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Big Valves


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103 replies to this topic

#21
crf450

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Obviously I don't know anything about the cam profile you are going to use so it's hard to estimate anything about your engine's potential. If you have gone for ultimate race tune with no thought to tractability you might get close to your power targets. If you've stayed moderate on cam duration I'll be impressed if you exceed 245/250 bhp at 7600 rpm.

Dave, all I can tell you (which is all I know) about Eddies profiles for my engine is they are 246duration from 1mm open to 1m closed with 11.6mm of lift with peak power predicted at 8500rpm.
As soon as my cars close to going on the dyno I'll let everyone know.
Cheers Martin

#22
PumaRacing

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Dave, all I can tell you (which is all I know) about Eddies profiles for my engine is they are 246duration from 1mm open to 1m closed with 11.6mm of lift with peak power predicted at 8500rpm.
As soon as my cars close to going on the dyno I'll let everyone know.
Cheers Martin

Interesting. That's a very mild grind then. If the figures are comparable, less duration than any of the Catcams mechanical profiles.

I guess we have to wait for the dyno tests and see what happens.

#23
Sam

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Someone must have hacked his account, that wasn't a sarcy reply :D :)

#24
PumaRacing

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Hi Martin,

I recall you mentioning that the exhaust manifold was a critical part of your guy's design. I'd be interested in the manifold primary pipe diameter he chose if it's already been decided on. My calcs suggest he possibly went for 1 7/8" (47.6mm) o/d if it was imperial tubing with 1/16" wall thickness. Any comment?

#25
base-1

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i *think* its already been designed and made and hes posted pics of it..... cant remember if he posted any specifics though

#26
crf450

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Dave, your quite right the pipe Eddie's chose for the primary's was 16swg 17/8"o/d tube.
To help him decide the overall design of the system I had to make him 3 different sized stubs which he bolted onto a finished exhaust port then fitted one of his many different bends to which he then flow tested.
Making the stubs was a right nightmare as I had little experience in flaring tubes or making tooling to do it, I also ended up turning the tube for the stubs out of solid.
After Eddie flow test all the stubs he made me a drawing of the whole system which I took to Tony Law exhausts along with my car.
The drawing details included,
Diameters and lengths of primary's and secondry's, diameter with three options for length for the main pipe and which cylinders were to be connected.
Cheers Martin

#27
fiji bob

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martin do you mind putting up a pic of the pic? doesnt have to show any detail im just interested in seeing it

#28
PumaRacing

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Dave, your quite right the pipe Eddie's chose for the primary's was 16swg 17/8"o/d tube.

Also most interesting then. I wouldn't say exhaust systems is really my speciality or something I get involved in much but I did write a computer programme many years ago based on flow requirements of gases at high temperature and it says 1 7/8" o/d pipe for outputs around his target of 70 bhp per cylinder. I would say from past experience that most people go far too large on exhaust systems so clearly his views and mine agree in this area.

All that remains to be seen then is if we end up closer to 280 bhp or 245/250. Whatever the outcome it will be very informative for all concerned and I will be quite happy to be proved wrong and learn something new from this.

#29
phatgti

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excellent thread gents.

dave i have vizards tuning the A series from my metro days, its been lent out so i shall have to go door knocking.

i understand what your saying about the theory and actual practical side of it, i dont have access to a flowbench but if i can understand the "theories" behind flow seperation and the way gas acts at different temperatures and valve lift then i'd be happy.

martin, do you know of any websites or books on the subject of manifolds or systems as i understand some of what you wrote but the lingo lost me a little - stubs etc...

thanks
Wayne

#30
Batfink

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something tells me I should be measuring my Maniflow manifold ; then getting depressed on its primary lengths and diameter

#31
crf450

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martin do you mind putting up a pic of the pic? doesnt have to show any detail im just interested in seeing it

No probs,any offers for hosting pic?

#32
blackscooby

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No probs,any offers for hosting pic?

CRF450...

You have PM re hosting.

#33
blackscooby

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Apologies for the delay !

http://www.peugeotsp...emp/Picture.jpg

#34
fiji bob

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cheers gents

#35
cybernck

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excellent sketch ;).

i would have expected that primaries would be tuned length across all 4 cylinders though :(.

#36
crf450

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excellent sketch ;).

i would have expected that primaries would be tuned length across all 4 cylinders though :(.

They are the same length at 28.5,the drawing isn't to scale.
Cheers Martin

#37
Alan_M

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Anybody measured the Maniflow system?

#38
cybernck

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ahhh, you mean they're curved but it doesn't show in this planar view? :)

#39
petert

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All a good read guys, but back to the original question, there are two reasons for changing valves in an Mi16:

1. A bigger head, what ever the size, allows a much better inlet seat to be cut, giving a better flow out of the bowl. The std. seat has just one 45 deg. cut, which then drops straight into the bowl. A well cut 3 angle seat needs a bit more metal to be done correctly, than what's available with the std. inlet valve/seat. It's the resultant 3 angle seat that makes the thing flow well, not necessarily the size of the head diameter.

2. Changing from multi-groove to single groove collets increases reliability.

#40
MartinR

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point 2 is up for debate i think.

my thinking is that it doesnt make a difference. What i will say though from personal experience is that Ford changed the valve in their 2 litre Zetec FROM a single collet groove TO a triple collet groove

the mind boggles