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No. Wrong Wrong Wrong. Do not say things that - you'll confuse people.
6 psig on a 9:1 engine is NOTHING LIKE an N/A 12.7:1 engine.
Compression ratio is not related to manifold pressure. It is very much related to static compression ratio and valve timing.
For example, miller cycle engines hold the intake valve open until the piston is half way up, allowing them to run a 14:1 expansion ratio, while only having an effective 7:1 compression ratio (as half the charge has been pushed back into the intake manifold).
Ich gehöre nicht zur Baader-Meinhof Gruppe
Originally posted by Top Gear
Every time you buy a car with DSC/ESC, Jesus kills a baby seal. With a kitten.
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heres some pics of the turbo/intercooler.
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Cool. how much torque do you get out of that now?
Those intake runners look like they never end from that angle.
Ich gehöre nicht zur Baader-Meinhof Gruppe
Originally posted by Top Gear
Every time you buy a car with DSC/ESC, Jesus kills a baby seal. With a kitten.
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Donesoldout, that looks nice and clean :D
Um, yes yes yes. Your effective compression IS dynamic, and for you to say it's 7:1 is wrong - that will only be the case when the piston is at one particular position in the cycle. I have software that calculated cylinder pressure for every degree of crank rotation.
Also, late IVCE (intake valve closing event) has been found to more relate to cranking pressure than overall dynamic. When the engine is at operating speed the air is moving too fast for the entire charge to be forced to make a 180* turn - and what you are talking about is called reversion which this software also calculates based on intake, runner, chamber and cam design. You think the amount of air going in the chamber at or above the speed of sound can just suddenly go backwards? Imagine using an air compressor blow-off tool and you trying to reverse the air coming out using a box fan, yeah some of the air will be (re)diverted, but a majority of it will pass right through the fan.
Even when I put heads on the flow bench and am only testing at 28", you wouldn't believe how fast that air is moving, and it still doesn't replicate real life engine pressures.
Here's a cheesy online calculator : http://www.dragsource.com/index.php?...s&calctoview=3
It's not near as advanced as the software here, but it gives you an idea. If you dynamic/effective compression was not raised in boost, then why do we need more fuel and have the risk of detonation? By forcing more air in, you ARE raising the compression ratio effectively. By adding more atmospheres to a combustion cycle (ie 14psig pressure), you have doubled the amount of air that entered that combustion cycle causing higher need for fuel, increasing compression, and increasing chances of lean condition (that are actually amplified).
Besides if you re-read my original statement, numbers were just made up to use as an example. A turbo kit I built not long ago had 9.1:1 static and was nearing 18psi max dynamic compression - he snapped the transmission at almost 400hp on the dyno (FWD transaxle FTL) but after a fresh one was put it ran 12.9@113 spinning the first 100' (2.2 60') in a 3000b car.Comment
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You are apparently unaware as to just how late the valves close on a miller cycle engine.
Are you aware of the miller cycle? Used in virtually ALL large stationary NG engines, which frequently run at a 14:1 expansion ratio?
The whole point of using a miller cycle engine is to do as much of the compression as possible with the supercharger, as they're more efficient compressors than the engine is, remove the heat, and then have a higher than normally possible expansion ratio to get more mechanical energy out of the fuel.
The intake valves close very late on a miller cycle engine, far beyond the point at which cranking becomes easier.
Well for one, compressing air makes heat. compressing hot air adds more heat.
Changing VE (you could see 7psig at the port at the right engine speed on a well tuned intake manifold), just means you're increasing VE, it doesn't mean that the combustion chamber is smaller now that you put more air into into the cylinder.
An engine with a 9:1 expansion ratio is still an engine with a 9:1 expansion ratio, be there 10" of vacuum in the manifold, or two atmospheres in the manifold.
Perhaps we should be talking about compression ratio and expansion ratio separately.
I fear we may be talking about slightly different things in slightly different ways. I'd be happy to argue until we're blue in the face (or not confused) via PM.
18psig at the intake port? I sure hope your compression numbers are higher than 18psi.
Ich gehöre nicht zur Baader-Meinhof Gruppe
Originally posted by Top Gear
Every time you buy a car with DSC/ESC, Jesus kills a baby seal. With a kitten.
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bottom end is stock but has
polished crank
honed cyl
new bearings, gaskets, rings, etc
top end
head was port/polished
new springs
new head gasket (stock)
arp studs
intake
2.5 charge pipes
24x9 intercooler
cleaned up intake ports to match head ports
widened throttle body port to match i trottle body
turbo/exhaust
ebay manifold modified for 38mm tial
turbonetics bb t3/4 hybrid .63 ar exhaust 50trim comp
full 3" mandrel bent exhaust, no cat or muffler
etc
36lb injectors
remote filter and oil cooler
megasquirt II, bg 2.8 codeComment
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what are the thoughts of running 12-15psi on a 14g on an all stock eta motor?Comment
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For what it's worth, we have a turbo eta at the shop now with no internals, badly tuned MS, and a T3/T4 at ~13 psi, and it dyno'd 208 hp and 280 lb-ft. with a good tune, it would be a heck of a fun, cheap setup.Comment
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