Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum - View Single Post - SR20det opinions on running a 9:1 compression for up to 500 whp?

Kingtal0n · 08-08-2012, 06:59 PM

cookie cutter sr20s usually run around 350whp on stock location turbos. Doesnt matter if the bottom end is built, a used 50k engine, OEM longblock, from 1992, will turn out 350whp with a good tune for 50k+ miles.
you only need:
turbo, injectors, maf, ecu, cams, clutch
and some fabricated plumbing/lines.

Beyond 350whp in street cars, daily drivers, it is generally customary to install forged pistons and rebuild the engine for a lifetime (100k+ miles) of operation beyond the 400RWHP mark. You can expect a maximum potential "enjoyable" power level for the street with a 2.0L engine between 400-500RWHP. After 500 wheel horsepower (550 brake horsepower) the 122 cubic inches requires significantly more boost and/or rpm than I am willing to dub "street, quiet, pump gas, daily driver". Those numbers are, specifically, 18PSI and 7800rpm respectively.

While this option looks promising, allow me to point out some often overlooked cons:

1. Unless you own all of the tools, and machines, and build the engine yourself, you are at the machine shop's/engine builder's mercy when it comes to high quality assembly.
2. A "built" engine generally requires ALL new wear parts, from springs to cams to bearings to the rear main seal to the timing chain & guides and even the little O-rings on the oil filter housing. Every part has a right and wrong way to be installed, and they are quite expensive en total.
3. Forged pistons require time to warm up, and even then piston slap is going to happen until you drive it for a while and get them hot (800*F?). This was never a con for me until I started having to be late to school, telling the instructor that I was late because my engine has forged pistons...
4. Clearances are larger in a "built" engine generally because high performance engines run looser tolerances but also to allow the pistons to expand as mentioned. besides additional cylinder wear due to piston slap, you also will produce slightly more blow-by, the leakdown test in one such warm CP-piston 9:1 compression SR20DET was around 14-18% after driving for several thousand miles (20,000miles) over the course of four years.

And finally #5:
you will invest heavily into these parts, and pray the machine work all comes out great and the engine assembles nice and every bearing clearance is perfectly round and right.... All of this for an additional 100~150 pump gas horsepower? No thank you,

Not when a 2JZ OEM bottom end is capable of 450RWHP with the same life expectancy as a SR20 at 350RWHP, that is, 50k+ miles, and it will spool the (identical) turbocharger faster than the SR20 due to it's larger displacement. This is lieu of the fact an OEM 2jz bottom end is about as costly as an OEM sr20 bottom end!

Nutshell: for daily drivers, reliability, pump gas:
350rwhp- use an OEM sr20 with cams,injectors,ecu,maf,turbo,lines,plumbing.
450rwhp- use an OEM 2JZ- with cams,injectors,ecu,map,turbo,lines,plumbing.
550rwhp- use an OEM LSx- turbocharged of course

This ONLY works because it costs less to retrofit a 2jz into a 240sx than to build an SR20 engine. If the cost was similar- even close, I would choose the SR20 because it drops into the chassis without modification.

Also, consider something in the bottom end fails. You spin a rod bearing because you over-revved the engine. It is much cheaper to source another used OEM 2jz block than to rebuild a "built" sr20det engine.

/the ten years of threads and experience you can search through to realize this

08-08-2012, 06:59 PM	#14
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 42 Posts: 4,829 Trader Rating: (17)	cookie cutter sr20s usually run around 350whp on stock location turbos. Doesnt matter if the bottom end is built, a used 50k engine, OEM longblock, from 1992, will turn out 350whp with a good tune for 50k+ miles. you only need: turbo, injectors, maf, ecu, cams, clutch and some fabricated plumbing/lines. Beyond 350whp in street cars, daily drivers, it is generally customary to install forged pistons and rebuild the engine for a lifetime (100k+ miles) of operation beyond the 400RWHP mark. You can expect a maximum potential "enjoyable" power level for the street with a 2.0L engine between 400-500RWHP. After 500 wheel horsepower (550 brake horsepower) the 122 cubic inches requires significantly more boost and/or rpm than I am willing to dub "street, quiet, pump gas, daily driver". Those numbers are, specifically, 18PSI and 7800rpm respectively. While this option looks promising, allow me to point out some often overlooked cons: 1. Unless you own all of the tools, and machines, and build the engine yourself, you are at the machine shop's/engine builder's mercy when it comes to high quality assembly. 2. A "built" engine generally requires ALL new wear parts, from springs to cams to bearings to the rear main seal to the timing chain & guides and even the little O-rings on the oil filter housing. Every part has a right and wrong way to be installed, and they are quite expensive en total. 3. Forged pistons require time to warm up, and even then piston slap is going to happen until you drive it for a while and get them hot (800F?). This was never a con for me until I started having to be late to school, telling the instructor that I was late because my engine has forged pistons... 4. Clearances are larger in a "built" engine generally because high performance engines run looser tolerances but also to allow the pistons to expand as mentioned. besides additional cylinder wear due to piston slap, you also will produce slightly more blow-by, the leakdown test in one such warm CP-piston 9:1 compression SR20DET was around 14-18% after driving for several thousand miles (20,000miles) over the course of four years. And finally #5: you will invest heavily into these parts, and pray the machine work all comes out great and the engine assembles nice and every bearing clearance is perfectly round and right.... All of this for an additional 100~150 pump gas horsepower? No thank you,* Not when a 2JZ OEM bottom end is capable of 450RWHP with the same life expectancy as a SR20 at 350RWHP, that is, 50k+ miles, and it will spool the (identical) turbocharger faster than the SR20 due to it's larger displacement. This is lieu of the fact an OEM 2jz bottom end is about as costly as an OEM sr20 bottom end! Nutshell: for daily drivers, reliability, pump gas: 350rwhp- use an OEM sr20 with cams,injectors,ecu,maf,turbo,lines,plumbing. 450rwhp- use an OEM 2JZ- with cams,injectors,ecu,map,turbo,lines,plumbing. 550rwhp- use an OEM LSx- turbocharged of course This ONLY works because it costs less to retrofit a 2jz into a 240sx than to build an SR20 engine. If the cost was similar- even close, I would choose the SR20 because it drops into the chassis without modification. Also, consider something in the bottom end fails. You spin a rod bearing because you over-revved the engine. It is much cheaper to source another used OEM 2jz block than to rebuild a "built" sr20det engine. /the ten years of threads and experience you can search through to realize this Last edited by Kingtal0n; 08-08-2012 at 08:16 PM..