Just because a c/i engine is a slower engine than a s/i engine doesn't mean it should be ruled out of competitive use. There are various ways around the problems encountered with diesel engines. The fact that car manufacturers and engineers are even considering their uses within motorsport hints towards their future relevance. As mentioned previously, advancements in forced induction and modern lightweight materials are opening doors for c/i engines. Rule-makers in all aspects of motorsport should seriously consider revisions to regulations in order to promote c/i participation.
The story behind the Indy diesel is that in 1950 the governing body, the AAA, decided to encourage some new ideas by permitting diesels to run with engines of up to 402 cubic inches (6600cc) supercharged or not. The gasoline fuelled cars were restricted to 274 CI (4500 cc) unsupercharged or 185 CI (3000 cc) supercharged. This attracted the attention of the Cummins Engine Co. Cummins had a 6-cylinder truck diesel that could be enlarged to 401 CI by enlarging its bore. The crank and connecting rods remained original. Initially they put a Roots-type gear-driven supercharger on the engine and soon found that they had 340 bhp at 4000 RPM available. Kurtis was commissioned to build a special chassis for the engine. In 1950 Jimmy Jackson qualified on the last row at 129.2 MPH and dropped out on the 52nd lap with supercharger failure. Cummins were evidently not too disheartened and came back in 1952 using a turbocharged version of the engine - probably the first appearance of a turbo in car racing. The turbo used gave 20-psi boost at 4000 RPM resulting in 400 bhp. Kurtis produced a new chassis and despite the humble origins of the engine the car was one of the most beautiful ever to appear at Indy. In order to reduce frontal area as much as possible and to lower the C of G the engine was laid flat on its right side with the crankshaft to the left and the driveshaft running down the left side of the chassis. The driver sat low down to the right of the driveshaft. It was, however , a very heavy car at 2480lbs (dry) and consequently it was hard on tyres. Apparently the car also suffered from very bad turbo-lag and it took 3-5 seconds for the large turbine to speed up coming out of the turns. Nevertheless Freddie Agabashian took pole at 139.10 MPH. For the race it was decided to set the car up in a manner which minimised tyre wear even though this meant losing some lap speed. It was still hoped that the car compensate for this by running through the race without stopping. However the low turbo intake meant that it hoovered up rubber dust and debris from the track and became clogged after about 175 miles..
Thanks jgm thats very informative. I think it would be great to see governing bodies of today thinking in the same vein as those of the 50's. It would provide engineers with new interesting challenges. C/I engines are becoming increasingly popular in todays commercial market and i don't see why they shouldn't be encouraged in motor racing. Cars such as BMW's 535d have had rave reviews from the motoring press here in the UK, offering performance and economy (allbeit at a price). It proves it can be done. It would be great to see a race series such as the BTCC (a little variety please!!) encouraging C/I participation providing it is properly regulated.
I believe a team did run a diesel in the B.T.C.C. last year. I think they started the season with a Honda before moving their programme to a Peugeot. Ran around the 12th to 17th mark if i remember correctly.
"Whether you think you can or can't, either way you are right."
-Henry Ford-
Really? I assume then that the car ran naturally aspirated as forced induction is forbidden?
"Engine Regulations:
Race engines are based on a road-going production unit from the same manufacturer of which a minimum of 2,500 have been produced, although the base unit doesn't necessarily have to come from the same model as the bodyshell. Whilst the base unit may be between 1.8 and 2.2l, the race engine is limited to 2000cc, which may be achieved by re-boring or sleeving the block.
The engine block and cylinder head must be as per the base unit but may be lightened by machining or grinding off excess metal. Internal components are free and may be constructed from lighter material, subject to various weight limits. For example the crankshaft must not weigh less than 11kg. These restrictions are to restrict the use of custom built cylinder heads and expensive 'exotic' metals. Maximum permitted rev limit is 8500rpm.
Cylinder head values must be of the same diameter as the base unit with a maximum lift of 12mm. A TOCA specified single throttle body must be used, which includes a 60mm restrictor. Any form of variable valve timing, turbo-charging or forced induction is prohibited."
I read about a gas powered entry and a few teams spoke vaguely about it before the season began but i didn't think any actually ran? I could be wrong though!
All other things being equal, engine horsepower is what determines how fast a car goes down the track. Engine horsepower variables are speed, displacement and BMEP (Brake Mean Effective Pressure). Rules usually dictate engine displacement, so to increase horsepower, you must increase engine speed or BMEP.
Thus, for a given engine engine speed, a higher BMEP will produce a greater power output. All gas engines (spark ignited) are knock limited, thus the maximum BMEP rate that can be achieved is also limited.
Diesel engines (compression ignited) are only limited by the thermal and mechanical capacity of the engine. Essentially, that means the more air and fuel you cram into the engine, the more power you will make. At least until the cylinder head blows off or the piston crown melts.
I have seen diesel engines achieve BMEP rates of over 700 psi on regular no.2 diesel fuel. I have also seen spark ignited engines achieve BMEP rates exceeding 600 psi, but they required very specialized, knock resistant fuel (tolulene based).
Another thing to consider is fuel energy density. Diesel fuel has an LHV of about 18,400 Btu/lb and weighs about 6.7 lb/gal at ambient conditions. Gasoline has a LHV of about 16,200 Btu/lb and weighs about 6.2 lb/gal. So an equivalent volume of diesel fuel can produce more power than gasoline, at least theoretically.
I wonder if engineers would consider employing C/I engines in F1 if they weren't restricted to the materials they can use for the head, block, crank, pistons etc?
not sure if someone already answered this question (i didn't read the entire thread) but:
Q: Why do diesel engines create so much torque?
A: Diesel fuel is much slower burning than gasoline, so the engine has a longer stroke to accomodate for this. So the fuel burns all the way down the combustion stroke. Because of this long stroke the engine runs low RPMs.
There was a diesel in last years LaMas. If i remember correctly it was doing fine until it had a suspension problem of some kind.
Read in Race Tech that Peugeot and Audi are building diesel challengers for Le Mans! They will lap about twelve seconds off the pace but will require less fuel stops so they believe it will even out.
"Whether you think you can or can't, either way you are right."
-Henry Ford-
not sure if someone already answered this question (i didn't read the entire thread) but:
Q: Why do diesel engines create so much torque?
A: Diesel fuel is much slower burning than gasoline, so the engine has a longer stroke to accomodate for this. So the fuel burns all the way down the combustion stroke. Because of this long stroke the engine runs low RPMs.
They also run very high compression ratios. I think the VAG 1.9 TDI 130bhp runs a compression ratio of 19:1 which is double what most petrol engines use and even more compared to forced induction petrol engines.
Two or three years ago FIAT run a diesel Marea at the 1000 miles of Interlagos (São Paulo). It lasted the distance without problems, runnning in the middle of the pack. It is just to show manufactures are all considering the idea.
BrentK7 wrote:not sure if someone already answered this question (i didn't read the entire thread) but:
Q: Why do diesel engines create so much torque?
A: Diesel fuel is much slower burning than gasoline, so the engine has a longer stroke to accomodate for this. So the fuel burns all the way down the combustion stroke. Because of this long stroke the engine runs low RPMs.
There was a diesel in last years LaMas. If i remember correctly it was doing fine until it had a suspension problem of some kind.
It's little bits of information like this that make these threads such an interesting read. Obvious once it's pointed out - thanks
