S1 air intake hose upgrade guide(ish)

[Kitchski]

Hi all,

Not made too much noise about it, but sadly sold my S1 that I've had since 2013 last week. It's gone to live in a beautiful part of Ireland, though, so it's probably happier than I am!

Anyway, I answered an email just now on about making a silicone/alloy intake pipe for the 2.8 engines. I wrote a fairly wordy reply, and then thought I might as well share it with the 'group', in case it helps somebody, somewhere:

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This is the site I used last time I bought silicone hose components. We do have some in the UK, but the service is poor. I received these faster from Poland than I would have done from UK-based suppliers!

https://fmic.eu/en/

Using a combination of hoses and aluminium pipework, you can create the intake pipe. The hoses are measured I.D, and the pipes are O.D (so the sizes match).



My process would be:

• First part to go on the throttle body, which you’ve already measured the O.D of. I would use a short piece of silicone here (50mm – something like that) because on my car (see image attachment) I used a silicone elbow to come out from the throttle body, turn 90degrees and then into the alloy pipe (well, I used stainless steel, but I would advise against it as it is harder to work with). Because the silicone hose is thicker than the pipe would have been, it caused it to foul on the bonnet slightly (you can see the mark). Not a huge problem, but it’s still one you could avoid, so what I would recommend here is to buy a length of silicone hose, the I.D of which matches the throttle body, and cut a piece off which will join this to the first piece of pipework. I would buy a length of, say, 500mm, rather than just the small section you need as you may need more to make adjustments later.

• Second, should be an alloy ‘elbow’ (this sort of thing: https://fmic.eu/en/37-135-elbows?page=3) The silicone hose you’ve cut will join this to the throttle body. I would go for 135degrees, but don’t assume this will be right (if TVR didn’t use a jig to position the tabs that the airbox bolts to, then each car is likely different!) It’s probably the closest you’ll find to what you need, though, and if you need to reduce this angle slightly, you can cut the pipework down at the T/B end slightly until the desired angle is achieved (this is why you have to make them on a car). You’ll have to cut this end down, anyway, because you need to buy an elbow with the longest legs possible, as on the metering unit side, it’s a much longer run. Ideally you would be inserting the pipe into the silicone joiner actually on the angle, but sometimes you don’t have much choice! Being able to form a swage Don’t forget jubilee clips, too – you’ll have used two by this point already!

• Once the alloy pipe is the right length on the T/B side, you need to connect it to the plastic joiner that goes into the bellows on the M/U side. This should be the same diameter as the throttle body, but check it first! In an ideal world, you’ll be able to use a ‘hump’ joiner to connect it (see here: https://fmic.eu/en/14-hump). These are desirable as the hump in the pipe allows some movement in the system, and you’ll need as much as possible, because in the course of driving, the engine moves around on its mounts; The metering unit does not! The rubber bellows on top of that may be brittle with age, so ideally you want to allow some flexibility prior to this, and the hump is the part to do it. Potential problem? The hump pieces are only made in a certain length (unless you have something custom-made), and this may not be long enough to bridge the end of the pipework and the plastic joiner in the intake bellows. Worst case here – you either forgo the hump and use your redundant straight hose (which will work, it’ll just put more strain on the rubber bellows), or you join the hump and another piece of hose with a redundant bit of alloy pipe, to lengthen it. It won’t look good, though, and you’ll have a multitude of jubilee clips spoiling the look of it. (In an ideal world, you’d put the ‘hump’ at the T/B end, and use it as the joiner, but there isn’t the room under the throttle linkage to do this, sadly.)

Remember jubilee clips, too. You’ll use anywhere between 4 and 8 of them. I would choose a size that covers 5-10mm more than the overall outer diameter of the silicone hose (will be around 10mm on top of the I.D), otherwise they’ll be too long and won’t look neat (see the two I STILL never got round to swapping for shorter ones!)

If you explore the FMIC.eu site, you’ll see that there are a multitude of different combinations you could create, and you may well design something better than me! That said, having done a few, I think this would be the best layout for looks vs. durability. There are ways of making it look prettier still, but not without compromising the rubber bellows on the M/U, and you do not want that to fail![/i]

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It's not that hard to do, really. Take your time, make it neat - job's a good'un!

Edited by Kitchski on Tuesday 18th February 12:01

[WotnoV8]

Similar setup on my S.