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

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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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

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Originally posted by franky

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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

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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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Supercharge it afterwards and you needn't worry

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]

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.

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.

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

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

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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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.

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Originally posted by wylliezx9r

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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.

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

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Originally posted by MikeRJ

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Originally posted by wylliezx9r

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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.

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

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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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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.

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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.

Is that a rwhp figure?

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Originally posted by daniel mason
Is that a rwhp figure?

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Looks a superb install!

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Originally posted by daniel mason
Looks a superb install!

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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!

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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

I was thinking more in general terms than for the specific engine that the OP mentioned

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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.

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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?

Off topic some what I know and I'm sorry....The MX5 cast ali cover and arms is designed to fail at that point it has two notches cast in to the arms. The diff when mounted in the MX5 floats within the sub frame on the rubber bushes and the nose is connected to the back of the gearbox by the ali back bone (the correct name of it escapes me just now). You need to solidly mount the nose of the diff and replace the rubber bushes in the arms with some thing a lot stiffer.
I how ever did away with the cast cover all together in the TMXR and made the MX5 diff fit in to the standard Roadster suspension cage with this fabricated item which gives four mounting points.




[Edited on 5/3/16 by Talon Motorsport]

I'm just going to add a bit more to the exhaust parts of the thread
Working with exhaust primary lengths and diameters is a very exact science, it takes into account not just the exhaust but also the inlet tract length from the end of the bell mouth to the valve head, the cam duration and I believe the stroke.
The guy who did the calculations for me on Turbosports forum provided ideal inlet tract length and the length, diameters of the primaries and the collector with different lengths for the 1st 2nd 3rd and 4th harmonics he also said which worked best for my engine
I was lucky the Pinto 4 branch I had fitted neatly into one of the preferred ranges, the collector was ok and the can near enough, pipe size was to large
I did not loose any bhp but didn't gain much
In any case the ideal exhaust would be built to deliver the torque at the desired revs and will only be at one small rev band
For me I want to enhance mid range torque as this is where I mostly am, brief excursions to high revs doesn't give me any advantage on the road especially with high lift long duration cams, you want to fill the off cam gaps to get a better driving experience
IMHO

It wouldn't be easy to make the perfect manifold for the F20 engine. To achieve the excellent HP figure they surely must have tuned the system toward high revs. To match the variation in cam timing given by the VTEC system I would be expecting the sort of variable tuned length systems used on some superbikes. Think "EXUP" or "HIVEX" to name the Yamaha and Honda versions. But Honda don't deem it necessary for the F20. In fact, I can't think of one car engine using this concept.
But loads have used a similar system on the inlet side.
Does this indicate that tuned lengths are more beneficial on induction than on exhaust?

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Originally posted by SPYDER
It wouldn't be easy to make the perfect manifold for the F20 engine. To achieve the excellent HP figure they surely must have tuned the system toward high revs. To match the variation in cam timing given by the VTEC system I would be expecting the sort of variable tuned length systems used on some superbikes. Think "EXUP" or "HIVEX" to name the Yamaha and Honda versions. But Honda don't deem it necessary for the F20. In fact, I can't think of one car engine using this concept.
But loads have used a similar system on the inlet side.
Does this indicate that tuned lengths are more beneficial on induction than on exhaust?

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I was fortunate enough to get a RR printout from a standard S2000 on the same RR as mine was tuned on:

Mine:




S2000:



If you look at the torque curve, after 6500rpm on mine, it drops down a fair bit whereas on the OEM car it remains flat.

I am pretty sure this is indicative of a restriction and not a lack of scavenging effect which at high rpm, really shouldn't be as vital.

Opinions welcomed.