Rv8 oil pressure using mechanical gauge

[ClassiChimi]

Going by the gauge in my Tvr Chimaera 450 I'm regularly getting oil pressure readings of as low as 5-10 psi on tickover when engines fully upto temperatures and about 25-30 psi at 3000 revs!
I've replaced the oil sender,, ( twice) and these readings have been constant for over 3 years
Having had an engine re fresh this has always annoyed me and so I eventually got around to using a mechanical gauge ( Clarks) to see what's going on. Dom at Powers always assured me things were fine but it's a constant wonder!

So this is my findings

Car on jacks so like sitting up hill,,, a steep hill!

Engine probably 30-50 degrees as I'd ran the engine for 30 mins only two hours before

Intitail start up shows 25-28 psi at 750 revs ( Mbe tickover )





Revs rising to 2000 revs





Then as the engine temp rises you see the oil pressure slowly dropping to around 15 psi when fans kicking in at tickover






And again as fans kicking in at 1800 revs






Thoughts gentlemen please

Sitting here now I've decided I'm still not convinced so I've cable tied the gauge pipe up safe and I'm going to drive the car,, see what readings that shows.

I'll post up a few picks of the gauge fitted to the car so others can see what they need to do

[Boosted LS1]

It's normal. You should see the idle pressure on a turbocharged engine. Mine was about 5 psi max. In the end I used Kendall 20/50 and a much stiffer relief valve spring. My oil pressure was very closely matched to the revs after that but still very low at idle. There's plenty of volume being pushed through the engine despite the low pressure reading.

[Argent]

Exactly the reading I get on my 500 Griff from the TVR gauge, 15psi idle hot and 45psi @2500rpm hot.

A

Edited by Argent on Wednesday 7th September 12:56

[caduceus]

The RV8 is well known to run on particularly low oil pressure. You could check the pressure relief valve in the timing gear cover, or just replace if you're worried about it. Maybe renew the oil pump main gear.

[andy43]

A low idle speed can make a difference when the oil is hot - try raising it from 750 to 900 as it might up the pressure a touch.
Mine's the same (not tried a proper gauge) - hot and idling it's certainly below 20psi.

[ClassiChimi]

Thanks for the responses chaps

So just had a drive around, fans kicking in and out and then car sat idling for a few minutes,, very hot and again fans kicking in/out

Tickover





3000 revs






Just connected up my original sender and hot it's showing 15 psi on tickover so actually fairly accurate, above 3000 revs it's still stays at 30 psi but at least I have some reference points


A couple of pics with mechanical gauge attached so I could drive the car.















I did notice the pressure rise a good 3- 5psi by bringing up the revs to 850-900 revs so I'll adjust my tickover up a tad

I also noticed how the pressure rises and falls in line with engine revs so I'm now happy the pressure isn't falling to low,, although it does on occasion go as low as 12 psi so lower than I'd anticipated but the engine sounds and feels well lubricated so I'm glad I've done this test now

ETA oil pump gears replaced as part of engine re build 18,000 miles and 3 odd years ago.

Edited by ClassiChimi on Wednesday 7th September 14:48

[carsy]

I have my idle at 1000rpm for this very reason. It also helps to keep the water flowing a bit better as well.

[QBee]

Peter has a Spa gauge in his car - ask him how his reads.

[chris52]

I had the same issue gauge in car reading very low. Griff 500 Supercharged 60k bottom end refresh 8k miles ago. Using the same gauge as you (Machinemart one) I had the following readings.

Cold idle 58psi
Cold 3k rpm 60psi

Hot idle 22psi
Hot 3k rpm 55psi

The hot idle was just letting the idle until the fans kicked in a few times so may not have been up to full oil temp.So I guess the hot figure may drop a bit. Oil is Millers 10 60. Happy with these results as should you with yours as they seem good to me.
Chris

[SILICONEKID345HP]

Mine read low ,pressure relief spring was jammed , I had to have new big end shells .

[ChimpOnGas]

These are my figures running Penrite HPR15 15w60.

Cold idle 60psi
Hot idle 45psi

Cold at anything over 2,000 rpm 62psi
Hot at anything over 2,000 rpm 60psi

The only difference from standard is V8 Developments uprated the oil pressure relief spring six years ago when they fitted my Stealth cam, new followers and JP roller timing chain/set.

The first thing that happened was the additional oil pressure blew the diaphragm inside my oil pressure sender , but once I replaced the sender the gauge showed the above figures and always has.

I did test these pressures a few years back with a Sykes Pickavant mechanical gauge, but just got the same above readings as I see on my TVR gauge... so I'm happy they're right.

[ClassiChimi]

I also had a seized pressure relief valve, Produced to much pressure and blew a number of gaskets, oil leaks galore, which is why I had an engine re fresh, new big end and main Shells incl crank grind to 10 thou.

Even when hot I'm seeing 25+ at anything over 1200 revs so pretty happy with that

[N7GTX]

Boosted LS1 said:

It's normal. You should see the idle pressure on a turbocharged engine. Mine was about 5 psi max. In the end I used Kendall 20/50 and a much stiffer relief valve spring. My oil pressure was very closely matched to the revs after that but still very low at idle. There's plenty of volume being pushed through the engine despite the low pressure reading.

Cold idle: 55-60 psi
Cold 3,000 rpm: 60 psi

Hot idle: 35-40 psi
Hot 3,000 rpm: 50-55 psi

Idle is set at 1,000 rpm. Oil is Shell Helix H7 10w/40 semi synthetic. 2,500 miles since engine rebuild with the turbo.

[ChimpOnGas]

N7GTX said:

Cold idle: 55-60 psi
Cold 3,000 rpm: 60 psi

Hot idle: 35-40 psi
Hot 3,000 rpm: 50-55 psi

Idle is set at 1,000 rpm. Oil is Shell Helix H7 10w/40 semi synthetic. 2,500 miles since engine rebuild with the turbo.

Very similar to mine then Iain, very similar indeed, did you uprate your OP relief spring? I should have also said in my previous post my Canems closed loop idle target is set at 950 rpm which it holds very effectively indeed and personally I just don't see any benefit in a lower idle. I want my water pump turning fast enough to do something and plenty of oil splashing on my cam lobes, I also feel more comfortable seeing my 45 psi hot idle oil pressure.

Can someone explain the benefits of a 750rpm idle other than to show it can be done and perhaps achieve a fractionally quieter idle? Just to be 100% clear here in "PH forum land" I'm asking a genuine question here not having a dig at anyone... especially Alun who is a super nice guy in my book.

I just don't get the whole the 750rpm thing , personally 950rpm is as low as I'm prepared go on my old Rv8

[Boosted LS1]

N7GTX said:

Boosted LS1 said:

It's normal. You should see the idle pressure on a turbocharged engine. Mine was about 5 psi max. In the end I used Kendall 20/50 and a much stiffer relief valve spring. My oil pressure was very closely matched to the revs after that but still very low at idle. There's plenty of volume being pushed through the engine despite the low pressure reading.

Cold idle: 55-60 psi
Cold 3,000 rpm: 60 psi

Hot idle: 35-40 psi
Hot 3,000 rpm: 50-55 psi

Idle is set at 1,000 rpm. Oil is Shell Helix H7 10w/40 semi synthetic. 2,500 miles since engine rebuild with the turbo.

Yes, I've done that to but one winter morning (cold) I gave the engine a blip and burst the oil cooler. To much pressure isn't needed. I ended up with idle matching the revs or close to it with the mods I'd done. Tickover was about 750 rpm iirc. I eventually used Halfords 20/50 in the end because it was cheap and readily available. My Gp A big wing sump held a huge amount and the Amsoil or Kendal packs were flipping expensive.

[N7GTX]

I've never been one for low idle speeds. My last SD1 was too low and the oil pressure was around 7 psi hot. Quick tweak to 900 rpm and it went to over 10 so that made me happy.

The spring is standard so far as I know, only Dom will know this unless I search out the invoice .

[Boosted LS1]

I think at one stage I even had a spacer on the spring during my experiments. I also had one of those real steel longer gear sets. What a load of faffing about, back in the day :-)

[ClassiChimi]

I raised mine upto 900 revs and now I'm used to 750 it seems ridiculously high, do Range Rovers run such a high tickover?

I've always been led to believe it's more a case of rough running at low revs because of a combination of higher lift cam and the CUX,

What car runs a tickover of 900 odd revs, mine happily sits at 750 revs and there's clearly enough oil circulating to not need to spin the engine over needlessly, the cam doesn't get splashed much below 1000 1500 revs so that's not an issue either, I always have the option of raising the revs with my right foot if I'm in traffic and want to get some oil pressure or splash.

If by running at 750 revs your water pumps not shifting much water then I'd expect my fans to kick in at slow speeds more often, they don't kick in hardly at all!

the tickover set at 750 means you can go around a roundabout in 3rd gear 1000 revs with no shunting, tickover higher the cars pushing on and shunting results unless you use the clutch which I try to avoid.

Dom wants Jay to get em down to 750 revs, just to prove he can I reckon but driving the car is way better so there is a reason for it as far as I'm concerned

[ClassiChimi]

Just to make my point even more desirable with the tickover set slightly lower than the 900 recommended revs for these cars on the Lucus CUX system it takes about 30% less effort to drive the car,,, I used to have to dip the clutch to control slight shunting at 1100 revs which is exactly the revs required for slow 3rd gear roundabouts when taking it easy so I was always on the clutch, now I don't need to do that and can just shut off until the desired speed is attained then potter through the obstacle and just gently squeeze the throttle on exit and I've proven I can go as low as 700 revs and still it won't shunt. Just pull away with loads of Torque.
This simple ability of the Mbe or any good after market Ecu management has transformed my Tvr, it's a pussy cat around town now and so much easier to manage the car

I avoid going lower than 1000 revs as a rule and seeing my tickover oil pressure on a mechanical gauge going as low as 12 psi on tickover makes me want to avoid such low revs but an important thing I leaned today watching the gauge as I drove the car,
Only if I dip the clutch or come to a hault does the oil pressure actually drop to around 15 psi
I noticed that even in 4th or 5 th gear at 12-1400 revs the oil pressure seemed to maintain itself at about 24-28 psi so I then pottered around my local streets watching the gauge, the moment you accelerate the oil pressure shoots up to well past 40 psi then as you settle the revs the gauge does the same,

My conclusion is my oil pressure only ever drops to 15 psi if the engines at idle for more than say 5 seconds, when driving and keeping the drive train engaged it maintains a higher level by around 10-15 psi regardless of lower revs,,

As Boosted and others point out the oil pressure is directly related to engine revs and with mine the Moment you raise the revs above 1200 the oil pressure jumps to around 30 psi and onwards as you Rev higher upto about 45psi from 2000 revs on,,,

I'm now confident that at slow speeds as long as I'm not on tickover for very long the oil pressure maintains a good level for the conditions and is actually around 20-25 psi even driving like my Nanna

[ClassiChimi]

Boosted LS1 said:

It's normal. You should see the idle pressure on a turbocharged engine. Mine was about 5 psi max. In the end I used Kendall 20/50 and a much stiffer relief valve spring. My oil pressure was very closely matched to the revs after that but still very low at idle. There's plenty of volume being pushed through the engine despite the low pressure reading.

that's my thoughts too, hey I must be getting better at this diagnostics lark

Now here's a weird one for you guys ,,, mechanical gauge so no electric involved,,, yet when fans kick in pressure drops a good 2-4 psi???
I didn't imagine it either it doesn't seem possible, the revs drop very slightly when the fans go on but not by much,, that must be the reason though !