The $3500 challenge

TurboTed said>

And I was pointing out that a low-buck turbo set up would rock a whole hoard of more expensive machinery for less than what a lot of folks are blowing on show-car paint jobs, aftermarket stroker motors, giant car audio systems,  or useless bling.

Not only that but it would ROCK A WHOLE HOARD MORE CUSTOMERS!!!!!! HELLOOOOO, WAKE UP CAR CRAFT!!!!! TURBO THAT OLDS!!!!!

True CSIROC but many rodders turn to CC as a leader. Can you say back yard tail pipe turbo set up? I just put a new exhaust on my 93 Buick Century wagon 3300 V6 but didnt put the muffler on yet. If I get all the parts on it, tailpipe turbo and remaining tubing will you help me with the engine management if it needs it? Ill do it, CC can show it in the rag even if it is a FWD.

Can you say home made back yard tailpipe turbo system? Do it CC!!!  

An interesting comparison would be between the 750+ h.p. raised-port Bulldog head/mechanical roller/forged Toronado crank/EFI 455 stroker BBO in the current Hot Rod Engines "special" magazine (available at your local newsstand)  and a more budget-oriented turbo 455. 

The high-horse, all-motor BBO seems to live well with a main girdle.   The turbo 455 should make more area "under the curve" with a more streetable cam, less RPM-related stresses, and a cheaper price tag.   

The bottom end would still have to be built the way D*ck Miller built his, so the price wouldn't be much different. Turbos are not cheap after the custom headers and exhaust, intercooler, modifying the fuel system and carb, not to mention the extra weight and packaging of the system in the car. If I was to go turbo I would want EFI anyway.  

You'd need the girdle, good rods and forged pistons. But you wouldn't need the expense of stroker crank machining (and you'd be able to slide by with a cast crank if the boost wasn't turned up too high--Turbos are much easier on cranks than big R.P.M. or supercharging).  You could also use much cheaper heads (Edelbrocks) that wouldn't require the expensive offset rockers.  And the cam could be a milder hydraulic (perhaps even with a set of variable-duration Rhodes lifters to broaden the powerband).

As to custom turbo headers--they'd be nice, but they're not worth that much over ported logs.  The important part of the exhaust is the part AFTER the turbines--and any 700+ h.p. mill would need a big set of pipes, so that's a wash. 

I'm not aware if anyone has off-the-shelf shorties for the BBO (didn't have time to check Sanderson, etc.), but plenty of JY-style SBFs have used them successfully with turbocharging. Some high-temp ceramic coating would go a long way to making them last for a while.  BTW, Gale Banks still uses cast-iron log manifold (although custom castings) for his 700-1000 h.p. twin turbo SBCs, so the "need" for custom headers is vastly overstated.  And there's always dirt-cheap "weld els" for those who can't imagine a high-performance engine exhaling through factory logs but who can't fabricate a set of stainless steel tubes!

Another alternative (if you just have to have tube headers) would be to use an STS universal remote-mount turbo set-up. I haven't seen anyone do any controlled back-to-back testing between remote turbos and engine-mounted ones, but given the modest horsepower levels we're discussing and the inherent torque of a 7.5 liter engine, the remotes would likely work just fine.

True, intercoolers and turbos aren't cheap. But smart shoppers could land enough parts for a serious budget BBO for around what an off-the-shelf Roots or centrifugal supercharger kit would sell for.

EFI would be better, but plenty of folks are making do with blow-through carbs.  Still, perhaps it'd be fun to cook up a Megasquirt EFI for a "budget" BBO project . . . .

The critical advantages would be that the turbo BBO --

• would be as mild as a baby kitten off-boost,


• would live well with a tight converter, air conditioning and "street" type gears,


• would get somewhat liveable off-boost fuel economy (10-14 m.p.g. in a typical 3,500 lb car--and more if you get crazy with overdrive/weight reduction/aerodynamics), 


• would make huge torque and power from 2500-5500 rpm (where "real world" street/strip cars really live), and


• would be relatively maintenance free (street hydraulic cam, remember).  

NONE OF THESE THINGS WOULD BE TRUE ABOUT A 750-H.P. ALL-MOTOR BBO! 

TurboTed

   Thats what I am talking about, figure out the a/r ratio and that other stuff for a 455 olds, resize one or two of them for tailpipe action and blow thru a single 4 barrel carb. STS claims that an intercooler is not required since the tubes running from the back to front of car have enough surface area to cool of the charge. Besides that the turbo/s are not running as hot being mounted at the tailpipe. My only guess is that you would have to have smaller turbine/impeller to for a reduced exhaust gas velocity way back at the tailpipe but I am not 100% sure of that. Kind of makes sense to me though.

   I have a mildly built 455 right now that was taken out of a car, Edelbrock heads on that would be awesome with the tailpipe turbo set up.

You're on the right track about how the STS remote method works. 

STS's "secret" on sizing is that they reduce the A/R to make up for reduced pressure, temp and velocity at the turbine.  EGTs and initial (off boost) mass flow on low-rpm turbodiesels are significantly lower than on high-rpm Otto-cycle engines, yet turbodiesels commonly run at two or three times the manifold pressue of pump gas street turbo systems. Viewed in that light, STS's turbo sizing theory seems theoretically sound.

I'd be curious to test STS's no intercooler claims on anything more than low boost (5-8 psi) system.  Some of the higher-boost STS systems run intercoolers and alcohol injection.  And without any cooling fins  or turbolators in the intake pipe,  at the velocities necessary to flow 600-1000+ cfm, I doubt there's sufficient surface area interaction to cool a high temp intake charge very much.  But without controlled, instrumented testing, we're all guessing.

Your right TT and what better place to find the right turbo than off some turbo diesels form the junk yards. I am sure that could be a great starting point, looking for an equivalent cid diesel engine, swipe the turbo and parts and mount it on the tailpipe of a similar cid gas engine. I cant wait till this spring, I am going hunting for some turbochargers.