High HP Airfilter Setup

[Bergerac]

I'm curious to see how people with higher HP engines (400+) have solved the air filter issue. I don't have a OE airbox and don't plan to buy one, there doesn't seem to be much room anywhere to install something big enough that will get a decent flow of cold air.

I was thinking of using the hole in the side of the engine bay and mounting a filter in the guard but there doesn't seem to be heaps of room in there either. I'm at the point of cutting the bracket off the lefthand headlight so I have some room behind it but I'm also not a fan of cutting things up unnecessarily.

[Thom]

I had to cut the LH headlight bracket ("windstopper") to route 3" piping through the hole down to the filter that I have located behind the air inlets in the bumper, making for a straight air feed. It is wrapped in the usual "stocking" to protect it from water exposure. Moving the horns somewhat backwards against the plastic wheel well was needed to free up the room required by the filter.
My car being a '90 it didn't come with the plastic brake cooling ducts used on '86/'88S/'89 turbos and I added the 968 set up shortly after purchasing it. I would guess that your S2 also didn't come with the plastic ducts.

[Bergerac]

No I dont believe it did, its a 90 as well.

Did you need to take the whole headlight bracket off or just one side? The other issue with the S2 is the ignitor bracket is in the way.

[Thom]

I cut the whole headlight bracket.

The igniter bracket is well lower than the piping in my car. I don't think you will have clearance issues if you make something similar.

[Bergerac]

So you have the same bracket on the wheel arch? Must be an 89+ thing, haven't seen it on the earlier cars.

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I was trying to maintain 3.5" because the turbo inet is 4" but I think 3" it going to be the way to go.

[Tom]

So you have the same bracket on the wheel arch? Must be an 89+ thing, haven't seen it on the earlier cars.

PXL_20250416_023759140.jpg

I was trying to maintain 3.5" because the turbo inet is 4" but I think 3" it going to be the way to go.

I thought Thom was talking about the brace/bracket thing on the back of the headlight bucket? The one that prevents the headlight from pushing back too much at speed. I cut mine off too.

[Bergerac]

Yes theres a couple of brackets in the later cars that get in the way, Im dropping mine at my fabricator to see if he can work around the headlight bracket, if not well cut it off, the ignitor bracket (in the pic above) was getting in the way of me putting a filter behind the headlight but Im going back to my original plan of mounting behind the guard, we had another look today and its the better way to go.

[Thom]

I was talking about both brackets

I have settled on 3" piping which easily clears the S/S2 igniter bracket (which is there on later turbos even if it serves no purpose). At this level of uprades anyway removing the igniter bracket may be far less of a concern than anything else. Cutting the windstopper is annoying as in my case the pop up headlight always shakes a little when driving at night and I wish I had a solution to this.

Considering how tight already 3" elbows of "standard" radius can be cut and made to fit in the fender from the hole to the lower area in the bumper I would doubt that 4" piping would fit cleanly.

[Bergerac]

Hopefully we can make it work with only cutting one side off the headlight bracket, the shaking would annoy me.

4" definitely wont fit, 3.5 tube just goes through the hole but a 3.5 silicone elbow wont. I already have the 4 to 3.5inch offset reducer on the turbo to clear the alternator so Ill try 3.5 first. I just need to get enough tube into the guard to get a silicone elbow onto it so I can mount the filter right behind the air inlet in the bumper, I may have to make a small shield for the worst of the water but the car rarely gets driven in the rain, mainly because it rarely rains here. The horn will have to move as well but that's not a big deal. Using something light this should give us the radius bends we need to make it work.

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The plan was always to leave the car in the state that if the motor blew up the S2 motor can go back in without too much trouble so ill avoid modifying the ignitor bracket if possible, cutting or drilling out spot welds in the guard will be a rust magnet at any rate.

[Thom]

If the engine goes pop wouldn't it be "easier" to actually rebuild the S2 engine to the same spec rather than undo all the other modifications made to the car?