Tom Cloutier

Marc Thomas and I have been using one of John Speake's Shark Tuners to tune Chebbys. Actually we've tuned a 500+ RWHP stroker, a more modest 410 RWHP stroker and my very neglected 928 with the Scavenger exhaust system. My car has barely been driven for the past year while my wife recovered from a stroke she claims was caused by my dyno. Anyway several problems surfaced very quickly: unhappy flappy, dead temp sensor on radiator (thanks Susan!) causing fans to not work, alternator charging at 16+ V, etc.

We accomplished quite a nice tuning job on my car with no flappy. Get to do it all over again now that it is fixed. The 500+ big bopper tuned up real nicely. It idles in spite of the B1 cams, but then who would be idling this baby anyway? Marc and I did some freeway tuning at about 150mph which velocity was achieved in very short order and before I knew it we were closing on some poor law abiding citizen at about 90mph!

The 410hp stroker proved to be a nightmare from beyond hell. We typically pull the LH out, remove the metal cover, plug in John's ribbon cable, and tune away. There's a clue there guys. The 410, however, would stall nearly everytime we pulled it out of the shop and I could almost never get it out of the parking lot. Marc and I found while doing low speed laps in the lot that the engine died regularly at a specific place in the lot, slightly downhill and turning left. The engine would usually fail to restart for about 30 min. Millions of clues!

We tried nearly everything, even consulted the manuals a time or two! We replaced relays, thought we had found a wiring harness problem, pulled the fuse/relay board out, checked the air in the tires, looked for potatoes in the tailpipe... Each time we upfixed der Gott im Himmel Porsche I'd go out for a drive and the car would run great, except when it died and refused to restart. I'd come back to the shop thinking it had been fixed and later would start off on a tuning drive. Of course the engine died.

The Shark Tuner has a very nifty system monitoring screen and I found through watching this screen and logging data that the injector pulse width would drop to zero when the engine quit. The car also had a nasty lurch at about 1200 rpm. The PW also dropped to 0 at each of these lurches. I later realized that the LH was not sending any signal when the engine quit as evidenced by all the monitors disappearing from the laptop screen.

Anybody guessed the problem yet? After pulling the car out of the shop and the engine doing its play dead trick, I reached down to wriggle the ribbon cable on the LH. The juice came back! When I pulled my hand away the juice went away again. Come on you guys--there are so many clues here you'll be ashamed when I tell you the cause. I started to grab the ribbon cable and squeeze its little neck until the connector popped off, but before I even touched it, the juice reappeared! Seemingly I had done nothing. What the? I reached out my hand over the LH several more times and each time John's monitor screen came back to life. Oh and the engine would restart.

The car was delivered to its owner last Friday and I presume it continues to run well and the owner is enjoying an extra 35RWHP (if memory serves). The Shark Tuner is a very useful instrument. Finally we have a way to tune the LH computer directly (just burn a new eprom after tuning). No more piggyback devices. My LH used to override all the adjustments I had affected with my Dastek. My Dynapack dyno is an excellent complement to the Tuner. I can set a load and vary the rpm or set an RPM and vary the load and just tune away. The autotune feature on the Tuner is a very useful means of getting the mixture into the right ballpark. Great job, John!

BTW, I spent most of 2 weeks diagnosing the aforementioned problem. Anyone who guesses the correct source can buy me a much needed beer!

Cheers,

Tom Cloutier

lorenolson888

Hi Tom,

Loose Cable?

LO

Tom Cloutier

Hi Loren,

Nope, but you can buy me a beer anyway! This is the sort of problem that one could easily spend years searching for and never find it. You really have to get into the zone for this one.

Cheers,

Tom Cloutier

John Speake

Hi Tom,
I was pleased to hear that this strange problem was successfully fixed ! Certainly an interesting cause...

Thanks for the kind comments about the ST. That makes all the hard work for me and Niklas worth while.

The first issue of the EZK version of the ST will be out for evaluation shortly....

sweanders

Hi Tom! Could it be a bad ground when the cover was removed that was the problem? Maybe the cable touched or lost contact with a ground source when it moved?

OT: Say hi to Marsha from me! How is she doing?

Thaddeus

RF interference of some sort, which your hand blocked?

AO

It's got to be a grounding issue. I'm guessing that the metal cover supplies ground to the LH and when that was removed, the grounding was... um... compromised .

Normy

Loose cable at the device?

When you leaned over, the ST's battery would fall out and the system would lose power?

N?

SwayBar

Good job John; three cheers to John Speake!

What was the resulting rwhp numbers?

Do you know how much bigger these cams are than GT cams? Do you think these cams would be too big for a stock-block GT track/street car? Do you have a guess-timate on the rwhp gain for the mentioned combo which puts out 320 rwhp (..headers, Ott-X, dual Magnaflows, rising rate fuel pressure regulator, cowl-induction).

Does anyone have a before and after dyno-sheet showing the power curve of the B1's?

Inside the shop, the car was shielded from the sun. Outside, driving the car where a position causes the car to be in direct sunlight where it can hit the exposed computer-internals and cause interference, stalling the engine. The 30 minutes between restarts was because that's how long it took the sun to move 'out of the way' of the computer's interference zone.


Tom, I hope your wife is well on her way to recovery.

Joe '87 S4

You mentioned you motioned around it with your hand so I'm guessing you used the force?

James-man

EMFs.

But what is the source? Solution is shielding or relocating the offensive source.

Garth S

Human hand capacitance effects are reasonably common, as one waves a blood engorged mitt about in frustration ..... so the real question is what was influenced by your 'capacitor'?
I'm not aware of a specific shielded input to either the EZK or LH - and I'm too lazy to check at the moment . Anyway, it sounds as if one of the LH trigger leads is suspect; it is difficult to suspect anything inside the module as it is well shielded.
The only other external item that may be influenced is the PC inside the ignition monitoring relay - which can shut the works down quickly.

heinrich

It happened at the same spot while driving - left turn and slight elevation change. To me that is clearly mechanical.

As in bad cable, bad connector, bad prongs, or bad connection.

The idea of an electromagnetic influence causing temporary failure seems unlikely. If all you did was to move your hand through the air and hover it above the LH and this caused power to return, then one must deduce that either your movement was in some way mechanically manipulating a shorted or loose connection, ot there was an electromagnetic change to the unit ... again to me this seems very unlikely. I suppose if one had a cell phone near an exposed LH that might conceivably cause interference, but I have never heard of a cell phone affecting a computer motherboard. I have seen ringing cell phones affect a computer monitor.

ErnestSw

Loose prong.

James-man

"these are not the droids we are looking for"