Shift light?

I'm swapping a 2zz/6mt into the place of a 1zz/5mt on a 03 Corolla.  The problem is the stock Corolla tach tops out at 8k, and the engine redlines at 8250. My ears can't really tell the difference between 8k and 8250, but I'd like to be able to wring every last but out of it at autocross if there isn't a corner before the 1-2 shift.  I've seen the standard flashlight sized shift lights, but I'm more drawn towards a slim sequential shift gauge, something more like this:

https://www.ebay.com/itm/124079930407

I see a couple options on eBay that look like they were built in someone's garage, which isn't a deal breaker, or name brand options that seem insanely expensive for what it does.

Does the hive mind have a preferred shift light model/style?  Something that can blend in on a DD but still do the job?

is  there  a simple chip , maybe arduino add on that would work ?

be nice to have an "idiot" light on the dash for a  shift light and not the big ones you see in street racers , 

added points if it could be a "soft"; rev limiter.....

https://www.ti.com/lit/pdf/snas555

Take a look at this. Figure 18 page 15 should get you close.

just out of curiosity, can the needle on the stock tach go beyond 8000?

RossD said:

https://www.ti.com/lit/pdf/snas555

Take a look at this. Figure 18 page 15 should get you close.

You must think I'm far more clever than I really am.  

mad_machine (Forum Supporter) said:

just out of curiosity, can the needle on the stock tach go beyond 8000?

I don't know for sure, but I don't think so.  

Years ago I tried to figure out how to make my own with an arduino type chip and never got anywhere. I realized it wasn't worth the time to learn the whole system just for a light. I wanted a low key bulb in the instrument cluster. 
 

at the time there was a universal, adjustable one available that was a little bit bigger than a sharpie marker. I never bought one but it seemed like a good compromise. Can't remember who made it now...

Can you swap in the tach if not entire instrument cluster from a Corolla XRS model in?

In reply to JesseWolfe :

From what I understand, it won't be a direct swap.  The harness and some of the senders are allegedly different between the early and late cars.  I have an early version, while the XRS was only late.  Also, an XRS cluster appears to be near unobtainium. 

An OEM cluster would be ideal, but appears to be more effort and expense than it's worth.

I generally use something like this 

https://www.ebay.com/itm/161650990862

And if i want the light in the cluster i take it apart,  add wire extension to the light bulb leqds, and place the new/extra led in the cluster/gauge hood/wherever 

I have some silly questions as I think it's possible you're whizzing up a rope with this. Bear with me on this as it maybe of use to you.

Where does the motor make peak power, what is the RPM drop between gears and what is the MPH at redline?

I will use my Datsun as an example, note all of the HP numbers are at the wheels.

It peaks 99HP at 8000 and continues to 8200. At 6500 the motor drops to 95, at 6000 it's dropped to 88 and by 5300 it's down to 78.

At 8000 RPM the 2-3 shift drops 2786rpm, 3-4 is 1902 and 4-5 is 1168. Of note is that below 6000 RPM the car starts to drop 1.4hp per 100 rpm. By revving the car an extra 200 rpm in second I gain 3hp. 8000 RPM in second is 52 mph, 8200 is 53 mph. In 3rd gear we are taking a 2 mph difference between 8000 & 8200.

 There are only a couple of reasons to hold the extra 200 rpm; it keeps the motor in the power band and  you can make fewer shifts.

On the subject of holding a gear longer; a shift time is .4-.5 but you are not stopped during that shift so it doesn't equate to a .4-.5 slower runs probably more like a tenth or two.  So the question is what's the time gap to any cars in front of you?

Also of note is that the higher the RPM, especially in lower gears, the more pitch sensitive the car becomes. What you gain in not shifting maybe lost on corner entry because the car is unsettled.

So with all that said unless there is a significant gain I'd stick to the 8K redline. I'm also not a fan of shift lights for autocross, if you do anything get a rev limiter on it as it will be past the 8200 before you notice the light.

My .02..................back to the regularly scheduled programming.

Tom - that is unusually sensible of you!

I often have that argument with people that insist that winding the nuts off their engines is the best way to go. No one ever bothers making a chart of gear ratios and works out where the most sensible rpm to shift might be.

To the OP - if you really want to shift all the time at absolute top rpm forget about a light and invest in a rev limiter - it will be a lot more reliable than you will (there is a tendency to ignore lights and such in the heat of the moment). Look at an electronic (e.g. MSD and many others) or mechanical limiter and then you'll just have to slightly anticipate it to not lose any time at all but the worst thing that will happen if you don't is a moment of ignition 'flutter' (many limiters omit every other impulse and the engine just flattens out).

I wanted a shift light in my gauge pod that kinda blended in. I bought a shift light and an AutoMeter RPM activated module. Disassembled the shift light and mounted the LED bulbs part in the dash where a clock came from the factory. I mounted the AutoMeter box and the "guts" of the shift light on the tunnel where there would be easy access to change the LED brightness for day/night and RPM pills for the module. You can see the LED part in the factory tach pod and module on the trans tunnel. Not a junkyard price project but might give you ideas.

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No factory shift light?

A lot of people HATE the factory upshift lights, but I don't understand why.  In the case of a Saturn for example, the light that suggests you shift when you are cruising around at low load and you could go up a gear, will also suggest you shift when you hit redline.  You can just take the wires from and connect them to a brighter bulb if you want.  I saw one guy connect it to a pretty bright LED inside the center vents of the car so when the light was off you would never notice anything.

I had a large one for the swift to remember to shift by 9000rpm's for safety even though the valve springs and tune allowed 9500 all day. The rest of my cars have always run out of power before time to shift ... 

@wspohn it's a combination of having road raced 125cc bikes (2000 rpm powerband) and a professional hazard (Purchasing Analyst). Also I'm cheap & lazy; a Datsun A-Series engine will go 10 seasons at 7800 RPM, 5 seasons at 8200, 6 race weekends at 8600 RPM and 6 hours at 9000 RPM.

I totally forgot about a MSD adjustable box; as pointed out you really don't have time to look at much during an autocross run.

You may have 8250 problems, but the tach ain't one.  I doubt a shift light would be set higher than 8k for reaction time vs the rate revs climb in 1st either, so additional hashes on the dial would mostly just go unused by your eyes either way. 

The much more important part is the accuracy of the tach, and your ability to be staring at it rather than where you're going.  That's really where the shift light comes into play.

I'm surprised more people haven't tried pointing LED's up at the windshield for an HUD style signal right in your line of sight.

The car is running on a factory ecu, which thankfully has a functional rev limiter.  It even adjusts based on engine temp to keep you from over revving before it's ready.

I like the idea of modifying a cheapo adjustable shift light to integrate the light subtlety into the dash somewhere.

My plan would then be to do some trial and error testing my reaction time.  I'm assuming I would need the light to trip a little early to allow me time to react.  I am hopefully consistent enough that I can find an RPM that allows me to respond to the shift light before hitting the rev limiter.

What is your RPM signal from ECU to the tach? If its a simple 0-5V signal, then building your own light bar is easy, just get some zener diodes and LEDs. If the signal is a frequency, you might need to do a frequency to voltage converter chip, and then put on your zener diode tree. I'm pretty sure the cheapo shift lights have exactly that circuit in them (frequency to voltage, zener diode to fire the light at the right voltage, activation RPM adjustable by an adjustable resistance with the zener). 

https://www.instructables.com/id/LED-voltage-range-indicator/

https://microcontrollerslab.com/frequency-to-voltage-converter-circuits/

Back to the sequentials - there used to be a product called a Revlight that was a good one. A little bit flexible for good mounting options, a nice size and (IIRC) 14 LEDs that auto-adjusted their intensity for ambient light. I find a sequential light a lot more useful than a single one.

It's gone now, but there's another product called a Shift-i that's similar. Not quite so slick in packaging but easier to program.

It's not all that hard to make your own, you don't need an Arduino. The circuit diagrams are easy to find online. Just look for "DIY sequential shift lights". I was about to build one when I foud the Revlight back in 2007 or so.

Here's the Revlight in action:

In reply to Keith Tanner :

dang that is so intense. Not sure I know my right from left well enough to be in either seat...

Tom1200 said:

@wspohn it's a combination of having road raced 125cc bikes (2000 rpm powerband) and a professional hazard (Purchasing Analyst). Also I'm cheap & lazy; a Datsun A-Series engine will go 10 seasons at 7800 RPM, 5 seasons at 8200, 6 race weekends at 8600 RPM and 6 hours at 9000 RPM.

I totally forgot about a MSD adjustable box; as pointed out you really don't have time to look at much during an autocross run.

I used an MSD on the race cars as I could stick in whatever chip I wanted to customize the rpm limit. Put in a 6000 or 6500 for break in and a 7800 for race and not have to worry about it.  I mostly shift by tach anyway, but knowing that there is an electronic back up in case I am momentarily distracted (by some git spinning in front of me, perhaps) is a great comfort.  Not crucial if you aren't running an 'interference' engine, but IMHO absolutely necessary if you are.