BlooSooby

Hi there, about 6 months ago I had a new engine built around a new EJ257 shortblock with forged CP pistons and billet rods. I'm using an ECUtek remap, 750cc injectors, APS TMIC, 3" Turbo XS cat-back exhaust, cat-less up-pipe, ported and flowed heads and AVO450s turbo.

When the car came back from the builder after being dyno'd it was making 21 psi boost and the builder said that the turbo was just about at the limit of it's performance. Since then I have swapped the drilled out restrictor pill for a stock 1.2mm pill. Now, albeit tentatively, I have seen 27psi boost. The car isn't boost spiking and drives great but I'm not sure whether the original pill was drilled out too far or whether the stock one is too restrictive, causing higher than planned boost levels....

The thing is, I had the impression that the AVO turbo was at it's limits at 21 psi, obviously this isn't the case.

Is it safe to be running 27psi boost on my set-up? (Semi-closed block)

Cheers

StickyMicky

i ran 24 psi on my stock shortblock for a short while and cracked a piston ringland

i suspect your uprated one will be ok as long as its mapped properly?

Peanuts

iTrader: (15)

convention seems to be about 1.5/1.6bar in old money or 22/23psi although thats by no means fool proof or set in stone.
There seems to be some mileage in running the car at lower boost for a fair while and then pushing it further when it's well used.
I have a forged 2.5Lbuild and I run it at 1.6bar on an md321T for now.
I may well push for 1.8 bar peak and 1.6bar held in the future if I ever get bored or used to the power.

Shaun

Is the OP's post not conflicting? The title says about the block and the post refers to the limits of a turbo? Which one is it?

Turbo... I have no idea about.

Block I have a number of views on.

Peanuts

iTrader: (15)

Don't listen to Shaunee
He has a mod that most don't

MartynJ

We have been running stock blocks with forged rods and pistons at up to 2 bar for a while now, no failures as yet.
If the motor is built well and mapped det free, you shouldn't have any problems @ 1.8 bar held.

Peanuts

iTrader: (15)

I'm not that brave

BlooSooby

Errrrr, the title of the OP is questioning the max boost that I can 'safely' run on my EJ257 block with forged internals. I then go on to state how much boost I am getting from the turbo at present, thereby giving readers more info. I'm glad everyone else managed to comprehend the OP

The engine has been remapped since the work was carried out.

Thanks fro the info everyone!

Shaun

Thanks for the clarification.

OK... 27psi is around 1.8bar. On a standard block casing assuming a standard HG and standard bolts, your head gasket will not last very long.

Jolly Green Monster

iTrader: (4)

the answer is not boost but cylinder pressure.. which is obviously effected by boost but more so turbo size.

obviously a large turbo flows more air than a smaller one for the same boost and therefore you have higher cylinder pressures.. however it appears to be torque that kills the cylinder walls.. and obviously someone running 2bar is going to be doing so on a fairly large turbo and therefore it will spool later and therefore run less torque or similar torque to a medium sized turbo..

Some blocks seem to last longer than others and just seems to be luck of how it came out the cast.. there is little support from the ally block for the thin 1mm thick liner.. and therefore it moves and cracks and at worse actually breaks a chunk off which bounces around introducing itself to various parts of the engine..

On top of that you have head gaskets that do tend to fail possibly due to the cylinders moving..

I have been running 1.6bar with occasional higher boost on an ej257 block with md321t making 455lb+ with no issue for several track and dyno session and close to 40k miles.

Simon

Jolly Green Monster

iTrader: (4)

only difference to my knowledge between your engine and his Andy is he has 2.5 AVCS heads.. the make of pistons and rod maybe different but they all work just as well just he paid lots for the name, no offence meant by that Shaun.

Simon

Shaun

Simon,
You bang 2bar of boost (on my size turbo) through a standard 2.5 block case with standard cylinders on standard head gaskets and 11mm studs and tell me how long the head gasket lasts.

I was still using the standard head gasket and 11mm studs and it took 9500miles till the head gasket let go. Had I not had EGT problems early on and the car had not been pushed to 2.5bar and had the engine not been exposed to continuous dyno testing.... I suspect it would of lasted much longer. That set-up ran circa 2bar for the majority of it's life on the original Head Gaskets. Was used on track, drag strip and worked hard on the road. The car is not for shopping in.

My engine block whilst having standard cylinders, is not a totally standard case. It had been modified AFTER cosworth delivered it.

I will know more when the heads get pulled off next week, but even with the HG's gone, it pulled 500bhp at the hubs the other week. I suspect the rest of the engine is fine.

It would appear that it is a case of "when" rather than "if" the HG's let go on highly modded 2.5's.

Jolly Green Monster

iTrader: (4)

Shaun,

I am not quite sure which part of my replies you are referring to?

I never said it wouldn't fail at that.. far from it.


Simon

Shaun

I am not saying you have.... I was however highlighting that my block case is not standard, and would it of been, I suspect I would of had problems way before now.

Jolly Green Monster

iTrader: (4)

without disclosing what was altered whcih I presume you are not going to else you would have already we cannot judge that can we

Simon

Shaun

But Simon you don't need to "judge" anything. Quite simply the point I was alluding to was that I would not run 1.85bar which is what the OP was discussing, on a standard case, liner set-up, presuming standard HG's and studs were being used. I certainly would not do what I have done on the same standard set-up.... it wouldn't of lasted 10 minutes.

In you professional opinion.... would you?!?

BlooSooby

The engine has ARP head studs and non-standard HG.

At 21 psi the car made 240Kw (320 bhp) at all 4 wheels (not able to get equivalent crank power here in Brisbane).

Ambient air temp was around 30 degrees celcius.

Jolly Green Monster

iTrader: (4)

no.. lol

Jolly Green Monster

iTrader: (4)

has it been retuned for the higher boost?

was that a hub dyno or rolling road? assuming rolling road that is pretty good for at wheels.. I suspect pushing your luck at higher boost..

Interestingly Impreza tuning over with you used to be a big big thing.. what are others running?

Simon

BlooSooby

It was remapped with 21 psi boost on a rolling road.

I've put the original restrictor pill back in now and I'm about to take her out for a spin to see that boost has returned to 21 psi.

Thing is, the builder gave me the impression that the turbo wasn't capable of producing any more than 21 psi, obviously he's mistaken......or trying to keep the power levels down so there's less chance of blowing the engine (under warranty)

I'll discuss the matter with a reputable tuner but, tbh, I'm happy with the performance at 21 psi

Shaun

BlooSooby,
There is a whole world of difference between a turbo making anymore appreciable power at x psi and actually making x psi. In short, whilst the turbo may produce 27psi, that does not mean that is not just pumping hot air. Your tuner may be right. Check the turbo manufacturer to see what it is capable of running etc, with what ever setup.

Tidgy

after just looking at haivng a build done, i wouldn't have an ej257 pushed anywhere above 1.6 bar of boost, shgould still make 450bhp, but above that then you start to risk engine failure, yes people do run higher than that on them, but personaly i wouldn't risk it if you can't afford to have it rebuilt if it goes wrong

BlooSooby

Shaun.
The performance is noticeably improved since the boost increased to 27 psi, it's not just hot air. Also, the car seems to be running better generally.

I've now put the drilled out (1.4mm) restrictor pill back in and driven the car but the boost is still hitting 26psi, there seems to be no difference

I'm wondering if the ECU is still 'learning' the set-up of the car? I recently had to renew the battery and the car had no battery in for a day or so, doesn't this reset the ECU back to a default setting? Once I fitted the new battery the engine was only developing 17 psi but this has gradually increased over time.

AVO say that the edge series 450s turbo is good for 450 bhp but will only reach that with a FMIC, I'm running an APS TMIC and my set-up produced 390 bhp at 21psi which seems about right. AVO also show the 450s producing 21 - 24 psi boost on the dyno.

Shaun

Not sure why your boost is still hitting same boost targets if everything is OK boost control wise and back to what it was. Probably worth checking everything is on properly again (when was the new battery fitted?). It would be very dangerous to run more boost than originally mapped for.... if you have not had AFR's checked at the higher boost level, you need to. I may of missed something here as you may of had this all checked at the higher boost levels. Apologies if you already know this.

Regardless of all this I suspect you need to except, that should you continue to run 1.85bar on the block build you have, you may at some point get HG issues.

BlooSooby

Everything was checked and double checked prior to starting this thread. And besides, apart from failing to connect up the turbo/wastegate actuator/boost solenoid pipework ,what could possibly cause the boost pressure to increase??? Maybe I accidentally fitted a set of performance headers????? The battery is in the opposite corner of the engine bay.

The battery was changed over Xmas, the car has done about 600 km since.

I can't fully explain why the boost pressure has increased since changing the battery but the car is running really well, maybe (since the build) everything has bedded in and settled down????? **** knows!

Regardless, I'll have a chat with the builder this weekend prior to taking the car for a blast to see if he has any ideas. I can see how the conversation is going to pan out already......'Err, my Rexie is making too much boost and is running really well'.......'Great, don't forget to recommend me to your mates!'

When that doesn't work I'll call Arthur C. Clark

Shaun

The only reason I asked about the battery is I had a similar issue with boost control on my RS500 Cosworth. Boost was mapped to x psi and fine, but I had an issue with my battery. This was changed for a new one and the boost went mental. Apparantly the voltage difference was enough to cause boost control issues.

Was just a thought.

Jolly Green Monster

iTrader: (4)

lmfao.. thanks for the humour injection into my afternoon

joz8968

iTrader: (13)

...On on of them special 'afterlife' phone networks.

BlooSooby

Thanks for your input Shaun, I'm just trying to keep things light-hearted

BlooSooby

Spoke to the builder this afternoon. He suggested cleaning the boost solenoid in case it was fouled. Tried this, no difference.

He didn't seem overly concerned about the rise in boost pressure and said that the ECU will go 'open-loop' once outside the pre-mapped parameters, it will then rely on information from the sensors to determine the correct amount of fuel to shove in. Things should be ok, although he did say he'd talk to the tuner abour my boost increase and I should take it easy until he gets an answer.

He also reassured me that all his engines get stainless head gaskets...watch this space.