22 replies to this topic

[John Clayton]

My newly acquired rally car's oil pressure is fine when cold, but when its hot (both for road driving and when driven on an event) it is as follows:
900rpm: 20psi [oil light flickering at idle]
1000rpm: 25psi
2000rpm: 50psi
4000rpm: 75psi

The garage put their standard oil (15W/30 or 15W/40) into it but I think this may be part of the problem.

This is the oil that Mini Sport recommend for an engine of this power:
http://www.minisport..._MIL20-50C.html

but this is what Millers own technical adviser recommended:
http://www.millersoi..._MOTORSPORT.htm
which appears a lot better, and I've ordered some to try it.


FYI, the car's spec is:
Capacity: 1300cc (re-bore +20 thou)
Head: ported and polished
Balanced crank and rods
Cam: Piper
Air Filter: K&N
Carb: Probably an HIF40 which is 1 ¾”
Centre oil pick up pipe
Lightened flywheel
Power: at 106bhp @ flywheel on rolling road
Distributor: Aldon electronic (new) -Does it have (or need) Breakerless ignition?
4 core Radiator with low-resistance 4-blade fan

It ran quite hot (3/4 up the temp gauge) througout a 1.5 hour gravel test session recently.


I've since been running:
Millers CTV 20w50 motorsport oil
Very high performance semi-synthetic competition oil for engines with the transmission in the sump.


Generally the oil pressure remains fine but we found when running the car on a very hot day in an Autosolo where it was triple-driven (3 drivers so not much break for the car although the runs were only 60 seconds each) that mid afternoon the oil pressure was fluctuating oddly -it was thought perhaps due to a faulty oil pressure relief valve.

However, subsequently, no problems have been noted.

That said, on an overcast and neither cold nor hot March day, the car did 6 minute Tarmac stages. By mid afternoon , the water temp would be slightly higher than the middle of the gauge after finishing each stage. The cooling system has recently been thoroughly cleaned with RADFLUSH and a hose before refilling with anti-freeze & distilled water, but the temp of the engine was apparently sufficiently high to make the oil pressure drop to the point where the oil light was flickering (below 20psi) at idle. By holding the revs up to 1500 or higher the oil pressure was maintained OK -so we stuck to doing this.

The key questions are:
1. Do you agree with my new choice of oil?
2. Is the reported oil pressure normal?
3. Do Minis of this ilk normally need oil coolers?
4. Would the oil cooler need to have a Thermostat? I've heard that the Thermostats you can buy arent set to the optimum temp for Mini oil in a competition vehicle (Pitstop @ Brize Norton -Mini Se7en racing gurus).


Full spec on the car's blog:
http://www.theminifo...x...=129848&hl=

Edited by John Clayton, 01 April 2011 - 05:17 PM.

[Spitz]

Nothing wrong with 20lb at idle ( hot )

[MRA]

The oil lamp flickering is possibly due to the pressure transducer being a higher pressure switch. Also if th eignition is retarded the oil light will often come on earlier than normal, although the figures given above are ok.

[bmcecosse]

You NEED an oil cooler for an engine with that power - the bigger the better - 19 row will be ideal. The pressure is 'ok' but not fantastic. An engine with that power and competition use should be stripped down regularly and bearing shells/oilpump replaced if worn.

[MRA]

you may of needed an oil cooler 30 yesrs ago fo rthat amount of power, however 100 bhp without an oil cooler will work just the same, if you were doing a long event then yes an oil cooler would be recomended.

still 100% convinced that a rolling road tune will almost certainly remove the "hot oil" issue which I have seen on numerous ocasions and the cause in every instance has been retarded ignition.

[Richard1]

Before I answer, I'll give you an introduction. My business is oil. I've been in this for 15 years, solving problems for people, doing root cause analysis and writing maintenance bulletins (but 95% in Spanish).

I'm semi-new to the mini, having finally bought one (see presentations). But not at all new to the concept and use of motor oils in transmissions and shared compartments.

You may in fact have issues that can be improved by more cooling, and normally 20 psi is not too low. BUT: I would not use anything less than a full synthetic in a motor/trans assembly in racing or hard circumstances. The reason is shear. The oil you mention is satisfactory for many Mini's. But a regular 20W-50 is basically a 20W with polymers to keep the viscosity at a SAE 50 (>16.3 cSt) when hot by crossing and expanding their fibers. A full synthetic SAE 50 is synthetically built to act thinner in the cold. A synthetic 5W-50 is a SAE 50 that acts as a 5W in cold, and can also be labeled 15W-50 or 20W-50 (by API standards) because it meets all of those requirements. A semi-synthetic is a combination of a mineral and synthetic, using some lesser quantity of polymers. There is no standard as to how much synthetic has to go into a semi-synthetic, or whether it is mixed with group I base oil or group II base oil. Group I needs more polymers than group II for the same viscosity index (spread between the xW-xx viscosities).

The problem is that polymers shear or are ground down in gears. They also lose their strength either temporarily or permanently in heat. You want to keep polymers out of transmissions whenever possible, or limit the extreme pressures or temperatures.

Your best performance will be with a good full synthetic (PAO if possible) oil with a diesel CI-4 rating. If you want to get further into it, read the 30 page+ paper listed in my signature.... I plan on using a full PAO synthetic API CI-4 SAE 5W-50 even though I won't be racing.

And ask more if you want. I'm just getting started on my Mini, and still have two businesses to run, but I'll be around, probably asking more questions than answering.

[bmcecosse]

I was assuming a Rally Mini would be sporting a good solid sump guard! Hence the NEED for an oil cooler. Rally engines also tend to be doing high revs/working v hard at lowish speeds - so not a huge amount of forced cooling from air flow. It's certainly true that modern oils are much better than they were '30 years ago' (make that 40 for me........) but I had endless trouble/grief/expense until I fitted oil coolers to my Minis. Only exception was my Autocross/Sprint car which was only doing short/sharp runs (although usually double entered) - but I felt the 'contact' risk outweighed the need for the cooler.....

[Cater_Racer]

John,

I have a similary specification engine (possibly from the same source)

You NEED an oil cooler.

I run Millars CTV oil, but temperature is the killer. You need to get the heat away,

the radiator is only half the aswer, and sump guards kill the sump cooling.

[Cooperman]

John,

You MUST have at least a 13-row oil cooler for a rally Mini as the sump guard removes a lot of the air cooling across the sump fins.
The biggest problem with the Mini is that the gearbox shares the engine oil and that gearbox was originally basically designed for the A35 which required an EP80 gear oil. So, what a rally Mini, or any Mini come to that, needs is a top quality 20w50 oil. I used to use the American oil, Kendall, but that is NLA in the UK, so I've switched to Valvoline Racing 20w50. It's a top quality mineral oil and I've never had any oil pressure problems on any events I've done. I did once try a Shell Synthetic, as recommended by a Shell oil specialist, and I blew the mains, big ends, cam bearings and gearbox syncros on the Longleat Stages Rally. It cost me over £700 to sort that lot out and that was when a guy whose expertise I highly regarded said that I must use Kendall or an equivalent.
So, go for a good sized oil cooler and Valvoline Racing 20w50 and you'll have no further problems, of that I'm very sure.

Peter

[bmcecosse]

The problem with small oil coolers is that they can restrict the oil flow when it's cold - the oil goes through the thin parallel passages in the cooler - so the more passages the better. And of course - more cooling too when the oil is hot! Win-win.

[Richard1]

John,

You MUST have at least a 13-row oil cooler for a rally Mini as the sump guard removes a lot of the air cooling across the sump fins.
The biggest problem with the Mini is that the gearbox shares the engine oil and that gearbox was originally basically designed for the A35 which required an EP80 gear oil. So, what a rally Mini, or any Mini come to that, needs is a top quality 20w50 oil. I used to use the American oil, Kendall, but that is NLA in the UK, so I've switched to Valvoline Racing 20w50. It's a top quality mineral oil and I've never had any oil pressure problems on any events I've done. I did once try a Shell Synthetic, as recommended by a Shell oil specialist, and I blew the mains, big ends, cam bearings and gearbox syncros on the Longleat Stages Rally. It cost me over £700 to sort that lot out and that was when a guy whose expertise I highly regarded said that I must use Kendall or an equivalent.
So, go for a good sized oil cooler and Valvoline Racing 20w50 and you'll have no further problems, of that I'm very sure.

Peter

That Valvoline is a decent additive package, although you will get some shear. An oil analysis will tell the permanent shear. They do not list the HTHS viscosity on their spec.
Valvoline Racing oil

[Cooperman]

John,

You MUST have at least a 13-row oil cooler for a rally Mini as the sump guard removes a lot of the air cooling across the sump fins.
The biggest problem with the Mini is that the gearbox shares the engine oil and that gearbox was originally basically designed for the A35 which required an EP80 gear oil. So, what a rally Mini, or any Mini come to that, needs is a top quality 20w50 oil. I used to use the American oil, Kendall, but that is NLA in the UK, so I've switched to Valvoline Racing 20w50. It's a top quality mineral oil and I've never had any oil pressure problems on any events I've done. I did once try a Shell Synthetic, as recommended by a Shell oil specialist, and I blew the mains, big ends, cam bearings and gearbox syncros on the Longleat Stages Rally. It cost me over £700 to sort that lot out and that was when a guy whose expertise I highly regarded said that I must use Kendall or an equivalent.
So, go for a good sized oil cooler and Valvoline Racing 20w50 and you'll have no further problems, of that I'm very sure.

Peter

That Valvoline is a decent additive package, although you will get some shear. An oil analysis will tell the permanent shear. They do not list the HTHS viscosity on their spec.
Valvoline Racing oil

I am only describing my experience in motor sport with the Mini running high revs, high temperatures and a lot of transmission abuse. I was recommended to the Valvoline a few years ago when Kendall became NLA and have been well-pleased with the competition results I've had with it. The failures I have had have been more related to component failures under shock loading on rallies than gearbox or engine wear. Pressures have always remained good even at high engine temps.
You can see why I'm reluctant to try a synthetic or semi-synthetic after my expensive experience a few years ago. It's not a question of oil cost as I'll pay whatever is necessary to get better performance from an oil, but it's hard to move away from something which has proved so good over years of motorsport, if you see what I mean.

[Richard1]

True, it might perform very well. Like I said, the additive pack is good for boundary lubrication which is especially needed in the transmission. The balance is toward anti-wear, rather than a 50/50 with cleanliness, so it wouldn't be as good in start and stop cold weather for long drain intervals.

But I wouldn't condemn all synthetics based on one experience, Shell uses more group III synthetics than PAO, and has more gasoline versions out there that therefore have less additives. You need those to get the EP protection.

[Cooperman]

I change the oil and filter after every rally, so sometimes the oil only does about 400 miles, including pre-event testing, between changes. It's always surprising how much steel filings come off onto the magnetic sump plug.

[Spitz]

I actually don't know of anyone using a synthetic in their classic MINI.
I for one wont be using it...yet....
As suggested ( proven ), a quality mineral oil of correct weight works well in the shared components of a MINI.

Since finding out GTX no longer contains the ZDDP levels as before, I've been using GrandPrix 4 Stroke 20/50 motorcycle oil. No issues. ( Can't get the VR1 here )

I do recall...but not where....reading that synthetic should NOT be used in a MINI due to the shared gear/engine design.