I've thought of this before but never did much with it and put it off but figured might as well bring it up and see what you guys have to think about it.
With the way engines work they are more efficient when the throttle is held open more. When you open that throttle up it reduces pumping losses by making the restriction in the throttle body less. from my understanding that is at least in part why desiels and 4 wangers are more efficient.

this whole idea works air being more dense when cold and less dense when warm. What i was thinking of is running some sort of duct near the exhaust manifold to make an intake for the air which should make it less dense. in doing this you would have to open the throttle more to get the same mass of air. with the throttle opened more it should create less of a pumping loss in the motor. Sure how much power you make would be down but this isn't a making power idea rather I'm a tight wad mod .

this idea is at least how it works in my head. also have some questions though regarding this. wold the added cylinder filling create any advantages? ah I had others but I can't remember them right now. no biggie this should be enough to get the topic started.

 

That's not why they are more efficient at WOT, or why diesels are more efficient than spark ignition engines.

 

ok so I might be wrong you can at least help though sir

 

i believe some fieros had a setup similar to this, designed by smokey yunich(sp?) went un noticed but supposedly worked well

 

I guess I'm not seeing why you would want to do that. Yes, your motor MAY run more efficiently with less restriction in the throttle body. BUT you would be sacrificing cool incoming air resulting in a less dense air charge. Less dense air charge = worse combustion = less power.

Just my 2 cents.

 

why would less dense of a charge create worse combustion? I can easily understand it creating less power in WOT applications but no big deal on my end with that.
this is more for part throttle application.

 

GM has been doing this basic idea for years, from heat risers, to heated grids under carbs. While it did work for cold start up, there was never any real increase in MPG, if anything it was just the opposite as more throttle was required to maintain a given RPM. The increase you would recieve with the short time the engine is cold would not be enough to offset the engine running at operating temp. You would help the NOx from the tailpipe, i.e..EGR system, but otherwise no improvement would be seen.

 

Cool air is more dense, thus causes better combustion and resulting in more power. This is the principle behind ram-air, etc.

 

how does density lead to better combustion though.
my understanding with the ram air and colder is more for wide open throttle. the space to bring air is only so large and can only flow so much volume of air. if the air was more dense though it would have more mass for the same volume. so in this you would have more oxygen molecules to burn with gasoline. but since this isn't wide open throttle operation and we are not limited to the amount of air we bring in.
outside of that I haven't heard of dense air being more helpfull or creating better combustion at part throttle operation. if you could provide a little more detail on how this would help part throttle operation that would be nice.


@kwik84 that is kidn of what I'm wondering on if it would help or not. I know you would need to open the throttle more but with any decent EFI system should be able to adjust for that. this way when you open the throttle more it "sees" the air is less dense and therefor even though you have more open throttle your not squirting as much fuel into the motor so still able to keep a stoic mixture. but on this I could be wrong also. beend oing a lot of that anyway so yeah.

thanks for the input though guys.

just hope 57 can come back in and say a few words.

 

Engines are most efficient at WOT because of undisturbed flow. Pumping losses don't have anything to do with it.

Smokey Yunicks' engine was all about getting total vaporization and mixing of the fuel and air. He used a turbocharger to start the mixing process and keep the fuel/air moving in the right direction. He heated the turbo output to complete the fuel vaporization process. In effect it was a turbo engine that had an inter-heater, although he claimed the pressurizing effect came from the heat expansion of the fuel/air mixture, not the turbocharger. And, the engine had a throttle. The incoming air/fuel was so hot he had to use exhaust type valve materials for the intake valve. He spent most of the development time working out the cam profile. If memory serves, he got 255 HP and 35 MPG out of the 151 cid iron duke engine.

The change in density required to throttle an engine would require a huge temperature range. And, most likely you'd get heat expansion pressurization effects that Smokey used the turbo to counteract.

Diesel efficiency comes from the high compression. It's an Otto cycle thing.

 

Also, If the air is more dense, you're cramming more O2 into your combustion chamber. With more fuel in that tight space, you get a bigger kaboom.

 

brando to get more fuel and air all you would need to do is open the throttle more which would make you go faster and make it hard to keep to the speed limit. sadly I have had enough problems with the traffic laws in my past and I'm trying to keep that behind me now

five7 I know there is few different things with diesels though I admit I don't know a whole lot. just curious though doesn't deisel have a higher BTU then gasoline?
I figured (though granted it is more of an assumption and we all know that can cause problems) that the throttle blades create quite a restriction on the motor. partly why more throttle means go faster less throttle means go slower. in this case more throttle would be needed making it easier for the engine to breath but yet still creating the same power production.
with the heat though if I recall correctly that has been used on my honda to help with fuel atomization. the intake was bolted directly to the exhaust and they shared a very large mating surface and with that thing would get VERY hot. but that was also a wet flow setup so I'm not sure how well that would with my mazda with what I would guess could be best called a semi-direct port injection. the injectors there bolt directly to the intake port on the motor itself and shoot just about right into the engine.

With this engine design by yunick does it have any name I can look up. I'm curious now just because I don't have much of an idea of what kind of ideas he came up with for things other then he was quite different with many peoples thinking at that time.

 

Interesting thread.
I think it had more to do with atomization of the fuel in the air mixture.
Here's an example:
On carbed applications, the small runner/small plenum volume manifolds are more efficient at lower rpms because they keep the intake charge velocity up and promote atomization as opposed to the large plenum volume manifolds that allow the air/fuel charge to slow down and the fuel to drop out of suspension and puddle at part throttle.
I believe that the most efficient design would have 2 runners to each cylinder; like one tied to the smaller primaries of a Q-jet and a larger one connected to the back barrels.
At part throttle, back barrels would close off the bigger passages forcing the cylinder to draw it's charge from the smaller runners connected to the smaller venturis. This would keep the charge velocity high for maximum fuel atomization. When the bigger back barrels opened the large runner would feed max air flow to the cylinder for WOT. If you looked at the ports on the cross-ram manifold, you would see ports half the size of the intake port on the head. It really needs to be a 2 stage system.
The problem with performance fuel injection systems is they have to have large runners and plenums to make max power. The downside is poor fuel atomization at low speeds. Also on the TPI system the injectors are "batch-fired", all 4 on one side of an engine at once.
It is known that if the injector is fired during the intake cycle, the engine will be more efficient. On the batch fired system, some injectors will always be spraying at closed intake valves.
Something you could play around with, would be changing a TPI to be a Sequential Fuel Injection (SFI). It would probably improve effeciency.

 

Chemistry meets ThirdGen.org

 

What you describe there sounds like my old 24valve V6 SVT Contour. Short runners open all the time going to one set of intake valves, promoting good economy and lowend torque. Then at 3200rpm the second set of longer intake runners open up to the second intake valve, which has a different, longer duration cam profile, for big topend power. Worked pretty good, be interesting to see a carbed intake manifold application like that.

 

wouldn't it be the other way? long runners for low end power and shorter ones for higher rpm power?

 

http://www.stuff.to/svtbrochure/power.html

You are correct, I had it twisted round backwards.