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Author Topic: DDM s/c mpgs?  (Read 6194 times)

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Offline NormSky

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Re: DDM s/c mpgs?
« Reply #25 on: January 24, 2012, 01:33:57 AM »
I see 40+ mpgs computing it myself. Poor Dave can't come to the fact that turbos are more efficient. :)
07 Sky Hahn Boosted - 44 MPG  40 mpg with air conditioning on.

Offline miller11386

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Re: DDM s/c mpgs?
« Reply #26 on: January 24, 2012, 08:48:37 AM »
I see 40+ mpgs computing it myself. Poor Dave can't come to the fact that turbos are more efficient. :)


Is your tune scary lean or something? 

And I find it odd that we are an hour apart and have never ran into each other
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Offline Dave@DDMworks

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Re: DDM s/c mpgs?
« Reply #27 on: January 24, 2012, 09:17:56 AM »
I see 40+ mpgs computing it myself. Poor Dave can't come to the fact that turbos are more efficient. :)


Norm,

It depends on what efficiency you are talking about ;)

Turbos can help out with fuel efficiency because they put a restriction directly into the exhaust, which does increase exhaust backpressure and cause more spent gas fumes to stay in cylinders, effectively increasing the EGR. That will help with fuel economy since the spent exhaust gases stay in the cylinder and help pack it in instead of bringing in as much fresh air on each piston stroke.

What is your DIC measuring for MPG then?

I am really intrigued by the mileage you are getting actually. It is something I would really like to figure out, and it has nothing to do with Turbo or non turbo being the difference. We have a new test car here that is a 1.4L turbo (smaller engine) that weighs less than your car (about 400 pounds less) with a better C/D, has less frontal area, a much taller 6th gear and smaller tires with less rolling resistance and it is only rated at 40mpg on the highway. We have also done enough turbo conversions here on 2.4L's to see the difference in fuel economy those have had and it does not line up with what you are getting. Also the standard BSFC (http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption) for a supercharged engine is usually estimated between .55-.6 and the turbocharged engine is calculated at .6-.65. What's even more interesting is that I have never heard of a 2.0L GXP getting that kind of mileage before either. If you take a look at the GXP, it beats the 2.4 in every way when fuel economy is the concern. Since it has the same C/D and frontal area as the 2.4L the main difference is that the GXP has a 20% smaller engine then the 2.4L and also the real big difference is the Direct injection. The Direct injection allows us to run a lot leaner during wide open throttle then a regular port injection engine can run. With a port injection engine we have to run 12-12.5:1 air/fuel ratio's and on a Direct injection you can run 13-13.5:1 air fuel at full throttle, of course at cruise you still target 14.7:1 on both engines. The 2.0L engine even has an advantage there since they come with a factory wideband and are much faster to react to changes in air/fuel ratio then the 2.4L's.

Dave Michel
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Offline Dave@DDMworks

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Re: DDM s/c mpgs?
« Reply #28 on: January 24, 2012, 09:31:03 AM »

If you get the right turbo/tuning it can match or better a sc for responsiveness.

I know that you are a turbo fan and think that we only like superchargers here (not true), but this statement is just ignorant to the way that both systems operate. There is no way that a turbo can ever match a supercharger for response based on very simple laws of physics. A turbo can have really good response when sized properly for response and tuned to get the best response, but a supercharger will always beat it for responsiveness.

Lets look at the simple steps required for a turbo car to spool up a turbo to start to compress the air vs. a supercharger.

On the turbo car, the throttle blade has to first open, air has to be brought into the cylinders, that air has to be compressed, fired off, it then expands on the exhaust stroke, then it gets pushed out of the cylinder head, goes through the exhaust manifold and into the turbo. Then that energy has to accelerate a mass (the turbine wheel) for the turbo to start to spool up. Once the turbo spools up it then starts to compress the air coming into the compressor side of the turbo and boost pressure is seen.

On a supercharger car, the throttle blade has to open, the supercharger is directly hooked to the engine belt system and it starts to move more air then the engine can consume (on positive displacement superchargers), boost pressure is seen.

My offer still stands, like it has for years now, when you get a chance come to any of the Solstice/Sky events and get a ride in one of the supercharged cars so that you can actually feel the difference between them, there is no comparison in responsiveness.
Dave Michel
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Stage 3 Supercharged 2.4L - 314whp - 93 octane
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Offline Critterman

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Re: DDM s/c mpgs?
« Reply #29 on: January 24, 2012, 09:33:46 AM »
Dave, Do I have to help you out all the time?  You forgot the rear end gear ratios, the GXP has slightly taller gears :)
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Offline Dave@DDMworks

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Re: DDM s/c mpgs?
« Reply #30 on: January 24, 2012, 09:36:51 AM »
Dave, Do I have to help you out all the time?  You forgot the rear end gear ratios, the GXP has slightly taller gears :)

Yeap, as always ;)
Dave Michel
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Offline miller11386

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Re: DDM s/c mpgs?
« Reply #31 on: January 24, 2012, 09:38:44 AM »
+1 to what Dave said

(Untill your turbo is spooled. Then you will get it like a kick in the pants. Size of the kick depends on the size of the turbo :))
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Offline elff

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Re: DDM s/c mpgs?
« Reply #32 on: January 24, 2012, 09:56:05 AM »
Don't you mean +1 Critter
:D

Offline NormSky

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Re: DDM s/c mpgs?
« Reply #33 on: January 24, 2012, 11:30:32 AM »
LM1 WB reads right 14.7 A/F at cruise. As Dave mentions early about Hahn's MAF the DIC reads 10-12 mpg high compared to dividing gallons by miles.

Driving style, tire pressures, and ambient air temperatures play the biggest role in my mostly highway numbers.

I got a 2.3t Saab that sees similar numbers with the stock 170 HP propelling 3400 lbs and better aerodynamics. So I know it's not the variable rtiming asa the Saab dowesn't have it. With Saab I can watch pre-throttle body  and post throttle pressures and can say pre TB pressures are significantly more. So you might be missing part of the equation. :)
07 Sky Hahn Boosted - 44 MPG  40 mpg with air conditioning on.

Offline miller11386

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Re: DDM s/c mpgs?
« Reply #34 on: January 24, 2012, 12:11:57 PM »
so basically you are getting the same as 2.0 drivers....You show 30mpg (miles divided by gallons put in) but your DIC gives you a false reading of 40-44mpg

Good to know.
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Offline ChopTop

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Re: DDM s/c mpgs?
« Reply #35 on: January 24, 2012, 12:27:01 PM »
I think the better question would have been; are there averages of before supercharging MPG figures available vs after supercharging MPG figures available based on driving style not changing. 

Seems to be a given that once performance increases so does your MPG & driving habits.

Offline elff

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Re: DDM s/c mpgs?
« Reply #36 on: January 24, 2012, 12:28:26 PM »
First week I had my 2871 I was thinking
Man this things eats gas like a Pig

But then when I drove like a normal person, I realized I get slightly better gas mileage.

Offline miller11386

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Re: DDM s/c mpgs?
« Reply #37 on: January 24, 2012, 12:52:44 PM »
Same here elff. Took a while to get a good tank through it without me flogging on it though!
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Offline Wartie

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Re: DDM s/c mpgs?
« Reply #38 on: January 24, 2012, 01:00:29 PM »
Same here elff. Took a while to get a good tank through it without me flogging on it though!

Yeah you two had me scared about MPG for a while, but I did the 2871 anyway. Miller you are correct don't flog it and you get good MPG.

Offline JimmyBaja

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Re: DDM s/c mpgs?
« Reply #39 on: January 24, 2012, 01:20:46 PM »
Norm you can ask "The Boss" about the response difference between the s/c & turbo, he knows first hand.  :lol:  Sorry Boss, I couldn't resist.

Seriously, i'll take the instant power over the turbo anyday, it's just more usable unless you plan on racing & staying in the trippel digets.  :)

Offline Sol Asylum

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Re: DDM s/c mpgs?
« Reply #40 on: January 24, 2012, 02:13:20 PM »
First week I had my 2871 I was thinking
Man this things eats gas like a Pig

But then when I drove like a normal person, I realized I get slightly better gas mileage.

I don't understand how does having the seat slid back from the most forward stop and removing the booster seat affect gas milage?
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Offline elff

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Re: DDM s/c mpgs?
« Reply #41 on: January 24, 2012, 02:24:57 PM »
When you can barely reach the pedal, you can't floor it

DUH!!!!
:D

Offline NormSky

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Re: DDM s/c mpgs?
« Reply #42 on: January 24, 2012, 09:15:59 PM »
Miller, the Hahn Turbo DIC reads into the mid-50 mpg range. :)

There is no turbo lag with this setup in an autocross. Had I had a better clutch I would have bested FTD dune buggy with Porsche drivetrain. :)
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Offline miller11386

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Re: DDM s/c mpgs?
« Reply #43 on: January 24, 2012, 09:18:47 PM »
Miller, the Hahn Turbo DIC reads into the mid-50 mpg range. :)

There is no turbo lag with this setup in an autocross. Had I had a better clutch I would have bested FTD dune buggy with Porsche drivetrain. :)



Lagless turbo? that just means it has no powa
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