anymore but one of there old employee's has set up on his own and does a top job and I get a better deal too, I also supply the 4-2-1 manifolds which are a slightly revised design of the maniflow one's

[timmsy19 3]

Try giving BTB a call, we do a 205 system (although we haven't made them for a while) but the price is likely to be very similar to the Longmans. I could try and sweet talk the boss and get a group buy going if enough people are interested, would need at least 5 though.

 

Cameron i might be interested if there is anyone who is. i'd need to mate it to my standard downpipe? and have a 3" tip i think. let me know though

[Cameron 16]

I'll ask tomorrow, I haven't seen the system we make as it was before my time but I'm pretty sure we still have the jig somewhere.

[timmsy19 3]

ok if you do get any pics from somewhere of anything pm me some details. if i can afford it i might be interested even if you can get a group buy seeing as DES is no more

Edited March 18, 2009 by timmsy19

[oli-pug 6 2 Cars]

I could be interested in a btb system cameron. Are we talking stainless for that price bracket, probably not?

[edbar 6]

Seems i now have a few options to work with, interesting really as long as ive been a member ive seen no in depth topics on what large bore systems are available and them in use. Seems most people either use a standard system or 2".

[DrSarty 90 1 Cars]

I don't want to throw a cat amongst the pigeons here, but what exactly do we mean by big bore here?

 

The reason I ask is that 2-2.25inches as I understand it (system - not tailpipe) as quite adequate, if not ideal for up to 200-300 (+) BHP.

 

What I'm asking is what is the realworld benefit of a larger exhaust other than more noise? A Le-Mans V10 850BHP Dodge Viper a friend of mine race prepares doesn't have an exhaust much bigger than 2.25inches (per bank), so I'm not really sure I understand the point of a large bore exhaust.

 

Happy to be educated.

Edited March 19, 2009 by DrSarty

[DrSarty 90 1 Cars]

Instead of just typing 'double post', I thought I'd just ask if that is the reason Ed that:

 

most people either use a standard system or 2".

 

?

Edited March 19, 2009 by DrSarty

[bales 1]

I don't want to throw a cat amongst the pigeons here, but what exactly do we mean by big bore here?

 

The reason I ask is that 2-2.25inches as I understand it (system - not tailpipe) as quite adequate, if not ideal for up to 200-300 (+) BHP.

 

What I'm asking is what is the realworld benefit of a larger exhaust other than more noise? A Le-Mans V10 850BHP Dodge Viper a friend of mine race prepares doesn't have an exhaust much bigger than 2.25inches (per bank), so I'm not really sure I understand the point of a large bore exhaust.

 

Happy to be educated.

 

The way always have understood it is that the actual manifold design i.e length and diameter of the primaries and the collector design is the most important aspect. As in terms of a race engine after the collector and a short length you would generally be unsilenced after that for max power.

 

In my four stroke performance tuning book they actually have a formula for the tailpipe size (bore) based upon the cc of the engine and the primary lengths.

 

Though the table it gives for general sizes that I have always gone off is;

 

80-120bhp - 1 7/8"

110-140bhp - 2"

130-150bhp - 2 1/8"

140-185bhp - 2 1/4"

180-220bhp - 2 1/2"

210-265bhp - 2 3/4"

250-320bhp - 3"

280-360bhp - 3 1/2"

400-500bhp - 4"

480-630bhp - 4 1/2"

580-750bhp - 5"

 

If there is 2 exhausts i.e 2 banks then you divide the hp by two

[Cameron 16]

I don't think that's all that accurate really.. we use 2.5" systems for up to around 400bhp.

The mass flow rate of a tube isn't directly proportional to the tube diameter, so a tube of 5" won't flow twice the amount of a 2.5" it will flow much much more!

 

Anyhow, I've asked the boss and we seem to still have a 205 jig around somewhere although I'm not sure if it is the right one. He's going to have a check in the barn (where all the old jigs are stored) and see if he can dig it out, but to be honest he doesn't seem too keen on making them.

[bales 1]

I don't think that's all that accurate really.. we use 2.5" systems for up to around 400bhp.

The mass flow rate of a tube isn't directly proportional to the tube diameter, so a tube of 5" won't flow twice the amount of a 2.5" it will flow much much more!

 

You might want to speak to Alexander Graham Bell then! are you talking about 400bhp n/a? as those pipe diameters are for n/a engines not FI.

 

What engines have you got running 400bhp n/a that exits through 1 pipe i.e is an inline engine!!

 

If its a V8 or something then it will have 2 pipes which is equivalent to 200bhp per exhaust which is 2.5" like you say??

 

Pipe ID = √(cc x 2) / ((P + 3) x 25) is the actual formula given if you want to see how that equates to your exhausts.

 

Where P is the primary length in inches

[DrSarty 90 1 Cars]

You might want to speak to Alexander Graham Bell then! are you talking about 400bhp n/a? as those pipe diameters are for n/a engines not FI.

 

What engines have you got running 400bhp n/a that exits through 1 pipe i.e is an inline engine!!

 

If its a V8 or something then it will have 2 pipes which is equivalent to 200bhp per exhaust which is 2.5" like you say??

 

Pipe ID = √(cc x 2) / ((P + 3) x 25) is the actual formula given if you want to see how that equates to your exhausts.

 

Where P is the primary length in inches

 

Oh God! What have I started now?

 

When I used the above formula (estimating from Kabul my primary 'P', which I guess is exh port to collector on a 4-2-1 Maniflow):

 

√{(2187cc x 2) / ((18"+3") x 25)} = 2.88inches internal diameter. (Note the added parenthises to allow the formula to work)

 

As my engine is realistically 225-230BHP then that 2.88" is a little high, but not much. As I probably under-estimated my primary, then a more accurate figure would be lower, perhaps near 2.25-2.5 inches.

 

What I don't understand is the distinction between N/A and F/I, because my mind tells me that fluid dynamics shouldn't distinguish whether it's an engine blowing gases down a tube or my backside. (?)

Edited March 19, 2009 by DrSarty

[bales 1]

The way I see it is that on a n/a engine the exhaust bore is designed to give the correct gas speed with back pressure being the unwanted side effect of this, as the gas still has 'work' to do so to speak.

 

With F/I engines the once the gas has left the exducer all you want of it is to cause as little resistance i.e backpressure - to the flow through the turbo as possible. Meaning that there is no unwanted energy slowing down the whole process, it doesn't actually contribute to or is used as a tool for the fundamentals of the exhaust system....apart from in a roundabout way.

 

I hope you understand what I am trying to say.

 

I think you have to draw a boundary between road engines and race engines though as on race engines you would only have a short length of tailpipe, i.e F1 cars exhaust straight out of the collector!

[Cameron 16]

Well off the top of my head the Subaru WRC systems were 2.5" and they put out what, around 300bhp?

I'm not doubting Mr Bell or anything, I'm just pointing out that those are just guidelines and there is a great deal of flexibility in them.

[edbar 6]

I don't want to throw a cat amongst the pigeons here, but what exactly do we mean by big bore here?

 

The reason I ask is that 2-2.25inches as I understand it (system - not tailpipe) as quite adequate, if not ideal for up to 200-300 (+) BHP.

 

What I'm asking is what is the realworld benefit of a larger exhaust other than more noise? A Le-Mans V10 850BHP Dodge Viper a friend of mine race prepares doesn't have an exhaust much bigger than 2.25inches (per bank), so I'm not really sure I understand the point of a large bore exhaust.

 

Happy to be educated.

 

Sandy brown recommended a 2 1/4" system and large bore meaning larger than standard (standard being 2") Was going off his personal results with these engines. Is he wrong then?

[Cameron 16]

Nobody is wrong!

[edbar 6]

Cameron you work at BTB and i trust them from experience, Does 2 1/4" sound over zealous to you?

[DrSarty 90 1 Cars]

large bore meaning larger than standard (standard being 2")

 

 

Well 2" to 2.25" is hardly what I'd call large bore. That's precisely why I asked the question.

 

The fact that Sandy's using/recommending 2.25" pretty much proves that table above and what I was saying.

 

Had you meant 3" or 4", or one of those stoooopid 'I can practically live inside my tailpipe Subaru' type exhaust systems, then I could've seen where you were coming from.

 

Now I know you meant a 0.25inch increase I'll shut-up.