Quote:
Originally Posted by Gardus
For comparison, this has 140 lbft at 4000 rpm, peak is 152 at 5465, and at 7k is down to 125.
170 lbft (equal to 230 nm) at 4000 is A LOT of torque from a 2l NA engine.
Good NA engine struggles to get over 100 nm/liter.
|
I'm beginning to consider this motor as an extension of the auto-tuned BEAMS 3SGE, which produced 197 bhp @ 7000 rpm and 159 lb-ft @ 4800 rpm. Same 86mm X 86mm BxS, same developer Yamaha.
The BEAMS did those numbers on 11.1:1 compression, port fuel injection, and bucket/shim lifters, without some of the inherent better balance/vibration elements of the H4.
We're looking at 12.5:1 CR with significantly better combustion from the D4-S (which, coincidentally, Yamaha, along with Denso and Toyota was a primary developer on) reduced valvetrain friction with finger followers on needle bearings, and the better balance and vibration properties of the H4.
168 lb-ft is realistic.
Also given the 86mm stroke, 7500 rpm (redline has been listed at 7400) put the mean piston speed at around 4200 ft/min which is often the upper range of production cars, especially those that involve a cost factor.