bench testing turbos

[oblique]

Here's the methodology I used:

1. Place turbo on bench
2. Ensure any wastegate ports are closed.
3. Fill oil supply with WD40
4. Hold 2.25 shopvac hose securely to downpipe flange for no more than 10seconds
5. Measure turbo compressor output with hand
6. Enjoy (with glee) the sound it makes
7. Repeat steps 1-6 with different turbos

Lets see how much air the vacuum moves compared to the motor:
1.6ME/MF at 1000rpm we are moving 800,000cc...1600/2*1000
Vacuum is rated at 75CFM which is 2,123,763cc but thats with no load so let's assume 20% loss to move the turbo so we get 1,700,000cc. This means my vacuum (assuming perfect seal) spins the turbo at the same rate as the motor would at 2,125rpm...so roughly an ideal highway cruise on country highways in 5th.

I tried this with my K14, T2, K24 and T3.

The spool time of the K14 and T2 were noticeably faster...maybe half. vs the bigger turbos. In terms of volume of air pushed, again Im just using my hand, both the K14 and T2 seemed to move air. I think the K24/T3 just incur more loss because the turbines are just so much heavier...they are likely capable of a higher top threshold of output but the engine just isnt big enough to move enough air to fully utilize them.

On a 1.9 AAZ for example we are moving 16% more air but the K24/T3 turbo housings are much larger than that compared to the smaller turbos...Id say as much as 40 or 50%. So to really use the big turbos you would need something in the order of a 2.5L engine.

Conversely, are the VNT15s too small for the ALH? Is that why folks get more power? Or to the dynamic vanes complicate things.

[libbydiesel]

I haven't hooked up my shop vac to a turbo, but in actually fitting the various turbos to the same engine, I agree with your conclusion that the K14/T2 move similar amounts of air to the K24/T3 at normal boost levels.  There is no real benefit to the K24/T3 unless you are running very high boost at high rpms. 

The VNT15 is not 'too small' for the ALH although the VNT17 is more relaxed with a very slight increase of lag.  The variable geometry makes either one able to be 'smaller' than a K14/T2 and also larger than the K24/T3 depending on vane position. 

[fatmobile]

I think the VNT-15 is a great size for my 1.6Tds.
 It's supposed to run at 15psi consistently, while keeping the EGTs at 1200F.
 That's what my goal is anyway.

 I don't think the 1.6TD can handle much more than the VNT-15 gives, without breaking.
 It boosts up fast, provides great power when I go to take off.
 It can give me a nice second gear burnout if I want one, even with posi.
It needs a beefier clutch, minumum 210mm gasser clutch.
 It has just enough at the top to keep the EGTs down to 1200F.

Easy to build a downpipe for.
 Allows different (cheap and readily available) intakes because it hangs so low.
It's a very reliable turbo, cheap to buy used (under $250, often $150) and replace.
 "Easy/cheap" to rebuild.