My augment as shown before is that your fuel economy will be lower if you mod your 1.8t to 400+ hp (and yes I specifically said 400+ hp, you can check the last thread if you don’t believe me though these same effect can likely be seen before this level) both on the highway and in the city. The city part we both agree on so we don’t need to go there but you say there is not drop in fuel economy on the highway. While I can agree that the drop in highway mileage won’t be nearly as drastic as the drop in city mileage, there is still a drop.

Everyone knows the compression ratio of a turbo charged engine is lower than a naturally aspirated engine. Everyone also knows the lower the compression ratio the lower the fuel economy. Of coarse it doesn’t matter that turbo cars have lower compression ratios because they have a turbo.

So now you are cruising along in you 400hp a4 and you are not in boost. Say you want to pass someone or you come to a slight incline. Naturally you press the gas …but wait. Now that you upgraded you turbo there is more lag so there is less response, so you have to press the gas harder. Finally you press the gas hard enough for the turbo to respond but guess what, you had to press it harder than before thus the ecm gives the engine more fuel in order to spool the turbo (sure not much but more).

But let’s say you just need a little power and not enough to spool the turbo. Well in this case you will still get a decrease in fuel economy because the compression is much lower now that you don’t have that little turbo with its quick response (even if you only need a little boost). To say that when you’re not in boost your just running like a little 1.8L is just not true. Fact is you’re running like a 1.8L with a low compression ratio that’s not designed to run in an n/a state. To add to that, all the component in the 1.8t are geared toward forced induction (intake manifold etc.) and would run poorly even if retuned in a naturally aspirated state. Don’t believe me. Take off your turbo, have someone retune your car and see if you make anywhere near what a Toyota yaris with a 1.8L engine makes (136 hp). It won’t happen.

In other words, you take away that low to mid boost (which I think we can all agree will happen with a turbo that supports 400+hp) that the 1.8t needs and it will require more fuel (even if ever so slightly) to cruise at the same speed because you lose that compression when under light loads. This is espcially true when say you go to accelerate even slights

The problem gets even worse if you upgrade you internals and have an even lower compression ratio.

Parts

From what I’ve seen at the VWvortex forums it seem like most people are begin to upgrade more than just the turbo at 400+ hp. Say for example you upgrade you intake. This new intake is great for more power and allows more volumetric throughput but guess what. Unlike the stock intake, it’s not designed for maximum fuel economy, it’s designed for power. The flow at idle and lower rpm’s is not nearly as ideal as with the stock intake. Even simple porting can change the characteristics of little load conditions. And lets say you want to upgrade your cams. Well I don’t think we need to talk about what the longer duration and higher lift of an aggressive cam does. Though I must admit this may not be a problem cause it doesn’t seem like a lot of people upgrade cams at this hp level though some do.

Injectors

The job of the ecm is to keep the afr as stable as possible but it’s a known fact that the bigger the injector, the harder it is to keep the afr stable at low rpm (when very little fuel is needed) especially under light engine load. If you get big enough injectors it has even been known to affect idle making it less stable and more erratic though I know most people here aren’t running big enough injectors for latter part, it can still be said for midrange load. Again I will admit this may not be a problem with only 400hp.

I agree the the change in fuel econmy on the highway is not nearly as drastic as your city milage but to say the mileage is not affected at all especially at or around 400hp just isn’t right. Just because you’re not in boost doesn’t mean you engine will behave like a naturally aspirated 1.8l engine. If you don’t believe me go to the forced induction section atls1tech.com or the masters of turbo at turbomustangs.com and they will tell you the same thing. I know because I have asked.

 

agreed

but he wants cincytt to come argue with him, thats the whole reason he made this thread.

 

Lmfao.

 

well kinda. i just didnt want to take up space in threads that had nothing to do with our arguement so someone suggested i post here...or something

 

As said in your other derailment.... go here and read. Its more than answers everything. If you dont believe it still, you are lost and hopeless. I wont argue with the ignorant that wont except facts.

 

nerds haha

 

im not going to read your first post, i don't need to. but i amgoing to post this here as well as the other thread you repeatedly scewed off topic.. reasons being,one, so i can make sure you will see it. and two, so everyone else that is as dumb as you can see it also...

you do realize how power/torque is acheived and made on an internal combustion engine don't you? and more importantly, how it is delivered?

well let me get you up to speed on that last bit in a somewhat short explanation.. that "400hp engine" (we'll use mine as an example here) does not deliver that 400hp throughout the entire powerband. my engine spinning at 6000 rpms, with 25lbs of boost mixing with maxed out 440cc injectors will make 400hp. but only for a short time.. just look at any dyno plot posted ANYWHERE. there is a torque curve and a hp curve(hp is a calculation derived from the torque prduced from your engine. HP = (TQ*RPM)/5252) this is why you will always see the hp and tq lines cross at exactly 5252rpms. everytime. the curves start low at less than 100hp, then rise to their peak hp a tq. like 400hp for this example.

if you notice when watching cars on dyno's, you'll see them "cruising" along on the rollers before they start. usually about a 50mph cruise, then they drop the hammer and the hp and tq curves start to rise and they eventually maxout then they stop.. on most dyno plots you'll see a section that states: "hp at 50mph = 50".. that is the power used to maintain that speed, at that rpm. no cars are using all of their potential power all the time. while decelerating, cruising, or at a slight acceleration, most cars don't even use half of their potential power.simply, lessair/fuel mixture= less power. and less power = less fuel consumption(pretty much a "A = B and B = C" equation)

you need to pay attention to the amount of air and gas that is put into the engine. as that will determine a majority of you MPG..

as of right now, my motorhas the potential of putting out 400+hp at any time. but on average with 90% city driving, i get 25 mpg. on the highway, i get over 30.

there, i explained it in the only way Cincy or others haven't yet. maybe this will make you understand. if not, if you don't believe common sense and real world experience, then thats up to you..

but either way, just DROP IT

 

what where in the hell do i suggest that your always using max power any where in any of my posts?? holly sh*t its clear im not gunna prove anything to you audi guys (some of you), youre just gunna ignor me and give me redicluous claims but appeartly thats cause you guys know everyone thing about turbos. not those guys making 1000+hp, not the guys who actually race thier turbo cars for a career, in other words not those guys who i have persnoally talked to who actually build car and dont buy kits. if those guys at trubomustang or ls1tech tell me one thing, i can guarenttee they know their ****. think ill take thier word for it. christ.....

 

we've provided practically every reason to prove our point, yet i haven't even heard you try and prove your point. so why don't you try and prove why a 400hp a4 cruising down the highway gets worse gas mileage than a stock a4, and we'll tell you why your wrong.

 

+1