Turbo and improved economy

[George Tyler]

changing the valve overlap is just tuning it for lower RPM, I think it is a good idea. you can also delay exchast valve opening to get a bit more power out before in opens, same reasoning.
How about removing 2 pistons, and disabling the valves on those cylinders in some way then adding a turbo, that will decrease your consumption. you will need a small turbo to work efficiently at the low flow rates. a turbo can actually do more than reduce pumping loss, it can develop pressure in the cylinder on the induction stroke which pushes the piston down, the energy is energy recovered from the exhaust.

[fatman57]

havent looks at this post in a while - must say thank you to Allch Chcar for his really great input!

Taking out 2 pistons is a good idea, how about replacing them with 2 smaller pistons, with fuel injection you can choose which to use so use the smaller ones for lower fuel consumption at idle to keep the engine turning then switch to the bigger ones for moving?

Anyone seen the new skoda? Around 1.0 litre engine but supercharged!.......gets 50mpg combined with a normal driver!!!!!

[Arragonis]

Originally Posted by fatman57

Anyone seen the new skoda? Around 1.0 litre engine but supercharged!.......gets 50mpg combined with a normal driver!!!!!

No, please tell me more ?

[EdKiefer]

Adding a turbo to a NA engine can increase its mpg, but that depends on the fuel metering system you use as to how much you'll see .
Even at idle speeds the turbo is spinning at like 20k rpm providing turbulence and the back pressure is nill on turbo at low speeds cause you can free the exhaust from turbo back (you don't need much of muffler) .
I have added turbos to few cars and it can improve overall but that also depends on how you drive of course .
You will see improvements if the vehicle has a carb or throttlebody injection with turbo downstream as the intake impeller breaks up the fuel droplets .
On modern port injection it would probably depend on how emission/fuel injection system is tuned by OEM .
If turbo is sized right even part throttle gets boost without being in boost conditions .

PS: Also you don't want to bias use/need a wastegate with turbo setup .If you try to setup turbo size so boost spikes high and needs wastegate early on then you probably will not get much improvement in mpg .
When I added turbo on my Opel 1.9 I first had it setup so card size limited boost (this is done with larger exhaust A/R housing (0.40) . Then I later went to 0.25 housing and a wastegate and while boost response was better at lower end it did eat a little mpg so how you set things up and size things has a big factor on how it affects driveability and mpg .

[George Tyler]

I was thinking that a lot of the gain would come from reduced friction by removing 2 pistons.....you also reduce pumping loss and a bigger cylinder is more efficient due to a better surface area/volume ratio in the combustion chanber. As you increase cylinder capacity area increases with the square of dimentions, and volume with the cube. heat conducted away from the hot gases is proportional to area.
this heat loss is one of the factors that limits low RPM efficiency.