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wardy18

[misc_work] Project 205 Diffuser

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wardy18

I was actually thinking this :lol:

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wardy18

Quick calculations while sat at my desk at work, if i were to have a 90cm long upsweep on the diffuser at 7deg i would have about 65mm height at the back of the diffuser, that aint much is it!!

 

90cm will take me approx just behind the beam and come level with the back bumper (obviously lower down)

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welshpug

you'll need to extend your bumper further down then wont you :lol:

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Cameron

Can't you start the diffuser further towards the front of the car?

 

7 degrees isn't the magic number people have made it out to be! There's plenty of scope to increase the angle, as I said you can easily run 10 degrees without detrimental effects and you can run up to 15 deg. The lift coefficient (hence amount of downforce) you'll get will increase with diffuser angle, but so will drag. This isn't an F1 car so you don't really have to worry about high speeds so much as you'll very rarely be seeing over 100mph.

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wardy18

If i started it further towards the car then the beam clearence starts to become an issue, i would need to sit the tray lower to the ground and at the moment its level with the bottom of the tub, i mean i can drop it by say approx 20mm but wouldnt want to do much more than that.

 

That's as i said earlier, high speed affects are not an issue for me, even at the qtr mile sprint with the old engine i was only hitting 95mph.

 

Ill have a play this afty and see what i come up with and post up results later

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Rippthrough

As others have said, that's far too steep to keep the airflow attached, I'd suggest going with Camerons idea and getting it starting much further forward, ideally half way down the car but that's not going to happen so you'll have to settle for a shorter, shallower setup.

You can run more than the magic 7 degrees provided you use a proper curved setup rather than a straight angle, but the length is your main issue, make sure it extends out behind the car by a few inches to get the airstream clear of the bodywork and it might just work well enough.

It's never going to make oodles of downforce so I'd concentrate less on a huge angle and more on clean airflow and low drag levels, so it might be an idea to turn the outer edges of the flow into the void behind the rear tyres.

 

Depending on the regs you have to run to, if you've got rid of the fuel tank I'd be tempted to chop and sheet metal the rear footwells in if you want it to make serious downforce, you'd have to panel the beam in and use it as a small wing or for flow control though.

Edited by Rippthrough

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wardy18

Ok i have taken everything on board and come up with the following

 

This is where the diffuser will sit at the back, will secure under the fog light section of the valance which is 27.5cm of the ground, the exhaust will exit above the diffuser in the gap as shown, the remainder will be filled with mesh around the exhaust end pipe.

 

 

 

Now see the dimensions as follows, the cars floor pan sits beween 14 and 15cm off the ground so this is the base at which the diffuser much lift a 7deg at the back. As stated above the point at which the diffuser secures to the valance is 27.5cm of the ground and so i cant afford for anymore upsweep lift in the diffuser than 13.5cm. This means at 7deg the section of the diffuser which sweeps up must be 108cm long and a further 17cm flat section to meet up with the floor pan.

 

(Widths yet to be determined)

 

 

 

 

 

How's does this look?!

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wardy18

Have just also worked an alternative, I van have the centre section at 10deg which will stretch 111cm and lift approx 22.5cm, this would fill the centre void I have in the bumper and I can then place the exhaust under the diffuser between it and the ground, the outer diffuser would remain as per previous spec at 7deg!

 

I think I would prefer this set up!

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Tom Fenton

The exhaust being below the diffuser ruins the point of having it.

Get the exhaust above.

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Cameron

Yeah you shouldn't stick the exhaust in the airflow because it'll reduce the peformance of the diffuser, stick it above like Tom said. If you can't stick it above, you could have it in the centre and have a couple of strakes to guide air around it, a bit like this:

 

F430_press-rear.jpg

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wardy18

Im going to have to box the exhaust in anyway, as it comes over the beam it will protrude into the diffuser and then go above it.

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Cameron

Fair enough. It shouldn't hurt the performance as long as you're clever with your ducting.

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wardy18

Im racking my brain as to how i can stop airflow going above the diffuser with the exhaust, because the exhaust will be boxed in with the diffuser over the beam there will always be airflow going above the diffuser from the exhaust entry point into the diffuser unless i start boxing in the whole exhaust system from the front floor tray but then i really feel this will hold in too much heat.

 

See the following image of a side on disection of how i see the exhaust boxing in over the beam going and see the airflow issue:

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Cameron

I think the only way you can stop that happening is to run a complete flat floor from front to back.

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wardy18

Just how much do you think a full body undertray will be of advantage to me in my division of motorport with regards to uninterupted air streams and downforce?!

 

I know the weight will be low down BUT at the end of the day its still going to be an extra say 5 to 8kgs extra for a full undertray and in circuit racing this is fine because your only using engine torque to get it off the line once and the cars faster momentum will do the rest but for me on hillclimbing weight is crucial id say!!

 

What you think?! Would the gains outweight the weight increase?!

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Cameron

I think if you're considering fitting a diffuser and splitter then you'd be nuts not to consider a full flat floor too. It will improve the efficiency of both for a start, and also eliminate your problems of sealing the leading edge of the diffuser. If you were to make it out of sheet aluminium I can't see it weighing that much, maybe 5kg at the most if you used really thick stuff.

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omega

i dont know if you will get any gains but you have done a lot of work so why not try it and if it doesnt work you can always take it off,i suppose the only way you will know is with 2 back to back runs on the same track one with and one without.

think what you have done so far is fantatic ive read with intrest.

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wardy18

Im convinced, full flat undertray it is, only biggest problem is side skirts really, i need side skirts which step out from he sills 5cm a the back and 6cm at the front so they come level with the bottom of my arches and they need to mould specially to the bottom of the arches contours, ill need to buy a bog standard set of side skirts and adapt, would look great though huh?! It'll look like a BMW DTM Motorsport kit once finished and is for practicality not look. Will also need some small rear valance corner splitters and need to extend the rear of the rear arches down the valance as they currently stop at the bottom of the bumper.

 

LOTS OF WORK :lol:

 

 

Anyways the latest of the diffuser, i have a dilema, what is more important - Undisturbed Air Flow OR As long as possible 7deg diffuser length?!

 

It seems the Damper mounting points are the lowest point under the car, so (OPTION 2) if i had the 108cm length 7deg diffuser i would have to box the diffuser over the Damper mounting points and so it wouldn't be a flat diffuser. Whereas (OPTION 1) i could start the 7deg diffuser at the damper mounting points so giving me a completely flat undisturbed diffuser but will only be 79cm long and width would be from 76cm opening at the back to 107cm.

 

Hopefully that makes sense, see the pic for more clarification.

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DRTDVL

As rangi as it might sound...

 

I know a few people here that have used the plastic house guttering as sideskirts with very minor mods...

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Cameron

I wouldn't worry about the dampers to be honest, they're only a very small protrusion at the edges, I'd start your diffuser before the dampers as you'd planned then position your vertical strakes next to the dampers to sheild them from the airfow. That way you'll end up with a nice wide central section of smooth flow. :lol:

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wardy18

Is this what you mean?!

 

If so then looks like the best plan to me, i have started so the centre strakes wider a the front narrowing to the rear so as said previous they speed up the air into the 7deg diffuser.

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projectpug

very interesting project , will read with interest. If you come up with a product to sell from this i am definately interested.

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wardy18

Definitely like to be reproducing this in fibreglass

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