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Old 11-07-2006, 07:02 PM   #1
turboso
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Default How to identify engine knock??

If I accelerate my car in neutral up at 3000 up the noise of the engine change a little bit, like more troaty or kinda rumble. Is this engine knock?? Sounds like regular engine sound to me but I dont know. The sound is very low if you have radio on you wont be able to hear it.

Also when the engine knock happens happens, is the performance affected??? Should I feel the car hesitating??


Also if I mix with the empty gas tank 91+100 octame gas, how long does it take to the "new mixed gas" get into the engine and be burned? From 1 to 10 miles??
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Old 11-07-2006, 07:31 PM   #2
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a.) your engine should not knock on a free rev like you are describing.

2.) yes performance is hurt when you engine knocks. Timing is pulled. the level of hesitation you will feel depends on the level of knock.

and mixing 91+100 isn't going to net you much without a tune, i suggest sticking to regular premium unless you get a custom map made for the higher octane.
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Old 11-07-2006, 07:36 PM   #3
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BBs in a tin can.


And bull**** mixing 91+100 wont get him much. The stock ECU will make power up to about 100 octane. Anyone that has ever run Torco or 100 unleaded race gas can tell you that. Someone did a dyno comparison a while back, 93 pump vs a mix that came out to about 98 octane, and it was in the 12-15whp range. No tuning, no other mods.
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Old 11-07-2006, 08:57 PM   #4
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So is not possible "less likely" to hear the engine knock in nautral "free reving of rpm's". Is engine load required to reproduce knock???
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Old 11-07-2006, 09:15 PM   #5
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Quote:
Originally Posted by turboso View Post
So is not possible "less likely" to hear the engine knock in nautral "free reving of rpm's". Is engine load required to reproduce knock???

In all but the most extreme cases yes. To have detonation (knock) with no load, you pretty much need a blown motor.
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Old 11-07-2006, 10:08 PM   #6
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Quote:
Originally Posted by Davenow View Post
BBs in a tin can.


And bull**** mixing 91+100 wont get him much. The stock ECU will make power up to about 100 octane. Anyone that has ever run Torco or 100 unleaded race gas can tell you that. Someone did a dyno comparison a while back, 93 pump vs a mix that came out to about 98 octane, and it was in the 12-15whp range. No tuning, no other mods.

right, so his car will most definitely make that much power. it depends on where you are at in your dynamic advance map prior to the rise in octane. if you're already maxed out guess how much power it will net you?

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Old 11-07-2006, 10:19 PM   #7
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Get a knock sensor, or knock light. I'd be impressed if you could hear knock on a modded car, especially with a downpipe.
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Old 11-07-2006, 10:48 PM   #8
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Not to highjack the post but this is along the same lines.

Is it possible for higher octane to hurt performance?

Hypothetical...

On 93 octane... a car is already running max timing. Drain the 93 and run straight 100 (or even mix it for that matter)... will your car lose power? From what I understand... higher octane fuels (gasoline) are actually less explosive (contain less energy) than plain old 93 but more power is made because they have a higher combustion temp which allows timing to be added. If timing can not be added, can power loss be noticed?
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Old 11-08-2006, 01:18 AM   #9
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So what can be the change in the tone of the engine, the car is a 2006 STi. It sounds like engaging a vtec "no flame plz"
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Old 11-08-2006, 01:35 AM   #10
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Are you sure it's not just the turbo spooling?
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Old 11-08-2006, 02:24 AM   #11
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^ thats what im thinking. i notice a change around 3000 as well, though i have only really noticed when the engine is loaded, im pretty sure its the turbo engaging.
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Old 11-08-2006, 07:06 AM   #12
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Yes higher octane gas can cause a loss in power, but you have to be beyond a certain point for that to start happening, you need to be beyond where the IAM is already maxed out. HOWEVER

No turbo subby, ESPECIALLY AN STI, is going to have the IAM maxed out on 93 pump. (I am speaking of a stock car)
Get yourself a scanmaster, and monitor things on pump gas alone, then monitor it on 100 octane.

Why is it that EVERYONE that has run torco, EVERYONE that has run tolulene, EVERYONE that has run methanol, all have gains?
And, why is it that datalogs from an otherwise stock WRX and STI will show the car getting MORE TIMING on higher than 93 pump gas, showing gains up to close to 100octane?? Thats hard proof. You cant dispute logs showing the ECU giving less timing on pump gas.





As far as if its the turbo spooling, put the car in gear and accelerate away from a stop, if you hear the sound at 12mph, its the turbo spooling.

Last edited by Davenow; 11-08-2006 at 07:16 AM.
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Old 11-08-2006, 01:16 PM   #13
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i didn't say it would provide no gains, i said they would be neglible and for real gains to be made with 100 oct a custom tune is necessary. being able to crank up the boost, lean it out AND add timing is where the gains are made on 100 octane.
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Old 11-09-2006, 11:15 AM   #14
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Any people with changes in the tone while hitting 3000 rpms??? Is the engine supposed to sound more robust??
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Old 11-09-2006, 11:39 AM   #15
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Quote:
Originally Posted by turboso View Post
Any people with changes in the tone while hitting 3000 rpms??? Is the engine supposed to sound more robust??
Yeah, it usually does. Try engine braking in second from 3k+, it's quite a bit quieter once it gets below 3k.
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Old 11-10-2006, 03:07 AM   #16
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I hear what sounds like a knock/rumble between 2.5K and 3K revs.
It 'feels' like the kind of noise that with a loud exhaust, makes the Subaru 'throaty burble' noise. I'm having gauges and cold air fitted at the dealer on 24th November. I've mentioned it to them already. PM me in case this thread drops and I'll PM you back with my findings. *crosses fingers, stroked warrantee card and lemon disclaimer*
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Old 11-10-2006, 03:41 AM   #17
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everyone's noises seem like normal suby noises
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Old 11-10-2006, 05:13 AM   #18
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Quote:
Originally Posted by Davenow View Post
BBs in a tin can.

Yippers, that's teh knock for ya.
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Old 11-10-2006, 01:25 PM   #19
turboso
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Quote:
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Yippers, that's teh knock for ya.
Are you saying that the sound around 3000 rpms could be knock??? I even hear the sound in neutral with no load at all.
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Old 11-10-2006, 04:00 PM   #20
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oh crap....thats no good


and you should tune for higher octane then what you are TUNED FOR or you can leave unburnt fuel

my tuner told me not to do it...but i was already doing it lol, but i learned my lesson
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Old 11-10-2006, 04:07 PM   #21
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Quote:
Originally Posted by turboso View Post
Are you saying that the sound around 3000 rpms could be knock??? I even hear the sound in neutral with no load at all.
Then definitely no.

Again, $100 and you can get a knocklite, probably worth it if you're that worried.
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Old 11-10-2006, 04:13 PM   #22
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could it also be the OL/CL trasnition?
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Old 11-10-2006, 05:21 PM   #23
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Quote:
Originally Posted by turboso View Post
Are you saying that the sound around 3000 rpms could be knock??? I even hear the sound in neutral with no load at all.
No, I'm saying that knock sounds like bbs in a tin can. Not at all like the sound you are describing. And you shouldn't hear knock under no load unless your engine is seriously borked.
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Old 11-10-2006, 05:37 PM   #24
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wrong thread

Last edited by BBBsti LTD; 11-13-2006 at 02:50 PM. Reason: wrong thread
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