EJ257 Safe boost?
10 January 2012, 08:07 AM
#3
Thats what i thought. Im told 400bhp is the limit on a 2.5 sti, but forged pistons and 500 is acheiveable as rods and crank are quite good. What boost is more suitable on the 2.5 and what power is possible at that level? presuming other supporting mods are good enough, i.e turbo, injectors, fmic etc
10 January 2012, 08:20 AM
#4
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On a built 2.5, I'm getting 460 ft-lbs at 1.5 bar tailing down to 1.3 bar giving 460BHP. But that is with some phantom det causing the timing to be cut slightly. Bob R who mapped it said it should be another 20 ft-lbs/BHP if the sensor is desensitised. The P Det is not noticeable when driving.
That is with std cams but Ric Wood cnc flowed heads.
Would expect 500 with 1.5 bar held.
As I understand it, its the upper cylinder movement causing head gaskets to blow that is the weakness with these, if you sustain over 500BHP. I tried to help stiffen the upper cylinders using 14mm head studs.
Wouldn't like to risk 1.5 bar on std internals - but no doubt someone will try it !!
That is with std cams but Ric Wood cnc flowed heads.
Would expect 500 with 1.5 bar held.
As I understand it, its the upper cylinder movement causing head gaskets to blow that is the weakness with these, if you sustain over 500BHP. I tried to help stiffen the upper cylinders using 14mm head studs.
Wouldn't like to risk 1.5 bar on std internals - but no doubt someone will try it !!
Last edited by StanS; 10 January 2012 at 07:39 PM.
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10 January 2012, 01:27 PM
#9
I'm running 1.42 bar on my standard EJ257. Andy forrest 20g, FMIC, 3" turbo back, 3 port etc etc.
I'm getting 309 bhp / 301 lbft (on a hub dyno) so lets say low to mid 380's at the flywheel?? Had these figures since the end of August and using the car as a daily driver. I am not boosting it too much now as it needs a clutch, but seems OK to me.
My mapper said the engine still felt strong when mapping and there was maybe another 15 - 20 hp in the pistons, but I left it at that for a "safe" margin.
I know that nothing is guaranteed at this level and if it lets go then I'll have a pinned / forged build which you should always plan for if pushing the limits IMHO.
I would agree with Toney83 - again, told by my mapper, that drop in forged pistons would see about the 480 mark before the standard rods start hipping their limit.
I'm getting 309 bhp / 301 lbft (on a hub dyno) so lets say low to mid 380's at the flywheel?? Had these figures since the end of August and using the car as a daily driver. I am not boosting it too much now as it needs a clutch, but seems OK to me.
My mapper said the engine still felt strong when mapping and there was maybe another 15 - 20 hp in the pistons, but I left it at that for a "safe" margin.
I know that nothing is guaranteed at this level and if it lets go then I'll have a pinned / forged build which you should always plan for if pushing the limits IMHO.
I would agree with Toney83 - again, told by my mapper, that drop in forged pistons would see about the 480 mark before the standard rods start hipping their limit.
Last edited by Wayne STI; 10 January 2012 at 01:29 PM. Reason: additional info
18 January 2012, 01:57 PM
#10
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Last run I did was 1.8 bar peak and 1.7 max on 2.5L forged pistons rods, EJ257...not sure BHP but must be up towards 500 mark as last measured roller was 483/494 and that was 1.65 bar. Running WI, meths in tank and 50/50 meth water in WI tank, plus many other mods.
18 January 2012, 05:06 PM
#11
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I had 1.5BAR tailing to 1.0BAR and the head gaskets duly went and leaked...£5,000 late I now know 1.3BAR IS the safe limit. If you think otherwise, it's only a matter of time......
Alan sorted mine nicely though. Still standard outside so 348ish corrected on high boost. The previous muppets had let the turbo give all it had which it now also does but correctly mapped and held together by one of The Engine tuner's lovely builds....
Alan sorted mine nicely though. Still standard outside so 348ish corrected on high boost. The previous muppets had let the turbo give all it had which it now also does but correctly mapped and held together by one of The Engine tuner's lovely builds....
18 January 2012, 06:01 PM
#13
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Most mappers and engine builders will say that the std pistons for the 2.5 are good for circa 1.3bar and that's it. IIRC from talking to David at APi Litchfield found out the hard way in the developement of the T25 how much the standard ones can take.
A good map with the standard turbo and supporting mods will see you at a very nice 350 of each (usually a bit more on torque) and a very nice drive; spools from nothing!
My Hawk with a BRD map with just the PPP spec, made 348 bhp and 380ft lbs IIRC.
If you want more, just do it properly and get the motor forged. Mine now peaks at 1.75 bar and develops 473/482.
With the 2.5 it's best to think in terms of calling it quits at the mid 400s. With a decent set up, they'll do that happily and be a great drive - 1 bar of boost achieveable at well under 3000rpm. If you want higher and you plan to use it, you'll have to think about re-inforcing (if that's the right term) the block or going for a smaller capacity.
Ns04
A good map with the standard turbo and supporting mods will see you at a very nice 350 of each (usually a bit more on torque) and a very nice drive; spools from nothing!
My Hawk with a BRD map with just the PPP spec, made 348 bhp and 380ft lbs IIRC.
If you want more, just do it properly and get the motor forged. Mine now peaks at 1.75 bar and develops 473/482.
With the 2.5 it's best to think in terms of calling it quits at the mid 400s. With a decent set up, they'll do that happily and be a great drive - 1 bar of boost achieveable at well under 3000rpm. If you want higher and you plan to use it, you'll have to think about re-inforcing (if that's the right term) the block or going for a smaller capacity.
Ns04
Last edited by New_scooby_04; 18 January 2012 at 06:07 PM.
18 January 2012, 07:09 PM
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There seems to be lots of opinions and storys of doom and gloom but little facts here (as usual).
Bob Rawle mapped my 2.5 with standard internals. 1.2 bar and 1.4 bar which reduces to 1 bar at higher revs. That gave 360/433 which is considered safe. More than that would require forged pistons to be on the safe side.
Bob Rawle mapped my 2.5 with standard internals. 1.2 bar and 1.4 bar which reduces to 1 bar at higher revs. That gave 360/433 which is considered safe. More than that would require forged pistons to be on the safe side.
18 January 2012, 07:19 PM
#18
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BOB WORKS ON MY CAR TO , DT SPD THE VF 43 IS JUST ABOUT FINISHED AT 5.500RPM WICH IS WHY YOUR BAR IS DOWN AT 6000RPM , IF YOUR CAR RUNS FINE & U HAVE NO ISSUES GREAT , BUT ME PERSONALLY , I WOULDENT RISK IT RUNNING 1.5
18 January 2012, 09:48 PM
#22
Good luck!
I'd always say for the sake of a £3k engine its worth paying an expert a few hundred quid to set it up safely!
Heard some bad stories about people mapping their own cars. But at the same time all the mappers we know started doing this!
I'd always say for the sake of a £3k engine its worth paying an expert a few hundred quid to set it up safely!
Heard some bad stories about people mapping their own cars. But at the same time all the mappers we know started doing this!
18 January 2012, 09:58 PM
#23
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I initially thought the same and paid £350 to have it mapped but was not that impressed with drivability and now found that boost is a little too high.
Ive been mapping oem engines for 15yrs so I will be ok.
only problem is i cant drive for 10 weeks because i broke my ankle and leg.
Ive been mapping oem engines for 15yrs so I will be ok.
only problem is i cant drive for 10 weeks because i broke my ankle and leg.
18 January 2012, 10:23 PM
#25
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my 2.5 built by harvey
forged pistons, acl bearings
ran 1.35 bar and made 420/430 on a sc46
well happy and quite safe, nevr missed a beat in over a year
forged pistons, acl bearings
ran 1.35 bar and made 420/430 on a sc46
well happy and quite safe, nevr missed a beat in over a year
19 January 2012, 08:33 AM
#26
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Hi
im running a 2.5 wrx hawk on optimax and 368bhp @ 1.5bar tailing off to 1.37 bar on a vf43 with standard internals and the standard td04 restrictor pill in the actuator hose and its been fine so far but it has been mapped so it does overfuel a bit to get rid of knock and det.... not too much that it bore washes tho....
Last edited by Wilky0302; 19 January 2012 at 08:34 AM.
19 January 2012, 11:59 AM
#27
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AND after a few thousand miles they start to suffer from bore flex of the cylinder walls, cos they are so thin. which can lead to noise, oil burning and all the usual good stuff.
Don't ever rebore a 257 for oversize pistons unless you own Shell or another oil company, as you'll need plenty of oil to put in at every service.
I know there are people out there running more than 1.35, they are getting away with it. It is not advised by us or any other serious quality engine builder, you know who they are, and shouldn't be done by any quality mapper either.
David APi
Last edited by APIDavid; 19 January 2012 at 01:52 PM.
