I have an 88 Integra RS (Stock ZC Motor) that gets pretty good gas mileage (27-30 City). I want to install a small turbo (used eagle talon turbo) so that I can add some performance. My question is this, if I absolutely do not care about performance and want a map to maximize my mpg, can that be done? Obviously the turbo will add some performance no matter what, but can the focus be put on mpg? If so, what type of results am I looking to get, in a perfect scenario can the turbo just be used to compliment the engine and not harm
Mpg significantly at all? Thanks for any info guys!!!!!!!!

 

Do not care about performance but are installing a turbo? Makes no sense. You can't predict performance until after the dyno. Tell the tuner what you're trying to accomplish and they'll tune for that.

 

It's all in the tune.
And then mpg will be in the foot.the more your on it the less mpg your get.
The most I have gotten was 35mpg and the less was 26mpg.

 

I think you first need to understand how an engine functions and how it’s function relates to a “tune” before you’ll understand an honest answer.

But my short & sweet answer to your initial question is no. And for your entertainment, my $.02 explanation is: mpg is dictated by how much fuel you deliver through the injectors. The amount of fuel delivered through the injectors is dictated by the amount of air the engine pumps. If you increase the amount of air an engine can pump, you must also increase the amount of fuel to “mate” with that air. Turbos increase the amount of air an engine can pump…

Facts:
Air/Fuel ratio for perfect combustion with gasoline (no leftover oxygen): 14.7:1
Gas, max power rich (n/a): 12.5:1
Gas, max. power lean (n/a): 13.2:1
Richer = cooler combustion temps
Leaner = higher combustion temps

Fuel will always be delivered somewhere in-between those ratios (depending on engine, modifications, tuner, management, strategy, etc.). You can’t change physics or the mixture ratio (significantly anyway). So ultimately, if you want to save gas, pump less air.

 

But turbochargers also increase engine efficiency, so theoretically they can be used to improve fuel economy (by recovering thermal energy that would otherwise be "wasted" in the exhaust stream). There's an interesting discussion here:

http://ecomodder.com/forum/showthrea...ency-1120.html

In practice I agree that buying an aftermarket turbocharger for a Honda is probably not going to have a fuel economy benefit. But it can improve performance without dramatic fuel economy penalties.

And it is possible to tune for fuel economy. You can get minor gains by using a leaner tune than these cars come with stock. You'll get worse noxious emissions though.

 

if you want the best fuel economy leave it stock,they try to get every mpg they can out of these engines in stock form

 

You can tune it for mileage so that when you're out of boost you can reap the benefits. But if you have a lead foot don't even hope to take advantage of it. How much mileage will depend on the tune.

 

mmmm hmmm, I hear ya and I'm sure everyone here knows way more than me.
But if you told me to make as much HP as possible using as little fuel as possible, I wouldn't pick the setup that required .62 lb/hr per HP (FI), I'd go with the one that required .42 lb/hr per HP (NA). FI isn't "free" HP.

And on an engine that consumes a maximum of ~70 lb/hr of gas, how much difference do you think a tenth of a AFR point is worth in MPG? I'll give you a hint: you'll never measure it. But don't take my word for it. Put 130,000+ miles on your own tunes and learn for yourself.

 

When you're not in boost, your turbo is just an exhaust plug - it isn't doing a got-dayum thing to make the engine more efficient in that condition. (and as a matter of fact, this is one of the reasons FI applications have a higher BSFC than NA).

 

I'd like to throw in my $0.02 on hypermileage tuning, and screw up some facts.

I average 54 MPG using a ported .48 AR T25 on a 1psi IWG spring to light arm tension, bone stock Y8 with lightweight pulley & flyweel.

At no point does it ever get richer than 14.0:1 AFR, and I cruise at 16.5:1 AFR with an irrational amount of ignition advance. At full throttle it adds fuel for urgent traffic needs, but otherwise it makes a spine crushing 97 whp.

I adopted Mitsubishi's lean spool concept and keep the heat down with colder plugs & thermostat. It's tuned on a Crome Gold ROM with closed loop wideband, which sadly appears to be the only program that supports a dynamic enough closed loop system for lean operation.

It still does not pass emissions, ironically.

 

Ecoboost, skyactiv, and that crappy Volkswagen were designed specifically to contradict your statement. If your turbo is "appropriately" sized then it increases volumetric efficiency at any point above the centrifugal and induction drag thresholds.

 

mpg fact.
i can get 18mpg( yes i calculated)i got 90 miles out of 5 gallons few times.
or i can get 35mpg driving same route to work( a week after when i decided not to smash on it) highest i got in that car was 190miles on 5 galons freeway
on my stock integra with IHE...
your foot is your best MPG deciding factor.

 

dont most of those cars have EGR that controls EGT via EMS that helps MPG lol

 

So clarify one more thing. Are you saying that if the car wasn't tuned to run leaner OUT of boost that this is not possible? How about just take the turbo OUT of the equation altogether.

 

How? Are you guessing they run leaner than a N/A engine? Are you guessing BSFC is lower? Because you don't need to guess. Get a Harbor Freight OBDII scanner and go for a test drive.

This guy. Less foot, less air, less fuel.

I don't follow you 100%. If it was tuned to run richer in vacuum – is what possible?

This shouldn’t be controversial, it’s old, widely accepted engineering knowledge that 1 turbocharged HP requires more fuel than 1 N/A HP. Why? Extra parts, require extra motion, requires extra energy. Doesn't matter if we're talking about mechanically driving a supercharger or spinning a turbine with exhaust gas, it takes energy from the engine to make it happen. Think about it: if exhaust gas could magically flow through turbos without any resistance, we would have boost with 0 backpressure. And if turbos made your engine more efficient without boost, every N/A engine would come with one (wouldn't that be great!). Turbos definitely pose an exhaust restriction AND they do not make an engine more efficient without positive pressure.

It should be easy to understand that exhaust gas molecules do not seek out or recognize turbochargers - they certainly do not speed themselves up to flow through them. The energy comes from the piston mechanically pushing the pressurized exhaust gas column. An engine requires a lot more energy to push exhaust gas through a turbine than it does through an open pipe (N/A), and that extra energy requires extra fuel. Nothing is free in this atmosphere. Every motion requires energy. Engines and turbos are no exception.

So, could someone tune their combo. to a lean AFR and get away with it? Sure. ICE’s are very forgiving machines. For how long? That's the $64,000 question - and that's why you'll never see a OEM turbo car tuned "lean." Stock Suby's and Evo's dip into the high 10:1 neighborhood in boost. While I'm sure we're all smarter than OE calibrators, I'll go ahead and say if they knew how to safely tune an engine to run at 14.0:1 at max boost - they would.

Air:fuel, pound vs. pound, forced induction requires a mixture about 1 AFR point richer for max safe power. BSFC is richer by .15 - .2 lb/hr. This means every HP made requires .15 - .2 lb/hr more fuel than a N/A engine. To change this, we’d need either a new atmosphere or a new fuel.

Until then, no matter how you slice it, apples to apples, HP to HP, forced induction requires more fuel than N/A.

 

I'm familiar with the science but I'm not even talking about a boosted application. I think that's confusing the issue.

I'm saying that with the right tune, with whatever EMS you're running, you should be able to get better gas mileage. With that said, your tune on a boosted application can also work towards better mileage when you're not in boost; just keep your foot out of it.

While you're boosting is another story altogether so I'm not talking about that nor what an OEM is doing because people will do what they want to do.

I have no doubt that if you went to a tuner and said "Here's what I want to do..." they'll probably oblige you.

 

properly sized turbo that doesnt engage when youre driving at freeway speed or city traffic.

if you look through b series MPG thread that i started. there are quite a few people that have close to 40 mpg on their boosted b series.

 

Clearly you have limited understanding about turbocharging. Most NA engines average 75% volumetric efficiency. Properly turbocharged engines can reach VE as high as 130%, which means they use nearly half of the power to accomplish the same job.

I'm an engineer, I tune hypermileage cars, including my own 54mpg turbo Y8. I'm not going to argue with you about this, because I do what you say can't be done, so please stop giving people bad information.

I'm done with this thread, it's turning into a pissing contest.

 

well from my thermo class back when I was a mech eng major a turbo works a bit like a jet engine (hence turbomachinery) by using wasted exhaust energy to drive a compressor, effectively a 1.5l engine 'breathes' like a 2.0 l engine for example (ie >than 100% volumetric efficiency), which means if all frictional losses from the turbo is ignored you get the power output of a 2.0 litre from a 1.5 litre engine. Of course a turbo has losses too in addition to raising the temperature of the intake air (hence the use of intercoolers) but if these losses are < than the gains in specific HP or torque than in theory you get an increase in efficiency. This principle is not new and has been used for decades in Diesel and marine engines.

http://www.mce-5.com/english/pop_up/...fficiency.html

 

Also how does specific HP and torque (ie a given output /unit volume of engine) help fuel efficiency? well in theory a smaller engine has less mass, and also lower frictional losses (no taking the turbo pumping losses into account). I believe that this is what is referred to as 'downsizing' in the link I posted.

You could get a more fuel efficient or more powerful engine with 4 valves and VVT, a turbo just takes that concept further.

 

A tiny turbo can help reduce pumping loses on the intake stroke.

I had a d15b2 that could cruise between 45-65 mph running leaner than 19:1 with ignition timing between 50* and 55* yielding 54-56 mpg.

 

Vegas, I am interested in your setup, is it possible to PM you for more info?

 

The B2 seems to have a better low end swirl effect than the Y8, I've also had similar results with super lean mixtures on those. It has no ***** though, most of my drivers lose considerable city MPG just trying to keep up with traffic. Shaving the head helps a little.

The 3-stage D15B is more promising, although very time consuming to tune in Crome with the variable Vtec load conditions. I had to customize two special events and shuffle between 3 maps to find the right engagement points. Still only 52mpg N/A but it pulled an 8 second 0-60.

 

these are my current y8 low cam AFR and ignition tables. I guess it's a little leaner than 16.5 in areas. I'm not embedding the picture because it's big and annoying.

http://gravityimports.com/hypermiletables2.jpg

I would strongly advise against using this as a base, this is aggressively tuned with active knock correction. But I think this is a decent perspective at least.
The left column is tuned richer because it likes to buck when it's cold. I've fully tuned this thing a good 15 times and that's the only thing that solved it, it's probably the craptastic DSM injectors I'm using. They have a better spray pattern IMO but they're ancient and don't like the cold.