2 stroke for drag racing cars?

Sir Yun · Post by **Sir Yun** » Mon Jul 31, 2006 8:25 am

weird thought

A smalll 2 stroke model engine can produce frightningly high revs and absurd amounts of power per cc (as in 2.5hp from 3.5cc).

so it kind of struck me why there are no 10 liter big blok nitro engines with 20000 hp.

emissions are not as issue

just a a thought

Larry Sockwell · Post by **Larry Sockwell** » Mon Jul 31, 2006 8:46 am

There were some diesel 2 cycle engines built by Cummins for a long time, maybe still are being built. I did some repair work on a Cummins stationary engine for a sawmill a decade ago. The owner was surprised that the engine no longer bogged when a large White Oak was loaded.

As for a gas burning 2 cycle fuel engine, can you imagine trying to get the tires planted with that torque curve? We already have enough power to break the tires loose at 300mph.

Larry

Ed-vancedEngines · Post by **Ed-vancedEngines** » Mon Jul 31, 2006 10:53 am

Are you possibly mistaken about Cummins 2 cycle engines?
All Cummins engines I have ever seen of any size or configuration were all of the 4 cycle variety.

On the other hand Detriot Diesel has mostly if not always built 2 cycle engines and they have always built them in all levels of sizes and performance. That is until a few years agao, when I forgot about keeping up with what they were doing any longer. They still may be. Dunno.

You can get Detroit 2 stroke/cycle Diesel engines with one cylinder up to 24 cylinders, and maybe larger, I am not sure. Thier sizes are named in the engine name and it has always been by how many cubic inches there is per cylinder. Examples are the 4-53 is 4 cylinders with 53 cubic inches per cylinder. A 6v-53 is 6 cylinders with a V configuration. They do go way on up there in sizes per cylinder and numbers of cylinders. One of the most common for many years was the old 6-71 (that is where the 6-71 supercharger we use in racing originated) The 6-71 Detroit was a workhorse in the trucking industry many years back and was affectionally called the 238 because it was rated at 238 horsepower. There was all configurations of the 71 series engines too. I.E. 4-71/6-71/6v-71/8v-71/12v-71/16-v71.24v-71. The largest you could get in a truck engine from Detroit was the 12v-71 and it was a powerhouse. IN later yers Detroit made some signifigant changes in that they went to a twin turbo and away from the roots style supercharger in the early 1970's The first engines they came out with using the twin turbo was called the Detroit 350 in an 8v-71 configuration which later got bigger. When I quit dealing with truck engines Detroit had changed everything to a 92 series engine so the engines all had 92 cubic inches per cylinder. Detroits were used heavily in agriculture and also in locomotive and tug boat engines in larger styles of the same design.

Cummins did make some industrial engines used mostly for irrigation pumps but as far as I know they have always been 4 strokes.

If I am wrong then I am wrong.

Now back to the 2 stroke principles. I would love to work with a 2 stroke engine of a size for a car to be used in drag racing. I think it would be very surprising to all.

Back in the 1960's we raced with 2 cycle/stroke engines in Karting and the power available from such phsically small power plants was incredible. After modifications for racing with porting in the block and heads and lots of carbs we routinely exceeded the 10,000 rom mark (that was as high as the tach would measure we used for testing) with enough power at the weight we had to burn the crap out of two per side 8 inch slicks in what was called the Super C class of competion. That was the biggest sized and the fastest. I loved Kart racing when we all had 2 cycle engines. They were either WestBend 820's times two or some of us had McColuch 75 's to 90's modified. They literally screemed to hear them. The sound was incredible and I can imagine that sound going down a drag strip in a car. Wow!

Ed

Ron E · Post by **Ron E** » Mon Jul 31, 2006 11:01 am

i believe Detroit has joined the 4 stroke crowd. I remember some old snub-nosed GMC trucks with those 2 stroke Desiels. THey sounded like they were runiing at least twice the RPM of the Cummins or Cats.

MadBill · Post by **MadBill** » Mon Jul 31, 2006 11:37 am

Here's an out-of-the box thought which dovetails with the previous nitrous topic: If you injected gasoline and nitrous direct into the cylinders, the engine wouldn't need valves or intake ports, just piston-controlled exhaust ports. It would thus be a two stroke....

mtkawboy · Post by **mtkawboy** » Mon Jul 31, 2006 12:16 pm

When I was 19 I worked at Ryder Truck Rental and got my first 6-71 Detroit Diesel lesson. I washed the air cleaner in solvent and just shook it out raher the blow it dry. I found out they will run at extremely high RPMs for a long time on solvent. I tore the shutoff right out of the dash so we got out of sight until it finally quit, sounding like 10 grand but Im sure it wasnt. Needless to say my boss wasnt to happy and I never did that again. Therse was a guy named Carl Heap that ran a 300 mph V16 4 turbo Detroit powered 42 International over the rod tractor at Bonneville. He has since passed away but it was a sight to watch. Pure black smoke with a clear spot at every shift. Had 747 front tires and a skid plate in case they blew out. His push truck was almost as stout as his race truck. He was from the Washington area, not sure exactly where. Each turbo was about 2 1/2 feet in diameter

PackardV8 · Post by **PackardV8** » Mon Jul 31, 2006 1:55 pm

Some things don't scale well - same reason an ant is many times stronger than a man, but there aren't any big ants. Strongest engines, ounce for ounce, are the nitro burning model airplane engines, but again, inertial forces, heat transfer and other physical laws keep them out of top fuel dragsters.

Post by **SchmidtMotorWorks** » Mon Jul 31, 2006 2:12 pm

Two-stroke motorcycles can be good for drag racing.
I used to race an RD400 (2cyl two stroke). I probably did 10,000 practice burnouts on that thing and it ran mid 11's, hundereds of trouble free passes. I think the only thing I ever did to maintain it was replace clutch parts.

Great fun for less than $2,000 for the bike, pipes and carb work.

The Kawasaki 500 and 750 triples could be faster but they were much more difficult to ride and maintain.

beth · Post by **beth** » Mon Jul 31, 2006 4:49 pm

I ported and modified 2 strokes for 6 years. The power per CC attainable drops quickly with cylinder size. The drop is unbelievable when you get above 250 CC per cylinder. A similar 250 cylinder will have approx 75% of the power of a 500 CC. Tremendous power can be made at 80CC per cylinder but at that size 427cid would be like 87 cylinders.

Darin Morgan · Post by **Darin Morgan** » Mon Jul 31, 2006 5:33 pm

Well,, here is the deal. When your parts have very little mass, the kinetic energies involved in turning an engine at 20000 or even 30000rpm are minimal at best. What stroke do these little things have. Its about an inch isn't it? look at the mean piston speed at 20000. 20000*1/6 = 3333fpm. That equates to a 350sbc turning about 5500rpm. Piston speed alone does not proportionally show the kinetic energies involved. Not even close. The power decreases at a magnitudinal scale of 2 to the order of size and weight decreases to the order of 4. What does this mean? Well an engine that is four times less massive than the original will only make about 50% less power. You can make a lot of power with small engines but when you start going the other way and get LARGE the weight starts to dwarf the power. The weight to power ratio is a funny thing. Within the scale we are used to working in these differences in power and magnitude are largely unnoticeable but when you look at some of the small scale engines that have been developed, it gets pretty amazing! How about a turbine engine the size of your thumb nail that turns 1.5million rpm and makes .3HP. Not only do they exist but they plan on making them one tenth that size in order to stack them and make small generator the size of a roll of dimes, runs on Hydrogen and will power a lap top for over a month!

Keith Morganstein · Post by **Keith Morganstein** » Mon Jul 31, 2006 5:57 pm

GMC. Jimmy AKA Detriot Deisel is the two stroke found in trucks and other similar sized engine applications. It's where the ever popular Blower comes from. 6-71 would be an engine model: 6 cylinders, 71 cu inch per cylinder and so on.

They made a lot of power for their displacement. The engine was really invented by Winton and became the EMD, the engine that put the steam locomotive out of business. The smaller detroits were off-shoots of the concept.

2 strokes for over the road use are pretty much done for reasons of emisions and economy.

The two stroke diesel is still used in very large engines i.e. up 120,000 hp to power giant container ships.

Like many things, what is effective in one application may not be for others.

The tiny turbine generators Darin speaks of are amazing. I read about them and it seemed like fantasy at first, but they are for real.

beth · Post by **beth** » Mon Jul 31, 2006 6:32 pm

The tiny turbines sound amazing, I wouldn't want to set up the clutch to get the car moving from 1.5 million rpm though.

sam · Post by **sam** » Mon Jul 31, 2006 6:33 pm

beth wrote: Tremendous power can be made at 80CC per cylinder but at that size 427cid would be like 87 cylinders.

Just imagine trying to press in all those crank pins and keep it all in line.....

From memory Honda did a V4 oval piston 4 stroke way back in the early 70's that revved to 26000, it was 500cc for the bike GP circus. I seem to remember it had 8 valves per cylinder, I'm sure there will be info on the net somewhere.

Commer (uk truck maker now long gone) did a TS3 (two stroke 3 cylinder) 3 cylinders and 6 pistons.

crank was central and the rods were mounted on rocker beams with the pistons horizontaly opposed in the same cylinder, it was supercharged with a roots type blower, very similar design to the old cabin blowers used in aircraft.

You could spot one of these things on the motorway (highway) after dark, they would decoke themselves every so often and you could see the carbon come out of the exhaust red hot, was just a shower of sparks. I suspect they may have been the cause of several fires

beth · Post by **beth** » Mon Jul 31, 2006 6:42 pm

"Just imagine trying to press in all those crank pins and keep it all in line..... "

Especially with over 2000 hp on the last pin.

Engineguy · Post by **Engineguy** » Mon Jul 31, 2006 7:55 pm

beth wrote:I ported and modified 2 strokes for 6 years. The power per CC attainable drops quickly with cylinder size. The drop is unbelievable when you get above 250 CC per cylinder. A similar 250 cylinder will have approx 75% of the power of a 500 CC. Tremendous power can be made at 80CC per cylinder but at that size 427cid would be like 87 cylinders.

The last two-stroke motorcycle I rode, 20 years ago, was a 4-cylinder 500cc Yamaha two-stroke sportbike my buddy smuggled in from Canada. At a smallish 125cc per cylinder (effectively two parallel twins with geared together cranks, not an inline four or V4), it verified your point... really nasty scarey acceleration... a bike as small and light as a 600 four-stroke with the power of a 1300(?)