[Gmecm] Got a good one for you all now!

Mon Mar 21 13:11:36 UTC 2005

Does your list of modifications include a gear drive on the camshaft instead of a chain? Gear drives can drive knock sensors crazy.

A well-known trait of 383 strokers is they are more prone to knock than a stock engine. Maybe you have knock that you can't hear with your ears, but the sensor can. What is your compression ratio? A 383 can knock even with lower compression. What is the timing of the intake valve closing on this custom grind cam? Too early and your compression can go too high, causing knock. Maybe you need to retard the cam a few degrees.

Maybe your knock sensor is just bad.

Maybe the problem will go away with tuning. And you're looking at a BUTT load of tuning with this build, especially with the blower and nitrous. Don't even think about engaging the blower or hitting the happy gas until the engine's base tune is all in place, or you may find yourself picking up pieces from the road. Are all the sensors connected? Are all the sensors installed? Have you upgraded sensors (like the MAP) to handle the blower and nitrous?

Maybe you should spend a few more dollars and just take this thing in to SuperChips or HyperTech for tuning on their dyno. The cost for that is small compared to what you have already spent. And no chance of grenading your engine.

If you're set on doing your own tuning, you're looking at a long haul with this build. It's going to take a lot of time and even more patience. If you haven't read Bruce Plecan's "Tuning 101," start there. It's written for older ECM's, but the rules still apply. I've been tuning my '88 Formula for nearly two years. Like Bruce, I have burned over 200 chips just getting it right, and I'll probably have 300 burned by the time I get it "perfect." You don't have to burn chips with your model, but you're going spend weeks getting this one tuned "right," and more weeks getting it "perfect."

I certainly don't want to discourage you. Tuning it yourself holds great satisfaction in the accomplishment. But the more radical your build, the longer it will take to get it tuned.

David Haggard

   '88 Formula Firebird "SR-71 Black 'Bird"

   _____  

From: gmecm-bounces at diy-efi.org [mailto:gmecm-bounces at diy-efi.org] On Behalf Of Sixpakmak15 at aol.com
Sent: Sunday, March 20, 2005 7:53 PM
To: gmecm at diy-efi.org
Subject: [Gmecm] Got a good one for you all now!

Hey everyone... Here's my problem... When I plug in the knock sensor, the knock counts go up insanely fast.. around 50,000 counts for just a few minutes of driving... I know its gotta be false, but I'm not sure what I need to do to fix it, or if I can... But here's the ringer... When it's pluged in, the BLMs and INTs go wild, there all split,  as low as 10 and as high as 200... But this is only when the Knock sensors plugged in... When I unplug it, they stay at a constant 128, and don't move... but I know this can't be right either because i'm using a practically stock tune, with a BUTT load of modifications... I'm new at tuning, so can anyone give me a good educated guess at what the heck might be going on? I appreciate the help guys... I've listed the mods below...

93 Trans Am Build... 383 Stroker LT4 54cc Port and Polished 2.05int, 1.625exh Heads...Port Matched LT4 intake, Crane Gold 1.6int 1.5exh Roller Rockers, Callies Forged 3.750 Steal Crank, JE 31cc dish Pistons, Oliver 5.7 H-Rods, Cam Motion 576/555-233/245 at 114 custom grind, Paxton Novi-2000 S/C 10-12psi, NOS 50 shot Wet, Custom Tuning, Dual Walbro 255lph, 50# RX Inj, Hooker Ceramic Super Comp Headers, Off-Road Y-Pipe, Flowmaster Cat-Back, K&N, M6 

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