Evo3 maximum boost original piston

[Karapok11]

Hi all,

can I verify the maximum boost pressure the original evo3 block and piston can take?

Heard its 1.2bar... but what do they mean by that? In terms of original ecu, fuel pump, injectors everything?

If I were to put in a piggyback, fine tune it with upgraded injectors and fuel pump and setting of appropriate fuel pressure, will having a constant healthy Air fuel ratio still cause any deterioration to the pistons?

Can I go above 1.2 bar with the stock pistons?

 

[edwin_lcw]

i dun tink so ..... now its like .8 - 1 be ma ..... i heard my friend saying pistons onli can make it to 1.2 bar ..... i dunno heard of it onli ...

 

[RJ_5847]

but i heard some technology from dunno which manufacturer r able to hit 2.8 bar pressure by tilting d cylinder blocj by 4 degree...

 

[MitonCT26]

but i heard some technology from dunno which manufacturer r able to hit 2.8 bar pressure by tilting d cylinder blocj by 4 degree...

hah????

 

[khoyos]

IMO, the weak link in evo block is not the piston, its the conrod.

 

[RJ_5847]

yep true...

Variable Compression Ratio - Saab SVC
Saab has stunned the world by showing its variable compression ratio engine in the 2000 Geneva motor show. I’ve heard such engine for some 2 years, but this is the first time Saab disclose the details to the press. In my opinion, this is perhaps the largest single breakthrough in engine technology since turbocharging and electronic engine management.
Why is variable compression ratio so fascinating? As everybody knows, fixed compression ratio is always a constraint for supercharging or turbocharging engines. To prevent excessive pressure in combustion chamber, hence pre-ignite ("knocking") and overheat to cylinder head, turbo/supercharger engines always employ a much lower compression ratio than normally aspirated engines so that the total pressure won’t exceed the limit when the boost pressure is added. The problem is, when the charger (especially is turbocharger) is not yet getting into full boost, that is, at low and mid rev, the combustion runs at lower
compression ratio than normally aspirated engines. Therefore power efficiency at low speed is even lower than normally aspirated engines.

As seen, the SVC engine have a cylinder head with integrated cylinders - which is known as monohead. The monohead is pivoted at the crankcase and its slope can be adjusted slightly (up to 4 degrees) in relation to the engine block, pistons, crankcase etc. by means of a hydraulic actuator, therefore the volume of the combustion chamber (when piston is in compressed position) can be varied. In other words, compression ratio is also variable.
SVC is cleverer than any previous patents for variable compression ratio engines is that it involves no additional moving parts at the critical combustion chamber or any reciprocating components, so it is simple, durable and free of leakage.

The monohead is self-contained, that means it has its own cooling system. Cooling passages across the head and the cylinder wall. There is a rubber sealing between the monohead and engine block.

The VC allows the Saab engine to run on very high supercharging pressure - 2.8 bar, compare with the latest 911 turbo’s 1.94 bar, or about twice the boost pressure using by 9-3 Viggen. So high that today’s turbochargers cannot provide. Therefore it employs supercharger instead. At other speed, the VC is adjustable continuously according to needs - depends on rev, load, temperature, fuel used etc., all decided by engine management system. Therefore power and fuel consumption (hence emission) can be optimized at any conditions.

 

[cyborgsabah]

IMO, the weak link in evo block is not the piston, its the conrod.

yup.. i agree... its not the piston.. with metal gasket to lower down the CR, proper tuning (at least piggyback) and other supporting mod such as fuel pump, adj fuel reg, etc.., evo stock internal can go for 1.5 bar without problem...

 

[MitonCT26]

we're talking about mitsubishi or saab here? 4G63 right?

damn bad hangover from yesterday's night bash....

 

[Cannonfodder]

Weakest part of the early 4G63 is the in the conrod bearings and thrust washers. When you run higher than standard boost, these are the first parts to fail, causing crankwalk.

There's also nothing you can really do about these two parts, it's an inherent design flaw that was only minimised with the later engines. If you want to run high boost pressures, take off your oil pan every other oil change and inspect the bearings for wear. PITA, yes, but better than a blown engine.

The pistons are also rather brittle, tending to crack under higher boost but you can always get forged units.

 

[cmng]

evo stock internal can go for 1.5 bar without problem...

err your assumption mean Evo engine can go to 1.5 bar on
HKS T51R SPL BB turbo
Trust T88,
Garret GT42 Turbo ?

 

[jinkl]

hehe , there is a evo in zth, evo II if not mistaken running 1.6bar with good fueling, with metal gasket of cos

havent snapped , touch wood

i also do tink the evo piston compression is nice
bt the conrod is like a lidi man hahahahaha not like a batang lolx

if i could reverse time :P e3 pistons anytime hahahahha

cmng : yeah , i tink we mean the td05 haha , sure CFM of other turbines will be even higher rite sifu

 

[jo1]

The weak link is the conrod…. Higher compression will allow you to running lower boost pressure but get the same power (VR4 vs EVO)…… just slap what ever turbo you want be it t51r, if the tunning is properly done it will not blow an engine. It been tested than an evo engine can hold up to 4++hp in other continent…. Maybe not for evo in malaysia because Malaysian always undermined their capabilities.
But, if you install a t51r to a std engine it will be a waste…. How much the std engine cost maybe 10% of the t51r price.

 

[dolly]

stock e3 @1.4 bar... survived 2 laps of sepang before i realised my boost controller was screwed up :P

 

[cyborgsabah]

early evo engine is much stronger than most ppl think.. but dont boost too high lar... i'm running 1.5 bar on my e2, it run just fine... if you run no more than 1.5 bar, i think even with bigger turbo also ok...

 

[Karapok11]

Weakest part of the early 4G63 is the in the conrod bearings and thrust washers. When you run higher than standard boost, these are the first parts to fail, causing crankwalk.

There's also nothing you can really do about these two parts, it's an inherent design flaw that was only minimised with the later engines. If you want to run high boost pressures, take off your oil pan every other oil change and inspect the bearings for wear. PITA, yes, but better than a blown engine.

The pistons are also rather brittle, tending to crack under higher boost but you can always get forged units.

So its the conrod and components that comes into the picture. Often read about people talking bout the piston and I just thought its really because the piston rings gave way or something related to pistons. Thats why I am skeptical bout the truth cuz if proper tuning and fuelling is in place, pistons should be in good shape.

Since its the lower half of the block thats the issue, then it might be good to follow the advise from the experts/those that has went thru the process of going around not more than 1.2bar boost.

But just a side question, anymore fellow evo3 engine owners running more than 1.2 bar boost with stock conrods, crankshaft and pistons etc and going fine?

 

[jo1]

Weakest part of the early 4G63 is the in the conrod bearings and thrust washers. When you run higher than standard boost, these are the first parts to fail, causing crankwalk.

There's also nothing you can really do about these two parts, it's an inherent design flaw that was only minimised with the later engines. If you want to run high boost pressures, take off your oil pan every other oil change and inspect the bearings for wear. PITA, yes, but better than a blown engine.

The pistons are also rather brittle, tending to crack under higher boost but you can always get forged units.

are you sure higher boost cause the crankwalk?
cranwalk is something to do with the crankshaft and drivetrain, if you'r talking about 4G63T engine. Mostly occured to the DSM variant which produce in US.... and never heard of any from JDM evo siries..... maybe i need to google more???


The EVO piston is stronger than VR4..... it is a cheap upgrade for VR4 to use an EVO piston and it good for 4-5++hp if properlly install and tune. but don't use an EVO turbo if you aiming for 4++hp because it max flow is around that region unless you a hell of a tuner...

 

[jinkl]

jo1 : which piston did u mean , e3 high compression or the e1,e2's

 

[jo1]

the lower the compression the higher boost you can run.....
what boost you want to run is depend on the effeciency of the turbo, certain turbo required you to run higher boost to show their true color...

as for evo piston i will choose e3 if i can get it free.... if not use stock engine only.

 

[Cannonfodder]

Yeap, crankwalk on the 4G63T used in the Evolution I to IV. Lots of complaints from early Evolution owners in Oz. NZ, and UK.

It's the same design flaw, the same that affects second gen DSMs, and is claimed to exarcebated by the stress of running higher boost.

Same with the pistons. Early Evos found to have cracked pistons (running standard boost) when head removed for head gasket or valvetrain repairs.

 

[jo1]

what can i recall from the owner of 2nd gen. DSM the dealer claimed that it is because of the used of aftermarket clucth system ... but it also occured to the OEM clutch user..it maybe because of the smaller and lighther design for the EVO or 2nd generation engine. For evo iv and above i never heard any complaint about that yet.