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Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Sat Feb 09, 2019 9:27 pm
by zippyonline
delta0 wrote: ↑Sat Feb 09, 2019 6:09 pm
Looks like Felix from Living with a Rotary is in a club of its own. Over 400 miles in an S1!
Cabby who is an ex member/owner also managed it. Also notice how it had the older non Milltek/petit racing exhaust on it, they did that a while back!
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Sat Feb 09, 2019 9:55 pm
by warpc0il
Nickp47 wrote: ↑Sat Feb 09, 2019 7:06 pm
Fair play to him, wonder what 42psi tyres do to the handling!?
As an aside, I did some data analysis with the Ford Powertrain engineers a few years ago, looking at the correlation between rolling resistance (and therefore fuel consumption) and tyre pressures.
On a perfectly smooth track the rolling resistance does reduce slightly if you increase the pressure, up to about 20-25% over the "normal" running pressure. beyond that there's no advantage.
However, on a test surface that better represents a real road, the benefit disappears at around plus-15% and then the rolling resistance goes up significantly as the pressure is increased further.
The actual numbers were slightly different with a variety of test vehicles but the pattern was much the same.
Once the tyre gets too hard, any imperfection in the road surface is no longer able to locally deform the tyre and the whole wheel has to rise to roll over. The energy required to lift the wheel is much greater than the scrubbing and sidewall deflection associated with a softer tyre.
What they did find is that an under-inflation by as little as 10% would cause a measurable increase in fuel consumption.
A similar increased could also be caused by have the steering geometry "off", especially front or rear toe, such that the wheels are trying to send the car in different directions, again a surprisingly small error was required to have a significant impact on fuel consumption - e.g. much less than can commonly be caused by bumping a kerb.
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Mon Feb 11, 2019 2:24 pm
by Dr. FrankenRex
As Zippy said, there's another S1 (ex)owner who managed it a while back too - although his was a 192.
As for the exhaust and wheel notice, this was done after the rebuild, and after the initial tuning session where the found the fuel pump to be struggling at high RPM, but before they replaced the fuel pump and before they finalised the tune. As such it has been rebuilt and 'run in' by then, as well as tuned across the rev range they were using
That puts me count at 3 owners in the 400 club, with each one owning a different variant of RX8
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Mon Feb 11, 2019 3:19 pm
by PeteH
warpc0il wrote: ↑Sat Feb 09, 2019 9:55 pm
On a perfectly smooth track the rolling resistance does reduce slightly if you increase the pressure, up to about 20-25% over the "normal" running pressure
Rolling Resistance.jpg
You can see that the rolling resistance at 20psi is around double what it is at 50psi. And it doubles again if you lower it to 10psi. All that rolling resistance gets turned into heat. That heat is the direct consequence of the extra petrol you are using (you are burning petrol to heat the tyres). It is also why low tyre pressures will cause your tyre to fail. The extra heat causes parts of the tyres to exceed their temperature limits, and the bonds break down, so it delaminates, degrades, and blisters.
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Mon Feb 11, 2019 4:34 pm
by zippyonline
Have you got the corresponding "grip" chart vs psi... (yes I know this is waaaay more complicated, but there must be some rules of thumb?).
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Mon Feb 11, 2019 5:45 pm
by PeteH
Nice try!!
The rolling resistance versus pressure is a fairly universal trend, regardless of the tyre type and size. So this plot applies reasonably well to all road car tyres. The grip versus pressure plot is tyre dependent, temperature dependent, load dependent, and has many other dependencies. There is no universal answer, and each tyre has to be independently tested. Even then, it's one of the most difficult metrics to extract.
You know my job, so you know the answer is probably yes, but you also know that I'm not likely to be posting it here.... Sorry.
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Mon Feb 11, 2019 5:55 pm
by warpc0il
I was aware of that chart, or at one's like it, and so were the engineers that were doing the testing.
However, the curve changes as soon as the road surface isn't smooth and the sort of ruts you see on real roads changes it dramatically.
The guys were surprised by how much, as were Bridgestone, that had test-rig results that suggested much less difference.
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Mon Feb 11, 2019 6:06 pm
by Dr. FrankenRex
I'd imagine that the 'rough roads' principle - as I have dubbed it - wouldn't be as impactful on the motorways though?
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Mon Feb 11, 2019 6:28 pm
by wiggles
warpc0il wrote: ↑Mon Feb 11, 2019 5:55 pm
I was aware of that chart, or at one's like it, and so were the engineers that were doing the testing.
However, the curve changes as soon as the road surface isn't smooth and the sort of ruts you see on real roads changes it dramatically.
The guys were surprised by how much, as were Bridgestone, that had test-rig results that suggested much less difference.
There has been similar tests for road bikes (pedal variety) where everyone used to think skinniest tyre possible at highest pressure would offer the least rolling resistance but more recently manufacturers have tested and realised a wider tyre at lower pressure actually offers lower resistance in "real world" conditions eg. Not perfectly smooth roads. Not as initiative as you might assume but makes sense.
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Mon Feb 11, 2019 7:23 pm
by PeteH
I agree with the concept that a stiff tyre can cause an increase in rolling resistance but, as with all engineering, it depends! Here's a couple of extreme examples:
When the pneumatic tyre was in the initial stages of invention / development, an experiment was conducted where the force to pull a push bike was measured. A "standard" solid rubber tyre was measured against a new-fangled pneumatic tyre. The pneumatic tyre won hands down, and became the dominant technology. On a perfectly smooth surface a solid tyre would have much low rolling resistance, but on a real surface the way a pneumatic tyre "flows" around the surface means it has much lower rolling resistance.
Trains have almost totally rigid "tyres" (i.e. steel wheels). They have these to minimise the rolling resistance. But they only work because of two factors; 1) they run an very smooth steel tracks. 2) The bogies have very compliant suspension, allowing the wheels to traverse over the joints and imperfections without resistance.
Basically, if you have a good suspension system, or a very smooth surface, you can afford to have more rigid tyres. For any given vehicle, suspension system, and road there will always come a point when the tyre is too rigid, and the rolling resistance will start to rise again.
Because this is a function of the car and the road, we tyre engineers tend to ignore it!
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Fri Mar 08, 2019 10:17 am
by bigpete8
Nowhere near but closest I've been to 200 for some time....
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Tue Mar 19, 2019 9:11 pm
by RX81977
First time getting to 300 from a tank. Mainly A and B roads, no dual carriageways or motorway cruising, well chuffed...
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Tue May 07, 2019 11:29 pm
by Luke0611
This should count? The last 16 miles would have been easy, just couldn't afford to spend the time (or money) fuelling the next morning at a service station just to prove a point
Sent from my SM-G960F using Tapatalk
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Wed May 08, 2019 2:24 pm
by ChrisHolmes
At least another 40 miles left there, you may have even scrapped into the 350 club but that is stress full last 20 miles or so!
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Wed May 08, 2019 5:02 pm
by Vian
My main restriction in making the 350 club is living in a part of the country where the motorway driving that maximises the potential range culminates on the journey home of joining the M25 and having to head around it with no services until Cobham, and then no more services along the M25/M23 until Pease Pottage. The stress of that last bit with the fuel light on is taken to new levels when there's one set of services in a 50 mile section of journey!
300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Wed May 08, 2019 10:54 pm
by GreySilver Beast
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Thu May 09, 2019 8:28 am
by Vian
Just after you've passed Beaconsfield services? How thoughtful of them...
300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Thu May 09, 2019 9:20 am
by GreySilver Beast
Quite Chris, and if I known this then would of filled up at Beaconsfield instead
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Fri May 31, 2019 1:31 pm
by v-rex
ChrisHolmes wrote: ↑Thu Nov 01, 2018 8:21 pm
Dr. FrankenRex wrote: ↑Thu Nov 01, 2018 4:31 pm
6th all the way (in a stock RX8 anyway). You won't need to use 5th on any motorway in Britain, none of the hills are steep enough to trouble an 8 at 3,500 rpm.
Not going to lie, it's boring as sin warbling along at 60, but still. That's 6 hours and 40 minutes of driving, for reference.
I do hope your not motorway cruising at 60mph to run the engine in. Worst thing in the world constant light load, you need A or B roads with regular gear changing and variable throttle loading on the engine to ensure correct bedding in.
I think you know better though so not sure why I am posting this!
Been trying to think of quick ways of getting to the required 1000 miles, before an oil change, for my recently rebuilt engine.
I was planning motorway cruising at 70 mph in 6th but now I'll find some A and B roads..... annoying to do when you have limited revs but if it's runs in the engine better than I'll take the hit.
And also now you have a good reason to have posted this obvious ( to some ) point.
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Fri May 31, 2019 1:50 pm
by qwakers
i went for a blast round cornwall, then wales, then dartmoor to run mine in.
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Fri May 31, 2019 2:18 pm
by v-rex
qwakers wrote: ↑Fri May 31, 2019 1:50 pm
i went for a blast round cornwall, then wales, then dartmoor to run mine in.
Yeah, I did manage to go to near Cardiff and back for the first 300-400 miles which would have probably fell under the low load cruising no no but thankfully smart motorways and dufuses on the road made sure I was never at a truly constant speed.
Been finding driving routes to rack up mileage but so far I'd been avoiding A and B-roads as I feel impotent coming up through the gears, keeping to below 4K revs. It does feel a little like driving a diesel, changing at 4K, and inevitably I get some diesel repmobile behind tailgating me as my RX8 does seem to invite people wanting to prove their superiority to it.
I've got 250 miles left. I shall try to not squander it on motorway, but find a route with a good mixture of different driving loads needed.
Not done any measurements but fuel consumption so far looks good and I hope to be a 300+ addition to this list soon. I think the best I got on my old engine was 250, but usually it was sub 200 to a tank.
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Tue Jun 11, 2019 5:54 pm
by nightfire10
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Sat Jun 15, 2019 10:46 am
by PaulAV
320 miles on one tank and still about 5 trees in the tank, Coventry to falkirk so it's up hill, wonder if I'll get more going down the other way
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Sat Jun 15, 2019 12:00 pm
by ChrisHolmes
Should be good for 350 coming "down" as that's what I managed in the previous car.
Re: 300 Mile Club (S1 RX8s) or 325 mile club for S2 RX8s
Posted: Sat Jul 06, 2019 8:34 pm
by geofftl1000r
Took the scenic route from Manchester to Nottingham then jumped on the M1 to get back to Redhill. As I pulled into the garage I noticed it was on 295.7miles so went off to the next roundabout and it clicked over to 300! Wasn't hanging about either!