Nope , wrong . You want to go a research how a four cycle engine works and what the dynamic compression ratio really is .

I'll save you the trouble .

The less restrictions there are in the inlet tract the better the cylinder filling is on the induction stroke . If you could get the mythical 100% charged cylinder and not lose it to any significant leakage anywhere then the dynamic or effective compression ratio would be the same as the measured one ie a ratio of the swept volume to the clearance volume .

So when you have very low restriction throttling such as individual per cylinder ones you stand a better chance of getting a more completely charged cylinder .
When you do so there is more air to compress within the cylinder meaning the dynamic or effective CR HAS to be higher .

Now lets assume you want a higher effective CR and don't have the means of raising the static CR , if you find a way to better charge your cylinders ie with ITBs then the effective CR will rise , this assumes you have adequate paths upstream of the throttles .

Now throttle response , yes it improves with ITBs and the reason it does is because it gives less restriction than a single one does ie better cylinder filling .
Turbo response , I should say turbine response , is not the same as throttle response . Is is possible to have good throttle response and **** poor turbine response .
Where ITBs and a higher effective CR helps is that more air burnt with more fuel gives off more exhaust energy and THATS what drives the turbine and compressor wheels up to speed .

If you look you'll find that many dedicated competition engines and a few homologation production engines use individual throttles . The turbo ones that come to mind are Nissans RB26 and GTiR spec SR20DET and off the top of my head some of the NA BMW M3 engines .
I think universally F1 engines have used them for ages including the 1980 - 87 F1 turbo era .

Believe what you like .

 

Care to quote Heywood where he uses throttle loss in his equation for Dynamic Rc?

I think you're confusing DCR with VE.

 

Before we get too sidetracked, I feel it's safe to say that the primary reason for improved response with ITBs comes as a result of the proximity of the throttle valve to the port, which shortens the distance/volume between the port and an air source of higher pressure (ambient or greater). In instances where the throttle blade and valve itself was deemed to be a significant obstruction, the solution was slide throttles (e.g. BMW turbo F1). In both cases, what's happening is that abrupt changes in throttle position result not in higher DCR, but in the rate at which DCR reacts to the rate of throttle position change.

Whew.

 

Keep CR low for years of boost pleasure.

 

As well as a motor that runs hotter, gets lower fuel economy, and makes less power at a given boost level.

I don't know why anybody would care about "Dynamic Compression Ratio" in the way it is being talked about? Once engine speed gets above cranking speeds, that number means almost nothing.

Air charge inertia will have dramatic impacts on cylinder filling. Cam timing is only one small fraction of the overall picture.

 

A lot more heating of the combustion mixture happens in a high compression engine. I would assume that controlling your IAT's is more critical with a high Rc engine.

 

Previously stated about me looking into the black, I have and I like the results for the money.

Back on topic though, so going with 9:1 would be better for my engine at my elevation? i'm at about 6k elevation.

 

no, at higher elevation you want higher compression.

 

I've run both 10:1 and 11:1 motors in the Denver area and above. For a street car, I'd say you can't go wrong with 10.0:1 ... if you are running E85. If you're on 91, I'd probably suggest sticking with 9.0:1.

Dave

 

so did we all come to a consensus?

My question would be if running E85 all of the time and given a smaller setup wouldn't a higher compression 2.0 motor be better all around over a lower compression 2.3?

or if I may (mitsu related but not evo) A 1.6liter 4g61 turbo with somewhere in the 10.0or11.0-1 CR over a 2.0 with 7.8-1 both on E85 and a 20g and reving to 8800rpm with fp2's. Wouldn't power be either the same or higher and drive-ability (off boost power) be similar with the smaller high CR motor? any input would be appreciated, thanks.

 

The 2.3L is going to have more power off boost then the high compression 2.0L. It is 15% more volume and the longer stroke produces more mechanical advantage at a given cylinder pressure. When the turbo isn't the restriction, that will make a significant difference in power.

The 2.3L does seem to choke pretty badly on the stock turbine housings though and the 2.0L would likely make a decent amount more power once the car is into boost and getting near the limits of the turbo.

 

tnx for the replies...great info!