KEEP COMPRESSOR OPERATIONS OUT OF THE "CHOKE ZONE"

By 460-BBF-Turbo-In-CC (adapted from the legendary Car Craft Forum turbo blog)

"Don't choke now!" -- Grady Seasons (Keith McCready), "The Color of Money" (1986)

The following excerpt appeared on the forum at Bangshift.com:

"[The January 2011 issue of Auto Enthusiast magazing at pg. 30]has a story about a class project at WyoTech's Blairsville, PA campus. They built a crate 350 SBC with a single [Holset]HX35. It maxed out at a paltry 575 h.p. on 15 psi manifold pressure (charge cooled). This shows that the engine was obviously running well into the choke zone of the HX35. [Jay K.] Miller's map [Turbo: Real World High-Performance Turbocharger Systems ]shows that the HX35 goes into choke at ~ 50 lbs/min at 2.0:1 pressure ratio."

 

Sadly, Holset is tight-fisted with its compressor maps and there isn't a good on-line map of the HX35 available today.

 

Referring back to the old T66 map, every point to the right of the mapped area is in the choke zone of the compressor. Choke means just as it sounds -- the turbo compressor is choking the engine because it is not large enough to flow air efficiently in the quantities the engine COULD be consuming.

A turbo operating in the choke zone is too small for the engine at high r.p.m. It's that simple.

That doesn't necessarily mean that the turbo is too small at every r.p.m. For example, the WyoTech Blairville SBC reportedly has excellent low r.p.m. response, with a boost threshold (on-set of measureable manifold pressure increase) of ~ 2,000 r.p.m.

In another famous example (reported in the June 2001 issue of Hot Rod Magazine), Chris Stewart used a pair of junkyard 1986 Ford Thunderbird Turbo Coupe Garrett T03E turbos on a 472 CID BBF. The boost threshold was a mere 1,700 r.p.m. and it pounded out 714 lbs./ft of torque at the rear wheels through a power-guzzling non-lockup C6 automatic. And Stewart achieved this on a mere 10 psi of "boost."

The torque peak was a diesel-like 2,200 r.p.m.

However, the smallish turbos greatly restricted power at high r.p.m., limiting the 8.2:1 BBF to a weak 355 RWHP at a tractor-like 4,200 r.p.m.

Even though a turbo will still flow some air in the choke zone, the mass air density will be lowered by excessive charge heating. The turbo could also be at risk of overspeeding. And if the turbine (exhaust side) is fairly well matched with the compressor (as expected with factory turbos but not always true with aftermarket "hybrid" turbos) the turbine is likely also in an inefficent range of operation when the compressor is in the choke zone. Excessive backpressure and exhaust heat from a turbine opertaing in choke can hurt power production and exhaust valve longevity. In short, operating in the choke zone is akin to a dog chasing its own tail.

 

It should be clear by now, a properly fitted turbo or turbos must avoid the extremes of surge and choke. The "sweet spot" for turbo compressor operation is in the middle portions of the map where compressor efficiency is the highest.

What does "choke" mean? And why does it matter?

SMOKEY YUNICK’S HOT-VAPOR "TEASE" IS BACK

By Cammie

Smokey Yunick’s legendary (or some say mythical) Hot Vapor Cycle engine has long been of interest to Truthseekers at this blog.

Now the September 2010 issue of Hot Rod Magazine reinvigorates the legend with the so-called "Story Behind Smokey’s Hot-Air Engine.

According to HRM, the keepers of the Hot Vapor flame are engineer Ralph Johnson and ISCA show car builder Tony Allers.

Johnson claims to have built the first Hot Vapor engine at GM back in the days of the Blue Flame Corvette. Allers picked up Smokey’s Fiero prototype engine at Yunick’s estate sale and recreated Smokey’s infamous Fiero. HRM reports the recreated Fiero is now in Don Garlits’ drag racing museum in Ocala, Florida.

Of course HRM’s story is another big tease. Allers and Johnson don’t really explain how to build a Yunickmobile at home. And the story suggests that Yunick took some of the "secrets" to the grave. HRM does suggest that big corporate money has picked up the research (perhaps under the guise of the trendy Homogeneous Charge Compression Ignition (HCCI) theory.

But for grassroots hot rodders, "hot vapor" remains just so much "hot air." That's sad. Imagine where the technology would be today if secrecy and greed weren't factors.

Here’s a potpourri of links to discussions about Yunick’s engine:

Skeptical engineers speculate on how it works (or doesn’t) here and here.
Background research on Smokey and the Hot Vapor Engine.
The story behind Tony Allers’ Fiero is here and here.
A test drive of Tony Allers’ Fiero.
Hot Vapor Engine presented to the Smithsonian.

TWENTY YEARS OF MANDATORY AIR BAGS . . . AND A FEW C4C “AIRBAGS” FROM CALIFORNIA

[Get the latest “Truth With Speedzzter” here]

On September 1, 1989, driver side air bags became mandatory in all new cars built for sale in the United States.

While the safety record for air bags is mixed (and thankfully Speedzzter has never deployed an air bag), most certainly some owe their lives to them.

Our larger problem, however, is a different kind of “air bag.”

The sort of air bag that deploys every time we exercise our automotive liberties in ways they don’t approve of. These “air bags” are “green” and are working to outlaw or regulate out of existence virtually all of the automotive hobbies and most grassroots motorsports.

The Greeniac "air bags" view almost all hot rodding as "tampering." They see all antique vehicles as "gross polluters." And they provide no alternatives or incentives to help vintage automobile enthusiasts enjoy their passion while minimizing and mitigating the environmental effects.

These Green "air bags" see car-crushing “buy backs” such as the CARS Act as a potentially potent tool in their attack on automotive liberty. Although the CARS Act has now thankfully wheezed off into history, the propaganda war for the next round of vehicle scrappage has already begun.

They are the new "mandatory air bags." Hopefully they won't stay in power for the next twenty years . . . .

Chad Lohnes over at Bangshift.com and Daniel Strohl over at Hemmings Motor News spotted a recent Los Angeles Times story by a couple of apparent "green air bags" (Ralph Vartabedian and Ken Bensinger) which trashed the Specialty Equipment Market Association’s effort to limit the horrific damage done by “Cash for Clunkers” to vehicles built after 1984.

The story, entitled “Why 'clunkers' program won't take some of the most polluting cars” amounted to a thinly-veiled call to expand the “War against V8s” and vintage vehicles to vandalize and destroy the 3-5% of the vehicle fleet that was built before 1984.

See, Truth With Speedzzter told you so!

Here's part of what I sent to one of the alleged journos via e-mail and posted over at Bangshift: (feel free to copy, modify and e-mail to them if you like)

I found your article to be highly one-sided and biased toward the state-sponsored vandalism of low-priced vintage vehicles. The free market, not some taxpayer-funded welfare program ought to decide which vehicles survive and which do not. Short-sighted schemes such as “Cash for Clunkers” corrode the free market. They also breed welfare sucklings who depend of borrowed-tax-money funded handouts. This dampens personal industry and self-reliance.

Of course the real intent of these programs is to drive people out of the automotive hobbies. As General Phillip Sheridan proposed in 1866, “Kill the buffalo and you will kill the Indians.” [see the “Buffalo” post link in the “Best of Speedzzter” sidebar]

It’s the same with vintage automobile interests. Basic economics teaches that as costs and barriers to participation rise, fewer chose to participate. If the power-mad environmental lobby can deplete the supply of affordable “vintage” donor and potential collector cars, the price of used replacement parts will necessarily skyrocket. In some situation, this could cause severe damage to the aftermarket. These state-sponsored vandalism plans also hurt vehicle resale markets and many small businesses who depend on servicing vintage vehicle market niches.

Nor do public relations “puff pieces” supporting vehicle scrappage like yours take into account the entire “life-cycle” cost to the environment of a vintage vehicle. Virtually all of the energy and pollution costs of producing a vintage vehicle have already been “amortized” to the environment. And such vehicles have a limited impact on air pollution, notwithstanding the handwringing claims of “experts’ at [the California Air Resources Board (CARB)]. The comparison of the Malibus [A CARB hack compared a pre-emission controls Chevelle with a current Malibu in the story] is most unfair, given both the rarity of such models for regular transportation use and the infinitesimally tiny amount of “pollution” of most current new vehicles. Most chain saws, motorcycles and lawn mowers probably emit several times the “pollution” as the imaginary new Malibu -- and are much more common than a vintage 1960s collector car -- but they are not singled out for venom and slack-jawed demonization. Based on their cumulative effect (e.g. vehicle miles driven), many, if not most, of the vehicles destroyed in Cash for Clunkers plans are NOT “some of the most polluting cars.”

These wasteful plans are indiscriminate. They sweep up fairly common-place utility models as well as rare milestone vehicles which have the misfortune to be at the low ebb of the depreciation cycle and in the custody of greedy, welfare-loving “appliance motorists.” However, to true students of automotive history and design, any pointless destruction of potential collector or donor vehicles is an irreplaceable loss to future generations of motoring enthusiasts.

Much like a ban on “Saturday Night Specials,” Cash for Clunkers disproportionately attacks the lower economic classes. It is therefore elitist in effect.

Cash for Clunkers programs also disproportionately affect affordable V8 powered vehicles. Some have described them a as a “war on V8s.” Given the coming hikes in Corporate Average Fuel Economy (motivated in part to placate a minority of California enviro-socialists), fewer RWD V8s will be produced and the few that survive will become significantly less affordable. Thus, one of the apparent aims of Cash for Clunkers plans is to limit the availability of traditional V8 performance vehicles.

Undoubtedly the most radical of the greens (and some allegedly “objective” journalists) will not be satisfied until vehicular liberty is decimated. A world of slaves to public transportation and/or electric micro-golf cars is their nirvana. I suspect that is your goal as well.

Your story did a real disservice to all readers who hold a more balanced, historically-sensitive perspective in the war against automotive liberty.

The discussion at Bangshift eventually turned to Hot Rod Magazine’s legendary “Crusher Camaro.” That was a project car from a couple of decades ago which was snatched out of line from a stupid UNOCAL “clunker” purchase program (If memory serves, UNOCAL was trying to offset the pollution of a California refining operation . . . which foreshadows what will happen on a larger scale if “Cap and Trade” ever become law).

Hot Rod Magazine honcho David Freiburger has written that the Crusher Camaro will likely return for an encore.
There’s a larger opportunity here.

The Crusher Camaro originally emphasized the point that properly-tuned vintage hot rods don’t really pollute all that much (especially when their limited use is factored in)

But Hot Rod could do more this go-around. The point that needs to be made now is this: if the environmentalists and CARB bureaucrats really weren't anti-hot rod and generally anti-car, they would make compliance easier and cheaper.

Maybe when Mr. Freiburger brings back the Crusher Camaro, he'll do some sort of home-brewed "green machine" version of it to tweak our know-it-all car-hating critics and point out the ridiculousness of the current regulatory scheme.

A reborn "Crusher" powered by a hybrid Tahoe powertrain** (turbocharged and converted to E-85***) would open a few eyes . . . . It would also be interesting to see how much CARB would hassle such a set-up. (CARB seemingly hates aftermarket turbocharging and CARB’s engine swap rules are byzantine to say the least.)

_______________________________

**Truth With Speedzzter realizes that this driveline is virtually unobtainable for 99.9% of rodders and that hybrids are dependent rare earth metals that are becoming in short supply And Truth With Speedzzter is also aware of the complexity of such a swap.

*** Truth With Speedzzter is aware that E-85 is often criticized as on environmental grounds, And it's not really available in Cali . . . But you can run so much more freakin' manifold pressure (turbo boost) with it!