Why not have a wastegate on a blower set up? You can achieve boost sooner and blow off the extra boost (pulley up). The Wastegate can dump into the fittings for the Air Injection pump directly into the exhaust so you don't have that loud exhaust leak sound under the hood.

There must be a simple answer why this hasn't been done...

Then you can use a boost controller like a turbo right?

Yes yes yes, I know that the wastegate is only for exhaust but it effective controls boost pressure (regardless of source - exhaust or intake). It just recognizes pressure. It would be similar to a Blow Off Valve but with the programming of a Boost controller.

I like how the turbo comes on the boost quick and I don't like how the blower "ramps" up to full boost. Why not get full boost like a turbo by getting a higher boost pulley and regulate maximum boost with a boost controller and retrofitted wastegate. Will a blow off valve have that flexibility?

 

I've wondered why this cannot be done. One of the theories is that when you overdrive a blower that much, then you might run over its efficiency range and create excess heat. Other people think that it will cause excess heat because of the air flowing out through the 'gate. Others just can't understand why you would put a wastegate on the intake side "ain't thems for a turbo?" Until someone actually tries it, the world may never know. I know of a company testing a setup using a clutch system on a centrifugal to achieve similar results. They can just about tune the torque curve of an engine into whatever shape they desire. Cool stuff.

 

It takes so much energy to compress air, why would you waste it by blowing it off to atmosphere. This isn't a very efficient way to regulate boost.

FWIW a small air leak on the dyno on my car cost me 100 Hp (hose clamp was coming loose) I retightened the hose and got it back. The boost stayed the same in the intake manifold with the leak, but I bet the turbo was working OVERTIME to keep the same air flow putting it way out of it's efficiency range, which is exactly what you would be doing with a wastegate on a blower.

Bill

 

...it costs hp to turn the blower off of the crank.

Ryan

 

You're saying that you would spin the blower much faster than normal and bleed off anything over, say, 6 psi.

1. You would run the blower beyond it's efficiency range. As you spin your typical Vortech blower beyond 30,000 impeller rpm, it starts losing efficiency. As it loses efficiency, the boost is heated more, which makes it less dense and leads to detonation.

2. You would overspeed the blower. I'm spinning my T-trim to 68,000 rpm and making 13 psi max. According to Vortech, the max safe speed for a V-1 T-trim is 65,000 rpm. How fast do you plan on spinning yours?

3. The bled-off boost will do you much more good if you keep it in the intake tract. Why would you want to bleed it off? It's like spraying Nitrous on the outside of your air/air intercooler. It will do you much more good if you put it in the motor!

Mike

 

Thanks for the replies. This is a hypothetical thread... nothing has been done yet.

Mike, suppose someone decides to run a T-Trim with a pully that should provide 12#s. But you want to run 10#s. The 12# pulley will build lower RPM boost more quickly than the 10. But if you want only 10#s max, then bleed off the other 2#s. The bled off 2#s would not hold heat because it is relieving pressure... right?

The goal would be to provide lower RPM boost like a turbo. The efficiency would be not as extreme at 10#s than 12#s. The T-Trim would still be operating within the safe limits.

I can see where the 12# pulley will tax the crank more than the 8# or 10#.

Smoknz, I can see where it would be wasted energy to bleed it off. Makes sense to me. But wouldn't it be a decent trade off to have more boost at a lower RPM and tax the crank a little more with a higher # pulley?

Thanks for answering these questions guys

To summarize, the higher # pulley will add more boost quicker at lower RPMs... then bleed off the extra you don't need.
Cons: 1) Wasted energy to compress a few extra pounds of air, 2) excess heat, 3) wasted potential boost.
Pros: 1) Reach desired boost at a lower RPM... quicker.

 

its a good idea but i dont think producing low rpm torque as the turbo will is going to happen.

with the blower you'll only see maybe 5 out of the 10 psi max down low even with the pulley setup you're talking about. as apposed to the full boost achieved by the turbo down low.


i do understand what your talking about though, been wanting to try something like that for a while!

 

Mike I thought the T-trims max speed was 55 not 65.

If you are pulleing up, why not run the extra 2 psi anyways? the only way to do this would be with an A/C clutch or something similar that you could control electronically.

 

If you pressurize ambient air with a 100% efficient compressor, it heats up.

T1/T2=(P1/P2)^((k-1)/k)

If you release the pressure, it returns to ambient temperature.

However, if you pressurize air with a 70% efficient compressor, it heats up more. If you release pressure, it does not return to ambient temperature because you've added heat on top of normal heat of compression.

So, bleeding off 2 psi will not return the remaining 10 psi to it's non-bled-off 10 psi temperature -- it will be hotter.


Highlander, you're right, max T-trim speed is 55,000 and I'm spinning mine 58,500 rpm for 13 psi.

I agree that you should run the extra 2 psi anyway rather than bleeding it off.

Mike

 

I wish its max speed would be 65k like the YSTrim

Anyways.. the only way is a clutch.

 

Your time would be much better spent designing a variable pulley and use that to control the boost. A dynamic one would be great. It could ramp up the boost quickly and then keep it there throughout the rev range. A modified version of a snowmobile clutch, perhaps.

Even a manually variable one would be great. One where you could take a wrench to the pulley and vary its diameter. That way, in minutes, you could dial in 8lbs for the street or 14lbs for the track when running race gas.

Brent M.

 

Now you're thinking!

A CVT drive would work the best. That consists of two cones facing away from each other with a V-belt riding between them. A governor weight could swing outward at high rpm and a linkage would actuate the cones to move apart, thus reducing the diameter of the drive pulley and slowing the blower at high rpm.

Problems you may encounter:

- Space is limited.

- Drive is only one V-belt, which may not be able to transmit the 50 hp required to drive the blower.

- The tensioner must mainain alot of belt tension over a broad span. A regular Vortech (Ford) tension doesn't have the range needed.

- The governor/actuator assembly must be balanced and light weight.

- The governor/actuator assembly must be strong enough to handle the cetrifugal forces associated with 7,000 rpm. I wonder if SFI would certify it?

- Someone must design and build this stuff. It would involve some pretty intricate fabrication, requiring a skilled machinist.


Maybe a better idea would be to use a high stall torque converter. Using a Vigilante 2800 (which stalls closer to 4000 in my car), I never see less than 10 psi boost, with my peak being 13 psi.

Mike

 

Interesting discussion. Thanks for the calculated answers and details versus the typical "yes/no crap". You guys really gave this some thought.

A CVT isn't a bad idea... hmm.

To get the blower to put out more boost at a lower RPM it would need to spin faster at a lower RPM. A clutch would only lock it up to 1:1... Or, it would slip and let the drive belt spin faster than the pulley. I'd think you'd want the pulley to spin faster than the drive belt to get the boost at lower RPMs.

 

Actually, I just thought of a simpler way.

You could use some sort of torque-limiting slipper clutch on the crank. Use a 7" crank pulley and 2.5" blower pulley (both available from ASP). This would put the impeller rpm at 20,000 at only 2,000 engine rpm. Then, as engine speed increases, the torque required to drive the blower increases also. The clutch would slip and limit the blower speed.

Patent Pending

Mike

 

Good idea! That would have to be a stand-alone belt or it would throw off the other accessories.