Grill block affected milleage

[MazdaMatt]

Does this meant hat a turbo adds a HUGE advantage in FE to a deisel? 14psi means double the o2 in the air (not quite, due to compression heating, i suppose, but close).

[lunarhighway]

A turbo will needs additional cooling wich will cause additional drag, But a well set up turbo could delever superior FE. there is a curent trent among carmakers to make small turbochared engines to replace powerful big blocks, as these engines have the same power but much better FE and despite the addition of the turbo often weight less, than a big block.

Fiat is working on a turbocharged 2cylinder wich could deliver over 100Hp

[MazdaMatt]

makes sense... you idle like a 70hp p.o.s. and you WOT like a 140hp sport compact.

Could you have a reasonably quiet 2cyl >100hp? That seems like quite a feat.

[lunarhighway]

just found the picture again with some details

hp ratings don't really tell much (how often do you drive a car near the redline?)
so it's where it gots the most torque will matter.

Could you have a reasonably quiet 2cyl >100hp? That seems like quite a feat.

probably not, but most engines will be rather noisy at the top of their revv range. they intend to use this engines in their small car's wich won't need to much power to purr around town, but it should still give them more then enough power to deal with todays traffic.

doesn't look like something that was designed with the mechanic in mind though

[NeilBlanchard]

Hi,

A 900cc twin would be a good engine -- if it has a long-ish stroke, it could be quite "torquey". The old "airhead" BMW engine worked very nicely in the 800-900cc displacment, and the torque output was very good. With variable valve timing and a (mild?) turbo, it could be pretty sweet. You also get less internal friction, etc.

[instarx]

Originally Posted by MazdaMatt

Does this meant hat a turbo adds a HUGE advantage in FE to a deisel? 14psi means double the o2 in the air (not quite, due to compression heating, i suppose, but close).

Yes and no. I oversimplified when I said that the limiting factor was how much O2 you could stuff into the cylinders. Of course once all the fuel is burned you can't get more power no matter how much O2 you have.

Turbos on diesels do improve fuel economy. Here's why:

We've all seen old diesels pouring black smoke from their exhausts. That smoke is unburned fuel because a non-turbocharged diesel simply can't get enough O2 when it is under load. Turbocharging the exact same engine will supply enough O2 to completely burn the fuel, improving FE. However, a diesel not under heavy load will not have its FE improved by a turbo.

Turbos on diesels work differently than on gas engines. Diesel turbos only supply compressed air to the cylinders, while gas turbos supply a compressed air/fuel mixture to the cylinders. That's why diesel turbos can increase FE while gas turbos almost always decrease FE. Gas-engine turbos always put more fuel into the cylinders under boost, while diesel turbos do not (but they allow more fuel to burn more efficiently under load).

I'm not convinced by the claims of automakers of new turbocharged gas engines that increase FE. I suspect the increased FE comes from use of a smaller engine rather than from the turbos per se.

AH! as I was writing this I see that lunarhighway posted something that supports this thinking... a 0.9L turbo engine replacing a 1.2L NA engine.

[NeilBlanchard]

Hmmm,

With direct fuel injection, then a turbo on a gasoline engine just compresses air.

Do turbo diesels use ever use an intercooler? (If the main purpose of increasing compression on a diesel is to heat things up...)

On a turbo gasoline engine, an intercooler can improve power (and probably boost FE) by increasing compression but avoiding pre-detonation because the heating (from compression) is reduced?

[instarx]

Originally Posted by NeilBlanchard

Hmmm, With direct fuel injection, then a turbo on a gasoline engine just compresses air.

Interesting observation. That's probably correct.

Originally Posted by NeilBlanchard

Do turbo diesels use ever use an intercooler? (If the main purpose of increasing compression on a diesel is to heat things up...)

Absolutely. Intercoolers are frequently used downstream of diesel turbos and increase power significantly (even more O2 can be stuffed into the cylinders). Pre-detonatoin is not an issue with diesels. The main purpose of compression (I assume you mean turbo-compression of intake air) is not to heat things up, but to supply more O2. Hot intake air bad, cold intake air good. The heat added to intake air by turbo compression is a bad thing and under sustained high boost can even cause engine overheating.

[tasdrouille]

Originally Posted by instarx

We've all seen old diesels pouring black smoke from their exhausts. That smoke is unburned fuel because a non-turbocharged diesel simply can't get enough O2 when it is under load. Turbocharging the exact same engine will supply enough O2 to completely burn the fuel, improving FE. However, a diesel not under heavy load will not have its FE improved by a turbo.

You don't smoke because you don't have a turbo, you smoke because you are dumping too much fuel in for the air you can get. I had a 1990 NA diesel and it wasn't smoking at all at full load. I can get my 1999 TDI to smoke like an old freight train if I want by offsetting the base inj qty. Most of the time, if your stock diesel is smoking it just means your intake is restricted for the power you're trying to make. On TDIs it's often filling with gunk from the mix of EGR soot and oil from the crankcase so it'll smoke at high loads.

I'm not convinced by the claims of automakers of new turbocharged gas engines that increase FE. I suspect the increased FE comes from use of a smaller engine rather than from the turbos per se.

AH! as I was writing this I see that lunarhighway posted something that supports this thinking... a 0.9L turbo engine replacing a 1.2L NA engine.

There are certain parts of the map where bsfc is improved with a turbo for a given engine size, but downsizing is really where the major benefit reside.

http://ecomodder.com/forum/15012-post5.html

[aerohead]

Originally Posted by mar5ka

Trying to figure out what happened, my mileage was worse with my grill blocked anyone have any idea's, this car rolls almost forever so its not mech. All highway(80) 400 miles rolling hills hardly any wind... my only idea is more air is pushed around the side of the car producing a biger wake---Also I found if I remove my passanger mirror there is a lot more wind noise

1986 Saab 900 with SPG aero package lowers CD down to .38 from .42

Running a grill block, a large flat skid plate (for rocks and smooth air) and a large whale tail( it changes rear angle from 25 degrees to 16 degrees)

By itself,the grille block would not be able to effect mpg by more than 3%.If your mileage is off by a larger margin,we need to look elsewhere for the culprit.