Oil pressure question

[Esprit2]

The flaw in that theory is that the Pressure Relief Valve (PRV) is built into the pump itself. (Snip)... "IF" the pump's PRV is working, then pressure at the pump outlet should never reach 6-7 bar (87-101 psi).

No theory Tim.
These are real world readings on my system with two identical 7 bar VDO sensors connected to the same gauge. 7 bar is the indicated post pump pressure from cold - therefore the pump PRV must be set at, or above, 7 bar ..I say above 7 bar because my first pre-filter pressure sensor (within the filter housing) is POST oil cooler and I suspect (I've not measured it) there will be a pressure drop across the cooler too..

Peter,
I'm not arguing your schematic's pre & post filter sensor logic. Heck, I'm not trying to argue with you at all (although every conversation with you seems to be an argument). Your 7 bar readings are real world "GAUGE" readings with no evidence that they are accurate... and in-car instruments are often something less than laboratory quality & calibration. I don't have an Excel (I have two Eclats, an Esprit and a Europa), but the VDO electric oil pressure gauges in Turbo Esprits are known to be unreliable. Never panic when your Turbo Esprit's oil pressure goes weird, it's probably just the VDO instrument... again. Given my experience with many of them, I wouldn't bet on your VDO oil pressure gauge being trustworthy.

"IF" your Excel's two senders and one gauge are accurate about a 7 bar reality, then the PRV is not working... it's stuck closed. That isn't a statement to contest anything you're saying, it's just a simple warning to alert you to something else of which you should be aware. I'm NOT trying to challenge your schematic or dual-sensor system. Calm down.

See my previous schematic for the position of the sensors - if you can tell me where the PRV is located post pump I will redraw for the sake of clarity (and the debate).

As I wrote in my June 24th post, the PRV is INSIDE the pump, not post-pump. A correct representation would be to draw it in white 'on' the pump symbol. Or, if you wish to approximate it with discrete items external to the pump symbol, then put a spring-loaded ball valve/ pressure regulator immediately outside the pump's output. From the ball valve's vent port, draw a return line around the pump to a 'T' fitting just outside it's inlet side. There is no part of the pressurized oil system, outside of the oil pump itself, that is not subject to the PRV's influence "IF" the PRV is working. At 6-7 bar, it's NOT working. That's all I'm saying. Please don't hang me for other things I haven't said.

At some point Lotus changed the earlier 5 bar VDO to a 7 bar gauge and sensor - they must have done this for sound reasons

:-/ Lotus also installed a tach that reads engine rpm well beyond the engine's rev limit, and a speedo that reads faster than the car can go. It is not prudent to read any, "they must have intended..." logic into any of that. Lotus used whatever components were readily available for a favorable price.

[Phantasm]

91 Excel SE
VDO 1-7bar range
Cold Start, pretty much any outdoor temp: 6-7 bar
Warm (15 minutes running) 4 bar under throttle, 2-3 idle.
Hot (20 minutes or more than basic Highway use) 2.5-3 at 3100 RPM throttle; .5-1 idle.
Results are pretty consistent regardless of ambient temps which range from freezing to 98*F (36.6C) I am running a 74* Tstat.
It's been like this since I bought it. Came with 20W50 Valvoline; No change when I switched to 5W50 Full Synth Mobil1 w/ zddp maxx zinc additive;
K&N Filter, the good one, with the wrench nut on it.

[Lotus-e-Clan]

• • Tim if we were having a face to face conversation you would realise a) I'm not an aggressive type b) I'm not *that* argumentative (just for the sake of it) c) I am pretty calm within my own skin, and d) I regularly take the piSS out of myself (and sometimes enjoy having the pi$$ taken out of me) .
    
    ... within my writing (style) I'm attempting to be accurate and concise and intend to come across as 'matter of fact' for the sake of problem solving ..so my writing style may well appear as you receive it (without social nuance and maybe without humility?) ... but there is no intentional challenge on my part to the integrity of the content of your posts! This is *clearly* a major short-coming of mine when it comes to written online communication.
    
    Sorry if you feel affronted - this is not what I want to waste my time on - or yours. It's a stupid waste of time! I have an ego like anyone else but I bet you it sits to the left of centre of a normal population distributon! I only want to contribute to understanding for like-minded folk sharing a specialist interest- I am not the 'fountain of all knowledge'. - I generate and collect data - then attempt to interpret those data with insights that are limited (as ever) by personal experience and understanding- but hopefully it's a catalyst for learning (for me too). I would encourage others to do the same - the more real world data generation/collection along with insightful and/or challenging interpretation - the better.

Back to the oil pressure problem'
It matters not (to me) what ABSOLUTE pressure the the pump PRV is providing (my definition of ABSOLUTE:- a 7 bar reading really *is* 7 bar). The point of my post(s) on his thread is to point-out that I have devised a sensor system to measure the pressure drop (delta) across the filter. The pressure drop (delta) is as you might expect if the oil viscosity is compatible with the matrix and therefore passing through the filter matrix. Using thicker oil (esp during cold winter months @ <4C ambient) I have measured zero pressure drop (delta) across the filter on cold start-up which indicates logically that the the BFRV has opened.... there is now lower resistance to (pump) systemic pressure - because the matrix is bypassed - so high readings equivalent to PRE filter values are found at the POST filter sensor.
My system is pretty robust at showing RELATIVE values (alternative terms/definition for RELATIVE values:- DELTA, CHANGE, HIGHER/LOWER).
In this context relative values (delta) are more important than absolute values (accurate values) when you want to measure systemic effects -which is what I set out to do, and hopefully have achieved.

• • For clarity (!?) Accuracy = the ability to measure absolute values. Precision = the ability to measure reproducible values. That might sound 'cooky' to some engineers but it's common parlance from a biomedical scientist's perspective.
    
    ie the OE electrical VDO pressure gauge/sensor system is likely to be both inaccurate and imprecise- I fully accept that. It's the precision of the VDO that's more important to me - not the accuracy. When I collect a set of data using the VDO I am very mindful of its short comings but I'm looking for significant change (delta) and even the humble (well-slated) VDO is capable of separating absolute black from absolute white.

[fueltheburn]

Worth noting Petes comments come from a long term investigation from well over a year ago where the pressure delta was one of the concerns that the "Lotus approved filter" seems to fail sigificantly from cold.
Having a real world comparison where you can check before and after pressures is not to be sniffed at. I have the same switchable system but with digital gauges.

Having investigated the same at length, is the reason I do not sell the "Approved Lotus filter". It is overpriced and not up to the job. The pressure drop on initial start up is slower to recover than other filters.
My exclusive use of K&N gold series is as a result of the proven delta upon start up likely to be as a result of the resin filter media as opposed to a paper media. The resin media still filters down to a ridiculously low micron level.

Pete's style can sometimes be abrupt but I don't see him enforcing his views on anyone. His provided knowledge and diagrams on items such as carburretor tuning is a valuable source on this forum.

Your input has also been a welcome change from another source across the pond.

A guage is merely a reference to show change from one value to another or an early warning sign when on the move. If you don't trust a gauge... change it.

[CHRISYD]

I use 20/50 semi synth, lotus or mann filter, outside temp doesn't seem to make any difference to dial display pressures. it takes 3 secs for the needle to move off bottom then it goes straight to 5 and stays there at any speed until hot. Then i get 1-2 on tick over but when you raise the revs, it goes to 4-5 and stays there then drops back to 1-2 only on tick over. if i was driving on the motorway for ages at 3000rpm, it might drop to 3-4 but that's it.

[RED BARON]

Hi. I read all the threads about oil pressures on here, but I am a little confused what it all means. I have done a lot of engine work on
my Excel from all the belts and including a full service. I finally got it taxed yesterday and took it out for my first drive of it.
When I put the oil in I used Castrol 10/60 fully synthetic as recommended by SJS & Halfords. after putting it in was told by a number of people on here I should have used standard 20/50.

When I took it out yesterday & today both at about mid day didn't take it over 2000 rpm and 50 mph just in case.

The oil pressure gauge was all over the place yet on my other classic car V6 3.0 lt once started stays at about 45/50 psi at 950 idle
or at 3000 rpm.

The gauge on my Excel showed :
Start temp 0 degrees second mark on dial stationary
Warm temp 40 degrees second mark on dial 2000 rpm moving after 5 mins running
Hot temp 90 degrees dropped just above first mark on dial 2000 rpm moving after 10 mins running
Hot idle temp 85 degrees dropped just above red band on dial 1000 rpm stationary after 10 mins running

After all that info my question is on the oil pressure gauge it starts at 0 Bar then a red bit all the way up to 7 Bar can someone please tell me what the pressure is at the end of the Red band and what pressure each mark is all the way up to the end one which is 7 Bar.
( In bars and psi if possible ).

Many Thanks.
Ian.

[DavidOliver]

As a latecomer to this post;

I have installed and only believe in the mechanical guage readings, not electrical.
If I wanted to you can always attach temporarily a precision pressure guage to get absolute readings.
I suppose the most important pressure reading is at the ends of the crankshaft, it can be done but I
have not seen anyone bother.

Any recordings of pressure readings, air and engine temperatures, oil type etcetera, needs to be
accompanied with miles/kms since the engine was last fitted with bearings/crank condition, cam
bearing condition.

Dave the cog.

[richardw]

After all that info my question is on the oil pressure gauge it starts at 0 Bar then a red bit all the way up to 7 Bar can someone please tell me what the pressure is at the end of the Red band and what pressure each mark is all the way up to the end one which is 7 Bar.
( In bars and psi if possible ).

Many Thanks.
Ian.

I'd imagine that the end of the red band is 1 bar and each white marker denotes 1 bar (therefore reading 2-7 bar)

ATB Richard

[pistolpete]

SO I didn't think that , I assumed the first white mark was 1 not 2 then there's a bigger gap between the 3rd and 4th so I assumed that was 2 bar. If your right then my oil pressure is much better. Strange how each mark seems a different distance

[MrCoolA]

don't stress about the accuracy of the gauge or the sender, remember cars generally don't have gauges just stop/go lights...If you have pressure just be happy...………………..
I run a high hp and high revving 912 with gauge and sender and a 2011 Elise with stop/go light without and I really cant loose any sleep over either of them

life is way to short to get stressed about it...........

[dancroft1984]

I run with valvoline 20/50 and K&N filter.

cold start 5 or just above
normal running around 4
warm idle 2
hot idle just under 2 say 1.8

when I first got the car it always went off the scale on cold starts and for a few miles afterwards and dropped to about 5 when it warmed up. After a couple of double oil changes to clear out the sludge and an oil cooler change and then several more changes it now runs as above. It's possible the pressure relief wasn't working and now is.

Mark

Good to read this. At the MOT my oil pressure was dropping to 2.5 bar. Only ever seen it above 3, but then I've never had the chance to get it hot and idling. Looks like I was getting a little worried over nothing.

[pistolpete]

Hi , So my oil pressure dropped this year during the summer sat in a lot of traffic and for the first time dropped at idle to 1.4bar. Which did worry me , having revisited this link doesn't seem so bad, but still a worry. I used PNM filter, and Valvoline 20/50 some left over from last years oil can plus some from there new receipt looking can.
So my question could it be the filter, would it be worth doing the oil relief valve, and changing to a mechanical pressure valve as there seem to be a distrust of the factory ones.


thanks pete

[rbgosling]

Firstly, I don't think you need to worry, that sort of pressure is not unusual for hot idle.

It looks like you're using good quality oil and filter, nothing wrong with that, in fact your oil is slightly thicker than the 10W-60 that would have been original Lotus recommedation.

At that sort of pressure, the pressure relief valve should be fully closed, it only starts to open at higher pressures to prevent the oil pressure getting too high. So, unless it's somehow not closing fully, I don't think messing with the PRV will make any difference.

[Lotus-e-Clan]

I.4 bar is ok stinking hot at idle.

I've got data using two pressure sensors pre and post filter to show about 1.5 bar COLD pressure drop across a high flow K&n racing filter, and just less than 0.5 bar drop over the filter when stinking hot using Castrol edge 10 /60.

For 5/50 Valvolene racing (current favourite synthetic) I get about 3psi drop across the filter when stinking hot.

Other filter data may vary!

[pistolpete]

Ok , as always thanks for info and help, I will use a K and N filter next time to see as it has dropped lower than usual