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Old 8 Aug 2009, 13:41 (Ref:2517835)   #1
XKRacer
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XKRacer should be qualifying in the top 10 on the grid
Bonnet Scoop

Probably been covered before but dammed if I can find it!

I have made a scoop for the bonnet of my car as the main air intake for my TBs however I am told they become inaffective after speeds of about 80mph and I will have to do a rear scoop also in front of the bulkhead where the air rolls of the windscreen....Is this correct or is the guy talking b0ll0cks



If its true......not a problem just good to know?

Cheers
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Old 9 Aug 2009, 05:27 (Ref:2518223)   #2
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terence should be qualifying in the top 10 on the gridterence should be qualifying in the top 10 on the grid
Your right in your assumption,yes he is! Just make sure that once all of the lovely air is in there,that it can also escape,dont want the bulkhead acting as an air brake.
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Old 9 Aug 2009, 06:02 (Ref:2518231)   #3
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I think it is correct that you don't increase the pressure of the air going into the engine though, because that is limited by the induction process. What a scoop does is provide cooler air to the induction system which is therefore more dense.
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Old 9 Aug 2009, 07:21 (Ref:2518244)   #4
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Are you sure about that as according to Holley engineers who state in their book that the pressure ram effect can have bearing on performance, I will dig the book out later its fresh in my mind as I have just rebuilt a Holley 4 barrel carb and was using it down the garage.
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Old 9 Aug 2009, 07:22 (Ref:2518245)   #5
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phoenix should be qualifying in the top 5 on the gridphoenix should be qualifying in the top 5 on the grid
From the photograph it looks like their is a lip where you have cut the opening at the TB end of the scoop. You should really get rid of that lip and make the opening flush to the top, bottom and sides. That lip is likely to cause a huge amount of turbulance and drag if you leave it there.

To be controversial, I would say that not all air inlets need an outlet - particularly engine air intakes. F1 fars don't have an exit from their airboxes other than via the airfilter and into the engine.

Cooling ducts, on the other hand, do need an exit as you need a flow of cool air in and a way for the hot air to get out. The area inside the engine bay tends to be low pressure anyway, as are the wheel wells, so it will be difficult to increase the air pressure inside the engine bay and the pressure built up in the inlet duct will dissipate at the end of the duct where it opens into the engine bay. If you find any side effects of having the scoop, for example the bonnet bulges at high speed or if you notice that the cooling is not as effective because the radiator flow is impaired by the higher pressure under to bonnet created by the scoop, then add an exit too at the base of the windscreen, but it could be in the form of a simple gap between the rear of the bonnet and the scuttle panel.

If you don't suffer any consequential problems, you won't need an exit, as you are not looking for flow through the engine bay - just a supply of air ready to be sucked into the engine.

The high pressure area created by your scoop - by the well known ram effect - can be used to improve power, but to get that effect the scoop should feed into a saeled airbox that contatins the inlets to the TBs and is sealed both to the scoop and from the rest of the engine bay. If you do this you will likely need a re-map as more fuel will be required - and the demand for fuel will increase as speed increases because of the extra airflow, so you may end up with the car running slightly rich at low speeds.
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Old 9 Aug 2009, 07:24 (Ref:2518246)   #6
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Exactly what the Holley engineers were saying (older technology but in effect the same) and you would have to go up on the jet sizes.
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Old 9 Aug 2009, 07:49 (Ref:2518250)   #7
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Originally Posted by phoenix View Post
From the photograph it looks like their is a lip where you have cut the opening at the TB end of the scoop. You should really get rid of that lip and make the opening flush to the top, bottom and sides. That lip is likely to cause a huge amount of turbulance and drag if you leave it there.

I produced the bonnet as a plug and will take a mold from it and reproduce in carbon fibre and I am glad you mention the lip. That was put in to give it a bit of strength but would a PITA to mold so I will be loosing it

The bonnet itself will be acting as the 'lid' to my air box which will be sealed from the engine bay and another question was going to be 'would I suffer from excess air?' But it seems you have answered that question also.

My air box will go under the air horns which wil then be bolted back on, the sides and back will come up to meet the bonnet, this will have a rubber (probably very similar to a door seal) strip sealing to the bonnet



It will look something similar to this



The front of the box will be different as this wil meet up with the front of the scoop, inside the box will be some kind of filter/foam, I think you guys will get the idea


I have replaced the original ECU and havent had it mapped yet so everything I do now won't matter too much......(he says!)


Cheers for your help and any other tips you can give me will be appreciated
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Old 9 Aug 2009, 08:05 (Ref:2518255)   #8
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Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!
Fantastic looking car XK where will you be racing it?
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Old 9 Aug 2009, 09:21 (Ref:2518286)   #9
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phoenix should be qualifying in the top 5 on the gridphoenix should be qualifying in the top 5 on the grid
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Originally Posted by XKRacer View Post
I produced the bonnet as a plug and will take a mold from it and reproduce in carbon fibre and I am glad you mention the lip. That was put in to give it a bit of strength but would a PITA to mold so I will be loosing it

The bonnet itself will be acting as the 'lid' to my air box which will be sealed from the engine bay and another question was going to be 'would I suffer from excess air?' But it seems you have answered that question also.

My air box will go under the air horns which wil then be bolted back on, the sides and back will come up to meet the bonnet, this will have a rubber (probably very similar to a door seal) strip sealing to the bonnet
http://i559.photobucket.com/albums/s...gzman/ENG5.jpg


It will look something similar to this

http://i559.photobucket.com/albums/s...n/DCP_0025.jpg

The front of the box will be different as this wil meet up with the front of the scoop, inside the box will be some kind of filter/foam, I think you guys will get the idea


I have replaced the original ECU and havent had it mapped yet so everything I do now won't matter too much......(he says!)


Cheers for your help and any other tips you can give me will be appreciated
You seem to have most things covered, but Tip 1 would be to make sure the air filter is free flowing and has as large as possible in surface area, to reduce pressure drop and improve power. A lot of F1 teams use K&N flat panel filters.

Tip 2 is think about water; remember in China a couple of years ago F1 engines cars were actually stopping because of too much water in the air filters? If you can create a water trap, i.e. make the air go through a kind of down then up 'S' bend between the scoop and the inlet trumpets, then that should help. At the very least you will need some kind of deflector for the water droplets to hit so they fall out of the airflow.

Last edited by Adam43; 9 Aug 2009 at 11:55. Reason: picture dupe
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Old 9 Aug 2009, 11:17 (Ref:2518328)   #10
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Fantastic looking car XK where will you be racing it?
For now I am just going to do track days, local to me is Snetterton I am booked for Marham in November not sure if I am going to make that but we shall see.....fingers crossed and all that
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Old 9 Aug 2009, 13:04 (Ref:2518353)   #11
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Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!
Good luck with it, it certainly looks like it will be fun.
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Old 10 Aug 2009, 23:41 (Ref:2519240)   #12
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Originally Posted by XKRacer View Post
Probably been covered before but dammed if I can find it!

I have made a scoop for the bonnet of my car as the main air intake for my TBs however I am told they become inaffective after speeds of about 80mph and I will have to do a rear scoop also in front of the bulkhead where the air rolls of the windscreen....Is this correct or is the guy talking b0ll0cks

If its true......not a problem just good to know?

Cheers
If it were further back towards the windscreen I think he may be right, although where you have it looks pretty good, BUT, the only way to really tell (for plebs like us without professional resourses)would be for you to do some wool tufting. A track day is perfect for that.
As far as the rest of it, you can create a significant effect with ram charging, and with Carbies this is very hard to guage because they work on the basis of 1 tune.
However, you have a computer, I presume it is modern so it has 3D, so it will have a MAP sensor input, along with the TPS, this will adjust the fuel for any ram effect, positive or negative. The colder air you are getting will probably make up for a small vortex if that is shown from tufting
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Old 11 Aug 2009, 07:17 (Ref:2519320)   #13
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Originally Posted by Notso Swift View Post
If it were further back towards the windscreen I think he may be right, although where you have it looks pretty good, BUT, the only way to really tell (for plebs like us without professional resourses)would be for you to do some wool tufting. A track day is perfect for that.
As far as the rest of it, you can create a significant effect with ram charging, and with Carbies this is very hard to guage because they work on the basis of 1 tune.
However, you have a computer, I presume it is modern so it has 3D, so it will have a MAP sensor input, along with the TPS, this will adjust the fuel for any ram effect, positive or negative. The colder air you are getting will probably make up for a small vortex if that is shown from tufting

Wool tufting?........that does ring a bell I have heard of wood shavings being used before to show where/how the air is running, could you let me know how this works

Thanks
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Old 11 Aug 2009, 07:55 (Ref:2519347)   #14
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http://autospeed.com/A_108656/cms/article.html

There is a series of 5 articles for you. This is a pretty good site for DYI, lots of road based, but OK overall.
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Old 11 Aug 2009, 15:11 (Ref:2519607)   #15
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Kinda looking forward to driving down the track looking like a pom pom

Very informative definately have a go with that especially regarding my rear spoiler as I have made it adjustable be good to see how that works!

Thanks
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