I have a question regarding tachometers. From my understanding, I need a tachometer to properly tune different aspects of my car such as timing. To use a timing light, I need to be sure I'm idling at roughly 950rpm which means I need a tachometer, right?
If so, I'm looking for advice on which kind to buy. I would like one on the cheaper end of the spectrum. What are their price ranges and what should I be looking for in a tachometer ? Thanks.
That's kind of like asking for a recommendation on underwear. Engine diagnositc tools are very personal depending on your use -- and more importantly, your possible future use.
I've seen hand-held inductive units that just clamp onto a spark plug wire for under $40 and laser units for under $70. On the other hand, it's easy to drop >$500, though the more expensive tools often have multiple features.
If JUST rpm is required, an inexpensive clamp-on is fine. Lasers usual work on the principle of applying a piece of reflective material on a rotating part (usually the crankshaft pulley) and then aiming the instrument beam at it. There are also mechanic units that use a rubber tipped probe to drive the counter. These require you to physically contact the moving part and thus require both clearance and for you to be very close to high-speed moving parts like fans & belts.
However, multi-function diagnositic instruments combine several features for both economy and added capabilities. I've seen an OTC unit for less than $175 (The Tool Warehouse) that, besides tach, includes dwell, temp probe, duty cycle (how long somthing is on like fuel injector switch) and all the usual volt-ohm type functions.
The only recommendation I make is get an inductive or optical unit so you don't have to tap high-tension leads. Contact units should only be considered on diesels, and that as a last resort. Spend some time with the Bentley to determine what you think you are capable of and may expand into doing. It may be cheaper in the long run to get a multi-task unit now.
I recently did a coolant flush and the resultant process of several rinses as described in the TIPS forum under "Clearing the muddy waters . . .". I got to play with my Raytek laser temperature gauge (Jan 22, 2005 post). Knowing when the engine is up to temperatures, or sufficiently cooled for draining and refill is difficult. The laser temp gauge was fantastic. I could scan the radiator at the inlet side and as soon as the thermostat opened, the temps would shoot up. This also let me test the thermostat operations. I could even scan the return side to see how much it was cooling before return to the engine. Thus I could easily time the amount of 'run' during the flush and rinses. I could also scan the coolant connections at the cylinder head to see when I had dropped sufficiently at the engine for a drain. And again before refilling with cold water. While playing the rinse game, I scanned my heaters' outputs to see if they were getting good flow.
The amount of time saved in just this one operation paid for the gauge, at least in the imaginary wage I pay myself for my own work.