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Engine Knock during acceleration

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Hi all, so the car I am tweaking (NA so no boost) is detecting engine knock during acceleration, The knocking goes away at and AFR of 11.2 but is present with AFR of 11.5 or more. There is no knock detected when running at a steady speed.

To my limited knowledge this seems very rich when I read about people getting better power at around 12.5 to 13. The system I am using (UpRev) does not offer acceleration enrichment.

Other than trying to increase octane what else can I do to lean out the AFR without getting knock?

Back off the ignition advance and/or use a better fuel?

AFR is a bit richer than I would expect for best performance as around 13:1 is generally close to optimum - but engines do differ on exactly what they like.

11.2:1 isn't bad. You can sometimes get more power with richer + more spark than less spark and leaner. You would have to get on the dyno and try different combinations of AFR and timing.

Thanks for the info guys. I found some information from the dark ages (2010) where this specific engine and ECU has a AFR lookup delay adn can take upto 1.5 seconds at WOT to reach the new AFR, Basically, the ECU will slowly taper to the new AFR target that is coming from the AFR target table lookup when you floor the accelerator and go WOT.

I have brought this up with the Uprev people as it is a setting that used to be configurable but is now not able to be set. Hopefully this can get added back in.

Just an update, after emailing UpRev they added the option to edit the "Fuel Target Lookup Delay" for my ECU and have set it defaulting to 0 seconds, nice service from UpRev :)

Hey Rob. what car are you working with? I've got some experience with UPREV. While every car is different I've found out on 350s and 370s the factory knock settings are too sensitive and really limit power.

Would you be willing to share some info on your car and build? Maybe I can provide some advice.

Hi Gary. Sure would becasue I am a noob :)

It is a Nissan Fuga, sold in the USA as Infiniti M45 so has the VK45DE engine. I have been emailing the UpRev guys a bit this last week, adn they have been really helpful. They added a new table to the ROM for my ECU for Knock Threshold (see attached) yesterday, so I havn't had a chance to logg with it yet.

Attached Files

yeah that is the same map on the 370z. we have found the factory knock settings are overly sensitive on the 370z and end up reducing that table a lot to helpcomabt false knock. the engines will also stop making power before it hits knock. id imagine it is similar to the vk but would know for sure unless we validate with knock listening device. uprev does a pretty good job. if you have any uprev specific questions you can email me at [email protected].

Thanks, I will. I am doing this as a hoby so learning as I go. I have the link G+ knock block, and I will get a local tuner to have a listen adn confirm,

I can confirm that on a 370Z the knock sensing is too sensitive and it pick's up false knock, especially when forcing boost into that motor. That and some other factors lead to the decision of going with a Syvecs ECU back then. We could extract quite some more power then.