Crossflow oil pressure problem..

[JamesH]

Hello all,

1300 Xflow, in a Locost, so pretty standard. Has shallow sump.

After running for just a few minutes, just about hot, oil pressure starts to drop off from usual 50psi. By end of race its normally about 20psi when engine revving, lower if idling.

Crankcase breather exit does have a baffle, and pipe is fed back to the rocker cover, which in turn breathes through a pipe off the filler cap.

I was hoping that the baffle would have fixed this problem which I have had for a while, but seems about the same. I thought maybe oil thrown was being prevented from dropping back in to the engine from the rocker area (via pushrod channels) by crankcase pressure.

Using 20w50 oil.

The only thing I can think of is that the oil pump is a bit crap, even though its new, as supplied with the engine. Has anyone else had problem with new Xflow high pressure pumps?

Any other ideas?

Cheers all

James

[greenamex2]

You really need to know your oil temperature.

It could be the oil thinning out due to heat, or as you said oil being in the wrong place totally.

It could also be the pump being on it's limit.

[Tim Falce]

Worn bearings, pump, or both, crap oil, or the oil is getting too hot and too thin.

[phoenix]

I'm no expert on oil, but I used to run a crossflow.

The problem with the high pressure pumps is that they normally just have a higher rate spring (or just more pre-load) on the bypass valve. This works fine when the oil is nice and thick - in fact you can blow the seal on the oil filter! - but it is no good when the oil is hot and thin and the pump isn't generating the pressure.

The crossflow relies on a relatively low pressure but high flow oil system. There used to be a high CAPACITY pump option available, and that is the one I think you want, as it will help maintain the pressure when the oil is thinner (somehow!).

Either that, or 1) cool the oil more or 2) maybe use a more modern oil that will keep it's viscosity better. I take it you do have an oil cooler?

[Robyn Slater]

My sons got a similar prob. with his road going mini.
We were wondering about oil temp.the gauge reads around 120deg.
What would be a good operating temp for the oil?
Also the temp sender is in the sump plug,Im, not sure this is the best position.
Any ideas?

P.S. The engine is totally rebuilt.

Cheers

[R59]

Robyn, is that deg F or deg C? If it' C - that's probably plenty hot enough, you should think about a small cooler

If it's deg F, then it's pretty well cool.

Regarding the Crossflow, and with a standard pump, you're doing well with 50psi!! As has been mentioned, high pressure relief valves help beef it up initially, but you need more capacity, and Burton Power Products used to do an uprated pump (probably still do). I'm trying to recall all of the other people who did (do) pumps. I seem to remember Piper and Kent Cams doing them too. My own experience with a Crossflow in a Fiesta was that even a high pressure spring wasn't much use with the oil when it was really hot. I even went to mono-grade oil (R40) to help keep up the pressure.

But first things first. Get an oil temp guage. Maybe a cooler will be required?

So that's your mission for now....

Rob.

[greenamex2]

Originally Posted by Robyn Slater

My sons got a similar prob. with his road going mini.
We were wondering about oil temp.the gauge reads around 120deg.
What would be a good operating temp for the oil?
Also the temp sender is in the sump plug,Im, not sure this is the best position.
Any ideas?

P.S. The engine is totally rebuilt.

Cheers

Pub experts will come out with something like "you need it above 100deg to get rid of the water".

This is cobblers. Any decent dyno operator would shut down at these temperatures and find out what had gone wrong.

Somewhere between 75-90deg is a good temperature. Above 90deg and there will become an increasingly significant reduction in viscosity and the oil will start become less effective.

And yes, synthetics can 'cope' with 120deg plus. The oil will be fine but your engine will be less well protected.

The ideal place for the temp sender is in the return from the oil cooler before it goes into the main oil gallery. However in the sump is better than nowhere.

Of course if you are running an F1/F3/Touring Car engine then none of the above apply.

[R59]

You are talking in deg Celcius of course....

According to data that I have, which relates to a 911, is that the optimum range is 180 to 210deg F (82 to 98deg C), above that the viscocity drops off, and wear increases, therefore engine life fall dramatically.

Here, see this site:

http://www.elephantracing.com/techto...emperature.htm

Rob.

[JamesH]

Thanks for all the replies.

I have been having some overheating problems which a new rad and some more louvres in side of car will hopefully fix (OK in open air, but water gets to 100c when close behind other cars - I know, get in front would be better!). NOTE - oil pressure starts to drop off before engine starts to overheat.

I'll look in to getting a oil temp gauge - currently I don't have a oil cooler (most race Locosts don't run them), so where would I plug it in on a crossflow???

I'm going to change the oil and refresh it with Valvoline Vr1 20w50 to see if that helps.

It shouldn't been worn bearings as the engine is less than 1 year and only a few races since it was built. I'll check with the builder to see if he fitted high pressure or a HP/High capacity pump originally.

Cheers all

James

[phoenix]

As was mentioned earlier, running with hot, thin oil will increase wear rates, so while your bearings seem ok at the moment (you wouldn't get the cold presure if they weren't) they will wear our very quickly without adeqaute lubrication - and that requires having your oil at the right temp.

First step is fit an oil temperature gauge.

Don't worry about what the others do - if you are racing you need an oil cooler for sure. So get a cooler - the oild temp gauge will confirm that you need one I am certain. On the crossflow, a sandwich plate between the oil filter and the block provides the feed and return to the oil cooler. You can get them from many places, but Think Automotive supplied mine http://www.thinkauto.com/. They can also do the cooler and the pipes. They also do a thermostatic valve, which ensures oil only gets cooled when it needs to be cooled - which is a very good investment. I think they may even do one built into the sandwich plate, which is a really good idea and saves extra plumbing and can also be supplied with a hole tapped to take your temperature sender for the gauge.

I think if you do all of the above you may not need a high capacity pump.

[Locost47]

I used to run an oil cooler on my Locost racer and found that it did help as otherwise my oil temps regularly exceeded 130 degrees. Eventually i improved my water cooling and removed the oil cooler to save weight and pumping losses (every scrap helps when you've got next to no bhp!) and i haven't really had any problems with low oil pressure, though my water does now get a bit hot.

There are a reasonable number of race Locosts using oil coolers as our cars do seem susceptible to overheating. Next year i will probably go back to one for summer races at twisty tracks.

[phoenix]

Originally Posted by Locost47

I used to run an oil cooler on my Locost racer and found that it did help as otherwise my oil temps regularly exceeded 130 degrees. Eventually i improved my water cooling and removed the oil cooler to save weight and pumping losses (every scrap helps when you've got next to no bhp!) and i haven't really had any problems with low oil pressure, though my water does now get a bit hot.

There are a reasonable number of race Locosts using oil coolers as our cars do seem susceptible to overheating. Next year i will probably go back to one for summer races at twisty tracks.

For James's benefit, what oil pressure and temp do you see now towards the end of a race?

Any engine running at consistently high revs/power output generally requires oil cooling to be considered seriously.

The beauty of using an oil thermostat is that you only get the cooling, and the associated pumping losses, when you need them. Surely better to lose a couple of hp than a engine!

If the engine is running too hot you will lose power anyway - most engines perform better at about 90 degrees water temp max. At 130 degrees oil temp the water must have been close to 120 I would have thought, so the engine would not be making the best power it could.

[Locost47]

I've now realised who JamesH is (i'm a bit slow) and so i'm already aware of his problem!

My oil pressure is normally 45-50lb/ft when cold but doesn't drop below 20 even when stinking hot.

For my car there's a fairly distinct point when the oil gets too hot and starts dumping that heat into the water as the top hose temperature stays steady at 90ish for quite a while then shoots rapidly up to 105 and sometimes beyond.

I've just finished upgrading to a larger radiator and that seems to have improved my cooling by more than the area ratio led me to believe. Hopefully that will allow me to avoid refitting the oil cooler. I'm off to Donington on Friday night (£99 for 3 hours open pitlane!) so will give it a thrash there and see if the water still overheats. If it does then i suspect the oil temp will be the root cause and go back to the separate cooler.

Like you say, it's better to lose a little power than have the whole thing go up in smoke!

[JamesH]

I've been looking thought all the catalogs and the best price seems to be Rally Design (again). They do the fitting kit for xflow,with thermostat sandwich plate for £53+vat, the rad itself would be 115mm 10 row at 30.60 +vat.

Is 10 row x 115 mm sufficient for our 1300 Xflows?

Second question - how do I measure oil temp without having any lines on which to mount a sensor?

Can I use a IR probe on, for example the outside of the sump to give me a approximate reading? Or is that just too approximate?

James

[JamesH]

Originally Posted by Locost47

I've now realised who JamesH is (i'm a bit slow) and so i'm already aware of his problem!

Hi Rob!

Which problem?? There are so many! Good races at Lydden btw, got my first MSN mention (in a bad, crashing sort of way).

James

[greenamex2]

Originally Posted by JamesH

Second question - how do I measure oil temp without having any lines on which to mount a sensor?

Can I use a IR probe on, for example the outside of the sump to give me a approximate reading? Or is that just too approximate?

James

Usually fit a weld a threaded boss to the sump and fit the sensor there.

Some sensors also happen to have the same thread as a sump plug, one instant boss!

[phoenix]

Originally Posted by JamesH

Second question - how do I measure oil temp without having any lines on which to mount a sensor?

First choice is a tee-piece. If you have an oil pressure gauge, remove the sensor and put in a tee piece with two outlets, one for the pressure gauge and one for the temperature gauge.

But better than that, if you get a sandwich plate to plumb in the oil cooler you can order it with a tapped (threaded) hole to take your temperature sender.

Please don't fit a sender to the sump - sorry Denis - because that will not give you the maximum oil temperature, which is what it is important to monitor.

[greenamex2]

Originally Posted by phoenix

Please don't fit a sender to the sump - sorry Denis - because that will not give you the maximum oil temperature, which is what it is important to monitor.

As I said before, better than no sensor at all.

[Al Weyman]

James, if every bhp counts in your championship (what one does'nt it) I would think twice about putting in a higher capacity pump as it will definitely rob HP from the little you have already. On my small block chevies one tweak is to put a big block chevy oil pump in place of the original but most engine builders renounce this as an unneccessay horse power robber and we are talking big V8s here so a little 4 banger I would have thought even more relevant.

[phoenix]

Originally Posted by Al Weyman

James, if every bhp counts in your championship (what one does'nt it) I would think twice about putting in a higher capacity pump as it will definitely rob HP from the little you have already.

That's true of course, but to finish first, first you must finish and if the engine needs the flow, what else can you do? Maybe the Chevy pump is adequate anyway, whereas the X-flow pump is marginal - just about copes with standard requirements.

[Al Weyman]

The point is does it need the flow and pressure though or is it just to see that higher pressure on the guage as a comfort factor. One of my chevy engines runs at 40 psi hot but is a perfect and very powerful professionally built unit and after consulting the builder he told me thats fine as he had built it to greater clearances as long as no surge. My other (home built) runs about 75 psi. and was just built on standard sized journals and bearings, Rover V8 engines are a classic example and will run OK with as little as 20psi.

Bear in mind when this engine (crossflow) was fitted in an old Mk 2 Cortina all that would have had to indicate oil pressure drop was a dashboard light that came on at 4psi so it may have done many thousands of miles at around 20 or 30 psi with no problem but as the driver would be unaware and therefore unconcerned. As long as James's engine is not suffering low pressure as a result of surge during braking and cornering or accellerating then thats the real concern not the steady state pressure.

[phoenix]

Well, you might be right, but for competition most X-flow users will use a 25 psi warning light switch (as supplied by Burton and others). With this fitted, if the warning light comes on at idle, that's fine, but it should go off with just a few more revs and never come on under load. I was told that 25 psi under load is about minimum safe pressure - any less and you are looking for trouble with these engines - so I would not be happy with 20 psi hot under load, which is what James is experiencing.

It should be noted that for a BDA, which uses the same bottom end as a crossflow, Cosworth insist on 70 psi as a minimum oil pressure, rising to 80-90 psi in normal running. Absolute maximum oil temp they specify as 100 degrees C.

[Al Weyman]

BDA may be a different fish as it has to pump copious amounts of oil up to the overhead cams I would ahve thought. Those high pressure lights can be a pain in the butt as it happens and can give confusing signals, I have one but also an accusump (another idea for James) but I know Rover drivers for example that have ditched them. The only thing I noticed in the original post was the comment 'shallow sump' could there be a surge problem here?

PS I have raced the Cross Flow kent unit in the past in hotrods but we used a drysump system with an external adjustable pump, is this not an option here?

[phoenix]

Originally Posted by Al Weyman

BDA may be a different fish as it has to pump copious amounts of oil up to the overhead cams I would ahve thought.

That's a flow issue, not a pressure issue. Dry sumping is an option - but maybe an expense that is not necessary.

[Al Weyman]

May be money well spent though especially if an oil cooler, take off plate etc is already being contemplated, I know what i would do.