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Old 05-11-2011, 07:27 AM   #1
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Knock Sensor on SR20DET??

Ok, someone explain to me how this works, and what it actualyl does with the ECU and timing. I just blew up a motor because of detonation, and its partially my fault.

What can I do/use to monitor timing and/or knock?
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Old 05-11-2011, 11:49 AM   #2
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The Knock Sensor and How it Works*|*EngineBlox
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Old 05-11-2011, 12:13 PM   #3
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you can monitor with a knock light/gauge, safc has the option to monitor also iirc. if you don't mind driving around with a laptop ... there many different ways to monitor. Get a good tune to avoid.
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Old 05-11-2011, 12:13 PM   #4
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Knock sensor doesn't even work past 4000 rpm or so on our cars, so it's not to blame.

FWIW: There really isn't a factory one out there IMO that works fast enough to prevent an engine from detonating apart. Usually (9/10 times) it's due to a bad tune, lack of fuel, or a combination.
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Old 05-11-2011, 12:48 PM   #5
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Ok, I didnt know it doesnt work at 4000rpm. I had plenty of fuel, but I was tuning with an SAFC2 and pulling too much fuel out to make a good AFR, (740cc injectors), and it tricked my ECU into thinking it was getting less air, and therefore advancing timing like a mother fucker and detonating it all to hell I should have listened to other people.

So what do I do now for tuning? PFC?
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Old 05-11-2011, 12:59 PM   #6
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Quote:
Originally Posted by BlackZenkiS14 View Post
Ok, I didnt know it doesnt work at 4000rpm. I had plenty of fuel, but I was tuning with an SAFC2 and pulling too much fuel out to make a good AFR, (740cc injectors), and it tricked my ECU into thinking it was getting less air, and therefore advancing timing like a mother fucker and detonating it all to hell I should have listened to other people.

So what do I do now for tuning? PFC?

And that's usually the issue, that AFC really offers such little 'true' control that it does funky stuff behind your back...it's like EFI Live with the GM stuff...so many oddball defaults/tables that can really wreck havoc

Tune wise, you would be ok with a PFC, but you'll need a tune then. To me if it's a general street car, why not go with a JWT or Enthalpy tune?
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Old 05-11-2011, 01:20 PM   #7
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I'd rather go Enthalpy or JWT myself as well, but I want to eventually get a 3071 and make some real power, and I dont want to have to buy expensive ECU's twice, and I like the idea of being able to retune every season and watch everything closely.
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Old 05-11-2011, 08:41 PM   #8
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You can send your "Tune" back to JWT/Enthalpy and have it redone for the 3071R. It'll probably cost you $150 or so to have it retuned and safe...
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Old 05-14-2011, 01:37 PM   #9
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Quote:
Originally Posted by BlackZenkiS14 View Post
I'd rather go Enthalpy or JWT myself as well, but I want to eventually get a 3071 and make some real power, and I dont want to have to buy expensive ECU's twice, and I like the idea of being able to retune every season and watch everything closely.
Just get one, and have it setup for the injectors/maf to support the power you want to make, and be done. It's only 100 dollars for a reflash, which you shouldn't even need to go from stockish to a 3071. I know (personally) I wouldn't be looking at a tunable setup unless I was looking to make 475-500...but that's just me. It's not going to hurt to go with a tunable setup, but to me it introduces way to many issues for a street car.

Also, if you want to watch things, get a NissanDataScan setup with a Blazt cable...plugs into the factory consult port and works great for live sensor scanning, logging runs, etc etc. They're silly cheap and are a great resource.

Quote:
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You can send your "Tune" back to JWT/Enthalpy and have it redone for the 3071R. It'll probably cost you $150 or so to have it retuned and safe...
100 dollar reflash Just log the files and go from there.
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Old 05-16-2011, 11:20 AM   #10
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Quote:
Originally Posted by BlackZenkiS14 View Post
I'd rather go Enthalpy or JWT myself as well, but I want to eventually get a 3071 and make some real power, and I dont want to have to buy expensive ECU's twice, and I like the idea of being able to retune every season and watch everything closely.
get a pfc (500-800 used) or nistune setup. both of these setups allow the tuner to make a tune for your engine. both can be found for around the price of a new jwt/enthalpy board. every engine runs differently and having a tune for power and reliability on every car with the same setup will either be on the safe side makeing less than peak power or on the power side, possibly damaging the engine. i ran my pfc on my stock setup and made 40-50 whp just from being able to road tune the base map. being able to re tune locally or even by your self is worth the small additional expense of a standalone imo especially if you can get a cheap pfc or nistune. i know you have already experienced what happens to an engine when you cheap out on tuning.
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Old 05-18-2011, 12:50 PM   #11
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Why the SAFC is NOT a wise tuning option*

Quick and dirty... On a stock ecu the safc interupts the maf voltage signal on its way to the ecu and decreases the voltage. Decreased voltage equals decreased airflow. It is doing this to trick the ecu into thinking less airflow is entering the engine. In turn the ecu will compute a shorter pulse width to compensate for a larger fuel injector. This allows the user to achieve the desired air fuel ratio.

The bad part is that airfuel ratio is only a small small fraction of a "tune". In fact timing is substantially more important to making power and preventing knock. So, when the SAFC makes these corrections to the maf signal to achieve the desired shorter pulse width outputs it is essentially tricking the ecu into "thinking" less air is entering the engine. Anyone familiar with the basics of tuning will tell you less air/less load requires MORE timing. The lookup values the ecu is referencing to come up with shorter pulse widths also correlates to more advanced portions of the timing map. The exact amount of timing you were running is unknown and I can only speculate. If for example the ecu was referencing the third column from the right on the stock timing map you would be running ~17* around 5000rpm. It is my opinion that with 91 octance gas this is definitely too much timing. When using an SAFC to correct for fuel you are essentially flying blind on the timing map.

*The only minor exception to the rule that the SAFC is not wise is if you have a mail order rom tune that gets you in the ballpark and only minor minor corrections are made.

I highly recommend an ecutalk (http://www.ecutalk.com/) to monitor your actual timing. It is arguably expensive but I have found it extremely useful.
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Old 05-18-2011, 01:12 PM   #12
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Quote:
Originally Posted by mct3351 View Post
Quick and dirty... On a stock ecu the safc interupts the maf voltage signal on its way to the ecu and decreases the voltage. Decreased voltage equals decreased airflow. It is doing this to trick the ecu into thinking less airflow is entering the engine. In turn the ecu will compute a shorter pulse width to compensate for a larger fuel injector. This allows the user to achieve the desired air fuel ratio.

The bad part is that airfuel ratio is only a small small fraction of a "tune". In fact timing is substantially more important to making power and preventing knock. So, when the SAFC makes these corrections to the maf signal to achieve the desired shorter pulse width outputs it is essentially tricking the ecu into "thinking" less air is entering the engine. Anyone familiar with the basics of tuning will tell you less air/less load requires MORE timing. The lookup values the ecu is referencing to come up with shorter pulse widths also correlates to more advanced portions of the timing map. The exact amount of timing you were running is unknown and I can only speculate. If for example the ecu was referencing the third column from the right on the stock timing map you would be running ~17* around 5000rpm. It is my opinion that with 91 octance gas this is definitely too much timing. When using an SAFC to correct for fuel you are essentially flying blind on the timing map.

*The only minor exception to the rule that the SAFC is not wise is if you have a mail order rom tune that gets you in the ballpark and only minor minor corrections are made.

I highly recommend an ecutalk (ECUTalk - News) to monitor your actual timing. It is arguably expensive but I have found it extremely useful.
I completely understand this. Thank you so much for the information.

Does anyone know if Nistune software can moniter knock?
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Old 05-18-2011, 01:23 PM   #13
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I highly recommend nistune. There really is no reason to go with anything else unless you have a special requirement it can't provide (launch control, anti-lag, auxilliary outputs to trigger nitrous/meth injection, 2 step limiter). The only thing close (cost wise) is the maf version of the pfc. It is alittle more expensive but arguably easier to use because of how comparatively few variables the user has access to.

They recently released a new version of the tuning software that incorporates a knock readout. 4x4le could definitly elaborate on that.
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Old 07-29-2011, 11:20 PM   #14
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Quote:
Originally Posted by mct3351 View Post
Quick and dirty... On a stock ecu the safc interupts the maf voltage signal on its way to the ecu and decreases the voltage. Decreased voltage equals decreased airflow. It is doing this to trick the ecu into thinking less airflow is entering the engine. In turn the ecu will compute a shorter pulse width to compensate for a larger fuel injector. This allows the user to achieve the desired air fuel ratio.

The bad part is that airfuel ratio is only a small small fraction of a "tune". In fact timing is substantially more important to making power and preventing knock. So, when the SAFC makes these corrections to the maf signal to achieve the desired shorter pulse width outputs it is essentially tricking the ecu into "thinking" less air is entering the engine. Anyone familiar with the basics of tuning will tell you less air/less load requires MORE timing. The lookup values the ecu is referencing to come up with shorter pulse widths also correlates to more advanced portions of the timing map. The exact amount of timing you were running is unknown and I can only speculate. If for example the ecu was referencing the third column from the right on the stock timing map you would be running ~17* around 5000rpm. It is my opinion that with 91 octance gas this is definitely too much timing. When using an SAFC to correct for fuel you are essentially flying blind on the timing map.

*The only minor exception to the rule that the SAFC is not wise is if you have a mail order rom tune that gets you in the ballpark and only minor minor corrections are made.

I highly recommend an ecutalk (ECUTalk - News) to monitor your actual timing. It is arguably expensive but I have found it extremely useful.
Is there any way to bandaid the timing issue? Such as retarding the timing alot so that under WOT it advances it to where you want it?
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