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Some one knocked and instead of opening the door you only check from peep hole..

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So as title says i had a little bit of knock go on in my fresh new sr20det.. Once I saw the knock flash light, hooked up to my power fc, turn on i let got off the accelerator. Car started smoking a little so Decided to take a look with a inspection camera and see if my pistons are still there.. There all there and there is no sign of melted pistons anywhere.That was close.. But I'm still worried. I noticed I have some very small spots on the piston witch I showed to my mechanic wich talked to his tuner. The tuner says there might be a possibility that even if there is non Visible damage to the pistons that i my have melted the side of the pistons between the piston rings.

At this point I really don't know what to do. I'd run a compression test but even if the numbers are good, tuner says that the piston could fail on me at higher rpms.. And I really don't want to go through another rebuild after only 900km..


just did a compression test..

cylinder 1: 140 psi

cylinder 2: 150 psi

Cylinder 3: 150 psi

Cylinder 4: 150 psi..

Have you got access to a leak down tester (cylinder leak tester)? are you running a catch can?

What colour is the smoke? black or blue?

What modifications are you running?

Hi Chris! I dont have access to a leak down tester, and no I'm not running a oil catch can at the moment.. The smoke is white. I have actually solved the smoke problem. I took the exhaust system off the car and had some condensation going on, had clear water coming out the muffler and some coming our the down pipe and test pipe. My exhaust system is all straight, and the remus muffler I have has been "lightened".

I'm running a fully rebuilt engine. Cp pistons, manley rods, Bc 264 cams, Bc springs and retainers, 850cc injectors, gt3071 twinscroll, fullrace exhaust manidfold, z32 maf, cometic headgasket.

At the moment my mechanic and I have decided to take the pistons out the engine and see if the "maybe" knocking signs on the pistons are just a low resolution of the camera, or if the knock is there and if it reached the in between the piston rings.. Unfortunately the knock detection on the power fc isn't as good as others..

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you mustve been knocking really bad to hurt a setup like that, maybe bad fuel. What boost are yo running and was it tuned?

Hi Tommy. I'm using V-power fuel.. I'm @1.2 bars. but never past the 5500rpm cause of the knocking detection turning on.. I'm trying to tune myself taking it a step at a time on the road.. unfortunately i don't have a knock headset.

Talking with my mechanic tonight lead to the decision of selling my Apexi Power fc and z32 maf to step up with another ecu. Unfortunately i live need Pisa and there aren't any good tuners. They really blow up brand new engines even if they have the tools! My mechanics tuner should be taking care of me, but isn't very close but is good at what he does. The only thing is he only wants to use EFI Technolgy ecu's, that uses map, but is pretty old. I would of preferred a Haltech but he won't tune anything else. I've seen the results tonight and I was impressed. I will be letting him do the job, but this doesn't mean I will be quitting or giving up. Plus he will help me out in learning more.


What kind of knock values are you seeing on the power fc?

The picture isn't really the best, it looks like it's been running rich or getting oil in the chamber, it's very wet and dark.

I've attached pictures from an engine I scoped before carrying out some work. The plugs had signs of detonation, which led to me scoping it.

Attached Files

My peak value while data logging was 56%.

Sorry bout the poor quality, but that was the only camera i could find in the area.. Yes it is a little rich.. At Idle I'm seeing 13.2 to 13.5 Afr cause of the bigger cams..

Here are my plugs right after the last pull with no sign of knock..

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those are really rich, im thinking your low compression or smoking is due to too rich of a mixture thats washing down the cylinders. First tune your a/f then timing and go back to a/f to fine tune it. you should be able to get stoich even with those cams.

As Tommy mentions, those plugs look exceptionally rich or fuel fouled. What you can find is that even with no sign of damage to a piston crown, knock can lead to damage to the ring lands where a section will break out but remain trapped until you actually remove the piston. This is pretty unusual with a forged piston though and particularly given your current low boost and low rpm. If you're backing off as soon as the knock warning comes on then I'd be surprised if you have done damage. With a forged piston and a relatively low specific power level it would take a little bit of sustained knock to cause damage.

The picture of the piston crown isn't conclusive that it's showing damage from knock - Mainly as has been mentioned already it's showing signs of oil consumption and rich running. I'd also be suspicious of your turbo causing your smoking issue.

Thanks to all! I've decided to tune my A/F again! lets see if things get better.. I'm just a little to scared to do damage so I'm trying to take a step at a time..

Thanks again!

Hello.. I Tuned my fuel table again and had really good results.. only thing is that i was getting a high reads from the knock sensor. The knock sensor is brand new but not a nissan one.. at 1500rpm and no load it read 116.. wich is crazy high. i then decided to go back with my old sensor positioned between 3rd and 4th cylinder.. number where so low i wanted to swap the position to the oem position. Happens that being the engine 20 years old while torquing the knock bolt the thread was pulled out.. So unlucky! think I have a haunted car! But the sensor readings are still a myth at the moment..

In the mean time I put my Power Fc up for sale and was able to do so! Now I will be changing ecu and getting some professional help, and will be able to assist to the hole tuning process.. This will help me a lot to learn with a hands on experience, and will be able to see if the tuner is doing a good job as i have learned here or if i can tell him to stop and go elsewhere. I have already pulled the engine out so we can check the pistons to see if there was actually heavy knock going on.. and after that we will be making a new Harness, so will be checking out the wiring course, and making a first tune on a engine dyno.

So i will be updating asap with some pics of the pistons in hand!

Its too bad your tuner doesnt want to touch haltech. If he did play with it, i bet he would be really happy with it. The haltech has really awesome datalogging features. I think thats one of the things i like best about it. you can log like 192 channels to pc (or 32 directly to onboard memory)

Id suggest getting your hands on a ps1000. you wont regret it. Id suggest getting the sport 1000 with the 2m autospec harness, and then build from that. super easy to do if you just take your time. comes with relays and fusing already built in. look into it.

Yes I really wanted to put in a Haltech, but no one wants to take their time and play with it.. I've contacted the Italian reseller and they only do NA cars and don't want to do my SR20.. I was willing to take the 4 hour drive... At this point i'll just follow my mechanics tuner and go with this italian ecu, witch on hit Fiat X1/9 turbo is doing a excellent job! I want to try and talk to the tuner again and see if he wants to try with the Haltech.

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