Exhaust Manifold for Cosworth V6 2.9 Granada

[kevchard]

Has anyone got or had made up a set of manifolds for a 2.9 V6 Granada Cossie?I am making a Cobra replica with this engine fitted.
Any dimensions (either theoretical or actually measured) will be a help. I am looking at using 1 3/4" steel tubing for the primaries and 2" or 2 1/2" for the remaining pipework.
Cheers

[boosted ls1]

Hi Kev,

I wouldn't worry to much about exact lengths. I've read that equal lengths can be used to tune peak bhp but that mismatched lengths can help with a fatter torque curve which is much more useful. Or did I get that wrong? I doubt that anything on the market will have been developed as such.

Boosted.

[350matt]

A little something I prepared earlier... Matt
Exhaust and intake length tuning

You will also need to determine the capacity of your engine, by using the number of cylinders and the capacity of each. To discover the best length and diameter of pipe for your engine, you will need to know the exhaust valve timing; that is the number of degrees before bottom dead centre that the valve starts to open. with this knowledge you can then set about making a tuned exhaust system by working out the following formula and applying it to your own engine:
850 (180 + N)
L =(------------- )- P
RPM
where L = length of pipe in inches
N = degree before BDC exhaust valve opens
P = distance from exhaust valve to manifold
and RPM = desired RPM For peak power

The diameter of the pipe needs to be calculated so that the volume of the exhaust pipe attached to each cylinder is twice the volume of each cylinder. The exact diameter of the pipe, incidentally, is not critical and should only be used as a guide in determining which standard sized pipe diameter should be used.
As a guide, this is example calculation. If the exhaust valve opens 110 degrees before BDC. The engine capacity was 700 cc per cylinder and the desired peak power RPM is 6,500

850 (180 + 110)
L =(--------------) - 3 in = 887 cm = 34.9 inches.
6,500
To find the diameter of pipe, the following formula can be used:
π r^2 L = 2 * 700cc
π r^2 * 223 cm = 1400cc
r = 1.4 cm
Diameter = 2.8 cm or 1.1 in
The nearest standard stainless steel tube available was 1.5” Ø.
If a primary pipe is oversize the consequences are far less severe than being undersize and unless a pipe is massively oversized it will have little detrimental effect.
To reduce the weight and complexity of the finished system, the exhaust pipe can be of a two-into-one type, with the joint at half length. The single pipe then finishes the required length and then the two pipes can then be joined together into a single collector and the exhaust silencer is then fitted onto the end of this single pipe. Typically this will not produce as much power as a well designed 4 into 1 system but is often far more convenient to package


INTAKE RUNNER LENGTH ii
ECD = Effective Cam Duration
RV = Reflective Value = 2 for 2nd reflection 3 for 3rd etc – the earlier the reflection = the stronger the tuning
ECD = 720 - (Adv. duration - 30)
Speed of sound = 396m/sec
intake runner length = ((ECD/360) × (1/(tuned rpm /60))* speed of sound)/(2*RV)
( ((470/360) x (1/6000 /60))*396) /(2 *6) = 0.43mtrs




All of the above calculations will get you somewhere close to the perfect length ie within an inch on the exhaust, but this can only be confirmed by dyno testing, consequently these numbers are a rough guide only.

[thong]

I have a pair of stainless maifolds for granada cossi v6,www.stainless-exhaust.com made them ask for don great chap and real nice job,
there number is 01623 552262.
If you want to get real technical with the most complex component of the i/c engine(the camshaft) ask this chap the best cam chap in the world-
- www.profblairandassociates.com, just dont make it loud (under silence it)then the stock cams should be ok,the bottom end of these motors arnt that strong so dont over rev it etc then you'll be ok,
Dale.

[boosted ls1]

thong said:

the bottom end of these motors arnt that strong so dont over rev it etc then you'll be ok, Dale.

They need a girdle for sustained rpm's

boosted.

[kevchard]

Thanks for all your help.
I will be contacting the stainless people on monday to see what sort of figures they are quoting.
I have contacted a company on friday called www.powercraftengineering.com and they have quoted £500 inc vat etc, for a 1 off set of pipes for the cossie. Do you think this is out of the way?
I have had prev quotes of £550 inc VAT & £600 plus VAT up until then.
I am working on some drawings at the moment to send to the company i choose.
Cheers
Kevin

[boosted ls1]

Kev,

That doesn't sound unreasonable for a pair of custom headers. There are several grades of stainless, make sure you get the grade that lasts for ever, Stainless Steve will know what grade that is if you pm him. 318 rings a bell but I'm probably wrong, it could be a house number

Boosted.

[thong]

I paid £705 inc vat.that included pair of manifolds and pair of pipes that bolt to 3 pin flanges that bring the system down under the floor of kit car inc bend in pipes,spot on job.