How much BOOST can a STOCK engine take??

SwarvJarv · 25-09-2006, 04:54 PM

I was reading an article in ford performance today, an there was a EF XR6 Ute, with a stage 3 CAPA SuperCharger Kit(9lb Powerdyne Blower, Water injector, EECU chip, Bosch blow off valve)...all else looked stock...

In the same issue there was an EA Ghia 3.9MPI was getting the same blower kit, but this motor was being rebuit to suit the blower (forged/balanced pistons + conrods, Crow cam, 30% bigger injectors, zorst system, 2 blowoff valves, valve springs, ported)...

What im tryin to find out is why didnt the XR need rebiulding(or did it?), and how much boost can a stock EA 3.9MPI take.....

EFFalcon · 25-09-2006, 04:56 PM

what about headgasket?

a mate of mine is running 12psi on an EL engine, only change is the headgasket to lower compression.
lots of ppl running around 10psi on stock compression or AU headgaskets.

BOOSTDEF · 25-09-2006, 04:59 PM

Ive been running around with 10psi on a stock AU motor with 9.6:1 compression. There are a few on the forums running around with 22+psi on the stock motor. For a daily this might be a bit too extreme but for mine, 10psi seems fine. The auto however is only JUST holding up.

The big secret to running high boost on your motor is the tune. If you have a nice safe richened tune you will be a lot better off than if you have no tune at all and run 9psi with the stock computer. It just wont last and its been proven not to. (BY My old motor)

SVT8 · 25-09-2006, 05:00 PM

depends on the condition of the motor, some can only handle 5-6 while others can handle up to 12.

XR Martin · 25-09-2006, 05:30 PM

Supercharger puts more stress on an engine so the boost it can handle would be less than if it had a turbo.

SwarvJarv · 25-09-2006, 05:33 PM

so...im planning on doin up a head(cam, springs, valves, ported, injectors, high fuel reg, chip), and if i was to strap one off these 9lb stage 3 blower kits (or mabey a bit lower) you reakon it'll handle it without better pistons or rods?
the motor is 250,000kms but in reco condition(quiet, smooth(at the front

: )).

FRDXR6 · 25-09-2006, 05:41 PM

Quote:

Originally Posted by XR6 Martin

Supercharger puts more stress on an engine so the boost it can handle would be less than if it had a turbo.

I always thought that superchargers (the powedynes at least) put less stress on the engine than turbo's...

BOOSTDEF · 25-09-2006, 05:44 PM

I dunno... The only stress i see turbos putting on is excess exhaust back pressure. This with a big exhaust would only aid in the rotating assembly?

Wheras a s/c would act the same as an air con/alternator? Putting load on the rotating assembly.

Im no pro but thats how i see it.

SwarvJarv · 25-09-2006, 05:46 PM

yea..the powerdyne use a kevlar internal drive, which is alot smother and alot more quiet, they dont even need to be plumed in to the crank case for oil....so i assume this would put less stress on the engine....

SwarvJarv · 25-09-2006, 05:46 PM

Quote:

Originally Posted by EFFalcon

what about headgasket?

a mate of mine is running 12psi on an EL engine, only change is the headgasket to lower compression.
lots of ppl running around 10psi on stock compression or AU headgaskets.

the worked EA had a decompression head gasket, but the XR was stockers..

matt_reynolds11 · 25-09-2006, 06:31 PM

Super chargers put less stress on the engine/drivetrain by the way power is delivered. In a supercharged car the power is linear, and the boost is raised as the revs rise. Turbo's can be quiet violent when hitting boost, resulting in increased stress

mik · 25-09-2006, 06:46 PM

Quote:

Originally Posted by BOOSTDEF

I dunno... The only stress i see turbos putting on is excess exhaust back pressure. This with a big exhaust would only aid in the rotating assembly?

Wheras a s/c would act the same as an air con/alternator? Putting load on the rotating assembly.

Im no pro but thats how i see it.

and if the turbo is not boosting theres no stress at all, where the blower is boosting most of the time.

TUFED6 · 25-09-2006, 07:10 PM

How long is a piece of string?

With the wrong tune, 1psi, with the right tune, 20+ psi.

Qwikcorty · 25-09-2006, 07:17 PM

Quote:

Originally Posted by matt_reynolds11

Super chargers put less stress on the engine/drivetrain by the way power is delivered. In a supercharged car the power is linear, and the boost is raised as the revs rise. Turbo's can be quiet violent when hitting boost, resulting in increased stress

violent for the gearbox diff tyres body, but not the engine if its been tuned ok.

NeishaXR8_347 · 25-09-2006, 08:00 PM

The main problem with the turbo is increased heat generated and these cars run hotter to begin with anyways, the first thing to go would most likely be the head gasket but if that doesnt go the rings will butt and causing a ring land to break and then say bye bye engine. But a safe tune is always good.

Shaun.