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-   911 / 930 Turbo & Super Charging Forum (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/)
-   -   knock sensor (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/405586-knock-sensor.html)

dsiegel360 04-23-2008 03:09 PM

knock sensor
 
Does anyone make a knock sensor suitable for the 930?

The "safegaurd" by J and S electronics is off the market until they come out with their new and improved version. The new one retards spark for any cylinder that needs it. It has general retard controls and a host of other stuff. I told the dude who designs and owns the company that I don't know if I need all that stuff. He said "don't waste my time" and then hung up on me. :confused:

douchebag.

I just installed the MSD ignition with boost retard. I have advanced my timing a little bit, retarded boost, and want to use the knock sensor both for safety and tuning. BUT, if no one makes an accurate-n-reliable one, then I guess I'm just playing with a grenade.

spence88mph 04-23-2008 03:30 PM

been wondering the sme thing, I have seen sensors that bolt onto the block but I wonder if they will work the same way with separate cylinders.

John at J&S 04-23-2008 03:54 PM

Douche bag here. Sorry I lost my temper with you this afternoon but I couldn't take it.

I just wrapped up the new design this morning, then you call asking if my system can reliably detect knock in all cylinders on an aircooled engine.

I say I'm not really the guy to ask since it's my design, then explain an aircooled isn't as noisy as most think, and relate a story, etc, then I tell you about the features in my new design.

You say you just installed a boost retard and all you want is a simple system to say it's knocking. I make a very fine closed loop system for not much more than you paid for your boost retard ignition and you want a knock LED. Sorry, but I lost it.

As for whether it works or not, Steve at Rennsport posted this a while back:
Quote:

Originally Posted by Steve@Rennsport
Hi Bill:

LOL,..We recently finished a 993 TT engine (627 HP) with Motec M600 interfaced to J&S controlled knock sensors for active feedback and timing control, just like stock.

In this case, three engine maps are selectable with different boost levels; street gas, race gas and smog compliance.

Works great.

mppickett 04-23-2008 04:18 PM

So, I have no horse in this race (no knock control), but I can attest for the widespread respect that J&S has in the non-Porsche boost community. If I were looking for sensitive active control they would be a serious contender for me.

dsiegel360 04-23-2008 06:12 PM

Wow John, that's some serious radar. Your apology is accepted. I am a bit of a newbie who has spent 3x the money I intended on my engine and 400x the amount of time intended. I know little about this subject, so I am sorry that I can't ask direct and intelligent questions on the topic.

As for your current creation, it sounds fantastic......yet, while you described it I felt another 1000-2000 bucks being sucked from my pocket (not that you told me the price). It sounds far more sophisticated thus I assume more expensive than your past knock sensor creations...just a guess.

Several people have mentioned that the general noise of an air cooled engine makes knock sensors inaccurate. I don't know your history, thus I could not know whether you spend most of your time working with liquid cooled engines.

I've also heard it said that knock at different RPM's creates ping in different sound frequencies. Perhaps some knock detectors only search for sounds at one end of that range. I wanted some details on if and how you address this. Just gathering info.

Pelicanheads,
Is a knock sensor a tried and true insurance policy on our expensive motors?

John at J&S 04-23-2008 07:14 PM

Doug: There are a few that have posted about the system. I'll dig up their posts after a bit.

Can't remember how I got this pic, but it must have been from an engine builder in Daytona Beach who installed several of our systems.

This was probably from '96 or so. I think the customer raced it in Panama.

http://forums.pelicanparts.com/uploa...1209002800.jpg

les_garten 04-24-2008 01:47 AM

When I built my motor I asked about knock sensors from the Company selling me my ECU, harness etc. The knock sensors will sense knock in an air-cooled noisy Porsche engine. I was told that the issue is that they "falsely" sense knock when it is not there from the cacophony of noise in a Porsche engine. Basically a false Positive. So you are a retard much more than you would like. I wold love to have one that was accurate and sensed knock when it needed to and didn't sense it when it was no there.

equality72521 04-24-2008 04:28 AM

Quote:

Originally Posted by les_garten (Post 3904852)
So you are a retard much more than you would like.

:D

Do you mean "So you retard much more than you would like."? :)

JBL930 04-24-2008 04:40 AM

993tt's have knock sensing right? If it can be done on the 993tt then it can be done on the 930. I've read that it's all about where they are positioned, not that it isn't possible

les_garten 04-24-2008 09:15 AM

Quote:

Originally Posted by equality72521 (Post 3904912)
:D

Do you mean "So you retard much more than you would like."? :)

"Stupid is as Stupid does" -- F. Gump ca.1994

les_garten 04-24-2008 09:22 AM

Quote:

Originally Posted by JBL930 (Post 3904918)
993tt's have knock sensing right? If it can be done on the 993tt then it can be done on the 930. I've read that it's all about where they are positioned, not that it isn't possible

Here's my scenario, I asked a few companies who specialize in Porsche 930 tuning, and they say, sure they are available but...

I got 35K in Engine Parts, I would love to put one on mine if I was convinced it wouldn't "false" on piston slap, etc.

A930Rocket 04-24-2008 10:17 AM

I've heard the 930 engine makes "too much noise" as well to use a knock sensor RELIABLY. Not sure if its the chain and ramps, etc that do it?

John at J&S 04-24-2008 10:25 AM

http://forums.pelicanparts.com/911-engine-rebuilding-forum/222245-how-do-i-safely-monitor-my-motor-post1923399.html#post1923399

les_garten 04-24-2008 12:14 PM

Quote:

Originally Posted by John at J&S (Post 3905507)

Hi,
No offense, but you SELL knock mitigation equipment. I read this thread you referenced. No proof of anything here. I'm sure your system can stop knock(well sorta sure), the question is does it stop performance? There are a lot of high end Porsche performance shops out there. Which one refuses to sell you a Hi Po engine without a knock sensor?

If I sold you a 65K motor and a knock sensor worked well on it, I would force you to buy it to protect your engine and my business.

Contrary to this, the Tuner shops I have spoken with have basically told me to forget it! It will kill performance. The fact that a guy tore his motor down and all his rings and lands look good doesn't really prove anything. Let's see his "Knock log" for the last 10,000 miles. Let's put his motor on a dyno and watch the knock sensor while he produces power, the engine is loaded and we mod the timing curve.

For the cost of a knock sensor, who wouldn't want one, comparatively speaking, they are DIRT CHEAP!! There's lots of modified cars here on this forum, the knock sensors are for all practical purposes ABSENT.

John,
You got a SIGNIFICANT amount of Porsche data and testimonials, and dyno time with 930's, I'd love to see it. i THINK WE ALL WOULD. Prove to me your system detects "positive's" properly and does not make "false" detections, and you've sold me one and most likely a lot of others. I basically would like to see the scientific method employed here, not sales brochures.

The first time I pulled my motor apart, every compression ring was broken into uncountable pieces, all twelve.

To coin a phrase...
Sho me sumpin' Mista!

John at J&S 04-24-2008 03:14 PM

Les:

The thread I linked to doesn't prove anything, but the post by 350HP930 should score us a few points.

http://forums.pelicanparts.com/1658863-post72.html

I don't know him, so he probably bought it from the engine builder in Daytona we used to sell to.

I checked his profile, and he hasn't been on the forum in a couple of years.

John

beepbeep 04-24-2008 03:35 PM

Hmm...IMHO, the only bombproof way if detecting the knock w/o running into false positives is by using ion-sensing (thus measuring ionization current over plug gap after each combustion).

Those acoustic I came in contact with certainly work, but are often tuned to go "safe" as revs climb and pull timing/boost as they go deaf att higher revs. They usually do their stuff at middle revs where BMEP/torque is highest.

A knowledgeable and expirienced gentleman gave me a very usable hint when it comes to detecting knock on dyno (while mapping etc.) He used brake line tubing that he connected directly on the block on one side and to some sort of megaphone on the other. He claimed he could hear a single knock on this contraption. :)

les_garten 04-24-2008 03:39 PM

Quote:

Originally Posted by John at J&S (Post 3906069)
Les:

The thread I linked to doesn't prove anything, but the post by 350HP930 should score us a few points.

http://forums.pelicanparts.com/1658863-post72.html

I don't know him, so he probably bought it from the engine builder in Daytona we used to sell to.

I checked his profile, and he hasn't been on the forum in a couple of years.

John

Hi John,
I'm not making my point obviously. I have no doubt that "most" if not all these knock sensors suppress knock. The issue is that they suppress performance. The fact that everything was fine when he pulls his motor down means nothing other than anecdotal evidence. That is, his engine didn't blow up. Why??? Maybe he only ran 20 degrees of timing with 103 Race gas all the time?? Maybe he never drives above 4200 RPM? Kinda doubt that but who knows.

The issue with the knock sensors is not that they can't sense knock, it is that they sense it when it is not there, and pull timing(Performance) out.

From your response I can only conclude that there is no empirical evidence of the efficiency of your knock sensor in relation to Porsche 930 motors??

John at J&S 04-24-2008 03:43 PM

I also quoted Rennsport in post #3 above.

les_garten 04-24-2008 04:07 PM

Quote:

Originally Posted by beepbeep (Post 3906098)
Hmm...IMHO, the only bombproof way if detecting the knock w/o running into false positives is by using ion-sensing (thus measuring ionization current over plug gap after each combustion).

Those acoustic I came in contact with certainly work, but are often tuned to go "safe" as revs climb and pull timing/boost as they go deaf att higher revs. They usually do their stuff at middle revs where BMEP/torque is highest.

A knowledgeable and expirienced gentleman gave me a very usable hint when it comes to detecting knock on dyno (while mapping etc.) He used brake line tubing that he connected directly on the block on one side and to some sort of megaphone on the other. He claimed he could hear a single knock on this contraption. :)

Ehhhhh? Whatdya say Sonny!!

Jim2 04-24-2008 05:15 PM

MSD knock alert, look it up on the web. It's just an indicator tool, no integration ability or feedback.


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