53 replies to this topic

[JG]

In stock too

[speedster]

Obviously it makes oil changes more complicated....

  No, oil access panel is on the main undertray not separate rear diffuser section.

No access panel on my under tray, early NA's didn't have them.

[Nev]

Looking for a diffuser which provides minimal visual impact with performance.

 

The OEM one has "minimal visual impact" and likely has the same "performance" as any of the after market ones. 

 

If you genuinely want to improve grip your best bet is to lower the front of the car and make a big solid splitter and then maybe a medium sized wing at roof height.

Edited by Nev, 07 August 2013 - 11:28 AM.

[FLD]

if you look at winstars CFD analysis in the premium section it shows why a diffuser on the Vx doesn't work.  The main tray needs fencing to stop losses into the rear wheel wells.   The only downforce a diffuser adds to a VX is its own weight no matter how far you choose to stick it out the back.

 

I very much doubt the tat would be an OEM fitment.  I believe it should really fail an MOT as a sheet metal protrusion is classed as dangerous due to the (potentially) sharp edge.

[speedster]

 

Looking for a diffuser which provides minimal visual impact with performance.

 

The OEM one has "minimal visual impact" and likely has the same "performance" as any of the after market ones. 

 

If you genuinely want to improve grip your best bet is to lower the front of the car and make a big solid splitter and then maybe a medium sized wing at roof height.

 

Thanks Nev. I prefer to keep the car in standard trim (body wise). When I start using her for hill climbs I'll see if a wing does anything.

The front will be lowered further (if possible), I already have her 20mm down on 16 inch rims.

 

if you look at winstars CFD analysis in the premium section it shows why a diffuser on the Vx doesn't work.  The main tray needs fencing to stop losses into the rear wheel wells.   The only downforce a diffuser adds to a VX is its own weight no matter how far you choose to stick it out the back.

 

I very much doubt the tat would be an OEM fitment.  I believe it should really fail an MOT as a sheet metal protrusion is classed as dangerous due to the (potentially) sharp edge.

Hi FLD. My understanding is it comes into effect at high speeds.... When the OEM design (sloped rear) actually starts to provide lift.  

 

rear protuding diffuser = leg slicer 

[speedster]

if you look at winstars CFD analysis in the premium section it shows why a diffuser on the Vx doesn't work.  The main tray needs fencing to stop losses into the rear wheel wells.   The only downforce a diffuser adds to a VX is its own weight no matter how far you choose to stick it out the back.

 

I very much doubt the tat would be an OEM fitment.  I believe it should really fail an MOT as a sheet metal protrusion is classed as dangerous due to the (potentially) sharp edge.

looks like a redesign of the under tray would be necessary for any real diffuser performance then?

[FLD]

Yup.  Or you could add on some side vanes easily enough.  Imagine some L-shaped pieces of alloy rivetted on. 

 

Editted for my hamfisted keyboard mashing resulting in poor spelling.

Edited by FLD, 08 August 2013 - 08:08 AM.

[Nev]

If you genuinely want to improve performance, try taking the OEM difusser off completely. That will give you the benefit of 6 Kg less weight over the rear axle and far better engine cooling which in turn may make more power, cooler runing gearbox which may well stop issues with that. The only negative is possible slight aero effects at very high speed. I (and a few others) have been driving like this and would recommend it.

 

[speedster]

If you genuinely want to improve performance, try taking the OEM difusser off completely. That will give you the benefit of 6 Kg less weight over the rear axle and far better engine cooling which in turn may make more power, cooler runing gearbox which may well stop issues with that. The only negative is possible slight aero effects at very high speed. I (and a few others) have been driving like this and would recommend it.

 

6 kg is a nice gain, anybody for a carbon fiber under tray?  How do you reckon better engine cooling will give an NA more power?

[techieboy]

If you genuinely want to improve performance, try taking the OEM difusser off completely. That will give you the benefit of 6 Kg less weight over the rear axle and far better engine cooling which in turn may make more power, cooler runing gearbox which may well stop issues with that. The only negative is possible slight aero effects at very high speed. I (and a few others) have been driving like this and would recommend it.

6 kg is a nice gain, anybody for a carbon fiber under tray?  How do you reckon better engine cooling will give an NA more power?

OEM diffuser is 1.6kg, TAT short is 3.2kg.

[Nev]

6kg saving is for the main tray and rear smaller tray combined BTW. Eliminating weight from the rear of the car is always more appealing than from the front too.

 

Surely even NA's get mild overheating when driven hard for long periods on warm days, though admittedly I am sure the problem isn't anywhere near like charged cars.

Edited by Nev, 08 August 2013 - 11:15 PM.

[FLD]

 

 anybody for a carbon fiber under tray?

 

http://www.vx220.org...oo-debate-nsfg/

 

Solid carbon stiff enough to make a tray would show little or no weight saving.  This one uses 3D core and saves 1kg over OE.  One with straight foam would save around 1.5-2 kg. 

 

I've found the 3D cored one overly stiff as you have to line it up just right on the sides.

[Andrew aka Stuwy]

6kg saving is for the main tray and rear smaller tray combined BTW. Eliminating weight from the rear of the car is always more appealing than from the front too.   Surely even NA's get mild overheating when driven hard for long periods on warm days, though admittedly I am sure the problem isn't anywhere near like charged cars.

I have no overheating issues in my SC with all trays fitted When I was N/A it was hard to get the engine over 100'c. Only giving it some beans and then stopping in solid traffic would cause anything heat wise

[speedster]

 

 

 anybody for a carbon fiber under tray?

 

http://www.vx220.org...oo-debate-nsfg/

 

Solid carbon stiff enough to make a tray would show little or no weight saving.  This one uses 3D core and saves 1kg over OE.  One with straight foam would save around 1.5-2 kg. 

 

I've found the 3D cored one overly stiff as you have to line it up just right on the sides.

 

ohhh! nice!  I'll have to go get Competition Car-Composites Practical Guide from my bookshelf

http://www.amazon.co...ref=pd_sim_b_37

Don't suppose you have a nice dimension drawing of the mold on computer 

 

 

 

6kg saving is for the main tray and rear smaller tray combined BTW. Eliminating weight from the rear of the car is always more appealing than from the front too.
 
Surely even NA's get mild overheating when driven hard for long periods on warm days, though admittedly I am sure the problem isn't anywhere near like charged cars.

I have no overheating issues in my SC with all trays fitted

When I was N/A it was hard to get the engine over 100'c. Only giving it some beans and then stopping in solid traffic would cause anything heat wise

 

 98 degrees is in and around the max I've ever seen and I ain't no cruiser... edit though I do now recall seeing 102 on an occasion

Edited by speedster, 09 August 2013 - 08:58 AM.

[FLD]

 

 

 

 anybody for a carbon fiber under tray?

 

http://www.vx220.org...oo-debate-nsfg/

 

Solid carbon stiff enough to make a tray would show little or no weight saving.  This one uses 3D core and saves 1kg over OE.  One with straight foam would save around 1.5-2 kg. 

 

I've found the 3D cored one overly stiff as you have to line it up just right on the sides.

 

ohhh! nice!  I'll have to go get Competition Car-Composites Practical Guide from my bookshelf

http://www.amazon.co...ref=pd_sim_b_37

Don't suppose you have a nice dimension drawing of the mold on computer 

 

 

 

 

 

It was a sheet of chipboard with bits glued on / routed out and then covered in vinyl.  Nothing high tech at all!

[Andrew aka Stuwy]

 

 

 

 

 anybody for a carbon fiber under tray?

 

http://www.vx220.org...oo-debate-nsfg/

 

Solid carbon stiff enough to make a tray would show little or no weight saving.  This one uses 3D core and saves 1kg over OE.  One with straight foam would save around 1.5-2 kg. 

 

I've found the 3D cored one overly stiff as you have to line it up just right on the sides.

 

ohhh! nice!  I'll have to go get Competition Car-Composites Practical Guide from my bookshelf

http://www.amazon.co...ref=pd_sim_b_37

Don't suppose you have a nice dimension drawing of the mold on computer 

 

 

 

 

 

It was a sheet of chipboard with bits glued on / routed out and then covered in vinyl.  Nothing high tech at all!

 

 

did you just draw round your under tray?

 

though it would be more complicated then that

[TazN]

I guess that would give you the silhouette but iirc it has some different thickness parts around edges...

 

I keep thinking about possibly making a new undertray as mine has some huge scrapes on it and is a bugger to line up correctly now so have given up trying

[PaulCP]

Tried fitting the short TAT on mine earlier this week and no way is it going to go on without spacers due to the brace bar. If it doesn't look right with home made spacers when I get round to doing it again (which will be the limit of my patience these days) it will be in the "for sale" section

[myles]

Tried fitting the short TAT on mine earlier this week and no way is it going to go on without spacers due to the brace bar. If it doesn't look right with home made spacers when I get round to doing it again (which will be the limit of my patience these days) it will be in the "for sale" section

Keep me posted on that one. Not that I don't wish you luck with the fitting though!

[FLD]

 

 

 

 

 

 anybody for a carbon fiber under tray?

 

http://www.vx220.org...oo-debate-nsfg/

 

Solid carbon stiff enough to make a tray would show little or no weight saving.  This one uses 3D core and saves 1kg over OE.  One with straight foam would save around 1.5-2 kg. 

 

I've found the 3D cored one overly stiff as you have to line it up just right on the sides.

 

ohhh! nice!  I'll have to go get Competition Car-Composites Practical Guide from my bookshelf

http://www.amazon.co...ref=pd_sim_b_37

Don't suppose you have a nice dimension drawing of the mold on computer 

 

 

 

 

 

It was a sheet of chipboard with bits glued on / routed out and then covered in vinyl.  Nothing high tech at all!

 

 

did you just draw round your under tray?

 

though it would be more complicated then that

 

 

Pretty much.  I used a router for the side bits that are doglegged lower than the main tray.  I used a piece of strip wood bonded on for the angled bit at the back and a profiled piece for the hook at the front and covered it all in vinyl.  It was a one shot mould, didn't need to be fancy, just needed to cope with vacuum.