Kryndon
Proven Member
- 944
- 591
- Jan 10, 2014
-
Bulgaria,
Europe
Had the pleasure of speaking to possibly the best/biggest tuner in my country this weekend at our national JapFest. We touched upon a few subjects including flat shifting.
Now, I wasn't certain if we were talking in general or for specific applications, but his general opinion was that flatshifting was extremely bad for the engine itself, disregarding all the benefits for transmission health and switching gears. He said that as you have flatshift enabled and keeping WOT between shifts, the boost doesn't drop as much so let's say you retain 14 psi between 2nd and 3rd gear. At the same time, your MAP (if equipped) is reading those 14 psi worth of air and is then demanding the necessary fuel to be injected. So you end up having a substantial amount of fuel-air mixture going into the chambers but at the same time some of the exhaust valves are open which from scavenging and possible valve float or weak springs start to let the hot exhaust air back into the cylinders. This suddenly ignites the fuel-air mixture prematurely, way before the piston reaches adequate travel for ignition. Essentially, he said this "forces" the piston back down before it wants to do so, and this leads to extreme pressures on the piston crown, pin and rod itself, not to mention bearing surfaces. This is the loud popping and banging we can hear if running NLTS.
On my Talon with ECMlink, I have it enabled without additional antilag, and I can definitely hear some loud banging as I shift gears, but I always assumed it wasn't putting heavy load on the motor during the actual shift as our NLTS works simply by cutting spark.
For us to retain the RPMs high between shifts and thus the boost pressure, some sort of combustion needs to happen, so the ECU needs to inject fuel to keep this process going. Yet, this apparently produces immense stress within the cylinders. So now I'm rethinking about disabling NLTS and just shifting like a granny. I'm trying not to take all he said for given but the guy's tuned more engines than years I've been alive so maybe it's wise to listen to him?
Curious about you guys' opinions and you tuners out there. Do you use flatshifting on any car at all and have you ever had mechanical damage or knock issues from it?
Now, I wasn't certain if we were talking in general or for specific applications, but his general opinion was that flatshifting was extremely bad for the engine itself, disregarding all the benefits for transmission health and switching gears. He said that as you have flatshift enabled and keeping WOT between shifts, the boost doesn't drop as much so let's say you retain 14 psi between 2nd and 3rd gear. At the same time, your MAP (if equipped) is reading those 14 psi worth of air and is then demanding the necessary fuel to be injected. So you end up having a substantial amount of fuel-air mixture going into the chambers but at the same time some of the exhaust valves are open which from scavenging and possible valve float or weak springs start to let the hot exhaust air back into the cylinders. This suddenly ignites the fuel-air mixture prematurely, way before the piston reaches adequate travel for ignition. Essentially, he said this "forces" the piston back down before it wants to do so, and this leads to extreme pressures on the piston crown, pin and rod itself, not to mention bearing surfaces. This is the loud popping and banging we can hear if running NLTS.
On my Talon with ECMlink, I have it enabled without additional antilag, and I can definitely hear some loud banging as I shift gears, but I always assumed it wasn't putting heavy load on the motor during the actual shift as our NLTS works simply by cutting spark.
For us to retain the RPMs high between shifts and thus the boost pressure, some sort of combustion needs to happen, so the ECU needs to inject fuel to keep this process going. Yet, this apparently produces immense stress within the cylinders. So now I'm rethinking about disabling NLTS and just shifting like a granny. I'm trying not to take all he said for given but the guy's tuned more engines than years I've been alive so maybe it's wise to listen to him?
Curious about you guys' opinions and you tuners out there. Do you use flatshifting on any car at all and have you ever had mechanical damage or knock issues from it?
