Displacement On Demand: Part 3

Posted on December 28, 2011
Late nights at the shop sometimes cause delusions, as Golen’s crew actually thought they could create a real dog with a welding torch and some spare parts. They soon got bored with it, though, when it failed to respond to any of their commands. The dog is, of course, anatomically correct (And wicked haaad! Ed).

Displacement On Demand
Part III: Tuning Golen’s 383 LT1 For 435 Horses (Continued)

C.A.T.S. allows the user to observe virtually everything that is going on inside the engine as it is happening. You can see on the top screen that four degrees of timing was being pulled, which was attributed to the engine stand creating vibrations that falsely set off the knock sensors. To remedy this Matt deactivated them and also pulled several other sensors like those that interact with the air- conditioner and speedometer while he was at it.

Even with those changes, however, something was not right. Not only was the engine not making the power it should, but also it didn’t have that WOT scream. Instead it sounded lackadaisical, lethargic and just plain lazy.

Not knowing what could be causing the aforementioned laziness, attention was turned to the air/fuel ratio, which was at a rich 10 to 1. Injector pulse width was trimmed 3 percent, then 10 percent, to try and lean out the mixture. However, only a slight improvement resulted, generating 409 hp and 421 lb-ft (corrected).

At last it seems we had found the culprit of our misadventures. The dyno session was abruptly interrupted when the rotor blew apart, as you can see in the picture; the metal tip in Dan’s hand was originally connected to the white plastic base. This is a common problem with the Optispark and can even happen on practically brand new units such as this one. While Dan was rebuilding the distributor, owner Chad Golen put in a call to Bryan Herter with the current data. Bryan then sent over a new program, which, when combined with a fresh distributor, seemed to do the trick.

It’s alive! The (uncorrected) horsepower got up to 448.5; and environmental corrections pegged customer Val Becker’s 383 at 435 hp and 447lb-ft of torque. It seems the extra port work may have robbed a little torque, as the base 383 package usually makes around 464. However, it seems well worth it for the 35 extra horsepower, which now peaks at 5800 rpm as opposed to 5000 rpm.

The first step in tuning with C.A.T.S. is erasing the PCM’s original program and uploading a new program, which is called flashing (insert indecent exposure joke here). The new program was written by tuner Bryan Herter based on the new cam and engine specs, then sent to Golen via email. Once Golen’s in-house tuner Matt Abdou flashes the PCM, he has a complete readout of the new map and can make adjustments to anything from the injector flow rate to enabling or disabling any of the sensors. They decide to leave the program alone for now, and to first make some soft pulls to break in the engine before baselining it.

This article was originally published in the April 2005 issue of GM High Tech Performance and is copyrighted by Primedia Inc., All Rights Reserved.
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