I added extractors to my 1hz and achieved a 15% increase in power at 70kph while on dyno test. I have since put on a sports muffler and a new tail piece (the Toyota one is flattened as it goes over the rear axle and it doesn't need to be). This has achieved an extra increase in pulling power although I've not had a dyno test since the new exhaust was fitted. When you get the extractors done it is MOST important that whoever does it replaces the vibration joint in the system. That is the plaited stainless steel bulge in the exhaust system that is visible behind the front rh wheel (drivers side in Oz). This vibration joint needs to be moved to fit the extractors but the bloke who did mine didn't replace it. Result was the muffler rattled itself to pieces inside 6 months.
So the exhaust people fitted a new one where the first resinator is positioned and discarded the resinator. You dont need it, and diesels fill the resinator up with soot and choke the motor. Hence the new exhaust system. The sports muffler is much flatter than the original and doesn't hang down nearly as much to snag those rocks we insist on driving over. Besides it has a nice throaty sound. Hope this helps
> Extractors (headers to our USA friends) do work. It of course depends
> on the standard manifolds etc. Turbos can have extractors leading to
> the turbo.
Turbos rely on maintaining a pressure drop before and after the unit itself. Whilst the manifold from the head to the turbo isn't critical (since the turbo is usually mounted within a couple of feet of the head), the rest of the exhaust system is. If you have back pressure from the exhaust, you're limiting the pressure difference, hence limiting the volume of gasses that can pass through the turbo. That's one reason why turbo'd cruisers can benefit from a free flowing exhaust. The stock system is quite restrictive.
That said however, Toyota have restricted the exhaust on purpose. What they're after is big boost down low and actually have it drop as you rev. It ensures the motors hang together when under high load. It is tempting to bolt on a bigger exhaust and for like $800 Aus, you can get a 4" SS system that adds a good 20% more power.
On a standard diesel, adding a bigger exhaust and extractors will offer a good (read noticable) power increase, but you do run the risk of sucking oil up through the piston rings. As far as I'm concerned, this isn't a bad thing since you end up putting a better lining of oil on the cylinder wall, but you do need to keep an eye on the oil level.
Beware that bolting on extractors and larger exhaust will increase the cabin noise. Early 1HZ 80's had fairly sparse sound insulation in the engine bay and you can hear the extractors. Later models were better insulated. As for the exhaust note....It's tight trouser time....