VersaTune User Forum

I was wondering if I could have some you more experienced and wiser users take a look at my log and tell me what you think about the knock spikes I have going on. It seems to happen mostly under part throttle/cruising loads and/or throttle tip in. Is there anything I can change to minimize this and is it a concern? The research I have done so far leads me to believe it is a product of an overly sensitive knock sensor and ECU logarithm from Mazda . Current modifications on the car are; Corksport TMIC, 3in intake (w/MAF cal), 3in downpipe back exhaust, & EBCS. I will be going over the intake clamps again tomorrow to see if that helps at all, but in the mean time, i just wanted to see if there was anything I could do or if I should even be that concerned about it.

On a side note, it seems like the PO installed the HPFP internals because I have not done them (yet) but fuel pressure never drops under WOT?!!! Unless I am not seeing something that you do!

Part throttle ignition retard is something that we see very often during spool up and low load situations especially with a downpipe and in those situations when the valve timing is high (>10-15) and the ignition timing is still low (<5 degrees, or even negative values).
So nothing to really worry about.

About the HPFP: the fuel pressure drops at WOT with OEM internals in the 2500-4500rpm range at high load, usually >1.9, but we've seen fuel rail pressure dropping as late as load 2.05 or as low as 1.8, and we've also seen fuel pump internals sticking and not providing fuel at high RPM and moderate load. So it's not a fixed air flow rate or fixed RPM you see them not being able to keep up. Also, they may just work fine up to, say, load 2.0 and next day you will grenade an engine because they failed at 1.7 at the same air flow rate (so same AFRs and same required quantity of fuel).
Just to be safe when this will fit in your monthly budget just get a set of internals: Autotech, CorkSport and VIS Motorsports are known to work just fine.

Ok! I have the internals and the o-ring kit from corksport at work waiting to be put into a spare pump i have, so it is very soon on the agenda. (This weekend!) Did you happen to see anything else concerning in those logs?

kwambe5 wrote: ↑April 15th, 2021, 11:37 pm Did you happen to see anything else concerning in those logs?

No. And the knock values higher than 1-2 occur where I just mention they usually do.

I have the same issue. This is my 5th tuned mazdaspeed and first mazdaspeed where i see tons of knock at cruising conditions. 2200-2700rpm. Of course, this is my first built engine, balance shaft delete, twin disc clutch, ported head mazda though. If any of my other mazdas knocked it was logged once in a couple months. This mazda though shows knock on every drive. This clutch makes a lot of noise too.

I will see 2-8 degrees of knock 10% throttle .4 load or very little during spool up when car transitions from closed to open loop.

At 0.4 load is where the input from the knock sensor starts being taken into consideration at those RPMs. It's just correcting timing rather than actual knock.
I also noticed that the cars with larger more permissive exhaust register knock in those areas a lot more frequently than the cars with factory exhaust in exactly the same conditions (fuel, load, temps, throttle input, whatever). I also started to notice exactly the same thing back in 2011 in my car after replacing the downpipe. So I think that plays a role in fooling the knock sensor as well, it's just a bit more noise to deal with.