I was reading on Mazdatrix's website about how higher boost hurts an engine because of the increased stress, which makes sense. But my question is, does a bigger turbo, even with less boost, cause more stress because of the added air being forced into the engine? For example, does a T-78 at 12 psi place just as much stress on the engine as a TO4 at 16 psi if they were theoretically moving the same amount of air? Or is engine stress directly related to boost pressure? Just curious.

 

it is a combo of psi and HP which is the stress. be careful of your T04 vs T78, because it depends on the T04's specs, because it is possible to have a T04 which will flow more than a T78.

 

90% of engine failures are due to detonation regardless of boost or amount of power. Problem with higher boost and more HP is that you are more likely to experience detonation and thats the real killer of engines.

Just my .02c

 

Think about it. Higher boost means the intake air is compressed more, which means that it's hotter. Hotter intake air means higher risk of detonation. Detonation means new engine. Short answer, low boost on a big turbo is better for the engine than high boost on a small turbo.

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i took it as though he was asking with detonation aside

 

Thanks for your responses guys. BOOSTD7, isn't a big turbo on low boost still forcing a greater volume of air into the engine? I mean in theory, if Turbo A flows more air at 8psi than Turbo B at 14 psi, shouldn't Turbo A be putting more stress on the engine since its cramming more air into it? The air is still being compressed more even though the turbo itself isn't stressed. I like HWO's response of how HP, i.e. how much air and fuel, relates to engine stress. I was just throwing the question out there for the hell of it and you guys are right, detonation is 100 times more important than lame *** engine stress.

 

Take a look at flow maps. I believe it works something like this. Let say turbo A makes 8psi at 75% efficiency and turbo B makes 8psi at 60% efficiency. Everything else being equal turbo A is your better bet because it doesn't add as much HEAT to your intake charge while making the 8psi boost. I've seen ppl that have stock turbos with a certain boost pressure and they upgrade to a better turbo. Sometimes they will make more power with the same boost level because the turbo is more efficient. Remember, heating air creates pressure, too. If you have a sealed system, you can make pressure by putting a heat lamp next to it. Turbos can make "false" boost in the same way. Lower intake temps help ward off detonation. I believe that this is the real killer here. This is my take on this. I have been wrong before.
Don.

 

Unless they are dumb and go to a smalled turbo they will always see HP gains when going to a different turbo, example: common mod is to put a T04 compressor wheel onto the FC's turbo, replace tha T04/stock hybrid turbo with a complete T04 and use the exact compressor spec and size and you can gain like 60-80HP at the same boost as the hybrid was being run at.
I aint sure of the exact numbers but as far as Overall engine stress goes, running 15psi with a small turbo and making 260HP with it is probably similar to making say 380HP @ 12psi boost with a larger turbo

 

Gearhead is right about the efficiency. It's both the added boost AND heat that will shorten the life of your engine. The added HP will also create more strain on the entire car. An intercooler is one of the few add-ons that will actually reduce engine wear (assuming you keep the same HP level).

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88 RX-7 20B/T66 Money Pit
88 RX-7 TII Daily Driver
84 RX-7 GS Driving School Beater
00 F-150 Recovery Vehicle

 

detonation is what kills engines!
boost increases the amount of oxygen in the combustion chamber, which leans out the air/fuel ratio which makes detonation worse and as said it raises the air temp which makes detionation worse!

 

and that my son is what engine management systems are for, to ENSURE enough fuel is supplied

 

YEH!!
And the right person doing the tuning!

crispeed
87TII
9.74@139mph

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Yup, in the wrong hands, all a standalone does is make it about 10x easier to blow the motor. Some rookie starts messing around just to see what happens, and boom!

Proper tuning is the MOST important part of any install.