Engine longevity with 1 bar VS 0.8 bar spring?

[bpu699]

So, how much life are you shaving off a motor by increasing to a 1 bar spring?

Assume proper afr/increased IC... stock motor.

Clearly the turbo has to spin faster...

Motor/pistons/valves/bearings/studs under greater pressure...

clutch under greater strain...

But what about the motor itself? Can you still get 100,000 miles out of it? 50,000?

99% of the time you arent driving at high boost...

what kind of longevity are you guys with modified motors running 1.5 bar getting?

[kenikh]

You need a baseline configuration. Stock engine? 3LDZ turbo? Early US exhaust, Euro exhaust, aftermarket?

1 BAR on a bone stock motor is not a great idea, as the backpressure from the stock exhaust and the 3LDZ turbo just aren't a good fit. Heat is your enemy and the previously mentioned issues, as well as stock timing and a crap intercooler compound the issue.

That said, a properly modified engine can last every bit as long (or longer) at 1 BAR as a stock engine at .8 BAR.

[bpu699]

Originally Posted by kenikh

You need a baseline configuration. Stock engine? 3LDZ turbo? Early US exhaust, Euro exhaust, aftermarket?

1 BAR on a bone stock motor is not a great idea, as the backpressure from the stock exhaust and the 3LDZ turbo just aren't a good fit. Heat is your enemy and the previously mentioned issues, as well as stock timing and a crap intercooler compound the issue.

That said, a properly modified engine can last every bit as long (or longer) at 1 BAR as a stock engine at .8 BAR.

My question was really just a general one... Personally, my car had a 1 bar spring/k27/sc cams/open exhaust/andial intercooler when I bought it. I downgraded to a 0.8 spring when I bought it, as the car was an unknown and I didn't want to grenade the motor... Plan to go back to a 1.0 spring this weekend...

Motor had 3% or less leakdown on all cylinders at 60,000 miles. The PO said it was rebuilt (lots of evidence to suggest thats true, but no reciepts), motor very solid...

[Rawknees'Turbo]

It's difficult to say to what extent engine life is shortened by using a 1 bar spring, but two things to consider are an increased risk of detonation (the effective compression ratio is raised quite a bit and good a/f ratio does not guarantee no detonation), and increased cylinder head heat (comes with the territory of increased compression), which will obviously reduce the life of the valve guides, etc., and further raise the risk of detonation.

[RarlyL8]

Most 930 engines don't or didn't last anywhere near 100K miles, that is more typical of a 911 engines life. Several reasons such as lack of maintenance, bad treatment, adding larger boost springs (with no other changes), and poor fuel curve. If you take care of the engine and add an intercooler to offset the added 0.2bar boost it will do OK. Change out the exhaust to fee flowing, tune the fuel curve and there is no reason why the engine shouldn't last 100K.

[kenikh]

Originally Posted by RarlyL8

Most 930 engines don't or didn't last anywhere near 100K miles, that is more typical of a 911 engines life. Several reasons such as lack of maintenance, bad treatment, adding larger boost springs (with no other changes), and poor fuel curve. If you take care of the engine and add an intercooler to offset the added 0.2bar boost it will do OK. Change out the exhaust to fee flowing, tune the fuel curve and there is no reason why the engine shouldn't last 100K.

My supposition is that all things being perfect, there's no reason a well maintained 930 shouldn't last as long as an NA 911. The issue is that there are more critical failure modes on a 930 and the outcomes from failure are much more dire. Whether it be a cracked vacuum line to the dizzy, a dodgy WUR, or any one of another of myriad issues - if anything goes sideways on a 930, the outcome is more often destruction than it is with a 911.