Knebel
Senior Member
i dont have a single open plenum intake. I just heared that those are better for efi. The fitech dumps the fuel above the plates through some swirl pattern annular thing. I believe I heared that they flow 800cfm or so.
Backfire through intake/ stall on acceleration
- Thread starter Knebel
- Start date
In one respect, I don't see the real issue with single-plane or dual-plane intakes making much difference with EFI of any kind. It doesn't seem to with carbs and all the latest EFIs are are carbs with fuel injectors for each throttle bore rather than having a float bowl to pull fuel out of via air velocity through a venturi. Even if it's an annular discharge version.
The whole reason behind the first single-plane Edlebrock Tarantula intakes was more even air flow to each cylinder. Pull from a common plenum area with a more direct route to the intake valve. Of course, with the shorter runners, they "tune" at a higher rpm than the longer runners of the dual-plane intake. So, in that respect, more equal cylinder a/f distribution, a single-plane might be better.
The Holley Z-Line intake was a single plant intake, but with a full plenum divider and the "resonating port" which connected #7 and #8, so #8 could also pull from "7 in order to compensate for #5 firing right before #7, using the same corner of the plenum. Again, so each cylinder would get closer to the same amount of a/f mixture on each intake stroke.
To me, it's the efficiency of the fuel/air mixing above the plenum that makes for power and economy of operation. If that happens with a carb or otherwise, the "wet flow" manifold will get the a/f mixture to the intake valve.
We tend to know how big of a carb works for what size and type of motor, but with EFI, we might tend to go ga-ga over "lbs/hr" of fuel and how many horses that'll feed. The earlier 4bbl EFIs were all usually about 900-1000cfm flow capacity. Who'd buy a carb that big for a generally street or HP-street motor? But that's just me. Seems like somebody has a 750cfm Self-Learn 4bbl EFI? Annular discharge venturis? Seems like I saw that somewhere a year or so ago?
The MPI kits have been around for a long time. Expensive. But that expense now seems a little better if you consider how much easier they might be to make happen than the latest Self-learn EFIs seem to be.
Seems like Electromotive was one of the first to combine EFI and timing control? Pricey, so many "normal" hot rodders didn't seem to worry about it.
So . . . guess I need to do more research before I spent that much money on EFI!
Take care,
CBODY67
The whole reason behind the first single-plane Edlebrock Tarantula intakes was more even air flow to each cylinder. Pull from a common plenum area with a more direct route to the intake valve. Of course, with the shorter runners, they "tune" at a higher rpm than the longer runners of the dual-plane intake. So, in that respect, more equal cylinder a/f distribution, a single-plane might be better.
The Holley Z-Line intake was a single plant intake, but with a full plenum divider and the "resonating port" which connected #7 and #8, so #8 could also pull from "7 in order to compensate for #5 firing right before #7, using the same corner of the plenum. Again, so each cylinder would get closer to the same amount of a/f mixture on each intake stroke.
To me, it's the efficiency of the fuel/air mixing above the plenum that makes for power and economy of operation. If that happens with a carb or otherwise, the "wet flow" manifold will get the a/f mixture to the intake valve.
We tend to know how big of a carb works for what size and type of motor, but with EFI, we might tend to go ga-ga over "lbs/hr" of fuel and how many horses that'll feed. The earlier 4bbl EFIs were all usually about 900-1000cfm flow capacity. Who'd buy a carb that big for a generally street or HP-street motor? But that's just me. Seems like somebody has a 750cfm Self-Learn 4bbl EFI? Annular discharge venturis? Seems like I saw that somewhere a year or so ago?
The MPI kits have been around for a long time. Expensive. But that expense now seems a little better if you consider how much easier they might be to make happen than the latest Self-learn EFIs seem to be.
Seems like Electromotive was one of the first to combine EFI and timing control? Pricey, so many "normal" hot rodders didn't seem to worry about it.
So . . . guess I need to do more research before I spent that much money on EFI!
Take care,
CBODY67
Knebel
Senior Member
Okay so I had a holley street avenger 650cfm that i installed some annular discharge boosters myself. tuned to same afr values as with the dogleg booster and my mpg increased from 8 to 11!!! that was incredible. So I did expect at least 14mpg with the efi. And now mind you thats all city driving. Not going down to less that what the holley initially returned in economy. That made me real mad that I did that switch. I also didnt want to fiddle with idle mixture 5 times a year here/every other day when the weather changes and what did it get? i fiddeled more with the efi than I had ever imagined just getting it to run "okay". Its a bunch of crap and if i dont get this sorted out til end of the year I will buy a carb again.
Knebel
Senior Member
this specific efi has a 30° range of capable timing. I am not sure why so "little" but in order to archive 60° cruise I'd need to have 30° base timing. That is impossible! i can get to 44...46 or so at cruise!
It can only dial back 30*?
I only use about 50-52* but I put it in 60 so I'd have plenty of room. The computer can pull timing back it can't magically advance it. Mine can pull back whatever, you just have to tell it where you stabbed it in at so it can do the math.
If your system is really limited to that I think it forces you to run a conventional dizzy in a street car.
I only use about 50-52* but I put it in 60 so I'd have plenty of room. The computer can pull timing back it can't magically advance it. Mine can pull back whatever, you just have to tell it where you stabbed it in at so it can do the math.
If your system is really limited to that I think it forces you to run a conventional dizzy in a street car.
70bigblockdodge
Old Man with a Hat
Knebel, what is your vacuum at idle?
Does your car have a fairly rough idle?
I have heard that there are basic parameters you put in so it can have a base map to start with. I have heard that some pick a aggressive cam profile base map, from sound or specs, and if you choose a less aggressive base map it actually ends up liking it better. Just a thought rattaling around in my head.
If that makes sense.
Does your car have a fairly rough idle?
I have heard that there are basic parameters you put in so it can have a base map to start with. I have heard that some pick a aggressive cam profile base map, from sound or specs, and if you choose a less aggressive base map it actually ends up liking it better. Just a thought rattaling around in my head.
If that makes sense.
Knebel
Senior Member
I wouldn't call that rough but there is some sort of miss happening i can hear at the exhaust!
I hit about 11"HG in park, maybe 11.5. In drive I have about 9-10"Hg. You are correct with the cam selectiins, there is 1-4 (mild to wild)
No it does not retard the timing. you have to tell it where you stab the distributor and from there it can advance 30°. It can't retard, so if i stab it at 20° ...my idle timing then can't be lower than said 20°. This would then also be the timing advance it cranks with. I stabbed it at 10°. I guess i could do 15° since i idle at 18°
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