Super V.E. for diesels

[oil pan 4]

The biggest problem with using super V.E. on diesels is the intake runners will need to be really long to keep the motor a harmonic range at cruise speed.

If you have 24 inch runners and start going up a hill and start pushing 20psi of boost the runners are going to effectivly become 28 inches long. Thats more useful.
If you could stretch them out to 32 inches, with a little boost they could become quite useful for towing/crusing. Use the 4th (+4%) harmonic range for cruise, put your foot down and bring it out of over drive and add more boost to get into the 3rd harmonic range (+7%), and when you drop it into 2nd or 3rd gear going over a mountian pass RPMs and PSI go up and bring you into the 2st harmonic range (+10%).

I am pretty much stuck with my OEM 24 inch runner intake. I dont think I could beat them for towing and power. I dont think I have enough room for the 32'' long runners needed to take advantage of harmonics at cruise RPM.
Maybe some of the 4cylinder guys do.

I like flow harmonics. I'm putting an expansion chamber exhaust on my chainsaw too.
Its kind of hobby.

Also water injection will slow down the pluses, but to what degree I do not know.

[baldlobo]

was diesel in the title the whole time? d'oh

pulled this from allpar

The high output 3.5-liter engines have a three plenum intake manifold design with short runner valves and a manifold tuning valve to regulate the air-flow needed, and a higher lift camshaft for increased air flow.

Fuel economy will improve as much as 10 percent on our new sedans using the new engines, due partly to the use of aluminum and computer simulations to optimize air flow. These engines have the potential to reduce hydrocarbon emissions by 30 percent. They will meet Tier 2 federal emission standards and California's Transitional Low Emission Vehicle (TLEV) standards in 1998. They also will meet California's stringent Low Emission Vehicle (LEV) standards by the year 2000.

[oil pan 4]

I changed the title.

[ecomodded]

I did some investigation into intake runners this morning,for my TDI they would need to be 3 feet long to have effect at the lowest rpm possible, around 4100 rpm.
The max rpm i drive is 2150, at my hwy speed & shift at 1500 to 1700 rpm.
Now i know why some hot rods have huge piped intake runners, I assume the headers/ exhausts work in conjunction.

[RiderofBikes]

when i hear this type of talk, encloding pipes needing to be certain lengths. First thing that comes to mind is a Transmission Line speaker project. for compactness and efficiency

[slowmover]

[IMG]http://image.moparmusclemagazine.com...-intake-us.jpg[/IMG]

1960 Chrysler 300F (and a few other models through 1961 or so)

Helmholtz resonator affect. Specific tuning. Mid-range passing times bested maybe by a Maybach or other ultra luxury gasser today.

[Daox]

Originally Posted by Diesel_Dave

The benefit is coming from two places.

First, increased vol eff decreases the pumping work. This is because as the piston moves down during the intake stroke it's being pushed down by the incoming air. The higher the air pressure during the intake stroke, the lower the pumping losses. Higher vol eff means higher in-cylinfer pressure during the intake stoke--even though the pressure in the intake manifold may be the same. The second source of the benefit is from the increased combustion efficiencies due to the higher AFR.

Is there really measurable gain there? Deisel engines optimize both of those thing better than most other engines already.

[Phantom]

Would we measure from the intake valve to the turbo?

Also is there any way to calculate the change in the harmonics in respect to length of the runner with an increase to boost?

[oil pan 4]

Originally Posted by Phantom

Would we measure from the intake valve to the turbo?

No, you would measure from the intake valve around most bends all the way back to the first and pronounced surface that the wave can bounce off from.
Some vehicles its the inside of the plenum, others like mine its another valve on a different cylinder.
I have a feeling a plenum would give the best wave return.

Originally Posted by Phantom

Also is there any way to calculate the change in the harmonics in respect to length of the runner with an increase to boost?

It would be easy to figure out, but the temperature is always changing under boost even if the pressure is not changing. Intercoolers start off working real well then get heat soaked and as you get up to speed they loose heat so its a cluster. One intercooled engine does not run the same temperature and boost as another.
Roughly every 10psi or at least for the first 10psi you add will cause the air pulses to slow down to the point where the air in the runners will behave as if the runners are about 10% longer.
I only worked this through 10-15psi because this was originialy for a gas application and I could only find post intercooler IAT numbers for the 10 to 15 psi range.

[Diesel_Dave]

Originally Posted by Daox

Is there really measurable gain there?

Yes, the gain is measureable (from both sources). I don't know as I've ever done it myself in a vehicle, but I've seen in many times on engines on dyno test stands.

Originally Posted by Daox

Deisel engines optimize both of those thing better than most other engines already.

Diesels typically aren't as optimized for reduced pumping losses (high VE) as you might think. In typical spark-ignited naturally aspirated gassers, high VE is pretty much the only way to get more torque at any given speed. So if you want to get more torque you pretty much have to increase the VE. On a diesel however, you can just add a little more fuel and/or a little more boost and you'll get the torque. Sure the FE will be sub-optimal, but it's just so much easier than redesigning heads and intakes.