Turbo Versus Roots Net Horsepower

[Bob Drury]

Wheeler Dealer, Just remember that if you want to run turbo's in the classic class that you cannot use any type of electronic timing, injection or any other non mechanical device on the motor.         Bob

[maguromic]

You don't electronics to get a turbo to work, just look at the 4 cylinder turbo offy's of the late 60's and 70's.  They were getting close to 1000hp and more without electronics. There is a whole plethora of parts availabel to do it without electronics. Maybe Rex will chime in with his story about the runaway turbo Offy on the dyno.  Tony

[wheelrdealer]

38... I ussually start with FUBAR and replace and rebuild until I get something decent. Sometimes its just an expensive FUBAR in the end.

Bob:
I understand about no electronics. That is clearly stated in the rule book. That also makes the tubro option a challenge. Manually adjusted pop-offs and waste gates present serious challenges over electronically controlling these functions. We plan on spending a lot of time on the dyno working through the tune up.

My other concern is dumping the exhaust out of the fenders verus under and out the back of the car. I know this topic has been covered in other threads but I plan on looking that topic up as well.

38  sorry to hyjack the thread. Good luck with the conversion.

Bill

[38flattie]

Bill, no problem! I usually learn as much, or more, from small sidetracks, as I do from the answers of the original topic.

[salt27]

I know we are talking about power here but don't forget about the aerodynamic difference.

   Don

[jl222]

  My adiabatic efficiency charts for a 70 deg day and 14lbs boost show  45% efficient  315 deg  roots type
                                                                                                 65%              240 deg  
                                                                                                                           turbo or centrifugal
                                                                                                 75%              217 deg

  Cooler air allows for denser air [or more of it] and if it is cooled by an intercooler or water injection the air shrinks even more so you end up with more molecules to compress ignite and expand.

  This is why roots blowers on gas don't go any faster at Bville than the unblown guys. [non vintage anyhow]

   In 1991 or 92 [222 Camaro] we had an exit speed of 275 mph with 12 lbs of boost [Bville news thought I was lying and terminated the interview] We had set the record at 229 + at El Mirage and upped the gearing to 1.85 from 2.39  the rpm was only about 6200. We finally figured out the blowers had to be geared up also.

  In 2010 we had a time of 294 mph in the 1st mile boost temps at 14 lbs was 104 deg and 132 deg at 24 lbs

  We run a 55 gal min water pump for intercooler ice water and we also inject water.
  
   And the main thing; a 139 Procharger centrifugal blower that enable us to make 2300+ rear wheel hp.

   One reason WW11 aircraft engine designers used centrifugals over turbos was of the thrust hp.

   Also centrifugals don't sound like bloodless cyefers


                     JL222

  

  

[saltwheels262]

never been a big fan of turbos.
roots type blowers have the look.

centrifical blowers are the way to go. imo.
and like above-- procharger.

to be efficient, all forced induction, need to have an intercooler.

[maguromic]

Not to high jack the thread, but in the early 50's there were a few cars with turbos.  So why cant they be run in vintage now without electronics?  Inquiring minds want to know.    Tony

[Dynoroom]

Not sure I know much about this but You might want to look a mass air flow in lbs/min. and not boost pressure when it comes to making hp.  

Garrett does have turbine maps that calculate power required to "run" a compressor. you might do a search or two.    

Density is what this might be all about, you know............. how many molecules per sq/in.  

I'll wait and see how this develops before I get my hand slapped again......... ya know about data and opnions etc......    

[Dynoroom]

You don't electronics to get a turbo to work, just look at the 4 cylinder turbo offy's of the late 60's and 70's.  They were getting close to 1000hp and more without electronics. There is a whole plethora of parts availabel to do it without electronics. Maybe Rex will chime in with his story about the runaway turbo Offy on the dyno.  Tony

Yep, you might even look at the 2012 rule book. See D/BGMS. That was set with draw thru carbs in 1988! How they do that???     

[Bob Drury]

  Tony, I don't think anyone is implying that you have to have electronics to make a turbo work.
  In fact it may be harder to make work with electronics, but with the addition of computer controlled timing and fuel systems, tuning has got to be a lot easier.
  In the classic classes we are allowed to download data but once we make a tune up decision we are pretty much stuck with it for the run unless you are really fast with jet changes and a timing light.......
                                       Bob 

[interested bystander]

In the interest of accuracy I'm challenging Jl222's claim re: WW II engine designers  preferring centrifugals to turbos'

I'll cite ONE case : the Wright Cyclone 3350s powering the B-29

Each of these four engined bombers had TWO turbochargers per engine. (General Electric built).

Couldn't find how many Wright (Curtiss- Wright) built, but DODGE  built 18,000+ of them (which were better engineered that the Wright version).

Oh yeah, and then there was the preceding  B-17. And a BIG,FAST fighter plane called the THUNDERBOLT that had it's turbo back behind and under the pilot with a huge duct running forward to the motor.

As I recall the B-17 and the P-47 had one turbocharger each.

There were probably others with turbos, DONTCHA THINK?
 

[hotrod]

The Pratt & Whitney R-2800's used a centrifugal super charger not a turbocharger.
It was used to power the following aircraft (among others)

A-26 Invader
B-26 Marauder
CH-37 Mojave
Convair CV-240 family
Curtiss C-46 Commando
Douglas DC-6
F4U Corsair
F6F Hellcat
P-47 Thunderbolt

The Pratt & Whitney R-2800 in the F4U Corsair is an example of the two-stage supercharger. The huge casting behind the last row of cylinders is almost entirely a two-stage supercharger. Output air from the first stage is ducted to the second stage for further compression. In the gear driven two stage superchargers the gear ratio for the low blower was 7.6:1 and for the high blower the gear reduction was 9.9:1. Selection of low blower or high blower was accomplished by the pilot engaging the clutch for the high blower unit.

http://www.connecticutscorsair.com/engine_history.htm


There were a few engines that use turbochargers but the shortages of the exotic alloys needed for reliable high temperature hot side turbines made them harder to build than the simple gear drive superchargers used in many aircraft engines. especially early in the war.
All 14,000 P-40s got gear-driven superchargers on their Allison engines for this reason although turbocharged Allison engines were used in high performance variants of the P-38.

The R-4360 Pratt & Whitney Wasp was supercharged with a mechanical supercharger geared at 6.374:1 ratio to engine speed provided forced induction.

One problem is that it is hard to make absolute declarations regarding construction of almost all WWII performance aircraft as they were all under constant development and one service might use a mechanical supercharger and the same engine might use a turbocharger in a different military service.

http://en.wikipedia.org/wiki/Lockheed_P-38_Lightning
In March 1940, the French and the British ordered a total of 667 P-38s for US$100M, designated Model 322F for the French and Model 322B for the British. The aircraft would be a variant of the P-38E. The overseas Allies wished for complete commonality of Allison engines with the large numbers of Curtiss P-40 Tomahawks both nations had on order, and thus ordered for the Model 322 twin right-handed engines instead of counter-rotating ones, and without turbo-superchargers.

http://books.google.com/books?id=8bSYNEWaRfYC&pg=PA8&lpg=PA8&dq=pratt+and+whitney+gear+driven+supercharger&source=bl&ots=_0I3buRBDz&sig=wGLch1L2nw-LeVwHblDPFFHjHc4&hl=en&sa=X&ei=tmqOT-vnFYTY2gXbz-TwCw&ved=0CE0Q6AEwBA#v=onepage&q=pratt%20and%20whitney%20gear%20driven%20supercharger&f=false

Larry

[generatorshovel]

This link is loosely related to this thread ,and makes good reading.
http://www.spaceref.com/news/viewsr.html?pid=4051

[1 fast evo 2]

38... I ussually start with FUBAR and replace and rebuild until I get something decent. Sometimes its just an expensive FUBAR in the end.

Bob:
I understand about no electronics. That is clearly stated in the rule book. That also makes the tubro option a challenge. Manually adjusted pop-offs and waste gates present serious challenges over electronically controlling these functions. We plan on spending a lot of time on the dyno working through the tune up.

My other concern is dumping the exhaust out of the fenders verus under and out the back of the car. I know this topic has been covered in other threads but I plan on looking that topic up as well.

38  sorry to hyjack the thread. Good luck with the conversion.

Bill

Hey Bill how ya been?
Mike Reichen here. I met you at Maxton last year I believe. I drive the evo 2 mitsubishi.
Are you still working with Matt?
If so I would follow his lead. The turbo setup can be made to work in what ever situation you need. ie class, engine size, hp output, effieciency you need. Making it work without electronics shouldn't be any real problem it may just take a little longer.


38flattie- 1st off good luck with your project.
1 thing you need to understand is that all boost pressure is NOT equal. You can make 100 hp or 1500 hp at 14.2 psi.
 If you are shooting for a particular hp # so as not to over strain your engine you need to pick a turbo that will get you there in the most efficient manner and then comes the hard part( don't turn it up as there will be a whole lot more power there just waiting and tempting you) You need to deal with a specialist when deciding on a turbo for your set up as they can be tailored to do just about anything you like but if you deal with the wrong person they can make your car an under performing not fun to drive pile.
The rite turbo will make more power and be easier on your engine at the same time.

P.S.-I thought this was SPEED week not a car show.
Do you want to go fast, or look cool ( a blowwer sticking through the hood= cool, not so good for aero though.
                         Mike Reichen