Sagaris rear spoiler on a griff

[jesfirth]

Does anyone know if a sagaris rear spoiler will fit on a griff I.e. if the rear curve of both cars is similar?

I can have a small spoiler but not a wing under the tvcc regs so a full wing is not an option

I am also looking into a rear diffuser and undertray

To those who like their griffs unmolested I understand you view but please do not comment from an aesthetic perspective - i really dont want this thread hijacked. this is purely about airflow and rear down force for track use so looks are immaterial to me

Thanks. Jes

[jeboa]

It looks quite a bit more curved to me:



If you made a template of the Grif boot in MDF you could probably bend some clear acrylic to the correct shape, with the same concept as the Sagaris for some aluminium brackets.

[jesfirth]

Jerboa thanks good idea

[dumbfunk]

I did a mockup of a Jag XKR spoiler on a Griff for a different thread and it *looks* a possibility, even if for inspiration only but may be a little small for your purposes:

[jesfirth]

dumbfunk said:

I did a mockup of a Jag XKR spoiler on a Griff for a different thread and it *looks* a possibility, even if for inspiration only but may be a little small for your purposes:

That looks like a tidy solution I think you are right about the size. Matt has a spoiler that is about 150 mm on his griff which seems to work so perhaps a mixture of the two. I just had in look in my garage and realised that I have a spare griff bonnet which is curved and about the right width so I might chop that up add a couple of alloy supports and see if it works as a test.

Interestingly when you don't lock the boot the lid floats up at 85mph so there is considerable lift at the rear. I think form memerory when andy race put the spoiler wing on the rear of his griff he added something like 250kg downforce which is massive. I need a little less I think

[dumbfunk]

I conducted the same rear lift experiment pulling out of a German rest stop onto a derestricted section of autobahn much to the amusement of the SLK I *momentarily* belittled.

Ho hum, that's character I guess!

[7 TVR]

Hi Jes, have also chatted to Andy at length regards Aero and have conducted some high speed testing with both front splitter & rear diffuser!
The front splitter has made a big differance to high speed stability but i still feel the arse is getting to much lift.
I'm thinking of switching to a single exit exhaust enabling me to run the SC Power diffuser, as Precat has had good results on the road and Andy proved its worth on track!
I would be interested in what you come up with!!

[450Nick]

As I understand it, there's a good story going round about how a Ferarri engineer came over to admire the sag at the motor show. After asking the salesman what the spoiler was for, he received a long explanation about downforce and aerodynamics. The Ferarri engineer then explained that he worked in the aero division in the Ferarri F1 team and that he could assure the salesman that it in fact did nothing at all, providing much embarrassment to the salesman.

Not sure if its true, but I can't see it doing anything either. It's too small and in an area that's never really going to see any high pressure air. I'd go for the sc power diffuser personally - tried and tested!

[jesfirth]

7 TVR said:

Hi Jes, have also chatted to Andy at length regards Aero and have conducted some high speed testing with both front splitter & rear diffuser!
The front splitter has made a big differance to high speed stability but i still feel the arse is getting to much lift.
I'm thinking of switching to a single exit exhaust enabling me to run the SC Power diffuser, as Precat has had good results on the road and Andy proved its worth on track!
I would be interested in what you come up with!!

I agree. It think just because its easy and a no cost option I will bung on a rear spoiler and see what it does then it's a quick chop of the exhaust straighten the tail pipes - silly design anyway and use the sc power diffuser that looks like a good value option. Thanks i hadnt seen that they make one. To make it work I guess we also need a sheet under to create a flat floor. The problem is that all this adds weight. Can't have everything I suppose Christian. You should bring that tuscan out on some of the tvcc speed champ rounds. You'd love it

[V8 GRF]

450Nick said:

As I understand it, there's a good story going round about how a Ferarri engineer came over to admire the sag at the motor show. After asking the salesman what the spoiler was for, he received a long explanation about downforce and aerodynamics. The Ferarri engineer then explained that he worked in the aero division in the Ferarri F1 team and that he could assure the salesman that it in fact did nothing at all, providing much embarrassment to the salesman.

Not sure if its true, but I can't see it doing anything either. It's too small and in an area that's never really going to see any high pressure air. I'd go for the sc power diffuser personally - tried and tested!

Nice story but talking to the guys at TVR who were there when they put the T350 through the windtunnel the Sagaris spoiler does reduce the amount of lift generated by the backend of the car by a significant amount.

[450Nick]

jesfirth said:

I agree. It think just because its easy and a no cost option I will bung on a rear spoiler and see what it does then it's a quick chop of the exhaust straighten the tail pipes - silly design anyway and use the sc power diffuser that looks like a good value option. Thanks i hadnt seen that they make one. To make it work I guess we also need a sheet under to create a flat floor. The problem is that all this adds weight. Can't have everything I suppose Christian. You should bring that tuscan out on some of the tvcc speed champ rounds. You'd love it

Likewise you should bring that griff out racing...!

[jesfirth]

Nick. I know I should but sadly can't afford it )-:

[wadsapple]

I made this de-fusier from scratch last year for my car.Glass fibre materials came to about £15.00 and took four nights to knock up using a bit of round gutter pipe as a form and a sheet of old doubleglazing glass on a bench.It works very well indeed I think, well at least iv'e not been in the armco yet.You could probably save a lot of exhaust chopping & welding in the process of making your own, fibreglassing really isn't rocket sience.

[7 TVR]

wadsapple said:

I made this de-fusier from scratch last year for my car.Glass fibre materials came to about £15.00 and took four nights to knock up using a bit of round gutter pipe as a form and a sheet of old doubleglazing glass on a bench.It works very well indeed I think, well at least iv'e not been in the armco yet.You could probably save a lot of exhaust chopping & welding in the process of making your own, fibreglassing really isn't rocket sience.

Car is looking really great Perry!

[jesfirth]

perry, thanks for the photos - that looks really good. fibreglass i can do - i spent many years breaking and repairing boats. My problem is that I am not sure how to produce a design that works. Did you make it flat or is it tilted up at the rear? and does it widen out at the back or narrow to accelerate the air at the rear? TIA Jes

[griffdude]

Hi Jes
Rear diffusers slow the airflow down (bernoulli's principle) as air passes through them creating a drop in pressure. The 'kick' up at the rear lip is mostly cosmetic IMHO due to extremely turbulent airflow behind the car but stand to be corrected on this. More benefit is to splay the vertical fins out towards the rear.

O/T are you still having issues with oil pressure in corners? I'm split between an Accusump or a JE baffled sump & am going to remove my oil cooler (planning to do the BOC Nat'B' next year).

[jesfirth]

griffdude said:

Hi Jes
Rear diffusers slow the airflow down (bernoulli's principle) as air passes through them creating a drop in pressure. The 'kick' up at the rear lip is mostly cosmetic IMHO due to extremely turbulent airflow behind the car but stand to be corrected on this. More benefit is to splay the vertical fins out towards the rear.

O/T are you still having issues with oil pressure in corners? I'm split between an Accusump or a JE baffled sump & am going to remove my oil cooler (planning to do the BOC Nat'B' next year).

thanks - i clearly need to do more research on the diffuser! the john eales sump works very well and stabilises the oil pressure. i only get a partial drop in pressure on 1 track which is MIRA which has a very long - best part of a 3/4 circle fast 3rd gear constant left hand bend. So i think it is working well and a sound investment. Jes

[Guillotine]

Audi TT Jes.

Some minor work to get it to fit as the curve is slightly different.
Comes with bolts embeded to make mounting very secure too.

I reinforced the bootlid to make it stronge enough for the wing too, possibly too strong.
Generated about 150kg of downforce with the wing, but the kicktail was the most important bit. It killed the lift.

Dont go for the bigger TT kicktail. too hard to mount, looks too big too.

This was mine...



Here you can clearly see how the air is taken straight out from the line of the spoiler and NOT curling down the back as would happen on a std boot ie generating lift.


As for difusers, I had on of those too but they dont make much difference.
They work best with flat floors, otherwise the air is too turbulent to have a mojor effect. Probably lose out overal due to weight added!
A

Edited by Guillotine on Monday 5th November 09:39

[jesfirth]

Andy - thanks - that is a really useful photo. Matt Oakley has an Audi TT spoiler on his as well - so I think that may well be my chosen route - much appreciated cheers Jes

[Guillotine]

tesdt day at Snett

http://www.tvrmonster.com/gallery/twentyone/new%20...

Perrys diffuser may well work as the wishbones have been filled (I did that too) and it extends a good distance which again is really important.
Make you vulnerable to a rear tap in Tuscans though...