Rockn-Roll

I want a fuel injected 350 that I can bolt in and fits under the hood. Not insterested in an LS or LT engine. I am fairly sure that I want the ZZ4. However, I'm unsure about the EFI system. I was going to get the Edelbrock ProFlo EFI system, but then I saw their ProFlo2 EFI system, and it indicated that their previous version was not true sequential injection...two valves are opened at the same time, but their ProFlo2 system is a true sequential system.

I'd get the ProFlo2 system, but from the pictures it looks like it is taller than their previous version...which totally sucks because their original version was exactly the same size as a stock intake and carb.

I'd also get the GMGoodwrench RamJet 350, but I'm not sure if it would fit under my hood...and I'd like to avoid repainting my entire car just because I need another hood...I might be willing to modify the motor mounts to lower the engine 1/2" or so, but that's about it.

Has anyone installed a ZZ4 with EFI that fits under the hood?

DIP51

I have been asking about FI for my car (zz454) on this forum also. I haven't really had too much feedback, so I have been searching on my own. I stumbled across a web site for Mass-Flo fuel injection, and read up on it. Of course, you have to temper their claims a bit(they are, after all, trying to convince you of their product), but it seems logical to me how they go about producing a system that is plug and play, and not something you are always plugging into a laptop.

It seems like they have clearance issues in mind also. I think when it's time to make out my Christmas list, I'm gonna ask Santa for a setup to go on my B/B!!!!! That is, unless someone here has any better option!!!

tjl82

i have the mas flo on my 80 L82 it is plug and play unit when you buy the unit tell them its for a corvette [hood clearance] they will mill the manifold so it will fit look at my avatar pic

Rockn-Roll

Hmm...the Mass-Flo web site has some good detail. Except they don't say whether their system is a sequential injection system. Apparently the trend was to turn on pairs of injectors at the same time so that the system only had to calculate injector duration 4 times per revolution instead of 8...which means some cylinders will run more efficiently than others. Their system is also a mass air flow system which requires a baffle in the air stream of the throttle body that restricts the air flow...making respond just a bit sluggish...similar to the upper butterflies on the secondaries of a rochester carb...and provides a reading of the surface air that the air is flowing through so the computer can calculate how much fuel to add. Unfortunatly, this really doesn't provide how much volume of air is flowing into the cylinders, and the engine will run rich when you first open up the thottle. I haven't really looked at these systems in detail, but I know they require a huge array of numbers called an air/fuel map...and a map sensor which determines which set of numbers to use. Which is why the entire system has to be returned to them if you change anything on the engine such as exhaust or even the air filter. This is why almost all mass air flow systems provide a computer interface so the user can modify the air fuel map.

Speed Density systems use a pitot tube pressure sensor and air speed gauge which does not interfere with the air flow...hence more responsive. These two devices along with a temperature sensor provide the computer with exactly the number of molecules of air entering the cylinders so that the exact number of molecules of fuel can be determined. All that needs to be done for this kind of system is calibrate it...after that the only time you need to change anything is if the size of the compression chamber is altered. Edelbrock uses a speed density system which is why I'm interested in their equipment.

Edelbrock's new Pro-Flo2 system is just slightly off...it's 1/4" taller than stock and the angle is off just a bit with the rear .16" taller than the front. I think the stock cowl induction hood can manage taking up the excess. I'm just wondering if anyone has tried it with a ZZ4, or if there's another system that's better.

73 LS-4

The major benefit of a speed density system is in its simplicity, it's actually a less adaptable system then mass air. Ask any of us old 5.0L guys about the adaptability of an 88 5.0L mustang system and an 89 5.0L system. Speed density computes it's fuel delivery off of tables. given engine size, rpm, and engine load (MAP reading), add in the other sensors ECT, IAT etc, and the computers then goes to it's tables and gives it the amount of fuel in this cell. This is then corrected for most PCM +- 25% from the O2 sensor reading. This is in cruise mode, now under WOT conditions with most OEM systems the O2 sensor is ignored and fuel correction is not possible. Thereby the adaptive limits at WOT of most speed density units. Now of course all of this can be remapped and corrected, and never underestimate the advantages of a simpler system. Now the Mass Air system, does not calculate airflow, it physically measures it. This means most MAF systems can have some correction at WOT, even though both systems normally ignore the O2 sensor at this point. MAF systems also require a faster pcm then speed density since it's not looking at a table as much as it's constantly calculating. It's drawbacks are that it's more complicated, normally more expensive, and it's one more possible restriction in the intake tract. The more accurate fuel delivery adaptability of the MAF system is why almost all current auto manufacturer's (Chrysler being the exception on a lot of models) use MAF rather then speed density, to meet the far more stringent emmissions demands then they had when EFI was just starting and almost everyone ran speed density. Now I haven't kept up on the latest and greatest aftermarket EFI systems, some of which may now be running wideband O2's and WOT fuel correction. In which case a speed density system with this capability would be able to adapt to changing WOT conditions after a few WOT runs to give it time to learn and adjust, albeit a MAF system with the same capabilities would adapt quicker since it will see the extra air coming in as well and not just have to adapt to only what it sees in the exaust. They both have their pro's and con's, and it really depends on if you simply plan to bolt this thing on and set it up and then not change the engine much, or if you are planning to constantly change the engine around.


Pat Kunz

glen242

From the Mass-Flow web site:
Our MASS AIR system does it all for you, and provides REAL PERFORMANCE BENEFITS over a carburetor or speed density system. It is by far the most user-friendly and most effective aftermarket fuel injection system on the market. Get improved power and torque as well as improved fuel economy, performance and reliability. Unlike programmable speed density systems, you will never need to tune this system. No laptop, no hand-held programmer, no tuning or tweeking, no dyno! This saves you the hassle and expense of tuning and trips to the dyno. When it comes time to make further engine mods, chances are you will not need to change a thing on our system. If you plan to make LARGE gains in horsepower, and you need to change your injector size, just return the computer, and we will recalibrate it for you, rather than retuning, reprogramming, and more trips to the dyno. Our system is even easier to use than a carburetor. You need to tune a carburetor. With our system, you just install it, and you're done!

Either Mass-Flow is lying their A** off or you are mistaken. Which is it?

TPIShark

I've been running a ZZ4 in my 76 for about 7 yrs. now. Was originally a TPI setup (SLP runners, etc.) but I switched to the Holley Stealth Ram. It's tight, but it fits under the stock hood. At least, without the hood insulation, and I had to remover one of the insulation pins bonded to the underside. Nice manifold too- basically a "dual quad" tunnel ram with an air box on top. Hope this helps. You definitely have choices. Regarding speed dens vs mass air - I think evreyone's right. Mass Air lends itself to modifications better, as it truly measures the incoming air flow, so you don't have to mess with the computer except with extreme stuff. Like a hot cam, which would require a higher desired idle speed, etc. Speed density is cleaner, avoids the extra plumbing and restiction of the MAF (which is kinda minimal if you gut it) but requires careful tuning and expertise to work properly, as it relies more on what's entered in the tables. I'm by no means an expert, but that's my understanding. I recently switched from a mass air setup, running the GM computer and my own PROM tune, to the Holley Commander 950 with the wide-band O2 (Speed Density) and am very happy with it.

86atc250r

I have an aftermarket Electromotive setup I just removed from my '79 to make room for my LS1. It would complement a ZZ4 nicely.

It's a "phase sequential" system with distributorless ignition. Just as the four coils work on the "wasted spark" principle, the injectors fire twice per intake event.

Here's how it works. It fires the injector once, just before the intake valve opens and once during the power stroke. Supposedly, this works even better than just a normal sequential setup because the shot during the power stroke hits the back of the hot intake valve and creates a nice vapor that is drawn in just as the valve opens - then it hits again with a shot when the valve opens. Of course, the pulse width of these two shots are halved compared to what they would be if it were just sequential. Fueling between cyls is even because they all get two shots at the correct time - once on the cyl's power stroke and again when the valve is opening.

In reality, there's not that big a difference in batch fire vs sequential. A tiny bit of idle quality and a little bit improved emissions at idle - that's about it. In fact, probably the biggest advantage from not using batch fire is just a more stable fuel pressure.

As far as my system goes, you can also set it for batch fire if you like, but I don't see much point in that. The system will also do strict sequential if memory serves me correctly, but I believe you would need an external driver setup since it only has four injector drivers - personally, I think that would be a waste and possibly a step backwards though.

A little more background on the system:
It is the latest software and firmware. It allows you tuning on the fly with a laptop. Monitoring and full datalogging. It even has provisions for self tuning/learning. I have it fitted with a WBO2 sensor. The software is capable of using the wideband's output and targeting a specific AFR for a given MAP level and RPM.

The software also has a unique "blending" capability to smooth the MAP signal with radical cams. It kinda works in an Alpha-N / MAP mode at lower RPMs by blending the TPS & MAP signals to get a stable reading to work from at lower RPMs. It actually works very well. The system is also capable of MAF, but I do not have it configured that way.

It also has output capabilities that can be used to control electric fans, it is programmable & can be used to control nitrous, turbo wastegate, shift light, or a number of other things. Seems like there are two general purpose outputs, but can't remember, there may only be one.

It's currently equipped with a 4BBL 1000CFM airdoor and 27lbs/hr injectors - which should be about perfect for a ZZ4. It also has a Weiand Xcellerator intake that was specially cast with bosses for the injectors.

I paid $2700 for the system back in the late 90's, plus the software/firmware upgrades it's had in more recent years. Not sure what I'll price it at yet, but it will be substantially less than that. EFI just isn't that expensive anymore. Although my hood is not stock, it should fit under a stock hood because the airdoor setup is much shorter than a carb.

Anyways - I'll be happy to answer injection questions whether or not anyone's interested in my system....

Also - FWIW, MAF is not what most people claim - if it were, MAP wouldn't exist because of the advantages MAF "has". What you have above from the Mass Air site is a hard "sales pitch".

I have another EFI conversion vehicle that uses MAF & it's not nearly as self tuning as claimed, even though it is directly measuring the air intake. Any EFI system needs specific tuning to run properly and at it's best. Anyone that tells you that you can set up a system and not touch it is lying. MAF is just another way of getting where you want to be. In fact, most people find tuning speed density (MAP) more intuitive & less intensive, I know I sure did. You're basically working with engine load which is easy to understand and interpret.

It took me much more tuning on my MAF system to get the vehicle running decently than my MAP system. In fact, a couple years ago I had to start from scratch on my MAP system (because I lost my source files) and had the car running well enough to go to a distant car show in a couple hours. MAP is also much easier to plumb. In fact, with my system, you can just slap on a traditional air filter, just like a carbie.

MAP actually lends itself to modification better because there are no limitations to the amount of "air" it can measure as there is with a MAF. It's easier to deal with variations in vaccum readings than with erroneous & potentially confusing readings from a MAF that's affected by the turbulence of a big cam.

With MAP there is also no restriction in the path. MAP essentially measures engine load and looks up the required pulsewidth from there. MAF does much the same thing. Practically every very high output EFI system you will find is MAP for these reasons. MAF also completely relies on tables for it's fueling. It's table is Air flow vs RPM where MAP is vacuum vs RPM. Same thing, different way of getting there.

You just have to watch out for marketing hype. People think you can bolt on an EFI and go - the computer will take care of the rest. That's a myth. You have a long road ahead. Ignition tuning, idle quality/anti stall, deceleration fuel cut, acceleration enrichment, cold start, etc are all things you will have to deal with and will take time to dial in. EFI gives you serious tuning power and some tools to make minor corrections on it's own - the main thing to remember is they make MINOR changes. EFI also generally gives you the power of data acquisition - very useful. However, you have to get the calibration close if you want the car to run well.

For me, the ignition tuning has always been the most difficult. WOT is easy - light and part throttle is much more difficult.

Bullshark

I totally agree with your position and explanation of MAF vs Speed Density, however, it has not been our experience that sequential injection is of limited value. When tuned correctly it has measurable impact on performance. More than just idle and improved emissions. Yes, you need an engine dyno to do this, but the ability to tailor each cylinder's fuel using fuel coefficient multipliers over the map/rpm map enhances performance across the total load/rpm profile. I question any advantage claimed by the two pulse phased sequential vs a single precision timed sequential fuel pulse timed prior to valve opening. Here is a tech paper I found on another forum written by Russ Collins - RC Engineering


ATOMIZATION
High atomizing injectors are usually used in Throttle Body applications only, and have a rather wide spray pattern. A wide, finely atomized pattern is wonderful for emissions and economy but can cause problems in higher performance engines. At low RPMs, with a low air flow rate, the slow moving finely atomized fuel has enough time to get past the valve and create a close to stoichiometric mixture. (Air/Fuel mixture of 14.70 - Chemically ideal) As RPMs increase this mass can't keep up, with valve open time, and many of the fuel droplets impinge the port wall and condense. Atomized fuel can only travel at "port air speed" and in large quantities it can actually displace air in the port. With a highly atomized mix in the port, at intake valve opening, the lighter droplets of fuel will be partly blown back up the port [intake port reversion]. This is caused by the residual exhaust pressure [overlap period] still residing in the combustion chamber. Some of this reverted mixture will adhere to port walls and condense. This puddling fuel may find its way home, on the next intake cycle, but it will cause cycle-to-cycle air/fuel ratio variances. The higher inertia of the more condensed fuel will carry it to its target. "The liquid film that wets the walls represents a capacitance that greatly reduces the transient response of the engine." (SAE 950506) This problem is compounded in Gang fire and Semi-gang fire systems, but is not as troublesome in sequential fire systems. Gang fire systems fire all injectors, every rotation, at the same time, discharging half of the required fuel at each event. Semi-gang fire systems fire groups of injectors in the same fashion, half-and-half, each rotation. Sequential systems fire each injector at a pre-determined time and discharge all required fuel in one event, prior to intake valve opening. In either of the Gang fire systems there is no timing-of-event technology in operation, and as you can see it's a rather simple system.

At 8000 RPM the intake valve is opening and closing at 66 times a sec. and is only open for an average of 9 Mil/Sec. At this cyclic rate the transient time to complete the delivery of fuel from injector to valve, is critical. This is why Indy car injectors are very precisely targeted and timed to provide a solid stream of fuel with non-existent atomization, LBDS - Laser Beam Delivery System. In these engines the injectors can discharge fuel, at a "just prior to valve open position" and get it all down the hole. As the fuel impinges the hot intake valve it virtually vaporizes and mixes quite well with the incoming air forming a very homogeneous charge. This is one of the most extreme situations but it's a real interesting one. As an added benefit, the latent heat of fuel vaporized in the chamber also provides charge cooling that makes the mixture denser. A denser, heavier mixture (cold and thick) will produce more power then a thin (hot and light) charge. This is why Turbo intercoolers are so effective. Injector timing, phase angle, is altered by the ECU according to RPM in these systems and can control the delivery impact time precisely. In a Steady State Pressure Fuel System, the injector pulse is always moving at the same speed, regardless of engine speed changes. The velocity of discharged fuel is relevant to the area of the discharge port and the net operating pressure. Pressure changes activated by boost, at a 1:1 ratio, only compensate for port pressure and don't change the static pressure, flow rate or velocity. RPM adjusted fuel timing is utilized for this reason, it advances the injector timing based on engine speed, and maintains perfect impingement timing at all speeds.

It's a known fact that you can't burn fuel until it's atomized. It's also known that you can't burn fuel without air. The most important, of all known facts is that you can't burn anything, if it's not in the combustion chamber. The secret is to provide 'adequately atomized' fuel with as much air as possible. 'Adequately atomized' is the secret phrase of the day. Fuel does not have to be completely atomized at the injector tip (SMD of 10um - 20um) but it does have to get past the valve to do us any good. The more condensed the fuel delivery is the faster it will travel, (regulated by discharge area and pressure) and the more accurately it can be targeted. Recent (S.A.E.) "Injector Atomizing and Targeting" studies have provided us with one of the most prominent advances in High Performance Engine Management. These test programs have concluded that "accurate impingement onto the center of the valve head is vital for good vaporization" and "the targeting orientation of the injected fuel spray is a critical parameter in fuel evaporation" also that "fuel injected directly onto the intake valve yields a significantly better engine response" (SAE950506) What all this means is, different engine designs require a different type of injector to operate efficiently and that 100% atomization is not always required or desired. In racing situations we usually have to do the best we can with what we have or what's available. The goal, of course, is to do the best in all cases and in all situations. The best injector for your engine is the one that will yield an optimal fuel-air mixture and provide the required power output consistent with smooth and reliable operation. This is our goal, and all things considered, we feel that we provide an excellent service in this very specialized field.

Great thread with good discussion points

Bullshark

glen242

86atc250r

What brand of MAF injection are you using, and on which engine?

86atc250r

My MAF setup is a TPI setup. Using '89 program code in an OEM ECM. Burning my own chips & tuning with open source software I modded a bit to suit my needs.

Bullshark - you have a point with the tailoring individual cylinder corrections with a fully sequential setup. My thoughts were more along the lines of the less sophisticated / more commonly available systems that are simply batch, phased, or sequential and treat the engine as more of a unit rather than offering the ability to tune per cyl. There are certainly advantages to be had if you have that level of resolution/control.

EricU

http://www.chevytalk.org/fusionbb/sh...uel_Injection/


The guys at the EFI forum at ChevyTalk have a lot of info, especially on the Holley C-950 (but not limited to the Holley).

Eric.