Whats safe boost to run on these blocks please, Is anybody on here reliably running higher than 1.5b on standard internals?

 

I would worry about pistons not the the block, your treading on very thin ice at 1.5bar.

 

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

 

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 !!

 

I would not go over 1.3bar on the standard pistons

 

Im running 1.4 bar with no issues as yet !

 

i'm running 503 bhp at 1.7 bar with a splash of meths, engine is forged not standard

 

Thats what i've always been told too.

I'm running 1.35bar

 

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.

 

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.

 

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....

 

Think API David advocates 1.3bar held. The 2.5's OEM hypereutectic pistons don't cope well with too much boost.

 

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

 

mine is running 1.5 bar peak and backs down to 1.2 at 6000rpm

Is this too high ?

 

standard internals 1.3 -1.35 max or its gonna go POP!!!!

 

thats interesting. it was mapped by someone well respected on here as well.

 

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 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

 

Thanks for that. Once I can drive again I will remap it myself and turn the boost down a bit, glad i bought the equipment now.

 

So how many engines you gone through so far? You map your own car?

 

Have not gone through any engines.

I paid to have it mapped first time but doing it myself from now on.

 

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 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.

 

Cool. Give it a go. Let us know how you get on! Good luck.

 

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

 

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....

 

What Joz says is right - anything above 1.35 bar on a standard EJ257 is asking for trouble. Even at standard boost the pistons crack out the ring lands.

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

 

Heed the above its good advice!!

I was running 600 /580 from a pinned, forged 2.5 but I'll end up going 2.3 or 2.1 in the near future.

 

just out of interest, does anyone know what boost the 2.5 sti PPP calibration runs ?

 

I'm sure most mappers would be happy to disclose that figure!