When you think hoodscoop, you probably think Subaru WRX STI, Dodge Challenger Hellcat, maybe Corvette ZR1 or Ford Mustang GT500. All of these cars use scoops for the same reasons: either to assist with cooling some kind of fluid (i.e. they send air to a heat exchanger filled with intake air, coolant, or oil, or these scoops can actually be vents that exhaust air to improve cooling/aero) or they’re part of the engine’s air intake. That’s what hood scoops are for: They help the engine breathe or they help the engine keep its fluids cool. But there is one hoodscoop that does something totally different, and I’m still having a hard time wrapping my head around how ridiculous it is.
My mind is being blown right now. As you may have read in James Gilboy’s piece today about the mid-90’s Toyota Celica GT4 (a WRC Rally homologation car not sold in the U.S.), the vehicle featured a tiny hoodscoop to cool the freaking timing belt.
When I first read it, I did not believe it. But then I found a February, 1994 press release by Toyota titled “Toyota Introduces Newly-Remodeled Celica GT-Four Limited Edition WRC Model Also Available,” and here’s what’s in it:
Design
With its diagonal mesh grids and large central “power” bulge, the new all-aluminum engine hood emphasizes the GT-Four7s potent, sporty looks.
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Use of aluminum reduces hood weight by about 8kg
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Center-right air-inlet maintains highly efficient cooling of the timing belt in severe running conditions
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The large right and left air outlets improve cooling efficiency inside the engine compartment
What the hell? How? Why?!
The hood scoop in question is this tiny one on the ST205-generation Toyota Celica GT-Four.
Here’s a closer look thanks to YouTube channel “furiousdriving” (check out their review here):
But how exactly does this hole flow air to the timing belt? This photo from a Cars & Bids auction shows a square-shaped outlet under the hood:
That square opening meets up with this square-shaped seal at the top of a duct on the turbocharged 2.0-liter 3SGTE engine:
But does that duct actually feed air into the timing belt? It loos like it’s a few inches away from the cover. This eBay listing for a 3SGTE engine gives us a good look at the duct:
You can see in the image that the duct appears to reach over the valve cover and down, toward the back of the engine. Here you can see that the duct appears to mount between that valve cover and the engine oil fill location:
If you look at how these 3SGET motors are set up, that’s all one piece — the valve cover includes the oil fill:
As you can see in the image above, there is no hole in that valley in front of the oil fill other than the spark plug hole, and obviously Toyota isn’t feeding air into a spark plug hole, which means this duct must be sending air outboard toward the timing cover. And indeed, in this photo, you can clearly see that there’s some kind of flat black piece between the base of the duct and the timing cover – presumably it’s a plastic extension that connects the two, allow air to feed into timing belt area:
I found a video of someone doing a timing belt job on their GT-Four, and I don’t see exactly where that duct feeds the timing belt; here you can see the timing cover off, but no clear hole for the air from the hoodscoop:
But then I found this old listing for a GT-Four timing duct itself:
If you look at those two mounting holes, they line up with the two elevated ones on the valve cover, just above that spark plug. It’s clear that, though we can’t see it in the screenshot above with the timing cover off, there must be a hole where the end of this duct enters the timing cover area from above to cool the belt.
Why did Toyota feel the need to cool a timing belt? I have absolutely no idea. I’ve never heard of anything like this, which makes this without question the craziest hoodscoop of all time.
Does Project Binky have one?
“I think we overestimated the need of cooling for engine bay area” – Probably some Toyota designer when reviewing GT4 to help designing GR Corolla
That is wierd.
Us spec legacy turbo had no intercooler so it’s all turbo cooling. Jdm legacy turbo of the same time was water/air so I assume turbo cooling was also the goal of the hoodscoop.
Please note cooling issues existed because a head was wrapped in exhaust pipes and hot oil was dumped into the head from the turbo.
Its official Japanese name is グローリーホール
Umm… Maybe not here?
Only thing I can think of is that is that in actual rally conditions, where there may be lots of high-throttle, low-speed drifting, that the under hood temperatures got pretty high. That coupled with sustained high-RPM operation possibly led to the timing belt getting excessively hot, requiring some kind of cooling solution, which then carried over to the production car.
Good point. I don’t know where the line was exactly with how much the street cars needed to share with the race versions, but that might be it.
10lbs of crap in a 5lb sack was one of the default problems of that era celica. I expect 300+ hp just made it worse. Imagine the thermal issues on any 90s car having 50% more power.
timing belts suck
From my extremely limited knowledge – it’s seldom the belts or chains that go wrong themselves due to stretching.
It’s the tensioners and guides that break, allowing stretched chains and belts to jump.
Tensioners and guides go wrong due to heat/cold cycling – making them brittle and prone to breaking.
I can’t tell – but my bet is that the vent is pointed at the belt tensioner.
That’s my best guess.
So what happens when Mr. & Mrs. chipmunk decide that looks exactly like a good place to raise Alvin, Theodore, and that other one that they keep forgetting the name of? Or perhaps store some walnuts in the timing belt cover?
Speaking of weird hood scoops, I bet hardly anyone notices the hood scoop on the Mercedes-Benz W123. The guys at the car wash were certainly surprised when it sucked up a towel.
Its not a normal timing belt, its a cool timing belt.
“Welcome to cool side of the timing belt”
– Billy Dee Williams
was that solely a Family Guy thing or did he also have a penchant for cool pillows in real life
timing belts are inherently not cool lol
Assuming Toyota wouldn’t do this unless there was a problem, please follow the recommended maintenance schedule for the timing belt on your GT-Four.
Since it’s a mid-90s Toyota, I’m assuming the maintenance interval of NEVER will be just fine?
Car Nerd: “Wow, cool, they’re cooling the timing belt – that must mean it’ll last a long time!”
Engineer: “Huh, they’re cooling the timing belt – that must mean it’s under a lot of thermal pressure and won’t last very long.”
Nobody is designing and building that scoop / duct setup unless there’s a reason for it. There’s even cost in just assigning the part numbers. This thing’s even going to need a different timing cover.
Right before I bought a house, I was Car Nerd, except it was about the intricate drainage system in the backyard. Right after the first rainstorm, I became Engineer.
I’ve found that perspective (“It’s like that because it has to be and this is the cheapest solution”) very helpful.
*When it comes to home repairs, etc the sentence ends with “…and they needed to spend 20% more than they did.”
The previous owner of my house worked in concrete. Concrete was his hammer, and he thought every house problem was a nail.
A friend of mine who owned an GT-Four Celica and he described it as one of the best looking cars he’s ever seen on a flatbed tow truck, because that’s where it normally was.
Wait, I thought the MR2 was the baby Ferrari?