alex37211

So the rb25det comes with a t3 turbo with ceramic fins. As I understand it, this turbo is only good for around 12-13 psi or so without breaking. And 300 rwhp is obtainable at this level.

Now...if a gt2871r (.86) were adapted to the rb25 and set to...i dunno...16-20 psi or so, would the result be quicker spool time and and same end result of 300+ rwhp?

After all, that .86 trim 2871r is said to be capable of 400+ hp on sr20's.

jspaeth

Of course, think about your question. If people can make 400+ whp and 330 wtq on an SR with cams and intake manifold with a GT2871R, then if you do the same thing to an RB25, you will end up with a faster spool up (more displacement) and AT LEAST as much power.

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deukalionS14

what he said!

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alex37211

lets say this setup were intended to make a nice drift car...which turbo would yield the best torque curve / powerband for drifting?

codyace

welcome to zilvia

upto there is a button with the word 'search' on it. try it out, you'll be able to see what other RB25 drift guys are using/into.

To me, I'd rather go with a smaller 30r with the .5 extra displacment.

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Silviaoneday

I'm with cody on the 30r, but I perfer big turbo's anyways. There are tons of research on best used turbos for the rb25, go look.

codyace

Or better yet, a smaller framed t3/t4 would do the trick, and cost hardly pennies. Graet for a budget setup. Dont' get me wrong, the 2871r will probably work, but the backpressure in the manifold itself with that sort of displacement will not be conducive of longevity.

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fos240

you guys are aren't thinking logically. the turbo's hp rating is based on the amount of air they can flow. if a turbo makes x amount of hp on one engine, it should be able to make the same amount of hp on another. providing of course the other variables are in align to support it. i.e. if a sr has cams, big intake plenum, standalone ems, etc, vs an rb with a 1" catback exhaust. (exaggeration).

also, a larger displacement engine is going to flow more air at the same psi than a smaller displacement engine. so a 2 liter engine is going to have higher boost (in psi) than a 2.4/5/6 with the same turbo.

frankie

frankie

codyace

I think the suggestions here are pretty logical. Not sure if you misread them or not.

"To me, I'd rather go with a smaller 30r with the .5 extra displacment."

"Or better yet, a smaller framed t3/t4 would do the trick, and cost hardly pennies. Graet for a budget setup. Dont' get me wrong, the 2871r will probably work, but the backpressure in the manifold itself with that sort of displacement will not be conducive of longevity."

what else is there to say? obviously airflow isn't the issue, but at the same time, to much isn't good either (as it will push it past choke limits, etc etc) Sure a 2871 will work on one, but as (I) stated above, it may not be be the safest choice due to the heat creation and back pressure in the manifold itself (lets face it a 6 cylinder 2.5 will be awfully restricted by a t2 flanged turbo, regardless of it's compressor efficiency)

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alex37211

So how about a t3 flanged 2871r? Would that mean the exhaust side would be larger? Would that solve the back-pressure issue?

Norty

The t3 turbine housing option would help with back pressure to an extent. This would be a pretty fun set-up if you like insta-spool. LOL aka 1st, 2nd, and 3rd just a little gas and blow the tires out, remindes me of a sr20 with a disco-potato. Not a lot of top end but makes a fun street car. Seems to me the back pressure wouldn't be too bad at less than 20psi.

Z U L8R

gt30/76r .63



blue = 22psi
red = 20psi

i was lifting the head @5200rpm, stock head/cams, stock bottom end (i'd recommend built bottom end), 550's + power fc

350+ft lb of torque at 3500rpm ftw. 28/71 = poo poo

gt30/76r .63 ftmfw

gt35r = 500rwhp @ 19-20psi, a little lazy for your taste tho

Dave

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codyace

Z U L8R's post pretty much sums up what I was getting at. If you're going with a t3 turbine, you may as well get a compressor behind it that will make awesome power.

His graph is exactly why (as I said) a smaller 30r, or even a t3/t4 with the right housings would be joyous...full spool way 3500 rpm or lower, with 450 whp capability and 350 ft lbs? YES PLEASE. That is a yummy car btw Z U L8R



Valid points, as I am addicted to quick spool as well. My feelings still remain the same, as boost pressure per pressure, you'll make more 50 more hp and trq and have such a difference in spool that it would really be negliable. Compressors are nearly the same, so by taking advantage of the larger flanged (albiet still small) turbine housing (to me) is a huge advantage as it's simply not such a restriction at that point.

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slider2828

RBs are sick motors out of the box... ZUL8R's dyno graph is sick.... 3500 RPM and making like 300 FTlbs of torque... Crazy.... 305's on the rear? Yes please....

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Z U L8R

thanks Cody/Slider

if i could do it all over again i'd do the billet precision 62mm on it, sold the car to a friend of mine and fully built the motor for him.

i tuned it the other day actually, but since it's still kinda fresh we only turned it up to 5500 rpm and 15psi.

was 320hp/310 tq stopping @ 5500rpm with the graph going straight up like 30hp every 300-400rpm on an safc >_<

gt30/76r .63 = bad ass 400+hp street turbo. definately proportionately matched for an rb25

revving it all the way out to 72-7400 i wanna say at 14-15psi she was 370ish when i had it.....that was honestly the only time i ever used "low boost" :P

if all you want is 300rwhp....you could do that on the stock turbo.......for a little while

gl,

Dave

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rubhamusan

RIP garage R33 that I built used a 2871 t3 flanged turbo with a 38mm tial WG.IT produced 390 whp and 385 ft lb of torque at 3100 rpms.And stayed in that power range all the way to redline. Awsome drift set up.

codyace

have a graph by chance? that would be awesome to see.

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Z U L8R

ya that car was pretty sick, i heard he just traded it for an rb26'd s15 ^_^

i wanna see that graph too, and i never asked him how much boost he was runnin

Dave =]

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rubhamusan

Been like 2 years.I looked around but could not find it.ZUlater knows me and the car.We dont even have the car anymore.yeah this season we are running a 26 powered s15. Krappy has the r33 now.I think he is going todo a retune.So he should post a graph. And that was at18psi. It was like driving a ls1 powered s13 came on real quick.

Z U L8R

good times

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codyace

why is that RB's up north here don't last lol. I've got such a sour opinion of them as any local one succcccks.

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rubhamusan

The last 10 years I have seen many many 25's blow up very easy. 20's seem to hold power really well and 26's aswell. I will not own a 25 unless the pistons are replaced and new bearings.or it's aneo.

Z U L8R

only like 2j's seem to last with good power now. i concur. it probably has something to do with them being almost 15 year old motors haha

cause i have a sour taste towards sr's now. i quit doing sr's in my cars 6 years ago but just sayin. these motors are getting old.

that's why i had no problem throwing head gaskets and studs in my 25's and cranking up the boost, then as time progressed my opinion changed on "what the stock internals are good for"

now i advise anything over 350 to definately build the bottom end...otherwise you're just rollin the dice and it's only a matter of time.

me and scott go way back on the rb motors though, we both been around the block four or five times lol. he was doing rb's back in the day when he worked at top hat, and now at Rip.

my new advice for the budget rb enthusiest is to get an rb20 in their car and have fun with that for a little, then once they recover financially, get an automatic rb25 motorset, sell your 20 motor, harness and ecu, basically pay for the 25 auto, bolt it in, wire it up and now you got a "$500 stroker kit" haha

my first 20 tranny on my 25 lasted 7 months with no problems beating it everyday, going to the track and launching it, and doing hwy runs every weekend. then i was getting into boost already in third gear on the on ramp and as soon as it hit 20psi it stripped every tooth off of third gear lol. i got another rb20 tranny that night from a buddy and was back on the road in 3 hours.

that tranny lasted two weeks with the boost turned down and just daily'ing the car to work, and i barely layed into it in second gear and it stripped every tooth off 2nd. then i was like [email protected]#$ it and got a z32 n/a 5 speed, a 26 bellhousing. put it in the Z and it's been in there for the last 4 years no problem.

crazy

Dave

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slider2828

The 25's I think had weaker internal components I think stock from factory. I mean most have to rebuild it or it would never last too long... Thats what friends from Japan tell me. 26's definitely had stronger internals, dunno much about the 20's.

But that is true of any motor....

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slider2828

I was tuning my friend's 2j with a T78... That is a smooth engine and the boost came on so nicely even with that fat turbo... Makes SR's run like tin cans.... God I want a 2JZ.....

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rubhamusan

rb20 with cams pfc and gasket using a 2871 can do 400 for a couple years easily.done it a few times. thats infact how I ended up doing a 25 with 2871. I built a s14 with a rb20. gt3076 kelford cams and extrude honed the head. 650cc inj and a PFC. Later went to a 2871 t3 flanged turbo.Had a lot of lag on the 3076. then got a r33 with a blown 25.parted out the s14.threw the turbo and manifold on the 25.Used weisco pistons and gtr con rods.balanced everything. took it to the dyno and was like hell yeah. clack the 33 into third clutch kick and drift mad easy.

jdm213

i think you should go a bit bigger to meet your power goals, not to big though. because the gt2871r is best for small displacement engine and you have more so you shud go a bit bigger and im sure youll be happy with the power youll make in the future

alex37211

I'm liking this. I think I may go with the 2871 after all. Do you know what supporting mods the car had?

Darksun280

What do you concider alot of lag? what was it spooling that by? Anything that spools by 3500-3700 in 3rd is decent to me.

rubhamusan

Yeah weisco pistons ,gtr con rods,650cc inj by sard ,power fc with boost control kit.Apexi head gasket,N62 maf. greddy intake and q45 TB.
here is the car.
YouTube - Rip Garage Skyline R33 Drift at Gresham Motorsports Park