VT-50 Jr. Dragster (kindof)

[Feathers]

IT RUNS!!!!!!!!!!
HAPPY DANCE!!!!!!!!!!

I haven't updated my blog yet, and I know "it didn't happen unless theres video" . My friend took one with his phone (which shoots like 720p... technology these days...).

First attempt was a hot start, because I was trying to throttle the leafblower, disconect a hot ignition exciter, and crank up the propane at the same time.

Freaked me out, but the turbine checked out once I cooled it down, and I was ready to try again.

Got my friend up front running the leafblower so I could run the propane from behind the engine, keeping an eye on the color of the turbine as it spooled up. I slowly brought it up to what sounded like a pretty good idle (I don't have a tachometer yet).

The engine runs like a charm on methamphetamines.

I had it idle on propane for >25 minutes, oil pressure remained at ~40 PSI, and the oil lines remained cool to the touch with the radiator fan running. Looking as far into the turbine volute as I could see it was cool black all the way in. Compared to my last engine (which idled at about 70% full throttle because of a terrible design) and despite the size of the turbocharger, idle is remarkably quiet, which means I did something right.

Once I was confident that the engine was sound and the evap system was hot, I began to throttle the engine with diesel. I don't have a tachometer or P2 guage yet, so "throttling" was pretty conservative. The engine was very responsive, and even when I opened the fuel valve quickly, I only noticed a small lick of flame inside the turbine housing, and cool turbine blades all the way.

Then, it happened .

I heard an eanormous POP and the turbine began to spool down. I was freaking out, as I was perhaps being a little reckless starting the engine with no instrumentation but an oil pressure guage, and didn't know if I might have "popped" a turbine wheel .

It was nothing but a big hole busting through the 3" rubber elbow connecting the compressor to the combustor inlet tube. I'll upload a picture if I can, because it is a PERFECT cartoonish rupture, and had my friend and I gasping for breath laughing when I removed it and we got a good look.

I'd known when I ordered it that the rubber elbow might not deal with pressure or heat that well, and it was burning in the back of my head, but It was cheaper than the silicone reinforced pieces.

Live and learn

Very happy with the engine's performance so far, an look forward to more testing once I get a replacement elbow in!!!

Feathers

[Johansson]

Congrats!!

[racket]

Hi Feathers

Yes, congratulations :-) ..........................heh heh , those sudden engine stops are generally accompanied by certain unwelcomed bodily functions , I hope they weren't too severe ;-)

Cheers
John

[ernie wrenn]

Way to go!!! I have had a few of those "sudden stops". The heart stops right after the "OH SH#T.

Ernie

[Feathers]

Haha I havn't wet my pants yet, we'll see if anything else gives way during a test...

By the way...

Tachometer setups are quite expensive, and I probably won't get to it for awhile.

Is taking a measurment of P2 an acurate (eanough) way to guestimate engine speed?

I know that the relationship between max rpm and max boost will change with the turbocharger and the setup, but say I were to run up to 15 PSI or so for now, would that be a "safe" pressure? This turbocharger is probably designed to produce up to 25, 30 or possibly more, so I wouldn't be pushing max turbine speed at 10 or 15 psi.

Thanks!

Feathers

[wolfdragon]

...

easy and cheap way

you need an infrared LED and an infrared receiver (looks like a led)

bounce the IR off the nut, watch it with the receiver, matte black all but one flat

the signal will be a square wave at one pulse per rev, plug that into your multimeter that has a freq measurement, it will read in rev/sec so just divide by 60 for rev/min

circuit will look a lot like this:
elecrom.files.wordpress.com/2008/02/sensor-schm.jpg

The capacitor is just a noise filter and the potentiometer is for setting the receiver gain, too much and it will just be a constant voltage, too little and there will be no pulses

[Feathers]

I don't have a multimeter with frequency measurment and my osciloscope is 30 years and in serious need of calibration.

I have a boost guage (a pretty cool backlit one) and I think I'll use that untill I can get a more permanent setup.

In the meantime, a nice all-functional multimeter would be great... and I do have a job...

[wolfdragon]

There is a pocket multimeter at mcmaster Carr for under 35usd

www.mcmaster.com/#7613K81

you now have no excuse

[Feathers]

true... but heres a laser tach for about $12
cgi.ebay.com/ebaymotors/Digital-Laser-Photo-Tachometer-Non-Contact-RPM-9852-/180583063718?pt=Motors_Car_Truck_Parts_Accessories&hash=item2a0b96e0a6
I didn't have an excuse to start with!

[Johansson]

Assuming that a gas turbine´d turbo can take the same pressure as it would produce in a car/truck/whatever is a mistake I have made.

My old Holset truck turbo on the gocart was probably good for 2-3 bar in the truck but when I by chance measured the revs during the first "safe" runs at slightly above 1 bar I found that I was already at max revs!

It all depends on the comp intake vs. turbine outlet diameters, my Holset was a "Free Floating" design where no wastegate was used on the truck since the turbine section was deliberately oversized so it wouldn´t be possible for the truck engine to over-rev it.

A better sized turbo with similar inlet/outlet diameters produce much higher P2´s at the same revs, so it is difficult to say what P2 that is the limit for your turbo. I bet you a bottle of brandy though that John´ll tell you a safe max P2 if you give him the diameters.

[racket]

Hi Anders

Yeh , those over sized turb stages can play havoc with P2 vs rpm ratios , only gotta look at any comp map to see how the rpm lines droop severely on the right hand side of the map .

Feather , a P2 of 15 psi - 2:1 PR is probably safe for your sized turbo without a tach .

LOL, I never had a tach on my bikes TV84 and it was taken to 45 psi P2 - 4:1 PR ................I shudder to think what sort of rpm it was doing when running those pressures .

Generally as long as you keep your T2 temps( comp discharge) under say 100 deg C - 220 F at 15 psi P2 - 2:1 PR on a 15 deg C day , and for a P2 of 22 psi - 2.5 PR a T2 of ~135 deg C -275 deg F you'll be running in the high efficiency regions with reasonable pressure vs rpm .

Cheers
John

Cheers
John

[wolfdragon]

is that 15 psi for 2:1 PR a gauge pressure?

also, what is the make/model of that gear pump and where did you find it?

[racket]

Yep 15psig , 29.7 psia divided by ambiant 14.7psia gives a ~2: 1 PR , actually 2.02: 1 PR , but considering most gauges we use are only within plus or minus a couple percent , 2: 1 will do ;-)

Cheers
John

[stoffe64]

Congratulations to you for your running engine,were you running the engine om propane only or was it in diesel as well?
Congrats once again Austin!!

[Feathers]

Thanks guys!!! I'll have that boost pressure guage hooked right up. And I really appreciate the advice John, don't think I'll be trying to pull 45 PSI yet but 15 sounds like a fun, safe max .

I'm displaying the now running engine (after getting a new reinforced silicone 90* elbow that won't grenade on me) at the Kansas City Maker Faire, www.makerfairekc.com/, along with my 750 watt tesla coil, www.youtube.com/watch?v=dg-WZiRI1-M&feature=channel_video_title, and some other electrical goodies I've experimented with for awhile. Its going great, I've already landed an opportunity to be featured in an engineering magazine with the engine, and made countless priceless connections.

The engine is running on propane for now, as its easier to set up in an eager crowd, and not very messy (or smelly).

The question is: does propane burn hotter than diesel? I'm thinking it does, but I'm not sure.

John, your advice might be haunting me . With the propane running through the pilot nozzle, the edges of the turbine wheel begin to glow a very dull red when I really crank it up (this was noticed at dusk). The pilot injector does not have the extra burn time that the diesel will in the evap system, and because the relatively significant (pi*.5^2)in.^2 cross-sectional flow area of the evap tree has been subtracted from the total primary mixing hole area, the propane is recieving alot more air in the primary zone from the evap tree than the diesel will (that will be begining to combust inside the evap tree).

This dull red glow isn't significant (it still idles perfectly cool and black inside the turbine scroll), and I'm not worried about the engine's basic functionality, but as I begin to explore the engines true capabilities with more comprehensive instrumentation, these issues might begin to bother me. Just looking at the variables and trying to guess at how diesel running through the fuel system the way it was meant to will affect the performance and EGT.

Thanks all!!!

Feathers