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View Full Version : retard timming for N.O.S. help please



RandyWS6
March 8th, 2005, 01:05 PM
could some one please help me retard my timming for n.o.s. i am running a 250 shot pro fogger and need to back my timming off about 6* where do i need to go, there is all kinds of different timming ajustments witch one do i need to go to :?:

dfe1
March 8th, 2005, 03:45 PM
Hopefully you'll only be using the nitrous at wide open throttle, so your best bet is to adjust the timing within the appropriate rpm range, from about .48 grams per cylinder up (in the high octane fuel table). Keep in mind that if you're injecting the nitrous behind the MAF sensor, it may affect what the PCM sees in terms of air flow. To be sure you have all the bases covered, data log a wide open throttle acceleration in second or third gear with and without nitrous. Compare the two and you'll see whether the nitrous is affecting air flow readings. Then you'll be sure to bring your spark retard down to the proper point along the grams/cyl scale. Also remember that timing is affected by both the high and low octane tables. If you take six degrees out of one, you'll have to take six degrees out of the other. For your purposes, you might be better off to copy the high octane table into the low octane table. Knock retard will still be active but you'll be giving up a bit of range, so make sure the engine isn't spark knocking. And remember, when you run nitrous, yoiu want your tune up like your sponsor-- rich and retarded.

RandyWS6
March 8th, 2005, 04:13 PM
It's not a dry system it wet there are eight fogger nozzles that spray straight into the cylinders and my car is a six speed thank for the help i will try that

dfe1
March 9th, 2005, 05:52 AM
Wet or dry doesn't matter with respect to the amount of "air" entering the intake manifold versus what the MAF sensor sees. When nitrous enters the manifold, it displaces air that would normally enter through the MAF sensor, so the engine is using more air (actually air and nitrous) than the MAF sensor is measuring. As a result, you'll be at positions in the spark table that you might not get to if you weren't using nitrous. That's why you should cut the spark back beginning around .48 grams per cylinder, even though you'd normally be above .56 at wide open throttle.