Torque specification for the inverter wires bolts on the 2012 Prius C? [and brake lines]

They do have universal charts for torque based on bolt & thread size... I suspect there's probably a website that will give you that info. Main emphasis with torque being the tightness for optimum strength, though there are other purposes for moving parts.

 

Do you mean that it doesn't exist in the Prius c repair manual, or that for some reason you thought you should not look there?

Please don't assume these are the same: this is from my 2010 (not a c) repair manual. But it should show you what you are likely to see in the c repair manual (more info) if you turn to where inverter removal/installation is covered.

Those should also be easy to find in the manual.

Right, the universal charts are usually for a few certain types of bolts/nuts graded for structural use. For a specific use like electrical terminals (as here), the fasteners might be made of different metals or alloys that the universal charts don't cover, and the specified torque might be chosen for some reason other than maximizing the joining force. For example, in some applications (with cup washers, say), you definitely don't want the torque that maximizes the joining force.

In general, you would want to resort to a universal chart only when you really do find that there is not a specific torque specified in the repair manual.

 

One answer: in the wiki page that Elektroingenieur compiled, there are numerous options covered for getting access to the manual, and some of them are free in some areas.

Another answer: maybe you are someone who philosophically believes you should never look anywhere but free sources even when you know what source contains the information you need. I can even sympathize with that, but then it is more upfront to not post "seems like such information does not exist", but rather something like "I have chosen not to look where the information I need is, because that would conflict with a personal philosophy, so I would like someone else to look it up for me."

 

Yes it is free information... Just as every bolt has a size and thread type, it also has a standard torque number where its holding strength is at its best. This is most common in bridge and other engineering design processes... I've seen the chart before in a repair manual back before we had the internet. I'm sure if you search you'll find it online.

 

An important point, made earlier, is that the "standard torque number" derived from holding strength is published for certain classes of fastener made of certain alloys, and is reasonable to use when those fasteners are being used for mechanical joining purposes (such as in building a bridge).

But there are lots of other applications of threaded fasteners, such as here for making current-carrying electrical connections, and for those applications the manufacturer may have chosen some different type of metal or alloy more suited to the purpose, or may have built the connection in a way that requires a different torque spec. (Connections with cupped washers, for example, made to keep a steady clamping force across expansion and contraction, can't be overtorqued, or the washers get flattened.)

That's why it's important to first look in the manufacturer's specs (here meaning the repair manual) to see if there is a torque the manufacturer specified for that fastener in that application. Only if there is not, and it's a standard graded fastener in a mechanical joining application, then you can resort to the generic torque-by-size-and-grade chart.

 

Torque on electrical connectors do exist, but only on some of them... So I wouldn't spend too much time worrying about it. Torque on engine parts is one thing, but not so much on others parts especially screws that hold down electrical connections.

 

On the other hand, #3 showed that there is an explicit torque called out for each electrical connection on the inverter for a 2010 Gen 3 in the repair manual, and there is very little reason to think that there are not such torques specified in the Prius c repair manual.

In my experience, the repair manuals do most commonly give specified torques for everything. There is a generic torque chart by size and grade in the front portion of the manual, but there are very few fasteners anywhere on a Toyota where it would be used because an explicit torque isn't given for the specific fastener.

 

Maybe you mean inch-pounds, because that much in foot pounds would be way too tight?

 

No, that would be twelve times too tight.

The image shows the torque values—for a different car, as @ChapmanF pointed out—in newton meters (abbreviated N · m) and inch-pounds (abbreviated in.-lb. or in.-lbf.), twelve inch-pounds to the foot-pound.

Toyota’s Repair Manual for 2012 Prius c cars (RM19C0U) says the torque for the high-voltage connectors (that is, those for the No. 2 engine wire, motor cables for MG1 and MG2, and frame wire) on the inverter with converter assembly should be:

• 9.2 N · m (81 in.-lbf.) for the two bolts that hold each connector in place, and
• 8.0 N · m (71 in.-lbf.) for the two or three bolts that make the electrical connections.

 

I suppose you could use crowfoot flare wrenches on a regular torque wrench if you had an adaptation factor for the longer arm. (Hmm, maybe offset the crowfoot by 90°?)

To be honest I haven't ever run into a brake fitting that was so sensitive that (with experience anyway) you would not be able to do by hand.