Adding Gauges

Ohmess

Ohmess

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So, I would like some input from the tribe about gauges.

I've acquired a VDO oil pressure sensor that contains a pickup for the gauge and a connection to retain the idiot light. I am planning to install this on the head in lieu of the existing idiot light sender.

I also have a VDO oil temp sender, and I was thinking about installing it into the housing that attaches to the block and holds the oil filter and canister. In order to do this, I would need to remove the housing from the block, and then drill and tap the hole. Given that I have all the vacuum hoses and radiator hoses disconnected, this would best be done now. Whilst planning to pull this baby off, I was wondering if there an upward oriented filter canister that fits the M30b30? My son's e34 has an upward oriented canister, and changing the filter without making a mess is easy.

Lastly, I have read that the stock water temperature gauge provides slow feedback on engine operating temperature. Do people install aftermarket temp gauges because of this? Could an aftermarket VDO sender fix this using the stock gauge?
 
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That oil can came way after our cars, best to get a top bolt filter housing. Still tight but put a zip lock bag around it, unclip Alt plug if you still have one, and pull upwards pushing PS hose out of way. No mess.
 
Or a spin on adapter

HB Chris said:
That oil can came way after our cars, best to get a top bolt filter housing. Still tight but put a zip lock bag around it, unclip Alt plug if you still have one, and pull upwards pushing PS hose out of way. No mess.
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Y'all are amazing. Even answered questions I hadn't thought to ask.

DeQuincy - thanks for the references; I had seen other threads of yours, but had not located those. In particular, the location of the oil temp sender you illustrate is precisely the location I plan to use, and I had not yet determined where to go through the firewall. Most helpful. I may not add a second coolant temp sender, in part because I anticipate oil temperature and coolant temperature to move in tandem, and in part because I am thinking about installing an air-fuel ratio gauge as my fourth gauge (oil pressure, oil temp, voltage and air-fuel).

I am planning for through firewall wiring to enable the gauges, to allow for a cut-off for the electric fuel pump, and to relocate my battery to the trunk.

Stevehose -- I have the double sender for oil pressure installed (but not wired) now, and it fits with the Weber DGAV intakes. I will file away your suggestion in case I encounter clearance issues when I change to the DCOEs.
 
Ohmess said:
I have read that the stock water temperature gauge provides slow feedback on engine operating temperature. Do people install aftermarket temp gauges because of this? Could an aftermarket VDO sender fix this using the stock gauge?
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I think we have debunked the theory that the stock temperature gauge is slow. However, to answer Ohmess' question: I wouldn't recommend trying to combine an aftermarket sender with a stock gauge. In general, gauges and senders need to be paired; their electrical characteristics need to be matched. Some random combination might work, and might be accurate, but a lot of luck would be needed.
 
As far as oil temp goes VDO use to make a drain plug that was an oil temp sending unit , I used them in my M30 race motors .
 
jmackro said:
I think we have debunked the theory that the stock temperature gauge is slow. However, to answer Ohmess' question: I wouldn't recommend trying to combine an aftermarket sender with a stock gauge. In general, gauges and senders need to be paired; their electrical characteristics need to be matched. Some random combination might work, and might be accurate, but a lot of luck would be needed.
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In general I agree, but in this case, the temp gauge and sender originally installed in my car was manufactured by VDO. Thus, I would merely be installing a newer VDO sender in place of the original one, and running it to a VDO gauge. That said, I am unsure whether the electrical characteristics of the senders may have changed over time.

I did not have any particular trouble with the stock sender, so maybe I should scrap this idea and leave well enough alone.
 
Ohmess said:
That said, I am unsure whether the electrical characteristics of the senders may have changed over time.
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Right. Kind of like wondering if the exhaust system from a 2015 6 Series would fit a 1972 3.0CS, since both were made by BMW. It might, but if it did, there'd be a lot of luck involved.
 
Not exactly. There are a lot more variables in exhaust system design - efficient removal of exhaust gases, heat dissipation, noise cancellation and vibration management to name a few.

The temp gauge circuit is pretty simple. The gauge displays the voltage of the current flowing through the sensor to the engine block. When cold, temp sensors exhibit high resistance and little current flows through to the gauge, so the needle doesn't move much. As the sensor warms up, its resistance decreases, more current flows past it and the gauge moves up to reflect the increase in voltage in the circuit. Once the tstat opens the cooling system keeps the engine at a relatively stable operating temperature, and the resistance in the sensor stabilizes at a level that enables a voltage flow that puts the needle on the gauge in the middle of the display range.

The only thing we need to know is whether the resistance of the old and new sensor decreases in response to heat in the same manner and it is not hard to measure this with a multimeter.
 
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