Is Retarding the Ignition Timing Really Needed on an Olds Quad 4 Running a 200HP ZEX Nitrous Shot?
Q: I have a 1992 Olds Achieva SCX with a W41 Quad 4 engine built for 250 to 270 hp with 11:1 forged pistons (a point over stock), forged rods, and a cryotreated crank. I have the ability to get a ZEX [nitrous oxide] kit, so I can drop a 200-hp shot on top of it.
A: I was able to advance the timing 4 degrees over the OEM 20-degree total, for a current setting of 24 degrees on 93-octane pump gas. The problem is: For the 200-hp shot nitrous, ZEX wants the timing dialed back 6 degrees, which would be 14-degrees [sic] total. The Quad 4 engine is similar to the old second Gen 426 Hemi, and other modern dual-cam four-valve, four-cylinder engines: It does not like retarding the timing back. If necessary, I can go back down to forged 10:1 compression pistons. I am trying to avoid dialing the timing back as much as possible. What would you suggest to set the total timing at to do this?
It appears you have your timing “math” wrong. If your current total ignition timing tuning is 24 degrees, and you dial back the timing 6 degrees when engaging the 200 ZEX nitrous shot per the manufacturer’s advice, that would leave you with 18 degrees, not 14 as stated. At any rate, dialing in more advance just because there’s no audible detonation does not necessarily result in the best performance. In particular, the GM Quad 4 engine is like other engines with
