EFI or Carb why not both ?

[JeffMcKC]

From John Marcella he makes some bad assed intakes if you dont know his work.

http://www.yellowbullet.com/forum/showthread.php?t=127750&highlight=john+Marcella

Injector sizing

2 per cyl. 1 on the roof 1 on the floor. Hard to beat the pattern of multiple injectors.
Or you could run both. I have been trying to get someone to run EFI with a carb. The carb to handle approx 60% of the fuel requirements and the injector the other 40%.
This would give the cyl to cyl accuracy and tunability of EFI with the emulsification benefits of the carb. Plus your carb guy can do more things with carb to break up the fuel because they dont have to worry about keeping the fuel curve. But its money and weight, and a learning curve so i have not gotten anyone to try it. Just my 2cents

[TheSilverBuick]

Re: EFI or Carb why not both ?

Nifty idea. Run a fuel map with no fuel being delivered at idle-low rpm, then just use individual cylinder tuning to trim up the delivery and bolster the delivery under heavy load.

Only down side I see to it (other than running a dual fuel pressure system) is that you are pretty much needlessly running a restriction in the intake. Though perhaps running an excessively oversized carb, under jetted, for the engine might off set that....

[TC]

Re: EFI or Carb why not both ?

From John Marcella he makes some bad assed intakes if you dont know his work.

http://www.yellowbullet.com/forum/showthread.php?t=127750&highlight=john+Marcella

Injector sizing

2 per cyl. 1 on the roof 1 on the floor. Hard to beat the pattern of multiple injectors.
Or you could run both. I have been trying to get someone to run EFI with a carb. The carb to handle approx 60% of the fuel requirements and the injector the other 40%.
This would give the cyl to cyl accuracy and tunability of EFI with the emulsification benefits of the carb. Plus your carb guy can do more things with carb to break up the fuel because they dont have to worry about keeping the fuel curve. But its money and weight, and a learning curve so i have not gotten anyone to try it. Just my 2cents

Kind of like running a "wet" nitrous system on a fuel injected motor.

[dieselgeek]

Re: EFI or Carb why not both ?

I think the flaw in that idea is the incorrect presumption that a carburetor is better at atomization or emulsification - or homogenization for that matter.


The reason nobody runs both (my opinion) is because the .001% of people that explore what's really going on, find out that their preconceived notions are wrong.

Note that no OEMs run carbs + EFI, and who around here has done more research on atomization, homogenization of mixture than the OEMs? nobody, that's who.

Although if anyone wants to man up and give it a try, you know I am down! We're looking at doing something similar wth MFI on a Nitro engine, to be able to run affordable EFI/Nitro. Let the MFI system (Gene Adams!) feed about 75% of the fuel, then let the EFI system do the trimming and enrichment. Best of both worlds, only because you can't feed enough nitro into a cylinder with EFI nozzles unless you use shitty nozzles that we don't like.

[dieselgeek]

Re: EFI or Carb why not both ?

I should add, I am personally going through a period of "changing my preconceived notions" about both Carburetors AND Electronic Fuel Injection.

The more complicated you get with EFI, the more distance you put on the carbs. It's a real fact that EFI makes more power, ALWAYS, when implemented properly. I don't care what WJ said at any point in time, because I believe he's spent less than .1% of his time studying EFI and the other 99.9% maximizing carburetion.

The more you study this topic in real world testing - the more you understand why F1, and motorcycle engines, and anything else pushing the limits of HP/cubic inch, or maximizing emissions, or both - are running EFI and have been for years.

The more complicated you get with EFI, the more you (I) appreciate the simplicity of a carburetor. Achieving 85% of your engine's power goals is easy and cheap with a carb. Getting that other 15% doesn't just mean "sticking EFI on there" (although, benefits like Randal observes - cold start, baro correction etc IS nice to have). Getting that extra 15% squeeze from your engine's potential power is probably 99% more effort than sticking the carburetor on the top and being done with it. Some day (after October) I'll share what I am learning this year. I never thought I'd be studying airflow like I am now, but it's recently started to come together and now I understand why certain things are the way they are. Motorcycles, F1 engines, etc.

[Tazracing]

Re: EFI or Carb why not both ?

D/G'S THATS GREAT AND ALL,
but have you spent any time with a simple as rocks carb..
sometimes that last 1% of extra power isn't worth the hours and money..
that a 100.oo carb can almost get..
I'll learn first hand as my engine will be carb'd first then injecton so I'll be able to see/feel the difference in it at the power and cost..
one thing a carbs got over efi is on the side of the road a flat blade screw driver and vise grips can get you back on the road

[TC]

Re: EFI or Carb why not both ?

The more you learn the more you'll find that there is a place for everything, carbs have their place just like EFI does and it's obvious that they both can get the job done.

As for your claim that EFI will give you 15% more power over a carb, I'd like to see some sort of testing to back that up. I'm not saying it's not true, but I would like to see some sort of comparison, maybe that is something DF might want to look into, maybe they could even get you to tune the EFI setup.........

[TheSilverBuick]

Re: EFI or Carb why not both ?

one thing a carbs got over efi is on the side of the road a flat blade screw driver and vise grips can get you back on the road

Never stopped me, and I drive in places where you can go 100 miles with out cell phone service. And more people are driving more miles with EFI than ever before. The only time the fuel system has left me on the side of the road is when my cheap universal priming pump would fail. And it's the same electric pump I was using on the carb, which back then would leave me stranded anyways.

[dieselgeek]

Re: EFI or Carb why not both ?

D/G'S THATS GREAT AND ALL,
but have you spent any time with a simple as rocks carb..
sometimes that last 1% of extra power isn't worth the hours and money..
that a 100.oo carb can almost get..
I'll learn first hand as my engine will be carb'd first then injecton so I'll be able to see/feel the difference in it at the power and cost..
one thing a carbs got over efi is on the side of the road a flat blade screw driver and vise grips can get you back on the road

Yep, sure have. In fact they've been comparing the EFI to carb on the Engine Masters project and you can be sure if the carb could hang with the EFI, they'd be running a carburetor.

It doesn't take much studying however, to compare 8 high pressure EFI nozzles, some of which have as many as 8 holes apiece (64 orifices running at 45psi pressure), versus a carburetor's maximum of 4 orifices running at just a couple psi pressure differential; the argument that a carb is better at atomization holds zero water unfortunately. I think a recent proof of that is in that Ray Barton Hemi we tuned a few weeks ago. You hear everyone talking about the fact that we made about +50hp over the carb everywhere in the curve (at comparable RPMs - the carb couldn't run the engine at max RPM)... but what you don't hear people talking about, is the fact that the EFI used exactly 40% less fuel to make more power than the carb. What that tells you is, the EFI is inserting smaller droplets of fuel into the air charge. Larger droplets, from the carb, require a greater mass quantity of fuel to get the same quantity of "burnable" fuel into the combustion chamber.

But you're absolutely right - one must consider the effort and resources required to get that extra power. That being said, you cannot assume that every single carburetor is also achieving 100% of its potential. It's just as hard to maximize a carburetor as EFI up to the same power level - to go ever further, requires EFI *and* a ton more resources, time, testing.

For 99.9% of the users here, carbs are fine.

[dieselgeek]

Re: EFI or Carb why not both ?

one thing a carbs got over efi is on the side of the road a flat blade screw driver and vise grips can get you back on the road

That's not true at all.

Any carb failure that requires parts, is going to result in "ordering parts" from the parts store - that stuff just isn't carried in stock anymore. Rebuild kits, gaskets, etc. are hard to come by in a store.

Meanwhile, every part of Randal's system under the hood: coolant temp sensor, MAP sensor, air temp sensor, and TPS sensor - all he really needs to run the engine - is found right now at a parts store for cheap. None of those parts is over $15 except a TPS, which might be $25.

This is an example of a preconceived notion that you have, that is inaccurate.

[dieselgeek]

Re: EFI or Carb why not both ?

As for your claim that EFI will give you 15% more power over a carb, I'd like to see some sort of testing to back that up. I'm not saying it's not true, but I would like to see some sort of comparison, maybe that is something DF might want to look into, maybe they could even get you to tune the EFI setup.........

That's not a claim, it's an observation on the whopping TWO engines I've worked hard enough to study this on. That's not a lot of test cases! that's why I didn't say you'll always get 15% more power but, it seems to be a common number.

Believe me, the effort it takes to squeeze that extra percentage is almost never worth it, unless you are racing Superstock or Prostock, or competing in Engine Masters where every little percentage counts.

Also, you keep implying that I claim EFI is always the better choice. I never said that, I just said it will always have a greater power potential. The rest is shit that you are making up to create an argument that isn't there. If you want respect, stop doing that.

[JeffMcKC]

Re: EFI or Carb why not both ?

Geek I think its more a question, none of us know what will happen when working with Carbs that cost 10,000.00 a peice and a proper intake. He is just saying it may be worth a look

[dieselgeek]

Re: EFI or Carb why not both ?

Geek I think its more a question, none of us know what will happen when working with Carbs that cost 10,000.00 a peice and a proper intake. He is just saying it may be worth a look

Yep, I understand. I'm just saying, my own opinion is that it's an idea that won't provide any gains over the optimized EFI by itself, and probably won't pick up gains over the $10,000 carburetor that's been optimized either. One thing I am learning about intake guys: they understand airflow. ;)

Still, like I said, bring me something to try it out on, if there's on thing I am learning lately, it's that basically NOBODY in this hobby can make generalizations that they haven't tested/proven.

[TheSilverBuick]

Re: EFI or Carb why not both ?

one thing a carbs got over efi is on the side of the road a flat blade screw driver and vise grips can get you back on the road

That's not true at all.

Any carb failure that requires parts, is going to result in "ordering parts" from the parts store - that stuff just isn't carried in stock anymore. Rebuild kits, gaskets, etc. are hard to come by in a store.

Meanwhile, every part of Randal's system under the hood: coolant temp sensor, MAP sensor, air temp sensor, and TPS sensor - all he really needs to run the engine - is found right now at a parts store for cheap. None of those parts is over $15 except a TPS, which might be $25.

This is an example of a preconceived notion that you have, that is inaccurate.

I run standard 32lb/hr injectors, easy to find at any parts store. My Ford high pressure fuel pump is common enough even the Ely parts store keeps one in stock. And as DG points out, all the sensor are available at any parts store, being a MegaSquirt, there isn't a specific application, and pigtails are usually available in the electrical section for any "brand" changes that may happen with the sensors. Though I can ignore one or two sensors if they went screwy with me, it'd just be a ding in mpg's and max HP, but managable, unplug the sensor and it just defaults to a constant number.

Try getting a Buick fuel pump, or Q-jet rebuild kit in a timely fashion these days, lots of times they are not next day items even if ordered in the morning. I built my system with as many common parts as possible, so I don't have to special order from Summit or TA Performance if I run into trouble 1,000 miles from home.

Hell, when I popped the head gaskets, or flattened the cam, I unplugged the fuel injector and spark plug to the effected cylinder(s) to eliminate backfiring and pressurizing the crankcase issues for drives well in excess of 100 miles from home. Try that with a carb and you'll just dump a bunch of fuel into the exhaust and crankcase. I've ran my Buick 160 miles with two injectors intentionally unplugged, 600 miles with one intentionally unplugged, and several miles with half the injectors unplugged (wire came out), and the car was still completely drivable at highway speeds and normal street driving acceleration rates. Of course, it is a Big Block so even a 50% power loss isn't detrimental :P

[dieselgeek]

Re: EFI or Carb why not both ?

Randal, how many miles of desert highway driving have you put on your megasquirt? about the only thing I'd do if I were you, is carry a spare megasquirt. WHich is a lot cheaper than carrying a spare carb. At that point you have no worries at all, IMO. I've carried spare megasquirts on Drag Week. I never needed one, but I did know a kid who fried one when he was removing a starter and shorted out the hot wire because he forgot to remove the battery ground... he fried his megasquirt, his entire dash/gauge package, an LC1 wideband, and the voltage regulator in his alternator. The spare MS wouldn't have gotten him home (he was in my garage when he did it) but you get the idea. You can kill one with a bad enough short to ground.

Now an EMS-pro - forgetabout it. You aren't killing one of those unless you are Jonny Huber with a Pressure Washer.