793 replies to this topic

[sford]

What angle are you running the rear diffuser at? I read in comp car aero that they experienced turbulence in the diffuser at over 11deg on their test vehicle (350z I think). Obviously won't translate directly but some vanes within the diffuser may help to stabilise this if it does occur. Liking the amount of thought that has gone into this, hope it translates to a success for you come race time. 

[turbotoaster]

its adjustable from about 5* to 15* so I wont know what angle to run it at until testing, its set at about 15* just so i dont kick the strakes with my feet so often when pushing it in and out.

 

Jamie told me he ran his up to 14* and the air was fully attached and could run it even higher so ive got a fair range of adjustability.

 

Did a little bit more work on my car tonight.

 

Fitted my throttle body adapter plate, the easiest option would have been to fit a vvc inlet manifold but ive been told the turbotechnics inlet manifold has much better flow rating than the vvc one so I thought it was worth working a bit harder to keep it, you can just see it bolted to the red inlet manifold.

 

 

Also test fitted my downpipe and exhaust again to make sure that it had all been cut and angled correctly, then marked up all the hangers for box

 

You can see how its going to exit like an S2 elise/exige, we will see how it copes with the noise levels, its a 2.25" box hence the reducer, which ill use for the short term until we finally turn the boost up to full where ill change to a 2.5" and decide whether to go bigger if its noisy for all tracks

 

Oh yeh, also got a picture of the inside of my doors........mmmm kevlar, be useful to hide behind if my girlfriend gets mad for spending all my time in the garage and tries to shoot me

[turbotoaster]

Fitted my other door and mirror today




reminds me something from Predator for some reason


Got my turbo feed oil line made up, was a bit of a pain as we spent ages trying to work out what fitting was in the turbo


Also I know its not scientific but for fun while I was blasting off my car with the air compressor I blew air into the canard and wind air stream and you could feel the air being attached to both sides and turning the air up and out at the same angle, was interesting to see and imagine how it will react when the car is moving

 

[chris_uk]

why dont you go about making your footprint bigger? ie wider wheels..

[FLD]

Just a thought.....

have you considered the leverage applied by mounting your wing so far back.  Would it cause front lift?  I know most single seaters try to get the wing mounts above the rear hubs for this reason.  I appreciate why you've mounted it there, I was just wondering if you'd considered the consequences and would like to hear your findings.

[Nev]

Have you considered the leverage applied by mounting your wing so far back.

 

I concur with this line of reasoning/questioning, centre of lift is almost certainly going to be somewhere over the cabin area (due to its shape), hence centre of aero down-force should ideally be over the cabin too.

 

In practice (as mounting a wing over the cabin (ie centre of lift) is next to impossible (and I expect you already know this)  most cars fit aero at the front and rear to exert a (hopefully) roughly equal force at front and back which sum up their centre of force over the centre of the car. Looking at your pics, I am guessing that the rear down-force * moments of leverage is going to be more than at the front end, hence leading to a possible light front end. Just speculation on my part from the pics mind you, and its hard to judge stuff like this remotely.

 

Very interesting project BTW. I wish I had had room in my engine bay to mount my turbo high up like that and have such a nice straight exhaust run.

 

 

Edited by Nev, 30 November 2013 - 11:24 PM.

[turbotoaster]

why dont you go about making your footprint bigger? ie wider wheels..

Ive already gone from 15x5.5/16x7.5 with 195/225 up to 16x8/17x9 with 225/255 so its gone up a fair bit already, im pretty much maxed out at the front, I could go wider on the rear but I would have to remake a new narrower diffuser so allow for a wider wheel, I cant push the wheel out any wider as im already maxed out with that.

 

Just a thought.....

have you considered the leverage applied by mounting your wing so far back.  Would it cause front lift?  I know most single seaters try to get the wing mounts above the rear hubs for this reason.  I appreciate why you've mounted it there, I was just wondering if you'd considered the consequences and would like to hear your findings.

I have thought about it yes, infact thats why my wing uprights are so basic, if I need to move the wing further forward, I can literally side it further into the car and drill 4 new holes into the uprights and bolt it in, would only take 5 mins(im taking my fully charged drill when we go testing)

 

That way we can test in its current position, then try it further forward and see how the car reacts, once we have decided the wings final position I will be making some proper uprights with a fully curved body to make sure theres no potential stress points(even though the current ones have radius at the 90* sections)

 

The actual bolts that go into the longerons are as far forward as i could make them, infact the one furthest forward I ended up drilling straight through the longeron and out the other side and used a fairly long bolt, I wanted to put my hand down the inside of the longeron and bolt it, but couldnt reach with the clam on, as like you say I wanted the actually downward force to be as close to the rear hubs as possible.

 

From what I was aware of, its not where the wing is positioned, its where its connected to the chassis which dictates the actually effects on the car, I did run the upright along the longeron touching the lip that the s1 has to try and distribute any extra load along there incase I was overloading the bolts its connected with.

 

Its been mentioned before about will the rear wing at its position cause a tiping point and lift the front end, ill be honest and say I dont actually know for certain, but everything ive read is to put the wing as far back as possible.

 

 

My thoughts are engine bay scavanging, less turbulent air which means I can run less wing angle(drag) to achieve the same numbers, less chance of the air hitting the wing at different angles along its length effectively making either the centre section very draggy, or the outer sections reducing there downforce capacitys, also If I decide to shorten the diffuser i can use the wing to drive the underbody for produce more frontal downforce.

 

I believe when the car is done it will actually be about 700kg due to the amount im adding to the rear with the turbo setup, bigger wheels and tyres and aero, i think without all them I would be about 650kg, so im hoping the 50kg weight penalty will be worth it.

 

Originally I was hoping for a 45/55 weight distribution with an aero balance matching that, though maybe a little bit more rearward for safety, but because of the extras weight i think im going to be back down to the 40/60 split, of which 150kg front downforce(the hardest bit) and 200kg rear at 100mph

 

I think jamie produced about 80kg of downforce on the front end with a 100mm splitter, so im hoping my bigger splitter with a larger surface area and canards can produce more than that so I can make use of the wing

 

 

Have you considered the leverage applied by mounting your wing so far back.

 

I concur with this line of reasoning/questioning, centre of lift is almost certainly going to be somewhere over the cabin area (due to its shape), hence centre of aero down-force should ideally be over the cabin too.

 

In practice (as mounting a wing over the cabin (ie centre of lift) is next to impossible (and I expect you already know this)  most cars fit aero at the front and rear to exert a (hopefully) roughly equal force at front and back which sum up their centre of force over the centre of the car. Looking at your pics, I am guessing that the rear down-force * moments of leverage is going to be more than at the front end, hence leading to a possible light front end. Just speculation on my part from the pics mind you, and its hard to judge stuff like this remotely.

 

Very interesting project BTW. I wish I had had room in my engine bay to mount my turbo high up like that and have such a nice straight exhaust run.

 

 

 

As mentioned above, the rear will always be stronger than the front, theres no way around that, if in the future I build splitter diffusers and have better wheelwell ventilation(cut the inner sill out) then that may change a bit but never fully.

 

There are benefits and downsides of the turbo position, the downside is weight distribution, its a big old lump to have high up in the car, the benefits are easy access to everything, no hot temps near my fuel tank(which heating up the fuel is never a good thing) no hot temps near my driveshafts or gear cables so wont cook anything, also I dont need to run naca ducts underneath for better aero benefits.

 

 

Edited by turbotoaster, 01 December 2013 - 01:33 AM.

[FLD]

Its nice to see the good, clear thought that's gone into this.  Fingers crossed it all comes good.  top job.

 

 

ETA: just thought about the wing mounting position vs actual wing position discussion.  Wing mounted above the hubs with vertical mounts would give 'down' force.  Mounting it at the hubs on a strut which makes the wing position further back would give down force but also torsion at the mount IMO so would still have some leverage effect.  Let us know how this pans out in testing.

Edited by FLD, 01 December 2013 - 11:51 AM.

[turbotoaster]

Little update

Started making the brace for the turbo, there is 3 threaded holes on the block that we are going to bolt a plate to, off that will be a bar connected to the turbo, this will take some of the weight off the head as the manifold, turbo and downpipe add up to a fair bit of weight.


Finished the hangers for the exhaust, we are going to hang it off the wing uprights(the horizontal section is higher than the longeron) may aswell make use of them for something else.


Made an adapter plate for the throttlebody and ported the inlet out so its a better transition from round to rectangle


Bought and mocked my chargecooler, this seemed the simpliest solution, with the shortest pipework and gives me something to mount it off(again horizontal upright) It looks close to the tyre but is actually 10cm away so should be fine, especially when im running very hard springs.



This is a quick doodle of the layout so you can see how I have done it


Being happy with my design I started working out all the bracket components and silcone pipe lengths, some of you might be thinking about having a fixed chargecooler but a 'rocking' engine but i was going to add silcone inflated joiners to cover for that.

 

[Andrew aka Stuwy]

Just cought up with this topic. I am looking forward to your season in TA. I know your car appears to be a bit marmite but I think it looks nuts (that's good) Love the idea your just going for it. Fair play We like to think ourselves not like other forums and a bit more... I don't know, weird I guess but there are some really nice people here. Testimony to that is you have had 2 offers for pit help already and last seasons winner with advice! P.s. Should have got a VX

[Mike (Cliffie)]

Progressing well and I am looking forward to your first test.

[turbotoaster]

Just cought up with this topic. I am looking forward to your season in TA. I know your car appears to be a bit marmite but I think it looks nuts (that's good)

Love the idea your just going for it. Fair play

We like to think ourselves not like other forums and a bit more... I don't know, weird I guess but there are some really nice people here. Testimony to that is you have had 2 offers for pit help already and last seasons winner with advice!

P.s. Should have got a VX

 

Yeh everyone is really friendly on here, its a nice place to be and I do enjoy reading everyones build threads as some things are transferable to my car so it gives me good ideas etc.

 

I did think about a vx tubby before buying the elise, I just didnt see one I wanted at the time and knew I wanted to build something super light(i even looked at seven replicas etc)

 

Progressing well and I am looking forward to your first test.

 

Thanks, we are getting there slowly, once all my suspension is sorted I think we just need to get it on the dyno for some tuning and we can get some testing done.

 

Also in regards of my aero package, i contacted Simon Mcbeath to get his point of view on the car.

This was his response, the red font are his words

Hi Simon,

Im sure you get alot of messages everyday asking all sorts of questions so ill try and keep it relatively short, if you could add any thoughts to my aero package I would be most grateful.

I started reading info from yourself from Track Driver Magazine, then ive bought and read your book and started subscribing to Racecar Engineering, though I did start building the car before I bought your book so there might be a few bits that may not have followed the book.

Its a Series 1 Lotus Exige that I will be running in UK Time Attack Series next year.

Since I cannot afford a 500bhp audi/honda engine or the maintenance that will go with it, I decided to make up the laptime with higher apex speed and lateral G, so im running a 300bhp rover k series engine with a 700kg weight without driver, for reference im up against 600bhp/1000-1100kg cars.

The bit im stuck on is the rear diffuser and wing placement, now Time Attack is one of those rare motorsports where there are no aerodynamic limitations(like Pikes Peak), if you can dream it you can make it.  I’m very familiar with TA, we have quite a few clients worldwide.

Your book mentions to run as steep an angle as you can get away with while keeping the air attached to maximise the flat floor area within the dimension restrictions.....but what happens if you dont have the dimension restrictions, if we forget rear wing interaction is it better to run it longer and shallower to allow for the gradual air pressure dispertion.

Im running a fully flat underfloor the width of the rear tyres, with end plates and skirts the full length so most air that gets under the splitter should make it to the rear of the car.

My diffuser is actually about 1 metre long and full adjustable from 3* up to 10* will the length give me any advantage?

Am I best just keeping it at the usual limit of 7* or will I gain an aerodynamic advantage by running it at a steeper angle, just film from behind to check tuffs are still pointing up to check attachment?My personal view is that a diffuser can be steeper than this on your type of car but it should only extend a short distance out at the rear. The reason for this is that you also get low pressure acting on the roof a diffuser that juts into the wake area, which will create some positive lift. There’s no arguing that bigger diffuser volume drives the underfloor harder to get more downforce there, but there must be a trade off and I don’t advise going as far back as you have gone.

Also since the lotus chassis doesnt have much front overhang it makes it more difficult to create decent levels of front downforce so what I have done for the splitter is have it extend from the front of the car buy 200mm, but rather than following the shape of the front clam(curved) maintaining 200mm, I have made the front square to maximise surface area, added 60mm end plates and large canards with endplates(the plates arnt shown) I didnt go any higher on the end plates on the splitter for fear of it negatively interacting with the canards. The front end kit looks aggressive, as it needs to be to balance a dual element rear wing, but I can’t see any major flaws from the photos.

I am going to cut out a big rectangle on top of the front arch to let any high pressure out and try and I have some space carbon angle to glue infront of it to allow the high pressure air to escape which should help against lift, I was going to try and make multple louvres along the length of the hole but I notice the LMP1 cars just have an open rectangle, this might be regs but wasnt sure.Louvre the cutouts so air can’t get in from the front.

Would you agree that im going along the right path(front wise)?yes


And the final thing Im wondering about is, your book pretty much says to put the wing as high and as far back as possible to get cleaner air to maximise downforce or the need to run less wing to reduce drag while still maintaining the same level of downforce, when you put the rear wing further back from the rear axle it creates a leverage that also lifts the front end up.

Now if I cannot create enough frontal downforce to be able to make proper use of the wing, would moving the rear wing further forward towards the rear axle allow more downforce to be applied to the rear wheels without adding excessive front end lift, Ive made the uprights a very simple design so i can easily slide the wing forwards and rearwards to find the best solution, once its finalised ill make some better ones without the 90* angle.It’s all a trade off – yes, further forwards means less unloading at the front, and also less Df at the rear tyres for the same wing setting. But this is also about getting the wing off or high enough above the rear deck so it doesn’t suck upwards on that.By eyeballing your photos I suspect you will have too much rear wing to be able to get a balance as things stand.

ie say I get 100kg of front downforce at 100mph and 200kg of rear, but the rear wing lifts the front up by 50kg, then moving the rear wing forward 15cm and turning the wing up a little to maintain the 200kg of downforce and only have 20kg of front lift........or does it not work that way?


Sorry for all the questions and thanks in advance for taking the time to read this, any information you can provide and thoughts on my project would be most grateful as i can imagine your a busy man but I didnt know who else to turn to as to save wasting any of your time.


From what I can read into that is that I should shorten my diffuser and bring my wing further forward to stop the leaverage effect which was discussed in this thread in detail ,

But from what he says I think that the larger diffuser will drive the underbody harder, hence create more downforce at the throat so providing more front downforce at the expense of the rear because my throat is fairly forward with the rake im running, now that actually might be a good thing as my rear wing will give me more downforce than I will ever need and its the front that needs the work, so trying the longer diffuser and more wing instead would give more front downforce compared to shortening it and running less wing angle.

Moving the wing forward 15cm seems the best thing to do to stop leverage effect, though its important to make sure the full underside of the wing is either high enough to stop it pulling on the clam or back far enough to stop the same effect, at 15cm im a of centremetre from overlap.

Made a start on helping reduce high pressure area in the front clam, there are 3 things to do, the first is to remove the lower sill extensions as they are working like little parachutes not letting the air out and generally catching bricks.


You can see them as the little black panels on the bottom right hand side
So off they came but that meant I had nothing to hold the rear of the clam from flapping, so I made some carbon  extension plates to bolt everything together.



Also we finished up the turbo setup today, bolted it all onto the jig to check over everything before its all bolted to the car tomorrow night.

Im pretty happy with it all, seems to do everything we want, only extra thing we need to make is a turbo brace which will bolt from the inlet manifold to the turbo to help take pressure off the head. We will bolt a couple of rose joints from the upper inlet with bars connecting to the side of the turbo.

We have looked at a lower manifold mount as below but havent made the final decision on this as it potentially can cause issues by the metal pipe expanding putting vertical pressure on the manifold rather than taking the weight of the manifold off the head

[turbotoaster]

Well she lives!!! Working on it all day to get it started, fitting the oil drain and alternator on was more fun than I expected and had massive panic attacks when it seemed like the oil feed wasnt pumping oil. Short video of it running, its quieter than when it was supercharged and driving it up the road you can hear the turbo spooling behind you. Next I just need to get it over to a friend to refurb all the suspension, fit the lighten flywheel and ATB diff

 

[JohnTurbo]

This thing terrifies the life out of me!! It seems Ronnie is out (Golf) but dont underestimate Umar if he is in again...he has built up some reeeaaalll pace. I admire your boundless optimism and hunger for knowledge, but have two criticisms:- 1) You are trying to fully develop a car in one go and its a bit mental. Rome wasnt built in a day! Are you just very impatient? You are meant to improve it based on your needs while driving it. Do you drive it on track much? 2) The engine setup is going to end in tears if you dont fully, fully test it to death. Personally I bet you'd finish the year with more points just running a vhpd thats well proven. The FC broke something EVERY round...and this is the norm. Youd be terrified to hear how many gearboxes Umar has used and Ronnie eats parts for lunch. Get to a safe power level and learn to use it to the best. If I didnt know better Id think youd been paid by the aero haters to deliberately get mad aero banned. I gather its been discussed before! Now the aero dude has told you what everyone else has inferred. ..that diffuser and spoiler are too big, I assume you will cut it right back? I do wish you well...I might even see you there if your money holds up!

Edited by JohnTurbo, 23 December 2013 - 08:45 PM.

[turbotoaster]

I had heard Umar had picked up the pace recently, but he has plenty of power, fairly wide tyres and some downforce so it would surprise me if it wasnt quick.

 

its a shame ronnie is driving the AMD car as I was looking forward to seeing how I would compare to him.

 

This might sound strange to you, but I just want to go as fast as possible, im not bothered about collecting points etc, I would rather have fastest laps than the championship.

 

Im developing the car because I can, I really like that Time Attack is a completely open motorsport, that if I can think it up then i can build it, so im really enjoying building it, some people smoke, some people go the pub, I work on this, its my hobby, has the aero caused any delays in getting to the stage im at now, nope i would be in the exact same position today but without the aero.

 

Ill be moving my wing another 15cm further forward but im leaving the diffuser where it is.

 

I will be getting it on trackdays to check the engine over, I understand the limits of this engine so there is no point pushing beyond them as that will just cause problems, as soon as its mapped the priority is to get it on track and learn as much as I can about the car.

 

Im fairly confident that the car should hold together, it spent most of its life on track so the major issues have been dealt with. The gearboxes are good for 400bhp and the engine will be running nowhere near that. The suspension is being setup by an expert so thats taken out of the equation, the brakes are getting sorted, everything close to the turbo/exhaust will be heat wrapped. So for me the only unknown is the engine.

 

Im designing the car to go around corners as fast as possible on treaded rubber, but hopefully enough power than I dont become a mobile chicane down the straights, with the budget I have this seemed the best solution in my eyes, as fitting any other engine would be to expensive and my aero has hardly cost anything to make.

 

Whether im right or wrong in my choices we will see, if it all goes wrong im sure there will be a queue of people a mile long giving me abuse and I hope if it goes well there will be a queue of people saying well done.

Edited by turbotoaster, 24 December 2013 - 01:07 AM.

[Nev]

Hi dude, having had another read of this thread, I wonder if you will be making enough power to overcomethe drag of your aero developments. It's really amazing how much drag a simple wing can make in my lmited experience. If I drive with and then without the wing on my car I can easily feel the difference in drag from about 80 leptons and looking at your pics, on yours the effect will be even more prominent I think.

 

Best of luck, keep spannering

[Mike (Cliffie)]

There is some epic work gone in here and I wish you the very best of luck with it.

 

 

[turbotoaster]

Finally pulled it out of the garage and onto the road so i could have my first look at the car to get an idea on what needs doing.

End plates for canards, move the wing further forward, fit my front brake ducts, build my adjustable side skirts and then it needs a good map.

 

[chris_uk]

did you say you was changing the design of the wing uprights.. if your not then the first time you end up going sideways its just going to take your spoiler straight off.

[turbotoaster]

Hi dude, having had another read of this thread, I wonder if you will be making enough power to overcomethe drag of your aero developments. It's really amazing how much drag a simple wing can make in my lmited experience. If I drive with and then without the wing on my car I can easily feel the difference in drag from about 80 leptons and looking at your pics, on yours the effect will be even more prominent I think.

 

Best of luck, keep spannering

 

well i am expecting to loose speed from 80mph upwards compared to no aero, what im hoping for is i will gain more time in the corners than I loose down the straights, im geared to 140mph(on 5th gear limiter) so I cant imagine that its going to restrict me to much until 120mph, but will just mean on tracks like silverstone where 140mph is easier to hit ill probably be only able to hit say 135mph.

 

Looking at the rear wing data it causes about 25bhp of drag, and I imagine the canards and splitter will say cause another 25bhp of drag, so if my engine makes 300bhp then it will be like 250bhp at 100mph

 

The car is very light, should produce good torque so should be late on the brakes and be able to pull out of the corners at a swift old pace.

did you say you was changing the design of the wing uprights.. if your not then the first time you end up going sideways its just going to take your spoiler straight off.

 

Yes I will be changing them to more of a curve and also cutting triangles out of them to lighten and avoid side wind effects.