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Author: Subject: The effect of lengthening manifold primaries S2000
wylliezx9r

posted on 21/3/13 at 09:14 PM Reply With Quote
The effect of lengthening manifold primaries S2000

For all you boffins out there.

To make an off the shelf manifold fit my S2000 F20C engine I am going to have to lengthen the primaries. Does anybody know what effect this is going to have ? I'm guessing its going to move the torque lower or higher in the rev range ? Or is it just going to choke the engine completely ?

ATB Dan





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daniel mason

posted on 21/3/13 at 09:26 PM Reply With Quote
the standard system is a very highly tuned setup,and the engines are very sensitive to exhaust changes..if you dont spend money on a good tuned setup you will almost definately loose a chunk of performance!






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franky

posted on 21/3/13 at 09:42 PM Reply With Quote
quote:
Originally posted by wylliezx9r
For all you boffins out there.

To make an off the shelf manifold fit my S2000 F20C engine I am going to have to lengthen the primaries. Does anybody know what effect this is going to have ? I'm guessing its going to move the torque lower or higher in the rev range ? Or is it just going to choke the engine completely ?

ATB Dan


Well by going higher or lower you're hitting all bases

You'll end up with more midrange as a rough rule of thumb, depends on other factors though too.

You won't choke the engine at all, you're talking a very very small percentage of perceptible change if any.

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wylliezx9r

posted on 21/3/13 at 09:54 PM Reply With Quote
quote:
Originally posted by franky
quote:
Originally posted by wylliezx9r
For all you boffins out there.

To make an off the shelf manifold fit my S2000 F20C engine I am going to have to lengthen the primaries. Does anybody know what effect this is going to have ? I'm guessing its going to move the torque lower or higher in the rev range ? Or is it just going to choke the engine completely ?

ATB Dan


Well by going higher or lower you're hitting all bases

You'll end up with more midrange as a rough rule of thumb, depends on other factors though too.

You won't choke the engine at all, you're talking a very very small percentage of perceptible change if any.


This is pretty much what I concluded with the limited amount of research that I have done. I'm not going to be changing the length ratio between the four pipes, I'll be adding the same length to all four.

Thanks





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SeanStone

posted on 21/3/13 at 09:57 PM Reply With Quote
Supercharge it afterwards and you needn't worry
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unijacko67

posted on 21/3/13 at 10:05 PM Reply With Quote
Read this chaps article on how to make your own, really good read. Sound bloke and can supply bends I believe.

http://www.ojzengineering.co.uk/

[Edited on 21/3/13 by unijacko67]





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Neadles

posted on 21/3/13 at 10:31 PM Reply With Quote
You may see a slight issue with a reduction in your scavenge effect across the exhausting cylinders. As you know Honda engines have high flowing heads and lengthening the primaries will reduce the effect of the low pressure created by the escaping gases aiding the removal of the combustion process. Alternative FI will sort it out This is a very precise sciences with high powered Honda engines but since its in a small chassis the change if power will not be a real issue I would say.
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Bare

posted on 22/3/13 at 01:56 AM Reply With Quote
Sigh.. IF you knew what you were doing you wouldn't be asking.
When you have the knowledge required to redesign it ...then you might not :-)
Want Mo' power ? insert some crap Rover v8 lump.

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snapper

posted on 22/3/13 at 06:57 AM Reply With Quote
Primary length, secondary (if you have a 4,2,1) and overall length to collector all have an effect.
In reality it will only effect a small specific rev range and therefore will not make a noticeable difference on the road
I did the maths on my Pinto manifold and have it set for a slight torque advantage but this also required a tuned inlet manifold length

If it realy bothered you and you have a 4,1 playing with the collector diameter and length plus where the silencer starts can restore the effect

But IMHO don't obsess





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Oddified

posted on 22/3/13 at 09:11 AM Reply With Quote
As said above, the pipe length to the first silencer also effects it, so when it's fitted in a different car with changed silencer position/s it's all changed any way.

As a rule of thumb lengthening the primarys will move the power band down the rpm slightly (unless your changing them a lot?).

The fuel map will probably need a few minor tweeks though (it will need more fuel in the area of where the torque has been moved to and less where it used to be).

Ian

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PeteS2k

posted on 22/3/13 at 09:37 AM Reply With Quote
Mine's running on a standard intake, DTA ECU, 4-1 manifold built to fit my engine bay (with primaries too short according to the calcs, but equal length). It still made 240bhp max when being mapped, and drives really well.

Of course, perhaps it could have made a lot more, with better mid-range etc, with a more optimised exhaust. But then, the other accepted fact with this engine is that it's difficult to make any significant gains without major work?

I did try to work out the theoretical pipe lengths - then compared them to the OEM manifold. At which point I just left it to the exhaust manufacturer - the OEM primaries are all over the place! Which I thought odd for an engine apparently so sensitive?

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wylliezx9r

posted on 22/3/13 at 09:44 AM Reply With Quote
quote:
Originally posted by Bare
Sigh.. IF you knew what you were doing you wouldn't be asking.
When you have the knowledge required to redesign it ...then you might not :-)
Want Mo' power ? insert some crap Rover v8 lump.


What the f*ck are you on about ? Am I missing something ?





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MikeRJ

posted on 22/3/13 at 10:44 AM Reply With Quote
quote:
Originally posted by wylliezx9r
quote:
Originally posted by Bare
Sigh.. IF you knew what you were doing you wouldn't be asking.
When you have the knowledge required to redesign it ...then you might not :-)
Want Mo' power ? insert some crap Rover v8 lump.


What the f*ck are you on about ? Am I missing something ?


God knows, that confused me as well, not even sure who it's directed at?

Longer primaries will tend to favour low/mid range torque, but often will have minimal impact on peak HP. A friends tarmac rally Peugeot 205 is producing ~280bhp from a very highly tuned Mi16/GTi6 hybrid engine, and uses extremely long primaries. In fact they end somewhere around where the back seat would be if it had one.

However, it will almost certainly to need changes to the the fueling to optimise the power output after changing the manifold.

[Edited on 22/3/13 by MikeRJ]

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wylliezx9r

posted on 22/3/13 at 10:58 AM Reply With Quote
quote:
Originally posted by MikeRJ
quote:
Originally posted by wylliezx9r
quote:
Originally posted by Bare
Sigh.. IF you knew what you were doing you wouldn't be asking.
When you have the knowledge required to redesign it ...then you might not :-)
Want Mo' power ? insert some crap Rover v8 lump.


What the f*ck are you on about ? Am I missing something ?


God knows, that confused me as well, not even sure who it's directed at?

Longer primaries will tend to favour low/mid range torque, but often will have minimal impact on peak HP. A friends tarmac rally Peugeot 205 is producing ~280bhp from a very highly tuned Mi16/GTi6 hybrid engine, and uses extremely long primaries. In fact they end somewhere around where the back seat would be if it had one.

However, it will almost certainly to need changes to the the fueling to optimise the power output after changing the manifold.

[Edited on 22/3/13 by MikeRJ]


I have a fully mappable ECU (Omex 7100) it will be going for a rolling road session before being driven on the road. I'm feeling quite posotive about doing this now, I really can't afford the £1000 to get a custom manifold built at the moment.

Thanks for all the comments





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PhillipM

posted on 17/6/13 at 12:37 AM Reply With Quote
quote:
Originally posted by MikeRJ

Longer primaries will tend to favour low/mid range torque, but often will have minimal impact on peak HP. A friends tarmac rally Peugeot 205 is producing ~280bhp from a very highly tuned Mi16/GTi6 hybrid engine, and uses extremely long primaries. In fact they end somewhere around where the back seat would be if it had one.




It depends on how long you can go really, if you can add enough extra length you get to the next set of resonances (which are often stronger with the longer manifold), anyway, you'll often run out of space before you get enough length in, we went for maximum midrange for ours and the manifold looks like some sort of accident in a pipe factory.

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Rocket_Rabbit

posted on 4/3/16 at 11:39 PM Reply With Quote
Drag up an old thread, but still relative.

I had mine rolling roaded at EFI parts. Also had some wiring done and I can't stress at how good Chris is.

The car made 214bhp with this exhaust. A run was performed with and without the silencer - no difference.








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daniel mason

posted on 4/3/16 at 11:48 PM Reply With Quote
Is that a rwhp figure?
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Rocket_Rabbit

posted on 5/3/16 at 08:54 AM Reply With Quote
quote:
Originally posted by daniel mason
Is that a rwhp figure?

Nope at the flywheel.








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daniel mason

posted on 5/3/16 at 08:56 AM Reply With Quote
Looks a superb install!
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Rocket_Rabbit

posted on 5/3/16 at 09:04 AM Reply With Quote
quote:
Originally posted by daniel mason
Looks a superb install!

This happened after 3 miles of driving, including the RR session:

I will be redesigning the rear diff mounting structure and using an RX8 diff. Roadrunner have been sh1t TBH. They built the car and supplied the reconned diff. This type of thing can happen after 'extreme' use which in my case was driving it up and down an access road and then onto a trailer.

I don't want to corrupt the thread, so i'll post more about it elsewhere

Looking at the exhaust, I'm convinced it's the 4-2-1 section that is costing power. I do have a 4-1 collector so I might get the exhuast modified to accept that.






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SteveWallace

posted on 5/3/16 at 10:21 AM Reply With Quote
quote:
Originally posted by daniel mason
the standard system is a very highly tuned setup,and the engines are very sensitive to exhaust changes..if you dont spend money on a good tuned setup you will almost definately loose a chunk of performance!


Just out of interest, what sort of percentage performance difference are we talking about when comparing a very well designed (and expensive) set of primaries with a low cost version that has been made to look right but without referring to someone who has a PhD in gas flow dynamics?

Are we talking extracting the last fraction of performance that could shave fractions of a second off lap times, or something where you get in the car for a blat in the countryside at the weekend and go "I wish I'd spent more on exhaust design"?

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daniel mason

posted on 5/3/16 at 10:27 AM Reply With Quote
You could make one out of scaffolding tube and it would still go like a stabbed rat with an f20c in it. But it would be a fair chunk lost.
Per lind on here knows his stuff regarding the f20c! User name PWL

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SteveWallace

posted on 5/3/16 at 10:51 AM Reply With Quote
I was thinking more in general terms than for the specific engine that the OP mentioned
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russtik

posted on 5/3/16 at 02:22 PM Reply With Quote
quote:
Originally posted by Rocket_Rabbit
This happened after 3 miles of driving, including the RR session:

I will be redesigning the rear diff mounting structure and using an RX8 diff. Roadrunner have been sh1t TBH. They built the car and supplied the reconned diff. This type of thing can happen after 'extreme' use which in my case was driving it up and down an access road and then onto a trailer.


Hmmm, that looks familiar... (clearly a design flaw in the SR2)







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sdh2903

posted on 5/3/16 at 03:59 PM Reply With Quote
That's definitely a mounting point issue as they've gone in nigh on exactly the same spot. How comes roadrunner have decided to bolt them down rather than hanging as per standard fit and also mnr/westfield? Looks like a couple of spacers required to prevent the mounting arms being under stress perhaps?
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