A work of pure genius! - Brilliant "Revetec" Engine

[santostripoli]

Pneuamtic said:
Where an engine makes it's peak torque is dependant on how it is tuned. If it is tuned for high performance it makes it's torque high in the rev range. If it is tuned for reliability and drivability then it makes the torque much lower.

Response & Question
Brad said that his engine is tuned for an aircraft application, not automotive. He has tuned this engine to deliver torque low in teh rev range. This equates to good fuel economy.

Pneuamtic said:
The engine size and efficiency effects the torque. And as far as peak torque goes, the Hayabusa makes more.

Response & Question
Brad's engine has not been designed for peak torque, it is designed for economy. Therefore Revetec engine is more effecient becuase its torque is reached at an earlier RPM.


Pneuamtic said:
You see there is a negative to making torque low in the rev range, and that is that you need to select a taller gear to run at the same speed. And torque is effected by gear ratio's, therefore the issue gets confused.

Response & Question
How do diesel engines deal with thsi problem then? They have torque low in the rev range yet they manage to get away with it doent they. But they dont do it with an engine that weights less and is smaller in size.


Now, I am looking at this as a casual observer reading the facts and Pneumatic based on what you have said I cant really see your point?

Brad, what is your response on this?

Regards

Santos

[pneumatic]

I just thought I would copy this edit over from the previous page;

The Revetec announcement with the dyno curve in it (4 May 2006) compares a Revetec RHL4 with a Toyota Prius, which is not fair as the Prius is a very low performance high efficiency hybrid car. The Prius is 57kW and 115Nm from a 1.5L. Compare this to an Opal 1.4L engine which has 66kW and 125Nm. There is a big variation in conventional engines, so comparing the Revetec to them will be difficult.

Any comparisons need to be fair comparisons, they must both be tested to the same international standard. This will dictate what ancillarys are on the engine at the time (if you have no alternator or water pump on one engine, it will make more power because no power will be lost to those ancillaries). I don't know if the Revetec has a water pump or alternator on it at the time of the test. I am sure Brad will let us know

[revetec]

You are right.

We design engines to suit a certain application which is automotive which usually has a rev range up to 6,000rpm.
Trucks are heavier and have engines that have a lower RPM range (Diesel) so they run closer ratio gears and in the larger types of trucks, more gears.

Have you noticed a trend in automotive transmissions that we are seeing more and more gear ratios? Some automotive companies are now supplying 6 and 7 speed transmissions to lower the operating rev ranges to save fuel.

So having such a wide rev range is not so important anymore.

Our production model will see further gains. We are shooting at a launch engine with around 30% increase in power and torque compared with comparable featured engines. We can then look at variable valve timing and intakes etc to better address the performance markets. Also note that no development was done on breathing at the stage those figures were produced. Power in the top end rev range will increase in our next engine.

[pneumatic]

Originally Posted by santostripoli

How do diesel engines deal with thsi problem then? They have torque low in the rev range yet they manage to get away with it doent they. But they dont do it with an engine that weights less and is smaller in size.

Most of what you said proves my point. You can't compare chalk and cheese.

The Revetec test engine did not look set-up for aircraft use at all. I am pretty sure it was aimed at the automotive market.

I will explain the diesel analogy later. It will take some diagrams I think

[pneumatic]

Originally Posted by revetec

Have you noticed a trend in automotive transmissions that we are seeing more and more gear ratios? Some automotive companies are now supplying 6 and 7 speed transmissions to lower the operating rev ranges to save fuel.

I think that is also marketing driven, people like to say they have a "6-speed" for wank value.

[revetec]

Originally Posted by pneumatic

I think that is also marketing driven, people like to say they have a "6-speed" for wank value.

Look...I have joined this forum so I can let you all know some information that was misinterpreted on this thread. I supose there are people who think we are innovative and the results show we are getting there. Some people will always be argumentative and suffer from tall poppie sindrome. Just accept that our project has merits, our new design is good and compact, we have a major automotive company interested which is impossible to do if you can't prove there will be gains in fuel efficiency.

We are working hard to complete our pre-production prototype and we look forward to showing it off to the world when completed.

We can chat for years about engines. Our technology has nothing to do with an engines top end or breathing. If you ever get the opportunity to actually turn one of our engines by hand you will feel the efficient transfer/torque lever and be totally sold, like everyone that has done it.

Cheers :-)

BTW. JP8, CNG and Diesel versions are coming.

[manolis]

Pneumatic,

The current Wankel Mazda motor – the most advanced rotary engine ever – needs oil inside the combustion chamber otherwise the ‘rings’ of the rotor/piston fail. This oil is lost at the exhaust. Mazda recommends one check of the oil every two fill up of the fuel tank. And there is an alarm light for low level of lubricating oil.
So the Wankel rotary engine does has two stroke lubrication.



Brad,

The control of the Pattakon Flying machine is already mentioned and it doesn’t need any complication like pitching the rotors. The body of the rider/pilot is more than adequate, just like a rider drives his bike.
As for safety: that is why the moving parts (say cylinder heads, camshafts, timing belts etc etc) have been eliminated in Junkers-PRE engine.
In any case a light safety parachute is always an option.
An engine to your back and a parachute cannot go fast, cannot go long, and you are always at the merci of any gust of wind.



Santostripoli,

Both the torque and the power are important quantities.
Think simply:
As long as you drive into the town traffic, what you really need is torque at low revs. This makes you life easier and less costly.
But when you want to accelerate fast, what you need is plenty of torque at high revs i.e. you need as much power as possible (power is nothing but the torque en engine provides times the revs).
So the good engine is the one having plenty of torque at a wide band of revs, i.e. plenty of torque at low, medium and high revs. If it has good behavior at partial loads too, so much the better.



Brand,

You made already a few essential mistakes in your previous replies. Read your replies once more and you will see you learned a few things through the present discussion. Therefore don’t blame Pneumatic for ‘tall poppie syndrome’.
The hope is that tomorrow we will have more ‘Pneumatics’ to give us tips and judgments and ‘a fresh view point’, for free.

Thanks
Manolis Pattakos

[pneumatic]

Originally Posted by revetec

Pneumatic: How about comparing our engine to the current Mazda 1.4litre. And please note that we are improving with every modification. Currently we are 20% better in peak power and torque up to 4,500rpm than Mazda's production engine.

Brad,

I am hoping you have made an honest mistake, or I am reading something wrong, because this a something quite fundamental.

It's just that the image you have posted above looks a lot like what you get if you get a Mazda 2 CHASSIS dyno curve, a lot like this one;


And then take the Revetec RHL4 ENGINE dyno curve (from Revetec website);


and put the two together.

This would be a silly thing to do, because as you know you cannot compare engine power (measured with an engine dyno) with wheel power (measured with a chassis dyno), because wheel power is the engine power less the transmission losses.

Now most dyno operators will work on a number somewhere around 17% for the transmission losses. So that number is basically the same as the 20% gain you are claiming for the Revetec.

You are not comparing apples to apples. If you put your engine in a vehicle, and got a chassis dyno reading, it would be close to that of the Mazda 2.

I am being totally realistic in this thread. I am being pessimistic because if I came on here and was an optimistic we'd all just be saying how great things will be. I am attempting to be some sort of reality check.

I am keeping an open mind, I do like the X4, but there still isn't any good test data to discuss at this stage. When you provide some positive test results, I will be the first to congratulate you.

Manolis,

Ok, I thought you meant the rotary uses a pre-mix with the fuel like a 2-stroke. The consumption of engine oil is very minimal. A normal 4-stroke consumes engine oil too, it is needed to stay in the cylinder wall to lubricate the piston skirt and rings. It also lubricates the valve guides.

Santostripoli,

A diesel is not used because it makes good torque at low rpm, it is used because the diesel is a naturally efficient engine (mostly due to the very high compression ratio it runs). The low rpm is a side effect of the bulky engine design required to handle the high compression, and the time needed to properly combust the injected diesel. European car manufacturers are working out how to use new injection technologies and develop relatively high revving diesels, combining the good efficiency of the diesel with the ability to produce good torque over a very big rpm range (like a petrol engine).

There is an article on the web I will try to find, that discussing power and torque in detail. It asks if you'd rather an engine that makes 100Nm at 2000rpm or 100Nm at 4000rpm (or similar). Basically the 100Nm at 4000rpm is much better as it is twice the power. The second engine can run gearing twice as low to achieve the same speeds, and this means it will actually have twice as much torque at the wheels at a given speed.

Making torque at low rpm isn't the (only) key to good fuel economy.

[revetec]

Dear Pneumatic: That was an honest mistake...Sorry!

You stated 17% losses but that's for a rear wheel drive car. In a front wheel drive car, the losses are more like 12-15%.

On our next engine we will get a further 10% initially and after testing and mods we expect up to 20% gain. Car manufacturers are happy with a 5-10% increase so it is all good.

Pneumatic: Sorry again....I don't really have enough time to read the whole websites I visit....but I should. I wont post so often so I can verify everything I post from now on. :-)

[revetec]

It's also hard to get comparison figures as most engine tests are performed in vehicles. Most Chasis Dyno manufacturers and operators factor in 20% drivetrain losses which overstates engine flywheel power and torque. Many major automotive manufacturers have been caught out doing this and overstating engine power. There are new standards world wide coming into effect soon which should help to address this issue.

Every car has different drivetrain losses so to properly check the losses, the engine must be removed and tested on an engine dyno then installed into the vehicle and compare those figures. Not many people remove a standard engine to perform a dyno test so it is hard to get acurate data to compare.

As well as this the two engines must have exactly the same test conditions so should really be performed at the same facility at the same ambient temperature, humidity, fuel quality, fuel temperature etc.

Usually all this information is not released with dyno graphs so how can it all be compared acurately.

Might I also state that when those graphs were produced that the lambda was set at a static 14.7:1. We didn't have time to enrichen and fully program the injection and timing because the engine was packed up and sent OS. I'm looking forward to getting that engine back so I can play with it a bit more.

[pneumatic]

Originally Posted by revetec

Dear Pneumatic: That was an honest mistake...Sorry!

You stated 17% losses but that's for a rear wheel drive car. In a front wheel drive car, the losses are more like 12-15%.

Ok. I won't debate the transmission loss issue, as that is a whole different discussion that is regularly argued You only know if you do a dyno run on an engine, put it in a car and then redo the dyno run. This is rarely performed.

The problem you will have is finding an actual engine dyno curve for a 1.4L engine. Again, you need to be running the same ancillaries for the comparison to be fair.

There is certainly nothing wrong with the current torque figure of the Revetec, but I also don't see it as out of the ordinary either (yet).

I do find it a little strange that the test engine is apparently having trouble breathing at the higher rpm, considering it is using the cylinder heads and intake manifold from a 2L subaru motor that flows enough air to make over 160kW in turbo form, and 112kW @ 6800 in naturally aspirated form.

[pneumatic]

lol, we did the last posts at the same time as each other. It's good to see we said the same thing about dynos and the difficulty of finding good data.

I've heard a lot of the manufacturers are understating power now, to be on the safe side and ensure the customer gets what they expect. But who knows what is really going on...

[revetec]

lol...we are thinking alike on some topics.
Back to the torque discussion:
If Engine A produces 200 pounds-feet of torque at 2,000 RPM, and Engine B produces 200 pounds-feet of torque at 5,000 RPM, Engine A will have more towing or hauling capability at lower speeds, because it reaches its maximum torque at the lower RPM. Engine B will have more towing or hauling capability at higher speeds, because it reaches its maximum torque at the higher RPM.
But the higher the RPM, the more fuel is consumed. Generally torque is important from an acceleration off the mark point of view. The heavier the vehicle or load, the more benificial higher torque at low RPMs.

If you look at the top end of scenarios like F1, you have to rev the engine at 15,000-18,000rpm to get the vehicle off the mark and not bog down or stall. In the lower end, a truck can accelerated well from just above idle. Higher torque at lower RPM's on the same capacity engines saves fuel. What is preferable is holding that high torque over a wide RPM range to give good performance right through the desired rev range. But most engines that have high torque at lower rpms usually have poor torque or are unable to operate at high RPMs such as a large truck engine. As a result many large truck engine have far more gear ratios in the transmission to deal with the narrow torque band.

[revetec]

Hey! Even though I made a mistake with the graph, I didn't delete the post...where the hell did that disappear to?

So let's look at what type of driving that torque is all important.
My view from driving my car is Towing, Accelerating from a cruise situation and/or driving at a constant speed and then going up a hill. (higher torque mostly results in not having to select a lower gear)

Both situations are around 2,000-2,500rpm.

Anyone have any other thoughts on this?

[pneumatic]

Ok, to explain the whole torque and horsepower thing will take quite a while, and a lot of examples and graphs to prove. Unfortunately I don't have time to do this just yet. So until then here is some light reading for those interested. It is a good discussion on the subject;

http://vettenet.org/torquehp.html

There are countless other discussions out there.

A good engine has a big area under the torque-rpm curve. You need lots of torque, and you need to be able to maintain that over the rpm range of each gear. The higher the rpm you can maintain that torque, the better (as it gives more power).

The engine that makes good torque down low will be fine for towing. But try to overtake and you will find you can't rev the engine, so need to change up a gear. This drops the torque at the wheels and you will accelerate slower in the next gear. An engine with good torque at high rpm will be able to keep revving out in that gear, not needing to change up a gear, and therefore being much faster.

The thing you need to remember is that just because an engine can make good torque at high rpm, doesn't mean it doesn't make good torque at low rpm. However an engine that makes good torque at low rpm doesn't make good torque at high rpm.

Just because you have an engine that makes torque at low rpm, doesn't mean it will be more fuel efficient at low rpm than an engine that makes it's peak torque at high rpm. The engine with the torque at high rpm may have good fuel economy down low, and up high. However an engine with torque at low rpm cannot have good economy at high rpm.

Confusing?

One engine may be as efficient at 3,000rpm as another engine is at 2,000rpm. This gives the 3,000rpm engine the advantage as it can be geared lower. You see in order to get good efficiency from the vehicle, you'd gear it so you cruise at the most efficient rpm. One car would cruise at 3,000rpm, the other at 2,000rpm. Both getting the same efficiency.

But the engine that can cruise efficiently at 3,000rpm would be better. If both engines made say 100Nm of torque at their cruising rpm, the 3,000rpm engine would actually have 150% more torque at the wheels than the 2,000rpm engine (as it would be geared 150% lower).

If you weren't confused before you probably are now