turbo_tracker

ok i need to know at what rpm does the 14b start to fall on its face. because everyone says it doesn't have top end but you honda guys get motors that like to rev and mine redlines at 6500 and its an auto so it rarely sees past 6k. also i would like to know at what rpm does the 14b hit full boost i know this has been said before but i figured i might as well include it.

bumblezc

My 14b has never fell flat at top RPM on my DOHC ZC that I rev to 7500rpm.

Sure a bigger turbo will yeild more power due to more CFM, but for the basic setup you will be happy with it.

shiznattik

It really depends on your engine and setup... a turbo that is small for one motor may be large to another.

I have a stock D15B (1493 cc) and I plan on running a 14B (largest I would even consider for now), and it's only going to be at max efficiency around redline... but for a larger displacement V6 it might reach max efficiency somewhere in the middle and start to fade out after that.

Give me a little more info about your engine and your plans for the car and I might be able to help you a little more...

IE. How many CC/Cubic Inches? How many psi are you going to run? Is this a daily driver, just trying to get a little more power out of it... or a road racer... drag racer.. etc.

Once you know all that you can figure out what turbo you want to get based on the compressor maps.

The rough estimate for MAX CFM = (CID * RPM * VE * .5) / 1728 [THIS IS FOR N/A]
cubic feet per min. = cubic inch displacement * redline rpm * voumetric efficiency of the engine * .5 (I think that's because the engine is only producing power every other stroke, but I could be wrong), divide by 1728 to get cubic feet
VE is usually around .85
So for my engine I went like this:
CID = 1493cc * .061 = 91.1
RPM = 7400
VE = .85

MAX NA CFM = (91.1 * 7400 * .85 * .5) / 1728 = 165.8

MAX Boosted CFM = NA CFM * bar

I think I am going to run 7 psi = (14.7 + 7)/14.7 = 1.48 = ~1.5 Bar
(14.7 is atmospheric pressure)

So MAX boosted CFM = 165.8 * 1.48 = 245.39 CFM

Then you look at the compressor maps, CFM on the X axis, 1.48 bar on the Y axis, where they meet is the MAXIMUM amount of airflow the compressor can produce at that psi. Also that point will be in a certain efficiency "island" -- look for a percentage next to the lines surrounding the point. That #% = how efficient the turbo is at that cfm and bar.

I'm not sure the answer to your second question, I know it depends on the turbo... probably an even more involved formula than the one I posted...

Hope that helps,
Scott

HMT-Admin

What engine do you have?

14b's fall on their faces on anything B-series and all stock DSM's on the high revs. Most D-series they work just fine.

95civic

Well on my d16z6 it never fell flat, but you could tell it was haveing a hard time around 6-7k at 10psi. If you like more topend and don't mind lag get a t3-so much better. If you have the turbo already I wouldnt make a big fuss about it though,also the turbo spools up fast and its nice you get power right away. 14b was done boosting by like 3-3500k? all i know is it was a fast spooling turbo.