Oil Pressure Sender

[bobfather]

Have you tried 7bar. Same thing. There's normally loads of them

[bobfather]

I've just had a look, there's several to choose from

http://www.ebay.co.uk/itm/Universal-Engine-1-8-NPT...

[ChimpOnGas]

Discopotatoes said:

I'm in need of a new sender but can't see any 100 psi ones on eBay they all seem to be 150 is this going to be suitable?

Hi Rich, I'm using an Ispro R8917-03.

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

I only fitted it four months ago so it's longevity is yet to be fully tested, but I have to say I'm really happy with it so far.

Alun reported when using this sender his gauge read 15psi at rest with the engine off, so the suggestion is the sender over reads by 15psi or more with the engine running too.

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

This has not been my experience with the Ispro R8917-03, to show this I've just popped out the the garage to take some snaps.

Ignition off...




And now with ignition on (engine not running)....



See... as close to the zero mark as you're ever likely to get, and with the engine running my pressures match what I've seen on a Sykes Pickavant professional mechanical oil pressure gauge plumbed directly into the engine.

Basically (& with the V8 Developments OP spring mod) I see the following:

Cold idle: 40psi
Hot Idle: 33psi
Cold over 2,000rpm: 60psi
Hot over 2,000rpm: 55psi

I can certainly see why Alun saw the wrong readings if his gauge was reading 15psi at rest and with the engine off, but the Ispro sender certainly worked for me on my 1996 car with magnolia Caerbont gauges. Perhaps the issue for Alun related to an incompatibility between the Ispro sender his later pure white faced gauges?

The American made Ispro R8917-03 seems significantly better built than any sender I've handled before including Jag XJ6 ones and the TVR original. For a number of years I'd been using a cheap eBay sender to good effect until it started weeping a bit, saying that apart from a few oil drips it continued to work perfectly right up to the day I removed it, and that was roughly five years service for just £15 so I'm hardly complaining.

The Ispro sender is more expensive but it's definitely better built than the TVR original or the cheapo eBay sender, and it works perfectly for me, but will it last

It's heft & build quality seems to suggest it will... but only time will tell

Edited by ChimpOnGas on Tuesday 28th February 20:23

[Discopotatoes]

that looks a lot longer than the original no clearance issues then?

[ChimpOnGas]

Its all in my post here mate...

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

But to save you the pain of reading all my waffle, I've sliced out the relevant bit for you....

ChimpOnGas said:

The Ispro R8917-03 is quite a bit more expensive than the cheapy Chinese ones but still a lot cheaper than the ones sold by the TVR parts specialists. It's also quite a bit longer, I had to jack my engine slightly to get it started on the thread, once started it screwed in perfectly and there were no clearance issues whatsoever when I took the engine weight off the jack.

Dave

[Discopotatoes]

ChimpOnGas said:

Dave

[ClassicChimaera]

As Dave says on my later car with white backed gauges the Isspro sender reads about 15psi high from the time it's switched on. If you -that 15psi it reads totally spot on though,, a tad high maybe.
Another owner had the same problem as me with it reading high so it does seem something to do with our cars rather than just mine.

What's funny is Dom at Powers told me this before I tried it,,, he's done it all ain't he

My engine at 2800 revs oil pressure is around 45psi ( mechanical gauge) hot oil and today it was reading 60 psi so take of the 15 and it's accurate.
Same with idle, 30 psi but it's actually 12/15 psi in the real world.

Years ago I used an O ring on a sender ( I was a kid and thought I better put a washer on that
The oil pressure readings dropped by about 10 /12 psi I seem to remember and it returned to its proper readings when I removed thevwaher,,, lesson learnt.
i might just take it out the flow of oil by a mm and see what it does,,, I shouldn't think aloud should I.

[bobfather]

The sender output causes the gauge to read 15psi high.

The sender works by varying the resistance
240ohm = 0psi
153ohm = 25psi
102ohm = 50psi
67ohm = 75psi
33ohm = 100psi

therefore adding a 30ohm resister inline with the signal lead should correct the 15psi gauge reading error

It's not a perfect solution because the axis aren perfectly linear

Edited by bobfather on Tuesday 28th February 22:39

[ChimpOnGas]

Alun if all this really bothers you, now you spent money on the Ispro sender, why not just tune it with a variable resistor? Once you've established the Ohm figure you can simply fit a resistor of the correct fixed value.

This is what I did with my Range Rover temp sender mod, and it works perfectly; unlike when I suffered TVR's poor original sender location/arrangement my TVR temp gauge now follows what my Canems ECU software shows. So with just a glance at the gauge I now actually know what my coolant temps really are... which is nice.

The Ispro sender is a quality thing that gives accurate readings if like me you have Caerbont gauges, and for people with later cars that have the white faced gauges for not much more than a pound you too can get the benefit of a better built sender and see the right figures on your gauge.

A couple of quid on some resistors has to be better than paying £60 or more for one of the rip-off original senders that in truth are nowhere near the quality of the nice & solid American made Ispro one.

[bobfather]

I think you're kidding yourself if you think the expensive sender will be more accurate. The mechanism is the same in all these senders. Price difference may give you a better build quality but it won't give you better technology. Ultimately these sender/gauge combinations are only designed to indicate approximate values

[ChimpOnGas]

bobfather said:

I think you're kidding yourself if you think the expensive sender will be more accurate. The mechanism is the same in all these senders. Price difference may give you a better build quality but it won't give you better technology. Ultimately these sender/gauge combinations are only designed to indicate approximate values

I think you've misunderstood me Bob, I'm not saying and have never suggested the Isspro sender will be more or less accurate than any other bellows type resistor sender, assuming that is we are talking about a correctly gauge matched 0-100psi sender that is! (not the incorrectly matched 0-90psi VDO Jag XJ6 sender used by TVR)

Indeed if you read my original post on this...

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

You'll see I make this statement...

ChimpOnGas said:

My personal opinion is all these senders are flawed by design, they work by hot engine oil acting on a rubber diaphragm which in turn acts on a variable resistor. Hot acidic engine oil acting on a rubber diaphragm isn't exactly recipe for longevity so you could argue the cheapy Chinese ones are a better bet because they only cost about £12 a time.

I also said this...

ChimpOnGas said:

I can't tell you if the Isspro R8917-03 is better or will hold out longer than the five years I got from my cheapy Chinese sender but it does feel better made, only time will tell if it lasts

Having spent my formative years restoring and repairing British classics I'm more than familiar enough to confirm this type of sender is never that long lived, their accuracy is also never as good as a capillary gauge.

TVR used a VDO bellows sender, basically it's exactly the same as and interchangeable with the sender from an old Jag XJ6. Every Chimaera & Griff I've ever seen still running the original VDO sender gives the wrong reading. They all show you a figure that's roughly 10psi lower than reality when you check it against a proper mechanical gauge plumbed directly into an oil gallery. This was a pairing/compatibility issue between the sender and gauge, the original VDO senders are also rather poor quality.

The TVR Caerbont gauge operates over a 0-100psi range, the highest number shown on the gauge is 90psi but look closer and you'll see it has the two dots at both ends of it's scale indicating the areas of risk, ie if the engine is running and the needle sits within the lower two dots (0-14psi) at idle you have a dangerously low oil pressure, and a dangerously high oil pressure at speed if the needle reaches the upper two dots (90-100psi).



TVR (or more likely their gauge supplier) probably only used he old Jag XJ6 VDO sender because there were loads of cheap unused ones available from Jaguar at the time, the Jag sender and gauge are correctly paired both operating over a 0-90psi range, to reaffirm this point here's a Jag XJ6 oil pressure gauge...



As we can see it's a 0-90psi gauge not the 0-100psi gauge we have, so TVRs use of the parts bin XJ6 0-90psi sender paired with the Caerbont 0-100psi gauge was always going to give readings that are roughly 10psi lower than they really are.

It's also why my Isspro R8917-03 sender gives the correct oil pressure readings on my Caerbont 0-100psi gauge.

http://www.issprogauges.com/0-100-PSI-Oil-Pressure...

Personally I would never fit the overpriced, poor quality, and inaccurate one sold by the TVR parts specialists.

I have no idea how long my Isspro R8917-03 sender will last, and as I've already been careful to point out all these bellows resistor type senders are flawed by design. But what I can tell you is if you have Caerbont gauges this sender will give you the right readings, the separate dedicated earth terminal and the sender's overall feel of superior build quality are also significant benefits offered by the Isspro sender over the VDO original.

It's cheaper too, so if you have Caerbont gauges I call that a no-brainer

Clearly there's something different about the the later pure white faced gauged used by TVR, my guess is they finally worked out the incomparability issue with the XJ6 sender and created a gauge that was correctly paired to all those Jag senders they still had. If you do have a later car with these pure white gauges it seems highly likely you need a 0-90psi sender, unfortunately Isspro only offer senders in the three following ranges:

• 0-80psi

• 0-100psi

• 0-150psi

Actually (and remembering the two dot rule), you can clearly see the later pure white faced oil pressure gauge used by TVR is a 0-90psi gauge...



Compare this with the earlier Caerbont gauge I have where the last of the two dots clearly ends at the 100psi point, making it a 0-100psi gauge.



So all you need to do is choose your sender correctly, and you'll see the correct readings!

Edited by ChimpOnGas on Wednesday 1st March 08:32

[mjlloyd500]

had 3 senders so far latest last 5years goes up and down after 30 minutes running time.dont bother anymore engine stil has no tapping sounds around 75000 miles still pulls like a train,owned for last 13 years and 600000 miles

[ClassicChimaera]

bobfather said:

The sender output causes the gauge to read 15psi high.

The sender works by varying the resistance
240ohm = 0psi
153ohm = 25psi
102ohm = 50psi
67ohm = 75psi
33ohm = 100psi

therefore adding a 30ohm resister inline with the signal lead should correct the 15psi gauge reading error

It's not a perfect solution because the axis aren perfectly linear

Edited by bobfather on Tuesday 28th February 22:39

My youth education left a lot to be desired, I've just been studying resistors and there identification with my 11 year old grandson so I understand the reasoning here.

I will try this at some point. Thanks Bob.

[ChimpOnGas]

Alun, study my last post paying particular attention to the last two images.

It's clear to me my earlier Caerbont gauge is a 0-100psi gauge, while your later pure white faced gauge operates on the 0-90psi range.

This is why the Isspro sender works perfectly for me but gave you the wrong/higher readings.

Quite simply... you need a 0-90psi sender.

[Brithunter]

Has anyone thought of changing to a mechanical oil pressure guage?

Surely it would not be that difficult.

[phillpot]

Brithunter said:

Surely it would not be that difficult.

Only difficult bit may be getting one to match?

[bobfather]

Brithunter said:

Has anyone thought of changing to a mechanical oil pressure guage?

Surely it would not be that difficult.

There are many 'made for purpose' mechanical gauges designed for testing engine oil pressure. One of these could easily be permanently fixed somewhere in the engine bay. The dash gauge could then be used for it's intended purpose, to give an indication of pressure as in low, acceptable or high. In truth the dash gauge/diaphragm sender combination could never offer much more than this anyway, if you doubt this just have a look at the error bands declared on pressure sender documentation. If worried the actual pressure can be read from the engine mounted bourdon-tube gauge

[Discopotatoes]

Brithunter said:

Has anyone thought of changing to a mechanical oil pressure guage?

Surely it would not be that difficult.

Ive got one which I'm about to fit, it's oil pressure and oil temp I'm one gauge. It's a capillary gauge so has two hoses going down to th engine

[bobfather]

How about fitting a digital data logger where the vents are behind the gear lever. You could then get accurate readings of all engine variables and have it set to permanently display a couple.

Personally I'm happy to see that my dash gauges show the important variables to be within 'normal' values. Looking for absolute accuracy is unimportant to me, these engines happily operate within a range of values, as long as I can see evidence of deviation from the 'norms' I'm happy I can respond appropriately to any engine problems using the imprecise gauges TVR supplied

[Brithunter]

If it were me then I would be looking at a new "Vintage" Smiths 100psi guage with white face. I believe they are 52mm dia.