Moparts Tech Archive

Fuel System

EFI & TBI Systems Q's

Jerry
Moparts Member
Posts: 1961
From: WARREN, MI
Registered: Nov 1999
posted 10-02-2002 09:40 AM

looking for the best single plane intake to convert to efi. or is a tunnelram better? this will be a batch fire efi system witha later upgrade to sequential fire efi on a hilborn mech individual runner intake. but back on topic which intake would be the best to convert? and why.

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wayne_township
Moparts Member
Posts: 3510
From: Rural Eastern, IA USA Baby! Or is it the NW burbs of chicago today?
Registered: Dec 1999
posted 10-02-2002 09:42 AM

booster has some interesting notes on his intake choices over the yrs on his 340, a single plane isn't necessarily the best choice.

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Jerry
Moparts Member
Posts: 1961
From: WARREN, MI
Registered: Nov 1999
posted 10-02-2002 10:30 AM

why is a single plane not a good choice. i thought they had better equalization to the ports when running mfi. if i was running tbi then i think i would use a dual plane.

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booster
Moparts Member
Posts: 1222
From: Minnesota
Registered: Mar 2000
posted 10-02-2002 10:36 AM

My preferences lean very heavily toward running whatever you would with a carb, based on the application. If a dual plane, such as a Performer RPM, would be your choice with a carb, I would use it for EFI. If the application is such that a tunnel ram would be best (very high output, rpm) I would use the tunnel ram. The testing I have done on the 340 showed that the single planes / dual plane issues that show up with carbs also show up in the EFI, only in a slightly different way.
What I found on the TT340, low rpm, 8 to 1, turbo motor was:

Best overall power was the street Dominator single plane by a small amount over the M1 dual plane. Downside was fouled plugs, bad mixture, bad mileage at cruise.

Best mixture balance, mileage, no fouled plugs was the M1 dual plane and Performer (standard).

The performer was a bit small for the heads and didn't do well on top.

A Weiand dual plane, which has poorly matched runners, worked well on top and poorly everywhere else, and had the worst mixture distribution of any of the manifolds.

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Jerry
Moparts Member
Posts: 1961
From: WARREN, MI
Registered: Nov 1999
posted 10-02-2002 10:41 AM

well this engine is a 10.5:1 compression 440 which will soon get a hyd roller cam. also has edelbrock heads and is currently running a m1 single plane.

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booster
Moparts Member
Posts: 1222
From: Minnesota
Registered: Mar 2000
posted 10-02-2002 10:49 AM

I am not a BB guy so I can't have much opinion on what would match your combo. What would everybody else run on a setup like this? Are you happy with M1 now?

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Jerry
Moparts Member
Posts: 1961
From: WARREN, MI
Registered: Nov 1999
posted 10-02-2002 11:18 AM

the engine has plenty of torque so i went with the m1 to gain more top end. i think i made the right choice as i like the way the car drives and i can incinerate the tires at 1200rpm in 1st - 3rd gear.

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booster
Moparts Member
Posts: 1222
From: Minnesota
Registered: Mar 2000
posted 10-02-2002 11:28 AM

If you are happy with the way it runs, I would modify the manifold that you have.

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Jerry
Moparts Member
Posts: 1961
From: WARREN, MI
Registered: Nov 1999
posted 10-02-2002 11:32 AM

well the efi is going into my roadrunner. thats the experimental car. the challenger is staying stock as its a 71 383 power everyhting car. 1 of 129 made that year.

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ProMax Carbs
Moparts Member
Posts: 179
From: Indpls, IN USA
Registered: Jan 2002
posted 10-02-2002 12:17 PM

Well we are going to use the new Edelbrock Torker intakes for our setups. The M1 is also a good option. We just completed the conversion on a small block Victor Jr. It has turned out really nice. We have just started doing these conversions for Mopars so if interested shoot me an email. I have some pics but do not have them on our website yet.
Thanks

Ben J. Gorman
ProMax Carbs & Performance Parts
www.promaxcarbs.com
email: sales@promaxcarbs.com

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Streetwize
Moparts Member
Posts: 1425
From: Charlotte,NC USA
Registered: Dec 2000
posted 10-02-2002 02:46 PM

If you have direct port injection (be it batch or direct fire) your two most important considerations IMO are equal/near equal cylinder to cylinder "raw" airflow and the ability to place the injector bung at the optimum angle to fire the nozzle at the intake valve where the fuel does not Splatter against the port floor at high volume flows. The dynamics of a DRY DFI manifold verses a typical WET carb are quite different; with dfi carrying the fuel in suspension is less of a consideration however the column of air moving past the injector can have a dramatic effect on burn efficiency. The Torker 2 has relatively good distribution as well as room to install injector bungs, The Team G has good raw flow but the building the optimum injector angle into the runners might take some work. The new Victor already has nitrous bosses cast in the manifold, I've yet to work with one of those.
Mapping of the injector pulse verses throttle position and ignition curve can take much trial and error to perfect. I applaud those taking the neccesary steps to bring this technology forward an to the MoPar crowd. As it stands, we're probably several years behind the Ford and GM State of the art crowds but with the coming of the new Hemi that may change quickly.

Wize

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Jerry
Moparts Member
Posts: 1961
From: WARREN, MI
Registered: Nov 1999
posted 10-02-2002 04:23 PM

i am thinkning of using the megasquirt computer. i guess they also have a timing computer in the works. i may eventually step up to the accel gen 7 but they are very expensive.

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efisixpack
Moparts Member
Posts: 188
From: Redford, MI
Registered: Jun 2002
posted 10-02-2002 09:33 PM

Jerry, I agree that the Gen VII computer is not cheap. Especially when using the optional linear O2. The reason I decided on that system for my small block was because they have great tech support, it's really easy to adapt to any EFI set-up, you can run sequential if desired and best of all with the linear O2 it's almost self programming. Not entirely but a lot easier than my electrotive set-up will be. I wish the gen VII was around when I started my first efi because that's what I'd be using on both. But again, not cheap. What is it about the system your considering that peaks your interest?

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Jerry
Moparts Member
Posts: 1961
From: WARREN, MI
Registered: Nov 1999
posted 10-03-2002 06:30 AM

first i'm a do-it-yourselfer and you have to assemble this kit. secondly it has a c++ base code which is easy to change and adapt if i need to. thirdly its very cost efective compared to the gen VII

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Streetwize
Moparts Member
Posts: 1425
From: Charlotte,NC USA
Registered: Dec 2000
posted 10-03-2002 08:49 AM

Another thing I thought I'd share. I've done a ton of DFI set-ups with various bore/stroke combinations, mostly on race type 5.0 motors. Cam timing with EFI tends to prefer wider lobe seperation than with a carb. If you think about it this is logical because you are not dependent on scavenging to pull more fuel into the motor during the overlap phase. Additionally reversion at low speeds can have a detrimental effect on cylinder to cylinder pulsing at low throttle openings. This is in part why you tend to see isolated runners coming from a large main plenum on most production motors. Runner length has a dramatic effect on torque output on EFI motors, the bigger the motor the shorter the runner. But in either instance they like a smooth constant column of air, the larger and shorter the runner area, the more difficult this is to achieve and the more impact valve overlap will have on the pulse waves reflecting to and from the plenum/valve. The intake tract has to be thought out all through the valve timing, I've had good luck with big runners and relatively late opening of the intake (counter-intuitive if familiar with conventional carb tuning) combined with aggressive rate lobes
so the valve "catches up" by about .150-200" lift. Generally speaking, if your DFI motor makes better overall power with a dual plane type manifold, I'd suggest your lobe centers are maybe too tight and or the intake is opening relatively too soon.
Wize

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booster
Moparts Member
Posts: 1222
From: Minnesota
Registered: Mar 2000
posted 10-04-2002 09:43 AM

Wize: I think you lost me a little bit here! You talk about the EFI engines liking, smaller, longer runners than with a carb, which makes sense, looking at the factory stuff. What doesn't add up to me is that you said that an EFI engine should do better on a single than dual plane. Wouldn't that be opposite, if you are going just by runner length and diameter, as the dual planes usually have smaller, longer runners than the singles. On the TT340 I have found that a single makes better top end power, but had worse cruise efficiency and cylinder balance, while the dual planes had better balance and midrange, but slightly less on top. This is with the Speedpro EFI, non sequential.

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Streetwize
Moparts Member
Posts: 1425
From: Charlotte,NC USA
Registered: Dec 2000
posted 10-04-2002 11:09 AM

A 180 degree dual plane manifold cylinder runner "shares" 1/2 a plenum with 3 other cylinders, this means the pulses fron the plenum are constantly changing direction, sort of a "Tug of war" between the runners to the plenum. On a carb motor the smaller plenum volume (verses a single plane) is a benefit at low and mid range speeds because the signal (relative vacuum) to the carb is stronger and helps keep the velocity through the carb strong at relatively low engine and piston speeds and keeps air/fuel mixtures in suspension. Also the larger the motor (and often the longer the stroke), the less dependent the motor is on runner length to generate good port velocity for a given cross sectional area. So there are a lot of variables to consider, there is no "one size fits all". It's worthy of mentioning that most of he Edelbrock Batch fire systems I've worked on and tuned use small runner single plane manifolds, even on 5500lb Chevy 4WD trucks. They basically convert the "wet" throttle body injectors to a rail system and use the existing TB as a mass air sensor only.
The long runners with a common plenum I was referring to is common in most production EFI systems, the small isolated runners tend to be tuned for optimum low and mid range torque; larger, shorter runners work best at higher rpms due to lower surface friction and closer to the Throttle plate which (at high engine speeds) has plenty of velocity.
A good example of this is the old Taurus SHO which has both long and short runners controlled by a throttle position and engine speed sensor.

Booster, with a turbo you're introducing positive pressure into the plenum which changes the whole dynamics of the "lesson", I'm not suprised in your case that the dual plane works better, under each one of your intake valves is seeing air that is "pushed" to it rather than "pulled" in from the cylinder on the intake stroke. Under boost, the effect of runner length/diameter is pretty much negated. You are also running a batch fire set up which means the throttle position and airflow through the throttle body determines the 'mass' air/fuel requirement for the motor, if it were a individual or sequential fuel delivery, I think you could probably tune around the low-end difficulties you're having at part throttle with the single plane. I wonder if youy did the popsicle stick mods to the street dominator whether that would improve the cylinder to cylinder distibution problems. another thing I have seen with dssbatch fire systems is that when you go from WOT to part throttle there is a "backwash" effect where extra fuel gets forced through the motor momentarily, it show up as a rich A/F spike and can possibly foul plugs. The danger here is if the motor were to have a backfire, I think I would consider building a burst plate below the throttle body just in case this occured.

Don't want to turn this into a novel (oops! too late), and this is considerably "over-simplified" for sake of general discussion. But that is my line of thinking from playing with the various systems. I do not profess to be an expert by any means and your results and mileage may vary. With regard to tuning, Batch fire is IMO kind of a bridge between wet fuel/carburation and programmable DFI. It's a little bit of both and not enough of either . i do believe the potential of turbo motors with programmable sequential DFI is almost limitless, this is one place where one the street at least the "Ricers" have a leg up on us, The Hondata system they have is cutting edge, there's no other way to say it. The V8's are natually behind the curve mainly because we don't need forced induction to go fast, but as the ricers start to go quicker and close the gap, we'll have to pull the other arm from behind our back!

Wize

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booster
Moparts Member
Posts: 1222
From: Minnesota
Registered: Mar 2000
posted 10-04-2002 12:02 PM

Wize: Very interesting information, I kind of like techinical "novels".
A couple of things I have found, and others that I didn't make clear. On my dual plane that I run on the EFI, I have the divider milled off completely to make an open plenum (at least as open as you get with a big step), so I would hope I would have reduced some of the fighting between cylinders. I also use the Accel 90 degree adapter, which adds a bunch of volume to the plenum. I have "packed" the plemum area to reduce the volume, and found it hurt the top end a bit, but didn't do much for the bottom.

On the single planes and popsickle sticks. My experience has been limited to a Street Dominator, and I did do the popsickle stick thing a couple of times, both with carb and EFI. What I found was that if I got the mixture balanced at WOT, it would be way off at cruise. If I got it balanced at cruise, it was way off at WOT, both with the carb and EFI. I could not come up with any way to get it decent at both places. I have not seen the balance problems with GOOD dual planes, they are good at WOT and cruise, both with carb and EFI. Bad dual planes behave as poorly as the single plane.

You are correct that the turbo does change a few things, but I think it is mostly the low compression and odd camshafts that do the most to it. You do have the capability of having more pressure to push air in 30 psi at 15 psi boost, rather than pushing with the atmosphere at 15 psi, but the numbers I have heard (don't have the capability to measure mine) show similar pressure drop through the head with turbo or N/A.

The one major difference I see between EFI and carb is how you wind up with varying mixtures between cylinders. With the carb you worry about the carb seeing even signals to provide fuel to the air consistently, but if one cylinder gets more, or less mixture, it changes power output, but A/F mixture, if the carb works well. With the EFI (non trimmed), the cylinders all get the same amount of fuel, so if the airflow varies between cylinders, your mixture and power both go bad. I think this is at least part of the reason the factory engines try so hard to match the runners, so that they react to rpm and load changes the same. Individual cylinder trimming can take care of this problem, but the trimming would need to be mappable, by cylinder, by rpm, and by load, and don't think any of the aftermarket units are that flexible yet. I have been told, but not confirmed, that some of the factory cars are totally programmed by cylinder for the entire fuel map, under all conditions. That would be a big job!

I still hope some day to make an individual runner, large plenum EFI manifold for the TT340, but there never seems to be enough time.

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