mx5cartalk.com

Hey guys,

A gentleman is entering this NA8 with VVT engine into the ClubSprint class at World time Attack Challenge this year. We finally got it all done and tuned and I thought members here would appreciate the video and maybe chat a bit about preparing for the event (Wink wink nudge nudge Mark).

Additionally with the new rules for 2b we are finally able to supply Cams competitors with turbocharger setups. We are really happy with the results and we hope to get a few out on the track to give the big boys a hard time. Id like to mention that this is a full road car setup with a full exhaust, cat and all, and that the engine has no performance mods, its just been strengthened, it even retains the standard compression.



Dann

Already had the chat I think

That’s an impressive number - rods, oil pump, balancer and e85?

Yes and supertech pistons and valve springs.

Dann

Download last years rules and build to them. If not sure send an email to the rule makers and get clarification. For a start you must use OEM hubs, this rules out using drop spindles in clubsprint. Further, you have to have a windscreen, front fenders must be OEM, however you can fit flares to cover the control tyres.

Will have to be able to put that power to the ground What is the weight? You can go down to 893kg. If you want to finish in the top 5 you will need to be at the min weight. However at 893 you will be restricted to a max of 265 tyres... Finding the right wheel size/width could be a challenge in itself.

At the pointy end of Clubsprint the aero (and cars) are very well developed and dríven by experienced drivers. Make sure you have sufficient time to test/tune the suspension and aero. It would also be prudent to do it on the control tyre in the size you will be using. Since the MX5 never came out with a flat floor having an effective rear difusser will be very difficult, hence mine has been removed. In a few weeks I will find out if the car is faster with or without. Due to the limitations of how far the splitter can poke out, developing downforce at the front is also a constraint. For this reason I'm working with somebody on a new front splitter/air dam. As posted elsewhere my new rear wing has been designed and will be built soon.

Just as important as aero is reducing drag. This is why I have a new wing and front air dam/splitter

One thing you will find out is the the amount of track time you are programmed to get is VERY different to what you actually get. Clubsprint sessions are normally shortened to make up time for other groups. Plus, this is the MOST annoying part, a lot of time is lost due to breakdowns as some cars have not even had shakedown runs and these sort of breakdowns cut sessions short and are AVOIDABLE!

Happy to provide my experiences, but I'm no where near your power levels

We will have to weigh the car in the coming weeks and try and determine where weight can come out of the car. It would have to be 100kg above min weight at the moment, at a guess.

The car runs only a 265 as it is so we will just focus on getting the weight out of it.

Regarding aero we are running a full vertical airdam front (aka crusher) and have a genuine GTC200 which will receive custom upright and end plates.

The time to beat is 1.38 and the driver has done a 1.45 with 200whp less and a LOT less optimal setup. It was dríven from work to the track that day If I am not mistaken. We believe that there are 2 or 3 whole seconds in power alone, another 2 in better aero, and the car also finally has suitable brakes. The last second or 2 required to get on the podium will have to come from the driver and chassis setup.

Is there anything you learned about the particular track regarding aero Mark? It's well outside of my expertise.

Thanks,
Dann

As someone who has done a bit of experimentation at SMP GP, I may as well chip in my 2c

Seat time. And some SERIOUS testing, done 'scientifically' (write it ALL down, change one thing at a time, etc).

With that power, and big aero, getting the gearing right and finding the optimum AoA for the rear wing should be priorities. Get those sorted, and you can then concentrate on fine tuning balance, handling and general suspension setup, and the driver can concentrate of going harder.

I am not sure if that wing is the best, it is 3D and can be quite draggy. You might want to talk to Lightyear, he said the other day he was getting into building wings - the right wing, mounted correctly, will be important it achieving aero efficiency. That means the biggest rear wing you can muster, using the most efficient airfoil. That way you get the rear DF you need at the lowest AoA which means lowest drag. (there's a bit more to it, but that is a good rule of thumb).

Is it running a stock 6-speed? What rear end? I found (on ~125rwkw) the 4.8 gave great acceleration but limited top speed - feathering the throttle for the last100+m of the main straight. Too much wing (AoA), and it runs into the drag wall too soon and again, limits top speed, but that might also mean plenty of rear DF and the resulting grip levels helping corner speed and acceleration out of the corner. Only focussed testing can get these compromises right. If you have reliable info from other competitors that might help get up to speed but they MUST be comparable cars. With all respect to Mark, and acknowledging that his experience can supply valuable insights, the differences in the cars means that car-to-car lessons need to be handled very carefully, and interpreted in the light of those differences.

Is the car instrumented? That is one area that Mark can give hugely important guidance. Going fast at these high profile events is all about data: being able see not just that the car is faster, but where, how and why.

Ok, my 2c has just run out, and I don't have any more to put in the meter

greenMachine wrote: With all respect to Mark, and acknowledging that his experience can supply valuable insights, the differences in the cars means that car-to-car lessons need to be handled very carefully, and interpreted in the light of those differences.

Agree 100% and no offence taken.

greenMachine wrote:Seat time. And some SERIOUS testing, done 'scientifically' (write it ALL down, change one thing at a time, etc).

This!

greenMachine wrote:I am not sure if that wing is the best, it is 3D and can be quite draggy.

This. The wing has separation issues around the mounts and is not as efficient as the posted data. I can link the video on where the separation is and give an idea of how much downforce is lost!

NitroDann wrote:Is there anything you learned about the particular track regarding aero Mark?

Personally I would setup the car to make use of the aero on the corners and sacrifice straight line speed. This is especially for T1...

I posted this in my build thread, it was a side result of the wing development... The blue line that is a 1:36.19 lap, the orange is 1:41.15 (simulated on my cars setup but with different aero packages). However, decreasing drag by 10% on my current setup could achieve a lap time of 1:44.61, if I could drive it as per the simulation...

Hmmm by Eipeip, on Flickr

What this does show, is that, at least for SMP having a faster corner speed is in preference to sheer straight line. Hence a 3D wing may not be the best for SMSP (as previously mentioned). Further, a swan neck will remove the separation at the mounts.

With respect to the splitter, again this will take a bit of development, unless you have it designed. Whilst the 'crusher' has its advantages, there are some small changes that can be made to increase its downforce. Further making the 'mouth' as small as possible and not having any brake duct holes will reduce drag and improve downforce.

Depending on brakes, you may opt to go light and not use ducts on the premise that you will only need them for 1 flying lap. However, in clubsprint there are at least 20 cars on the track at once and 'timing' your hot lap is difficult especially if the session is called early. My tactic was to try and do the hot lap just after the warm up lap, in general this worked. A 1:38 is fast, especially on AD08R's!

If you can download the VBox circuit tools software I can post some files that I have. I have also been sent a file that has a 1:43 sec lap, this will help you 'visualise' what you need to do.

I have a few big changes to do to the car this year and they are not power related! Hopefully on 16/03/18 I can add another mod to the list!

Happy to keep answering questions

1:45 is about a 1:47 at Phillip island. I haven't done the track up there yet, so need to work on Phillip island times in my head. I plan on entering Clubsprint as well. ;)
I have done a 1:41 equivalent on your track in a basic road car with basic aero and a stock motor, SE turbo, manifold, down pipe, etc. But using 225/50/15 A050's. So to go sub 1:40 is possible with a confident driver, more power/aero/tyre. And less weight. I am still unsure how much you can gut cars for Clubsprint class. I know the basic panels stay, bumpers an bonnet can be carbon fibre. We should be able to run a fastback, as the S2000 guys have in the past.

I will make a big wing, and splitter/airdam to balance it out. The only tyre we can run is 18" really if we are to get wide tyres. Maybe a 17" but I think they have a larger rolling diameter. Haven't looked in a while. Your a long way in front of me if the car is running.
And don't rest thinking you have to match last years podium times. I would aim to be 2 seconds faster. The wheels and tyres are the problem for MX5's. What are you planning on running?

I think the biggest struggle for us will be finding enough weight to pull out of the car without spending heaps on carbon fibre parts.
For now we will just find the easy cheap gains and see how far we can go.

For tyres, I have 17x9 wheels at the moment, and will be running 255 tyres and see how we go for times and traction.
I may need to find some 18s if we run into problems.

I will aim to get the car ready within the next month, then just get as much seat time as I can, and get a good set of data logs for us to start with.
Then we can make the appropriate changes to the car based on where we are lacking.

I have put a deposit down a while ago on an NA fastback, but waiting for the next invoice *wink wink*

That is a very quick time, but i know you are a very experienced driver, so I will try to start with improving that first.

Did you see this rule “each vehicle with a performance level, based on lap time, quicker than a 1.45 min lap of Sydney Motorsport Park Grand Prix Circuit must be fitted as a minimum with a CAMS Type 2 Safety Cage (half cage).”?

By the looks of things clubsprint will be difficult to be selected based on some of the cars I have heard about entering this year. Hopefully there is still a soft spot for NA cars

I think coming out swinging looking for first place at your first try at an event like this is probably unrealistic.

Getting a sub 1.40 and making it home in one piece (car too) would make me happy. But its Kens car and his race meet not mine.

I believe most of the time will come from testing and setup and driving, im glad we have got it running with 6 months to go, gives plenty of time.

Dann

I can't contribute much to the discussion of on track dynamics, but I do have a question regarding the power and the driveline.

We all know the 6-speed is at risk somewhere beyond 300whp (I'm sure there's a more relevant torque figure out there, but I'm not sure what it is), and at 450whp this car's gearbox must be on the raggity edge. Dann, I know you tune the car to have a smooth delivery of power and torque to help prevent any damage, as shown in the dyno, so I can see you'd be fairly safe rolling into the power from 2000rpm to peak hp/tq.

But what happens when you shift at 7000rpm and re-engage the power at ~5500-6000 rpm? Wouldn't that cause a great spike in drivetrain stress? What can be done to lessen that?

The car sounds pretty awesome, and that power curve is excellent. I'm looking forward to seeing how the car develops and gos on track!

Solid driveline mounting keeps the gearbox case from flexing which keeps the gearsets aligned and better at being gearsets.

Outside of that you keep under 350ftlb using the same calculation method ive posted over and over and you pick a clutch and also a technique which will be unlikely to shock load the parts beyond 350.

But I am no expert, Im just applying the theory I understabd as best I can and learning along with the rest of the community.

Dann

Cool, I'm just trying to understand the theory also. Good luck to the driver and the car! That power is quite awesome.