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.

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]

Ok, that makes seance, maybe other sensors then, crank?

Sorry crank sensors, i'm not calling anyone.

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.

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.

Disconnect and try same driving profile

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]

quote:

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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.

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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

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]

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]

Just re-read some of the suggestions and its not a jap import and its the 2007 motor.

quote:

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Originally posted by adithorp

quote:

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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.

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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.

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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?

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!

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]

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.

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.

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]

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.

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+

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

What are the wipers off ?

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.

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

CV & UJ on single prop was why I've had a new one made, although it incredibly quiet and no bad vibes it had little slip about 20mm, but the new uj-uj prop when first fitted smashed my gearbox as it was out of true. All re-done now so fingers crossed as I've not test run it yet.