Inflatable boattail

[tasdrouille]

Here's an idea for turbocharged engines, you could basically bleed unused boost to the boattail instead of just opening the wastegate.

[donee]

Originally Posted by tasdrouille

Here's an idea for turbocharged engines, you could basically bleed unused boost to the boattail instead of just opening the wastegate.

And, shoot the bleed air out the back of the car either for rocket boost, or for boundary layer control .

[dremd]

Not so sure about bleeding boost off, I believe the boost gives a fuel economy boost, Not at all sure on gassers, but on diesels 4 sure.
However if it was just to inflate, it might not be an issue . .. . . .
I'm banking on a 12 volt inflator from an air mattress, or equivalent.

[donee]

Hi Dremd,

Yes, of course. The pressure that makes it to the engine from the air pump is controlled however. Because at certain running conditions the pressure could be very very high. So high, that if allowed into the engine the fuel octange would not support a controlled burn, but detonation. So on a turbo there is a device called a waste-gate. It shunts some of the pressurized air either out into the atmosphere, or back to the pump input stream. The energy to pump up that waste air is wasted. The idea would be to use it to help push the vehicle, or reduces its air drag.

[buckyball]

Originally Posted by aerohead

Back in the 90s I did a inflatable boattail for the T-100 ,when it was John Gilkison's.We took it on a camping trip near the Very Large Array,in New Mexico,and did a roundabout long way home,just to get more miles.For about 600 miles of driving,the inflated tail gave over 30-mpg.

The mileage figure you achieved with the boattail and half-tonneau was great. I did not see a pre-mod mileage figure though; do you have that data?

[dremd]

I need to add my other vehicles to my ecomodder garage

1 87 Supra T77 Drag only Tial wg (open) sprung at 18, Boost controller set at 22 Liquid 2 air intercooler (8.4/1 compression) soon to be E-85 powered R154
1 89 Supra 60-1 ct26 High compression GTE AE340 (9.5/1 compression) Pump Gas (scca Solo2/ blast on the street with the targa off)

I've wrenched a lot on friends DSM's, WRX (just 1 of them) I've turboed an 07 focus (from scratch), Worked on a 9 second turbo 5 liter (10.5 class), farted around with a turbo caravan, had a tt z32 for a spell, turboed a few civics (bolt on affairs), farted around a little with supercharged fords (not much) done an LS7Rx7, worked a little on ls1 TransAms, and lots of fun with SBC's. (By the way the new BMW TT 3.0 is AWESOME I got to do a little stunt driving in one (and I secretly want one))
On the 89 I once towed a 99 Surburan which was towing a camaro on a trailer for 25 miles (off of the basin bridge) at 55mph I ran a sustained 5~6 psi, I don't want to know what the fuel economy was, made mental note to not check mileage on that trip.
With the boost controller set at 0 the wasegate will open at 6.9 psi.



By far the most efficient boost control setup is VGT. The TDI has one and am totally in awe how much better of a setup it is than a waste gate . . . .

Cliff note, yes I know what a wast gate is, at constant speed they are very rarely open Find me a gas car that has the wastgage open at cruise and I'll do, . . .. well whatever you say.

[tasdrouille]

Originally Posted by dremd

By far the most efficient boost control setup is VGT. The TDI has one and am totally in awe how much better of a setup it is than a waste gate . . . .

Could you please elaborate on that? I have and A3 TDI with a wastegated kkk03 and never heard the comment that a vnt-15 on the A4 TDI was "more efficient".

[dremd]

Geese, I guess I don't know how to explain it; other than to say that the turbine Map is somewhat alterable by the vgt, so as to move peak torque around; closer to your current rpm.
Not much here->
http://www.osti.gov/bridge/servlets/...ive/771164.pdf
http://www.patentstorm.us/patents/65...scription.html

[donee]

Hi dremd,

Sorry if you felt I was being simplistic. But your comments were phrased simplistically. You apparently have more practical knowledge of Turbos than I.

But the method being proposed has been researched by NASA, although not used in production practice. They put little holes on the downstream side of a wing, and injected bleed air from the jet engine through the holes. The goal was prevent flow seperation at low speeds. Inflating an air bag at the back of the car would be alont the same lines. One might actually be able to combine the two, and put small holes in the air bag.

If there is no waste gate operation at highways speeds, there is no bleed air available for this.

If you bleed air off the TDI turbo, will the variable geometry control be altered to bring the pressure back to what it supposed to be ? As you alluded to, there will be effective comprssion ratio lost however. Maybe the VGT control is just shooting for as high an ouput pressure it can achieve, all the time in the TDI ? As the fuel is going to detonate anyway...

[tasdrouille]

If I take my TDI as an example, I agree that at cruising speed on a flat road the turbo does not produce enough boost for the wastegate to open.

In this case a better option might be a 2nd turbo dedicated as a compressed air source.

Donee, the "electrical bleed" that some people do to the VGT 4th gen TDI turbo will only up the boost limit. I'm pretty sure the turbo is shooting for as high as it can for any given operating state below the limit.