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RB25DE+T Max Ignition Timing? Knock Headphones? Link G4 plugin

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Hi everyone I have been road tuning an R34 Sedan, RB25DE with a top mount Greddy/Trust style turbo on it, front mount intercooler, front-facing Greddy style intake manifold, 1000cc FIC injectors, Walbro 255 fuel pump.

I have a timing map from a rb25det map that I have pulled around 10 degrees from the entire map to get him able to start and move it around etc, we have since started some road tuning on it before it goes to the dyno, it's running around the 160kpa mark which is around 10 degrees of timing.

However, when I installed my knock sensor to confirm this tune I noticed that it sounds like it knocking the minute it goes into load, so is this amount of timing still too much? I reduced the timing to 5 degrees in a light load area and seem to sound like it was still knocking, this motor has VCT and was enabled at the time, I don't fully understand Nissan's VCT apart from that it is on or off and I don't know how much it advances the cam?

I was also only wearing a pair of AKG earphones with my knockblock as I haven't had a chance to get something better for tuning yet, is it possible I was getting some feedback with my earphones? any recommendations on headphones for tuning?

Attached is a picture of timing map, the tune, and log, keep in mind I changed a few things during this log, Toward the end of the log attached it started to sound fine under part load but still making knocking sounds in boost, AFR was around 11.5-11.8 under full load

Also was having issues with the lambda sensor output to the ECU so pay no attention to its logged values, seems to read correctly on the gauge though.

Thanks in advance

Simon King

Attached Files

It's been a long time since I've tuned an RB25DE+T so I can't give you anything to work with from memory. For comparison an RB2rDET with a decent turbo and manifold should be able to take 8-12 degrees around peak torque and 17-20 degrees at higher rpm on 15 psi boost. I'd think your starting point for timing at 160 kPa should be pretty conservative so I'd pick that you may not actually be hearing knock. It's always important to purposely induce a little knock so that you can be sure what it sounds like and can then separate it from normal background engine noise.

The VCT system is relatively simple but I can't tell you how much the cam moves sorry. I usually just do a run with it on and one with it off and the cross over points are then pretty easy to see.

No worries Andre thanks for the reply, I feel like I am on the right track and did feel conservative with timing that low, I did try to induce some knock but couldn't seem to tell the difference, I watched the webinar on knock sensor placement last night and I am going to drill out one of my knock sensors as you recommended as I was struggling to find somewhere to bolt it too.