Supercharger & Knock sensor ???
- Thread starter onestepx
- Start date
That's an interesting recommendation by your tuner. There is no limit per say to any properly functioning knock sensor. All they are is a Piezoelectric crystal used as a microphone for picking up the noise signature of Pre-detonation.
If you did want to make it more sensitve and couldn't change it via a programable ECU all you have to do is tq it down more so that the acoustic energy transfers from the block to the sensor with less resistance. (not recommended)
The limiting factor is the amount of response ecu has when it detects pre-detonation. Normally on a car that is N/A from the factory (like the NSX) the ECU only has limited a reaction because drastic measures are not needed to control it.
I wonder where he got the idea to replace them?
If you did want to make it more sensitve and couldn't change it via a programable ECU all you have to do is tq it down more so that the acoustic energy transfers from the block to the sensor with less resistance. (not recommended)
The limiting factor is the amount of response ecu has when it detects pre-detonation. Normally on a car that is N/A from the factory (like the NSX) the ECU only has limited a reaction because drastic measures are not needed to control it.
I wonder where he got the idea to replace them?
My Addiction my car is currently running the BBSC Supercharger kit I am currently running 15lbs of boost & 465RWHP.My goal is to get to 500RWHP or close to that.My current RC 550cc injectors & Walboro 255 in-tank fuel pump are close to being maxed out.So I will be switching to E85 fuel system upgrade as per my Tuner this should get us close to the 500 mark with some fuel upgrades & E85.He recommended if we can switch to the Bosch knock sensors that the will help with distinguishing noise from knock if I remember right more accurately than the factory ones.We had to stop tuning at 465hp to be safe till I upgraded my injectors extra fuel pumps etc.
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does this bolt right on?
From my experience in detonating engines, the knock sensor does very little when you are going WOT with some serious power. No one has cat-like reflexes to get off the gas that fast to make a difference.
it should trigger a "buy engine light" or auto pilot to your nearest shop.
The key foundation is for a proper build and tune. Nothing will substitute for that.
From my experience in detonating engines, the knock sensor does very little when you are going WOT with some serious power. No one has cat-like reflexes to get off the gas that fast to make a difference.
it should trigger a "buy engine light" or auto pilot to your nearest shop.
The key foundation is for a proper build and tune. Nothing will substitute for that.
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They Factory Knock sensor is probably best as it is designed by the Honda Engineers for the Specific Knock frequency the engine generates.
I'm in the process of setting up the New Motec Knock module, first you do a frequency analysis to identifiy the actual knock frequency of the engine.
Just fitting a different Exhaust system or major changes to the Chassis or Engine can change the Knock frequency of an engine.
I'm in the process of setting up the New Motec Knock module, first you do a frequency analysis to identifiy the actual knock frequency of the engine.
Just fitting a different Exhaust system or major changes to the Chassis or Engine can change the Knock frequency of an engine.
Just curious, what are the "limits" of the factory sensors according to your tuner? Knock sensors between manufacturers are made of different piezoceramic materials, each having different response times, output, aging, etc. That stuff is really just technical, nit-picky stuff. Then, there's resonant, non-resonant types, shielded, non-shielded types, etc. I think the Bosch is a non-resonant, shielded type. It's output, in general, will be less than our resonant sensor. But you're going to have a lot of faith in your tuner knowing when knock is expected to occur when calibrating your engine management. Just because they swap in a non-resonant sensor that has a lower "cleaner-looking" output doesn't mean that you'll have protection when knock occurs because the amplitude trigger hasn't been set correctly for this non-resonant type.
That may not be true on our OE sensors. Most knock sensors have the piezo element torqued separately to the sensor than the mounting stud to the engine. Of course, the more torque you apply past the recommended installation limit, the more risk you have of damaging the transducer and altering the output signal. The piezo material is ceramic and brittle (that's why they're torqued separately). Be careful with them.
I agree to an extent. The only way we have in the real world without access to direct cylinder pressure measurement (as the factory probably did) is to test the limit by self-destruction (and maybe the factory did that too). Maybe the factory only identified the theoretical limiting cylinder (cylinder 5 on the front bank due to intake charge, least cooling ,etc) and tuned the ECU knock sensor level to that particular cylinder. Autowave has a 1000HP NSX that's been working for awhile - I would ask them for help or copy what they did since it seems to work.
BTW, check out SAE Technical Paper 900488, Combustion Knock Sensing: Sensor Selection and Application Issues.
You can get an idea of your predicted knock frequency by knowing the cylinder bore. 90mm bore with a speed of sound of 600m/sec leads to a first mode frequency of ~6600Hz. This is a little higher than the valve train frequencies, but the valve train is, in general, pretty loud. Also, you can get an idea of the effect adding crap onto your engine does on the predicted natural frequency by striking the block sharply with a hammer and looking at your knock sensor output before and after any mods (supercharger, turbocharger, or even exhaust changes like whrdnsx said). This will give you some confidence in knowing the add-ons you've done have had little impact on your predicted knock frequency.
Bottom line is this:
If you don't know your tuner well, explicitly trust them, or they don't have an experienced track record with our cars, I would go seek Autowave's advice. Otherwise, I would trust the OEM system (sensors, location, and ECU safeguards) for a modest power increase (less than 500HP) rather than take the blind advice of a tuner I didn't have much reputation with.
My $0.02.
Dave
p.s. This is a cool article for the DIYer:
http://sine.ni.com/cs/app/doc/p/id/cs-398
Thanks Mac attack I have no where near as much knowledge as you have on this subject.This was just a recommendation from my tuner he is a very well known tuner that has done many turbo & supercharged applications on all types of vehicles including several Nsx s .I will take your advise and call Auto-wave as well as this should cut right to the chase of my answer whether or not the swap is worth it.Thanks for the advise.
If you find out more info please post back. I would like to learn more too. I don't have first-hand knowledge on this... I've just been studying it myself for my own custom FI project.
Good luck! 500 RWHP must be a blast :biggrin:
Dave
Good luck! 500 RWHP must be a blast :biggrin:
Dave
Will do spoke to Shane at Autowave but seems like no one has actually done this swap as of yet.He did recommend replacing the knock sensors that they do tend to get sensitive over a long period of time . I guess I will be the first .I will keep you guys posted of results .If someone here has done this Bosch Knock sensor swap please give us some feedback.Thanks
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