Knock sensor Forged Engine

Chris' Garage

Greenie N00B Member
has anyone had issues with the knock sensor retarding timing at WOT with a forged engine? i'm getting a lot of knock after a recent forged build. not sure if it's false or not. going to call my tuner and get his thoughts but i was curious...

mahle 4032 88mm pistons
manley forged h beam rods
head refurbished
corksport cst4 turbo
new corksport injector seals
remanufactured injectors
cxracing fmic
autotech hpfp

21psi
93 octane
 
How recent is recent in terms of mileage? My friend built his Subaru engine with forged interals and it knocked for the first 1-2k miles after that it cleared up.

Who did the assembly and machining?
 
Can you give it a splash of corn and see if that helps? 1-2 gallons untuned should be safe and be proof enough.
 
not available around me. i think there is a gas station with 100 octane fuel. i'm going to try that, also going to record the audio from the knock sensor to try and narrow it down.
 
Also is the knock sensor appropriately torqued? If it's too loose it'll create more knock than actually is occurring. As Easter Bunny said how much knock? Is it knocking at idle?
 
knock sensor does not pick up knock at idle. i'm only worried about WOT. i replaced the knock sensor with new oem one torqued to 14ft/lbs. yesterday a 4th gear pull started at 3k instant KR 3.15 then tapered down to 0 at 3162rpm then .35 at 5600 rpm and 5900rpm then 0.7 and 0.35 at 6700.

the thing is at wot i can feel the car retarding timing as it's not a smooth increase in power

i'm not that familiar on the tune data from these cars, but i know the vitals. spark advance from the log shows 19 at the start
i left Will a voice mail but have not heard back yet, i'm sure he's busy.
 
800 miles rings could still be settling in as well perhaps not full compression yet? Have you checked the crank sensors? The one on the bottom of the block and valve cover as far as seated properly? How are the AFRs? No fuel leaking down the block I hope
 
nothing leaking, crank sensor i aligned to the 20th tooth when i assembled it, thing runs beautiful part throttle. no engine light. i just put 5 gallons of 100 octane in to half a tank of 93 octane, i'll do the logs again and see.
 
Post a log. 0.3-0.7 KR is nothing to worry about in the high rpms.

The 3 at 3k we'd need to see a log for. Sometimes you can get a bit of KR on spool up. But it's also possible that the tune is a little aggressive down there
 
I just finished tuning with Ryan@PD; when I asked him about some KR at the start of a few pulls he said it isn't anything to worry about during spool-up. ¯\_(?)_/¯
 
I had increased part throttle KR, which seems to be normal when going forged internals, but no out of the ordinary KR on WOT on my car. My tuner was able to filter out the part throttle KR to the point where it is similar to where it was on stock internals after a drive on the max value on the AP, just to help with my paranoia LOL.

I went 87.5 Mahle 4032 pistons with Manley H beam rods, DIY build after cracking two pistons ringlands at 78000km (48467 miles). The bores still looked really good so went with a light hone and refit stock sized pistons. I do have a bit of piston slap at idle now though but no noticeable wear marks yet checking with a camera into the plug holes after 4000km (2485 miles) so sending it as is till any issues arise :)
 
Don't log throttle position unless you're troubleshooting something. Always log pedal position so people know what you're commanding the car to do.

Edit: You're better off using some kind of ethanol content in the tank vs race gas as alcohols in DI engines give WAY more effective octane than normal.
 
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thanks for all the help, with the 100 octane the knock is less on WOT below .7 there is some on tip in. but that's expected. i will fill up fresh with 93 and submit those logs to Will. this forged motor was not cheap so i just wanna make sure it's 100% good.
 
Chris' Garage said:
thanks for all the help, with the 100 octane the knock is less on WOT below .7 there is some on tip in. but that's expected. i will fill up fresh with 93 and submit those logs to Will. this forged motor was not cheap so i just wanna make sure it's 100% good.
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Been watching/commenting on your videos on youtube man and I’ve enjoyed them! Glad to see you joined MSO and these guys have great knowledge on here! Oh and @Raider I suggested this site for him in his comments considering it is the best speed forum around lol
 
StreetSpeed6 said:
Been watching/commenting on your videos on youtube man and I’ve enjoyed them! Glad to see you joined MSO and these guys have great knowledge on here! Oh and @Raider I suggested this site for him in his comments considering it is the best speed forum around lol
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Thanks for the support. hoping to have more videos soon. i have a new issue :)
 
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