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Old 30th January 2007, 12:37 PM   #21 (permalink)
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Re: Stack Injection and Power Loss

Hi, all. Re. Jim C's thought that almost all DFI 8 stack set-ups use TPS, I'm not sure that's accurate. I don't. I run in MAP mode and have no problem with large droplets(?) at idle, with Venom 36# injectors.

Re. air filters vs. stacks, I copied Bill Bayard's set up, and got definite increases in HP, Torque AND area under the curves on the chassis dyno when I switched from 8 K & N 3.5" tall filters to 90mm velocity stacks, specifically, 20 HP and 20 ft. lbs. Most noticeable was the HP, which went from a peak of 350HP at 5900-6000 then falling off, to reaching 370 HP at 5300-5400 RPM and remaining flat at 370 HP all the way up to 6500 RPM where we shut it off. The Torque curves showed a similar improvement, but not as glaring.

Re. the discussion on a separate piece of plexiglass and sealing off the air box, question;
Are'nt we talking two separate things? 1, sealing to keep dirt out of the motor (doesn't have to be perfectly airtight) vs. 2, Airtight to provide an accurate MAF input. Re. 2, If you run the ECU in MAP mode (vs. TPS), don't you get most(?) of the advantages of an actual manifold fuel sensor? Without having to have a perfect measurement of intake air?
I'm running ACCEL's DFI, and since I went to manifold referenced fuel pressure regulators, I have had zero problems. The plugs (after a little individual cyl. tweaking) all look great and matched. The fuel pressure goes as low as 35psi slowing down in gear in idle/over-run, idles about 40 psi, with a nominal 44psi setting at WOT. It pulls cleanly from 1500 RPM in 5th gear.

Attched: what it look's like. I have K&N filters in each body duct a-la Bill Bayard. So far so good.

Mike
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Old 30th January 2007, 12:37 PM   #22 (permalink)
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Cool Re: Stack Injection and Power Loss

I am curious about the pure driveability question, I realize that in some countries you have a emission standard that must be met and that can't be done with Webers. Except for the emissions and possibly some gain in fuel economy I don't feel that there is any reason to spend the extra money on a fuel injection system. If it was a true standalone system that had a learning capability and would drive like a new car then it would seem to be worth it but the difference in cost will buy a lot of gas for my weber powered car.
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Old 30th January 2007, 02:57 PM   #23 (permalink)
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Re: Stack Injection and Power Loss

Mike,

We are kind of talking about 4 things at once:

1) webers - air filtration/reversion issues

2a) EFI - (MAP/TPS) which are usually BOTH used and called speed-density. The issue here with 8 stack throttle bodies is "what is the manifold pressure?" There aint no manifold! Usually individual small tubes from each TB are manifolded together to give an appoximation of manifold pressure (MAP). This is not issueless, but seems to work OK when coupled with the throttle position sensor(TPS). I am not as conversant with this (so, I'll let others speak to speed-density which has been around the longest and is what nearly all aftermarket engine management systems (EMS) are based on) as I have focused on,

2b) EFI w/MAF which generally combines all three: air flow measurement (MAF), MAP and TPS. There can be other inputs with both 2a and 2b including (but not limited to) engine temperature, inlet air temperature, ambient air pressure and both use some form of timing input obviously.

3) Aesthetics

The closed in rear deck area will not suffice as a MAP source for speed-density. The plexy box might give a useful MAP input, but you couldn't just throw something together without possibly adversely effecting performance. As I recall from my discussions with Adam Christian on this, if the top edge of the trumpet flare were perfectly flush with the floor of the box, the air flow into the stacks is maximized and reversion is somewhat subdued. And that is all I have to say on that subject, as again, it wasn't my area of interest at the time.

Closed loop idle control is not possible with 8 stack EFI as it works with the idle air contol (IAC) valve on a common manifold EFI system. And, I don't think anyone has made tiny little stepper motors that could control tiny little IACs for each TB yet ;-)

Lynn
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Old 30th January 2007, 03:09 PM   #24 (permalink)
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Smile Re: Stack Injection and Power Loss

Yes, I should clarify that reversion as per Ross Nicols case only pertains to Carbs & Non timed injection like Hillborn etc. With timed injection & fuel only being introduced during the intake period fuel standoff should be at a minimum.

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Old 30th January 2007, 10:01 PM   #25 (permalink)
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Re: Stack Injection and Power Loss

Damn! The excitement is draining from my body.(Please stay away from that one Pete). I have sequential injection so I guess I would'nt gain from fitting the filters.I'm glad my excitement didn't reach fever pitch LOL. The cone thing caught my eye too Jac Mac and I now assume that I wouldn't gain anything by going down that track.You guys with carbys need to get into the 21st century.(Flame me over that statement if you must).Anyway out of interest my Motec injection inputs include TPS, Air Temp, Water Temp, Map (reading barometric pressure only), Cam/Crank sensors from distributor. So load is determined solely by the TPS and it works fine, none of the stuttering you get if you floor the accelerator with carbies and a big cam, just beautiful clean power at all revs, I will never go back to Carbs.

Ross (injection only) Nicol
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Old 31st January 2007, 05:20 AM   #26 (permalink)
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Re: Stack Injection and Power Loss

Quote:
Originally Posted by ross nicol
.Anyway out of interest my Motec injection inputs include TPS, Air Temp, Water Temp, Map (reading barometric pressure only), Cam/Crank sensors from distributor. So load is determined solely by the TPS and it works fine, none of the stuttering you get if you floor the accelerator with carbies and a big cam, just beautiful clean power at all revs, I will never go back to Carbs.

Ross (injection only) Nicol
Well said Ross - M48Pro - Kinsler TBs - 8 coils - sequential... - AMEN to modern electronics...

Of course you could always fit hidden fuel rails below a turkey-pan, beneath existing Webers, for that 'authentic look' without any 'authentic hassle' . Would work well with bigger motors as you could rip out the venturi restrictions as they would no longer be required.....
(48s become...48s!)
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Old 31st January 2007, 05:51 AM   #27 (permalink)
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Re: Stack Injection and Power Loss

Mikegaan

If you can run in map sensing on your efi I would only presume that your manifold has balance pipes.

As if it had separate runners and running in map it will only pick up one pulse from that one cylinder and the ECU can not make a good decision on that.

As you can run MAP that is even better for you as the load sites are 3 diamentional instead of 2D with TPS and RPM only.

if a manifold had no balance pipes thatís when TPS is used and the MAP is hooked to the ECU but not to manifold vacuum.
The ECU uses this as an altimeter.
(Autronic & Motec and others im shore)

My comment on the injector droplets was more about atomization.
A lot of people often over size there injectors and at high rpm its fine but at low engine speed the ECU can have trouble controlling a high volume injector
at low duty cycles.

It is often a common error EG engine makes 400hp and has injs capable of 600hp that makes them aprox 20-25% to large(all rule of thumb).
Generally the smaller injector will have a better spray pattern and aid in better drivability that was mainly the point about droplet size.

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Old 31st January 2007, 06:16 AM   #28 (permalink)
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Re: Stack Injection and Power Loss

Quote:
Originally Posted by 561234
I don't feel that there is any reason to spend the extra money on a fuel injection system.
David,

Go for a ride in a GT40 with a well tuned 8 stack EFI/Motec setup. You WILL be converted! There is no comparison whatsoever. Find somebody in the San Diego area who has an 8S EFI/Motec setup, and beg a ride. You won't regret it.

Throttle response is frightening, driveability is UNQUESTIONABLY better, and once tuned, that's it. Just get in, drive, and enjoy! No more tinkering with jets, airscrews, backfires, etc. EFI is WELL worth the extra money!



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Old 31st January 2007, 10:58 AM   #29 (permalink)
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Re: Stack Injection and Power Loss

Quote:
Originally Posted by Fatal Attraction
...
Throttle response is frightening, driveability is UNQUESTIONABLY better, and once tuned, that's it. Just get in, drive, and enjoy! No more tinkering with jets, airscrews, backfires, etc. EFI is WELL worth the extra money!
Are we talking about Weber's or Holley's? Weber IMHO are more for the show, I would not run them expecting much other then a long history of tuning and maintenance (again IMO). The Holley on the other hand can be bolted on and run generally fair without much work. Get a worked over car from the likes of Stan or DamBest and I'll guess most of your carb bias will be gone. I do have a TWM and simple Haltech ECU and I'll bet again that the edelbrock victor manifold + DamBest Carb will make more power then the 50mm TWM Stacks (Again IMO). Bad throttle response, backfires, etc are all indications of something not set up right, including too big carb, big cam, timing, engine cold...and on and on.

Now that all being said I love the EFI, and will be likley the first thing that I do after the car is running. Gota' have the stacks!

Also not free with EFI is cost and complexity, more electronics, sensors, pumps, injectors, surge tank, WB02's, software, PC, etc. So it is good from the standpoint of having to fun project, but adds a lot more then a fuel pump and a hose to the carb.

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Old 1st February 2007, 01:23 AM   #30 (permalink)
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Re: Stack Injection and Power Loss

Hi guys. Interesting thread.
Lynn, (and Jim C) you're right about the MAP. I have a vacuum pipe running from each of the 4 twin throat throttle bodies to a plenum chamber in the valley. The IAC is also connected to this plenum, and closed loop idle works great (butterflies are fully closed). Vacuum hoses from this plenum also connect to the fuel pressure regulators for their reference (nominal 44 psi).
I ran in TPS mode before, and MAP provides much more consistent and cleaner running. I can't say I notice any improvement in throttle response at the higher rev ranges, but the slow 'putz around town' and idle performance is noticeably better.

A question: how much improvement (percentage) would there be from going to a MAF system? Would it be worth a)the trouble sealing the rear deck and b) how good would it look with whatever boxes/plexiglass sealing would require?

Sandy, there was a thread some time back that got into power (especially high RPM power for track purposes) with Ron Earp. Seems the concensus then was that there would definitely be a big HP gain, and no RPM limitations (obviously within engine specs) with a single plane manifold and a good carb. The limitation of an individual runner/8 stack set-up, as I understand it, is the single stack/throat. That's all there is, vs. the plenum and 4 barrels (or 8?) of a carb. At any one instant, a cylinder has access to the entire plenum. So, 8 stacks look great, are great for mid range, but start to run out of steam at higher RPM. I believe somebody said you could get up to the 7's with 8 stacks, whereas you can push 8-9000 rpm with a good carb set up...but I'm getting out of my league here. Somebody help me out
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Old 1st February 2007, 02:40 AM   #31 (permalink)
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Re: Stack Injection and Power Loss

Mike - I'll have to look at the thread, but I think it was related to Weber Carbs, not so much the EFI stack setup (will have to take a look), it is a good thread.

The thing that you get with EFI is nice even fuel disto that the carb and intake can't usually do (due to runner lenght mismatch, etc). I also wonder what the EFI fuel atomization vs a Carbs emulsified approach does to performance. I would for some reason expect that the carb does better with the air mixin' the the dropplets of fuel sprayed at the valve, but way out of my league.

I would love to have a shoot out on the dyno it would be and EFI vs Carb. I would also expect that for different applications (street vs race) the winner might be different. Out of the box a correctly sized carb should bolt on and go, and do reasonably well, if not you have other issues.

I run a horrible combination of parts on my 65 mustang (Big heads, big manifold, large carb, an old school 106 CL Roller Cam, etc), and I have an out of the box 830Cfm cup carb that does OK, room for improvement yes, would I have got as far with EFI in my application, not a chance. I would expect to have it on the rollers for tune, have burnt up a couple of WBO2's etc, so cost of entry for EFI is much higher for me IMO, like I said I want the stacks, but I can see where the 1950's technology of the 4150 is hard to beat. 4 bolts a fuel line and your good to roll Spend some time with either and you will get what you put into it same for EFI or the carb. EFI is much better a overall fuel control my guess, think of what the carb must deal with dynamically, roll down the straight at 8200rpm, slam the throttle shut, low speed performance etc, EFI being smart just say Oh, throttle closed change the duty cycle of the injector to xyz% and be ready for the next evaluation of all fuel curve parameters.

Some day if the engine guy ever finishes the build, I have a 331 12:1 motor going together for the mustang and I have a out of the box 830 and a DamBest version carb and will see how good a 'tuner' carb is vs. the box stock pro Holley. Also most carbs comes with free bonus fuel injection for quick throttle response...it's called the accelerator pump

Sorry been a long coffee laden day!

Sandy
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Old 1st February 2007, 06:50 AM   #32 (permalink)
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Re: Stack Injection and Power Loss

No doubt Sandy, if I was "allowed" to run carbies, I would have been on the road weeks ago. However to get my car registered, it must run the Motec/EFI setup and that costs A LOT of money and takes time to set up; especially for someone that is learning as they are going....
That being said, there are benefits to having it - so if one must, then what the hell....
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Old 1st February 2007, 09:39 AM   #33 (permalink)
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Re: Stack Injection and Power Loss

Mike,

That is really cool. The lines I have seen previously that were used to provide a manifold pressure reading for the EMS didn't look large enough to supply enough air even for idle. What size lines are they? Do you have any pictures of the setup? I'd love to take a look at it. I wondered about losing the (accurate) manifold pressure input when the IAC was open, but it dawned on me, "who cares, you're in idle mode on closed loop."

561234,
I thought of another thing that EFI can do that a single carb can't do and that is enrichen on a per cylinder basis, depending on which EMS system is used. Ford V8s are known for having "hot" cylinders and this will allow you to protect them somewhat by running a slightly richer mixture in those cylinders. Webers should be able to do this as well.

Lynn
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Old 1st February 2007, 10:43 AM   #34 (permalink)
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Re: Stack Injection and Power Loss

Quote:
Originally Posted by mikegaan
e?
Sandy, there was a thread some time back that got into power (especially high RPM power for track purposes) with Ron Earp. Seems the concensus then was that there would definitely be a big HP gain, and no RPM limitations (obviously within engine specs) with a single plane manifold and a good carb. The limitation of an individual runner/8 stack set-up, as I understand it, is the single stack/throat. That's all there is, vs. the plenum and 4 barrels (or 8?) of a carb. At any one instant, a cylinder has access to the entire plenum. So, 8 stacks look great, are great for mid range, but start to run out of steam at higher RPM. I
Mike, I think a big part of the issue was the actual choke size. Lots of people have 48mm IDAs and IDFs. But one thing a lot of folks don't realize is that the largest choke that fits into the carb was 44mm, and the vast majority don't have that fitted. My IDFs from Pierce had 42s I think, and another set I was looking at had 38s fitted. The flow through the largest choke was limiting to the stroker motors if you wanted some RPM out of the motor, i.e., greater than 6200-6500 RPM. YMMV.

289, an old poster on the board, has some dyno plots of, guess what, his 289 engine with webers. It doesn't have any RPM problems because the engine is small and if I recall correctly even 42mm chokes supported a lot of RPM, 7000+, on the small V8. But enter in all the combinations that we are running these days, large displacment, as well as radical cams, bullet proof bottom ends, etc. and then the webers appear to be stretched in flow capacity.

I like the webers in look, feel, and sound. But I don't think they'll beat a 4bbl on a modern V8 build.

The throttle bodies are a different animal though. They don't have that choke limitation the webers have, and they are generally have larger bores than webers. I'd imagine that most of those won't be limited with flow, but I do know that a couple years back some RF cars, and one CAV car, was dynoed with stack injection and all lost some fairly significant hp with the filters run on the stacks. 35-50hp as I recall, using the stainless steel "caps" impregnated with some sort of fitler material.

Best,
Ron
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Old 1st February 2007, 10:22 PM   #35 (permalink)
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Re: Stack Injection and Power Loss

Lynn, I use 1/4" vacuum hose to the plenum, MAP etc. Attch. is the only picture I have, not very good but it gives the idea. I also use 1/4" steel pipe (inside) that connects to the IAC motor with it's own neat little air cleaner, all hidden inside/under the rails/throttle bodies.
Ron, the previous thread about HIGH RPM power ( you were looking at track applications, with >7000 RPM peaks) went into some depth re. limitations of the 8 stack systems. I'm too lazy to dig up my automath book, but as you say, a 340-350 cube engine requires a lot of air at 7500 RPM. The equivalent individual throat diameter would have to be pretty big, which then introduces air velocity problems at low RPMs. I guess you could do it on a full race motor, but I would think it would be a royal pain in the butt to drive on the street?
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