Hi, this engine has so far 1200 miles and every time I go in traffic at low rpm (betwen 2,000-3000rpm) the engine makes a strange noise, it is like a piston skirt knocking on the cylinder wall, above 3500rpm the noise stops, when the engine is idle doesn't make this noise, it makes this noise all the time no matter if the engine is cold or warm, it's the same, I use 98 octane pump gas, I tried to use Octane booster but the noise is still there. Thanks.

 

bump, any suggestions???

 

management? could just be knocking, period.

 

I'm using VAFC, should I switch to a knock sensor ECU?? currently I'm using a chipped P28 Erick's Racing

 

Your engine is "knocking" "detonating" or what ever you want to call too much timing, compression, not enough octane. Get a better base map.

 

Its probally The Je pistons

They dont run an Offset wrist pin ...

makes more power but they knock loud ...

 

I think you ment to say 89 octane?

With 12.5:1 CR you need atleast 93 octane. If you think it is piston/skirt knocking pull your head and check the cylinders.

I've heard forged pistons knock also

 

what did you gap the rings at? too small of a ring gap will cause the end gap to completely close up under high heat and gall up the piston's skirt, which cause it to knock like that

 

i ran exact same setup almost. JE pistons with 11.5:1 on 84mm bore. Same noise pulled head and waddaya know, my skirt on piston #1 was all messed up..car ran lean somehow. i was using a hondata. ..my suggestion is to pull ur head and take apart your block. wat i did to diagnose the problem was to put the car on lift and listen from the oil pan while the car was running. the sound was significant. i hope it isnt as bad as mine..good luck.

 

do you know the piston to wall clearence?

 

yeah piston to cylinder clearance is 0.004" was double checked as piston specs required

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote"> I think you ment to say 89 octane?
With 12.5:1 CR you need atleast 93 octane. If you think it is piston/skirt knocking pull your head and check the cylinders.

I've heard forged pistons knock also </TD></TR></TABLE>

I live in Guatemala I have access to 98 octane pump gas from Shell, that's why I decided to go 12.5:1

 

Ok Im running a Built B20 vtec with Wiseco 12:1 84mm Pistons and a Built B16a2 head. Over all I have 13:4:1 compression. Now I had my motor tuned with Hondata S200 on 93 Octane.

Now the motor made alot of Pinging noise around the same RPM range your in. So if you do the math. Pump Gas is to Lean for that High of compression. I live in Texas and alot of Gas Stations sale 100 octane gas. So I tried it. Not as much motor noise as before. But there was a big difference in performance. If I were you. I wouldnt run anything under 100 octane.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote"> i ran exact same setup almost. JE pistons with 11.5:1 on 84mm bore. Same noise pulled head and waddaya know, my skirt on piston #1 was all messed up..car ran lean somehow. i was using a hondata. ..my suggestion is to pull ur head and take apart your block. wat i did to diagnose the problem was to put the car on lift and listen from the oil pan while the car was running. the sound was significant. i hope it isnt as bad as mine..good luck. </TD></TR></TABLE>

Was this sound doing all the time or only at certain rpm?

 

if I ran low octane and Low RPM's. Like 2k to 3.5 k then it would clear up after I would get in the gas. But I also could hear the noise at like 70mph if I would just stomp on the gas at times. I know run 100 or 110 octane gas. And it cleared the noise up. 110 octane works the best.

 

Tune the car and you wouldn't be worried about this... 12.5:1 B20/Vtec tuned last night, 93 pump gas, happy as could be.

 

The problem isnt neccesarily a lean condition.. Just too much timing and the motor sees alot of load under those conditions. You can either get rid of the vafc.. or keep using it just get someone to burn you a chip with some timing pulled out of that area.

I bet with the timing gets pulled back the knocking will go away. W/ 98 octane you should only need a few degrees out unless you got a really aggressive chip in there.

 

The B20 vtec I did last night was happiest leanest (big surprise) and ignition timing at part throttle was cruicial to having the car run right.

Tuning is key.

 

it sounded like it stopped after higher rpms...but if u are able to put the car on a lift you can make sure cuz i thought it was just valve train noise. it was also at certain rpms if u were looking for an answer to ur question.

 

higher Octane and Tunning Cleaned all my probems. I mean. With 93 I had pinging all the time. But with 100 or 110 octane my set up runs smooth.