I know my gsr was reaching almost to 17 afr under acceleration on my first runs when I was initially adjusting basemaps.

but I never heard knock or any other choking I could feel the sound change when it ran lean but it didn't stumble

this b20 is acting strange.
any slight lean condition makes it fall on its face around 2500-3000 rpm and then it starts accelerating normally

the afr shows around 15.5-16

but datalog shows it go up to 16 and then drop and then spike back up and drop like square wave.

all other sensors show normal


is that because of 89mm crank more sensitive to lean condition or something other?

I checked vacuum leaks and all other things

all seems normal and it can drive all day and suddenly just throw that **** at me and then disappear again.

 

Are you running neptune?

 

yep why?

 

I have some questions\observations in regards to neptune.. Is this problem when a laptop is hooked up or just random with or without laptop connected? Ill be starting another thread here in a day or two..

 

Usually i have my laptop hooked up but today i didnt and it happened randomly again and just once out of the blue again. I have a feeling its same issue that i had before but this engine is more sensitive to changes in afr and when it shifts towards lean condition i get these hiccups

 

Wideband could be reading improperly, timing could be an issue. Cruising afr I never go past 15.5.

 

its all been checked before over and over wideband timing sensors dizzy wiring ecu soldering etc

 

How much timing are you running when these hiccups occur and im assuming its low load.. What issues, did you have before? Ive heard that not enough timing in low load can cause hesitation/hiccups but i am not positive.. Have you pulled a plug and seen any signs of detenation? I was hoping someone else would chime in and give some tech info on the question you asked.. Anyone want to share some tech/advice on the relationship of stroke, rod/stroke ratio, long rods, and short rods in regards to timing? Short rods=less time at tdc and long rods=more time at tdc

 

if you like send me your calibration and a log file
and im sure i can help you out.

 

yea im gonna upload it

so to the original question.

is 89 and higher rod/stroke ratio more sensitive to detonation?

 

its not more senstive
but higher rod stroke ratio allows less ignition timing advance.

 

Because...

 

I believe its because the piston is at tdc for a less amount of time..

 

Backwards.
When the piston sees less time at TDC it is less likely to detonate there.
The ATDC slope is faster, so combustion can happen faster, allowing more advance.

If this is a random occurrence you may have an incorrect IAT or ECT scale or an ignition/timing issue, but it may just be a misfire, not detonation.
Verify again that your base ignition is correct and your timing belt is properly tensioned, then make sure your dist cap isn't full of carbon. While it's off, check the coil resistance.
Lean cylinders are also common in B series, so next time it happens kill the engine and pull the plugs, look for one with discoloration.

 

Correct. I made my previous comment... kind of in passing because I was at the end of lunch... to try and spur a little more tech in the discussion. A little "why" usually goes a long way toward understanding

 

but the piston speed is higher with bigger stroke.

VI according to what you said the b16 would have the easiest detonation and b20 would have a lot less...

just don't feel right for some reason

if looking at tdc dwell time alone maybe
but taking into account the piston speed and the angle with bigger stroke

 

when you look just at the R/S ratio a b16 is will allow more advanced timing then a B20
but the ideal ignition timing has a lot variables
like : Fuel,rod stroke ratio, stroke, bore,Compression, IAT, ECT,EGT, Exhaust back pressure and so on.
so its not that easy as most of etuners think.
sure its not that hard to find a ignition timing that works,
but to find the right shape of the timing curve requires long expierence in tuning.

 

yea after 3 years of reading and attempting to street tune and spying on rich lol I still cant understand ignition adjustments.

I got the fueling pretty good but not ignition.



on this one I had to increase the iat compensation when it gets past certain IAT temp because it was getting a lot leaner with hotter IAT but stock is negative compensation.
am I doing it right?