Thread: Timing map, how to tune.

Right now I just retarded the timing a little on boost, but I would like to know how can I tune better my timing map and actually gain some power out of it.

I wrote this long explanation out, and then I closed the tab by accident.

First off, ignition tuning is done properly with a load/brake dyno.

That being said, you should be able to take the values you have at the top of your N/A map and work from them. The rule of thumb is 0.75 degrees of retard for every 1 PSI of boost.

So if you have +35 degrees at 4500 rpm and 100 kPa (atmospheric) then for 1 PSI at 45000 rpms you should have +34.25 degrees. At 10 PSI you will have +27.5 degrees advanced.

This is going off of the advice of well know Nissan tuner Enthalpy.

Also, read up on the ignition section of this calibration guide to give you a better understanding of what's going on:

http://www.vems.co.uk/forum/index.php?topic=97.0

Thats really a goofy rule of thumb when you think about it. Its makes intuitive sense that talking about 15psi from a small T2x turbo is different than 15psi from a T3+ etc, and that using the same timing curve for both is a bit silly. Less obvious is how the different back pressures of each affect the timing you run. If your running a T25 or T28 your better off just copying a stock Nissan timing curve than guessing a curve without a dyno. Your best bet is to set it on a dyno.

You've really got two different factors that affect your timing curve- where the engine wants the timing to be (aka your minimum best advance or MBT) and where your knock threshold is. It is a common fallacy to assume that if you keep advancing your timing power will keep increasing, and your only limited by knock. Hey, I thought that way too, but its wrong. Assuming you aren't limited by knock, there's really a point at which when you keep advancing the timing power starts to plateau or drop off. That point is your MBT. On a pump gas SR (especially crappy gas of course) your generally limited by knock first, but on race gas you really can hit the MBT first. Watching a 400+ hp car (large turbo, cams, on race gas) make more power as your pulling timing out is really an eye opener.

Typically on a SR what you want to do is limit your timing around your peak torque, and then start to feed it back in aggressively. What I think is useful is after doing some baseline runs just pull 2-3 degrees of timing across the entire curve and watch what happens. If you've got points where its not making a difference, what you've just done is better than getting more power, you've gotten a more reliable tune (and if your power doesn't change at all you've got something reaaaaaally wrong!). Also, its amazing to watch how just 1 degree of timing can cause a noticeable difference in your result.

Find an experienced shop (with a dyno of course) and work with them. Even dynojets are just fine for tuning WOT performance.

quote:
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It is a common fallacy to assume that if you keep advancing your timing power will keep increasing, and your only limited by knock. Hey, I thought that way too, but its wrong. Assuming you aren't limited by knock, there's really a point at which when you keep advancing the timing power starts to plateau or drop off.
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100% agree. this phaenomenom you can watch on a brake dyno really good.

for maximum performance you have to set your timing map on a brake/load dyno. street tuning will not give you 100% of available performance.
some points in the map you can tune to maximum limited by knock. others you don't have to tune to maximum timing to get most hp.


greetings ronny

Not to nit pick, but that’s for a 8.5:1 engine. For 9.5:1 he recommended .875/ lb boost, and that was for a good starting point. As Calum mentioned it depends on a lot of other variables. An example would be when I changed cams, he changed my entire timing curve, because my peak torque had moved, and he could be more aggressive up top due to the cams characteristics.