wylliezx9r
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 posted on 21/3/13 at 09:14 PM |
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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
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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daniel mason
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| posted on 21/3/13 at 09:26 PM |
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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
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| posted on 21/3/13 at 09:42 PM |
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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
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| posted on 21/3/13 at 09:54 PM |
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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
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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SeanStone
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| posted on 21/3/13 at 09:57 PM |
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Supercharge it afterwards and you needn't worry
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unijacko67
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| posted on 21/3/13 at 10:05 PM |
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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]
http://www.kittenkitcar.co.uk
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Neadles
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| posted on 21/3/13 at 10:31 PM |
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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
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| posted on 22/3/13 at 01:56 AM |
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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
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| posted on 22/3/13 at 06:57 AM |
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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
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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Oddified
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| posted on 22/3/13 at 09:11 AM |
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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
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| posted on 22/3/13 at 09:37 AM |
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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
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| posted on 22/3/13 at 09:44 AM |
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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 ?
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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MikeRJ
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| posted on 22/3/13 at 10:44 AM |
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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
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| posted on 22/3/13 at 10:58 AM |
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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
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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PhillipM
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| posted on 17/6/13 at 12:37 AM |
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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
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| posted on 4/3/16 at 11:39 PM |
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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
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| posted on 4/3/16 at 11:48 PM |
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Is that a rwhp figure?
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Rocket_Rabbit
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| posted on 5/3/16 at 08:54 AM |
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quote:
Originally posted by daniel mason
Is that a rwhp figure?
Nope at the flywheel.
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daniel mason
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| posted on 5/3/16 at 08:56 AM |
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Looks a superb install!
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Rocket_Rabbit
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| posted on 5/3/16 at 09:04 AM |
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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
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| posted on 5/3/16 at 10:21 AM |
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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
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| posted on 5/3/16 at 10:27 AM |
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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
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| posted on 5/3/16 at 10:51 AM |
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I was thinking more in general terms than for the specific engine that the OP mentioned
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russtik
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| posted on 5/3/16 at 02:22 PM |
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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)
SouthernKitCars.com
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sdh2903
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| posted on 5/3/16 at 03:59 PM |
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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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