Carbs vs FI Options

[SirAndy]

so steve, this dyno sheet is from one of your motors with *your* FI on it ???

(IMG:http://www.914world.com/bbs2/html/emoticons/idea.gif) Andy

[lapuwali]

Which ECU is, IMHO, not all that relevant, assuming any ECU can be tuned appropriately. What IS relevant to this particular comparison is the fact that carbs were swapped for throttle bodies. If you plot the two power curves on the same scale, you'll see that the difference in power rises as the revs rise. Under about 4000rpm, they make the same power. Above that, the EFI engine's curve rises away from the carb'd engines curve. This strongly suggests that the carbs used in the comparison were too small, and were flowing too little air at upper revs. The freer flowing throttle bodies kept flowing, so they produced more power at higher revs.

Jake's results show similar curves when layed atop each other. The divergence happens a tad earlier on those graphs (3500 rather than 4000), but it's still close.

This doesn't mean this is an unfair comparison. One of the advantages of EFI is that the effectiveness of the fuelling is decoupled from the air velocity through the throttle body. In a carb, if air velocity falls too much (carb too big), fuel control gets very erratic. So, an engine with big carbs tends to suffer from poor drivability, so for a daily driver, you tend to deliberately run carbs that are too small to keep good fuel control. In an EFI setup, flow velocity is irrelevant to fuel control (but NOT completely irrelevant to power), so you can run bigger throttle bodies with EFI and retain good drivability, thus getting the high rev benefits of big throats with none (or few) of the downsides).

If you used, say, 44IDFs with 36mm venturis, and compared them against 36mm throttle bodies, you'd see very similar power figures. Comparing 44IDFs with 50mm Jenvey throttle bodies is not an apples to apples comparison, even though a well-tuned EFI setup with those TBs would probably drive just as nicely as the same engine with well-tuned 44IDFs.

Sanity is restored. Now I understand how this 30% number is possible.

So, bolting aftermarket EFI onto a 914 engine using the stock intake plumbing will NOT give you a 20-30% power increase. It MAY help if you use a larger throttle body. Using a throttle body that flows more than the engine will take offers no help at all to power, and only makes the throttle action "jumpy", as you're changing the ratio of throttle pedal movement to airflow into the engine. Since it's very likely (but unconfirmed) that the stock throttle body is adequate for an otherwise stock 2.0, it's very unlikely adding a bigger one will help. So, you're not going to see much, if any, power increase by using any aftermarket ECU with an otherwise stock engine in place of an otherwise properly functioning D-Jet or L-Jet system. 5% is pretty much the outside, by simply cleaning up the fuel delivery a tad.

[tnorthern]

QUOTE

so steve, this dyno sheet is from one of your motors with *your* FI on it ???

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)

[SirAndy]

QUOTE (lapuwali @ May 9 2005, 12:49 PM)

Which ECU is, IMHO, not all that relevant

i have to dis-agree.

first, the ECU is only one part of the equation and second,
if i was to fork out $2000 for a FI setup you better believe that i would want to see some dyno sheets with that particular setup installed on a comparable motor and not some graphs from a motor and injection system that has nothing at all to do with his product and engine.

ok, so now we have general *proof* that FI can give you more HP than carbs, way cool, except, i'm a FI guy, i knew that all along.

what does that say about steve's product?
absolutely nothing!

(IMG:http://www.914world.com/bbs2/html/emoticons/cool_shades.gif) Andy

[ArtechnikA]

QUOTE (lapuwali @ May 9 2005, 03:49 PM)

...One of the advantages of EFI is that the effectiveness of the fuelling is decoupled from the air velocity through the throttle body.

not just EFI :-)

but yes. a carburetor *MUST* introduce a restriction into the airstream. it is the pressure drop through the venturi that makes it work in the first place.

FI throttle bodies present very little restriction and only meter the air to match what the engine requires. (and in the case of slidevalve TB's - ZERO restriction...)

Diesels - which always operate in excess air - don't even have throttles - their injection systems just meter fuel. (exception - okay - modern computer-controlled Diesels like TDI's have throttles for emissions, to help control the NOx...)

[jgiroux67]

QUOTE (Aaron Cox @ May 8 2005, 09:18 PM)

only street car i know of that is NA & ,akes more than 100 hp a liter is the s2000 (lots of modern tech in it)

2002 and up BMW M3 3.2- 3.3 liter and 333 hp stock
Maclaren F1 6 liter 627hp
Honda S2000 and I think the Integra GSR does as well

[ArtechnikA]

1974 Carrera RSR - 3,0 liters, 320 HP.

30 years ago hi-tech...

[lapuwali]

QUOTE (ArtechnikA @ May 9 2005, 02:04 PM)

QUOTE (lapuwali @ May 9 2005, 03:49 PM) ...One of the advantages of EFI is that the effectiveness of the fuelling is decoupled from the air velocity through the throttle body. not just EFI :-)

Quite true. MFI is the same way, as is CIS (though it moves its intake restriction elsewhere).

Carbs do and must introduce a restriction to work, but it's not usually so bad that it drops top-end power by 30%. That 200-230hp Type I would probably produce just as much power with 48IDAs as it does with the FI, though it may very well need to idle at 2000rpm and fall on its face trying to accelerate from anything below 4000rpm.

[lapuwali]

QUOTE (ArtechnikA @ May 9 2005, 02:35 PM)

1974 Carrera RSR - 3,0 liters, 320 HP. 30 years ago hi-tech...

The RSR wasn't really a road car, though. 100hp per liter was commonplace in racing engines as early as the mid-50s. Substantially more than 150hp/liter was common by the early 60s. The 1961 BRM 1.5V8 made 240hp. Making 100hp/liter NA hasn't been difficult for quite some time. Of course, we haven't even started mentioning road bike engines, which have been north of 150hp/liter for decades. And they idle well and have acceptable (though only barely in some cases) powerbands. Emissions are also getting to be pretty good, with some current bikes even having catalytic convertors and full closed loop EFI systems. 100hp out of 600cc is boringly common now, or 166hp/liter. Just imagine a 280hp 1.7 914...

[anthony]

There's a guy on the Pelican 911 BBS that developed a Megasquirt based kit for the 911SC.

http://www.bitzracing.com/

He's claiming a 23hp increase over CIS. With SSI headers and Megasquirt he's 40hp above stock.

http://www.bitzracing.com/gallery/Tony_78_911SC.html

[lapuwali]

QUOTE (anthony @ May 9 2005, 02:59 PM)

There's a guy on the Pelican 911 BBS that developed a Megasquirt based kit for the 911SC. http://www.bitzracing.com/ He's claiming a 23hp increase over CIS. With SSI headers and Megasquirt he's 40hp above stock. http://www.bitzracing.com/gallery/Tony_78_911SC.html

CIS also has a significant top-end restriction from the airflow meter. I'd bet money that a before and after dyno chart would show the same thing as the previous charts: all of the increase is above 4000rpm. 23hp is also about 13%, not 20-30%. 40hp is 22%, and I'll bet the SSI header swap also involves removing the cat. His data also involves an arbitrary 15% bump to convert RWHP to crank HP. With no RWHP data prior to the swap, there's no real way of knowing how big the actual power increase is, unfortunately. 13% from removing the airflow meter is believable, though.

[anthony]

It would have been nice if he had done back to back dyno tests. Still, he's produced a great figure with just SSIs and EFI. It puts him in 3.2L territory for a lot less money than an engine upgrade.

Anyway, I can't wait to see Jakes dyno figures for his 2056, 2270, 2316 motors with carbs and then with EFI.

[grantsfo]

QUOTE (jgiroux67 @ May 9 2005, 02:33 PM)

QUOTE (Aaron Cox @ May 8 2005, 09:18 PM) only street car i know of that is NA & ,akes more than 100 hp a liter is the s2000 (lots of modern tech in it) 2002 and up BMW M3 3.2- 3.3 liter and 333 hp stock Maclaren F1 6 liter 627hp Honda S2000 and I think the Integra GSR does as well

Lotus Elise 1.8 and 190 hp and Toyota Celica 1.8 180 hp both are powered by the same Yamaha designed powerplant and make 100 hp per liter or more too. Acura RSX also makes over 100 hp + per liter.

[Andyrew]

They can do it with sbc's..... lol

Remember Jake being very impressed with Kit Carlesons EFI kit? I remember him being a skeptic, then completly converted after toying with the kit.

and yes, kit carleson efi is not avalible...

Andrew

[Mueller]

QUOTE (SirAndy @ May 9 2005, 02:33 PM)

QUOTE (lapuwali @ May 9 2005, 12:49 PM) Which ECU is, IMHO, not all that relevant i have to dis-agree. first, the ECU is only one part of the equation and second, if i was to fork out $2000 for a FI setup you better believe that i would want to see some dyno sheets with that particular setup installed on a comparable motor and not some graphs from a motor and injection system that has nothing at all to do with his product and engine. ok, so now we have general *proof* that FI can give you more HP than carbs, way cool, except, i'm a FI guy, i knew that all along. what does that say about steve's product? absolutely nothing! (IMG:http://www.914world.com/bbs2/html/emoticons/cool_shades.gif) Andy

I dis-agree with your dis-agreement (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

I'd say any of the commercially available (and even the Megasquirt) electronic fuel injection ECU's can attain the same level of HP numbers if all the hard parts are the same (throttle bodies/injectors)

the biggest differences between all the ECU's are the available inputs and outputs for "extra's" such as fan control, boost control and other cr@p that 90% of us will never use or need.....

sure, some ECU's have better resolution on the MAP tables, but an ECU with an 8x8 table can have just as much power as an ECU with a 16x32 table...IMHO (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

In the right hands and tuning, I bet a Megasquirt controlled motor can pull the same numbers as this Steve's Emerald or even a $4K MoTec system......

[ArtechnikA]

one last road car number, for Porsche content:

Carrera GT - 5,7 liters, 612 HP

[Jake Raby]

The only way to solve this debate is with some graphs... I did some testing today, will do more next week and so on and so forth. Now that the 16 channel data logger is here and all hooked up I can see everything clear as day and log it as well and even upload complete dyno runs.

As for the 2054 graph posted, I cut my teeth on TI engines and I'll say that is more than likely a Turboed engine, look at the torque...

I have 11 solid weeks of FI testing coming up starting week after next, during those 11 weeks I will log more data than anyone can imagine!

I was not super fond of FI until I worked with the Kit Carlson package and then experienced it.. After seeing the huge power gains that we saw in that testing I saw a huge and easy way to make my engines more powerful and better yet run even cooler. This alone opens up doors that are otherwise closed and allows more development to be done.... Hell, thats how the "Super 2 liter Plus" is going to make its goal of 50 MPG and 110 HP.... It'll be assembled in less than a month..

Just wait till you see the 2 liter 356 engine I'm building for LN Engineering........ Every modernization available, plus EFI and about 190 RELIABLE ponies.... Nuttin outflows the 356 head! (except my billet monsters)

[MattR]

50 mpg? I hate to be a skeptic... but I'll believe it when I see it. Modern engineers are struggling to make hybrid technology get 40 mph with under 100 hp.

[Jake Raby]

Thats the goal- 50 MPG...

I have attained 40 from my 2056 in the 912E and that engine was not built for such a feat..

We are shooting for this as a challenge, the engine combination it will take to do it has been in development for 2 years in the heads of Len and I so we are throwing every trick we have at it.

I seriously think that some corrupt bastard in the gevernment thats an oil tycoon is keeping the development of super efficient engines down or something!

I will be happy if we get 40 MPG with the combination, but 50 is the goal... The gearing is being set up specifically to keep this baby at peak torque on the highway and the engine will run very cool with its DTM and etc and that will help. I am quite sure we can average 40 MPG with this baby when its all said and done especially with is long stroke, small bore and every friction reduction known to man from a Ion Nitrided crank to ceramic lifters to even DLC coated valves rockers, pushrod tips and oil pump gears.... Chris Foley is building a header specifically for the project as well.

BTW- Those engineers aren't very effective most of the time!

[ArtechnikA]

QUOTE (MattR @ May 9 2005, 10:39 PM)

Modern engineers are struggling to make hybrid technology get 40 mph with under 100 hp.

modern engineers need to keep chasing emissions numbers set for the next 5 years...

i believe that an efficient engine is a clean engine, but nobody has been talking about making aircooled engines meet 2010 emissions standards.