Turbo question

Mightyfordranger · May 26, 2016

Why is it that when a TURBO charged engine comes under a load and you throttle it up it builds boost I mean my Na motor up hill it slows down and won't speed it just runs outta ass pretty much even if I stand on it it won't it just bogs but I noticed turbo engines just push more boost and pull harder why is that??? I mean if the load slows the rotation of the crank it can't push more exhaust gas into the turbo so there for it shouldn't be able to spool any more right?? Or am I looking at it wrong???...just curious

alwaysFlOoReD · May 26, 2016

The turbo spools up with exhaust energy. That creates boost which puts more air into the intake. Add extra gas and more horsepower/torque is made and also more exhaust gas is made. Which adds even more air.... and it keeps cycling until you blow your motor or the excess pressure in the intake is relieved somehow, maybe with a blow-off valve.

Mightyfordranger · May 27, 2016

I understand the concept its just why does the cycle still continue when the engine is loaded so heavily to the point where the rotating assembly has no more ass to give it can't push any harder and yet it builds boost. I think I'm thinking to hard about it it's probably just as simple as you stated....hhhhhmmmm

alwaysFlOoReD · May 27, 2016

I'll try a different way. You "input" 1 and get a "result" = 2. Then you take the result and use it for input, so now 2 is input and result is 4. Do it again; input 4, result 8. Do it again, input 8, result 16. See where this is going? Unless you have a mechanism [like an unloader valve or blow-off valve] to stop the cycle, you keep making more power until something explodes.
This is a very simplistic explanation and turbos are not something I play with personally, it's knowledge I gleaned over the years. There are lots of variables including how efficient the spools are, what rpm the turbo starts working best, friction, etc. It's why throwing a big ass diesel turbo on a 2.3 probably won't work too well until rpms are too high to do any good. Or a turbo from a 2.2l on a 7.5 will run out of power very low in the rpm scale.

RonD · May 27, 2016

+1 ^^^

A turbo is an air compressor that uses exhaust gas speed and pressure instead of electric motor and belt drive

Turbo can get loaded down as well, effective boost pressure happens at a minimum RPM and up, exhaust gases have to reach a certain speed to effectively turn the "compressor" fast enough.
Turbos have Wastegates set to bypass turbo at high RPMs so you don't blow up the engine, lol, so you can set a maximum boost pressure, generally a spring loaded valve that is pushed open as exhaust pressure increases between head and turbo, stock turbos often use computer controlled wastegates to set maximum boost pressure.

While turbo increases HP it is a fixed increase so if hill is steep enough or trailer is heavy enough.........engine will still struggle as RPMs drop and boost pressure is lost.
Boost is a result of RPMs, as long as RPMs are keep up you will see boost pressure, but dragging a heavy trailer around in 1st gear to maintain high RPMs and 10psi boost is still a struggling engine, lol.

Same for NA, it has an RPM HP and torque range that you need to stay within to get best HP and torque.

Intercoolers are used because when you compress air it gets hot, hot air has less oxygen, is less dense(hot air rises), so less fuel can be added, intercooler cools the compressed air a bit aiding in increased horse power, like the cold air intake that all fuel injected Rangers have.

Mightyfordranger · May 27, 2016

Ok I see now it was the part where load comes into play that I couldn't quite grasp but I do like both of your explanations well put thanks :icon_thumby:

Turbo question

Mightyfordranger

Well-Known Member

alwaysFlOoReD

Forum Staff Member

Mightyfordranger

Well-Known Member

alwaysFlOoReD

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RonD

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Mightyfordranger

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