IL Motorsport 4-1 Header

A while back I purchased the IL Motorsport 4-1 exhaust header directly from IL Motorsport in Germany, just a few minutes after it became available again on their store.

At the time I had researched extensively all the available options, and while the IL Motorsport (reportedly BBK supplied) header wasn’t the absolute best option, their reputation with fellow MX-5 owners, along with the affordable price tag and versatility sealed the deal.
If I had to purchase a header today, I would go with the 4-1 Long Header, engineered by PPE Performance according to the 2012 SCCA championship rules in USA. Those headers have nice long primary tubes that go well beyond the stock junction between manifold and mid-pipe (for this reason they are bundled with a custom mid-pipe), which reportedly deliver more torque in the mid-range without affecting the high-velocity flow near the redline (as a 4-2-1 header would do).

Anyhow, everyone was happy with the 4-1 headers, and I must say everything I have read is true. These babies don’t spoil low end grunt, in fact they open up the engine all the way down to 3000rpm. It doesn’t feel stronger (or weaker) than before… but boy do I find myself surprised at how the speed builds up! I can now step on it in 6th gear where I had to drop down to 5th or 4th to overtake!
All in all this is a great upgrade for the MX-5, it makes the engine finally come to life above 5000rpm (everyone who has driven the 2.0L knows just how unwilling the engine appears to be when you push it up to the redline). The 3500rpm hole is gone too. The car feels sportier, better. The gas pedal is more responsive, and you get a minor sound improvement. People that would rather stick with the sound of the stock exhaust can happily purchase this header and have the ECU remapped, to see their Miata’s come to life (it looks like we’re talking about a 10% increase in peak torque and horsepower, but I never look at that… what you feel is what counts, and this feels GOOD). Not revolutionary good, but it is a pleasant improvement nevertheless.

While I was at it, before installing it, I purchased the required material to do a professional grade wrap. In this case I had to purchase from Poland, since this kind of (serious) stuff isn’t readily available in Italy. I got a roll of black 2.5″ wrap, a can of black spray silicone sealant and a set of stainless steel straps, all Thermo-Tec Cool-It! with a continuous 2000°F spec.
I first sprayed 4 layers of sealant on the bare stainless steel (after cleaning the surface with solvent).

I let the sealant dry for 1 hour between layers, then a couple of days before wrapping it.
I only treated the surfaces that I was going to wrap, to seal the micro-imperfections of the stainless steel, to avoid corrosion.

Then I carefully wrapped the primary tubes. Unfortunately I had to go across the 4 tubes together where they ran parallel. No clearance whatsoever. To apply to wrap you must first wet it in lukewarm water (I’ve heard and seen many people avoid wetting the wrap to save time… this is totally unprofessional, and one of the main reasons so often you hear about people having to re-wrap their exhausts after a few months). This ensures you tightly apply the wrap.. but requires an additional 5-7 days for the wrap to fully dry out, before you can apply the sealant to it (yes, the same one I used on the stainless tubes themselves).
Many installers will avoid sealing the wrap too… I really don’t understand how these people can ask for money to do such a poor job (just to name names, the Harley Davidson’s shop in Turin).

Here is the finished header, sealed, wrapped, strapped and sealed again.

Onto the installation now!!

It took a total of 7 hours to do the job, taking it easy, creating cable extensions for the front and rear sensors and riding down to the store for supplies and beer.
The stock exhaust manifold (once the heat shields are removed) is of very good build quality, this one here is 7 years old and shows no signs of failure, only superficial rusting that is to be expected.

The only real issue with the stock manifold is the crimped headers where they join before the catalyst… That’s a horrible design!
I can tell you, the car responds so much better without that! (the liquid on it is a squirt of engine coolant that came out when I rerouted the pipe that runs above the headers in order to gain access)

Notice the difference between the stock manifold and the new free flow headers. A part from the missing pre-catalyst in the replacement unit (which will indeed contribute to the better response of the engine), the length of the mandrel bent primary tubes is the key here.

In the end I decided to go with the new single-use gasket (soft type), since I didn’t find the head plate of the IL Motorsport headers to be good enough to go with the stock gasket.
It’s a pity because the stock gasket had an upper lip that shielded the timing cover, which is made of plastic. Not a big problem, since I wrapped the header (no direct irradiation, and a very effective isolation).

The new headers fitted, retaining the upper stock heat shield.
I am very pleased with the result, and the Thermo-Tec Cool-It! treatment is very effective in keeping things cool around the pipes. I purchased a fire extinguisher nevertheless, just to be on the safe side :)

As I anticipated above, the butt dyno tells me the car feels more sporty. It feels like I unscrewed a cork that was capping the exhaust!

With the stock exhaust main catalyst, mid-section and muffler still on, the sound hasn’t changed much. It’s deeper, and floods the cabin a little with the roof up, but from the outside it’s virtually the same as stock.

A friend of mine has a bone stock Miata (2006 as mine) and had it mapped, to gain pretty much the same results in terms of power delivery… I’m curious to see how a nice map will work on my Miata after I am done with the exhaust!

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