First i will explain my situation. I am thinking of a turbo upgrade because I want more power on pump gas. But I was thinking about it and i am only at about 70% the full potential of my current setup. Usually i drive with the boost controller off to save gas and only turn the boost on when im going to race. So i was thinking of going water meth instead but i dont want to unnecessarily hurt the longevity of the engine. So this may be a total newb question but here it is. Would there be any more stress on the engine with say a 450whp gt28rs@28psi with race gas/water meth setup than a 450whp gt35r@17psi pump gas setup so long as all things like heat and detonation were equal. Even if both these turbos are capable of more or less than stated hp/psi what im basically asking is does more psi put more stress on the engine or does 450hp equal the same stress no matter what boost level or turbo you're running.

 

Yes, there will be more stress on the engine pushing a smaller turbo at higher boost levels, which is getting the turbo out of its efficiency range and starting to produce more hot charge air. Also, a small turbo will put more stress on the engine because it will produce more efficient air at lower boost levels, which in turn produces more torque out of the engine at lower rpm.

With a larger turbo, but the same end result in hp you were trying to achieve with the smaller turbo, you will have less stress on the engine. The reason being because you dont have to push the larger turbo out of its efficiency range with big boost to achieve those same numbers you want. This will keep the turbo in its efficiency range and keep the turbo from pumping hot charge air into the engine. Also, the larger turbo will not spool quite as fast as the smaller hard pushed turbo and thus the low end torque will be a little less on the engine and less stress.

This is just the gist of it and hopefully it helps some.

 

in my car i can get better gas mileage by not mashing the throttle all the time, instead of turning down boost, have you tried that?

 

Lmao

 

Thats an interesting thought. Im a boost junkie what can I say. The problem is no matter what I always get on it a little bit when im leaving a stop. As soon as im pinned in my seat its like having an orgasm. So when the boost comes on strong for some reason i ring it out, then usually the next gear too. But when i run it on wastegate boost they creep open so the boost doesnt hit as hard or peek nearly as high. The car feels so much slower that I dont even stay in it.

 

I'm not a turbo guy so bare with me, but doesn’t a turbo actually help fuel mileage by helping to expels gasses when in vacuum/partial throttle say over N/A? As long as you stay out of boost isn’t it the most efficient?

 

You have a point, so, yea you COULD get better mileage in certain circumstances.

Now, the OEM designs, don't they lean out the fuel when the throttle isn't open? Also, fuel efficiency is a big design goal in OEM systems. After market, not so much.

 

Now, the OEM designs, don't they lean out the fuel when the throttle isn't open? Also, fuel efficiency is a big design goal in OEM systems. After market, not so much.
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Yes, OEM and aftermarket when at idle and partial throttle to aprox -5 vacuum, running a stoic fuel mix target and gradually richening up to about 13.5 - 12.5 afr depending on load in closed loop is the general tune. Obviously in Open loop you have a solid afr target in your richest afr setting. So logic tells me the turbo helps expel the gasses better in the vacuum range over N/A where your fuel % is low, mileage I think would increase.