UK Bonnet Scoop

Whilst discussing if the active spoiler affects MPG I cited the official brochure regarding the UK bonnet scoop, which stated it "...directs cooling air through the exhaust manifold to improve fuel consumption at high speeds".

 

My question therefore is has anyone ever noticed this? Has anyone added one to a JDM and gone "Wow look how much fuel I'm saving now"? Or did Toyota really add the scoop to make it more aesthetically pleasing to the UK market? Or was it actually needed to compensate for some of the other UK changes like different turbos?

 

One thing I do know is a UK bonnet with a scoop is considerably heavier than a JDM bonnet and that can't be helping fuel consumption!

I would have thought the drag would have slowed it a bit too - a friend has a Jspec though, and always said she was more economical at speed, so could be some truth in it..

Have any J-Spec owners fitted the associated "snorkel" to do the air redirection though? Just fitting the cosmetic part won't give you the effect Toyota added it for.

 

Might be better to approach this from the angle of a UK owner swapping their bonnet for something else but I suspect mpg isn't something that concerns most of us at 100mph+

I added one to mine and it still drinks the juice as heavy as before but it was after the fuel price rise so not really fair comparison I guess.

I can't see how it would make any difference.

 

To increase efficiency it has to either

 

1) improve in cylinder burning - I doubt this as it diverts air over the exhaust

 

2) recuce drag - Unlikely as it is routing air from a low pressure area (on the bonnet) to a more low pressure area (under the car). I can't see how this will improve aerodynamics

 

I always thought the UK scoop was there to aid cooling to the rear of the block / exhaust as there was an expectation of sustained higher speeds (similarly the additional gearbox cooler and diff cooler). Can't see how it would improve MPG either.

i fitted a uk scoop with all the ducting as toyota intended

 

the only difference i saw was the boost raised,so had to adjust my boost controller get get back to where i was beforehand.

 

may be a coinsidence that something else affected the boost.

 

or is it that the under bonnet temps where reduced

I always thought the UK scoop was there to aid cooling to the rear of the block / exhaust as there was an expectation of sustained higher speeds (similarly the additional gearbox cooler and diff cooler). Can't see how it would improve MPG either.

 

Thats correct, on early mule car tests at sustained high speed were overheating the 2 back cylinders, so the bonnet vent was a bit of an afterthough, which shows really.

Would have thought the differences in MPG wouldnt be noticeable for driving at speeds where people actually care about MPG, much like the front active spolier.

 

Having said that, the best MPG I got from my car was doing an average speed of 90 odd coming back through Europe from Germany!

I get about 18 - 20 mpg from my UK spec auto - stock apart from BPU, ssqv, superdragger and rear sunshade spoiler. Running stock rims with RE71 bridgestones and Shell V-power fuel. I love the look of the scoop and much prefer it to j-spec bonnets (apart from 3000GT/TRD bonnet)

the only difference i saw was the boost raised,so had to adjust my boost controller get get back to where i was beforehand.

Well I suppose it is possible that by cooling the exhaust manifold you reduce the tempreature of the exhaust gases spinning the turbos, which reduces the amount the intake air heats up due to the heat of the turbos, and thus more power is produced. More power for the same amount of effort equals better fuel consumption. (Or just more power if you don't control your right foot!)

Thats correct, on early mule car tests at sustained high speed were overheating the 2 back cylinders, so the bonnet vent was a bit of an afterthough, which shows really.

If that was true then I would have expected them to make it common across the range when they produced the facelift. Do you have a reference to where this information came from?

If that was true then I would have expected them to make it common across the range when they produced the facelift. Do you have a reference to where this information came from?

 

There'd be no point putting it on a car that was limited to 112mph. I'm sure we've had these discussions before.

Is that a polite way of telling me to use the search?

 

So one can assume this over heating problem only occurs at speeds beyond the JDM limiter then. That would explain it only being added to the UK and I can understand why Toyota would advertise the scoop as a fuel saving device rather than publically admitting there might be an over-heating problem. What I am surprised about is the Supra was originally designed and made in Japan (correct?) prior to it being produced elsewhere like the UK, and we all know how car mad the Japanese are, so I would be surprised if they didn't encounter the problem much earlier on during the original testing phase. Assuming they did, it seems strange they ignored the problem given how much care and attention they spent on the rest of the car.

 

I suppose this over heating problem also explains why they chose to switch from ceramic to steel blade turbos too*. It must have been a lot of expense though for something that only happens above 112mph, especially in a market with a 70mph maximum speed limit and considering they previously ignored the issue.

 

* - For the purpose of this thread we are assuming that both JDM and UK Supras produce the same power and that, as proved by IanC, the UK turbo is not actually bigger than the JDM one despite popular belief suggesting it is.

It just comes down to a durability issue, for running on roads where technically you can drive flat out at 155 for a long time. Same thing with the turbos and diff cooler.

 

Its not just the UK cars that come with these bits, its EU models too.

 

I dont think the turbos are the issue either, as the US models have the same turbos as the UK/Euro specs and they dont have the scoop.

* - For the purpose of this thread we are assuming that both JDM and UK Supras produce the same power and that, as proved by IanC...

 

Do you have a link to the thread where Ian proved that?

If it was intended to cool the engine, would it not be better to duct the air up from underneath the car rather than what is coming though a hole with the area of a Cadburys Flake (sideways)

I think with the negative effect under the car air is sucked down through the scoop and out under the car, you wouldnt get that from ducting air up from under the car, or am i talking bo!!ocks here,

Oh, I haven't a clue how the airflow dynamic work, way over may head

Oh, I haven't a clue how the airflow dynamic work, way over may head

 

LOL, come on, just think of every other car out there with some kind of bonnet scoop

The JDM and export models were released at the same time and after the same development. Cant see the JDM market not having the scoops for any other reason than they are limited on top speed surely.

Slightly off topic, put does anyone have a link to the original brochure for the J Spec Supra. Mind you, thinking about it, it will be in Japaneese im guessing, so not much use!

*****