EFI University

[NickG]

Last year I purchased a used Mustang MD-250 portable dyno. It had come with 2 RPM pickups: the standard inductive and the optional optical pickup, both of which interfaced to the dyno software via a BNC A-B switch feeding an ATI Smarttach unit. The dyno always worked well, but the inductive RPM pickup left much to be desired.

Recently the inductive pickup stopped working. After some debugging I found that the ceramic and coil in the plastic pickup itself were fine, but the wire connecting the pickup to the A/B switch was at fault. I purchased some 16 gauge 110v AC wire (zip cord) to replace the faulty wiring. The inductive pickup was back in business. And wouldn't you know, the readings were MUCH more stable now. Before I had to constantly fiddle with the trigger threshold voltage to get a reading, and the reading would also bounce around too. Now, it's perfectly stable and works with the default inductive pickup settings. So if you're using the inductive pickup and have troublesome RPM readings, you might want to check out the cable.

Another trick I found in doing all this relates to getting the RPM signal from BMWs (which is what I primarily dyno). BMW outputs an RPM signal from the ECU on a dedicated wire (one pulse for every cylinder firing, hence, the signal's frequency x 20 = RPM). This signal is available on pin #1 of the 20-pin diagnostic port in the engine compartment, or pin #9 on the OBD2 port. I've made a harness that connects to either of these 2 ports (not all cars have both) and the A/B switch. By programming the ATI Smarttach accordingly (via it's front panel or the PowerdynePC software), it will convert this frequency signal into an RPM reading. With the RPM signal hardwired to the ATI, there's much less chance of noise and a bad reading. This method has also proven to work well for me and provide a stable RPM signal.

[kickerzx]

Nice tips Nick. Dont have a Mustang, but this is stuff worth knowing.

[TuRBo-Shark]

Thanks for the tips!

[brianko]

And don't forget that if the inductive pickup fails, you can always run with the calibrated roll speed for fixed-gear pulls.

The inductive pickups are very prone to damage, especially if they get banged around. I'm on my second in 3 years, and have pretty much resorted to either running with calibrated roll speed or from the OBD-2 signal.

Thanks for sharing about the shortcomings of the optical pickup. I was planning on buying one, but have now changed my mind.

Also, be careful when using the inductive pickup on multistrike systems. You can modify the SmartTach to correctly count the pulses, but if you're working on a poorly grounded system (and there are many out there who simply don't know how to properly ground their new ignition system), spikes in the pickup lead will lock up the DAQ board, requiring a shutdown of the computer to reset it.
_________________
ExaTorq Tuning and Performance (Dallas, TX)
Mustang MD-250 2WD dyno

[bbucalo]

Hi Guys,
There are other alternitives to the pickups used on the Mustang dynos. I used to work for ATI, the manufacturer of the SmartTach and have since left to start my own business. We had always had conversations with the management about the accuracy of the inductive pickups and I tried to convince them to re-design the unit, no success.
I have designed our own pickup to replace the one they supply and it is a major improvement, much smaller pickup for clamping on the wire, more versatile, and can also be used on the fuel injector feed wires for a second option from the ignition. It is a direct pin-to-pin cable connection to the SmartTach unit as the original.
We also have a smaller and more reliable optical unit for diesel engines and a replacement for the SmartTach if there is a need to replace it.
In my experience there is no need for a "High Level" pickup on the secondary ignition,( plug wires) as if you have secondary, you have Primary which is more reliable to sense.
Take a look if your interested or call us for more information, http://www.testcellservice.com
BTW: I am always open to help with any questions you may have about the SmartTach units.

[TuRBo-Shark]

Cam you pm a price?thanks!

[10sec_rx7]

any way you can interface that to a DD dyno?

[bbucalo]

Yes, these devices can be used on any dyno system. The inductive pickup, (RS1000) has a pulse output that can be configured to be many different levels, including an open collector type, the standard is a TTL level output.
If the dyno data acq. system has a frequency counter input it can be wired directly to it. The system will be responsible for the scaling of pulses per rev to rpm value.
The other device, RS2000, is a programmable freq-to-voltage unit that will scale the PPR into a RPM value for dislay and output a 0-10vdc analog voltage that represents 0-10,000 rpm. This can be connected to a analog input of the dyno system for reading RPM.
The RS2000 unit has options for scaling that will allow the used of any count of pulses so the pickup can be placed on a single primary coil feed wire or a fuel injector feed wire for 1 pulse per rev.
If you want more accuracy it can be placed on the main feed wire for the coil-pack and get a signal for every plug fired per rev. Ex: on a 6cly engine it would read 6 ppr. The device is universal and can also be used with an optical pickup for diesel engines. Note, if the diesel engine has electronic fuel injection then the inductive pickup will work just fine on a injector feed wire.
Bottom line is that it will work for any dyno, just depends on the input options of the system.

Brian

[Power-Tripp]

[bbucalo]

Hi Power-Trip,
There is a scaling option in the setup menu for range adjustment, it can be set as a divider for the calculations. This means that the range set to 2 will setup the device to have a range of 0 - 20,000 rpm with an output of 0-10vdc. It can use a maximum frequency of 200kHz, so it is possible with the correct ppr setting to measure up to 50,000 rpm.


Brian
_________________
TestCell Service,llc
Service and Support for your Dyno Test Cell !
White Lake, Mi.

[10sec_rx7]

tell us the price!

[bbucalo]

I would rather not post the prices on the board here but if you are interested just give us a call or drop me an email.
Brian@testcellservice.com

I received a call from DD dyno yesterday inquiring about the interface to their system and we are talking.
_________________
TestCell Service,llc
Service and Support for your Dyno Test Cell !
White Lake, Mi.

[dkGoodrich dot com]

Wish my mustang dyno had a rpm pickup.

ATI unit is just too damn expensive and I am afraid if I bought it there would be no help in getting it to work properly.
_________________
http://www.dkGoodrich.com
KY's Fastest Honda's, Acura's & Subaru's
Dyno cell with a 2010 Mustang Load Dyno.

[bbucalo]

Hi DK,
I hear you, that is why I designed my system so it is reliable and there is support when you need it. I also support the ATI SmartTach and TS1 for customers, we are a authorized factory rep for ATI also.

PS: Our system is much cheaper than the ATI system.
_________________
TestCell Service,llc
Service and Support for your Dyno Test Cell !
White Lake, Mi.

[Tomak]

Both my mustang old MD250 and my current DD unit use the Fluke RPM80 rpm inductive pick-up.

I have found that with age, these pick-ups start to give a poor signal, I tend to change them at least once a year, or as I burn them on headers

In the case of the DD, it just plugs in. In the case of my old MD250 with the 16bit "B97" rpm board, I had to rewire the pick-up, but it saved me $200 over buying MD's version.

The DD (analog) is trouble free, and I used the inductive 90% of the time, and the direct tap when the vehicle has an easily accessible tach output wire. Only issue I have is if the pick-up is placed around the wire in the wrong direction.
_________________
www.Dynomotive.ca
AEM Factory Trained, Accel EMIC, Haltech Trained, Advanced GM EFI, Diablo CMR Mopar Dealer, SCT TUner - Viper/SRT10, Delta Force Dealer.
Analog DD 450
Mustang MD250 - gone but not forgotten.