My mind is wandering - port vs throttle body EFI

[Yellow Truck]

With the better half out of commission (triple bypass coming up next week) I'm not spending much time on the truck, so instead my mind is wandering. Turbohunter triggered this bit of speculation with his post about EFI.

I have a QFT SS 830 on a Street Dominator. Changing to EFI has been something I toyed with but never really started to break it down into decisions. The main one is port vs throttle body. I understand that port is more precise, but it requires a new manifold. Going with the current manifold means limiting the benefit. Question is - how much.

On a 445 with a hydraulic roller cam (details below) how much would I give up by staying with the current intake and using a throttle body EFI? I also note that there are traditional intake options from Edelbrock or FAST, but Trick Flow have their "R Series" intake for the Cleveland that I assume would work with Jay's adapter.

I assume runner length is less of an issue in a port injection setup since fuel atomization and precipitation is taken out of the picture.

Also thinking about "self learning" (I have big doubts) vs programmed options. Main benefits of injection over carberation   seem to be in driving characteristics and ease of tuning (tuning is largely done without removing any parts).

http://i1135.photobucket.com/albums/m637/410dyno/Cam%20Card.jpg

[Yellow Truck]

60 views and not one opinion? Must have been a really stupid question.

[jayb]

Nope, its a good question.  The advantage of a port injection setup is that you take variations in the intake out of the equation.  So, if you inject up at the carb the fuel has to be distributed through the intake, and most intakes will not give you even fuel distribution from cylinder to cylinder.  On the other hand, with a port injection setup you do get even distribution, because of where the fuel is injected.  Also a port injected system can be set up as a fully sequential system, which makes for better characteristics all around.

I was at a big car show this past weekend, talking to lots of people about my products, and I had one guy come up and complain about that Fitech self-learning system.  He can't get the engine to run as well as it did on a carb with the Fitech EFI.  He said it starts easier and idles nice, but the performance is way down compared to a carb.  He was pretty disappointed.  Also a local friend of mine came up and was having some issues, he thinks, with a Holley Sniper system.  Its a shame that has to happen because with EFI everything should be better than it is with a carb, given the same intake manifold.  Its seems that the self-learning systems work great for some people, but not for others, kind of a crap shoot. 

If you want to be sure you can make your EFI system work with your combination, get a real EFI system that is fully tunable.

[unclewill]

IMO, the choice is dictated by what you want to do with the car/truck.  If you are trying to beat the guy next to you by a hair to make the next round, the more expensive and fiddly port injected EFI is probably the best bet.  If you want a fun street driver with lots of reliable power, the self learning throttle body system is likely fine. 
I like the FiTech EFI on my street car because I want to run the Edelbrock Performer intake and I'm tired of tuning carbs.  Am I giving up 20hp?  I don't know...the unit has 8 injectors and can support 800hp according to FiTech.  Do I care?  Not really, it's not a race car and the 482 makes way more power than I can use on the street.  What I like is the smooth idle, cool running, driveability and the peace of mind knowing I won't be running lean and burning a hole in a piston.  Also, hopefully, long term durability...

[Drew Pojedinec]

I'm anti-wires..... so didn't feel like responding.
^there, I responded.

My stance on fuel injection in a naturally aspirated engine is "Why the heck would you want to do that?"
If someone thinks having a system with 8 injectors is going to make them less likely to "burn a hole in a piston" than having a carburetor..... uhhh well.....  Good luck.

[My427stang]

So, it's all about the ability to tune it.

Self tuning is a real good thing, but, it should be considered as an "self-adjustment to a good tune" not "the creation of the tune"

That is where some of these TB systems have issues, you just don't have the ability to create a good base tune with 4-5 questions.  As Jay said, taking fuel distribution issues out by using port injection is a very good thing, but I have a hunch that 4 properly size injectors in a TB, combined with ignition control, would still do real well if driven by a Megasquirt or some other system that would allow more manipulation and the ability to learn (and the ability to prevent learning in some conditions)

The other thing I will bring up is, a guy who loves his carb usually doesn't go EFI. So guys who are replacing a "carb that can't be tuned" may not be too happy with a TB system either, one because if you can't tune a carb, you can't tune EFI (insert tuna fish joke here)  but also because often the carb issue is not because of the carb, so the EFI likely can't fix it.

As far your application, it's pretty expensive to set up to port injection compared to a cheap TB system, it depends if you think the truck is worth it.  I have used many different setups, and I think if I go EFI on my truck, I will use a Megasquirt to drive a TB, I have even considered a EEC-IV speed density system off a 4 cylinder because I know this insides of that program.  In either case, less benefit than a port injection, but more control than an out of the box TB. 

FYI - The MOST controllable cheap TB system I have installed and tuned is the Professional Products Powerjection, but the hardware itself is crappy, so what you get for a computer based ability to tune, you lose in junky parts.

[My427stang]

I'm anti-wires..... so didn't feel like responding.
^there, I responded.

My stance on fuel injection in a naturally aspirated engine is "Why the heck would you want to do that?"
If someone thinks having a system with 8 injectors is going to make them less likely to "burn a hole in a piston" than having a carburetor..... uhhh well.....  Good luck.

No doubt, but you are a sharp carb guy too.  Once you got into it, you'd dig it.

I will say, the reason I swapped - cold start and cold drive, taming idle, mpg, low rpm torque (part throttle especially), high pressure fuel system without a potential for vapor lock or fuel boil, and timing control.

[Drew Pojedinec]

I'm sure I would love messing with it..... if there was a direct injection head available for an FE I'd probably want to play with it.
If I was really into turbo's even port injection would certainly get my attention....


Your statement of:
"So guys who are replacing a "carb that can't be tuned" may not be too happy with a TB system either, one because if you can't tune a carb, you can't tune EFI"

Sums up my view in a very brief and accurate way.

[Yellow Truck]

Drew - I respect your advice and have followed it, and Ross, I believe you to be correct that the carb is often not the issue. I do think that carb adjustment is a skill not easily learned. At the moment I'm frustrated that I don't have the time to experiment with it, and some of my local "advisors" are all convinced that the carb I have is too much.

I just don't have the time to mess with it and try and get it right. I did want a carb, it fits with the old school nature of the truck. What might take some of you an hour will take me weeks of trial and error.

As I write this I'm on hold with MSD to ask them if they will be returning my distributor.

[unclewill]

The "self learning" EFI starts with a too rich base map for safety and leans itself out through time.  The FiTech computer allows for fine tuning for most parameters - I suspect most TBI retrofit systems offer the same.
Anyone who is unclear on why EFI trumps a carb on ANY engine needs only to drive their vehicle from sea level to 8000' of elevation without opening the hood.

[Drew Pojedinec]

When was the last time you drove from Sea Level to 8,000ft?
I rarely ever drive more than 300miles from here, which is maybe 600ft of elevation change max.  I suspect FI would make more sense if I lived out west.

For the record, I couldn't care how you power the engine.  I just see a ton of people (on facebook FE groups mostly) who think that instead of learning how to tune an engine they can buy FItech, and well..... they end up spending a pile of cash and still have to learn how to tune an engine, all for a car that drives maybe 40 miles a week.

[Yellow Truck]

0 to 8,000, nope, but 3,600 to 7,500 to 0 and back, yes. Was driving an injected 5.3 GM in a van pulling a trailer. While I didn't have to make any adjustments it sure lacked punch at 7,500.

I'm early in my discovery of carberation, and there is a lot of "advice" out there, but it seems that learning how to get ideal fuel delivery out of a carb requires a lot of knowledge and practice, and few so called experts really have it. I think the reason FI is preferred by many is that the relationship between what you do and the result is more direct and understandable. On a carb you can get the result, but the things you need to understand and do are really indirect.

The shop where I'm getting my exhaust work done also does a lot of performance work - admittedly not on FEs as they are a bit obscure - and their reaction was an 830 was too much carb for a 445 making 500ish HP and FT-LBS. He though a 600 would be closer. He has done a lot of carbs, but it doesn't mean he really understands them.

Reading Visard's book is a good indication of how much you need to learn and practice. By comparison FI is very linear and simple. Having said that I really want to run a carb for now and may decide to try it with FI down the road.

[TomP]

How about from zero altitude, cold ocean breeze and corrects to way below sea level and in a couple hours of driving getting to over 10,000 ft corrected, 7500ft actual altitude and over 100 degrees. There are places on the west coast you can do that and even late model factory EFI systems can struggle with that.

[RJP]

The "self learning" EFI starts with a too rich base map for safety and leans itself out through time.  The FiTech computer allows for fine tuning for most parameters - I suspect most TBI retrofit systems offer the same.
Anyone who is unclear on why EFI trumps a carb on ANY engine needs only to drive their vehicle from sea level to 8000' of elevation without opening the hood.

So whats the problem with carbs at altitude? Jet change? Power valve change? Your statement is simply untrue. No hood needs to be lifted with a carb equipped car to correct for altitude. I have made countless trips over Tioga Pass, Ca. [alt. 9945'] in 3 different carb equipped cars and not once did I need to lift the hood to adjust for altitude. All 3 cars have 3310/780 Holleys and ran just fine. No puking black smoke, no loading up, no stumbling or flat spots, all ran fine. A carb will respond in kind to atmosphere or lack of as fuel delivery is directly related to the amount of air flowing thru the carb. Less air...less fuel, its that simple.

[Drew Pojedinec]

Cool Tom and Paul.
I'm unaware of the challenges of driving out west with my own cars.
I recall as a kid driving around out west up in the mountains and down to the Mexican border and don't recall any issues, but that was a long time ago.