from efi to carb in two weeks, my experience

vector1 · #1 (**permalink**) 06-28-2009, 08:45 AM

well, actually, i played with the efi for 6+ mos. and couldn't get it to run to my satisfaction. accel gen 7 setup, so i gave up and put a carb on. chose a dui distributor so i could get away from the msd setup and use one wire to fire.

the rewire was more of a problem then i thought it would be and now know why i hate wiring, although it wasn't too bad considering i had made most of the wiring mistakes already.

the original hi pressure pump and lines were retained, i used a lighter spring in the regulator and still had to cut one coil off but the pressure is now a steady 7 lbs. or wherever i choose to set it.

the dui dist. is nice, one wire to the tach, one to the power, get it close and watch for fire out the carb--happened once, kind of an eye popper when that big flame roars up but luckily went out rather quickly. so just keep moving dist. til it fires and runs.

installed a wb o2 sensor setup from wideband commander that i had in the shop since i still had the bung in place, this is nice.

i started with a pro systems carb that had been built for a 375ci engine and it ran rather lean according to the o2 gauge, didn't know if the gauge was incorrect but couldn't really run it in this fashion, the idle was good at 13.5-1 but wot was up in the 15-1 range. the engine ran good though, no backfire or hisitation except off tip in sometimes. the accel pump was a little loose and wasn't getting the fuel to the inlet quick enough imo. if i hadn't had the o2 sensor things could have turned out bad some day.

in a moment of desperation i changed to a bg rr 750 and the car ran about the same, except the afr was in the correct range and didn't fluctuate through the rpm range as much as the pro systems. idle was rich at 12.5-1 but wot and everything else looked better. this morning i adjusted the carb per bg instructions and adjusted the idle screws in 1/4 turn and the afr went to 14.5-1 with just 1/4 turn, lots more sensitive then i thought they would be. with all the trash talking on bg carbs i was surprised at how well this carb performed. don't think i'll do the pro systems thing again, it's on a 351 crate motor now and still has some tuning that needs to be done.

i like the carb setup for now over the efi, car runs different, sounds different, and is easier to drive imo.

i think the sup vic manifold the efi setup uses is not suitable to rr lightweight cobras and is geared more toward the 1/4 wot high rpm crowd. the rpm air gap pulls much better throughout the rpm range. and really, don't think i lost anything power wise. also, imo, the accel is much too sensitive hardware/software wise for what i was trying to accomplish with my experience and knowledge.

DocDirk · #2 (**permalink**) 06-28-2009, 09:20 AM

Thanks for taking the trouble to outline the details of your conversion experience! I learned something as I often do in such Club Cobra posts - congrats on finding a combination that works well for you!

Dirk

kobrabytes · #3 (**permalink**) 06-28-2009, 10:23 AM

I hate to see you give up on your EFI. It takes a lot of patience.

When I first got my set up (TWM/FAST) it was in speed density. After the first summer and 6, or more, sets of plus I knew that I needed to understand the system better. The engine was running so rich that a typical drive would cost me a new set of plugs. Had lots of backfire... Hard starting.

This spring with the help of a really smart friend I moved to Alpha-N. (Actually against many peoples opinions. Telling me that Alpha-N is for the race track. Some even suggested completely staying away from injection.)

The program is nearly perfect. No backfire, no sensitivity to altitude, plugs don't foul, LOTS of power, fantastic idle and starting, and much improved gas mileage!!!

The initial change over was rough. I was discouraged at first by the lack of power. With my laptop sitting in the drivers seat I made dozens of logging runs. After each run I would sit down and replay what happened and make changes to the maps. Yesterday I took a run with the Cobra club on a road that went over 8000 ft, my performance was flawless. Ask anyone in the club if my car is fast...

I think the bottom line is that you need to learn everything you can about what you have. Take input from everyone, but weigh it carefully. Then actually get your hands dirty until you figure it out. I'm am happy that I kept trying. The end result is better than I could have imagined.

When I pop open the hood the stacks have an "oh SH!T" factor equal to none.

vector1 · #4 (**permalink**) 06-28-2009, 11:40 AM

kobrabytes

that is pretty much my experience, lots of laptop work and datalogging plus the added frustration of working out bugs in the system--my own created bugs plus stuff that accel was not doing correctly, which is more frustrating because the system is supposed to have already gone through beta testing, or so one would think.

glad to see you got yours running well. i don't see too many cheering posts on efi, seems most of it turns out "good enough", and i think that is pretty much the majority with anything anymore.

jdean is putting a powerjection setup on his, will be interesting to see how it turns out, haven't read too many glowing reports on the other cobra site except from the ones selling it.

an aside, the car tries to stall now with leaner idle mixture, so i am going to adjust the rear idle adjustment screws back to where they were at 12.5-1 afr, and leave the front ones at 14.5-1 since they are the ones uncovered under decel. and don't contribute any fuel, maybe i'll end up with 13.5-1.

kobrabytes · #5 (**permalink**) 06-28-2009, 06:36 PM

I have my A/F between 12.8 and 13.9. (WOT/Idle)

When I did logging runs I tried to do smooth long passes at a given rpm. The quick on and off throttle periods make it difficult to see where you need to be. I don't think that the 02 sensor tracks accurately with rapid changes. Once I got the A/F correction within reasonable limits, and no obvious holes, I started adding fuel to the accelerator functions until I eliminated the bog.

I probably spent a lot more time than I needed too. (Than if I would have had access to a dyno.) On a dyno I could have peaked the power through all the rpm ranges. Right now I'm guessing on the A/F, but have it close enough to scare the HE!! out of me...

Good luck on your new direction.

www.kobrabytes.com (Pictures of my setup.)

len

vector1 · #6 (**permalink**) 07-01-2009, 06:41 PM

after a couple outings and no tickets i still have the bg 750rr unit on. called bg tech and told them my lean condition and they suggested going from 75/75 to 80/80 on the jets, there are pv's front and back. i ended up trying 80/83 which was too rich then 80/81 and all looked good til the upper rpm range when it started to lean out. i was tooling up a grade in 3rd with the hammer down and think i might have uncovered the rear pv, so i'm going to plug it and go to a 80/87 split as someone suggested and see what happens.

the experience of acceleration and just waiting for the rear to break loose........ah yes.

vector1 · #7 (**permalink**) 07-03-2009, 06:13 AM

ended up with square jetting 80 all around, linkage is 1-1 so i don't think i could plug rear pv without giving something up. raised float levels and everything is good. 13-1 or less on wot runs.

mdross1 · #8 (**permalink**) 01-12-2010, 07:50 AM

I built a car years ago and set it up with EFI.Enjoyed playing with it but could never get the performance I was after.Finally gave up and went to a Holley dbl pmp dailed it in and never looked back.It gives me everything I hoped for and is so much easier to work with,not to mention,the engine idling is music to my ears.Oh how I yearn for that big cammed sound,Carburated!!

captjohn · #9 (**permalink**) 02-23-2010, 02:05 PM

I am looking into an 8 stack EFI system and found a new controller offered by FAST. The new EZ-EFI controller self calibrates after answering a few simple questions on the handheld module. I spoke with a rep and he stated it will work with virtually any 8 stack system. They even offer a dual quad kit. I'll most likely go this route...no laptop or techs required.

olddog · #10 (**permalink**) 02-26-2010, 04:27 PM

Quote:

Originally Posted by captjohn

I am looking into an 8 stack EFI system and found a new controller offered by FAST. The new EZ-EFI controller self calibrates after answering a few simple questions on the handheld module. I spoke with a rep and he stated it will work with virtually any 8 stack system. They even offer a dual quad kit. I'll most likely go this route...no laptop or techs required.

I'm a show me type of guy. I trust salesmen about as much as politicians. I cannot think of a single time anything ever worked as good or as easy as a salesman told me it would. I can think of dozens of times it was a flat out hunk of junk.

I feel a mass flow EFI has a better chance at plug and play than speed density does. When you get to high overlap cams, where the vacuum at idle is lower than it is at say 2000 rpm, speed density doesn't have a chance. Alpha n (think that is the term) is used, which is based off of throttle position.

The more stock an engine is, the better chance these self tuning systems will work. The more modified the engine, the less likely this is going to work.

Maybe I'm living in the past. I just don't buy it. I've seen videos of some set ups, but the engines were all mild. They never show you the AFR on the dyno. You never know how many hours was edited out. I'm still not a believer.