Setting up shiftlight

[LesG]

Hi all,

I finally got round to installing a DRE shiftlight, which was really easy to fit, and works well, but I'm  looking for some advice about setting it up correctly! I've dug out my dyno sheet, so can see where my maximum power is, but am I right in thinking I should use the rev point where my maximum torque figure is produced, as the point where I set the 'change up' lights to come on? Or do I continue revving the engine to the maximum bhp point? I run an Emerald, and should look where the soft cut is set too, to make sure I'm making the best of what I have, without unnecessarily over-revving the engine (1.8 K Series).

Any advice greatly appreciated!
 

[Jonathan Kay]

Which 1800 version? What's your desired maximum engine speed? Any modifications? Which gearbox?

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Can you post the dyno report?

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You can't predict the optimum change points from those two values alone.

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You'll probably get some useful advice here, and I'll see what the archives say. But how about using an acceleration app on a smart 'phone so that you can suck it and see?

Jonathan

 

[Jonathan Kay]

This might be a good point to start in the archives. It includes DVA's recommended prediction software, but there might be something more modern...

Jonathan

 

[LesG]

Hi Jonathan,

my engine was built by Rob Morley, with a spec including forged pistons, steel rods, a vhpd head overhauled and tweaked by DVA, and includes 285 cams with solid lifters. I run the 42mm Jenveys, and use a 4-2-1 SLR manifold. Don't have a clue how to upload the dyno sheet in here, but happy to mail or text it over to you?

Cheers for your help so far!

 

[LesG]

Forgot to add; I use the CC 6 speed gearbox 

[Jonathan Kay]

You can upload the image to this thread by following the notes in the Forum User Guide. Let us know if you get stuck.

Jonathan

[LesG]

[LesG]

Ta-dah!

[Jonathan Kay]

:-)

Well done, but it's a bit small.

I'm guessing that you used this tool:

 

You can probably get a bigger version to show using this tool instead:

 .

(I can't resize images after uploading.)

Jonathan 

[SimonR300]

I think generally shifts lights are positioned in line of sight so you don't have to take your eyes off the road to look at your tacho and therefore serve as a visual red line to avoid loosing power by running into the rev limiter (assuming there is one).  Normally you would have a soft cut and a hard cut to the ignition.  Although you can generally hear when to change gear, it is not usually accurate enough to protect the engine or avoid hitting a limiter.

You can configure the lights to suit yourself, so yes, you could decide that your preference would be to change gear at max torque.  Although it is too small to read the values, it looks like your bhp continues to rise and would do so a little if projected on from the rev limit.

Usually the shift light is set for a gear change just before you hit the soft cut or rev limiter and probably a few (100-250rpm) revs below that to allow for reaction time. That will depend on how quickly the revs rise and of course they will rise quicker in 1st gear than top.  (I don't know whether the DRE lights allow you to set a value for each gear, but some systems like Motec do.)  The other point to consider is where your limiter is set to cut the ignition, common sense suggests that there is no point in revving the engine beyond the point where both torque and bhp are starting to drop off, even if mechanically it could handle it.

I would suggest you work back in evenly spaced rpm gaps to somewhere close to where your torque and bhp graph lines cross (as the car won't stop accelerating at that point).  So you end up with a ready, steady, change now series of lights moving from left to right.

You'll have to experiment until you are happy with the rpm gaps based on how much time you want to react.  For instance, assuming you can use all 5 lights, you might start by having the first light come on at say 1500rpm before the cut and space the others out evenly at 1500/5= every 300rpm.   Or you could make the gaps varied or maybe bring the last two lights in together or maybe they will all flash when you need to change.

Depending on your driving style, say on the road, you might already have your hand on the gear lever before the the first shift light comes on.  Or if you are on a track and keeping both hands on the wheel is preferable, then think about the time it takes your hand to reach the gear lever to pull the next gear, can be under a second.

You could watch a few onboard videos like this

to get the idea.  Jon Barnes has his lights set to have two reds at the end of a multi-coloured sequence which flash together when he really must change gear.  It is just down to personal preference.

 

 

[LesG]

[LesG]

This is the biggest the site tool will allow me to post.

Thanks also to SimonR300, I can see some fun ahead tweaking this! The DRE has 6 led's which light up in pairs, left to right, from the 'get ready', 'get set', and 'change up now' stages. What I'm looking for when I'm sprinting, is to know that I'm in the right gear, using the best of the power available, rather than changing up too early, but protecting the engine by not overrevving it. I never look at the Rev counter (it's the original xflow version, so useless with this engine), and just listen to the engine, but there are many times, midway around a sprint course, when corners and gradients are coming at you pretty quickly, when I doubt whether I'm in the correct gear.

[Jonathan Kay]

[Roadsport06]

When I fitted mine I spaced the lights coming on over a large rev range. I can't remember what it was, perhaps 500rpm. The lights took a while to all come on then flash. For me it was then trial and error to adjust so now I get the lights more closely spaced so the lights begin coming on and I quickly need to change gear or I'll hit the rev limiter. The lights are therefore not a big distraction as they are only on when I really do need to change gear quickly. With a revvy k series I would have thought changing near the rev limit is going to be best.

[LesG]

Roadsport06; yep, that sounds about right, keeping my K in its powerband is the reason I fitted these, I just need to get s rough idea about setting them up, then tweak as I go on! Having these in my  eye line, rather than trying to switch between the road ahead and a Rev counter, is going to be much easier.

 

[SimonR300]

Hi Les,

Some shift lights have down change strategies too but I suspect that isn't available with the DRE.  The point being that you could consider setting the first pair of lights to a point in the rev range that you don't want to fall below.  So if you are in the power band you want they will stay on and as soon as you fall below the band, lights go off and you know to downshift.

Then obviously the remaining two pairs can be your upshift lights.  So with only those two sets available you will have to open the rpm gap to maybe 1000rpm to start with and then you might be able to close it to 750 - 500 rpm as you work out your reaction time needed.

You have a bit of a plateau in your torque curve below 6000 rpm, so you could try setting the first pair of shift lights somewhere between 5300 and 6000 rpm, the next pair at somewhere between 7000 and 7750 and the change gear now at 8000 rpm, so if you are a bit late changing, you just run into the bhp plateau which I assume is closely followed by your soft cut/limiter.

Simon

[LesG]

Simon; yep, this is exactly what I was hoping to set up, basically letting me know I'm in the powerband. If I set the 'Lo' pair to come on at 5300rpm, and the 'Hi' pair to come on at 7500rpm, the DRE automatically selects the midway point between those two settings, and that should be my torque sweet spot? There's also the 'Flsh' point I can use to come on just before the limiter, which I think is 8200, but I'll need to open the Emerald software to check. I can see some 'spirited' blats around the Lakeland fells coming soon! 

 

[O.G.]

Acceleration of a car is proportional to the torque at the rear wheels. Theoretically this is Engine Torque x Gear Ratio (of the gear your in) x Diff Ratio. Obviously the variables are Engine Torque and the Gear Ratio as Diff Ratio is a constant.

For Max overall acceleration you need to plot the graph of torque at the rear wheels for each gear against RPM. You set your change up lights for the revs at the point between say 3 & 4 when the two torque figures at the wheels are the same.

Typically this is in the range of 500-750 revs more than max torque depending on the ratio difference between the gears. I've never done the maths and just use these figures on track days, close enough.

O.G.