tach signal

Ask questions relating specifically to the PicoDiagnostics NVH equipment and software here.
Post Reply
fisher
Newbie
Posts: 4
Joined: Tue Jan 20, 2015 1:51 pm

tach signal

Post by fisher » Fri Apr 03, 2020 11:24 pm

I had been told, when I called England from here in Seattle, U.S.A. that any tach signal would do in order to synch the NVH, however there was a max voltage, 12 or so...now I want to learn more. What for sure is the max voltage and if I had a cam signal that has an increase in amplitude once per 2nd revolution, how would I manage that with the NVH? I bought an ELM-327, blue tooth, and guess what? It came with no password for to boot it and asks for one when I try to use it.

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 817
Joined: Sun Aug 25, 2013 7:22 am

Re: tach signal

Post by Steve Smith » Tue Apr 07, 2020 8:54 am

Hello and thank you for the post, sorry for the late reply.

The maximum input voltage for an RPM signal using Channel D (NVH) is 20 V
This raises an issue when using an inductive sensor (for example, Crank) as your speed input, given the crank sensor voltage may well increase above 20 V as RPM increases

We can overcome this by using an attenuator assuming the output signal of the inductive crank sensor has sufficient voltage output at low engine speeds

Moving onto using the CAM sensor for your speed input, unfortunately the NVH software will not allow you to enter 0.5 pulses per revolution, which is what we have here (one pulse every 2 revolutions of the crankshaft)
Both items above have been raised with the software team (along with the ability to filter Channel D speed input) and will be implemented in future builds of NVH

The ELM device you are using may well function with a number of vehicles, I have however found the Bluetooth unit a little temperamental with connectivity to the laptop

The better options would be true J2534 or J1939 interfaces or perhaps an optical pickup here

I hope this helps and sorry for any confusion caused using the Channel D Speed input option

Take care……Steve

fisher
Newbie
Posts: 4
Joined: Tue Jan 20, 2015 1:51 pm

Re: tach signal

Post by fisher » Mon Apr 13, 2020 3:56 am

Thank you Mr.Smith.

fisher
Newbie
Posts: 4
Joined: Tue Jan 20, 2015 1:51 pm

Re: tach signal

Post by fisher » Tue May 19, 2020 4:22 am

Steve, I have more questions. I did think about the attenuator and realized a fuel injector could work if it were attenuated, however, doesn't the synch have to be a square wave signal? Also, if one uses the Mongoose ISO/CAN interface wont that only work on CAN vehicles?

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 817
Joined: Sun Aug 25, 2013 7:22 am

Re: tach signal

Post by Steve Smith » Tue May 19, 2020 8:11 am

Hello and thank you for the post

Using attenuation on an injector signal may work assuming we can pull the voltage down below 20 V, however we have the same issue as your Cam sensor with only one injection event every 2 crankshaft revolutions

Unfortunately we cannot enter 0.5 pulses per revolution with NVH (At present)

We also have to consider injection strategy as we have no injection events during over-run, bespoke injection pulses (depending on fuel/drivability strategy) and Stratified/Homogeneous injection timings which change depending on temperature, load and emission requirements

Using an injection event is therefore "challenging" to seamlessly determine engine speed.

Moving onto Mongoose, you connect to the vehicle via a number of protocols (not just CAN) using the Mongoose ISO/CAN II Device

These include:

J1850PWM
J1850VPW
ISO9141 (K-Line)
ISO15765 (11 bit & 250kbps, 11 bit & 500kbps, 29 bit & 250kbps, 29 bit & 500kbps)
ISO14230

I hope this helps, take care......Steve

matt07181986
Newbie
Posts: 8
Joined: Wed Mar 07, 2018 4:31 am

Re: tach signal

Post by matt07181986 » Tue May 19, 2020 5:42 pm

I am guessing the ELM device you have is a poor quality clone, there are so many out there. The clones have multiple connectivity issues due to quality and they clone an older version of the ELM327 chip. There is an ELM327 Identifier app available to test your device. I beta tested multiple ELM devices for Pico when the NVH software was being improved. I only had reasonable success with one device, the OBDLink MX. They have devices available that are compatible with Windows and are Bluetooth. They use a genuine ELM327 chip.

Here is the device that works with Windows and Android:
https://www.scantool.net/obdlink-mxbt/

The scan tool software is actually pretty nice for quick monitor and code checks too. If you use an Iphone I would suggest buying this one instead:
https://www.scantool.net/obdlink-mxp/

All of that being said, the best guarantee for connection is using a J-2534 device on cars and a RP-1210 device on trucks. You may be best off buying a Mongoose cable.

fisher
Newbie
Posts: 4
Joined: Tue Jan 20, 2015 1:51 pm

Re: tach signal

Post by fisher » Sun May 31, 2020 8:50 pm

I may have goofed. I went to Scantool.net and saw that the current MX was a bluetooth app, saw the MX+ and bought that; it is also bluetooth. It is not the MX however and wont load the signal we want to see. I am disappointed. I ought have bought the plain MX of course. I can imaginbe it wont work also, in this particular PC. I dont know. I do have a J2534 device, dont understand how it is supposed to work. I know it is used for flashing, how is it supposed to capture a tach signal? This unit is from a MAC Tools MDT-10 scantool; built by Bosch and is comparable to the BOSCH ADS - 625 tablet with J2534 or the OTC Evolve, also a BOSCH tool with J2534. I may be wrong; I believe Chrysler does not provide for any J2534 scantool app until 2008 or later, I am attempting to work on a 2002 model. Thank you for your patience.

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 817
Joined: Sun Aug 25, 2013 7:22 am

Re: tach signal

Post by Steve Smith » Tue Jun 02, 2020 1:23 pm

Hello and thank you for the feedback, sorry for the late reply.

From what I can see, the MAC MDT-10 and OTC Evolve utilize a dedicated head/display unit along with a customized OBD cable in which to communicate with the vehicle.

I can see there is some form of USB connectivity for the PC but I am not sure if this is for updating the device or printing etc.?

Assuming both these devices incorporate J2534 Pass Thru, I assume again this is via the support service for both these products?

The NVH software will attempt to access any J2534 adapter on your PC (in alphabetical order) however, these do not reside on your PC with the MAC or OTC devices

In order for these adapters to be visible (and accessible) by NVH there would need to be some form of “link” to use the J2534 adaption of these devices when connected to your PC.

The only possible way this could happen is if this is permitted by MAC or OTC and the relevant support instructions were available to do so.

We do use our Bosch KTS 590 device for acquiring engine and road speed (with NVH) via the OBD using the J2534 protocol / Pass Thru feature.

However, our Bosch software does reside on our PC’s and therefore access to the relevant driver and firmware within the correct directories (by NVH) is permitted.

For you to access the vehicle for engine and road speed via a J2534 Pass Thru device we recommend the Mongoose ISO/CANII device as once installed to the PC, the relevant driver and firmware are installed to suit

I hope this helps, take care……Steve

Post Reply