spdracerut

There was something off about the 80mm turbine wheel. Basically, it was too weak and would fail. Hence why the 9174 was created which from a turbo efficiency point of view is worse because the blade speed ratio is worse. But, the 74mm turbine was strong enough not to fail in expected use envelope. Seems they fixed the design of the 80mm now after a few years of more development.

DavidNJ

Curious, what is your current boost, displacement, fuel, and rpm range? What power is it making now?

Charper732

As I said, it'll be on the dyno on the 21st. I have not dyno'd this turbo setup yet. Last setup I had a F22 with a PTE 6062bb. It made 508hp @ 16lbs. It spooled too slow for my liking which was around 5300.

I've had the BW257 up to 24lbs which felt pretty close to the pte setup as far as torque goes but it had a .88 turbine housing on it and was choking up top so im not sure. My current setup is a F24 at 11.3:1 comp with a 1.00 ar housing on the 257. I have not gone into boost over 10lbs yet as the motor is not quite broken in enough for my liking.

Fuel is E85 only

DavidNJ

I forgot to ask what engine speed. The underlying equations are pretty straightforward. For a given displacement, engine speed, and boost, there will be an approximate amount of air. Ethanol brings some of its own oxygen to the party, as does methanol.

Did you run 24psi with 11.3:1 compression on an OEM piston, connecting rod, sleeve S2000 or was that on a different engine and the S2000 has only seen 10psi?

Charper732

i have yet to decide on what redline will be. Ill take the advice of whatever my tuner decides. Although its on BC2 cams with a 4piston head so power should not fall off until the turbo maxes out. 24psi was on a 100% stock motor. Current motor is fully built f24, only seen 10psi. It has less than 600 miles on it

DavidNJ

It looks like you have an 89mm x 97mm engine with Darton sleeves, fairly strong rods, turbo pistons, and an offset ground k24 crank. The cams seem to be 232/228, which are common turbo durations when installed with minimal overlap.

In the Supra forum posters (lots of posters) run boost in the mid to high 30s on E85 daily drivers. At 8k rpm, a 2.4L may only require 30psi, about 3.1 pressure ratio, to reach 700hp according to Garrett's Boost Advisior: https://www.garrettmotion.com/boosta...ion=calc&dev=1 Your 11.3 compression ratio is higher than the Supra's 8.5 OEM, but at 30 psi with a flex fuel sensor it is probably fine.

800+ hp is probably possible, but will the drivetrain handle the power and will the intercooler have the capacity to keep temps down. I guessing you have been following @hatrickstu 's 900+hp build in another thread.

Is this a track day car also?

spdracerut

8k rpms would be pretty high piston speeds. The stock F22c has a average piston speed of 24.79 m/s at the stock 8200rpm redline. This is very high by the way, pretty much the same as Nascar and higher than old V8 F1 engines. The F1 engines that operated around 18k rpms only had a mean piston speed of 23.86 m/s. With the 97mm stroke of a K24, a speed of 7650 rpm gives a mean piston speed of 24.735 m/s. 8000rpm is 25.87 m/s.

DavidNJ

Piston speed isn't the limiting factor, nor is rod angularity. I doubt you can find any K-series/F-series reports of crank failure, rod failure or piston wear. The limiting factor is the valvetrain, which tends to get more aggressive in ramp to handle the airflow. In a competitive racing class with open camshafts, the ramps get extremely aggressive. These things, in turn, put stress on the valve steps, keepers, retainers, rockers, timing chains/belts/gears, etc. Often the rpm limit is just from the air. I used to run in a class that required a specific model Holly 2bbl carb (restricting airflow), no bigger than a .842" diameter flat tappet lifter (limiting how aggressive the cam profile can be), and prohibited shaft rockers (which I don't think provided any performance hit, but wrecked havoc on my hands do adjustments with the girdle). The profiles were still aggressive enough to make checking the spring rate and occasionally changing valve springs on the head normal maintenance. My car had (really has, it is still in the garage) valve spring oilers to keep valve spring temps down extending their life.

4Piston made a 2.5L K24 for Wiesco using their rods and pistons: 600hp on pump gas, 800 on E85, 1200hp on C85. Over 50psi boost. 4 Piston Racing's 1,000hp-Plus Honda K Series Build

Charper732

I'm on a 4piston CNC head with ferrea valvetrain.

You guys are overlooking one of the most critical parts of a bottom end...the rod bolts and wrist pins. I have carrillo HD wrist pins but my rod bolts are only 3/8 arp 2000s. Overloading the rod bolts is a major concern. Inline pro rates these to 800hp. The forces on the rod bolts rise exponentially as the weight on the small end of the rod (piston&pin) moves faster. I understand the concept but I do not know the math.

DavidNJ

Very good points. One note: the reason for an HP limit is because of the compressive forces on the power stroke, not the tensile forces at the end of the exhaust stroke. Those compressive forces, especially as ignition begins at the end of the compression stroke can be huge. Excessive timing has lead to some engine having S-shaped connecting rods.

I doubt the ARP2000 would be a problem given the relatively light weight of the piston and rod. However, 4P or ILP should know right away. Remember, Honda did the OEM rod for 9k in an emission-certified last-forever street engine. The piston is a much smaller diameter than NASCAR. And neither the piston nor rod was designed to remove every last gram as might be done in a highly competitive wheel-to-wheel racing class. If anything, I'd be worried about the temptation to raise boost to get close to 250hp-300hp per cylinder. What boost was the piston designed for? What about rings since your pistons aren't gas-ported.

What HP was the piston pin rated for?