The Lotus Grand Tourers

I'm on holiday in Devon atm having made the trip down from North Yorkshire in the Lotus last Sunday. I haven't done a long trip in the Excel since Cornwall 2016 so I was a little on-edge about using it for a long trip untested since then.

Happily, so far, (touch wood) all has gone well. I expected some oil (and petrol) consumption because I haven't spared the horses (given limits), and I was well-laden with luggage including 13 bottles of wine and the wife (which weighs loads!).
That's said, petrol consumption doesn't look too bad having 1/8 tank left and just over 400 miles covered from full! Oil consumption is about 1mm from max which is amazing - given I used much more on the 2016 Cornwall trip.

I converted to Evans waterless coolant before the 2016 trip and the only cooling system /oil grade differences are ; 1) I let the coolant run HOTTER at 82C to 88 C this time (EWP temp controller setting) rather than @ 78 C for the 2016 trip and, 2) I'm using THINNER Valvoline synth 5W/50 instead of Castrol Edge 10w/60W. The lower oil consumption outcome seems counter-intuitive given I'm running a thinner oil / hotter compared to 2016!

I'm now thinking Nikasil liners may like running a bit hotter than I once believed - ie piston ring seal might be better at 82 - 88C rather than 78C? Certainly not thinking of going back to the thicker 60W any time soon.

Lotus-e-Clan wrote: ↑

Tue Sep 22, 2020 19:48

I was well-laden with luggage including 13 bottles of wine and the wife (which weighs loads!).

Lol, did you read that back before you posted it?

TAR wrote: ↑

Tue Sep 22, 2020 21:25

Lotus-e-Clan wrote: ↑

Tue Sep 22, 2020 19:48

I was well-laden with luggage including 13 bottles of wine and the wife (which weighs loads!).

Lol, did you read that back before you posted it?

Ooops!

Nice report Peter (I'll skip the bit about your wife!)

I'd be interested to know what oill pressure you get using the Valvoline 5w/50 (especially hot idle), and how it compares with what you used to get using Castrol 10w/60. The low oil consumption is interesting. Good fuel consumption too.

Cheers, Richard

richardw wrote: ↑

Wed Sep 23, 2020 17:26

Nice report Peter (I'll skip the bit about your wife!)

I'd be interested to know what oill pressure you get using the Valvoline 5w/50 (especially hot idle), and how it compares with what you used to get using Castrol 10w/60. The low oil consumption is interesting. Good fuel consumption too.

Cheers, Richard

Yes I can give you fairly comprehensive oil pressure and oil temp reports, I thought nobody would ask, so here goes.....

No point in explaining oil pressure without reference to both oil temperature and ambient air temperature:
The ambient temp on Sunday 20th September ranged from 18/20C in North Yorks (morning) to 26/27C south of Bristol (Brizzol) in the afternoon. I have TWO oil pressure senders and TWO oil temperature sensors, so I can follow oil temp and pressure changes meaningfully / diligently.

On the A1/M1 the SUMP oil temperature was 72C in the morning and 82C in the afternoon (on the M5 .... coincidently when my cruise speed pushed the limit.... ). The GALLERY oil temperature was 86C morning and 92C afternoon. i.e. @ 20C ambient air temps I got -14C cooling in the morning and @ 26/27C ambient just -10C cooling in the afternoon. At J16 (M5 Bristol) we were diverted off the M5 into the centre of Bristol through stationary city traffic therefore had NO oil cooling - here in the city, during the hottest part of the day, the sump and gallery temps equilibrated to 90/92C (Evans waterless coolant running 82 to 90C) !

With reference to the ambient and oil temperature time-lines outlined above, OIL PRESSURE was 4.5 bar @ 3200 rpm (70 mph) in the morning and 4 bar @ 3200 rpm afternoon. In Bristol's stationary traffic, oil pressure read 2 bar (@ 92C oil temp) @ 1200 rpm tickover (I have a light steel flywheel fitted and run a high idle speed). If the revs dropped below 1000 rpm (during clutch take up) I noticed the oil pressure dropped to about 1.7 bar (@92C sump/gallery oil temp).

EDIT: When the normal oil pressure sender (post filter) reads 4.5 bar @ 3200 rpm (70 mph) the PRE=filter pressure reads 5.5 bar @ 3200 rpm - i.e. the filter (a large High-flow K&N remote racing filter) caused a 1 bar drop in pressure.

Engine has done about 75K miles... i.e. ~ 36K miles during my ownership since 1998.

Great report Peter . I'm astounded at such a large drop in pressure through the filter - the "ordinary" filters must be even worse. I wonder how many reports of suspect pressure (especially at tickover) are just the result of the filter?

Pete

Pete Boole wrote: ↑

Thu Sep 24, 2020 14:10

Great report Peter . I'm astounded at such a large drop in pressure through the filter - the "ordinary" filters must be even worse. I wonder how many reports of suspect pressure (especially at tickover) are just the result of the filter?

Pete

Hello Pete
At IDLE the pre and post filter pressure difference is less in absolute (psi) terms....but I expect it's 'constantly relative' (%) across the operational range. I will collect some pressure data at IDLE for the current filter (it's about 3k or 4K miles old now) next time I go out.

IIRC, for a NEW K&N filter when I used 10W/60, the pre and post filter delta when the oil is HOT was something like 1/2 a bar at idle...I wrote it up somewhere but have forgotten the exact numbers.

Just as an experiment - if your remote mount still accepts an original-style filter - you could also do the same tests with an original filter to see what differences in pressure there are. I'm also considering a remote filter mount as well - if there's still room in that part of the engine bay!

Pete

Pete Boole wrote: ↑

Fri Sep 25, 2020 09:50

Just as an experiment - if your remote mount still accepts an original-style filter - you could also do the same tests with an original filter to see what differences in pressure there are. I'm also considering a remote filter mount as well - if there's still room in that part of the engine bay!

Pete

Good idea. The K&N has a greater surface area than std so one would expect better flow even if they share the same matrix pore size. Double whammy if the std filter has a smaller pore size for 40 weight oils and thinner. The K&N is more expensive too.

The remote filter set-up is worth the hassle if you can fit one. I managed to use both original oil cooler pipes - just needed a new return hose to the sandwich plate at the original filter location. The remote filter plate allows fitting of pre-filter oil temp and oil pressure senders. simple change over relays (and a dash switch) to have 2 sensors feeding the one gauge.

Remote on chassis bracket next to sump:




A second oil temp sensor was fitted within the sump plug after these pictures were taken.

Nice set-up Peter. I'm part way through building the supercharger brackets so should have more of an idea of space around that area soon. Thanks for the photos.

Pete

OK. took note of the pre- and post-filter oil pressure delta today @ tickover... 88C oil temp for both sump and pre-filter line temps in traffic @ 20c ambient ....less than 0.5 bar difference (so maybe only 5 or six psi). Bear in mind it takes 3 psi to 'pop' the non return diaphragm valve - so in summary - for Valvoline 5W/50 fully synth @ 88C, filter resistance to flow is negligible at tickover when oil is sinking hot: i.e. ~2psi in a used 3K miles filter.

However, double-checked the pressure delta @ 3500 rpm (88C) and it is definitely 1 bar lost via the filter.

Back in North Yorkshire. Engine never missed a beat.

A number of Range Rover Sports put in their place. I don't understand why it was only Range Rover Sports that wanted to have a go but their poor aero clearly kicks-in at high speed just when the Excel lowers it's skirt and flies... I think the light flywheel (and no belt-driven water pump) at high rpm helps the in-gear acceleration mind.