# Knocking with Stage 2 Cobb



## maxzugkraft (Feb 25, 2008)

Hi Guys,

I got a Cobb from Benj last year and have been using Stage 2 & LC5 for my ADM2009 on the road since. Great burst of power and improved drivability.
(I'm on 98RON Shell vPower, HKS res midpipe, K&N air filter element)

I took it to the track last month (18 deg C) and just yesterday (23 deg C).
I noticed flashing of the boost gauge - which I think means that there is "knocking". This usually happens after the 3rd or 4th lap, especially if I hit the rev limiter. Sometimes it occurs even at 5000rpm in 2nd gear and tends to linger for about 5 to 10 seconds. I feel the car is not as fast as it normally is.
How do I fix this?

Is this BAD for the engine?

Thanks in advance.


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## Adamantium (Jun 24, 2002)

If it's happening it's terrible for the engine. It's like hitting the pistons with a hammer.

The car will pull ignition timing to combat it which is why it may now feel flat by comparison. If you see it happening you shoud back off immediately.

Call Ben and disses it with him, you'll need to datalog and he'll send you an updated map.


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## CT17 (Mar 25, 2011)

What Adam said.


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## maxzugkraft (Feb 25, 2008)

Thanks guys. Will get in touch with Ben.


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## bobel (Jul 26, 2010)

Yep as the guys say talk to Ben, but knock sums do not necessarily mean pre-ignition in the sense of knock, I believe the threshold Set by Cobb is a safe level and you can breech it without damaging your engine assuming you don't drive all day with it reoccurring but safe tunes should keep you below the threshold so you'll need a tweak!


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## ChuckUK (Jan 1, 2009)

Does this knock feature exist on a EcuTek map ? good safety feature.


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## CT17 (Mar 25, 2011)

I think it's a car feature, not dependant on which tuning option you choose.


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## bobel (Jul 26, 2010)

bobel said:


> Yep as the guys say talk to Ben, but knock sums do not necessarily mean pre-ignition in the sense of knock, I believe the threshold Set by Cobb is a safe level and you can breech it without damaging your engine assuming you don't drive all day with it reoccurring but safe tunes should keep you below the threshold so you'll need a tweak!


Yep it's a inbuilt feature of the cars ECU, it's actually a mandatory device on all cars nowadays what the Cobb does is adjust the threshold at which the ECU pulls timing, I believe the threshold is around -730, above this level the ECU will pull timing as it tries to regain control of the combustion within the cylinder. The Cobb also visually links the boost threshold breech to the boost gauge on the MFD so you can see the engine pulling timing when it occurs (i.e. the boost gauge flashes)

The knock sensor is in simple terms a microphone which has been tuned to listen for a specific range of frequencies that are typically omitted from the engine when you get preignition/knock but it does not necessarily mean that when you see the boost gauge flash that's what is happening as any noise that the engine generates in the frequency will cause a reading but ideally regardless of what causes the reading your best that it is not occurring!

Anyways Ben knows best in the OP's case he'll have it sorted and safe in no time


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## maxzugkraft (Feb 25, 2008)

Thanks guys.
That is reassuring to know that is does not necessarily mean damage when it flashes. However, if you do tune it to stop that, would that mean that the resulting tune would have to be even more conservative/safer than the existing OTS Stage 2 map? Might as well go to Stage 1 map then?
How would that work? Hmmm...


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## [email protected] (May 16, 2003)

maxzugkraft said:


> Thanks guys.
> That is reassuring to know that is does not necessarily mean damage when it flashes. However, if you do tune it to stop that, would that mean that the resulting tune would have to be even more conservative/safer than the existing OTS Stage 2 map? Might as well go to Stage 1 map then?
> How would that work? Hmmm...


best contact me for a custom tune rather than the generic OTS maps, so i can calibrate specific ign, fuel, for what your GT-R responds to


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## bobel (Jul 26, 2010)

I would opt to get Ben to do a custom tune for you, it will be dialed in to perform to the optimum for your specific engine, each engine is different and requires slight tweaks to ensure your good and safe

Don't worry about your engine, the stock ECU retards timing and you don't even know its happening, the VR38 is robust and should withstand some knock (if this wasnt the case the place would be littered with broken vr38 blocks) but I would not drive it WOT when you know there is an issue. Just to clarify I'm not saying its OK that your car is pullin timing as that's not what you want and it's the engine response to a problem, and as its a response it will not prevent the issue but only react to it so I would recommend getting some logs at the very least and getting Bens advice.


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## ChuckUK (Jan 1, 2009)

CT17 said:


> I think it's a car feature, not dependant on which tuning option you choose.


The boost gauge flashing I mean ?


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## David.Yu (Jun 28, 2001)

ChuckUK said:


> The boost gauge flashing I mean ?


It's a Cobb feature. Don't know if ECUtek can do it too, but the standard car doesn't.

Very impressed with my latest tweaked map from Ben on my car. Greatly reduced smoke under acceleration and no knock at Spa even when hot, running 1.2 bar map and using only 98RON Total (you can't get 99 in Belgium).


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## Litchfield (Feb 26, 2008)

If enabled the Ecutek map can flash the check engine light at a pre-defined knock amount.


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## David.Yu (Jun 28, 2001)

Litchfield said:


> If enabled the Ecutek map can flash the check engine light at a pre-defined knock amount.


Ooh, that's even better! It's easy to miss the boost gauge knocking unless you choose it as your main gauge.


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