billla

What was missing in terms of the test being complete and deep?

It wasn't an engineering study, but I thought it was a pretty decent set of test scenarios.

Golden

I can't believe how stuck in the 70's a few of you guys are.

In Europe people would laugh themselves stupid at the idea that a carb is better than EFI.

The only race cars here that still use carbs run in controlled historic racing categories, even the lowest of amateur racers go for EFI.

I do accept that for many people a $300 carb is much better value than a $1500 EFI system but to say a carb can out perform an EFI setup is like suggesting an abacus can be as fast as a computer.

billla

Some of the challenges here are defining performance and recognizing that things have changed dramatically fairly recently.

Carbs still sometimes show slightly higher peak HP on the dyno. If this is the definition of "perfomance" for someone, then they see things differently. Factor in throttle response, driveability, fuel economy AND peak power and EFI clearly wins.

Price/Performance is also a tough call right now. Carbs is cheap, and if well-tuned pretty decent

Finally, the very latest generation of mass airflow-type EFI systems is a total game-changer. I've worked with some of the older stuff from Edelbrock, Holley and GMPP...and although it worked, it wasn't great for power or economy - and it was persnickety to set up and tune.

So, the times they are a changin' and I do think people need to look at what's happening right now and build some awareness of the latest generation of this stuff...

gerry72

No one is saying that. Language differences aside, it's quite clear no one is pronouncing the superiority of a carburetor as a fuel delivery device. It's quite the opposite. The only point of the thread was a carburetor "can" make more peak power than EFI, but we don't drive our cars full-throttle all the time nor do we all have perfectly tuned carburetors so that minor difference becomes irrelevant and nothing more than a topic to discuss. Let us know how all of Europe feels about that.

billla

I don't know that this statement reflects all thread participant's viewpoints.

Otherwise, with your comments.

not a '76

I didn't read the article, but if the EFI doesn't include at least a knock sensor, wide band oxygen sensor, the ability to learn/be programmed, and some learning time, then the comparison is a wash.

The EFI should also be some sort of port injection with a completely different intake manifold design.

Most of what we consider a 'good' intake is basically just compensating for the limitations of a carburator.

Golden

How many times do I have to say it, if EFI makes less peak HP than a carb it's either an incorrectly selected system or it isn't set up properly.

WOT is possible the easiest fuelling area to set up, it's the transitional set up on both carbs and EFI that's tough.

A carb is never going to be a match for EFI, as the fuel air mix in a carb is governed by the ever changing pressures and airflows within the intake. The fact that an EFI system sprays a perfect mist in the manifold, regardless of manifold pressure, reversion waves, cylinder robbing and all the other things that effect venturi pressure, make it head and shoulders above a carb.

I think too many people still see EFI as the same half cocked rubbish GM put on in the 80's.

Golden

So true.

roscobbc

My vote is with Kinsler

tt 383

The test in question uses a 750 carb for a 420 hp engine, wouldnt a 650 be a much better carb for said engine?

Golden, since there are so many great kits in the UK that work so much better than carbs maybe you can post a few links where back to back test were done and the affordable/ easy to tune EFI makes more peak? Seems to me on the many forums I visit that a few of the builders experience a common scenario where EFI is to be used and the tech achieves less in two days dyno time than by the builder bolting on a carb and crap design intake to make more power in a few pulls. EMC this year had very bad air, the test is average power over 4000rpm pull. These are 2 elements that mount in the EFI camps favor. A good setup carb will get good mpg, it will accommodate big changes in weather, and in WOT it will make more power than a cheap/production EFI system. How many high end EFI systems in road course or timed events (ALMS, CART,F1,ROLEX SERIES) actually run the processor/sensors instead of a map that somebody programmed? Seems redundant to me to pay so much for something just to program how its gonna run with multiple fuel maps. EFI biggest advantage is that its a pressurized system. No matter how you look at it a carb works off of real time, not so with EFI........ Troy Patterson put it this way on speedtalk, look at a leaf blowing in the wind and how it responds(like a carb) and then try to use sensors and controllers to make it move the same way in the same time frame(like EFI), or something like that.

MotorHead

100% and the big problem is not many know how to setup a carb correctly ( and I am not saying I do either ). When done so it performs much better than many think

tt 383

Reversion waves and cylinder robbing are a manifold design problem not a carb issue. If you have a poorly designed manifold Carb or EFI it will not work properly anyway..... I would assume why race pieces with no package requirement use either a Tunnel Ram, or IR setup.

Golden

I'll try and answer your questions.

I can't link you to any back to back tests as no serious tuner has used a carb here since the mid 90's.

I think this is maybe a cultural thing where the US is behind the times in it's use of EFI. Many of the guys here do their own mapping and our Dyno guys are far more used to setting up EFI from scratch and can often get a MAP set up in maybe half a day to a day.

A carburettor may run acceptably in many conditions and return acceptable MPG but will never match EFI that can make allowances for air temp, air density and fuel quality. It will only make more peak HP if it replaces a conservative factory EFI system or if the EFI system isn't optimized.

I'm not sure you fully understand how modern EFI works. All EFI systems run a pre programmed map, the sensors are there to make sure the right part of the map is used dependant on the information returned by the engine sensors.

Troy Patterson wants to sell carburettors. His leaf analogy is exactly why a carb can't compete with EFI.

A carb relies on a vacuum 'signal' at the venturi to try and match a flow of fuel to what it perceives as a certain amount of air going in. This airflow is constantly disturbed by factors created by the engine, reversion pulses, valve overlap, cylinder robbing, inconstant manifold temperature, the list goes on and on. EFI ignores all of those factors and delivers the correct amount fuel regardless of airflow disturbances in the manifold. An EFI system can calculate how much fuel an engine requires thousands of times a second, more than fast enough to keep up with changes in load and revs.

Bullshark

Golden, As I read the posts on this thread, it is ridiculous to categorize the US as a country, group, or culture of people who think an old analog fuel control system (carburetor) can equal or come anywhere close to the capability of today's highly sophisticated digital control systems (todays EFI systems). All I can do is throw up my hands and say, please guys, talk to people who really know wtf they are talking about. We are designing digital autopilots that guide a 2000 lb brick (bomb) to within a meter of its target. We don't do that with an analog/mechanical control system. I would be laughed out the door if I even suggested it. Trying to debate this issue with people who have never been educated in control theory is like Don Quixote jousting the windmill. Futile, It has everything to do with knowledge. Don't take me wrong, we all take a position based on our experience and what we know but smart people defer to experts in the field. Today's experts wouldn't give a carburetor a nano second of thought as an option for optimizing an engine for performance. Peak HP or otherwise.

Bullshark

tt 383

So in your world where for 20 years carbs don't get used, you determine that efi must be superior? Yet in that admission, you have no real real proof in the form of data because no one uses them? Please maybe you can enlighten everyone as to what exactly goes on at WOT in an EFI system? What part of the system do closed loop sensors control at that point? Some systems the MAP doesn't even read, relies purely on throttle position. I still dont understand how a sensor reading what goes on in the intake is doing anything different than a carb? It still reads the same air reversions and cylinder robbing, but in past tense it makes its adjustments. Venturi does nothing more than magnify the signal at the booster, to get an accurate reading. You make it sound like a carb has no atmospheric compensation in it at all, thats just not true. Troy Patterson clearly hasn't accomplished with carbs what you have with efi, but thats another thread in itself.....

roscobbc

The real issue with 'proper' good quality MPFI is the cost of it - especially here in the UK (if you are injecting USA engines) a fully mapped individual runner Kinsler system would cost me more than my recent BBC engine build-up. Unless you are driving many thousands of miles per year (and not too many of us doing that in our 'fun' car just now with the current economic climate) then the mpg improvements just don't pay for themselves - EVER. Performance benefits - questionable again.

Bee Jay

I was a big Q-jet fan. Read everything by Lars and Ruggles. I had Brad Urban modify my Q-jet. Then I bolted on a very basic Holley Throttle Body Injection. The driveability and throttle response is phenomenal and the gas mileage ain't bad. I'll never go back to carbs.

Bee Jay

Golden

I'm really sorry if I came across like that, I didn't mean to sound like I was lumping the entire continent in together. It's clear from this thread and others, that there are many US Vette owners who either through their thirst for knowledge or desire for maximum performance are fully aware of the benefits of EFI.


All of the items mentioned above are not 'manifold design issues' they are naturally occurring side effects of the internal combustion engine. Engine design can try to minimize or move these items within the engines working range but you can't get rid of them. A map sensor doesn't suffer from these in the same way as a carb because it is not reading in a turbulent area in a constant state of flux. It reads a smoothed real time manifold vacuum.

Those are the facts I'm afraid. One of the big differences in EFI development between European and US designs is that we went straight to multipoint port injection. In the US many designers stayed with, and still do, throttle body injection. We call it single point injection and no tuner (professional or DIY) gives it the time of day. It's seen as a cheap economy design not worth tuning.



You still seem to think that EFI only has two modes, 'open' or 'closed'. Open and closed only refers to lambda control. On some systems at WOT lambda correction is turned off in favour of a pre-programmed fuelling map. This is because it's assumed that if a driver has floored it they want performance rather than economy and it's safer to run the engine on a richer A/F ratio. The reason for dropping lambda control is that older narrow band oxygen sensors couldn't accurately read past a certain rich A/F ratio. Now many systems can run permanently closed loop because they run wide band lambda sensors.



Whether a system runs open or closed loop, you seem to think that in open loop it becomes a static mechanical system. It's only lambda control that's not used. Fuelling is still corrected for manifold pressure (load), intake air temperature and engine temperature. Additionally on some systems/engines fuelling and ignition are corrected for knock and in some cases with sequential injector firing and multiple lambda sensors, individually corrected per bank/cylinder.

This is called Alpha N, it's used when there is insufficient or too narrow a vacuum signal from the engine. This is not a failing or work-around, it's the use of throttle position as an input that allows the use of high lift/overlap cams on street engines. Everyone has seen a car with a very hot cam on a carb, you either have an idle speed of 1200rpm or the engine jumps around like it's trying to leave the engine bay. Alpha N injection is why these days you can run near race cams on the road and sometimes even squeak past emission limits.

Please see paragraph 4.


A carb has no compensation for engine temperature, air temperature, altitude or O2 feedback.

I'm sure Mr Patterson knows his stuff and is an excellent carb builder, but to me there are only two reasons to keep a carburettor. Originality and cost, if your carb starts to cost the same as EFI you're throwing money down the drain.

Bullshark

Golden. good job. You get the Don Quixote award for your persistence. BTW, Carbs can't tune fuel to the individual cylinder like todays MPEFI. That alone offers a degree of optimization at WOT over TBI / Carb. It's not a large number but it is real and measurable. I have seen the evidence on an engine dyno.

billla

Not to go OT, but this is a great book for understanding EFI on a broad level as well as specific to the Corvette.

http://www.amazon.com/Corvette-Injec...0636445&sr=8-1