Missed Shift with Nitrous?
Thread Starter
Burning Brakes
Joined: Oct 2005
Posts: 791
Likes: 2
From: Stafford Virginia
Missed Shift with Nitrous?
I've pondering running Nitrous on my H/C LS2 but I've blown a few shifts over the years and was wondering if it would have blown the motor if I had been running nitrous.
I can even remember one occasion where I missed third and didn't have an aggressive enough over-rev strategy in my tune, my HPTuner log said I hit 8,495rpm... The motor was fine, but I blew the alternater, it straightened out the fan blades and they locked up against the housing...
I have the tune under control now and running N/A I'm sure it wont happen again, but how do you manage an over-rev situation with nitrous?
I know I would be shifting earlier of course as one measure and would apply some type of over-rev strategy but, what method should I use?
I currently employ Fuel cut off, Spark cut off and Electronic Throttle reduction together to control over-rev situations...
I would think it would go lean if I cut fuel and I would think I could build up unburned nitrous in my exhaust if I cut Spark...
I can even remember one occasion where I missed third and didn't have an aggressive enough over-rev strategy in my tune, my HPTuner log said I hit 8,495rpm... The motor was fine, but I blew the alternater, it straightened out the fan blades and they locked up against the housing...
I have the tune under control now and running N/A I'm sure it wont happen again, but how do you manage an over-rev situation with nitrous?
I know I would be shifting earlier of course as one measure and would apply some type of over-rev strategy but, what method should I use?
I currently employ Fuel cut off, Spark cut off and Electronic Throttle reduction together to control over-rev situations...
I would think it would go lean if I cut fuel and I would think I could build up unburned nitrous in my exhaust if I cut Spark...
Last edited by Isaiah48; Oct 15, 2009 at 01:07 PM.
Thread Starter
Burning Brakes
Joined: Oct 2005
Posts: 791
Likes: 2
From: Stafford Virginia
Should I stagger the rpm's between the window switch cutting Nitrous and the Tune cutting the fuel, timing and throttle to avoid any lean spikes, if so how much spread?
Under a hard missed shift, roughly how many rpm's will it still likely climb after the window switches cut off if I stagger the Window switch to kick in about 200 rpm before ecm starts cutting? Knowing this will allow me to build in my comfort factor.
I just ordered ARP rod bolts just to be on the safe side, I run very little piston to valve clearance...
ZO6 Owner
Joined: Nov 2007
Posts: 979
Likes: 5
From: Richmond Texas
I just wired the MSD digital window switch to the tach wire under the hood. It worked perfectly. I always had my nitrous cutting off just before my car made a shift (A6). I'd definitely recommend having it before your fuel/spark cutoff. The engine RPM's will climb but the window switch instantly shuts off the flow. I think 500 rpm's prior to fuel/spark cutoff will be sufficient. Like you said...its all about your comfort level.
Drifting
Joined: Oct 2006
Posts: 1,984
Likes: 16
From: Amityville New York
I has a MSD window switch and has it set to shut off exactly where my rev limiter are set, has been running it for over 2 yrs and never had an issue, remember to also has a WOT switch and set your window switch to be activated over 2k rpm,( now it might sound funny, but some people hit the pedal to the ground, activate the nitrous before motor RMP goes up and puff, the motor just trow a piston through the hood.) Just use all the safety switches, a Fuel pressure switch is also important, set it to,as soon as your fuel pressure drops under a certan PSI it shuts off.
Nitrous are very safe if it is tune and install correctly using all the safety requirements.
Nitrous are very safe if it is tune and install correctly using all the safety requirements.
Racer
Joined: Feb 2009
Posts: 272
Likes: 0
From: H_TOWN WETNBLOWN
Mine sprays at 3500rmps then cuts off 6600rpm with the window switch..400rpms before the fuel/spark cutoff.
