unijacko67
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| posted on 23/11/13 at 11:55 AM |
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Knock sensor, how do they work ? S2000
I'm not sure where the sensor or sensors are on the s2000, but would like to know what they do and how? also could a knock sensor limit the
overall top speed (gearbox output shaft/prop) if bad vibes are being detected.
The reason for this question is my car seems to hit the wall prematurely in top gear so to speak at exactly the same speed give or take 1mph on any
run up hill or down. It revs to 8500rpm in all gears, but I've noticed in top gear it stops at around 7000rpm even if going down hill, its not a
gearing or lack of power issue as the engine pulls like hell until then and then the engine note doesn't sound quite as crisp.
The only thing I can think is that the prop and final drive will be spinning at the highest rpm in top and wonder whether any slight unbalance could
trigger this to happen.
I have a new prop on the way, but that's another story  enough said, as my origional prop and still on the car has cv joint at front and uj
at the rear.
I've looked on internet for answers, but trust you lot will deliver the correct info. Thanks in advance.
http://www.kittenkitcar.co.uk
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ianm67
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| posted on 23/11/13 at 12:15 PM |
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I thought that knock sensors detected pre-ignition or pinking rather than mechanical noise? It is essentially a microphone.... According to Google
images, it is located in the block above the water rail and is above and to the left of the oil pressure sensor....
[Edited on 23/11/13 by ianm67]
Always biting off more than I can chew.....
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unijacko67
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| posted on 23/11/13 at 12:21 PM |
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Ok, that makes seance, maybe other sensors then, crank?
Sorry crank sensors, i'm not calling anyone.
http://www.kittenkitcar.co.uk
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bi22le
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| posted on 23/11/13 at 12:21 PM |
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I would of thought it would be more turned then that.
Its in the engine block. Pleanty of engine noise to overpower anything coming from the diff.
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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britishtrident
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| posted on 23/11/13 at 12:36 PM |
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The knock frequency is filtered out from the background noise by digital signal processing.
On many cars they are bolted on to the inlet manifold, on others the crankcase.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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snapper
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| posted on 23/11/13 at 12:39 PM |
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Disconnect and try same driving profile
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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MikeRJ
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| posted on 23/11/13 at 12:46 PM |
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If you are getting bad vibration from the propshaft then attempting to achieve top speed doesn't seem like a clever idea.
If your maximum speed is around 180km/h (112mph ) then you have a Japanese import car which have speed limiters fitted from the factory.
[Edited on 23/11/13 by MikeRJ]
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adithorp
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| posted on 23/11/13 at 12:56 PM |
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quote:
Originally posted by MikeRJ
If you are getting bad vibration from the propshaft then attempting to achieve top speed doesn't seem like a clever idea.
If your maximum speed is around 180km/h (115mph ) then you have a Japanese import car which have speed limiters fitted from the factory.
I was going to suggest maybe it had a max speed limiter in the ECU. I doubt you'd get the same result at the same speed under different loads
(up/down hill) caused by the knock sensor.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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britishtrident
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| posted on 23/11/13 at 02:10 PM |
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It is quite common for the edu to monitor the vehicle speed sensor output and trigger the limiter to govern top speed
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Oddified
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| posted on 23/11/13 at 04:01 PM |
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As above, most likely to be a speed limiter in the ecu which depending on how/where it's being picked up from will probably also be effected by
the diff ratio and tyre/wheel size.
A quick google shows that they do have speed limiters, and the actual limit depends on the original cars market place.
Ian
[Edited on 23/11/13 by Oddified]
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unijacko67
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| posted on 23/11/13 at 04:21 PM |
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Thanks for the suggestions, the prop isn't noisy by the way. I wonder if it is a speed limiter as I'm sure when I first had it on the road
(same diff and wheel size as now) it hit the rev limiter in top (or did I just presume it had as I can't remember watching the dash) , but since
I have fitted a yellow jacket speedo healer to get the digital dash to read correctly and wonder if that's the issue. I'll pop the obd on
it tomorrow and see if I've any fault codes.
The other thing I've done is wrap the exhaust manifold as the heat was causing the engine mounting rubber to fail.
[Edited on 23/11/13 by unijacko67]
http://www.kittenkitcar.co.uk
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unijacko67
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| posted on 23/11/13 at 04:39 PM |
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Just re-read some of the suggestions and its not a jap import and its the 2007 motor.
http://www.kittenkitcar.co.uk
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unijacko67
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| posted on 23/11/13 at 05:44 PM |
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quote:
Originally posted by adithorp
quote:
Originally posted by MikeRJ
If you are getting bad vibration from the propshaft then attempting to achieve top speed doesn't seem like a clever idea.
If your maximum speed is around 180km/h (115mph ) then you have a Japanese import car which have speed limiters fitted from the factory.
I was going to suggest maybe it had a max speed limiter in the ECU. I doubt you'd get the same result at the same speed under different loads
(up/down hill) caused by the knock sensor.
Thanks Adi, its topping out at around 120mph 7000 rpm, 4.1 diff same as s2000, but on 15" 50' profile tyres. standard uk s2000 are good
for around 150mph so I would have thought it should rev out at around 130mph ish. Standard car did have big wheels though so could well be a limiter.
Hits just under 9000rpm in all other gears.
http://www.kittenkitcar.co.uk
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adithorp
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| posted on 23/11/13 at 06:42 PM |
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If your speedo corrector is on the signal from the gearbox to ECU then the ECU will be limiting based on that signal. Could you fit it between ECU and
dash instead?
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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daniel mason
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| posted on 23/11/13 at 06:58 PM |
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if i remember,the speedo healer comes with a wiring diagram which i printed off for andrew. its for the s2000 guys who fit shorter ratio back axles so
i presume its wired up as per the instructions knowing andrew!
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coyoteboy
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| posted on 23/11/13 at 10:25 PM |
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FWIW the knock frequency is usually filtered as BT says, but if you have a mechanical noise which has a component in the same frequency range (usually
4-7KHz) it could well trigger it in a finely tuned OEM system which never expected to have DIY hardware bolted up.
you might think something isn't noisy, but try sticking a screwdriver on the block and the handle to your ear while revving it and you'll
understand more what the sensor has to deal with.
When I did my first batch of tuning of my car I hooked the sensor up to my stereo's amplifier and used the EQ to filter out a LOT of mech noise
while listening for det, at high RPM it's virtually impossible to separate light det from mech noise.
[Edited on 23/11/13 by coyoteboy]
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unijacko67
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| posted on 24/11/13 at 12:38 AM |
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Its fitted at the gearbox end which then goes to the dash or ecu? not sure, so might need to disconnect it and have a run out. Cheers for all the
advice.
http://www.kittenkitcar.co.uk
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chris mason
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| posted on 24/11/13 at 09:32 AM |
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It's 8 years now since i built my S2000 Indy, I was running the stock gearbox/diff and 195/50/15 tyres, iirc it was geared for 168mph at 9000rpm
in 6th, roughly 18.7mph per 1000 rpm.
Based on the above at 7000rpm you should be doing around 130mph
I drove mine at a speeds higher than this, but on an aftermarket ecu, at a guess i would assume 7000rpm/6th gear in an S2000 would roughly equate to
its quoted top speed, so maybe there is a limiter preset in the ecu for this even on Uk cars.
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unijacko67
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| posted on 24/11/13 at 12:07 PM |
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Thanks Chris, I used a sat nav to set the speedo healer at around 30 mph so it might well be out further up the range. So as you say the
engine/box/ecu may think it's hit a speed limiter.
Coyoteboy, could my drive train if not 100% balanced be making the sensors limit the engine revs. Cheers.
[Edited on 24/11/13 by unijacko67]
http://www.kittenkitcar.co.uk
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unijacko67
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| posted on 4/12/13 at 10:29 PM |
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Just a quick update, there doesn't appear to be a top speed limiter on the s2000 as I've done a test tonight. I removed the prop, warmed
up the engine then put it into 6th gear and sure enough it revved right up to the limiter. As Chris said my car seems to top out at around 7000rpm in
top which could be nearer130mph as my dash could be a bit out. I now know the management ECU/speed sensor will allow more revs so I'm happy that
that's about my lot on short blasts. Also I spoke to Andy Larton today from Larton auto Developments and he suggested it could be all down to
aerodynamics or lack of aerodynamics as my car was originally built to do about 40mph on a good day. Cheers.
http://www.kittenkitcar.co.uk
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froggy
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| posted on 5/12/13 at 08:42 AM |
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When I ran twin bike engines I sort of hit a brick wall at 120mph with around 240hp. Don't know about yours but my wipers come off the screen at
120+
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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unijacko67
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| posted on 5/12/13 at 01:52 PM |
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My wipers are off a newer car so quite a lot more substantial than the standard kitten blades and they behave themselves, but the car defiantly gets
to a speed that it doesn't want to go beyond dispite the donar car being heavy and good for 150mph. Don't get me wrong 120mph is more than
enough for my ability, but if the shape of the car is creating a situation behind the car that's holding it back these same effects will also be
holding back the car at 80mph.
I will see if I can find the wind tunnel reports for the reliant kitten factory 1975 on Google. Lol
http://www.kittenkitcar.co.uk
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froggy
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| posted on 5/12/13 at 04:03 PM |
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What are the wipers off ?
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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unijacko67
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| posted on 5/12/13 at 04:30 PM |
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I fitted the s2000 motor and mechanism, but had to shorten bits, fitted the screen then to my horror realised the s2000 wiper arm hit the screen so a
quick trip down the scrap yard to find a pair of wiper's that had the same spline (seemed fairly universal) but I needed them to pivot almost
straight away as the Kitten screen is quite close to the wiper spline, then I had to shorten them and re weld. Bit of a pain but got there in the end.
Not sure what car I salvaged them from sorry.
http://www.kittenkitcar.co.uk
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02GF74
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| posted on 5/12/13 at 08:16 PM |
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Cv and uj on a prop is that alkowed?
I understood uj were phitted 90 degree to each other to cancel out variation in rotational speed
Not sure if that can cause vibtlration.
Presumably the prop has been bakanced
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