Does GLHS stage II calibration allows the engine to run 17psi...

[tryingbe]

I say no because ECU can't see anything above 14.7psi with a 2 bar map but


http://www.turbododge.com/forums/f4/...sket-p445.html

Let me try to explain the "basic history" of the Stage II logic module and I'm not suggesting anyone could or should run past overboost shutdown.

The GLHS Stage II logic module was programmed to provide 14.7 PSI boost rather than the normal Shelby 12 PSI, in order to give Shelby race cars an advantage in assorted stock car racing venues racing such as SCCA. With stock boost control it was calibrated to make 14.7 PSI but with on track secret bleeding it could make higher boost temporarily. As the logic module was provided by Chrysler, and as it had had CARB certification, it was considered a stock Chrysler part and teams were allowed to use it and run 14.7 PSI.

As 14.7 PSI is the limit of a stock 2 bar MAP, a time cushion I previously mentioned was included to prevent hitting overboost at exactly 14.8 PSI, and the time cushion delayed overboost shutdown for approx. approx 10 seconds, enabling approx. 17 PSI using otherwise legal stock components. Possibly even using the same 10 second timer as in early T-I logic modules. The overboost part was not widely promoted for various reasons but became known as time passed. Obviously boost is monitored by the MAP but administered by the logic module, in this case a Stage II, with a time delayed overboost shutdown.

Keep in mind, this was in the very early days of Turbo Dodge electronics and things that are well known today weren't so much known at the time. 3 bar MAPS weren't really available until the introduction of the 1989 Turbo Trans am and it used a MAF !!

Ever heard of the time limited, "Push To Pass Buttons" on certain modern race cars, something you could almost attribute to Shelby!!

Today most everyone uses a proven calibration but cut our risers, bleeds, zeners and extra injectors etc. and Stage II logic modules are part of our history.

Thanks
Randy

I looked at the calibration file, I didn't find anything...

ShelGame? 5DIGITS? Any input from anyone?

[bamman]

The key word here is 'secret bleeding'. See this antiquated article on it:

http://www.thedodgegarage.com/turbo_map.html

I could imagine putting in one of these boost bleed devices on the car and the car assumes you are going the max boost (perhaps it only sees 14.7 psi) and going full rich. Sure, maybe the Stage II module will support it by going full rich for 10 seconds before hitting overboost shutdown. The problem still is the computer does not know what the boost is, nor does it have the proper fueling for it. So going 17 psi isn't a problem, just as long as you don't detonate.

[Force Fed Mopar]

Pretty sure I was running 16psi on a StageII GLHS w/ overboost disabled years ago. Might have been 15. I had no issues.

[mopar-tech]

See this antiquated article on it:

Ouch! Making a guy feel old!

FYI- With the advent of being able to go into the code and shut off the overboost or extend the timer function its a much better option than playing with a diode or bleed on the map sensor line.

Another FYI- The 87 GLHS, CSX and Shelby Z has a weak wastegate spring that prevents it from boosting much over 14 psi *in stock form*, think of it as an extra safety. You are not going to see big boost numbers which can hurt an engine fast compared to 89 big can wastegate.

Gary

[4 l-bodies]

I have run considerably more boost than 14.7 PSI with my stage II DC 85 logic module (Spearco intercooled). Never being in any one gear for more than a few short seconds. I would lift during shifts, so the overboost timer would reset at each gear change. Early on, I would many times hit overboost just short of finish line when going through the lights in 4th gear. I learned quickly way back when to run a more RPM in each gear so I wouldn't hit overboost in 4th. This of course was aeons before the use of zener diodes or any custom calibration.
Mine and my friends 86 and 87 GLHS (with stage II LM) acted the same way. It would run pretty much as much boost as you could throw at it, but only for a very short time. IIRC it was less than ten seconds. No way would I have ever been in 4th gear for 10 seconds.
Todd

[ShelGame]

The GLHS Stage II is set for 13.7psi. But, it does seem to have overboost essentially turned off. You will never get to the point that the OB timer even starts.

So, yes it's possible the race teams 'bled' the boost up to 17psi. But, it never would shut down. I wonder if there's extra code in there I missed...

[86Shelby]

My experience with the STG2 LM in my GLHS mirrors Todd's, with the car shutting down after short while over 14 psi. A nice long 4th gear pull on the dyno at 17psi or shortly before the lights at the track the car would lay down.

FWIW the original/PO of the car, the service manager at the Omaha dealership where it was sold, said he picked up the LM as soon as they were being offered.

[Force Fed Mopar]

I had an old Neil Emiro switch cal that had stock Stage II on one setting that had the overboost on and it did the same thing as you guys describe. On the other setting the overboost was disabled somehow and it would never hit it. Pretty sure I shimmed the small can wastegate and ran 16psi.

[5DIGITS]

There are timers related to overboost and they were desensitized but not disabled in higher boost/performance cals.
Although, why would anyone run boost levels beyond the capable limit of the sensors and electronics when there are more available options today, to do it properly, vs the "yestertech" of a diode??