Aerodynamics and what happens when you blow a hose at 150 mph

[haskett]

First practice run at Big Bend Open Road Race today, I blew the coolant bypass hose off of the top tube at 150 mph. With a boxed radiator, open hood vents, and 150 mph, the coolant spray eliminated 100% of the visibility through the windshield. I had to steer by watching the passing stripes out the side windows, which is a bit like steering using your rear view mirror. Luckily I was on a long straightaway or I might not be writing this.

Anyway, the coolant left some interesting marks on the car that were clealry visible at dusk and show the aerodynamics of the car at 150 mph.

Lots of airflow out the hood vents and across the hood..

...which then goes across the windshield corner to corner and then across the front two-thirds of the roof (back one-third was dry)...

...and finally hits the rear spoiler at the top edge without ever touching the back window or the deck lid.

 

[haskett]

Oh.... If you run your car at high rpm for extended periods and have opened up the coolant flow by removing the water-to-oil filter adaptor, replace those spring clamps on the radiator hoses with worm clamps. I had replaced MOST of mine, but not all...

 

[snakezilla]

time to bust out a can of elbow grease

 

[Jimmysidecarr]

Bummer!:nonono:
Glad that you were able to drive through that unfortunate happening!:uh oh:

Are you running the Evans stat in the upper hose or the standard T-stat by-pass arrangement?
When I did my rad and Tstat mods I switched all the clamps at that time over to band clamps and I re-tighten at the start of each season.
I had heard about issues with the OE spring clamps from other open track guys.

 

[haskett]

Bummer!:nonono:
Glad that you were able to drive through that unfortunate happening!:uh oh:

Are you running the Evans stat in the upper hose or the standard T-stat by-pass arrangement?
When I did my rad and Tstat mods I switched all the clamps at that time over to band clamps and I re-tighten at the start of each season.
I had heard about issues with the OE spring clamps from other open track guys.

I have the standard thermostat bypass arrangement. It never occured to me that those spring clamps would actually allow the hose to blow off. There must be some very serious pressure built up at high rpm to do that.

I only replaced most of my spring clamps because they annoy me. But I won't get back out there tomorrow until all of them are gone. I have two more to eliminate in the morning, both on the tstat housing.

The good news is that the cooling system is definitely working better with all of my new mods. I purposefully heat-soaked the car prior to the practice run. With an intake temp of 113 degrees and a charge temp of 141, my coolant was only at 203 when I blew the hose. The real test will be Saturday afternoon in the heat going 59 miles non-stop.

 

[boosted2000si]

Been there, done that.


How about my dumbass took my relay out of my IC box and put my jumper in that was wired into the cab of the car. I was out racing and forgot to hit the switch and the coolant started boiling and forcing its self out of my IC tank(At the cap or around the cap rather) out the vent down the hood just like you have there. Thankfully all I had to do was cool the car down, add some more coolant, and put the relay back in.

 

[P49Y-CY]

I have the standard thermostat bypass arrangement. It never occured to me that those spring clamps would actually allow the hose to blow off. There must be some very serious pressure built up at high rpm to do that.

were you running a t-stat? with a functioning t-stat in place, there wouldn't be any pressure or flow through that bypass hose :shrug: (i don't think)

glad to hear you came through unscathed! :beer:

 

[CobraBob]

Wow, you were definitely very fortunate because that could have been one nasty experience. Losing all visibility through the windshield at 150mph isn't for the faint of heart for sure.

 

[DevilSun]

Guess I know what I'm doing this weekend, since I haven't put anything back in my engine or cooling system...all those pressure clamps are getting removed and replaced. Good ending to a very unsafe situation, glad to hear it came out that way.

 

[Jimmysidecarr]

Even without the Evans Cooling higher output water pumps added to our cars the coolant output pressure at high RPM with the stock DOHC Cobra water pumps is very significant!

Even with a fully open T-stat there is still significant resistance to coolant flow from the radiator, the stat housing and stat, the water to oil ->oil cooler and the housing and block interface.

The backed up resistance to flow results in pressure and it will release where ever the weakest point is. That would be near the coolant exit point of the engine if there was still a spring loaded clamp still there.
If you think about it, that by-pass hose is the first hose that high pressure exiting coolant sees, and the by-pass block off in the stat is spring loaded, so it is not a locked hydraulic column of coolant. It would be nice if it was, when the stat is hot and open, but it's not.

Spring type band clamps actually are a pretty cool invention because as OE coolant hoses deteriorate and shrink with age, the clamps adjust to the diminished thickness and can preventing leaks on high mileage engines.

They are not the hot ticket for race engines though.

 

[P49Y-CY]

Even without the Evans Cooling higher output water pumps added to our cars the coolant output pressure at high RPM with the stock DOHC Cobra water pumps is very significant!

Even with a fully open T-stat there is still significant resistance to coolant flow from the radiator, the stat housing and stat, the water to oil ->oil cooler and the housing and block interface.

The backed up resistance to flow results in pressure and it will release where ever the weakest point is. That would be near the coolant exit point of the engine if there was still a spring loaded clamp still there.
If you think about it, that by-pass hose is the first hose that high pressure exiting coolant sees, and the by-pass block off in the stat is spring loaded, so it is not a locked hydraulic column of coolant. It would be nice if it was, when the stat is hot and open, but it's not.

Spring type band clamps actually are a pretty cool invention because as OE coolant hoses deteriorate and shrink with age, the clamps adjust to the diminished thickness and can preventing leaks on high mileage engines.

They are not the hot ticket for race engines though.

interesting jimmy and thanks for pointing that out

i was under the impression that with it fully open there wouldn't be any diversion through the bypass hose, but as you explained it would make sense that it would happen under high rpm's

i remember when i first got the car i was thinking what a shitty design, since it looked like half the coolant went right back into the engine without any radiator cooling, but then could see that when the stat opens it effectively blocks that bypass hose and forces all of the coolant through the radiator

 

[TRQJUNKIE]

Dude I had the same thing happen to me last year after I just flushed eveything and changed the coolant... It was pretty cool though, I killed it immediately and coasted into a 7-11. I was able to fill it and burp it in like ten min. You only blow the hose once because after that you put the worm clamps on fo sho!

 

[haskett]

Been there, done that.


How about my dumbass took my relay out of my IC box and put my jumper in that was wired into the cab of the car. I was out racing and forgot to hit the switch and the coolant started boiling and forcing its self out of my IC tank(At the cap or around the cap rather) out the vent down the hood just like you have there. Thankfully all I had to do was cool the car down, add some more coolant, and put the relay back in.

I'm glad I'm not the first.

 

[Silver2003Cobra]

I wonder how much downforce that rear spoiler provides? looks like a little bit..

 

[haskett]

Dude I had the same thing happen to me last year after I just flushed eveything and changed the coolant... It was pretty cool though, I killed it immediately and coasted into a 7-11. I was able to fill it and burp it in like ten min. You only blow the hose once because after that you put the worm clamps on fo sho!

Absolutely! I had no idea that this was a potential problem. But the first thing I did this morning was replace the two remaining spring clamps with worm clamps. Four passes on the practice course went perfect.

Btw, interesting factoid.... After my last run, we measured tire temps. The front passenger tire was 10 degrees warmer than my other tires because of the oil cooler in front of it. Not hot enough to be of concern, just interesting.

 

[haskett]

I wonder how much downforce that rear spoiler provides? looks like a little bit..

Given that so little of it was getting sprayed, I'm guessing "little bit" is correct.

 

[Jimmysidecarr]

Given that so little of it was getting sprayed, I'm guessing "little bit" is correct.

LOL!

Be careful out there Brian.

Make sure you come back with vids in hand so we can all live vicariously through your adventure!

 

[keith89]

Absolutely! I had no idea that this was a potential problem. But the first thing I did this morning was replace the two remaining spring clamps with worm clamps. Four passes on the practice course went perfect.

Btw, interesting factoid.... After my last run, we measured tire temps. The front passenger tire was 10 degrees warmer than my other tires because of the oil cooler in front of it. Not hot enough to be of concern, just interesting.

Any pictures of your oil cooler setup? I've never seen one in front of the passenger side tire so I'm curious.

 

[forcefedcobra]

I had the pleasure of finding out about the oe upper radiator hose clamp while at Hallett. Came out of "the bitch" and pulled to the top of 3rd gear and POP right when I was starting to slow for the final corners. The cobra that came along behind me was unlucky enough to slide in my trail of coolant and go off track.

 

[haskett]

Any pictures of your oil cooler setup? I've never seen one in front of the passenger side tire so I'm curious.

I started a new thread here for this...
http://www.svtperformance.com/forums/engine-tuning-214/769071-oil-cooler-version-2-0-a.html