2bular Vs. Hangar 111
Below is the Hangar 111 manifold for the 2ZZ installs. It was fitted to a supercharged 2ZZ! A short, 4-1 design with a head-flange only 6mm thick. It is made of mild-steel and already rusting. It is also seriously warped after the primary pipe-to-flange weld. Not good. I was informed of another H111 manifold which just would not seal at the cylinder head and had to be returned. No re-fund, only the supply of another manifold.
The pipes are quite badly rusted too. They are not Austenitic 300-series Stainless - they are Type 409 stainless - a lesser grade barely qualifying for the designation of Stainless Steel. They are 18g - very thin given the stresses they have to endure on this install. The heavy, machined-from-solid mild steel 'collector' is not the best design I've seen for this purpose. This part weighs 1.5 x the rest of the manifold!
With that weight, the thin 409 pipework and the curious 4-holed plate closing the end of the 'collector' it's no real surprise that it broke after a few hundred miles! The whole fabrication is very amateurish in its design and fabrication. In my 33 years in the exhaust business, I've never come across anything like it. Of course, if it worked - if it improved the performance of the 2ZZ motor, all well and good! Sadly, testing on an N/A motor showed a loss of 15bhp.
Compare and contrast with the 2bular 4-2-1 manifold below. A Type 304 Stainless Steel long-branch design with proper 2-1 merge collectors, all TIG-welded. The 10mm thick, head-flange is also 304 Stainless. Built to perform, with minimum gains of 18 bhp and 16ft/lb of torque. 4-2-1 is the design used for the N/A motor. You have to use a shorter/larger-bore 4-1 for the supercharged installs!
With those longer primary pipes and matched secondaries, the exhaust note rises to a real scream when on the 2nd cam.
Lotus Stage2 Exhaust:
When I first heard this system, I thought it sounded fantastic. Although I wasn’t that keen on the tailpipes jusssssst poking through the diffuser and the owner advised me he had to trim the diffuser panel for clearance on those 89mm diameter tips.
Once I had a drive in a 111R with it fitted, I soon changed my mind. The dronnnnnne was horrendous.
We got the car up and checked the layout. The silencer was 5”diameter(!) – pretty damned small for a 170bhp motor.
The big tips certainly contributed to the dronnnnnnne and cutting open the silencer showed a very small bore perforated tube with poor quality packing materials.
Standing back I could see this was designed by a firm experienced in mild-steel exhausts but the 300series stainless used in modern aftermarket exhaust systems has a co-efficient of expansion 1.5 x that of mild-steel. It MOVES - a LOT - when it’s hot AND it shrinks a LOT when it cools. If you don’t take account of those properties – in other words, allow the construction to expand and contract and don’t try and tie it down, you’ll be fine.
However, inexperience can lead to stuff like this –
And this –
You see those mild-steel hanger rods? Always a bad idea to mix mild and stainless. A pet hate of mine – along with the horrible stretched pipe used as a 1-into-2 collector for the tailpipes. Just pull the two pipes together, use the squirt gun (MIG-welder) to fill in the gaps and slide the stretched pipe over them both. Weld what you can, then bash the middle down till it meets your fill-in weld. Seal it up – lovely! Urrrgh.
I recall Lotus dealers fitting this exhaust to the supercharged cars until they were advised in no uncertain terms NOT to do this. The bore is barely advisable on an N/A motor, never mind a supercharged beast.
However, I bet there’s some supercharged car owners out there still with this exhaust fitted to their pride and joy!