Compression vs. Boost

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Originally Posted by r.barn

There is no answer to this question

Too many variables.
static compression
dynamic compression
aluminum or iron heads
intercooler or no intercooler
type of intercooler
fuel
tune
boost level.
compressor efficiency
ect
ect
ect.

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I believe most of this is pre determined in the OP's case.

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Originally Posted by ATX ENGINE MAN

If its primarily a street vehicle, I would run the most compression I could that would still allow me to hit my power goals on the chosen octane under boost in the given app. That would give you a more responsive engine out of boost, also more efficient. But, by going on the lesser compression side you have way more room for error with the tune under boost, less chance of timing being pulled and you have the capability to make more overall power with the fuel being the limiting factor. Its all about the particular combo in ? and what your after.... :twocents:

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I would have to agree with him because I built my 6.0 for a lot of boost so it's compression is 8.8-1 I do wish that I would have gone like 10-1 because it us a daily driven truck and I would have rather had more compression and less boost but it is just because before the turbo kicks in it is a dog

most ppl arent sure what they want to be honest. ppl toss a turbo on a stock motor and run X amount of boost and then it mishaps. then they go and listen to the rest and say drop the compression. now they run the same amount of boost as they did before and wonder why the vehicle is a dog. less compression allows for more boost. Heres the key tho you want the least amount of boost as possible. less cylinder pressure the better the outcome. build your motor for most power NA then apply boost but take into account what fuel will you be using, what temps will you see and etc.

you can boost 11.0 all day long but you got to be smart. low timing, good fuel. or you can run meth and little more timing. so many variables.

now with a vehicle with compression off boost will be much more snappier and with compression will spool the turbo faster. low compression motors are complete dogs off boost but once boost applied is when you see it come alive. another thing comes into play is displacment. a much larger motor will be more prone to higher cylinder pressues then a smaller motor. the amount of volume filling hte cylinder is always the factor. my 4.8 can see 19psi daily without a blink of eye on 93 octane only...i have a cam that bleeds off compression and im already low on compression to start. also have a larger intake valve to help all this. push 19psi thru a 6.0 with a ls6 and use only gas with 24* timing and see how long it lasts. that cylinder pressures of the 6.0 will be so much greater then the 4.8 youll lift the heads or detnoate alot sooner.

also in picking your motor setup. dont worry about what psi you run. psi is only a measurement of restriction. the key word here is VOLUME. the more volume you fill cylinders is wher your power comes from. that is why 16psi from this setup isnt no where near 16psi of that setup.

plan a power goal, plan a use of vehicle and take the approiate actions to reach your goal in mind

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Originally Posted by ATX ENGINE MAN

If its primarily a street vehicle, I would run the most compression I could that would still allow me to hit my power goals on the chosen octane under boost in the given app.

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+1

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Originally Posted by r.barn

compression should match intended boost level ........... done.

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+1

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Originally Posted by Quik

dont worry about what psi you run. psi is only a measurement of restriction. the key word here is VOLUME. the more volume you fill cylinders is wher your power comes from.

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This is key, you want Flow and Volume high and boost level low. A lower boost level will generate less heat. Less heat means more air molecules in the cylinder and the more fuel you can add to get more power.

If you can make X amount of horsepower at 10PSI, or make that same X amount of horsepower at 7PSI which is going to be better.

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Originally Posted by trx2stroke4life39

This is key, you want Flow and Volume high and boost level low. A lower boost level will generate less heat. Less heat means more air molecules in the cylinder and the more fuel you can add to get more power.

If you can make X amount of horsepower at 10PSI, or make that same X amount of horsepower at 7PSI which is going to be better.

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i agree completely. less boost is less heat. when you compress air it heats up

but with anything else ppl love to speak of how much PSI they run to brag for penis rights

8:5.1 comp and 30+psi and smile

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Originally Posted by TMC

8:5.1 comp and 30+psi and smile

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you do u think i have 6.0 heads on my 4.8 :)