S1 undertray

tut · Post by **tut** » Sat Nov 18, 2006 2:05 pm

Trying to buy a used large centre section S1 undertray, as mine is knackered.

Nothing on eBay at present, so though unlikely, worth checking if anybody has one, or knows of one.

Cheers

tut

Bob vanM · Post by **Bob vanM** » Mon Nov 20, 2006 7:57 pm

can Lotus not supply them or are they fancy priced ?

tut · Post by **tut** » Mon Nov 20, 2006 9:17 pm

Have not checked with Lotus Bob, but Geary does them at £170.

However my retired old blacksmith next door is making one for me from galvanised steel, so even stronger than the original, for beer money, so that should do fine.

Feelers out in the meantime for a reasonably priced rear subframe.

tut

Lawrence · Post by **Lawrence** » Mon Nov 20, 2006 9:22 pm

Good idea tut a steel one will add to the rear downforce.

dr al · Post by **dr al** » Mon Nov 20, 2006 10:52 pm

Is it not just a sheet of flat aluminium cut to shape?? - or am i thinking of a different bit?

couldn't you just get a sheet of aluminium and borrow someone's to get the shape right and the holes in the right place?

verious kit car places sell naca ducts pretty cheap. look at the mags in which-kit or something??

A.

tut · Post by **tut** » Mon Nov 20, 2006 11:00 pm

It is just flat, with a lip at the forward edge. He is using mine as a template.

Not bothered about the NACA ducts, the plastic inserts had both ripped off anyway, so he will just cut out the shapes, which I presume were for airflow cooling.

1.6mm galvanised steel sheet plate will be stronger than aluminium anyway, and the weight penalty is not much, and low down. Mine shows the sort of punishment that they take on goat tracks and humps, paper thin and worn through in places, all the bolt holes enlarged, so this one will take much more punishment.

tut

Rich H · Post by **Rich H** » Tue Nov 21, 2006 9:21 am

Beware that the forces will be transmitted to the bolt mounts now instead of deforming the ali.

Could he not use rusty corrogated iron for that macho look?

tut · Post by **tut** » Tue Nov 21, 2006 11:09 am

mmmmm, never thought of that.

Suppose the solution is not to scrape the undertray.

tut

ps anybody know for sure the purpose of the NACA ducts? I certainly do not need any cooling in that region with the Honda conversion, nor the oval cut out for the exhaust flexi section, as my manifold is at the back.

Post by **Shug** » Tue Nov 21, 2006 11:13 am

tut wrote:mmmmm, never thought of that.

Suppose the solution is not to scrape the undertray.

tut

ps anybody know for sure the purpose of the NACA ducts? I certainly do not need any cooling in that region with the Honda conversion, nor the oval cut out for the exhaust flexi section, as my manifold is at the back.

AFAIK, it was to waft some air at the sump and gearbox on the K series, as cooling was borderline. Shouldn't be too much of an issue as yours has an oil cooler - dunno about gearbox though.

Rich H · Post by **Rich H** » Tue Nov 21, 2006 1:33 pm

Idea I had a while ago was to have some spacers made up for the diffuser/undertray joint. this will give an air extraction point right at the back of the engine bay.

The spacer would have to be something like a U channel with slots in and either tapped for bolts or fitted with those little captive nut clips:

robin · Post by **robin** » Tue Nov 21, 2006 2:53 pm

tut wrote:mmmmm, never thought of that.

Suppose the solution is not to scrape the undertray.

tut

ps anybody know for sure the purpose of the NACA ducts? I certainly do not need any cooling in that region with the Honda conversion, nor the oval cut out for the exhaust flexi section, as my manifold is at the back.

Tut - if you get some rubber bushes to mount the tray to the car then this will provide both the spacing you Honda boys need and isolate the mounting points from knocks and scrapes. Also most impacts are more or less vertical and 1.6mm steel is hardly an RSJ, so I think it will still bend rather than overstress the mount. The C-clips at the sides will just slide about when stressed, so no real worries there I think.

Anyway, the sort of bush I am thinking off is something like 385-1609 at rswww.com

I think that the ducts are there to extract hot air from the engine bay and feed into the flow under the car; I suspect they are positioned so as to remove hot air from around the exhaust manifold and downpipe. If I were going to put these in on your car I would position it underneath the point where the manifold meets the head.

Cheers,
Robin

tut · Post by **tut** » Tue Nov 21, 2006 4:33 pm

Thanks Robin.

I was using old rubber bushes at one time, but they got lost along the way as different people took the undertray off, so ended up with none.

As we are replacing all nuts, bolts, screws etc on the clams and undertrays with S/S, I will also order some of the rubber bushes from rsww.

tut

hiscot · Post by **hiscot** » Tue Nov 21, 2006 6:06 pm

I think the ducts draw air up into the engine bay so heat can be expelled through the boot lid just using holes wont draw as good ( a bit like a chimmely with paper across )
if it was me I would fit extra nact ducts they are not expensive

tut · Post by **tut** » Wed Nov 22, 2006 12:54 am

Thanks, they are listed with a part number in the Parts List, I thought that they were integral with the tray, so will check with MMC tomorrow.

tut