proxlamus© Posted May 30, 2006 Share Posted May 30, 2006 Hey guys... i have a quick question.. what is the proper spark cut for the soft rev limit retard?? I am using 40 degrees.. which I fear is WAY WAY WAY too retarded after some searching on the forums... ( I am running 17psi on a 8.3:1 CR and MegaSquirt n Spark extra 021u and the stock Nissan dizzy) is 10 degrees adequit? I noticed when I go into the HARD CUT mode.. the RPM's go from like 6,200 RPM down to almost 4,200 RPM .. its a HUGE RPM loss.. is this correct? another question is overboost protection.. is this damaging to the engine? during my datalogs when the hard cut kicks in when I overboost.. the MAP spikes up dramatically.. and looks like a MIS FIRE (which it is obviously) I fear this is damaging the engine rather than protecting it Quote Link to comment Share on other sites More sharing options...
mobythevan Posted May 30, 2006 Share Posted May 30, 2006 10 degrees is adequate and realize that it only soft limits for a fixed time because running continously with retarded timing under load will cause a cherry hot exhaust manifold and turbo IIRC, since it fires late and will still be burning on the way out if too late. Ask Tony D about that, I remember his story of an aewsome spooling turbo that quickly melted down with wildly retarded timing. Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted May 31, 2006 Author Share Posted May 31, 2006 Welp im running 10 degree retard for the Soft Rev limit... for ONE second.. then it hits the HARD rev limit.. which cuts THREE sparks .. and still sprays fuel.. I noticed in nuetral.. like lets say launching .. and revving up.. when it hits the rev limiter.. this SPOOLS the turbo.. and I am actually running 12psi !! IN NEUTRAL!! so this means.. one very very slippy launch.. LoL unless I had sticky tires thought it was kinda cool that I can build boost for launching Also for the OVERBOOST protection.. I am cutting FUEL AND SPARK at 17psi.. this is due to the following... Cutting spark meant fuel would dump into the exhuast manifold.. now a VERY hot exhuast manifold will cause this unburned fuel to ignite.. once this ignites it explodes.. and spools the turbine.. which in turn creates even MORE boost.. so this kinda defeats the purpose.. so I am cutting fuel and spark .. i will go from 11.2 AFR to 20.9 AFR (free air calibration) with a POP from the exhuast.. so it obviously works and protects my engine from overboosting with my Holset. Quote Link to comment Share on other sites More sharing options...
BLOZ UP Posted May 31, 2006 Share Posted May 31, 2006 I did 20 degrees retard soft limit, and cut fuel and spark for overboost. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted June 1, 2006 Share Posted June 1, 2006 I didn't realize until reading this post over at msefi.com, but the soft limit timing is actual timing you enter in the box, not the amount you want to retard when the soft cut limit is reached: GarageWorks wrote: So if you put 10 in the box for soft rev limit retard, it will make the timing 10 degrees any time the soft limit is activated? Not subtract 10 degrees from the value in your map? yes. Quote Link to comment Share on other sites More sharing options...
badjuju Posted June 1, 2006 Share Posted June 1, 2006 wow, there's a major difference... I just put in a base soft retard based on this thread last night. thanks a ton moby, lol Quote Link to comment Share on other sites More sharing options...
badjuju Posted June 1, 2006 Share Posted June 1, 2006 mine has a - on it by default, should it be - to represent retarding? this is strange, because it says "limit retard" and it's -10 by default. I would think that a - value for retarding would be advancing... no? kinda like subtracting a - number would be adding? Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted June 1, 2006 Author Share Posted June 1, 2006 If you are using a Spark based code, e.g. MSnS, Neon, etc, then the soft rev limiter can retard the ignition to a setpoint when the RPM reaches the Soft Limit setpoint. This can help to reduce the engine power o it begins to slow down or feel different so the driver realises they should change gear. The Hard rev limiter will come in if the RPM reaches the setpoint or if the soft limit point is maintained for as long as the max time setpoint. The hard limit can be Fuel, Spark, or a combination of the two if using a spark based code. http://megasquirt.sourceforge.net/extra/revlimiter.htm That makes no sense.. I mean look at the soft rev it says "retard" (deg) and the description on the MSnS extra site says the soft rev can retard the ignition to a setpoint.. so your saying I could type in a value lets say 40.. and then when i hit the soft rev limiter.. it will ADVANCE my timing from 21 degrees to 40?!?! that would be BAD under boost Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted June 1, 2006 Author Share Posted June 1, 2006 WHoa.. so I made a thread on MSefi.com and look at this reply !! http://www.msefi.com/viewtopic.php?t=19312 If you tell it to use 40degrees timing then you have asked for advanced timing. That number is the absolute timing, not a retard from present setting. Trust me, I helped write it and I use it on my car. I agree that the wording can be confusing - I'd never looked at it that way before. It should say "soft limit timing (absolute deg)" and will be changed at the next maintenance release of 029q WOW .. uh oh .. I hope I havent hurt my car! Quote Link to comment Share on other sites More sharing options...
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