Discussion
hi steve I looked at the SC rear spoiler but came to the conclusion that it might not help much and would add weight. I built various versions myself that did not work and now have a solution that does seem to work comprising:
centre exit exhaust to remove the changes in direction which affect airflow beneath the car
infilled the bottom of the rear wishbones with plates and filled the gap between them and the under floor area
added a small rear lip boot spoiler with a vertical gurney flap to disrupt the airflow.
I don't know what downforce it adds but it does seem to help a bit - BUT it all makes absolutely no difference that I can feel below 70 mph so its only really any use on high speed corners mostly 90mph plus!
centre exit exhaust to remove the changes in direction which affect airflow beneath the car
infilled the bottom of the rear wishbones with plates and filled the gap between them and the under floor area
added a small rear lip boot spoiler with a vertical gurney flap to disrupt the airflow.
I don't know what downforce it adds but it does seem to help a bit - BUT it all makes absolutely no difference that I can feel below 70 mph so its only really any use on high speed corners mostly 90mph plus!
Hi Jes Yours is about the only one I have seen on a Griff that looks like it may do something. Pleased you now have a Gurney flap, think it was me which suggested that.
Trying to think of something to give a bit more confidence round hollow bend, I guess we are both doing around 98 at the approach so well into the aero region. You however being either braver or less sane carry far more speed round the corner. I tried it a couple of times last year without lifting but visited the crop going backwards.
Trying to think of something to give a bit more confidence round hollow bend, I guess we are both doing around 98 at the approach so well into the aero region. You however being either braver or less sane carry far more speed round the corner. I tried it a couple of times last year without lifting but visited the crop going backwards.
Steve - it was you who suggested the gurney. thanks for that it was good advice. I have yet to remove the heavy ally bolted one and make a light fibreglass one bonded into place - just been too busy.
I think perry is right - infilling the rear wishbones is a decent mod for airflow and very easy to do. I just used 2mm thick ally sheet cut to fit drilled and fixed with heavy duty cable ties around the wishbones.. then I added a further piece of ally sheet screwed to the rear of the "flat" floor that extends from the floor pan to within 5mm of the rear wishbone sheet to fill in the gap at the front..
I did add a flat floor under the engine as well cut around the sump. that helped the under car airflow BUT the oil temperature increased noticeably when driving hard as the sump gets no natural cooling and that was with an oil cooler in the nose - so I took the sheet back off. I have discovered by trial and error that everything you do has an unexpected consequence (-:
I am now thinking through rear wheel arch venting.....I reckon a decent slot/hole across the top of the inner arch with a duct to the rear light venting out through the body recess on the outer side of the rear light fittings. it should work and there is no silhouette change.
I think perry is right - infilling the rear wishbones is a decent mod for airflow and very easy to do. I just used 2mm thick ally sheet cut to fit drilled and fixed with heavy duty cable ties around the wishbones.. then I added a further piece of ally sheet screwed to the rear of the "flat" floor that extends from the floor pan to within 5mm of the rear wishbone sheet to fill in the gap at the front..
I did add a flat floor under the engine as well cut around the sump. that helped the under car airflow BUT the oil temperature increased noticeably when driving hard as the sump gets no natural cooling and that was with an oil cooler in the nose - so I took the sheet back off. I have discovered by trial and error that everything you do has an unexpected consequence (-:
I am now thinking through rear wheel arch venting.....I reckon a decent slot/hole across the top of the inner arch with a duct to the rear light venting out through the body recess on the outer side of the rear light fittings. it should work and there is no silhouette change.
hi neal
As Jes said really, the air flow is badly disturbed in that area and I found filling in the rear wishbones made a significant difference to handling for a cheap mod, less than £7.00 in ali.
Jes you may find this interesting again a cheap mod less than £5.00 and will add to less lift at high speed. I took a strong
flexi bathroom extractor pipe from top of arch that I fibre glassed in ran it through the boot and it exits through the two holes you can see under the rear brake light lenses either side, no disturbing the silhouette. Jes ,you ever heard of Vortex Generators ? very useful things they are
let me know if you want to discuss on here a little further, very powerful things at £3.50 each
OP you can clearly see my rear diffuser, does it work .............................. probably but only as a part of a full package of aero on the car. One thing to remember about the black art of aero is if it gives you more confidence to push the throttle down harder sooner it is a worth while mod in my humble opinion. see bottom picture which shows that very little air is sticking to the rear of the car so that means no real drag in that aera.
IMG_0037 by flat chat, on Flickr
11201624_828919383840023_1726743601701612858_n by flat chat, on Flickr
As Jes said really, the air flow is badly disturbed in that area and I found filling in the rear wishbones made a significant difference to handling for a cheap mod, less than £7.00 in ali.
Jes you may find this interesting again a cheap mod less than £5.00 and will add to less lift at high speed. I took a strong
flexi bathroom extractor pipe from top of arch that I fibre glassed in ran it through the boot and it exits through the two holes you can see under the rear brake light lenses either side, no disturbing the silhouette. Jes ,you ever heard of Vortex Generators ? very useful things they are
let me know if you want to discuss on here a little further, very powerful things at £3.50 eachOP you can clearly see my rear diffuser, does it work .............................. probably but only as a part of a full package of aero on the car. One thing to remember about the black art of aero is if it gives you more confidence to push the throttle down harder sooner it is a worth while mod in my humble opinion. see bottom picture which shows that very little air is sticking to the rear of the car so that means no real drag in that aera.
IMG_0037 by flat chat, on Flickr11201624_828919383840023_1726743601701612858_n by flat chat, on FlickrEdited by 77racing on Friday 31st March 09:04
I was going to have a go at this idea I saw at combe, looks like it broke it's self but it should turn the 
on..........................................
543447_645859422100508_1753458090_n by flat chat, on Flickr
Another car I have come across was a full fat dark green MGBGT that had DRS , it does trackdays at combe and it works a treat.
on..........................................543447_645859422100508_1753458090_n by flat chat, on FlickrAnother car I have come across was a full fat dark green MGBGT that had DRS , it does trackdays at combe and it works a treat.
Hi Perry,
thanks for the info. rear grip is the problem for me as you know. we cant have a wing and the silhouette is supposed to stay pretty much unchanged.
the front was easy a big splitter - I had to cut mine down to get some front/rear balance back into the car. I guess you don't have the same problem?
i built a rear diffuser just like the one on the 6R4. It stuck out of the rear by about a foot. I never really got it to work though - I don't think I ever got the angle right and at the time I didn't have a flat floor or side skirts so that probably killed the benefit. I also kept breaking it when I hit things or ran off the track so in the end it binned it.
glad to know that the arch/ducts/holes work. did you angle the pipes up slightly at the exit at the rear of the car to direct the exiting air upwards?
thanks for the info. rear grip is the problem for me as you know. we cant have a wing and the silhouette is supposed to stay pretty much unchanged.
the front was easy a big splitter - I had to cut mine down to get some front/rear balance back into the car. I guess you don't have the same problem?
i built a rear diffuser just like the one on the 6R4. It stuck out of the rear by about a foot. I never really got it to work though - I don't think I ever got the angle right and at the time I didn't have a flat floor or side skirts so that probably killed the benefit. I also kept breaking it when I hit things or ran off the track so in the end it binned it.
glad to know that the arch/ducts/holes work. did you angle the pipes up slightly at the exit at the rear of the car to direct the exiting air upwards?
jesfirth said:
Hi Perry,
glad to know that the arch/ducts/holes work. did you angle the pipes up slightly at the exit at the rear of the car to direct the exiting air upwards?
Hi Jes,glad to know that the arch/ducts/holes work. did you angle the pipes up slightly at the exit at the rear of the car to direct the exiting air upwards?
Wow well done that man, you built a blown diffuser like the 6R4, I would really like to see your take on Adrian newey's idea if you have any pictures. The 6R4 version was crude and obviously it must of worked a bit or else he broke it whilst doing a bit of grass cutting LOL.As regards the exit pipework on the rear arch mod pointing up. I don't see the air exiting being of any use as it will not be traveling with any speed or force, it is more taking high pressure air away from the top of arch to stop the pressure lifting the rear of the car at speed. It will not give you down force, but it will get the car to handle better and will move around a bit less on the limit at the rear and give you more confidence whilst at the limit. I really don't have a down force problem as I have the twin element rear wing doing it's job at the back which you can't have in your regs as I remember. what I have done getting back on track with diffusers is I have since the picture above modified mine again and like you was thinking having the exit air pointing up would push the car down, wishful thinking maybe as I don't see the force of the exit air under the car being great enough to make much difference but heh if you don't try you won't know. It is the sum of all parts that work. Can you use wider tyres in your regs as that will give you more mechanical grip which will be noticeable . I went from 9" to 10" rims and it was really significant for all round grip. My lap times at most circuits dropped by a second. The picture below clearly shows my new take on my old diffuser which I now have on the car. twin layer as I thought that that would give me twice the surface area for the same size space. Exiting uphill as you are thinking about.
DSC_0729 by flat chat, on FlickrEdited by 77racing on Saturday 1st April 17:11
I ran the rear SC power rear diffuser on its own for a few years and although it improved rear end grip and stability on long fast bends, the down side was the front end felt light and unstable in a straight line. This led to the fitment of my home made front splitter which works by counteracting the high pressure area between the forward leaning radiator and the ground. Now that high pressure area is between the radiator and the top side of the splitter resulting in a downward force on the front end of the car. The difference is amazing and the car feels a lot more balanced and stable above 90mph when compared to how it was without the aero aids. Tested on tracks and in Germany.
77racing said:
Hi Jes,
Wow well done that man, you built a blown diffuser like the 6R4, I would really like to see your take on Adrian newey's idea if you have any pictures. The 6R4 version was crude and obviously it must of worked a bit or else he broke it whilst doing a bit of grass cutting LOL.As regards the exit pipework on the rear arch mod pointing up. I don't see the air exiting being of any use as it will not be traveling with any speed or force, it is more taking high pressure air away from the top of arch to stop the pressure lifting the rear of the car at speed. It will not give you down force, but it will get the car to handle better and will move around a bit less on the limit at the rear and give you more confidence whilst at the limit. I really don't have a down force problem as I have the twin element rear wing doing it's job at the back which you can't have in your regs as I remember. what I have done getting back on track with diffusers is I have since the picture above modified mine again and like you was thinking having the exit air pointing up would push the car down, wishful thinking maybe as I don't see the force of the exit air under the car being great enough to make much difference but heh if you don't try you won't know. It is the sum of all parts that work. Can you use wider tyres in your regs as that will give you more mechanical grip which will be noticeable . I went from 9" to 10" rims and it was really significant for all round grip. My lap times at most circuits dropped by a second. The picture below clearly shows my new take on my old diffuser which I now have on the car. twin layer as I thought that that would give me twice the surface area for the same size space. Exiting uphill as you are thinking about.
sorry I haven't got any photos - they were all on my old ipad and it died so I lost stacks of photos that weren't backed up - I learned from that!! but my solution was pretty much identical to that on the 6R4 except my exhausts were straight from the front along the centre line so I just used them to accelerate the air over the centre of the diffuser. Wow well done that man, you built a blown diffuser like the 6R4, I would really like to see your take on Adrian newey's idea if you have any pictures. The 6R4 version was crude and obviously it must of worked a bit or else he broke it whilst doing a bit of grass cutting LOL.As regards the exit pipework on the rear arch mod pointing up. I don't see the air exiting being of any use as it will not be traveling with any speed or force, it is more taking high pressure air away from the top of arch to stop the pressure lifting the rear of the car at speed. It will not give you down force, but it will get the car to handle better and will move around a bit less on the limit at the rear and give you more confidence whilst at the limit. I really don't have a down force problem as I have the twin element rear wing doing it's job at the back which you can't have in your regs as I remember. what I have done getting back on track with diffusers is I have since the picture above modified mine again and like you was thinking having the exit air pointing up would push the car down, wishful thinking maybe as I don't see the force of the exit air under the car being great enough to make much difference but heh if you don't try you won't know. It is the sum of all parts that work. Can you use wider tyres in your regs as that will give you more mechanical grip which will be noticeable . I went from 9" to 10" rims and it was really significant for all round grip. My lap times at most circuits dropped by a second. The picture below clearly shows my new take on my old diffuser which I now have on the car. twin layer as I thought that that would give me twice the surface area for the same size space. Exiting uphill as you are thinking about.
Edited by 77racing on Saturday 1st April 17:11
I thought your double deck diffuser was a good idea when you made it - I am sure that double the surface area makes a difference. did you put a flat floor under the whole car or just rely on the tub/floor as it was. if the former how do get the heat away form the exhaust and keep the sump cool? - oh just realised you are probably dry sumped anyway?
my side skirts are black plastic 77mm deep - they could be deeper but as I seem to visit the scenery regularly and still drive on the roads to the events I thought I should be sensible - they bend a little to get over speed humps.
I like the wider wheels and tyres idea - we can have any width of tyre. I am currently 255 40 17 so I might well go down the wider rim/tyre route. matt Oakley had I think 10 or 10.5 rims on his griff with 335 tyres so they will fit. what width rubber do you have at the rear on the Tuscan?
this is what I am trying to stop form happening - wait for the lift off after fordwater https://youtu.be/_joq8Exim7o
spikep said:
Have you got pictures of what's been done to the rear wishbones?
here you go took some finding in amongst thousands of pictures 
white nearly finished 006 by flat chat, on FlickrMorning Jes,
Yes have gone fullish flat floor a few years ago. I have watched that bit of the video back 20 times and I think the wind noise is loud LOL. I recon that is a classic case of snap over steer on lift off as you say. To be fair no saving those. I have never had that and am mighty glad I havn't. You may have lifted off to fast but as I say wind noise makes it difficult to hear what's going on.At that speed i'd be treating the throttle like a wet sponge in my best sunday suit. For it to snap that early on initiation of the turn in you are getting massive weight transfer to the front.That must a very nervious car to drive. Either from coming off the throttle too aggressively or the car is so badly balanced. It sounds like this has acured more than just this once. That is a confidence robber if ever their was one. I will do some more thinking and get back to you if I have any suggestions as to where to go in terms of a fix. I dought very much that you are getting lift from the rear arches in that instance and i'm not sure bigger tyres / mechanical grip will sort it either. Can you post a picture of front and rear aero ?
Yes have gone fullish flat floor a few years ago. I have watched that bit of the video back 20 times and I think the wind noise is loud LOL. I recon that is a classic case of snap over steer on lift off as you say. To be fair no saving those. I have never had that and am mighty glad I havn't. You may have lifted off to fast but as I say wind noise makes it difficult to hear what's going on.At that speed i'd be treating the throttle like a wet sponge in my best sunday suit. For it to snap that early on initiation of the turn in you are getting massive weight transfer to the front.That must a very nervious car to drive. Either from coming off the throttle too aggressively or the car is so badly balanced. It sounds like this has acured more than just this once. That is a confidence robber if ever their was one. I will do some more thinking and get back to you if I have any suggestions as to where to go in terms of a fix. I dought very much that you are getting lift from the rear arches in that instance and i'm not sure bigger tyres / mechanical grip will sort it either. Can you post a picture of front and rear aero ?
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