Discussion Forum - Northstar Chevelle Club

gearlube · Active Member

Quick Fuel QFI is finally Out!

Dan Williams · Active Member

So Tom, what is the advantage of the Quick Fuel over the Holley Terminator that I have sitting here ready to go on. It looks an awful lot alike (even got mine in black). Will run my fans, atomizes from under the throttle plates, self learning ecu, about the same money. etc etc. They compare pretty much apple for apple from what I have read and seen. Don't tell me I screwed up or I will come looking for you and whine!

gearlube · Active Member

Lol Dan. I am no expert by any means. I have been running Quick Fuel for a long time and have had good luck. So when they came out with their EFI I wanted to check it out. I think you really can't go wrong with these.

Scott Parkhurst · Super Poster

The racers used to prefer the port injection setups due to superior distribution- each cylinder would get its share with the injectors mounted in the ports. But the increased distance from the valve gives the throttle body setups (and carbs) better atomization (smaller fuel droplets, which burn more efficiently) compared to the port design. Depending on a slew of other factors like intake manifold design, the cam specs and more (target rpm range, vacuum levels, and even exhaust efficiency) there might be some potential gains based on where the throttle body actually injects the fuel...but it would require back-to-back testing to determine any advantages on a given setup. Any gains would be minor, since the 2 systems are truly very similar overall.

The hardest thing for any engine to do is idle. It might not seem like it, but it's true. The high vacuum condition means the engine is craving more air, fuel and rpm. Guys tune at wide open throttle, which eliminates a lot of the mechanical restrictions and challenges that come with them...which is why these new self-tuning/ learning systems are so cool. They work on the inevitable compromises that challenge even the most talented EFI programmers at part throttle, low load, and idle.

I've learned over the years that if an engine can idle steadily with a minimum of issues, the odds are very strong it will work well throughout the rpm range. If all the idle and low rpm performance issues have been addressed (like stumbles on tip-in, over-rich idle, loading up, and even overheating), higher rpm WOT performance is almost assured. Most of us know what max timing should be (and 36 is always a good place to start) but when the curve isn't controlled mechanically and can be programmed anywhere, it takes time, talent and good data/instruments to maximize efficiency all the way from 750 rpm to redline at 6500 (or more).

What fascinates me is how good carbs are, when they are fully tuned. But EFI can be a lot better in those critical low rpm ranges if it's dialed in right. Testing has shown that peak hp doesn't change much between carbs and EFI...if the engine is getting all the air and fuel it can take in the right proportions, the delivery system is less relevant. It's at the lower levels EFI can really flex it's electronic muscles...if the tune is dead on!

gearlube · Active Member

Scott this is excellent information. I really enjoyed reading this. I am still educating myself on the whole subject. When I talked at length with the Quickfuel engineers they realized the advantages of the place for fuel delivery even through the throttle body. But it seemed to make sense when they explained. If my car was numbers matching or stock I wouldn't do this. My carb is dialed in right now and the car runs well. Craig S. Advised me to make sure it is dialed in because an EFI does not fix issues with timing etc. I still think I am going to keep my MSD7 box to work with my distributor And not have the EFI control the timing. I have had really good luck with it. But I a still on the fence there. What attracted me to EFI was the throttle response. I drive 0-60. Or stop light racing. I have a lot of torque and want to use it.

-- Edited by gearlube on Friday 4th of April 2014 06:45:05 PM

bowtie · Secretary

gearlube wrote:
...EFI does not fix issues with timing etc..

-- Edited by gearlube on Friday 4th of April 2014 06:45:05 PM

100% true.

A fairly simple mechanical timing change (small but steady increase at measured intervals) on an otherwise good tune gave me a little over 40hp at the tires as measured on the dyno.

Enganeer · Mega Poster

I sure your MSD7 box gives you far more control than the standard HEI setup but do you have full control over the all the ignition aspects? A system that controls the complete picture tends perform the best.

I swapped out my old school HEI to the a small body computer controlled for the Holley EFI conversion and it made things so much more controllable in all aspects. I can select the initial timing, idle timing at a specific rpm I want to idle at (can use the MAP sensor for feedback for amount of vacuum) for the smoothest idle, tailor the timing curve to what ever I want. Even connect knock sensors in case you need to pull some timing out if needed to protect the engine.

But for those with just an HEI and doing an EFI conversion, I recommend having the computer control distributor setup. With regular HEI setup of a vacuum advance / mechanical distributor, you sorta limited how much you can tweak...you have to start with a set initial timing, which vacuum can for the advance curve coupled with the springs you use for mechanical timing.

Nothing wrong if the setup you have is working great...you just might be leaving some on the table when said and done.

-- Edited by Enganeer on Saturday 5th of April 2014 09:05:34 AM

Dave Seitz · Mega Poster

When my engine was on the dyno Ron at R&R kept commenting about how great the throttle response was and after 3hrs of tuning we remembered to check the timing. Funny thing was it was set at 32 and that was optimal for the engine. Now I just need a car to throw the engine in.