Ana Roadster

Yugen said:

A fellow Garage Vary fan! I like!

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That's very kind of you to say, thank you


I have made a start on the first issue in my list, a bit of back story first:
Since fitting a VVT engine and the uprated fuel pump, the car has been driving fine (at least for an untuned car..). However on my maiden voyage home from the paint shop, the car cut out mid drive. After a few days of soul searching and running round the car with a multi-meter, I discovered that the issue was simply that my main relay had stopped working correctly. I rigged up a 12v power source to it on a bench, and whilst it still actuated, it was clear there was no current passing through it at all.

After I dug a bit deeper, it seemed that a common fault after upgrading things like the fuel pump and ignition system, is for the relay to go due to the amount of extra current being continuously drawn, the relay heats up and plastic starts to melt which could be seen very clearly on the legs of the connector in the fuse box.

This is where things start to get tricky, I opened the relay and the contacts looked OK, I guess the metal must have become non-conductive in some way, maybe the heat has caused it to tarnish a bit. I bent the contacts further up so when it actuates, it does so in a different place and it works again.
So I then replaced the relay with an OEM one from a breaker, took the car for a 30 minute drive and damn, she hot!

After a bit more reading I found that flyin' miata sell the 80a RX-7 main relay (JE16-18-811) listed as an upgrade for people with uprated fuel pumps etc. So on the phone to Mazda and £70 later, an RX-7 relay is being sent to my local dealer. Roll on a week later and it's fitted (no modifications required) but it does still get hot when driven. I've asked around and I can't find any technical data to work on as to how hot it normally gets before it's considered out of spec.

So what do I want to know/achieve:

1. What is rated amperage of the OEM NA main relay (B6S8-18-811)? I ask this because the main fuse in my fuse box is 60a, though I understand the OEM one is rated to 80a which is the rated limit of the RX-7 relay. Why would a fuse allow more current than the components allow from stock?
2. How hot does the NA main relay get when used in my set up?
3. How hot does the RX-7 relay get when used in my set up?
4. Does moving the fuel pump to it's own relay lower the temperature of the main relay? If so why or why not?

I have bought an infrared thermometer so that I can test the differences between the two relays in my set up.
I would be very keen to know others observations.

guitaristanime said:

1. How hot does the NA main relay get when used in my set up?
2. How hot does the RX-7 relay get when used in my set up?
3. Does moving the fuel pump to it's own relay lower the temperature of the main relay? If so why or why not?

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Relay current ratings aren't really to do with continues use capacity its more related to switching capacity. You shouldn't really see any temperature increase due to a larger current draw unless you are well outside of its rating. The bigger issue is that if for example you try and pull 100A at 12V through a 60A relay it may draw an arc internally across the contacts as there won't be enough air gap to instantly break the connection. This creates a huge amount of heat and will damage the contacts very quickly causing the relay to fail (either through the contacts melting or the plastic). This is one of the reasons the relays are often rated for much higher AC loads than DC as is AC is far easier to switch.

Relays will get hot/warm in use but this is to do with the coil that holds the contacts open or closed. Moving the fuel pump to a separate relay is a good idea and I would always recommend this if you have seriously upgraded your fuel pump (very large or multiple in tank or external pump) as it means you can run larger feed wires but I doubt it will have much affect on the temperature of your main relay and with a walbro255 pump its probably not necessary.

Its also worth noting that fuel pumps are electric motors and motors are an inductive load meaning they normally draw a huge amount of current at the moment they are switched on and then drop down to there running levels. This is very aggressive on relay contacts over time so if you do switch the fuel pump to its own relay be sure to spec the relay correctly; some suppliers/manufacturers will list a different inductive load rating in the relay data sheet.

thanks,
Nix.

Nix. said:

Relay current ratings aren't really to do with continues use capacity its more related to switching capacity. You shouldn't really see any temperature increase due to a larger current draw unless you are well outside of its rating. The bigger issue is that if for example you try and pull 100A at 12V through a 60A relay it may draw an arc internally across the contacts as there won't be enough air gap to instantly break the connection. This creates a huge amount of heat and will damage the contacts very quickly causing the relay to fail (either through the contacts melting or the plastic). This is one of the reasons the relays are often rated for much higher AC loads than DC as is AC is far easier to switch.

Relays will get hot/warm in use but this is to do with the coil that holds the contacts open or closed. Moving the fuel pump to a separate relay is a good idea and I would always recommend this if you have seriously upgraded your fuel pump (very large or multiple in tank or external pump) as it means you can run larger feed wires but I doubt it will have much affect on the temperature of your main relay and with a walbro255 pump its probably not necessary.

Its also worth noting that fuel pumps are electric motors and motors are an inductive load meaning they normally draw a huge amount of current at the moment they are switched on and then drop down to there running levels. This is very aggressive on relay contacts over time so if you do switch the fuel pump to its own relay be sure to spec the relay correctly; some suppliers/manufacturers will list a different inductive load rating in the relay data sheet.

thanks,
Nix.

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This is incredibly helpful and so informative, thank you.

Do you have any insight into what a normal temperature of the relay would be after a spirited drive. I'm getting a bit paranoid now that there is something else causing the relay to get hotter than it should be whilst driving. For what it's worth, my car still has the 60a main fuse in, am I right in thinking that if the car was pulling any higher current than 60a across the main relay, that the main fuse would blow? or is it not that straight forward?

Moving the fuel pump to it's own relay is a minimal job with minimal cost and sounds like it's worth doing anyway for safety but I appreciate that it might not be completely necessary then based on what you've said - at some point the car will be getting ITBs (or I might even go for a turbo again depending on how I'm feeling) so future proofing that too.

MOT passed with no advisories

Its been an audio day the last two days, in between showers and extreme heat cycles.

Started by making some DIY water covers for my new cheap door speakers.



Used the lid of a blank CD spindle, for one and a haribo tub for the other. Cut both to size with a dremel and then sealed them on with some silicon.

I managed to run a remote cable under the centre console carpet, and quickly realised that I would never get any more cables down there, so routed a set of RCA cables down the drivers side into the boot.
Next, I spent the best part of an hour shouting at the drivers door as I tried to feed a new 16 gauge set of wires for a door speaker, eventually I came out on top and decided to call the wiring a day.

Next up I made up a mount for my Ground Zero Class D amp, but of marine ply I had in the garage, cut to size and a cable channel put in, finally sanded and painted:





- Left to do -

• run wire for passenger door speaker
• wire amp in to power etc
• continuity test head rest speaker wires
• choose new headrest speakers
• split rca signal from stereo into 4 channels from 2

A quick update, been too busy recently to properly document this - plus, it's nothing ground breaking really. My turbo mk2 decided to lose all brakes at 70mph on the drive back from having it's brakes sorted, simply because I made the gamble on chinesium calipers. Lesson learnt.

So back to the mk1......

• wired passenger door
• amp fully wired up

Everything seemed fine, tested the set up and suddenly I lost the left channel. Had a play with the volume and suddenly the right channel lost, and the left came back on loud. Immediately I thought that there must have been either some current issues or the amp was faulty. However after I had a little sit down and some advice, turns out the issue was likely the gain knob or the x-over switch. To test this theory I moved the input and output over to the other two channels and sure enough all was working fine.
Cleaned up the gain knob and x-over switch with some brake cleaner (yes I know it's conductive but, it does evaporate) and after 3 goes, it was finally good.







- Parts Used -

• Ground Zero GZHA Class D amp with a whopping 80w RMS x 4 channels!!
• VIBE amplifier wiring kit, consisting of a remote signal wire, chunky power and ground and RCA lead
• Pioneer TS-R1750S speakers - just budget speakers but I needed to gauge what 40w RMS was like before moving onto the headrest speakers, may revisit and upgrade to 80w RMS
• Cheapy Sony A410BT head unit, plans to upgrade this to an Android unit in future as I want to be able to utilise Android Auto, Tuner Studio and RealDash
• Amazon Basics 16 gauge speaker wire

guitaristanime said:

apologies for stealing your cars nick name!

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I doubt we are the only people using that


from https://www.japan-partner.com/check-manufacture-year.html

made in 10/1990, year older than my silver heap but younger than my feb '90 white mess

^^guessing thats one of the last with that type of wipermotor? - little tip, if you need a replacement then it's the early type as the mounting baseplate & bulkhead holes differ (might be the same as a lefthand drive car though)

guitaristanime said:

the stock cross over was just to get me home, initially the plan was always to go with ITBs but as you'll see on my thread I posted yesterday, I'm not happy with the way the car runs and really need help tuning and I want to get it right before I move on with changing any intake bits.

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ecu setup can be fun, iirc Tunerstudio has a 'test' setup so you can fiddle without killin........

think @Bilbo would know more

as to itb's, can adapt motorcycle tb's on a standard / cutdown inlet manifold for cheap, will save a few hundred £££'s over Jenveys and probably similar results?
like Bilbo's setup
or get a Jenvey manifold & adapt bike tb's to fit like I've done

guitaristanime said:

The end goal was jenvey ITBs and possibly a light skim and big cams.

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maybe better off with

QUOTE="guitaristanime, post: 4540318, member: 66569"]a skim and small cams.[/QUOTE]

Less can be more and unless you are running a low ratio diff loosing low rev torque can make driving harder and less fun🤭

Rich.