Wattage/current-draw of car components - Advice please
Discussion
I'm building a new fuse & relay board for our 205GTI race car along with new looms (we have had more DNFs due to electrical issues than any other reason 
) Although I'll build in a 'safety' allowance, I don't want to use unnecessarily heavy wiring. Wiring for the bulbs is fairly obvious; the wattage is stated. Where I would appreciate some advice is for some of the other components.
In no particular order; The starter solenoid (I have seen widely differing figures on the interweb). The wiper motor (I have a relay for each of the two speeds). The fuel pumps (both the low pressure from the tank and high pressure for the injection). The car is fitted with a single OEM engine fan, I think this might be the highest current draw of those I have mentioned.
I don't expect anyone to know the actual figures for our car, but ballpark for a 1980s car would be ver useful.
TiA
) Although I'll build in a 'safety' allowance, I don't want to use unnecessarily heavy wiring. Wiring for the bulbs is fairly obvious; the wattage is stated. Where I would appreciate some advice is for some of the other components.In no particular order; The starter solenoid (I have seen widely differing figures on the interweb). The wiper motor (I have a relay for each of the two speeds). The fuel pumps (both the low pressure from the tank and high pressure for the injection). The car is fitted with a single OEM engine fan, I think this might be the highest current draw of those I have mentioned.
I don't expect anyone to know the actual figures for our car, but ballpark for a 1980s car would be ver useful.
TiA
https://www.autogenius.info/peugeot-205-1986-1998-...
Easiest just to run on the basis of the OEM Fuse ratings if you've not changed too much around?
Most parts should have a wattage listed that can be used to back-calculate if you scour for datasheets - Or derive based on the size of fittings (E.g. giant spade connector with 3AWG Crimp fitting...)
Don't forget to account for the length of run too!
Could also measure in-situ with a clamp meter - see what current draw looks like as you toggle the load.
Easiest just to run on the basis of the OEM Fuse ratings if you've not changed too much around?
Most parts should have a wattage listed that can be used to back-calculate if you scour for datasheets - Or derive based on the size of fittings (E.g. giant spade connector with 3AWG Crimp fitting...)
Don't forget to account for the length of run too!
Could also measure in-situ with a clamp meter - see what current draw looks like as you toggle the load.
Thank you for your reply. I agree a clamp would be the best method but I don't have one. I do have some numbers that I have tried to deduce using a combination of the methods you have suggested, but I'm not comfortable they are correct - I was reluctant to post them as I didn't want to 'lead the witness' as they say 
As an example, the OEM fuse for the fuel pump is 15A - but that doesn't change between the carburetted version of the car with one pump and the GTI with two pumps...
I was hoping peeps could offer me typical values that I can sanity check my own against.
As an example, the OEM fuse for the fuel pump is 15A - but that doesn't change between the carburetted version of the car with one pump and the GTI with two pumps...I was hoping peeps could offer me typical values that I can sanity check my own against.
ArthurH said:
I'm building a new fuse & relay board for our 205GTI race car along with new looms (we have had more DNFs due to electrical issues than any other reason ) Although I'll build in a 'safety' allowance, I don't want to use unnecessarily heavy wiring. Wiring for the bulbs is fairly obvious; the wattage is stated. Where I would appreciate some advice is for some of the other components.
In no particular order; The starter solenoid (I have seen widely differing figures on the interweb). The wiper motor (I have a relay for each of the two speeds). The fuel pumps (both the low pressure from the tank and high pressure for the injection). The car is fitted with a single OEM engine fan, I think this might be the highest current draw of those I have mentioned.
I don't expect anyone to know the actual figures for our car, but ballpark for a 1980s car would be ver useful.
TiA
thicker cables for just those components won't add a lot of weight really.) Although I'll build in a 'safety' allowance, I don't want to use unnecessarily heavy wiring. Wiring for the bulbs is fairly obvious; the wattage is stated. Where I would appreciate some advice is for some of the other components.In no particular order; The starter solenoid (I have seen widely differing figures on the interweb). The wiper motor (I have a relay for each of the two speeds). The fuel pumps (both the low pressure from the tank and high pressure for the injection). The car is fitted with a single OEM engine fan, I think this might be the highest current draw of those I have mentioned.
I don't expect anyone to know the actual figures for our car, but ballpark for a 1980s car would be ver useful.
TiA
starter solenoid / wiper motor would both be happy with 2mm.
fuel pumps are likely in the rear and some pumps may take up to 20amps (particularly if turbo e.g. Bosch 044) and also the voltage drop due to cable length could be a factor so use 3-4mm.
engine fan is probably the greatest current, maybe 25amps so use 4mm for that.
if you are using commonly available connectors it's wise to parallel connect some of the pins to accommodate the high currents like the fan circuit and instead of a single 4mm cable use 2 parallel runs of 2mm or even 4 x 1mm twisted together to make easier connection to more than 1 pin in the connector. there's also a much greater range of colours for thinner cables.
Edited by Tye Green on Saturday 2nd November 08:51
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