modified merlin heads

[ukmerlin]

Re: modified merlin heads

Sure , if you got the bucks then anything can be designed and made BUT who accepts the liability when it all goes tits up . For most UL racers one cocky race engine is a luxury , it goes kaboom and we go home with zero. To say that for reno racers money is not a problem is just untrue, Its bloody expensive and huge effort . Also some of the manufacturing codes will reference FA or FV . Meteor parts (i.e rods) or stamped FV for fighting vehicle. They cannot go in an engine for an aircraft .
Cheers ......up the hammers

[Sparrow]

Re: modified merlin heads






Here are a pair of cylinder heads to look at. The bare one is a 600/700 series Rolls Royce transport head. The crusty one, which is the closet aircraft head to the one being modified is a Packard –7 head as used in the Mustang. One of the differences is the fact the aircraft head only has 14 coolant transfer spool bores while the tank head has tandem bores. The tank head and the aircraft head are not interchangeable for this reason alone. There are some other differences between the two heads.

[Sparrow]

Re: modified merlin heads







Here in this pic is 2 different kinds of liners. The round topped one is for the Packard head while the one with the flange is for Rolls banks.

The other pic is of a couple of rods. The LH one with the piston hangin onto it is a Packard rod that came out of an engine quite a few years ago that detonated at take off power and then cut the case in two.

The other one is an Allison rod the detonated at 120” when the ADI shut off. You see the obvious difference, the Packard rod broke. The Allison rod get the $hit kicked out of it but didn’t separate. So much for Allison rods.......

[Sparrow]

Re: modified merlin heads




In this pic is a stock Merlin as used in the Mustang. There are a great many differences between these engines and the Meteor’s, although the first Meteor was built using an aircraft Merlin crankcase. The Meteor, like the Merlin is all aluminum castings. Meteor’s are also being modified for use in boats, both pleasure boats and some of the Hydro’s are using Meteor’s that are modified with 2 stage engine parts.

[morerevsm3]

Re: modified merlin heads

I think this should be looked at in seperate pieces, the port modifications, combined with new plenum will make a big difference on this engine, and totally eliminate the need for backfire screens, as reversion is no longer present, however, you could not possibly fit the same plenum to a Mustang, there simply is not room under the cowl, so then the question is how much extra power would it need to make to offset extra drag if a bulge was put on the cowl?
the second question about new pro chargers Vs mustang superchargers is something that is definitely worth investigating

http://www.youtube.com/watch?v=hPVJUCAjAT8

the 3rd question is the motec used on the tractor, this one is a no brainer, it is massively superior in every way to the old ignition/carby setup, and would have no packaging issues, each individual cylinder can have fuel adjusted by reading EGTs, you can add extra timing after torque peak to maintain maximum cylinder pressure for more rpm range, timing can be altered for inlet, and exhaust plugs seperately in 500rpm increments (not fixed advance curve)
4th questin is connecting rods, seems like Allison rods are very rare and expensive, would be worth talking to carillo or pauter and see what they could offer

double overhead cam conversion would not offer enough benifits for the cost and complexity in a Mustang, and still have the cowl limitations as well
just my 2c on it all

[Sparrow]

Re: modified merlin heads

We all must realize that we are basically comparing apples to oranges. The Meteor engine is a naturally aspirated 600 HP engine that has a completely different intake manifold, carburetor and accessory drive (wheelcase) set-up than the aircraft engine. Also, in it’s original configuration, the Meteor runs the opposite direction of the aircraft engine. I found it interesting they were using Packard –9 cams on it for awhile so I assume it was running in the opposite direction (LH crank rotation) than the Meteor did originally (RH crank rotation).

Here’s some aircraft engine numbers, Packard V1650-9 is 1930 HP wet at 3000 RPM & 80”. The G6 Allison, 143/145 engines as used in the P-82’s were rated @ 3200 RPM & 100” wet which produced 2250 HP. These numbers can be bumped around somewhat depending upon altitude, but these are basic operating HP numbers for these engines as produced by the manufacturers. It is figured that on a Merlin race engine with a tube, rather than aftercooler, using –7 (5.8 final drive) blower drive gears that at 3500 & 110” is roughly 3100 HP. Using the –9 (6.3 final drive) gears it is figured that at 3450 and 130” is roughly 3800 to 3900 HP. With the higher ratio blower gears the supercharger requires twice as much power to drive it. Point being, that with the low gears it’s all done about 110” maybe 115” at the most, WFO. With the higher ratio gears, they start really coming on at 120”. I have seen a Merlin produce 150” MAP, but the reality of it is anything much past 3600 and 135” is just making noise, the inside dia. of the valve seats becomes a factor that begins to limit how much volume can be introduced and removed from the cylinders. This is why I found the statement of getting 5000 HP at 90” interesting.

The Procharger is a nice part, however there would be only enough room on the back of a Merlin in a Mustang to get 1 of those in there, without moving a bunch of other stuff around-like the oil tank, for starters. It is gear driven so it is still consuming HP. Probably not as much as a Merlin blower, they consume over 1000 HP at race boost using the higher ratio blower drive gears. They showed 56K rotor RPM and 48 PSI, how much HP is required for that blower to produce that? Unlike your Meteor tractor engine, these engine’s run at a constant speed. Manifold pressure is controlled by throttle position, not entirely by RPM.

An interesting fact is that Allison’s don’t use backfire screens, but the 2 stage (G6) Allison’s when used in the boats, had to have the ADI set up perfectly or the engine would sneeze and blow the blower off the engine-- literally off the engine. That being said, I would assume the ADI system to be equally as critical and twitchy for the aircraft. With the screens in the Merlin, they are somewhat more forgiving. Allison was playing with ways to install backfire screens in their intake system but it wasn’t put into production. Rolls Royce specifically state’s that the backfire screens will be in place at all times. Rolls was experimenting with both fuel injection and turbo-charging but ultimately decided to go with the pressure injection carburetors and putting the fuel into the eye of the blower which is how they all are. This was found to be most efficient for what they trying to accomplish.

I have had different people look at building G6 rods, it could be done, comparatively speaking probably not expensively for the finished rods themselves. The bulk of the cost was in the tooling. There was (is) simply not enough of a market to warrant producing them and there are still NOS and good serviceable rods available.

The packaging could become an issue with the EGT’s in the airplane as there are stack shields between the head and the stack, and then covering the stacks. Six individual short exhaust stacks that were extensively designed to produce thrust. Placing the EGT probes could be done, however running all the wiring out of the shrouds, through the engine compartment and to the cockpit would expose the wiring that is controlling fuel mixture/timing etc. to a lot of situations that could damage it. Between race maintenance being one. The covers and cams are removed to torque cylinder banks, re-adjust the valves and etc. There can be a lot of things taken apart in the engine compartment between races. It would be best if the EGT probes (as an example) could be disconnected and the control wiring moved out of harms way. What's the feasibility of doing that several times at the race track? How are the connections done? Would there be a program in the computer for testing system integrity after each maintenance cycle to insure something hadn’t gotten damaged while it was being taken apart and put back together? Is there any system redundancy in the event system initially checks good but then there is a failure of a component during operation? Custom made camshafts have been made and stock ones reworked so there are several flavors of them to choose from.

Sparrow

[morerevsm3]

Re: modified merlin heads

as far as EGTs go, you only need that for initial tuning, once done, they can be removed

[Sparrow]

Re: modified merlin heads

I wouldn't think you would want to remove the EGT probes if your using them for control. Is there an automatic mixture control for altitude compension or a way to compensate for density altitude. Reno is 5000' and sometimes on really hot days the density altitude can be 8500' or more. Does the computer automatically adjust for this after the initial setup?

[morerevsm3]

Re: modified merlin heads

egt probes would only be used to setup differences in fuel requirements per cylinder, MAP sensor compensates overall tune for altitude density changes, you may run an egt sensor on one cylinder for data logging while racing and/or add fuel if temp reaches XXX* or whatever you like, but differences between individual cylinders should be a constant

[ignomini]

Re: modified merlin heads

What a great thread. Keep it going.

In case anyone needs a bathroom break, I thought I would throw in a practical application of some of the ideas under discussion. The motor in my 1962 Triumph TR4 consists of a welded up original engine block (show me an old TR and I'll show you a cracked engine block) and pretty much everything else is brand new - including the aluminum cylinder head. Stock heads are iron.

It would be entirely possible to assemble this engine with original bits, but modern materials allow us to make stronger parts which are better able to withstand more than stock power levels.

So with all the fancy bits inside, why did we use an SU carburetor? Simple, carburetion covers all sins. While it's entirely possible to achieve better results with EFI, the cost of tuning the system is prohibitive, even in relation to all the money in parts and assembly. The SU slobbers enough fuel to keep the engine alive. Because EFI systems are so precise, they must be tuned for every scenario (temperature/load/altitude, etc.).

Why spend the extra dough when we know a stock engine can take 6psi with no problem? Because I wanted to run eight. Just like the Merlin guys, I'm looking for about double the stock horsepower in a reliable package.

Now back to your regularly scheduled program...

[Sparrow]

Re: modified merlin heads

We have kicked around, quite alot actually, fuel injecting a Merlin and even going to alcohol. That would solve a lot of issues with a few things in air racing. However, myself, like Knight engine's cannot even begin to afford an R&D program for something of this nature. It would be a great thing to do, some of the things shown on this thread by the folks in Oz are very intriguing. It can all be done. As has been mentioned before, money invested versus prize money returned (if it don't break) isn't even really worth discussing. Tough enough to keep it going from year to year without opening another cavern to throw money into. As far as making parts for aircraft engine's, that's a whole different can of worms.

Sparrow

[IcePaq]

Re: modified merlin heads

[morerevsm3]

Re: modified merlin heads

We have kicked around, quite alot actually, fuel injecting a Merlin and even going to alcohol. That would solve a lot of issues with a few things in air racing. However, myself, like Knight engine's cannot even begin to afford an R&D program for something of this nature. It would be a great thing to do, some of the things shown on this thread by the folks in Oz are very intriguing. It can all be done. As has been mentioned before, money invested versus prize money returned (if it don't break) isn't even really worth discussing. Tough enough to keep it going from year to year without opening another cavern to throw money into. As far as making parts for aircraft engine's, that's a whole different can of worms.

Sparrow

I race cars, circuit, hillclimb and speedway, there is no prize money at all for circuit, but you pay entry fees, for winning my class at national hillclimb championships, I won $100...but entry fee was $250 and speedway there is a small amount of prizemoney, no where near enough to cover costs. in the scheme of things, going to methanol and motec on a merlin would be not rediculously expensive, and motec themselves were heavily involved in sorting the meteor in this tractor, so should have the data on what parts etc to use, and Joe would also provide detailed information, and, tuning in a plane should be easier than ground based vehicles, as you can do full power runs like on a dyno without actually needing a dyno, maybe run some different exhaust stacks that are longer and merged so you can run a lambda sensor and egt sensors for the ground based tuning, you could have a webcam looking at a laptop screen, and a tuner anywhere in the world can see the screen and give instructions and what parameters to adjust, and how to do it.
the world is getting smaller all the time...

[MRE]

Re: modified merlin heads

Maybe you could make it pay for view.

[morerevsm3]

Re: modified merlin heads

Maybe you could make it pay for view.

next years world origami championships are going to be paper view...

seriously though, if something like the red bull air races are not self funding, what hope have mere mortals got of breaking even with our expensive hobbies?