Was with my buddy and his Mustang Cobra at a Mustang only performance shop. The dyno was available, so we threw my 87 NA on for a couple of quick pulls. Don't think the mechanics had ever seen a rotary (does this thing have spark plugs?) Try as they might, they couldn't find anything to to send a legitimate RPM signal to the Dynojet. Apparently not off the plug leads because of the firing pattern of a rotary. Probably a pretty simple solution, but we couldn't figure it out in the few minutes available.

By the way, consistent 130 RWHP on 2 pulls. Max RPM showed 14000 when we really went to 7000, and torgue maxxed at about 56 lbft which is obviously wrong.

 

You can splice into the yellow wire coming off the 4 prong connector on the Trailing coil. That will give you a tach signal if you have some kinda of pickup( signal based) that does not use an inductive clamp.

 

What a bunch of dumbasses...

Although all four spark plugs on a rotary does fire a very complicated pattern compared to piston engine, the DynoJet uses an inductive pick-up that should easily pick one of the leading spark plugs.

If you do a search on inductive timing guns and spark plug wires, there is a trick to put the inductive pick-up closer to the spark plug end for a cleaner signal.

We've NEVER had a problem with a DynoJet picking up the spark plug signal off the leading spark plugs.

You can also adjust the DynoJet program to "720" to adjust the RPM's to match the FC RPM's. They should've known how to do this.

You're basically readling 1/2 the RPM's, so your torque is basically 1/2 of what is should be.
"56lbft" = ~112 lb-ft of torque, is the proper torque readout you should've gotten.


-Ted

 

Ted

They didn't have a problem getting an induced pickup...they just couldn't get it to match the car's tach. What they ended up with was twice the reading the should have.

Figured I could double the torque # for an accurate reading, but 112 is well below the published # of 138, even though HP is a few above the 146 ( at least at a 15% discount for drive train loss, it works out to 153 at the crank) advertised. 26 lbft short seemed a little odd.

Whats this "720" setting on the Dnojet?

Gotta remeber these are Mustang only guys who have never had to fiddle with their dyno, 'cause the only get one brand of car!

Jim

 

112 lb-ft equals to about 132lb-ft with a 15% drivetrain loss.
Um, if published was 138, that's pretty close.


Yeah, it sounds like they only do V8's.

There's a menu which you can adjust the tach readout.
I remember we always change this value to "720", and we get the proper tach readout on the DynoJet.


-Ted

 

Sounds eerily like an amount of crank rotation, in degrees...

 

What about this:

The leading coil is wastesparked, meaning it only gets a signal to spark but doesn't differentiate between the two primary plugs, so they both fire on every signal.

The trailing coils are not wastesparked, it receives TWO signals, one to spark and one telling which plug to spark. That is why the coils LOOK very different.

Try using the inductive method on the trailing plug, no math needed.

 

Ted
Your right...I did the 15% math for Hp, but not for the torque.

Wayne
"720" does sound like "count every 2 rotations".

Rat
Thanks for the coil info.

So I'm tired of catching everyone on the twisty parts, and having them walk away on the straights. Figure the next step (short of finding a tll) is porting? Any estimate on what I could expect?

Jim