Some engine volumetric efficiency calculations, more added

[bemis]

With the dyno sheets in hand, I calculated the engine volumetric efficiency's of the stock VG30, VG30 NA2T T3 turbo, and stock VH45DE.

First, I selected 5 specifc RPM locations and calculated the BHP using a 15% drivetrain loss. For the NA engines, this was based on only RPM increments of 1000 till redline, but the fifth RPM was HP maximum. On the boosted VG, I used boost threshold as the first RPM, the second RPM point when boost reaches set maximum, the third was whatever, the forth was HP maximum, the fifth was redline.

Using the Ray Hall's turbocharger compressor calculator, I then input all the data.

For the boosted model, intercooler was set to 85% and max boost was set to 9psi. I selected the T3 60trim compressor map (because that is what it is) and corrected the compressor efficiency based on where the RPM dots lie.

For the NA models, intercooling was deselected and boost was set to 0psi. The compressor efficiency's was set to 100% since there isn't such a factor. Nevermind the compressor maps too, they dont matter here.

I then selected the volumetric efficiency of each RPM until its calculated HP matched the dyno'd HP to the crank.

This is what I got.

VG30, pathfinder intake


VG30 NA2T T3 turbo, pathfinder intake


2000rpm, efficiency is down because the turbo is now a plug in the system until it reaches max boost.
all the way to redline, efficiency increases due to forced induction
redline, efficiency drops dramatically due to SOHC design and climbing exhaust backpressure due to small turbine. NOT because of compressor efficiency.

Note: raising the VE at redline to 75% netted an increase in BHP by 70. this can be accomplished by stage one cams and lowering exhaust backpressure.

VH45DE


absolutely amazing, 100% efficiency at 4000RPMs
the dive in efficiency at redline is very clear on the dyno too. it just dies after 6000.
This engine can make 400WHP on just 10psi of boost too.

1984 VG30ET, stock intake



18lbs boost, non-intercooled, meth/water injection
114% VE at 3000rpms, mostly because of no intercooling system. non-intercooling FTW for VE, but not for overall HP.
Still, the compressor is not completely out of its efficiency range as once thought.


Obviously, for those "technically minded critics" out there, there are other factors to think about. This was not meant to be a set in stone judgement, but a good indication of where the engine sits at in VE.

I did this because I had a hard time believing that the VE of an engine remain linear through the RPM band, as most people believe. They are clearly wrong.



I have more to come, such as Stinky's stage one cam VG30ET with a holset, VG30DE, and Kyle's 400WHP black bitch.

[MrwassmanNA2T]

I have never seen VE charts like this. Very interesting, and I am pretty sure i actually understand what is going on.

Thanks for the info.

So are you expecting to get closer/to 100% VE with cammed Z?

[Jason84NA2T]

Re: Some engine volumetric efficiency calculations I have do

That's interesting to see. I figured I would say thanks and comment on this:

bemis wrote: I did this because I had a hard time believing that the VE of an engine remain linear through the RPM band, as most people believe. They are clearly wrong.

No, as we know VE most definately does not remain linear. I have a hard time believing someone would think VE is a static value for all RPM. That's pretty much why you have a VE adjustment for speed density systems and VE charts for OEM/performance engines from the factory. Seeing engines that exceed 100% VE wihtout true forced induction is what I find impressive.

That's effectively what changing the degreeing on cams (or cam timing) does... shift the VE curve higher into the engine's operating range.

[G-E]

I experimented with an engine simulator as well, I had similar results, basically if I ever entered a fixed VE% for the engine the numbers would be all wrong, the torque curves will never match

and logically airflow changes with speed in a restricted system, every bend, corner, bump, and splitter will change the way the air moves differently at different speed..... much like mountains and trees affect wind and weather

[bemis]

Re: Some engine volumetric efficiency calculations I have do

Jason84NA2T wrote: Seeing engines that exceed 100% VE wihtout true forced induction is what I find impressive.

Actually, the VH45DE does exceed 100% VE at 4000rpms. Its more like 102%. But I settled with 100% instead, about a 10hp difference.

[bemis]

MrwassmanNA2T wrote: I have never seen VE charts like this. Very interesting, and I am pretty sure i actually understand what is going on.

Thanks for the info.

So are you expecting to get closer/to 100% VE with cammed Z?

The closer to 100% VE you can get the engine, the more power you get. Lets just say that increasing the VE by 1% is an increase in about 5hp.

Also, exhaust manifold pressure in any application, turbo or not, is a HP killer for engines. You will see ungodly numbers from any set up if you can get your exhaust manifold pressures lower than your intake manifold pressures. I'm qouting this from Corky Bell too.

[bemis]

edit: I stated that for the boosted VG30, that the redline VE plunged because of the small turbine. actually its more correct to say that the turbine is not matched for the flow requirements of the VG30 at 6000RPMS. It actually better matched for exhaust flow requirements of the VG30 at about 4000 rpms.