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Poor mans real time tuning


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Seen this mentioned and it got me thinking.

Build a square wave oscillator of the appropriate amplitude and frequency range.

Flex fuel custom OS. Pay attention to the spark blend map and add in some reasonable numbers to the flex timing table that are well above those in the 98 table.

Steady state on the dyno, wind the oscillator up to increase spark. Find MBT or knock limit for load and rpm. Write timing down on a piece of paper. Repeat for next cell.

Then repeat for fuel.


Am I dreaming or was the guy who mentioned this but with regards to a GM PCM actually onto something? 


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It is already incredibly easy to find the knock threshold for 98, peak power timing on e85 is also fairly commonly known, as well as easy to find with a dyno.

The stock timing maps are very close to perfect off boost, there are very minor gains to be had, and generally only need some adjustment when the boost is turned up.

Live tuning would be a cool feature but I don't think it would speed up the tuning process, given that most tuners already know where the timing needs to be set.

Even with large cams and custom os, the learning curve is fairly easy to dial in the fuel.

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Was thinking for blokes like me who don't know where those limits are and would like to learn it by doing. I'm looking to hire dyno + operator time at $250 an hour so this method will save me a lot of money. I only envisage this method would be used for WOT. 

I'll be bold, you could save me some time and money here lol. FG Mk1 XR6T, stock cams, exhaust + dump + flapper mod, F6 turbo, standard intake with hole cut in airbox, stepped intercooler, valve springs, 18psi boost both 98 and e85, 1000cc injectors. Commanded fuel vs actual +/-2% depending on atmospheric conditions verified with AEM wideband.

98 Spark & Fuel




e85 Spark & Fuel



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Assuming that the car is running those timing numbers as the actual final timing and it is following that lambda...


That 98 tune looks ok, it might have too much timing from 4500 up but maybe not. Before it comes on boost, before 2250, you might be able to get more timing into it, perhaps 2 or 3 degrees. You'd wanna verify with knock ears, I use tuner nerd. 8 degrees for 18psi is a good starting point with a cold intercooler. Leave the iat spark correction stock and it'll do it's job when it heats up. The fuel looks good too.

On E85 you can run more timing than you have there. It will make power the whole way up to 20 degrees but DO NOT put that much into a stock motor. I would add 4 degrees the whole way up to 4000rpm, for a max of 17 degrees, then carry that number out to redline. I would lean it out a bit as you can run E85 leaner than 98. Make it the same as your 98 tune or even 0.1 leaner. You could let it drop straight to 17 degrees after it comes on boost if you felt like it.

If you have load in your log you can cross reference load and rpm to see exactly where the tune goes through the map. Tuner nerd records boost, rpm, afr and knock noise so that will also show you where it knocks, if at all. It comes with headphones too so you use them first then use the software to pinpoint it.

Fyi you can run an engine very lean and it'll be fine, but letting it knock will hurt it. Don't run it lean all the time but having it go lean while tuning is fine, providing it doesn't knock from too much timing. Cylinder heat reduces resistance to knock so there is a correlation there. At the above mentioned timing figures it will not knock on E85, even if your factory knock sensor is recording noise. I turn the knock sensors off for E85 but generally leave them on for 98.

It's worth a mention that boost spikes from a gear change in an auto car on 98, can and will cause knock if it isn't addressed.


Anyhow there's a bit of info, it's what I would do for road tuning. I have a reasonable amount of dyno experience having done some 150 runs on my home built and self tuned 711awkw territory, as well as many other customer cars. You will find a bit more power on the dyno but that info will get you 95%  of it. No need to run a stock motor too hard anyway.

Final bit of advice for this post, keep your wideband where you can see it and periodically check that the fuel is there at wot. A blocked fuel filter, blocked injector baskets or failing fuel pump will lean it out.

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I have the tuner nerd setup. Being using it on my VF which I am more at home on. Bloody great bit of gear. Yeah wide band is were I can see it. Still got a boost spike still on shift. Not as bad as it was when I got the car it used to spike up to 3psi. Have done the usual tricks, now I'm just slowly bringing in a little more injector cut and backing out the spark cut a bit. Got the spike to just over 1psi now so big improvement. Have to be careful and try and keep the reported torque during shift at around the same level as before so I know I'm not hurting the trans. 

Thanks very much for your insights and guidance. Bloody legend mate 👍

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  • 5 weeks later...
  • 1 year later...
On 5/3/2022 at 5:09 PM, CHRISNOTH said:

hi puff have you had trouble tunning a 07 bf i cant stop it going in to cut out mode at full throttle i have changed tq settings but it does not help any ideas ?


I am experiencing the same problem. Still trying different ideas out so I'll let you know what I find.

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I must have missed this. I have had it happen on a few cars but I can't remember what I did to fix it cos it was years ago. I'm not tuning much these days so it isn't as fresh as it would be.

I'm usually happy to have a look at someone's tune if they want to post it up or pm me. It helps to have a log of it happening with some explanation of what's occurring.

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