SR20det opinions on running a 9:1 compression for up to 500 whp?

[filluptieu]

Im trying to decide which route to purchase. I want to build my sr20 to achieve 500 WHP max. the piston will be 87mm. the turbo will either be a .86 gt2781 or a .63 gt3071r

Please give advice if you actually have experience. Thanks

[Kingtal0n]

2871r cannot flow 54lb/min

[filluptieu]

Originally Posted by Kingtal0n

2871r cannot flow 54lb/min

I'm sorry. Seems like I do not understand what you are trying to say here. Please elaborate. Im interested in learning

[R@ddy]

What he's saying is, the 2871R does not have the flow capacity to reach 500whp.

[filluptieu]

Understood. I was hoping for 400 WHP with the 2871r. does that sound correct?

[filluptieu]

Nobody has answered the question about the compression level. still looking for an educated answer

[di-devol]

I'm running 9:1, right around 400hp if that helps any.

[jr_ss]

9:1 will be fine with good tuning...

[filluptieu]

is there a noticable difference from 8.5:1 to 9:1?

[di-devol]

^Nope, not that I can tell anyway.

[filluptieu]

I guess maybe it would just be safer to run the 8.5:1 is that case then?

[S@nt0s]

9:1 is fine nothing to worry
as long as your tuned for it your perfectly ok.

[Lutz Performance]

you should have zero issue running 9:1

most people dont really need 8.5:1, just happens to be that way stock

[Kingtal0n]

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

[filluptieu]

So I have thought long and hard about this.

I came to the conclusion that a fully built sr20 and a stock 2jz with a large single will come out to the same price however the sr20 should in theory last long since it is a fresh motor. The transmission and harness is so expensive.

Please take into factor that i want a/c and p/s either way i go.

What do you guys think?

[fliprayzin240sx]

Yes...no replacement for displacement. You'd be pushing an SR hard at 500hp while the 2JZ wont even be breaking a sweat. In the long run, money wise and reliability wise, you'd be better off going I-6 turbo setup.

I've had a 500hp SR20 on a GT3582R, in the middle of an RB25 swap.

[Kingtal0n]

Originally Posted by filluptieu

The transmission and harness is so expensive.

Please take into factor that i want a/c and p/s either way i go.

What do you guys think?

A/C and PS is no problem on the 2jz.
For a cheap transmission on a daily driver, I recommend the OEM automatic, with a part throttle accumulated shift improvement kit and around 3200rpm stall on a 4:1 rear gear. Dont cheap out on the converter, that is the main key to getting good performance from an automatic. Good clutches also help, but it isnt always necessary.




A turbo blanket and some heat wrap really go a long way to cleaning up the exhaust side and cooling it down under the hood.
if you will be on the highway alot then a 3.5:1 rear gear is a better option. Use a smaller turbo, though, and a smaller stall, around 2800 instead.
this car was built about five years ago. It went 11's on the track around 120mph with "first pass ever" driving. Turbo is 6776 precision. I felt the exhaust housing was far too large but the owner was spraying nitrous and using drag radials to spool/launch so it didn't matter. A/C, PS, of course. Around 26psi it produced 800RWHP with the OEM engine internals, including camshafts, and C16 leaded fuel. The total swap cost was about 18k, including the vehicle, and paint.

The business that painted/swapped the chassis is still around doing these swaps. PM me for more info.

[Kingtal0n]

Another one







cookie cutter swaps. no hunting or guessing parts. years of proven reliability on tap.

[filluptieu]

Is a shifter modification needed on a v160?

[zurud]

like you can afford v160

[filluptieu]

Originally Posted by zurud

like you can afford v160

LOL... you are just joking right? I believe I can. I make enough for it.

[rotation3x]

im looking to get 9:1 86mm cp pistons for my sr and I am stuck on a cosworth 1.1mm or a oem headgasket. Will the oem gasket hold? I have arp studs. not 100% if I will buy a isis t25/28 replacment with stock injectors or run my gsp 18g with 550cc. What should I do?

Btw my reason for high comp. pistons is because I want my motor to be a little more responsive in the lower rpms when I am not boosting.

[LBSil80]

Originally Posted by rotation3x

im looking to get 9:1 86mm cp pistons for my sr and I am stuck on a cosworth 1.1mm or a oem headgasket. Will the oem gasket hold? I have arp studs. not 100% if I will buy a isis t25/28 replacment with stock injectors or run my gsp 18g with 550cc. What should I do?

Btw my reason for high comp. pistons is because I want my motor to be a little more responsive in the lower rpms when I am not boosting.

if you go with the cosworth then youll still loose a little compression but im not sure by how much. But from what im told if u want high boost then u want less compression and vise-versa but regardless youll need a reliable tuner. why dont u consider going a mill over size or so on the pistons?

[rotation3x]

Originally Posted by LBSil80

if you go with the cosworth then youll still loose a little compression but im not sure by how much. But from what im told if u want high boost then u want less compression and vise-versa but regardless youll need a reliable tuner. why dont u consider going a mill over size or so on the pistons?

I figured since the cylinders were in good shape to not mess with them. I have the block and head resurfaced and the cylinders have been rehoned.
I am not really looking to run high boost I just want my sr to have good throttle response and spool my turbo up fast. My block has .005" shaved and my head has .004" shaved. I was thinking of running a oem head gasket but don't know if that will be good since I am raising the c/r to 9:1 or I was looking at getting the cosworth 1.5mm.

plan is to run my gsp 18g at 14psi max with either oem headgasket or cosworth 1.5mm ?? Arp studs, fresh main/rod bearings and cp 9:1 86 mm pistons. I have a power fc. all thats left to get is injectors either 550 or maybe over kill it with 740's

[LBSil80]

well i talked to a guy about this and he said u should be alright esp if u have the pwrfc. from what he said ude be cool with the stock oem gasket but he would use the 1.1 mm to be safe but also because basically ude be defeating the purpose if u went 1.5mm. but as far as injectors go it all depends on ur hp goal. if ur looking to get around 400 to the wheels then ide go with the 740's to be safe.

[TheRealSy90]

There was a video posted on here a while back but I haven't been able to find it right now. It was a drift car running 13-1 compression on c16. Pretty awesome.

[rotation3x]

Originally Posted by LBSil80

well i talked to a guy about this and he said u should be alright esp if u have the pwrfc. from what he said ude be cool with the stock oem gasket but he would use the 1.1 mm to be safe but also because basically ude be defeating the purpose if u went 1.5mm. but as far as injectors go it all depends on ur hp goal. if ur looking to get around 400 to the wheels then ide go with the 740's to be safe.

That was something I took into consideration about the HG but forgot to ask my machinest. Nissan has resurfacing limit of 0.008" from the head and block total. I have 0.009" total. I assume when nissan says you can take off .008" they would still use there own oem 1.1mm gasket. If I do that it would be like running a 1mm gasket if I didnt get my block and head resurfaced. I would like to think there is enough clearance to run that so I dont sacrifice my hard earned money on 9:1 pistons.

[Winkler22]

Based on all the research that I have done on here; Apexi HG seems to be the #1 recomended aftermarket brand and cosworth #2, but you should be fine w/ 1.1mm gasket. And I have always been told that when in doubt about injectors always go larger, especially if you are getting the car tuned. You can only increase the fuel so much before maxing them out, but you can always decrease them.