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Discussion Starter · #1 ·
01 RS motor with high milage.

I want to rebuild it for boost. Replace the pistons and rods with something forged, (sti or aftermarket). I know the crank is good.. right?

Replace the valves, springs, retainers and guides. all that good stuff.

the ultimate question.
can the block its self handle the boost?
Should I have the cylinders resleeved with iron sleeves?
Should I get a block guard or something similar?

looking for 300-ish whp on a built RS motor. with a custom turbo kit.
 

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Premium Member
2002 2.5 RS-T
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2,960 Posts
01 RS motor with high milage.

I want to rebuild it for boost. Replace the pistons and rods with something forged, (sti or aftermarket). I know the crank is good.. right?

Replace the valves, springs, retainers and guides. all that good stuff.

the ultimate question.
can the block its self handle the boost?
Should I have the cylinders resleeved with iron sleeves?
Should I get a block guard or something similar?

looking for 300-ish whp on a built RS motor. with a custom turbo kit.
the open deck stock ej251 block is perfectly capable of handling 300whp....actually quite a bit more.....

save your money :)


we cant tell you if your crank is good :rotflmao:get it checked by a machine shop, along with the rest of the block of course....but yeah the crank is the same as the sti crank and will be good to a lot more than 300whp if thats what you were wondering....

300 whp is a nice goal....sti internals, a decent sized turbo (something like a 20G)..and some good engine management will get you there no problem....you can also keep your stock tranny...just be carefull....

man 300 is such a nice goal...my guess is i was making pretty close to that with my 18G, ej255 shortblock + RS Heads set up....it was a lot of fun :)
 

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02 F-150 Extended Cab
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2,610 Posts
sleeving is pointless unless you plan on pushing serious boost out of a turbo that can push more then 800 CFM

like..500+ whp-ish..
 

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2002 2.5 RS-T
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2,960 Posts
will do.. woot im in vancouver too haha


another question,
how much boost can the stock block handle?
10,12,14,16? more?
thats rad..where abouts in Vancouver you live? check out the forum me and some friends are on....www.importsview.com... it's just starting up...but we're having a meet on sunday at wings in surrey, you should come out.....

buutt anyway boost on the stock block...well that depends on the internals...also depends on the turbo....20 psi from a td04 is much much different than 20 psi from a gt35....
 

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Premium Member
2001 2.5RS-T BRP
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575 Posts
another question,
how much boost can the stock block handle?
10,12,14,16? more?
I'm currently pushing 12psi into my stock motor with a 3071. I plan to go a couple psi higher after I add meth. I'm trying to push the stock internals as hard as I can before upgrading. The more boost you run the better your tune needs to be.
I haven't dynoed lately but it feels real close to my friends Protuned stage 2 sti, so just short of 300whp.
 

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95 GC 371hp/355tq ej25 1.5xtr
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also depends on the turbo....20 psi from a td04 is much much different than 20 psi from a gt35....
(not being a smart ass....) but seriously, i never understood that. can you explain it? im a noob when it coming to turbo and all that good stuff
 

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2002 2.5 RS-T
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2,960 Posts
(not being a smart ass....) but seriously, i never understood that. can you explain it? im a noob when it coming to turbo and all that good stuff
ok well im kinda tired but i'll try to explain it best i can :)

the first thing you have to understand is that the relative(above atmospheric) compressure discharge pressure (gauge pressure what you see on your boost gauge) is not necessarily what determines how much power you will make.

in an engine obviously gas is what drives the engine, gasoline stores the energy which turns the engine, the problem is you need air to burn this gas...you cant just dump more fuel in...then you just run rich and gain nothing. So a turbo adds more air, allowing you to add more fuel, adding more energy...

therefore What determines the power is the mass flow rate (the mass of air flowing through the compressor, usualy lbs/min) or the volumetric flow rate(cfm) of the air going into the engine....they're basicly the same thing but the volumetric flow rate will vary with the density of the air...at sea level air has a density of 0.076 lbs/f^3....so in these conditions MFR = VFR * 0.076...if you look at turbo stats u will usualy see a cfm rating...my 18g flows 600 cfm @ 14.7psi, a td04 flows 360, gt-35R 800cfm, a t72 flows 920 CFM :D:D. as you can see the larger the turbo the more air they move at the same pressure...therefore you are making more power, without increasing the manifold air pressure....but you are also putting more strain on the engine..


if this doesn't make a lot of sense we can look at it from a different perspective

usually a turbocharged gas engine will make ~9.5-10.5 HP per lb/m of air...

so say i want to make 400 hp (@ flywheel) i will need to flow about 38 to 42 lb/m of air(500-550CFM)....but i want to do this at a reasonable manifold pressure as to not heat the air too much, or run the turbo outside of it's efficiency...

so we use the formula i thieved from a book i got:

MAP=(Wa*R*(460+Tm)/(VE*(N/2)xVd)
where
MAP = Manifold absolute pressure req'd
Wa= airflow (lb/min) (we determined 42lb/min)
R= gas constant = 639.6
Tm = intake manifold temperature (we'll say 110 degrees)
VE = volumetric efficiency (.92)
N = engine speed (say 6000 rpm)
Vd = displacement in cubic inches (2.5L * 61.02 = 152 in^2)

so we have:
MAP= (42*639.6(460+110))/(.92*(6000/2)*152)
MAP= (42*639.6(570))/(.92*(3000)*152)
MAP= (15312024)/(419520)
MAP= 36.49

this is absolute pressure....so subtract 14.7(atmospherica pressure)

and i will need about 21lbs of boost to get the 400hp at 6000RPM..

i need something that will give me a compressor pressure ratio(the ratio of absolute outlet pressure to absolute inlet pressure...for simplicity we'll say inlet pressure is at atmosphere so 14.7) so we have 36.49/14.7= 2.48

so at a pressure ratio of 2.5 i need to be able to flow 500 cfm...so we look at our compression charts:



TDO4:

http://www.stealth316.com/images/td04-13g-cfm.gif
TD05 18G:

http://www.stealth316.com/images/td05h-18g-cfm.gif

obviously the td04 wont cut it, the point i need lies outside the surge lines...but it looks like the 18G should get me to the 400HP goal....and shouldn't be laggy at all..:)

so yeah...i dunno, im no expert by any means so if i made a mistake somewhere hopefully someone will correct me....and i probably went into way more detail than needed but i remember how confusing turbos used to be so i figured this might help out a little...i left some details out cause i didn't feel like typing tooo much.....if you want to know more go read a book lol



and im bored and like to ramble on lol:rotflmao:
 

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95 GC 371hp/355tq ej25 1.5xtr
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^^^^ ok i understand it better now.

im slowly learning....lol. thanks for explaining it to me.
 
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