[dk10438]

recently I've had an issue with knock on the OTS Stage 1 map where the boost gauge will occasionallyl flash. I went back to the OEM map and would occasionally would go into low boost mode which made me think that the problem might be poor fuel quality (I live in So Cal and only 91 is available). Anyway, I'm still not sure if it's the fuel, hot ambient temp etc. Which parameter is used to assess for excessive knocking? Is it the DA? I've used Torco as well as adding a little E85 to the tank (1 gallon on a full tank). I read a thread where it was considered to be safe to add a little E85 to help with knocking but since I'm on stock injectors, I didn't want to push it. Last time I data logged my IDC was 97%.

car has catless MP, catback, 2.75 CAI

Thanks

 

[pfl]

I'm in SoCal as well and having had 2 GT-Rs now, I can tell you the stock tune does knock, BIG TIME, and I've tried most gas stations here in OC. Torco does raise the octane but has some unexplained behaviors that make the car not run 100%. I've ran torco at track and still went Low Boost Mode on both 2012 and 2015 (stock 100%). E85 I don't believe is proven to help in GT-R. It does help with raising the octane but then you'll need more of it to make the same power and stock ECU is not aware of it so it may be a wash.

 

[R35 Dan]

recently I've had an issue with knock on the OTS Stage 1 map where the boost gauge will occasionallyl flash. I went back to the OEM map and would occasionally would go into low boost mode which made me think that the problem might be poor fuel quality (I live in So Cal and only 91 is available). Anyway, I'm still not sure if it's the fuel, hot ambient temp etc. Which parameter is used to assess for excessive knocking? Is it the DA? I've used Torco as well as adding a little E85 to the tank (1 gallon on a full tank). I read a thread where it was considered to be safe to add a little E85 to help with knocking but since I'm on stock injectors, I didn't want to push it. Last time I data logged my IDC was 97%.
car has catless MP, catback, 2.75 CAI
Thanks

I had the same issue with the OTS Cobb maps and I have the same mods as you. I unmarried the COBB AP and its now fine (Back to stock ECU).

 

[IPAlpha]

recently I've had an issue with knock on the OTS Stage 1 map where the boost gauge will occasionallyl flash. I went back to the OEM map and would occasionally would go into low boost mode which made me think that the problem might be poor fuel quality (I live in So Cal and only 91 is available). Anyway, I'm still not sure if it's the fuel, hot ambient temp etc. Which parameter is used to assess for excessive knocking? Is it the DA? I've used Torco as well as adding a little E85 to the tank (1 gallon on a full tank). I read a thread where it was considered to be safe to add a little E85 to help with knocking but since I'm on stock injectors, I didn't want to push it. Last time I data logged my IDC was 97%.

car has catless MP, catback, 2.75 CAI

Thanks

How much boost are you running?

 

[dk10438]

Map 1 16psi

 

[Boostd4]

Unfortunately we just have really bad fuel here in CA. I had the same issue when I was running the OTS maps from Cobb. I typically saw knock when the IATs were relatively high. When I would mix in 3 gallons of even 94 octane into a full tank I would see zero knock.

Did you do any datalogs to see how much timing the car was actually pulling?

 

[dk10438]

i just moved to a new house and have to climb a hill to get to there so I'm not sure if I'm knocking 'cuz of different gas OR if I was always knocking and this hill just put extra load on the car under hard acceleration and created a situation where the knock was going to be evident.

until last night I didn't even realize which parameter to look at for knock. I guess it's the dynamic advance? 0 is no knock -3 is severe knock?? and -3 triggers a detonation warning?

 

[Church]

I guess it's the dynamic advance? 0 is no knock -3 is severe knock?? and -3 triggers a detonation warning?

-3 is not severe knock. It's at the limit of what is considered acceptable and will cause your display screen to blink.

-6 and higher would be considered too high and close to putting your car into limp mode.

Cobb's OTS maps are crap. If you buy a Cobb make sure you get a custom tune.

E85 will work well to keep your car from going into limp mode. 2-3 gallons of E85 for a full tank of 91 on a stock DBA will work great. Stay away from Torco, it turns your cats red and clogs things up.

If you want to run a bit of E85 on a tuned DBA, make sure you know how to data log. Especially if your running the crappie Cobb DBA OTS tunes that are so rich.

 

[Boostd4]

Also, keep in mind the car will never be truly free of some sort of detonation (at least on 91 fuel). As long as you're not seeing any of this knock at high rpms under full load you should be ok. I see the car pulling a little timing here and there in the weirdest places (low rpm, close to zero load) on 91 octane. Just really bad fuel....

 

[Church]

I see the car pulling a little timing here and there in the weirdest places (low rpm, close to zero load) on 91 octane. Just really bad fuel....

That's Cobb's software glitch I have been talking about for years. It happened when I had my 2010. I know it's a Cobb glitch because if I loaded up an older tune before Cobb updated the software it would go away. They didn't help me at all and blamed it on my car.

It wasn't the car, it was the Cobb's software for the CBA cars that has the issue.

 

[dk10438]

I'm inclined to think it's just poor quality gas...
I'll try to do a little more data logging now that I know I have to keep an eye on dynamic advance. Seems to be a problem when ambient temps are higher so maybe it's not really an issue anyway.

 

[Church]

I'm inclined to think it's just poor quality gas...
I'll try to do a little more data logging now that I know I have to keep an eye on dynamic advance. Seems to be a problem when ambient temps are higher so maybe it's not really an issue anyway.

You have a DBA. There is not issue with Cobb's software for the DBA with knock that I know of.

 

[gyoja]

Also, keep in mind the car will never be truly free of some sort of detonation (at least on 91 fuel). As long as you're not seeing any of this knock at high rpms under full load you should be ok. I see the car pulling a little timing here and there in the weirdest places (low rpm, close to zero load) on 91 octane. Just really bad fuel....

cylinder pressures and torque are actually highest mid-rpm range - where *most* knocking is likely to occur. In the bigger builds you also need to worry about ignition which may show up as knock in higher rpms if you don't have good spark and gapped correctly (thanks John Visconti!!!)

 

[Boostd4]

That's Cobb's software glitch I have been talking about for years. It happened when I had my 2010. I know it's a Cobb glitch because if I loaded up an older tune before Cobb updated the software it would go away. They didn't help me at all and blamed it on my car.

It wasn't the car, it was the Cobb's software for the CBA cars that has the issue.

I took this into consideration (based on your threads

), but even with my Tim Bailey tune it shows up here and there at low load situations. In terms of CBA speak, I'm seeing -2 to -307...very minimal. It's simply fuel in my case...gotta go E85 soon.

BTW, the issue disappears when I dump in higher octane fuel.

 

[Church]

I took this into consideration (based on your threads

), but even with my Tim Bailey tune it shows up here and there at low load situations. In terms of CBA speak, I'm seeing -2 to -307...very minimal. It's simply fuel in my case...gotta go E85 soon.
BTW, the issue disappears when I dump in higher octane fuel.

That's good to hear.

 

[anx21]

I live in LA and I've definitely had this problem as well, and I'm running a custom Cobb tune on 91 w/ FBO. I feel the bad quality of the fuel is exacerbated by the terrible roads, and sometimes I'll have the boost gauge flash after I hit a really bad bump. It's never persisted though, and restarting the engine fixes it. Also, I've noticed that the amount of times the boost gauge flashes definitely varies on each gas refill. On most refills the sensor goes off very rarely (0-10% of drives), but I remember this one time when after a refill the sensor would go off about half the times I drove the car.