DIY Knock sensor listening - detecting detonation

[gazzy2000]

 pl0x said:

i just rang up Mitchell motorsport who built my motor, asking about what my compression would be and he said he didnt work it out and wouldn't know?? do you not have to do this to build a engine?

and then i asked about my low boost/boost pills in the right place and he reackons 7 & then 9psi is standard for a b4. pretty sure its not unless every other b4 ive been in wasnt standard even tho the owners thought is was...

told him what i was thinking sti ecu, single turbo etc and he said the difference between 9.0:1 to 8.5:1 wouldnt change to much and cause a det issue, more the ecu itself being more advanced or higher tune or some crap.

Glad i didnt pay for the rebuild or id be even more pissed off how he cant answer afew q's without being a wank. wont be taking my car there...

Sorry i cant answer those questions but i will say, DO NOT take anyones advice as gospel! there really are some dick cheeses out there and they just dribble chit out their gobs for the sake of talking and robing you blind!

[gazzy2000]

Mind you, i havnt had this compression discrepancy 100% confirmed by a rocket scientist, but the evidence has stacked up with all the testing.

I have spoken to alot of ppl bout this incl lots of conversations with Kevin at PBMS.

One subaru mechanic that i asked about the compression ratio difference (who is a smaller subaru workshop specialist) said straight away "dude, you got to pull the timimg" and the only way to do that is with an after market ECU.

So really, if the compression ratio is not the issue (of which i really believe it IS the issue), at least what ever it is you can tune it out with an after market ECU.

I wud have been finished weeks ago!!!!

[pl0x]

yea he was going about how you would need to change sooooo much to get a sti ecu to run it and how it would be cheaper for aftermarket ecu,

Are the heads the same? if so the alone different thing that would be hard to change is compression right? (aswell if that is the only different thing then it would point towards that being your issue)

p.s. i agree tho, go for an A/m ecu, id rather get that for the money than change the compression and not have a tuneable ecu lol

[gazzy2000]

 pl0x said:

yea he was going about how you would need to change sooooo much to get a sti ecu to run it and how it would be cheaper for aftermarket ecu,

Are the heads the same? if so the alone different thing that would be hard to change is compression right? (aswell if that is the only different thing then it would point towards that being your issue)

p.s. i agree tho, go for an A/m ecu, id rather get that for the money than change the compression and not have a tuneable ecu lol

yea thats the thing, i was told teh heads are pretty much the same, so where is the change in compression done?? Heads or pistons??? phuck that chit, i say just get a a/m ECU and tune it to suit.

Man, the amount of aggro and time i cud have saved myself if knew that in the begining!!

Plus the money spent diagnoseing and testing would easily amount to $500

[pl0x]

yea agreed...

im just gona try get mine running normal boost and leave as TT for now

[gazzy2000]

heres the knock wav file

http://www.yousendit.com/transfer.php?action=batch_download&send_id=789223472&email=66dbd371e6145f1e10b3168c622eb306

[gazzy2000]

 gazzy2000 said:

heres the knock wav file

http://www.yousendit.com/transfer.php?action=batch_download&send_id=789223472&email=66dbd371e6145f1e10b3168c622eb306

OK, that wav file is best played in the program it was recorded in, so download the wave file and play it in a program called spectrogram, download it here http://www.electronics-lab.com/downloads/pc/003/

install it, open it, goto > file > analyse file > then browse to the wave file > let it load > then click play in bottom right

this is cool as you can see the graph and frequencies etc

[gazzy2000]

 pappu said:

what area u from bro..

and maybe host the wave file somewhere so can be downloaded easy .. i wud like to hear what det is lol..

PS> just a theory but what if the factory knock sensor is buggered and causing false det noise - just wondering thats all

maybe try the wrx ecu and injectors and afm - i hear thay run higher compression than the sti

Sorry man, missed this post.

I am in Timaru, SI

Wav file is availiable to download as per other posts

My DIY knock sensor picked up all the det and the factory one wasnt even connected for that run, so wen the factory one is connected it must be working otherwise i wud get really bad det.

Dunno bout a std wrx ECU and AFM, just cant afford to trial and error any more.

With this engine and ecu, its simply just trying to det all the time and the knock sensor will be working overtime. If i recall the snap-on engine analyser showed knock voltage constantly evan under light boost evan in safe mode.

Still trying to get evoscan to log some more data too.

[gazzy2000]

UPDATE: possumlink purchased ;D

[Swindog]

Problem solved

Possum links are the shiz.

I hook my up to my lappy and tune away. Gives good readouts in real time and i can record a good run and sit back and watch fuel and boost curves afterwards. Also solved my idle problem.

[Guest boostin]

 gazzy2000 said:

UPDATE: possumlink purchased ;D

And I assume you've been kicked out and are now living in the car??

[gazzy2000]

 boostin']

[quote name='gazzy2000 said:

UPDATE: possumlink purchased ;D

/quote]

And I assume you've been kicked out and are now living in the car??

man, its a very very VERY touchy subject, its okish for now, but the guilt trips will no doubt surface again soon.

God i hope a A/M ECU fixes everything!

I'm scared man!

[webup]

Knock at cruise is quite common on these engines.

Its knock under WOT you really dont want

[Guest]

say if you had a forged engine,would a knock sensor pick up knock on cold startup?iv herd a few forged motor cold start up and they dont sound very nice,mines not to bad thoe.

[gazzy2000]

 webup said:

Knock at cruise is quite common on these engines.

Its knock under WOT you really dont want

not when the ECU is isnt matched for your engine CR i.e. timing is 10 degrees advanced, thats what the problem was here

.. the amount of knock that makes you go wooo, pull over right there and go home ASAP as it just sounds completely wrong. The kind of knock that you wudnt dream of even trying to see if it was there under WOT.

on a factory set up (i.e. TT engine with TT ECU) they may well do the odd knock, but i bet you it aint nothing like what was experianced by mine

[gazzy2000]

 sti8u said:

say if you had a forged engine,would a knock sensor pick up knock on cold startup?iv herd a few forged motor cold start up and they dont sound very nice,mines not to bad thoe.

its normally piston slap if heard on cold start up, of which is a different frequency to knock/det, so no the knock sensor isnt listening on this 'frequency' if you like..

this " Forged pistons are usually installed with greater clearance than cast pistons. The expansion rates between the two are different and more cold clearance is required for forged to ensure good running fit when up to temperature. You only need a extra thousandth of an inch clearance to make the engine noticably noisier!

In a forged piston set up, I would be a bit concerned if there wasn't at least a bit of slap when cold!

Gentle acceleration until up to temp"

[Guest]

Good shit this.