Well but that means unless all drums of all dynos have the same inertia, there's no way that you can compare the data from different dynos. You can only compare data taken from the same dyno, but I guess that's what you and others said anyway.

Yep. The tools used to make a measurement have an effect on the thing being measured.
This is known as the "Heisenberg uncertainty principle."

That's why they have "Heisenberg Compensators" equipped to the Enterprise on Star Trek!

Yep, uncertainty would bug Spock no end, so they had to compensate for it.

Does anyone know what compression ratios (compressor and engine) and what compressor types NHRA top fuel cars run?
Also how does the flash point of nitro compare to pump gas (knock sensitivity)?

(Just for curiousity, I'd like to know what compression ratios of compressor and engine you'd run (what range) in order to generate maximum power output regardless of engine efficiency.)

As you would expect those things are kept secret by the teams. As near as I can get is only aprox. They run the piston very far down in the bore, that we can see when they rebuild between rounds. A good guess is around 6 to 1.
Thhey run a industry built extended version of the GM 6-71 or any 71 series engine for that matter. It just has a 19 inch rotor length. They call them 14-71 but there really never was such a thing.

These are roots blowers. They run up to 40psi which is a point where the efficency of the blower is about what the engine is. Somewhere around 38%.
This is obvious as if they turn them any faster they go slower. I cannot make the math come out as bad as it is.

They are getting over 500f increase out of the blowers. Yet they need over 1000 hp to turn them. This is a given as they have run them on the bench. I was witnes to the first bench testing of a drag race supercharger. Around 1971 my freind Larry Bowers who built drag race blowers built a test stand. He wanted to test his blowers against others.

This was still the era of the 6-71, Bowers built his own magnesium cases but used GM rotors. Running this test stand he put a Ford 302 engine. When the first test was run the engine just boged with any pressure was put on the thing. A 351 C was put on the stand. This engine could get up to 7 psi from the blower before giving in.

That is as far as that stand went. A boat racer built another stand a few years later and used a big block 427 Chevy. He tried to use an 8-71 as was then the style. It couldn't pull up to speed. So he put a full race 492 inch engine on it that made over 600 hp. They could not pull full speed and pressure.

Since then I have heard numbers like 800 to 1000 hp from well informed racers. One such is John Force who built a blower test unit but will not give out numbers. However his crew chief did hint to me that the 1000 number is not to far off.

These blowers are only efficent up to about 5 psi. But the NHRA will not allow any other blower to be used. They just don't want them to make any more power. I proposed my blower to them just on saftey reasons. You would not have al those blower explosions. If they wanted to limit power they could do what other sanctioning bodys do, restrict the intake size.

Those blower explosions are from flash point being reached in the manifold. They have readings of about 200f in them. Acording to that same sorce, but that is with 25% of the fuel being put in before the blower. This is what takes all the heat out of the air. But what happens when a spot of air slips by without getting some fuel, it explodes that's what.

They will not listen, they don't want to change anything orr put anyone out of buisness. They claim it is a valve hanging open. Now if those guys can't set up a set of heads after all these years I find it unrealistic. They have spring you could put on your RX8 for suspension springs. Heavy duty ones at that. Well maybe not but they have about 300 lbs or more on the seat. It takes a special spring compressor to put them on.

15 years ago they were running about 21-23 psi. They now are limited to 90% nitro, I think maybe they lowerd that to 85% recently but I'm not sure. That means the rest is alcohol. The flash point of these mixes is something I tried to find out but never got an answer. The only one who really might know all these answers is Prof Dean Hill. I tried to get to him at the university but he was on some sort of sabatical.

That's all I know.

Your second q does not state if you were talking race cars or street.

I may have posted this before or not, but this is the proposal I gave the NHRA

RP, you know the problem with the NHRA is the same problem that is in all other pro sports. Drag racing under the NHRA is not about car nuts having some friendly competition any more. It's all about MONEY. Just like NASCAR ought to remove the letter'S' from their name.

Wally Parks built a good organisation, but I don't think that he ever wanted to price out all the guys who build their own cars, drive them every day, and like to race them on weekends. Nowadays the NHRA rules are made to benefit the pro teams. Innovation is not encouraged. Between the NHRA and the state laws I'm surprised the term "Hot Rod" even still exists outside of museums. Current NHRA cars are not hot rods; they are purpose-built race cars.

I'd better get down off this soap box before I fall and hurt myself.

PS -- If anyone is interested, my 8 is for sale.

Why?

Firstly - what RAP says is all good stuff.

Secondly, the below "facts" don't directly answer your question, but give you some interesting stats...

Source: http://www.ftw.com.au/content/view/100/50/ but I have seen it quoted in various places in pretty much the same form.

It still stands the hairs up on the back of my neck when I read it :D

Cheers,
Hymee.

PS - I know of some rotors "unnoficially" running around 40PSI.

Thanks Richard, that was certainly interesting.
So if I understand this correctly if they could use a more efficient compressor they could produce more boost with the same 1000HP with that extra boost they could increase the total power output and when they can increase the total power output they can use more power to run an even more powerful blower and so on.

Regarding the 2nd q. The compression ratio of the top fuel class should be an indicator at what compression ratio an engine is run to maximize its power output. But the fact that they are forced to use roots blower means they don't actually have hit the limit of what would be possible with a supercharged (not turbo) piston engine. (I just remember that you mentioned that when you lower the compression ratio you can increase the BMEP).

Just a sidenote. I guess on a racing boat you could use a more effective air to water intercooler which means that a racing boat engine should theoretically be able to generate more power/displacement than an engine mounted on a car.

Hymee thanks for that extra information. Believe it or not, but I actually went to a drag race event not far from Perth (WA) 9 years ago. :D

If manifold explosions are so common, why didn't they place the roots blower in front of the engine and have a pipe between supercharger and manifold (as a weak link)? (I think you are (Richard) suggesting something like that in your word document with the axial flow compressor.)

Actually I think you could say this is true with the Formula 1 as well. For instance it would stimulate innovation if they would limit the amount of fuel they're allowed to use (in order to reduce the speed of the cars.) instead of limiting the size of the engines. Of course one could say it would make it too expensive, but I guess they could solve that if the organizers would share some of their profits with the teams.

Instead of a pipe, they have a think on the intake manifold called a burst plate. That is to limit the pressure inside that induction tract. Like a saftey valve.

We are pretty fortunate that a lot of the technology/R&D that has gone into F1 in years past has filtered down into the sorts of things we have standard on our cars today. I guess we can thank the fuel limits etc during the turbo era for that to a certain extent.

And that is one more time than I have been to the drags in Perth.

Cheers,
Hymee.

There was at one time i think in the early '60's or late '50's a front mounted blower. trouble was it couldn't use overdrive. Known as the Potvin it was used at Bonniville due to the lower profile.


What is the limit of supercharging? Was that a question?
Well the Novi ran 60psi. The race Merlins that Zeuschel built for Reno ran up to 50psi. So we havn't reached a limit of the actual supercharging it's just holding it all. How do you hold a head gasket inthere? Well the novi didn't have one, like the Offy it had the head cast with the "bank". You ground the valves through the bore. Then the "bank" slips into the crankcase.
This was done on some Merlin but not the last ones, there the sleeves were set to be about .004 above the face of the bank. This required very carefull build up.

Funny thing is I just read about a shop prepairing Honda race blocks who is doing this same thing. Ferrari had a unique way on the 512M LeMans cars. I saw Penske's engine being built and Traco couldn't get it to seal. Seems they laped the sleeves into the head. They had to get hold of Ferrari to tell them that, no one knew.

The heat is a thermal limit problem for internal parts. Hoowever we have new coatings that might help. Remember in a dragster the pistons are scrap by 4 seconds. This of course cannot be used in any other form of racing. I can picture it now pit crews scatered around the track at Indy say 10 times a lap they stop for pistons.

Your thought about boats is a good one. There is an unlimited heat sink right under the boat. Nice 60f water to run in any sort of heat transfer device you have.
But they still try to run the roots blower on offshore craft?????????/ Seems a strange thing, yet you have to realize that there is no other hardware on the market for them. Teams don't want to be the one to waste a season developing new things. Usually it means a season of learning the new parts and winning is rare. Unless it is so well developed out of the race arena by a development team who is a part of a running race team. Just sounds like a lot of money for racing that doesn't pay anything.

So what would I use if given the choice? A Lamborgini 500 inch 60 degree V-12 four cam, four valve race engine. these make over 900 hp unblown. They run two of them in a cat style 50 foot off shore boat in the Itailian series. Now they don't allow supercharging of over 350 in engines, So if Lambo could just build these off there 6 liter car engine platorm and I'd build some superchargers that put out whatever it took to get say 1100 hp. We could just take extra blowers with us some with more stages to put out boost in 5 psi steps. Untill we beat everyone. Enough cooling could be had tio get the air down close to the water temp. That might not be practical as there would be to much IC to go through and might hurt the response.

Anyway if you could hear two of those engines running 7000 RPM through tuned exhaust, now that is music. The 12's I'm talking about. It would be a sin of proportion to muffle those with a turbo. You might get a visit from the Pope.
Italians are very romantic when it comes to motorsports.

There is a reason why the boat engine can't make the power of say a sprint car or equivlant other engine say F1. There is no other place except aiir racing that the load is constant. You leave the throtles open for extended prriods of time. There are no corners that you need to slow down and shift. you don't get to lift because your drafting. You just have full power all the time. The engines just can't take it. I learned this lesson when I was building blown engines for the sport offshore guys.

I had a failure of one engine until I learned that they take off out of Palm Beach or such and lean the throtles open until they get to Bimini. I had to start building them with one point less compression and just not tell them about it.

Just not enough cargo space for guitars and accessories.
The car is great otherwise.

Thanks again for that extra information.
I guess I just wanted to know how you would supercharge an engine to maximize its power output without causing detonation, but then I realized you can't take top fuel cars as a benchmark, since detonation probably doesn't matter in their case anyway. And I believe you basically answered that question. At least with an axial flow supercharger there's not really an upper limit as long as you can cool the intake charge well enough it won't detonate, it will just generate tremendous pressures and temperatures and that's what sets the limit.

Also I agree that the valve failure doesn't make sense. The exhaust valve is exposed to much higher temperatures than the intake valve. So I guess if there was a valve failure at all it would be the exhaust valve not the intake valve anyway.

And I read your article about engine mass flow and I agree as well, volumetric efficiency is not precise.

Actually I'm not sure whether you can say 25% less energy being produced. Maybe 25% less energy being consumed. I thought that most of the fuel is just used to cool the intake charge and the engine itself and ends up unburnt in the exhaust?

Talking about speed aircrafts I wonder why aircrafts with push and pull propellors are not more popular?
http://www.aeroflight.co.uk/profile/d335hist.htm

Well, Cesna makes one. Voyager the plane that went around the world non stop was that way. There are probably more. Just that new prop planes are not being designed for commercial use. There is also a home built plane designed by the same guy who did the round the world plane, Burt Ratan.
It uses a push prop.
Just doesn't seem as good a design, kinda like high wing low wing. The high wing lets the plane hang, making it more stable. But stble is less nimble or fighter like. :confused:
Same might go for pusher prop, but certainly Ratan knows more than I. The new spy drone used by the DOD is rear prop.

Having the noise behind the cabin is nice. Ah wasting time, need to go get shifters done. See ya.

I can't find that plane on cessna's website... by any chance you know what model it was or will be? I've been silently taking the flight stuff in... real interesting..

It's the Cessna skymaster. They don't build it anymore.
http://www.skymaster.org.uk/

I think Adam aircraft is one of the few that sells an aircraft with push pull propeller.
http://www.adamaircraft.com/Ownershipa500.asp
(I believe it was also designed by Burt Rutan).

I know they're around I just don't see why they're not more popular. Considering it's advantages in efficiency and turning (no angular momentum).

Since this thread is also about aircrafts. :)
The push pull propeller would probably be the design you'd choose to reach maximum speed.

Other very efficient aircrafts are canard aircrafts:
http://www.velocityaircraft.com/
Some people fit them with 20B rotary engines.
Canard designs have less drag because all wings lift the aircraft. On a standard designs the rear wing pushes down (more drag), but is more stable.

The very first aircraft (Wright brothers) was also a canard design.

Actually, more lift (+ve or -ve) = more drag. One of the first things we learn in flight school.

Cheers,
Hymee.

Ok, I should have said a canard design needs to generate less total lift in order to equalize the gravitational force because all wings lift the aircraft.
(The same is true for a flying wing aircraft which is even better than a canard design.)
Less lift = less drag

We need another topic for aerodynamics arguments ;)

Actually, the lift generating surfaces on any aircraft, only needs to generate the amount of lift necessary to overcome the mass of the aircraft. It doesn't matter if it is canard, conventional, flying wing - if it weights 1000kg, then it needs to make 1000kg lift.

With the conventional layout, and a properly designed and balanced aircraft, the rear horizontal stabliliser should run pretty much neutral at straight and level. When you want to pitch the nose up, get it to make some -ve lift (decrease AoA), and to pitch the nose down get it to make some +ve lift (increase AoA).

Cheers,
Hymee.