Some options that have been considered for getting a higher redline have been to replace the QR crank with one from an SR20DE. For forced induction setups, squeezing a lot of NOS, or trying to get a revlim higher than 6900 rpm, block guards or Darton sleeves should be used to prevent the cylinder walls from flexing due to the open block construction (which improves hydrocarbon emissions due to a more even distribution of heat around the tops of the cylinders). Lightweight aluminum low tension valve springs need to be replaced with stiffer aftermarket ones. Modifications that would probably have to be done to obtain this level of rpm are stronger connecting rods, removed balance shafts (see below), forged pistons, cams, a lower ring position, and a new oil system to increase oil flow to the rod bearings. Using the QR crank, the highest obtainable revlim with the 100 mm stroke is about 7,000 rpm due to the piston speed limit. The low revlim and 6200 rpm fuel cut are sparing you from blowing your engine. Low tension rings placed high on the piston reduce hydrocarbon emissions but engine detonation, even slight pinging, could easily bend or crack the piston's ring land given the high ring position. ![]() Lightweight slipper skirt pistons were designed for efficiency, not strength, by minimizing reciprocating mass. The small 45mm rod journal diameters (48mm on an SR) creates too small a bearing area risking spun rod bearings. You're taking short breathes which don't allow your lungs to fill. Liken this to your engine hyperventilating. The high piston speed and short dwell time at TDC produces a low volumetric efficiency because there is less time to fill the cylinders, making it hard for the engine to breathe at high rpm. At 6900 rpm, the QR's piston speed is equivalent to about 8000 rpm on the SR. The long 100 mm stroke and short 143 mm rod generates a very high piston speed of 23 meters per second. ![]() Unfortunately, they aren't strong enough to handle high rpm running. This is why lightweight, thin internals were used in production. The QR25 was designed for power and torque through a wide powerband while reducing reciprocating weight and minimizing friction. QR20DE (Japan model) short-stroke is only 150hp - but can rev to 8500 rpm? redline extension might need new pistons and conrods This engine was designed for efficiency, not ultimate performance. It is the light valve springs, not the long stroke, that are responsible for the low, 6100 rpm redline ![]() How would this fit to a rwd vehicle? An adapter plate could be fabricated. light and powerful like the SR20, and fuel efficient and torquey like the KA24DE.Īvailable with 4-speed Automatic (E-ATx) or the XTRONIC CVT trans - all FWD layout with or without awd The QR25DE was designed to eventually replace both the SR20DE and the KA24DE. variable cam timing (37 degree range for intake) ![]() The new enigne is 13 percent lighter than the SR20DE and. The SR20VE (Neo VVL) only makes 187hp.ĬVTC (Constant Valve Timing Control) varies cam at all times, which is better than the Nissan SR20VE or Honda VTEC - which only has two positions. The run-of-the-mill QR25DE in all Sentras makes 170hp. flows exceptionally well-better than any SR20Ĭompare to the SR20DE in the SE-R Spec V at "only" 175hp.
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