Volumetric Efficiency Question

[GNDriven]

I am trying to run some turbo calculations vs power capabilities.
The engine is hardware capable of 800fwhp. I know the robotic choice is the hpq70, but I am trying to at least take a survey.

Does anyone have any documented, empirical, or educated guess as the volumetric efficiency numbers for the stock 231 as if it was naturally aspirated? All the turbo selection models I have found require a volumetric efficiency for the engine N/A.

Also I have GN1 full race port heads and intake, how much does this increase volumetric efficiency at 14.7pisa? My goal is to move enough air to make 800fwhp. Getting the air required (lbs/min) is easy, same for every engine, but figuring out the pressure ratio…then the density ratio…requires some good estimation of the volumetric efficiency of the engine non-supercharged.

On a stock engine, what rpm does the VE reach its highest point?
The stock engine should provide a base line for me. I can kinda calculate what rpm direction VE will go with different cam choices and such.

P.S. Does Precision release compressor maps on their turbos?
Thanks

 

[Chuck Leeper]

Max VE occurs at max torque.

 

[GNDriven]

Yep,

Max torque is when VE = Max.

Maybe I can study someones DYNO sheet.

Anyone have one you can post, with setup?

Thanks.

 

[Turbo6Smackdown]

I'm not trying to be a jerk or anything, but... If you find the answer you're looking for, or you don't find the answer you're looking for, what are you going to do about it?
There's only a few options available, when talking about 800 horsepower. We're talking big turbos, rock solid bottom end, from forged internals, and either a girdle, or billet steel main caps, front mount ic, alky, reinforced suspension, race heads, intake, doghouse, big tubing, etc etc. Whether you know this magic number or not, you're still going to have to do the minimum stuff, which, for 800 hp, is quite a lot.
Basically what I'm saying is, just follow the basic requirements, and focus on your tune, and that's all you can really do. Stuff like a WB O2 setup, power logger, egt gauge, maybe, a fast, or big stuff etc etc.
Stick with the basics, and do your part, and don't worry about the obscure stuff. Keep it simple.

 

[GNDriven]

The car/engine is setup to handle 800Hp, now its time to take a turbo survey of what is available.

The engineer in me whats to conduct full analysis (at least the best I can), since I majored in electrical engineering, learing the fluid dynamics and mechanics is requiring a learing curve.

I do like to keep things I am not interested in simple, but I enjoy this stuff, hence the questions. I know some of the more modern day engines are close to 95% VE N/A, would like to see if anybody has looked into what it is on our engines.

I would imagine all professional tuners know %VE at what RPM the engine they are tuning is designed for.

 

[dr_frankenstein]

I have always used an 85 to 93% rating when ive done that calculation... Are you using Turbo Calc? if you are I would say its safe to use 90% for its VE due to the fact its a fairly modern turbo engine.

Ive used this and had OK results.

A.j.

 

[GNDriven]

Did you use those percentages for the stock engine or a modified 231?

What rpm do you think the VE is at max for a stock engine?

Thanks

 

[dr_frankenstein]

I went at those percentages ASSuming a mild performance build..... i figure that a stock 87 engine should fall in around the 85% range - considering its size and power output.... now for my Modded engine, I went with the higher 90 to 93% range.

But I cant honestly say what a target VE for RPM is on a Stock 87 as I have never run or tuned one... my turbo calculations were Based using the buick in a blow thru Carb appication. But I do understand your fusterations with using the Program, as they ask alot of variables that are very hard to define. The way I learned to look at it is, i have to make a combination of educated guesses and choices about what i want.

for example, they ask for VE through out the entire RPM range, listing up to 6 points for the variable that include boost pressure, intercooler effciency, ambieant air temp, bla bla..... I filled in what I wanted, and used the Program more as a recipe than a tried and true calculation program... Does that make any sense?

So i would say i want X number of lbs of boost here, at this RPM with an ASSumed VE of such.... and i would create the numbers that i wanted.... the end result being the target combination to build.

I know thats a really wrong and incorrect way of using the program, but i have been successful with that method... Turbo Calc is just a hard program for the DIY use.... theres alot of variables that are not easily known at home.
I dont know if that helps your questions at all....... but feel free to tell me a better way!

:tongue:

A.j.

 

[GNDriven]

Actually is does help.

I am coming to the conclusion rarely this is an exact science.

I am learning there are people that are very knowledgeable on various combinations (this turbo with that converter type) and those that engage in the science of a combination.

I am sure each approach will yield results. But what about Bob Norwood that builds turbo systems from scratch? I am sure Precision does not hand him a turbo and go "here use this" and he does so without knowing all details.

I am using the TurboCal program to help calculate air mass/flow needed for certain horsepower and which turbo is good fit. This program has a cool setup of showing different compressor maps and automatically plotting your air requirements across the engine rpm band.
I am checking the program’s results with equations and principles taken from Jeff Hartman’s book.

But almost every equation requires an assumed N/A volumetric efficiency.
Just wondering if anybody has tried to nail down what it is for our Buick LC2.

 

[dr_frankenstein]

LOL.... hit the nail on the Head Boss! but im sure one of our more high end builders around here .............**cough cough** (anybody out there) should be able to atleast point you in the right direction for the LC2.

I agree that there is a correct way of doing this as you stated - nobody is just given a turbo and builds all kinds of horsepower.... but I wish there was a more resonable method of finding that information.....

I love Turbo Calc........ just a PITA to use for me...... or maybe im just a crappy engine builder!

LOL:redface:

A.j.