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The Fast and the Furious Re-Validated: Danger to the other Manifold

Illustration for article titled The Fast and the Furious Re-Validated: Danger to the other Manifold

(TL;DR at the end. I can get chatty)

Once upon a time, before I’d ever heard about Jalopnik, some folks made a series of movies about cars. It was largely beloved, although it had a tendency to put its foot in its mouth (For instance, claiming that the Nissan SR20 ever fetches a high price ever. This is not particularly true, proximity of race day be damned). The internet let many of these faux pas slide, but one seems to be a constant source of good cheer and chuckling. The film insisted that using “Stage 1” Nitrous Oxide injection was resulting in “Danger to Manifold”. Despite this warning, our hero activates “Stage 2” Nitrous Oxide injection, which is presumably more than Stage 1. His floor panel falls off. **SPOILER ALERT** He loses the race, the car totaled due to a missing floor panel.


On the heels of Barack Obama being elected POTUS, some well meaning Jalop posted an article regarding manifolds and anecdotal danger therein. Apparently, they say, the welds of an intake manifold can break.


I would contest that, if you are able to pressurize your intake with air to the point that the welds break, then it’s time to hire a new welder. Furthermore, after some recent study, I’m not convinced these guys were talking about the correct manifold.

A proper exhaust manifold, as you are all surely aware, guides the detonated air-fuel-nitrous intake mixture into the turbochargers and out the back of the car. This material is hot. Intake manifolds have been known to get hot, and sometimes, welds get weak after repeated heating-cooling cycles. The folks that design exhaust manifolds usually understand this, and most exhaust manifolds will last for a good long time...unless you get a bit creative with your air-fuel-nitrous mixture and/or your ignition timing.


You see, many car types enjoy Turbocharged cars (I enjoy them so much, I treat Turbocharging like a proper noun sometimes). Turbocharging is not without its downsides, however, as your uncle will undoubtedly tell you with some fervor. Between using strange terminology like “Glasspack”, “Carburetor” (I think more of these is better??), and “Posi-traction” (I only remember this from My Cousin Vinny), he’ll probably throw the term “Turbo-lag” in at some point too.

Turbo lag is bad. Without getting into the details, turbo lag can be avoided by keeping the turbo spinning. How can this be achieved? Either by driving like you’re playing Mario Kart (or like you are Polish), or via an aptly-named “anti-lag” system.


There are a couple types of anti-lag systems, but their purpose and method is essentially the same: keep the turbo spinning by causing much-hotter-than-normal exhaust gas to turn it.


Basically, in a normal four stroke engine, the second stroke causes compression. In between the second and third stroke, the charge is detonated, and by the time the fourth stroke starts, most (read: as much as possible) of the thermal energy has already dispersed, and the (still hot) exhaust passes through the exhaust manifold and into the turbo.

In an Anti-lag system, (depending on the type), either the ignition is retarded, and the charge detonation occurs later during the third stroke, or the charge is fed too much gasoline, meaning that there is gasoline in the exhaust. By adding air directly to the exhaust manifold, and due to its temperature, this exhaust material detonates a second time. Either way, the exhaust gas in the manifold is significantly hotter than it normally would be, and, for the same amount of strokes, spins the turbocharger faster.


TL;DR/Conclusion: Welds will become brittle and break when repeatedly heated and cooled, and will break faster if more drastically heated and cooled. Anti-lag will make your exhaust manifold a fair bit hotter. This, coupled with the massive turbocharger you applied, the Nitrous Oxide system you added, and time, will almost invariably cause “Danger to Manifold”. While the manifold is still good, however, you will be a total badass. I mean, look at this:

So, my friends, the next time you are watching/crying over Fast Car Movie #1, and they joke about manifolds, perhaps hold the chuckle back (or, redirect it at that shitty CarPC UI). Feel free to laugh heartily at the Eclipse though.


**Author’s note** Wow, SR20’s actually do fetch quite a price now. Drift tax I guess. If you are looking for a good engine, ignore that crap and get yourself an RB25DET instead. They are faster, have more cylinders, and come with a lifetime membership to the “Argue with people about the LS1” club.

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