whats the volumetric efficiency of a tdi engine

BlakGolf · October 25th, 2006, 09:19

getting some progress done today, im off from school and trying to pick a turbo. im looking at the compressor maps. whats the aproximative VE for our engines?? im thinking 75% tops. anyone have a idea?

pruzink · October 25th, 2006, 09:32

“Volumetric efficiency. The volumetric efficiency of an engine is the ratio of the volume that would be occupied by the air charge at atmospheric temperature and pressure to the cylinder displacement (the product of the area of the bore times the stroke of the piston). The volumetric efficiency determines the amount of air available for combustion of the fuel, and hence influences the maximum power output of the engine.
Volumetric efficiency is actually the completeness of filling of the cylinder with fresh air at atmospheric pressure. The volumetric efficiency of an engine may be increased by enlarging the areas of intake and exhaust valves or ports, and by having all valves properly timed so that as much air as possible will enter the cylinders. Since any burned gases will reduce the charge of fresh air, the supercharging effect gained by early closing of the exhaust valves or ports will reduce the volumetric efficiency.”
If you want to work the math, the Bently manual lists the stroke for the BEW engine as 95.5mm, and the bore as 79.5mm with a compression ratio of 19.0:1.

diesel des · October 25th, 2006, 09:40

At what rpm?? At 2K you could assume 90% falling to 80% at 4K....

BlakGolf · October 25th, 2006, 09:52

i have a bit of trouble accepting 80% for some reason. if it is ill be happy but these heads are horrible. i wanna know VE for 2000rpm, 5000, 55000

im getting good progress done all the math is done

now i have 7 maps to pick a turbo LOL

BlakGolf · October 25th, 2006, 09:55

i used .75 at 5000 rpm in the formula

chippedire.com · October 25th, 2006, 09:55

It can be tricky to work out , you have to do flow testing to find out the restrictions eg valve size , valve timing , intake tract size ect , the list goes on and on .

Since our cars are cars are forced induction we can over come a lot of restrictions .

With out the turbo , 75% max at 2k , i recon with 2 bar boost it could be around 85% anyway at 4500

BlakGolf · October 25th, 2006, 10:03

from the compressor maps that i have from the garrett site half the gt20s shouldnt even be running at 25psi thats what im looking for. i wonder what the compressor maps for the vnt17 and vnt20 are. i have a fealing u guys are running wayyyyy out of the maps. from the maps the best choice should be the gt2259 ( its to bad they only provice the map for the .41 AR tho)

GoFaster · October 25th, 2006, 10:04

For purposes of selecting a turbocharger, just use 75%. It will be close enough. You do not need to split hairs with the numbers in order to do that.

BlakGolf · October 25th, 2006, 10:13

cant figure out what would spool up faster the gt20 with a smaller wheel and larger ar or the gt22 with bigger wheel but way smaller ar (gt 20 ar is around 50-56, gt 22 ar is .41. i should ask my friend he knows a bit more then i do

Gil · October 26th, 2006, 13:14

I always thought that when you have a pressurised intake system that volumetric efficiency was close to 100%. Valve overlap will help rid the chamber of burned gas. Gil

diesel des · October 26th, 2006, 13:43

What valve overlap. None on a tdi....

TDIMeister · October 26th, 2006, 14:06

The presence or absence of any forced induction has absolutely no bearing whatsoever on the true value of volumetric efficiency of an engine by definition.

Gil · October 26th, 2006, 18:02

It is my understanding that an increase in intake pressure will increase VE.
Many engines use valve overlap to increase VE. (not ours)
The trick to getting power out of any engine is to make sure the cylinder is fully charged at high RPM where VE decreases.
Events happen so fast in an engine that the gasses don't have enough time to fully charge the cylinder without help at high RPM.
If you are talking about the engine on a test stand and powered by an electric motor the VE of the base engine can be measured. The higher the RPM the amount of air will drop off a lot.
I think the biggest problem for power is in the injectors not being able to operate in the high RPM area. Spark ignition in a gas engine used to be a big limiting factor. Valve float is another problem as the cams won't be able to open and close properly due to the springs design. (There are always limits)
SuperCHARGING or turboCHARGING are a great way to increse VE IMHO.
...........Gil

BlakGolf · October 26th, 2006, 18:20

ok boys ill explain why i need the VE u put VE in a formula for a engine to be able to find the proper turbo to mate with that engine. thats all lol. the head sucks automaticly VE on this engine would be wayyyyy lower then say a aeb 1.8t or a b18 from honda. u guys might not realise but our cars probably have the worst head on any car on the planet right now

40X40 · October 26th, 2006, 18:56

Quote:

Originally Posted by BlakGolf

ok boys ill explain why i need the VE u put VE in a formula for a engine to be able to find the proper turbo to mate with that engine. thats all lol. the head sucks automaticly VE on this engine would be wayyyyy lower then say a aeb 1.8t or a b18 from honda. u guys might not realise but our cars probably have the worst head on any car on the planet right now

Apples and Oranges. In this case, Gassers and Diesels. I almost forgot,
Mountains out of Molehills.

You are making this much harder than it needs to be.

Bill