Rev limiter?

[Mucus72]

I had the pleasure of taking Richard Price for a few laps around Donington a month or so back. I asked him his opinion on where I could improve my performance and he suggested that I needed to rev the car out to its limiter. I had been revving up to circa 7200 before changing up and he said that I needed to be more aggressive and hit the limiter. 

So this weekend at Castle Combe I threw away my mechanical sympathy and went for it. Bear in mind my rev counter has a piece of red tape stuck on it between 7200 and 7500. I revved up to 8000, which is where the dial ends but still I didn't hit a limiter. 

Does anyone one know if the limiter can be removed from a MEMS3 Supersport ECU on a K series?

I'm fearful of expiring in an explosion....

[revilla]

The only person I know who could do that would be Mark Stacey at Z&F ... but I don't believe he would! 8000rpm on a mostly standard engine sounds like it is asking for bent valves or a piston failure so be very careful (unless you know for sure you have forged pistons and uprated valve springs that can take it). Mark would certainly be able to examine to ECU to determine what the limit is currently set to. I believe 7600 is about the highest that DVA would recommend on a VVC 160 bottom end and around 7300 on a standard K.

 

I know Mankee's engine bent all its exhaust valves at 8200 on a short rolling road run.

[simon_h]

Might just be a rev counter engine revs mismatch. My SS 1.6 doesn't read exactly what the engine is doing.

[LazerBrain]

It would be useful to put a set of shift lights on the car, set them to come on at 3000rpm and compare that against 3000rpm on the tacho. You can then repeat at 6000rpm to see if the difference has increased.

[Richard Price]

Marcus,

My tacho needle often appears to indicate very close to 8000rpm, but my datalogger (which I'm more inclined to believe) confirms my revs are limited to 7600rpm.

[Mucus72]

Thanks for the comments. I'm going to borrow a data logger before the next track day and work out what's really going on - thanks for this Andrew R ;) I will report back...

[Roadsport06]

Get yourself an ELM327 and torque on an android device and it will clear fault codes. You can also plot revs, coolant temps etc. The ELM327 was from eBay for about £5 and Torque was brought from Google apps for about £3. It paid for itself a week after as it diagnosed a MAFS issue on an Audi TT 3.2 VR6.

[Jonathan Kay]

What's the nature of the signal to the tachometer: is it a voltage or a pulse rate?

Thanks

Jonathan

[Richard Price]

What's the nature of the signal to the tachometer: is it a voltage or a pulse rate?

The signal from the ECU for the tacho is pulses

[Jonathan Kay]

Thanks.

What's the easiest accurate way of testing a signal like that?

Jonathan

[Mucus72]

Just an update regarding my rev limiter.

Andrew Revill and I ran tests at each 1000 rev increment using an OBD reader, whilst maintaining constant revs so that the reader would record a fairly stable result set. The Rev counter is reading circa 200-400 revs higher and is further out the further up the Rev range. We recorded somewhere around 7,600 at just under 8,000 on the dial and did not want to go any further for fear of serious damage. I still didn't hit any rev limiter!

My car is a SuperSport 1.6 K DVA fettled, circa 150 BHP unit. I've asked the previous owner to help me understand if its had any bottom end upgrades. I know top end work has been carried out, but unsure beyond that.

 

[Mankee]

Peer down the spark plug holes or get a borescope to see if you can tell what sort of pistons are lurking in there.

[revilla]

So Mankee ... what does a forged piston look like?

 

[Mankee]

Grut old cutouts for the valves can be a good giveaway.

Omegas (from the K-Bible, aka DVA's website):
http://www.s262612653.websitehome.co.uk/kengine/torpstn1.jpg

82mm Pistals:
https://www.dropbox.com/s/ixm5bbimolioj3c/SDC10416.JPG?dl=0

82.5mm Wisecos:
http://images60.fotki.com/v224/photos/8/42688/8170069/photo1-vi.jpg

[Richard Price]

Marcus,

You have Blatmail.

Unless someone else have worked on the engine since I did, you don't have forged pistons.

 

[nickh7]

My 1.6 SS EU2 hits its rev limiter with ease at an indicated 7,400 .  I have my change up light set at 7000 for the first red second light at 7200 (maxium power)

 

[Paul Deslandes]

I suspect that the standard rev counter, although electronically counting ignition pulses, uses an analogue instrument to display revs.  Your statement that the error increases in proportion to the revs would bear this out.  It may be possible to recalibrate the meter if there's an internal adjustment pot or select-on-test fixed resistor

Better quality instruments, e.g. Stack, use stepper motor instruments so the reading will be more accurate.

Paul

[TomB]

So whats a suitable rev limit for a standard bottom end 1.8k?  Ahead of the Oulton track day later in the month, Ive programmed the Emerald at soft cut off at 6800 and hard at 7000 to avoid getting too excited and taking it too high. A few hundred RPM at the top end wont make any difference Id have thought?  Does this sound about right? 

[Mankee]

For my first 1.8 engine, which was basically a boggo standard engine rated at 150bhp/133lbft @ 6430/5072rpm, I used shift light at 7000rpm, soft-cut at 7400rpm and hard-cut at 7600rpm. It was plenty safe enough and there was no point in revving any harder as all the good work was done by 7000rpm.

[TomB]

I've played again tonight. Engine is peak power at 6300, so I've set the lights to come on between 5500 to 6800, flashing at 7000. The Emerald is set at soft cut at 7100 and hard at 7200. Sounds reasonable?