Lotus Elan Central

Has anyone looked into getting a custom part made up to replace the big black intercooler -> throttle pipe? Not that there's much wrong with the stock part (apparently it can inflate given enough boost, but I don't think most of us have to worry about that!), but I'd be interested in a one-piece fluorosilicone job with an integral 25mm takeoff for a recirc valve... particularly if it matched my samco hoses and vacuum lines!
Most valve installations I've seen look a bit messy, even the very best ones with a custom ally pipe still need a bit of flexible coupling pipe at either end - I'd prefer a nice neat one-piece option.
I'd also like to replace the ugly concertina filter box -> compressor hose at some point, while I'm at it.
Adam

ashm wrote:Has anyone looked into getting a custom part made up to replace the big black intercooler -> throttle pipe?

Cut

I'd also like to replace the ugly concertina filter box -> compressor hose at some point, while I'm at it.

Just general comment Adam
1. Both of these are fixed at one end (wing & garbage gan) and moveable at the other (engine) end so will need a fair amount of flex somewhere in the pipes.
2. The intercooler > throttle pipe needs to have a smooth diameter transition from small to large to avoid creating turbulence going into the plenum.
3. The same pipe needs to seal really well but also be easily removable for access to all sorts of things.
4. The stock pipe is pretty good because of the above reasons. Were you to, for example, do an expanding alloy pipe with rubber joints at each end then there will be a sharp step at the joints.
5. The turbo intake pipe is less critical in terms of turbulence since the turbo is 'sucking' and any turbulence at the intake side of the turbo is trivial compared to the turbulence as soon as it gets inside the turbo. So as long as the pipe can supply sufficient air to satisfy the turbo's maximum 'suck' the degree of turbulence is pretty irrelevant.
6. Those of you with filthy minds can all go take a cold shower now.

saska wrote:1. Both of these are fixed at one end (wing & garbage gan) and moveable at the other (engine) end so will need a fair amount of flex somewhere in the pipes.
3. The same pipe needs to seal really well but also be easily removable for access to all sorts of things.

These are some of the reasons why I'm looking for a single "rubbery" pipe rather than an ally one. I'm thinking of something very similar to the stock pipe, but with a 25mm branch to feed a recirc valve.

saska wrote:2. The intercooler > throttle pipe needs to have a smooth diameter transition from small to large to avoid creating turbulence going into the plenum.
4. The stock pipe is pretty good because of the above reasons. Were you to, for example, do an expanding alloy pipe with rubber joints at each end then there will be a sharp step at the joints.
5. The turbo intake pipe is less critical in terms of turbulence since the turbo is 'sucking' and any turbulence at the intake side of the turbo is trivial compared to the turbulence as soon as it gets inside the turbo. So as long as the pipe can supply sufficient air to satisfy the turbo's maximum 'suck' the degree of turbulence is pretty irrelevant.

I'm no expert (and welcome corrections!) but as I understand it, flow boundary characteristics on the intake path for a FI engine are pretty irrelevant compared to that for a NA engine, since rather than relying on the piston's intake stroke to draw air down the whole induction system and into the engine, the compressor does a much more effective job. I believe this is why airbox/filter/intake pipe upgrades and head porting/manifold tuning on the intake side tend to make little difference to the performance of a reasonably well configured FI engine. I wouldn't worry too much about turbulence downstream of the compressor and chargecooler either, the vorticity in this path will probably be enormous. Not necessarily all a bad thing either, as this'll probably help with charge mixing. I seem to recall reading that it's important not to make the intake path too smooth, as a certain amount of turbulence is essential for effective mixing. Anyway, I agree that in general a smooth transition is better and I'd prefer a neat, smoothly expanding pipe than an alloy one with rubber at each end and loads of hose clamps.
In fact, I believe the "alloy pipe with rubber joints" option is already available, but it's because I don't particularly like this solution that I was looking for a one-piece rubbery one.

As for the concertina hose, I just think it's ugly!

Adam

ashm wrote:As for the concertina hose, I just think it's ugly!

I just wrapped that one with aluminum tape (used for air ducting repair, etc). It looks 1000 times better, and cost almost nothing.

Hi Chris,

Do you have a picture??

Would love to see how it turned out.

Cheers

One small advantage of alloy pipes over rubber. Under preasure they do not expand nor collapse under vacuum. Air turbulance in a turbo motor is unavoidable. It's what a turbo does. On a related point, what motorsports car uses rubber intake/turbo pipes? Answer.... None. They either use carbon/composite or an alloy for the very reasons aforementioned. It may be "ugly" to some but it works and very well at that.

If you really want to stay "rubber" reinforced silicone like that used by Samco would be your best option. They may even do custom work though I'm sure pricey.

Marie, am I wrong in thinking that expansion under pressure is only an issue with the pipes downstream from the turbo? I think that's part of why the one going into the turbo doesn't need to have a smooth interior.

maz_r wrote:Hi Chris,

Do you have a picture??

Would love to see how it turned out.

Cheers

I could go take some, but I think you can get the idea from these pics taken at the New Orleans British Car Day show last spring. As you can see, both of my intake pipes are wrapped with the aluminum tape. It's 2 inches wide, and I just cut it into segments and wrapped them one at a time, overlapping each section of tape. This was done 100% for appearance, and there is no performance benefit. In case anybody was wondering.

lotusgirlmarie wrote:One small advantage of alloy pipes over rubber. Under preasure they do not expand nor collapse under vacuum. Air turbulance in a turbo motor is unavoidable. It's what a turbo does. On a related point, what motorsports car uses rubber intake/turbo pipes? Answer.... None. They either use carbon/composite or an alloy for the very reasons aforementioned. It may be "ugly" to some but it works and very well at that.

If you really want to stay "rubber" reinforced silicone like that used by Samco would be your best option. They may even do custom work though I'm sure pricey.

Yep, I agree with all of the above. If I wanted to run very high boost levels I'd definitely go for a rigid pipe, although probably not as slick as your setup Marie. I'm thinking of the neat built-in flange for the greddy in particular. My welding skills are very limited
I like to keep things looking clean & simple though, and so would prefer one hose and two clamps to a pipe, two hoses and four clamps. I don't think it's ugly, just not my preference. It's the same reason I don't like clothes with logos or patterns and I prefer to have my trousers made without pockets - I guess I was just born when minimalism was still cool

Silflex (http://www.silflex.com), who make the Samco hoses, do take on custom jobs but as you say they're not cheap.

I did look into getting a flexible, fibre reinforced fluorosilicone pipe custom made (pretty much a strong Samco-style pipe) but for the same money I could buy... well, a lot of other stuff!

Having mulled over the turbo/intake turbulence question... I recall as a student I once had to design and build an axial compressor for a project. I took a lot of care over the stator assembly but discovered that the output flow from a high speed compressor is almost always going to be supercritical; Could there be any point in the intake where the Reynolds number drops far enough for it to even be possible to reestablish laminar flow? I dunno, maybe in the intake plenum/manifold at very low revs... but I doubt it.

Adam

The intercooler throws a pretty big wrench in a perfect flow pattern as well as the tight 90 at the IC's outlet.