70 replies to this topic

[Robin Fairservice]

That is what I am trying to explain. You can not directly convert one physical quantity into another one. You need at least two independent quantities to combine them for calculation of a third quantity.

Like in this case force * speed = power

The problem is, which "speed"? Power is energy/work per time, so how much energy the engine will deliver to accelerate the airstrem through the engine. Therefore you have to know how much quicker is the air behind the engine than in front of it. This I think is a different kind of "speed" than the travelling speed of the whole machine. Also (being no expert on this) I assume that this speed difference will not be constant for the whole range between "standstill" and maximum speed of the whole vehicle.

Finally, even if you would know this quantity (the acceleration of air through the engine), you would still compare the effective power of the whole set-up of a jet engine to the nominal power given for a piston engine. You could compare it emprically by attaching for example a propeller to the piston engine and then look which revs you need to achieve the same thrust like with a jet engine, but of course you would have a certain loss depending on factors like propeller dimensions or aerodynmic shape.

So I am afraid the answer to your question is "no"...

Read pages 66 and 67 of Sir Stanley Hooker's biography "Not much of an Engineer". There he explains how he persuaded his boss, Lord Hives (Hs,) to go to see Whitle's gas trubine engine which was developing 800 pounds of thrust. He explained to Hs that the Merlin engine in a Spitfire flying at 300 mph, with a 70% efficient propeller, delivers about 840 lb thrust. Hs then made immediate arrangements to go and see Whittle. Apparently a piston engine in an aeroplane doesn't develop thrust until it starts moving through the air.

Edited by Robin Fairservice, 07 January 2013 - 17:16.

[Doug Nye]

I am with Andrew K and John Aston here. Doug - I am just a bit surprised, but you have to try a Top Fuel meeting at least once. I saw the Americans visit the UK in the early Sixties, then went (pilgrimage, really) to the Nostalgia Drags at Bakersfield in 1989 and just a couple of years ago to the FIA Top Fuel Finale at Santa Pod.

Nothing prepares you for the extraordinary impact of a Top Fuel dragster - as another poster said, it is a multi-dimensional experience ... and just when you think you cannot withstand the sound and internal vibrations any longer .... they are through the traps. Thank heavens it only lasts 4 and a bit seconds.

DSJ (quick pause to unfurl worship mat and face East) could see the appeal and I think probably had high regard for George Brown and Ian Ashwell when they dragged bikes in the Sixties. Ands it must be the last FIA-organised event where you can wander through the pits and see a crew rebuilding the motor between rounds, talk to the pilots and etc. Fantastic !

Even after fifty years of spectating at historic racing and making up the numbers on the grid, and seeing and hearing some sensational cars, I still rate the drag racing experience as not to be missed.
Nick

Yes, I appreciate all this about dragsters and drag 'racing' but it's just an activity that strikes me as pointless. I don't have it within me to get excited about so-called 'supercars', either. If a road car can't carry a sheet of 8x4 and at least four people, what's the point? If a car can blast from 0-300mph over a quarter-mile straight, I'd be impressed to see it then take a curve at 200mph, and keep on going for dozens of laps, in competitive company with
others. Otherwise, very impressive for a fleeting second or three...but what's the point? Just a case of different strokes for different folks. Some enjoy white wine, some red, some have no interest in either. Straightline accelerationfests remain, for my personal taste, just a drag. Nobody's perfect.

DCN

[MODE]

Renault reached its higher boost with 5,5 bar at 86 last GP, Australia, by using the qualification turbos initially set for Mexico only. Senna also used these turbos at Estoril during saturday qualify, its max speed was 10 Km/h faster than friday. Like BMW their bench couldn't read more than 1100 Cv. Bmw is known to have reached also 5,5 bar at Monza the same year with G.Berger. The trap speeds during qualifications at 1986 Monza GP tell all about the advantge of BMW at that time :

http://www.gurneyfla...benettonbm.html

[flatlander48]

Alcohol and liquid oxygen? I don't think so.

Rosche did not go into the details of the blend. However, I am pretty sure that was how he characterized it. That is not to say that we automatically should take a literal meaning from his words. It's very possible that he was being facetious much like people use the term Rocket Science, for example. I do have that issue of the magazine, somewhere. I moved a few months ago and all that stuff is still in boxes.

Anyway, January 2001 issue...

Edited by flatlander48, 07 January 2013 - 18:12.

[Lee Nicolle]

BMW used second=hand blocks for their F1 engines as they had been thermally cycled many times and were therefore a stable base for the turbo engine.

While I have no idea of the fact or fiction about the BMW blocks I do know they are quite tough, and also fairly heavy. Someone has mentioned lack of 4 bolt, that is generally a fairly easy conversion, make some steel caps and drill an extra pair of holes in the main web! Any competent machine shop can do it and have done it for decades on all sorts of engines.
Used blocks effectivly heat treat them selves, as do weathering them too, it does make for a more reliable engine, and they do not go 'out of round' in the bores and the main tunnels stay a lot straighter too.
Perkins used to leave their blocks that had already been semi machined out in the weather.
And many 60s-90s engine books have said use the block in your 'shop truck' for a few months then finish to race specs. This will be better than heat treating the block, though that is an essential anyway for serious race engines. This applies to iron blocks, I have no idea on alloy blocks which do flex worse and need more clearance normally in all applications. An alloy sprintcar block will make less power modification to modification than an iron one. But the alloy one will be generally faster as the weight is more important than an extra 10-15 hp max.
Someone mentioned a Merlin, but the reputed 2000 hp is more a stationary engine, and about 3000 rpm really does not count. And the weight really only makes them good for landspeed cars where all that power and torque can be used,,, or aeroplanes! a hotrodder here in Oz has one in a 57 Chev, the most underwhelming thing to listen too really, though in a plane they sound right when making power, easpecially in multiples. I can remember a Lanc flyover when I was a kid and as it climbed it sounded lovely.

[beighes]

Didn't somone once libellously claim that the Foyt V8 had a supply of nitro in a fake fire extinguisher. I'm sure that can't be true but a fun story.

I don't know about the fire extinguisher, but I seem to remember something (pertaining to a NASCAR chassis) about Nitrous being sprayed into the air intake via the head of a pop rivet on the firewall?
Steve

[flatlander48]

While I have no idea of the fact or fiction about the BMW blocks I do know they are quite tough, and also fairly heavy. Someone has mentioned lack of 4 bolt, that is generally a fairly easy conversion, make some steel caps and drill an extra pair of holes in the main web! Any competent machine shop can do it and have done it for decades on all sorts of engines.

From the image I saw (link below), the webs looked relatively thin. The bolts for main bearing caps are not small and I think there wouldn't have been much material left after you tapped the hole. The front and back don't look to be a problem, but I think the middle 3 wouldn't be thick enough.

http://images.search...umb=c6syMjObpWU

Edited by flatlander48, 08 January 2013 - 02:25.

[jm70]

From the image I saw (link below), the webs looked relatively thin. The bolts for main bearing caps are not small and I think there wouldn't have been much material left after you tapped the hole. The front and back don't look to be a problem, but I think the middle 3 wouldn't be thick enough.

http://images.search...umb=c6syMjObpWU

Caption says it's a Datsun block. All the BMW blocks I worked on had no provision for a cam in the block.

[uechtel]

Read pages 66 and 67 of Sir Stanley Hooker's biography "Not much of an Engineer". There he explains how he persuaded his boss, Lord Hives (Hs,) to go to see Whitle's gas trubine engine which was developing 800 pounds of thrust. He explained to Hs that the Merlin engine in a Spitfire flying at 300 mph, with a 70% efficient propeller, delivers about 840 lb thrust. Hs then made immediate arrangements to go and see Whittle.

That is the perfect explanation of what I wanted to make clear.

Apparently a piston engine in an aeroplane doesn't develop thrust until it starts moving through the air.

No, just the other way round. Of course it delivers thrust (as you need something to brake in order to prevent the plane from rolling), but it does not deliver power to the airplane. Instead all its power is lost to the air pressed through the propeller.

[D-Type]

That is the perfect explanation of what I wanted to make clear.



No, just the other way round. Of course it delivers thrust (as you need something to brake in order to prevent the plane from rolling), but it does not deliver power to the airplane. Instead all its power is lost to the air pressed through the propeller.

So, a jet engine and a piston engine and propellor both deliver thrust. In order to deliver that thrust, both the engines generate power.

My question remains the same "Is there a simple means of approximately comparing the two types of engine?"

Or put another way "How does the power generated by Thrust SSC compare with that generated by a top fuel dragster or a turbocharged race engine?"

[arttidesco]

So, a jet engine and a piston engine and propellor both deliver thrust. In order to deliver that thrust, both the engines generate power.

My question remains the same "Is there a simple means of approximately comparing the two types of engine?"

Or put another way "How does the power generated by Thrust SSC compare with that generated by a top fuel dragster or a turbocharged race engine?"

hp and thrust are different things see this link for an explanation.

Later in the thread someone says something about equating a 55 lbs thrust electric motor with a 3 to 5 hp petrol motor, taking 55 lbs thrust to be equal 5hp then the peak 50,000 lbs of thrust available to the Bloodhound SSC would work out at 45,454 hp required to propel 6.5 tones up to 1,000 mph plus

Edited by arttidesco, 08 January 2013 - 11:16.

[uechtel]

So, a jet engine and a piston engine and propellor both deliver thrust. In order to deliver that thrust, both the engines generate power.

Yes, a piston engine with propeller delivers thrust. A piston engine without propeller does not. So the amount of thrust is depending on the combination of engine and propeller. You can "spoil" the power of the engine by using a "bad" propeller. Therefore the hp value is usually given for the engine only, so without a propeller (it is measured directly from the drive shaft). Therefore you don´t know how much power a 100 hp engine has effectively on the airstream when you attach a propeller. You would have to know the efficiency factor of the whole layout and it would be different from the efficiency factor when not using a propeller, but driving the wheels of a vehicle by a shaft.

Also it is not guaranteed, that jet engine, which does deliver the same amount of thrust at zero speed as a specific piston engine combined with a specific propeller or installed ina specific vehicle will still be comparable to this specific layout at travelling speed (100 km/h, 200 km/h etc.)

My question remains the same "Is there a simple means of approximately comparing the two types of engine?"

My answer ist still "No". There is no simple means in my opinion, but only complicated ones. At least I did not find anything useful by searching the internet, which I think may be an indication.

Perhaps to make the problem more clear, your question is like "is there a simple means of approximately comparing the running speed of two animals from weighing their muscle masses". No, sometimes the heavier one is quicker, sometimes not. Of course it depends in some way on muscle strength, but there are also other factors.

[flatlander48]

Caption says it's a Datsun block. All the BMW blocks I worked on had no provision for a cam in the block.

Sorry. Who would think there would be a Datsun photo on a page of BMW photos? Weird. Anyway:

http://www.ebay.com/...k-/290840641041

Unfortunately we can only see the front end of the block, but it looks like the areas beside the main bearing cap are asymmetrical. You might be able to add an additional bolt on the right, but the left side would require removing a fair amount of material that presumably has some purpose.

Edited by flatlander48, 08 January 2013 - 15:39.

[Mistron]

Drag racing IS impressive, and everyone should indeed try it at least once.

Drag racing jet cars at night is a hoot! Do they still run a 'night of fire event' at Avon Park / Shakespear County raceway? It was may years ago and it was very impressive - the jet cars on run up literally brought tears to your eyes.

It was in Octoer and I seplt in my pal's beetle. I have never been colder in my life. I remember sitting in the stands wearing all the clothes I had with me, and my sleeping bag!

[Allen Brown]

Didn't somone once libellously claim that the Foyt V8 had a supply of nitro in a fake fire extinguisher. I'm sure that can't be true but a fun story.

I mixed up my stories. In April 1975, AP reported that Bignotti had accused Foyt of having a spare five gallons of fuel in his fire extinguisher. He also claimed that Foyt was using (illegal) nitro-methane in his fuel. The following month Foyt was reported by AP to be "steaming still" about the accusation and threatening to sue. Anyone know how that was resolved?

If this was true - and, in case there are any lawyers reading this, let me make it quite clear that I don't believe it for a moment - then I suspect the 1975-spec nitro-assisted Foyt V8 would be a contender for the most powerful engine used in four wheel competition

[flatlander48]

then I suspect the 1975-spec nitro-assisted Foyt V8 would be a contender for the most powerful engine used in four wheel competition

Well, if we're talking grenades...

[Lee Nicolle]

From the image I saw (link below), the webs looked relatively thin. The bolts for main bearing caps are not small and I think there wouldn't have been much material left after you tapped the hole. The front and back don't look to be a problem, but I think the middle 3 wouldn't be thick enough.

http://images.search...umb=c6syMjObpWU

That is an L series Datsun motor! I believe actually based on a Benz engine?

[flatlander48]

That is an L series Datsun motor! I believe actually based on a Benz engine?

Post #63...

[PS30-SB]

That is an L series Datsun motor! I believe actually based on a Benz engine?

It's a 1960s Nissan J16 block. OHV design with the cam in the block. If you want to link it to any other manufacturer, it would have to be Austin ( 1952 to 1959 Austin-Nissan partnership being the obvious reason ).

L-series Nissan was OHC design with cam in head, and NOT "based" on a Benz engine. Prince Motors licensed some Mercedes-Benz patented details for their G-series OHC engines of the early Sixties, and Prince was forcibly merged with Nissan in 1966, but Nissan's first L-series engine ( the L20 six of 1964/5 ) was already well into production before the Nissan-Prince merger. Nissan's L-series never used any Mercedes-Benz licensed designs or components.

[Henri Greuter]

I mixed up my stories. In April 1975, AP reported that Bignotti had accused Foyt of having a spare five gallons of fuel in his fire extinguisher. He also claimed that Foyt was using (illegal) nitro-methane in his fuel. The following month Foyt was reported by AP to be "steaming still" about the accusation and threatening to sue. Anyone know how that was resolved?

If this was true - and, in case there are any lawyers reading this, let me make it quite clear that I don't believe it for a moment - then I suspect the 1975-spec nitro-assisted Foyt V8 would be a contender for the most powerful engine used in four wheel competition

About the latest, I am not sure.
In '75 USAC had reduced the maximum turbo boost to 80 Inch, way below the levels that the Ford had achieved in the past and then came up with 1100 and more hp. Now there are the stories and rumors about the `special for Foyt`popoffs which supposedly gave some extra inches to him....
For sure that 100% nitro was out of the question, the highest levels of usable pop I have read was 30% and that was on atmo engines.
I dont know enough about how much notro could be used on a highboost turbocharged Indycar engine and the effects of nitro. On legal 80 Inch I've read that the Ford gave some 850 or so hp. Was it possible to go beyond 1200 hp with only using Nitro in the fuel?

Is there anybody reading this whe knows a bit about how much power increase coulc be obtained with different percentages Nitro?


Henri

Edited by Henri Greuter, 09 January 2013 - 10:25.

[arttidesco]

Speaking of extra inches of boost wasn't Mark Blundells wastegate welded shut when he set that stunning time of 3m 27.02 secs in 1990 I believe 1100hp was quoted to qualify the Nissan R90CK over six seconds ahead of the rest of the pack.