It is a known fact over in the US, in the big-block tuning world that blowers help fuel economy and lower emissions, as much as it does increase power of course.
The reason is that the blower is mighty good at mixing the fuel and air, and the mixture gets to the combustion chamber very well vaporized, avoiding the usual thicker droplets running down the ports wall.
So yes, you get better mileage for comparative power outputs (that means same overall speeds, that means not opening the throttle too much, like cruising or in motorway use)
And reduced emissions.
i’d have thought it was fairly easy to believe you can get a more efficient ‘burn’ using a properly tuned ecu with a turbo or super charger??.. therefore more fuel efficient (esp in relation to power output)…
on the related note you mention - i also always believed turbochargers were more efficient than superchargers because they aren’t continuosly driven… thus don’t sap energy all the time… of course, superchargers also don’t suffer lag… but that’s not the issue here i s’pose.
Uldis please point me to some info. If this was the case why is it most modern Superchargers feature a bypass so the Supercharger is not boosting at cruising speeds or low throttle opeinings. If there was something to be gained in fuel economy why fit a bypass?
Rox, I’m not a techie as you know But here’s my thinking. You’re driving a car at say 70mph if you know the cd figure of the car then you can work out how much power at the wheels it will require to overcome drag and maintain 70mph. So in an NA car you may need to be at say half throttle. Fit a supercharger and your foot may only need to be at say 1/4 throttle. Are you saving 25% gas? I don’t think so because you are still needing to make the same hp at the wheels to keep the car at 70mph.
The fuel going into the engine has a certain amount of potenial energy. Some is lost as heat (a lot!), some is lost through internal friction and some through the drive train. A relatively small amount of that potenial energy is actually used to turn the wheels. Now add a Supercharger into the equation - the above loses remain but in addition some is lost driving the supercharger - for an efficient screw type Supercharger flowing 265cfm it’s around 20hp!! So you need more energy i.e. fuel to compensate for this additional loss.
Although your are increasing the volumetric efficiency by forcing more air in you also need to maintain the correct AFR so you are also forcing more fuel in.
A turbo charger is more efficient because it is reclaiming some of the heat energy that would otherwise be lost through the exhaust. There are no free lunches if you want more power you need more energy or you need to make better use of what you have (i.e. less losses through friction etc) - energy output cannot exceed energy input - since the supercharger itself consumes energy it cannot use less energy than a NA engine at a given output i.e. maintaining 70mph.
I didn’t know any car had a bypass. It seems to me ridiculous, unless it’s to make it more docile at low speeds or partial throttle openings.
Never heard of that.
OTOH, all you say is correct, but you’re not taking into account what I mentioned before.
If in a NA engine, part of the fuel/air mixture is used to push the piston down, not all.
Actually, only the mixed part burns efficiently, and you had to put some extra fuel in the system, because not all of it will mix. This is the problem. Part of it will stay in liquid form, wetting down the walls of the ports, and sliding down the combustion chamber, not burning properly.
In a supercharged engine, the blower (especially the Roots ones) are very efficient at mixing, so actually less fuel is needed to acieve the same mix concentration.
This will also help emissions, because all the fuel will burn more eficiently.
Now, this is petrolhead talk, people that have installed SC’s tell these stories about lower emissions, increased fuel mileage, etc.
Take them with a grain of salt. I don’t have a SC, maybe some day will.
Apart from that, yes, you lose a bit of power to turn the SC, but not as much as you think at low revs. Maybe more at high revs.
Uldis think about it. You’re cruising along and take your foot of the throttle. The butterfly is closed but the supercharger is still trying to stuff air into the engine, hence the bypass.
Regarding your reasoning about the supercharger mixing the mixture, why is it most don’t do it this way? The fuel is injected after the compressor. When you think about it how could it be any other way for a multi-point fuel injected engine. If you throw away your fuel rail and put one giant injector before the compressor your AFR will be all other the place. As some of the fuel air mixture bounces back and forth between the manifold and compressor (in a Roots type blower this happens).
Don’t know who’s telling you this stuff but I ain’t buying it…
You’re right.
Most of these guys aren’t running MPFI, but either big 4 holleys or just one big injector before the blower.
Never heard this comments with MPFI.
So there you go, it works with just one big injector before the blower.
(pick any custom car magazine and you’ll see what I mean)
two thhings i still wonder about from what you are saying…
i agree basic energy law (well why wouldn’t i !!) input energy=output energy… but… sort of for the reasons mentioned by Uldis above in an NA engine some of the chemical energy stored in the fuel just stays there because it doesn’t burn. However, in a forced induction engine its easier to get the perfect AFR (or closer to it) all the time therefore we get more chmical energy (from fuel) being transferred into the mechanical/kinetic energy that we are looking for - even tho some of this is used to drive the supercharger, i can believe its a trivial amount of it. I also understand that most of the stored chemical energy ends up as heat and the supercharger will generate more heat than the NA… however, again I can believe its less than you gain in forward motion of the vehicle.
I’m pretty sure that not all superchargers are upstream of the butterflies… in fact doing this frequently allows you to ensure the butterflies end up inside the combustion chamber… … pistons and valves dont like that… the best place to have a supercharger compressor is after the butterflies and i can vaguely understand how this would be better at the ‘mixing’.
(i know i only said two… but you know how it goes when you start to spout… ) We all know its a fact that forced induction generates more horsepower than NA… are you saying this is due only to having a bigger charge (eg more air AND fuel in the chamber) and not also because we can get more energy out of the fuel (due to burning more of it instead of letting it spill down the insides) ??
Uldis, put those tuning mags away! I haven’t found anyone making a supercharger kit for a modern engine with the fuel/air mixture passing through the compressor - they may exist but the majority don’t do it this way. Ask ahki where the injectors are on the JR kit.
Rox,
However, in a forced induction engine its easier to get the perfect AFR (or closer to it)
Nope, as a rule most FI engines are set to run richer to avoid problems with pre-detonation. Which is why ahki was claiming to use AVgas a higher octane reduces pre-detonation allowing more aggressive timing.
I’m pretty sure that not all superchargers are upstream of the butterflies
Correct didn’t say the butterfly was downstream just the injectors. Not that it matters anyway.
We all know its a fact that forced induction generates more horsepower than NA… are you saying this is due only to having a bigger charge
Yes, shove 50% more air and fuel into an engine and you’ll get a 50% bigger bang.
i will be happy to show you next time you come the the “Nordschlefe” how fast my car is. I think the track only shows how driveable your engine with a turbo will be against mine.
My car is ver reliable and revs with any problems 9.300. Infact i have seen many cars come to germany with lots of HP and lost some of it on the way over the sea! But still, i do not understand why many of you always know better about engine tuning and espaccily about my engine and for example my throtlle bodie kit, btw. it has an airbox fittet. And yes Ahki it fits, maybe not the Toda i will agree, but there are other companies out that built these airboxes with the right fttet air horns.