BACKNBLACK
Enthusiast
How come all the funny and dragsters are Super Charged?
If TT setups are better then Super Chargers
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Vic
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Better low end torque, for greater off-the-line response?
CHAD
Enthusiast
Better low-end torque with a SC?
Turbos are outlawed in many classes because they would be an unfair advantage over evry other power adder.
Turbos are outlawed in many classes because they would be an unfair advantage over evry other power adder.
Torquemonster
Enthusiast
The long answer would take a while to write.
The short answer (which is a little over-simplified) is - "tradition"
Turbos will make more power in theory, but while they once suffered from "lag", now that has been conquered. Now they suffer from prejudice from sanctioning bodies that penalize those that run them in the few classes that allow it at all. Top Fuel does not permit them, nor does Top Alcohol to the best of my knowledge.
Cars like the Monte Carlo Mike Moran runs suffer weight penalties verses the blower and nitrous cars. Nobody is willing to go head to head against a turbo max effort car on an equal footing it seems.
In Top Alcohol - turbos could rule the tracks if given an open door and free reign without a weight penalty once given time to catch up the technology (remember the blowers have had 50 years experience behind them - turbos would only need months to match then slam dunk the blower cars on an equal footing).
In Top Fuel - the main power source is chemical not boost... and the engines run so much fuel they verge on hydraulicing right now - so how would higher flowing turbos help? In theory higher flowing turbos and higher boost would speed the flow up and allow more fuel and air - but in real life - the blown fueler engines can blow the tires at 300mph as it is... so it is the chassis and tires that need technology improvements - not more power.
For race gas or methanol - a large well built turbo engine setup will exceed a blower engine by several hundred hp in all out effort. That is of course assuming the turbo engine builder knows how. You could count those that could on the fingers of one hand. Blowers therefore are easier because a lot more people have played with them and know how to make them work. A "reasonable" street/strip turbo engine will make 4hp per cubic inch on gas, a good race OHV one will do a lot better than that... over 6hp, with high tech engines doing better than 12hp per cube.
The short answer (which is a little over-simplified) is - "tradition"
Turbos will make more power in theory, but while they once suffered from "lag", now that has been conquered. Now they suffer from prejudice from sanctioning bodies that penalize those that run them in the few classes that allow it at all. Top Fuel does not permit them, nor does Top Alcohol to the best of my knowledge.
Cars like the Monte Carlo Mike Moran runs suffer weight penalties verses the blower and nitrous cars. Nobody is willing to go head to head against a turbo max effort car on an equal footing it seems.
In Top Alcohol - turbos could rule the tracks if given an open door and free reign without a weight penalty once given time to catch up the technology (remember the blowers have had 50 years experience behind them - turbos would only need months to match then slam dunk the blower cars on an equal footing).
In Top Fuel - the main power source is chemical not boost... and the engines run so much fuel they verge on hydraulicing right now - so how would higher flowing turbos help? In theory higher flowing turbos and higher boost would speed the flow up and allow more fuel and air - but in real life - the blown fueler engines can blow the tires at 300mph as it is... so it is the chassis and tires that need technology improvements - not more power.
For race gas or methanol - a large well built turbo engine setup will exceed a blower engine by several hundred hp in all out effort. That is of course assuming the turbo engine builder knows how. You could count those that could on the fingers of one hand. Blowers therefore are easier because a lot more people have played with them and know how to make them work. A "reasonable" street/strip turbo engine will make 4hp per cubic inch on gas, a good race OHV one will do a lot better than that... over 6hp, with high tech engines doing better than 12hp per cube.
carguy07
Viper Owner
Rules dictate it, they are cheaper and more consistent.
BACKNBLACK
Enthusiast
Carguy the SC is cheaper?
weed43
Enthusiast
Do not, the TT generate more heat then SC engines which the Viper already has a problem.
Paul Hawker
Enthusiast
Something often ignored is the driving experience is quiet different with the two systems. The Turbo's chop up the sound, so the auditory experience is different than with the Superchargers more open exhaust systems.
This "better" thing gets way overblown. (Pun intended). If you want to know which is "better" you need to qualify what you mean by better. Faster, Cheaper, Lighter, better economy, less lag, cooler running, better at drags, road course, street. Lots and lots of "betters".
This "better" thing gets way overblown. (Pun intended). If you want to know which is "better" you need to qualify what you mean by better. Faster, Cheaper, Lighter, better economy, less lag, cooler running, better at drags, road course, street. Lots and lots of "betters".
Tom F&L GoR
Enthusiast
I think carguy is on the right track - it's the NASCAR mentality of the sanctioning body. By keeping things mechanically straightforward with minimal electronics, the rules are easier to write and enforce. You can regulate a blower drive pulley size easier than manifold pressure (just ask the Indy guys when Honda had a "cheat" for the pop-off valve.)
I'll challenge the TT advocates now: Ultra high manifold pressures require some interesting ways to cool the intake charge. While nitromethane has a higher latent heat of vaporization than gasoline, it is nowhere near that of methanol. So while I think ultra high power is achievable in a TT engine with methanol, I suspect that a TT with nitro or gasoline will have the same tuning issues as a supercharger. In other words, it's the fuel that is the limit rather than the boost system.
Anybody have information to show a "no holds barred" TT over a supercharger using the same fuel?
I'll challenge the TT advocates now: Ultra high manifold pressures require some interesting ways to cool the intake charge. While nitromethane has a higher latent heat of vaporization than gasoline, it is nowhere near that of methanol. So while I think ultra high power is achievable in a TT engine with methanol, I suspect that a TT with nitro or gasoline will have the same tuning issues as a supercharger. In other words, it's the fuel that is the limit rather than the boost system.
Anybody have information to show a "no holds barred" TT over a supercharger using the same fuel?
Paolo Castellano
Enthusiast
**** 53, turbo Vipers actually run cooler due to the fact that they are compressing air only under load(under light cruising, the turbos are just along for the ride.
Superchargers are compressing the air anytime the crank is spinning. Due to this, turbos are actually easier on the motor than the blowers not to mention there is no stressing the snout of the crank(several supercharged Vipers have actually snapped the snout off the crank).
Casey
Enthusiast
More heat where?
My engine temp runs cooler now with the TT than with the SC that worked the engine harder.
Tom F&L GoR
Enthusiast
Superchargers rotate all the time, but at part load can't be doing much compression work. They **** against the closed throttle bodies, so there is manifold vacuum in front of the supercharger inlet. Unless the engine is under load, the manifold pressure on the downstream side is still less than atmospheric. Otherwise, how could the engine idle...
So, back to drag racing, where it's always under load...
So, back to drag racing, where it's always under load...
BACKNBLACK
Enthusiast
I think I know what setup i'm going with.Thanks for all the information. I took consideration on street and all.
Chuckie baby see you this fall.We are going all ballz out brother. Put your magic on the car
Chuckie baby see you this fall.We are going all ballz out brother. Put your magic on the car
Torquemonster
Enthusiast
Tom there were some experimental turbo Top Fuelers running a decade or so ago. They gained around 500hp over the blower engines, but could not peak to their potential because back then there was no fuel system in existence that could feed them.
They also had not got the launch issues as sorted as they do now - so they lost a tenth or two at the start line but had the most awesome top end.
Today - I think you are right as far as nitro goes - it is fuel limited and tire limited. When tires and chassis can take more - then it will be time to gain more power. Even the blowers are not at their limit of technology as the PSI will outboost the screw blowers Top Fuel has mandated... but PSI blowers are outloawed in Top Fuel.
Turbos will still beat a PSI however on other fuels. Find me a blower engine that can exceed 12hp per cube ON GAS!!! I'd be impressed if you can find one that gets within 20% of that.
They also had not got the launch issues as sorted as they do now - so they lost a tenth or two at the start line but had the most awesome top end.
Today - I think you are right as far as nitro goes - it is fuel limited and tire limited. When tires and chassis can take more - then it will be time to gain more power. Even the blowers are not at their limit of technology as the PSI will outboost the screw blowers Top Fuel has mandated... but PSI blowers are outloawed in Top Fuel.
Turbos will still beat a PSI however on other fuels. Find me a blower engine that can exceed 12hp per cube ON GAS!!! I'd be impressed if you can find one that gets within 20% of that.
Tom F&L GoR
Enthusiast
The turbo F1 engines were 1.5L (91 cubic inches) and turned up to 1100hp on gasoline (sort of) to qualify, so there's your 12hp/in. I think they did it with turbo because it's smaller and lighter than the positive displacement pump of a supercharger.
A few years ago the top fuel engines were approaching 8000 hp from a 500 in3 hemi. Maybe I'm answering my own question, since I was going to say that the supercahrger has to be pumping in enough air, therefore it would only be a matter of supplying the fuel. But then nitro brings it's own oxygen, so maybe a supercharger is somehow limited after all.
Haven't discovered the fundamental reason yet - seems if you were an intake valve, combustion chamber and piston, you wouldn't know which was feeding you.
A few years ago the top fuel engines were approaching 8000 hp from a 500 in3 hemi. Maybe I'm answering my own question, since I was going to say that the supercahrger has to be pumping in enough air, therefore it would only be a matter of supplying the fuel. But then nitro brings it's own oxygen, so maybe a supercharger is somehow limited after all.
Haven't discovered the fundamental reason yet - seems if you were an intake valve, combustion chamber and piston, you wouldn't know which was feeding you.
This debate has gone on since the beginning of time. I've seen it on the mustang boards, on the Vette Boards (going on as we speak), hell on every type of car board that I've frequented...at the end of the day, there is no "right" answer. Each form of forced induction can be made to go insanely fast. There are pros and cons to both. Turbos are more efficient (less parasitic drag on the engine) but packaging and heat management can be challanging. Also turbos are a bit more complex (i.e. not many people, even the ones that use them, understand much about the proper sizing of turbos for a given application). Superchargers can also do the job, but fighting belt slippage/breakage problems and the constant load placed on the snout of the crank are some negatives...an lets not talk about the debate amongst s/c guys...centrifugal, roots, twin screw, whipple...
Most important thing is understand what you want and get the system that best meets your needs.
Most important thing is understand what you want and get the system that best meets your needs.
JZ 97 SS 1500
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Turbos have been outlawed....plain and simple. Look for NMRA and probably Pro-Mod to outlaw them soon as well. Every class they enter they dominate.
As for F1, I think you guys are talking about the 80's. Thats when Keke rosberg, Gilles Villeneuve, Alain Prost, Senna...etc ruled the track. In qualifying trim their 1.5 liters were putting out over 1400hp and in race trim over 1250hp. Those cars ran on exotic fuels,it was a blend of toulene, n-heptane and some traces of methanol and benzene...maybe some other chemicals.
JZ
As for F1, I think you guys are talking about the 80's. Thats when Keke rosberg, Gilles Villeneuve, Alain Prost, Senna...etc ruled the track. In qualifying trim their 1.5 liters were putting out over 1400hp and in race trim over 1250hp. Those cars ran on exotic fuels,it was a blend of toulene, n-heptane and some traces of methanol and benzene...maybe some other chemicals.
JZ
Vic
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Chad, When do your turbos kick in? Can you post your dyno chart? I had to ask....:-D
What about turbo back pressure, heating up the exhaust valves? Was a time when well-built turbo charged engines had sodium filled exhaust valve stems, to help radiate the heat quickly from the valve seat. Is this still a common practice with turbo charged cars?
Paolo, What would it take to get your kit CARB certified? Maybe its easier than you think? [/blatant encouragement]
What about turbo back pressure, heating up the exhaust valves? Was a time when well-built turbo charged engines had sodium filled exhaust valve stems, to help radiate the heat quickly from the valve seat. Is this still a common practice with turbo charged cars?
Paolo, What would it take to get your kit CARB certified? Maybe its easier than you think? [/blatant encouragement]
Torquemonster
Enthusiast
it takes high rpms, and you'd never get an OHV engine to rpm high enough to make that power.
Tom - the answer is staring you in the face. Yes you can get a blower so big it can pump as much air as any turbo - but what happens then?
the power will be limited by what the engine can take from whatever supplies the air LESS what it takes to pump the air... therefore the parasitic loss is the major difference between the two approaches.
There are several other differences but this parasitic loss is the only significant difference in power potential between the two - if both are done to the same high standard. There is your answer. A blower no matter how good - can not over come the parasitic loss of driving it when compared to an equal capacity turbo system that is as well designed and matched... more-over the turbo boost progression is GEOMETRIC... the blower is LINEAR... hence the hp/torque area under the curve will be FATTER with the turbo engine... simple.
Having said that - in real world conditions - Earl is right - either one has its pros and cons and either can be faster depending on many variables.... but if you want the most power and the fattest curve - on any given octane - there is one answer if there are no restrictions. Parasitic loss and geometric vs linear boost.
Tom F&L GoR
Enthusiast
pppphhhhhtttt... if the area under the curve counts, then the "linear" low RPM blower performance exceeds turbos boosting at "geometric" rates for high RPM. You can't get both with only one system. And backpressure isn't free energy, either. Saying a blower is no good compared to an "equal capacity turbo system" (whatever that means) isn't the kind of answer I was looking for. Earl is right; we don't know enough.
Not sure what is meant by "geometric." Guess maybe I need to go back to school some more. But I did take a graduate class on turbomachinery (power and propulsion major) so I believe I understand the basic principles of turbine devices. First thing is all variable speed turbine devices provide a non-linear speed-pressure-flow curve. The benefit that turbochargers have over centrifugal superchargers is that the coupling of 2 non-linear devices can produce a more linear result. Displacement superchargers such as the twin screw provide a near linear response. But the turbos can also be matched to provide a more non-linear result, allowing higher boost at higher engine speeds where detonation potential diminishes. Maybe this is what is meant by "geometric" though all turbine devices work based on geometry.
As indicated above there is no free energy. The primary loss of a turbocharger is the energy related to backpressure increases. You can think of an engine as an air pump. Add a restriction in the system (the exhaust turbine) and the energy required to flow air through the system goes up. That energy is typically called pumping loss. Along with the backpressure is retained heat in the exhaust system and a greater amount of reversion. The reversion may by itself be a limiting factor in a top fuel engine. Very difficult to time the exhaust valve closing to prevent reversion, and thus internal EGR, under all speed and load conditions. That may limit cylinder filling versus a supercharger which can minimize reversion potential. Given how close they are to hydrolock, that additional variable may be difficult/impossible to counteract.
All-in-all present day turbochargers are more efficient overall than superchargers. That means that for a combustion limied engine the BMEP will be higher for a turbo than a supercharger for an equal IMEP. That also means a better FMEP and thus fuel economy. Things start to get copmplicated at this point because for a given IMEP combustion characteristics are quite different. An equal boost will not provide an equal IMEP. First, the pressure differential across the engine is different due to the turbo restriction. But in addition the the flow characteristics, required valve timing, retained heat, etc all together provide a significant impact on the combustion characteristics. In general a turbo requires more fuel cooling at the same IMEP. That decreases the fuel consumption aspect and makes turbocharging with high efficiency a significant challenge.
I could go on and on but I think it just does not matter. In the end they are different forms to produce the same end product. Some may be more suited for one use than another, as they are not exactly equal. LIke top fuel where cylinder filling is the most critical versus F1, where fuel economy and non-linear characteristics may be desired. But in general a given sport cannot afford to have these competing technologies acting against one another creating winners and losers (from an engine design and builder perspective). That drives up costs considerably as we have seen in F1 and CART over the years.
Just my $0.02
As indicated above there is no free energy. The primary loss of a turbocharger is the energy related to backpressure increases. You can think of an engine as an air pump. Add a restriction in the system (the exhaust turbine) and the energy required to flow air through the system goes up. That energy is typically called pumping loss. Along with the backpressure is retained heat in the exhaust system and a greater amount of reversion. The reversion may by itself be a limiting factor in a top fuel engine. Very difficult to time the exhaust valve closing to prevent reversion, and thus internal EGR, under all speed and load conditions. That may limit cylinder filling versus a supercharger which can minimize reversion potential. Given how close they are to hydrolock, that additional variable may be difficult/impossible to counteract.
All-in-all present day turbochargers are more efficient overall than superchargers. That means that for a combustion limied engine the BMEP will be higher for a turbo than a supercharger for an equal IMEP. That also means a better FMEP and thus fuel economy. Things start to get copmplicated at this point because for a given IMEP combustion characteristics are quite different. An equal boost will not provide an equal IMEP. First, the pressure differential across the engine is different due to the turbo restriction. But in addition the the flow characteristics, required valve timing, retained heat, etc all together provide a significant impact on the combustion characteristics. In general a turbo requires more fuel cooling at the same IMEP. That decreases the fuel consumption aspect and makes turbocharging with high efficiency a significant challenge.
I could go on and on but I think it just does not matter. In the end they are different forms to produce the same end product. Some may be more suited for one use than another, as they are not exactly equal. LIke top fuel where cylinder filling is the most critical versus F1, where fuel economy and non-linear characteristics may be desired. But in general a given sport cannot afford to have these competing technologies acting against one another creating winners and losers (from an engine design and builder perspective). That drives up costs considerably as we have seen in F1 and CART over the years.
Just my $0.02
Vic
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Logrithmic? Exponential? Sinousidal?
Marmalade?
Thats all the big words I know....I'm out.
Marmalade?
Thats all the big words I know....I'm out.
Torquemonster
Enthusiast
Ron gave a great post.
Tom - nobody said a turbo runs on free energy.
Off idle excepted - I disagree that a typical centrifugal blower makes more bottom end than a turbo - but let's agree that it does. So what?
Whatever boost method is chosen, from the moment a race car of ANY motorsport takes off by dropping the clutch or stalling the converter - until shift point - the engine is in its high mid to top end power range. Any BOTTOM END advantage of either method is irrelevant in racing.
Having actually project managed, R & D'd and pioneered an engine combo that used a PSI blower which pulled 54lb boost on a 494 cubic inch wedge engine at 9500rpm - I am not rubbishing blowers...
Nevertheless - my money is on the fact that the same engine CAN make more power in its operating range on turbos than on a blower... in EXPERT hands.
That opinion is in good company from people who can prove it.
I have no experience with nitro.
Step back from the microscope and look at the forest guys. The pumping loss of a turbo is minor compared to the losses driving a pump...
One proof = turbos can seize and the engine will still run fine.
yes there is turbo back pressure but it's impact is not massive on a well designed system.
I personally achieved 60mpg in a turbo car - something its naturally aspirated version could not. Why that can happen is another story.
Turbo engines can run correct (not rich) mixtures and cruise lean. They can be very fuel efficient. The typical extra fuel is a cheapskate fix 99% of tuners use because ...well, it is just easier. There are better and safe ways to maintain correct mixtures without excessive EGT's.
Vic - geometric boost progression simply means that the rate of boost increases as a function of LOAD and engine speed, not just rpms. In other words you can go from 1-2 lb boost to 20lb boost in a very small rpm band - which makes a very steep and then fat power curve.
You can imitate this to some extent with a centrifugal blower but you can't match the turbo boost delivery. You can overdrive a blower to come in quickly - but then you end up overspinning it at the top end... therefore most blowers will be setup to retain efficiency on the top end - otherwise they will die young.
A blower is easier to go fast with because the more linear power can be used, whereas the turbo can hit so hard it blows the tires and has to be softened... which can be tricky. The 2 liter turbo Cosworth Sierras gained 300-400hp in 500rpm which made them violent on the road courses, but unbeatable when mastered.
a turbo engine definitely requires more tuning because of the above.
A blower engines more linear power progression makes tuning fairly straight foward and predictable...
So - in summary - a turbo will have more power potential - but most tuners will get better and easier results from a blower in drag racing - because turbo tuning and setup is an expert field.
The belts used by street centrifugal blowers are a problem at high power levels. The big Whipple and Roots type blowers run sturdy belts - but will have your engine top higher than your Viper roofline - not very practical and really stink for handling.
Therefore - in the Viper world there is no comparison. Anything over 800hp at the crank is turbo all the way in my opinion... unless you just like the whine and more open exhaust noise of the blower setup.
For most - you'll only break one belt or have to retighten it once after being beaten by a turbo Viper at the same boost to figure it out.
I've done many hundreds of thousands of miles on turbo gas engines with only 2 failures... one after 125,000 miles on original seals, the other was a bad turbo rebuild which blew an oil seal after only 1000 miles. We ran a blower to run 6 seconds at 200mph on the track for cost and simplicity reasons only. We knew we could make more power with turbos.
Look at some Viper blower dyno graphs then consider this. Paolo and Jims TT Viper makes more power than a stock Viper from 2000rpm up (so will most blowers). Then it went on and made 1579rwtq on a tired engine (that is soon to be replaced with something more substantial). Overlay that over the best Viper blower dynos you can find.
The new power figures will be truly interesting.
Look at the old dyno from RSI re Dr Roofs first TT engine, let alone what his new and improved one will be, overlay that over his blower engine. The boost was similar, in fact the blower engine made more boost than the RSI turbo did. Color in the overlap. These are real world results.
Look what Chads car has achieved despite the design limitations of mounting turbos down by the oil pan. 8.26 seconds at 176mph.
Imagine if those limitations are removed.
Of course - skeptics will say you could go as fast with a 30psi Procharger.... well, yes you could. But not at 20psi and a base engine around 550rwhp.
