I just noticed the tables for "RPM derivative speed control" aka RDSC aka "spark smoothing" (at least I think spark smoothing is the same thing?) and apparently it retards spark when the engine speed is increasing and advances when engine speed is decreasing... so that got me wondering if it would be useful for slowing down or reducing the strength of low-RPM/low-throttle cam surge.

Very little has been written about this, so I'm guessing no, but I figure it can't hurt to ask.

Apparently EFI Live has these tables, but HP Tuners doesn't.

 

You mean this table?

 

Sort of... There are also a bunch of options to configure how much smoothing to apply, and in what conditions. This is in Tuner Pro:

 

I have not tried the additional parameters in tunerpro, but it has been my experience that just turning on spark smoothing in hptuners does nothing good. Those other tables could make a big difference.

 

A lot of vehicles have spark smoothing turned on from GM

 

Yes, but for an aftermarket cam it seems to make matters worse if you just enable it through hptuners without altering any of those other tables. As an example, my 2004 gto stock file has smoothing on, but with the current 226/230 cam I have it turned off, as enabling it destabilizes rather than smoothing anything.

 

I typically dont change it, if its on I leave it and if its off I just leave it off. I typically calm it down with other tables but I dont think there is a right or wrong way to do it if you achieve the same end result.

 

This is interesting… I have spark smoothing disabled on my car. This thread makes me tempted to buy an EFILive setup just to play with these tables 🤣🤣🤣

 

EFI Live does not have the tables posted in Tuner Pro. It does not have the gain table. Have tuned thousands of 896/411 pcm vehicles with efi live and hp tunrs and its never been an issue not adjusting those tables.

 

PCM Hammer + Tuner Pro might be a better option than EFI Live, that's where I got that screenshot.

The only catch is that there's a lot that varies by operating system. I'm using 12587603, which has more tables defined than most.

Plus there's the extra hassle of finding the best XDF for your operating system... I'm going to work on making that easier, but I'm in the middle of rewriting the UI right now and I want to get that finished first.

 

Some of the spark smoothing parameters are listed as manual transmission only, which always led me to believe that they may be triggered by the clutch switch. However, I have no idea if this assumption is correct. I know very little about coding, so I mostly rely on the descriptions others have added.

 

I am pretty sure spark smoothing is MPH based and not clutch based

 

There are some tables that are based on RPM, MPH, and gear, but I don't see anything based on the clutch switch.

If anyone wants to see the nuts and bolts you can grab a copy of Tuner Pro, and get the "mother of all 7603 XDF files" xdf from pcmhacking dot net (IIRC we're not supposed to link directly to other forums) and look at the attached stock 2004 Corvette .bin file.

 

On the Gen3 PCMs I only see spark smoothing trigger on a fast throttle transition like a quick shift near the limiter on the manual trans cars, it will pull timing and put it back in and can make for what feels like a lazy throttle response. I've never seen it trigger or do anything at all under normal conditions on these PCMs which also means it's not going to do anything for cam surge.