anesthes

iTrader: (12)

I've been thinking of a lot of systems as of late. A lot of the information floating around the internet on the forums regarding MPFI is vague and misleading when it comes to the technology based on the thirdgen F-Body.

For example, many times I will read a post on a forum where someone will state that MPFI will "deliver the appropriate amount of fuel for the cylinder being fired", and "MPFI will atomize the fuel better because it's sequential".

Neither of those is true for our applications. Take a typical '730 or '165 ECM, it fires what once every revolution (every fourth DRP)


Next we have the TBI style computers - and I just want to say computers for now. Just sit back and think of the firing on these. It alternates on the DRP right, so you fire smaller amounts of fuel much more often. A typical '747 computer can run up to four peak-n-hold injectors which in theory have better pulse control than a saturated type injector.


Ok, so now we know the true and actual limitations of our electronics.

Now let's look at the actual intake design, assuming we are starting from scratch. I propose three designs.

A. Port style intake manifold, with a set runner length of say 5". This could be a miniram, HSR, etc. This manifold runs 8 saturated injectors in batch fire fashion, driven by a '730 or '165 ECM.

B. Single-plane style carb manifold, with a set runner length of say 5". This manifold is coupled with a 4bbl 1,000 CFM throttle body with 4 injectors cast and angled under the throttle opening. The injectors are peak and hold port style, and are run using a '747, '746, or '749 ECM.

C. Dual-plane style carb manifold, like a performer RPM, with a runner length between 6-7". This manifold is also coupled with a 4bbl 1,000 CFM throttle body with 4 injectors cast and angled under the throttle opening. The injectors are peak and hold port style, and are run using a '747, '746, or '749 ECM.


Points of discussion:

1) Does the wet flow design of combo "B" or "C" provide better fuel atomization than combo "A" ?

2) Does the peak and hold style injector offering of combo "B" or "C" provide better injector timing from idle to 6500 RPM, and allow the use of small or large injectors, than batch fire combo "A" ?

3) Would a wet-flow design be more beneficial with a single-plane, or dual-plane combo?

4) Which combo would naturally deal with environmental changes such as humidity and temperature?


I have been thinking about this a lot. Based on a lot of experience with various MPFI type intakes but using batch fire ECM like a '730/'749, I feel that for a typical street-strip car a dual-plane style intake with wet flow would be ideal for operation sub 6500 RPM. My feeling is that the air and fuel distribution would be better, that the intake would have better off-idle performance, and would be more well mannered 'on the street'.


However, I'm not an expert.


Discussion ?

-- Joe

Orr89RocZ

iTrader: (20)

I read a big discussion on carb vs EFI on another board and the general concensus was that a carb will make more peak hp than EFI on most motors when considering older OEM style EFI systems.

With all the cylinders feeding from a common plenum port, you get abit better mixing with the carb style setup because there is an intake pressure pulse acting on the entire intake tract from the cylinders drawing air from the plenum. I guess this is a somewhat turbulent condition based on the firing order of the cylinders, the air fuel mixture is being shifted around to different runners. Also, the fuel has longer path to follow so there is a better chance of atomization/mixture with the air stream.

This seems to be what the carb pros say from that thread. EFI guys are saying with the most modern systems with the fastest processing speeds, you can deliver much more precise amounts of fuel and better dial in the air fuel per cylinder to get max hp per cylinder. Much better than any OEM system out there. I tend to believe this because all the carb intakes i've seen dont flow even across all runners, even when ported so I'd expect a distribution problem. EFI doesnt flow evenly either, but the fuel can be controlled precisely to optimize each cylinder. It would make sense to me that optimizing all the cylinders will make best overall power. EFI can be tuned to even out exhaust gas temps across all cylinders so it should have all the same combustion.

Most modern EFI systems place the injectors near the head intake port instead of near the plenum. The higher pressure of fuel helps to start the atomization process but the fuel really atomizes when it hits the hot intake valve. Some of the carb pros were suggesting moving injectors up higher near the plenum to give a longer path for fuel to travel to better mix in the air.

I would think in our case with the available thirdgen electronics, an EFI car may not make the power a wetflow carb style intake setup would. Like you said, batch fire doesnt give the accuracy as a true sequential type setup in some of the elite aftermarket EFI type systems out there.
The only problem is can the TBI style setups deliver fuel like a carb setup? I would have expected to have seen tons of very powerful/fast TBI based cars but I havent seen any that rival the other EFI based stuff.

Would it be better for a higher pressure of fuel to be shot into the plenum on a TBI type injection system like the TPI based fuel systems?
I just never see any fast EFI setups using TBI type injection systems. Even on some of the very fast drag cars running sheet metal intakes, they have the injectors down near the port for a MPFI type setup.

anesthes

iTrader: (12)

Hi,

Well. I guess it depends on what we consider TBI. I'm not looking at the showerhead style TBI injector as factory, I'm looking at stuff like the Wilson or the Motorvation. Picture attached.

These run higher rail pressure, and run the injector under the throttle blades.
With four peak and hold injectors you can spray the fuel more often rather than batch, and have better control over the injector right?

The question is what is the better setup given our factory ECM options. I think a lot of those high end drag cars running sheet metal intakes are running ECU's with sequential fire, and cylinder trims.

-- Joe

Orr89RocZ

iTrader: (20)

Yeah I understand your point. With our older EFI systems, i'm not sure how effective those kind of injection systems can be. I dont know of anyone running them. The idea seems like it will work well if the injector is fired at the right time when the cylinders are drawing in the air fuel charge. Carb is continuous but injection is not. The timing has to be right.

anesthes

iTrader: (12)

Wow. I figured this topic would get a lot more insight from our members.

-- Joe

Orr89RocZ

iTrader: (20)

I was hoping more would chime in with their thoughts/experiences as well. I've only played with port style EFI, TPI based. I was very happy with how all my systems worked with batch fire and think it can cover most all streetable goals.

I was in the 11's with the all motor MAF 165ecm Stealth Ram 383.
87_TA is in the mid 10's at 130+mph on motor alone with 730 ecm miniram solid roller cam which spins to near 7000 with peak in the lower mid 6K range.
I'm in the higher 9's with 730 ecm using code$59 with very large 80+lb injectors on batch fire, saturated not peak and hold with single plane EFI in the port, not below throttle body. It will be in the 8's eventually once I get a rear end, slightly larger setup and a trans brake It should already be going 9.4's with T-brake.

They all drive well and idle well enough. Those systems are covering the range of most street cars i'd say.

Now for gas mileage, I dont know. I havent been able to drive the turbo car enough to get an idea what the mileage is like but I dont expect it to be anything special. I'm not sure what Tom gets in his miniram motor above but its a 6 speed so that helps. My 383 did get wonderful mileage for what it was. High teens day to day mixed driving i'm sure and thats with little tuning for mileage.

anesthes

iTrader: (12)

I, like you, have mainly run port injection. I had 3 singe plane intakes, one miniram, and a couple of TPI's on my own personally owned cars. They all performed well.

I currently have a nice performer RPM air gap intake. I'm curious if the motorvtion 4bbl unit would work as well or better than batch fire MPFI. If I choose to sell the intake, I can do a MPFI setup using chinese components (throttle body, manifold) for about $1,100. I could probably get $100 for my intake, so call it $1,000 even. Be about $100 more than using a motorvation type setup and a '747 ECM.

But which is better? hrmm. I own all the electronics either way. It's purely manifold/throttlebody/injectors/pump/fuel system we're discussing in the financial equation.

The only other thing I might need is a surge tank, as my fuel tank (1970s) is not baffled.

-- Joe

RednGold86Z

iTrader: (1)

Let me share a bit of what I think I know:

Port (in general - batch or sequential)
1) reduces the transient fuel requirements - making it MUCH easier/possible to keep near lambda 1 during drive cycle transients for better emissions, and making cold starts that much easier, and allowing DFCO to work more smoothly.

Sequential
1) with one injection, you increase the dynamic range of the injector, allowing larger injectors to idle, and reducing the effect of any opening closing variance across the cylinders by half.
2) injecting on the closed intake valve is great for emissions - the fuel gathers heat from the valve, and gets blasted to vapor by the exhaust when the intake valve cracks open during overlap. This excellent vaporization allows a much leaner cold startup/warmup - I run lambda 1.05-1.15 within 4 seconds of cranking for EURO4. Low RPM late open valve injection is terrible - the fuel hits the wall of the cylinder, and stays liquid - and doesn't burn and washes the wall, and exits as HC's.
3) at higher RPM and high throttle, #2 is not so important, so, we're now allowed to inject some fuel droplets into the cylinder where the high charge motion vaporizes the fuel, and vaporization cools the charge, which contracts slightly, which draws in more air to improve VE.
4) transient fuel can be a little more accurate, as the fuel calc is updated more often.
5) 1 injector failure can be noticed by the computer to meet OBD requirements, and also fail more safely (doesn't take out an entire bank).
6) a detected misfire can allow the OBD type ECU to disable the injector for that cylinder in order to keep the cat alive until the fault is repaired.
7) tricks during a cold drive cycle can be done that turn off a cylinder or 2 during a cold decel, giving some O2 to the exhaust that might be a little rich because of the cold ports being extremely difficult to calibrate very accurate transients, and the cat isnt't working yet.

#3 might actually be why carbs make more high RPM power - extra poor atomization until it reaches the cylinder, where it causes in cylinder charge cooling. I hate carbs, though.

Most OEMs don't try to have variances from cylinder to cylinder - they'd change the manifolds to fix it. It's bad to have different cylinder torques sending the wrong vibe to the driver, and it causes the misfire detection algorithms headaches. As for individual spark control - it is - at best - a crutch for a hot cylinder at high RPM. In a more difficult aftermarket situation - such as uneven runners (e.g. a carb manifold) - it might pay off a little bit, but would take a real expert on a dyno to make it right, not the average schmoe.

If either of you guys want to develop a manifold, and have it cast in China - I've got some connections (and I work here in the EFI business). I'm setting up a new R&D in Iowa - bought a chassis dyno (MD1750 de), engine dyno (old sf800), and plan to sell my company's EFI in the aftermarket soon.

anesthes

iTrader: (12)

That is a lot of good information. Sounds like sequential would be cool. Maybe my next build.

What do you think in terms of batch port injection vs peak-n-hold wet flow on a dual plane?

-- Joe

RednGold86Z

iTrader: (1)

Depends on the software and if it's for street use. It takes a LOT of fuel to get the transients in shape on a TBI style injection - and you'll have to just give up eventually in some situations and just stop looking at the wideband so much.

You could do a 'best of both worlds' attempt. Staged or switched injection. One of our ECUs can do switched injection with 4 injector drivers for primary, and 4 for secondary. Use semi-sequential for low RPM or throttle, and switch over to the TBI if you find that to be more powerful.

A dual plane with port injectors, though, might be a little hard to get the fuel rail done, depending on how you get the injectors mounted.

Retrotek (sold to Professional Products) and FAST both have throttle bodies with injectors in them now. It makes the install very convenient if you have a carb manifold and air filter. No idea if they're really better power makers than a properly tuned carburetor or a properly tuned batch or sequential system, but typing the numbers sure is a lot easier than pulling the hot carb apart.

redcorvette

From what I have read the advantage carbs have for peak hp production comes from the continuous injection of fuel (all air coming in is mixed with fuel, no periods of air with no fuel), the cooling effect on the incoming air ( denser charge allows more inertia effect in the runners) and since the fuel is already mixed in if one runner gets less air it gets less fuel or vice versa, all in real time.
For the average home tuner it is hard to take full advantage of sequential operation since we have no easy way to "see" the outcome in each cylinder. Ideally you would be tuning not only for flow differences but also for compression differences in each cylinder. Luckily for the average shmoe like myself who doesn't have to meet emissions one wideband and batch operation will give you an engine that starts well enough, runs well enough and gets good enough fuel economy.
A few years ago I was in contact with a company that made extremely fast pressure transducers that mounted inside spark plugs. They were too busy working with Detroit OEM's and Formula 1 to work with my non-automotive employer. Those transducers might come in handy for you guys when you are setting up your new fuel injection system.
P.S. Please make it fit under the hood of a C4.

Orr89RocZ

iTrader: (20)

A cast 2 piece manifold that looks/acts like a LSx style intake would be awesome. Or a lower profile HSR style intake with a custom tapered plenum to help even out the air distribution problems

dimented24x7

iTrader: (2)

wetflow systems can be a headache if theyre not set up properly. The biggest problem is the fuel dynamics. This is especially a problem with airgap type intakes. The intake temperature varies with the load, vacuum and outside air temp, and theres no easy way to predict it. SD systems work poorly in this type of situation. The only way I ever found to make a wetflow system work well was to use MAF for the fueling to decouple the fueling from the air charge temp, and install a dedicated manifold temperature sensor on the side of the plenum so the AE logic would know how much AE the manifold really needs. Without this, the car was undrivable with a stick.

If you can, go with port injecton, it will be easier. My SFI system is pretty much dead-on AFR wise. With MAF, theres not much need for extensive tuning, and the SFI ensures even fueling as the PCM calculates the fueling for each cylinder.

RednGold86Z

iTrader: (1)

"Keg" shaped or keep tubes? Are you good at CAD? What's the target power range? Target max power? Keep the distributor? LS or TPI throttle? EGR & CSI? Injector location?

It's hard to say there's a lack of options currently available. What's the main deficiency? Is it just the novel look? Maybe a 1467 8352 split plenum "dual plane" cast manifold would be what the market needs.

RednGold86Z

iTrader: (1)

Even with speed density and sequential port injection, I cancel out the air temperature in the equation (with a table that has the inverse of that), and just use a coolant temp vs MAP table. I've yet to find this insufficient.
I have some compensation for air temperature in the transients, too. That is about all I use IAT for (other than to check if the start up was an EOBD start up, and some minor corrections for crank fuel and IAC and main spark retard when very hot, and a little advance when very cold).

The only 'difficult' part with MAF is that it needs a plenum filling and emptying model or filtering to avoid massive over fueling during a transient - the plenum fills before the cylinder, which needs air flow to fill.

Orr89RocZ

iTrader: (20)

I'm not familar with CAD programs else I'd attempt to draw one up. Just an idea for an EFI intake that will work in low clearance applications. Keeping the runners around 6-7" to support up to around 6500 rpm peak power ranges max. Strong 6000 rpm area power. 1205 port but capable of 1206 porting. Got to have a larger cross sectional area than TPI base plates. Will have to support 500+ hp. A street intake like the LSx stuff but not exactly sure how to pull it off. LSx TB front but high enough to clear a water neck as a base LS intake doesnt have a setup like that.

Would keep distributor. Injectors in the port like most EFI intakes for our cars.

Sorta like this but with the runner outlets facing up instead of to the side so a plenum can bolt down on it.



or a base that is sorta like in this pic with a bolt on plenum top


Weiand makes a cast metal LS style intake for the LSx stuff so I know you can cast that shape, just need to change port locations on the runners and create a water neck spot and distributor hole.


Not sure if it fills a niche in the market or not. Just a look of a LS but for a sbc. Can use LS TB's so that would be nice. It would be most practical if it can be done in composite material like LS stuff so you can get the weight savings but I understand that can be difficult and probably expensive.

Simple alternative is to make bolt on low rise plenums for HSR's to clear C4's and other cars.

anesthes

iTrader: (12)

Seems to me the better idea would be to build hybrid SBC heads that will bolt to an SBC but offer an LS1 intake bolt pattern and port height. One of the strong points of the LS stuff i I recall is the port height and shape of the runner in the head.

-- Joe

InjectorsPlus

iTrader: (1)

The strength of the LS1 head is the alternate angle valves. if you go 18, 11, 9* heads on a standard SBC you will get similar results to a LSX. The issue is one of expense.

Anyway there are LSX hybrid motors out there.

World has a combination see the link. I have a good relationship with the Mitchells at world, and can get you a good deal if you want it.

http://www.superchevy.com/technical/...ine/index.html

Now you know my view on magazine articles, worth the paper they are written on, but the platform is there.

InjectorsPlus

iTrader: (1)

Lots a questions. Here's my thoughts.

If your basic concern is fuel atomization that happens in the port of the head, down to the top of the intake valve. This gets into discussions we've had a million times over

It's more of a question of head port design, and once the fuel hits the top of the valve, it's all over anyway.

InjectorsPlus

iTrader: (1)

That is a flat out lie. All fuel delivery systems will make the same power. Carb, TB, TPI, MPFI.

The primary difference is because FI does not depend on vacuum at idle, you can better control the idle with a larger cam.

Nope.

They are wrong.

Wrong again, there is no power difference between a carb and FI.

This is actually an interesting point of discussion. Adding bungs to CARB style intakes has been a discussion of how an intake not designed for FI will work for FI. The other part of the discussion is where to place the bung in the runner, down low, up high?

Again


The issue has been one of having injectors big enough to do it. That's why we're trying to do it.

No

That is because of the lack of fuel you can put in them

We carry a 6 injector throttle body that can handle some huge HP if done right. There's gys running single digits with these.

anesthes

iTrader: (12)

John,

Let's try to not **** anyone off ok.

-- Joe

InjectorsPlus

iTrader: (1)

I wasn't, seriously.

Orr89RocZ

iTrader: (20)

Those were the points top carb guys who are in the business of selling carbs gave for the EFI vs Carb argument, atleast from what I remember seeing. EFI guys gave their reasons as well.

In the Engine Masters Challenges, i dont think an EFI motor has won yet but majority are carbed. There must be a reason for that. Maybe its because they dont know how to work computers and its an expensive cost to go to a good EFI system. I dont know.

The only arguement I have heard/read about favoring carbs over EFI when it comes to power production that I possibly can agree with is that air is constantly drawn into the carb where it mixes with fuel so that there should be a constant and equal air fuel mixture throughout the intake (assuming carb can provide fuel and distribute it into the air evenly and that the intake flows evenly, which alot dont). So when the cylinder is ready to draw in air, its taking an already mixed charge in. In EFI, there are periods where there are air pockets without fuel since the injectors havent fired yet. Could be a possiblity that air is sucked into the cylinder without a proper amount of fuel already mixed with it?

That is where this arguement came from.
In theory, if the motor gets fuel and air of the same amount it should make same power, but most pro carb guys were suggesting that for peak power/VE, carb will provide more fuel. Fuel injection injects in a precise amount and the hope is all that charge will get into the cylinder, while carb is providing constant fueling. No one seemed to know what to believe. Lead to a very long thread.

Orr89RocZ

iTrader: (20)

Problem with a setup like that is that most 18 or lower angle sbc heads have huge runner ports/large cross sections with small combustion chambers. So its hard to get streetable compression ratios and low rpm driveability sucks since flow velocity is low. Torque loss is significant. LSx stuff, even the huge cc L92 type heads still have a smaller cross section and still have decent port velocity for the size. LSx stuff is in the 205-225cc range for 90% of street n/a setups. Most 18 deg and up sbc stuff seems to be in the 230-260 cc range and thats a lot of runner.

1989GTATransAm

iTrader: (3)

Regarding sequential or batch injection Madbill(former GM engineer) stated on another forum that there is no difference above 3500 rpm. Below that sequential is mainly for emissions and a slight mpg gain. I would think for our purposes either would work just fine.

As to the design of the intake system we need to know the parameters. What rpm do we want to make peak power and what is the size of the motor?
This will determine the cross sectional area, taper and length of the runners. Do we want to pick up the 3rd harmonic wave?

After messing around with the aftermarket TPI system I can see the potential of the design. I will include the SuperRam because it is virtually the same as a highly modded TPI. Lets start with the base. I like the design of the First as it is large enough and has enough meat to support a lot of horsepower. The runners are relatively straight into the head with a nice curving transition to meet the angle of the head. They are also the same length unlike a single or dual plane manifold. At around 8 inches of runner coupled with around 5 inches in the head that is 13 inches total length and tunes in the 3rd harmonic. That can be adjust shorter or longer depending on the needs of the motor. The port taper can also be adjusted to the needs of the application.

The aftermarket runners can be fully siamesed or have partial runner again depending on the motor needs. The siamesed ports have now become part of the plenum. As some of have done we have made the top 1/3 of the runner siamesed to all 4 ports. The next portion is now split to two sets of two siamesed runners. The siamesed 4 ports cuts down on the air speed by quite abit and allow the air to turn easier so each port gets its fair share of the air.

With the SuperRam you would only need to siamese the paired ports due to the design. I think it would be interesting to mate the Super Ram plenum and runners to a First intake manifold. With a monoblade I bet you could support 650 to 700 hp and with the 13 inch of runner not give up any torque down low. I believe the LSx intake total runner is also around 13 inches.

InjectorsPlus

iTrader: (1)

Agreed, MPFI over batch fire is more about emissions than anything else. He says 3500, I would say off idle, but he's a smarter man than I.

Yes...

InjectorsPlus

iTrader: (1)

Everyone will have their bias, however the same car with the same setup on the same dyno has demonstrated, no real difference

It's cheaper, and that is what they understand. I sell injectors to guys making 3000 HP using multiple stage, multi 220 LB injectors on the same cylinder. 2,3,4 220LB injectors on each cyl is not uncommon.

IT's a rationalization. Again, same dyno, same car, same setup, demonstrated no difference.


Here's the thing with carb guys. I know a lot of them, I work with their shops. The real issue is they don't understand fuel injection. It's really that simple. I visit shops on the daily basis. Was at one yesterday the guy keeps trying to get me to go carb. He "tried" to do injection on his car, and it just couldn't work. He didn't understand it.

InjectorsPlus

iTrader: (1)

Depends on what you want to do.. Brodix does have a 185CC 18 degree head, I can't get info on Dart because their site doesn't work.

But, yes, you're correct on most of that, so you have to build around those conditions.

Orr89RocZ

iTrader: (20)

This is my conclusion as well. I am the opposite. I never touched a carb before so I have little idea how it all works. i grew up EFI and will always work with it.

Sounds like you just need to buy the First TPI setup and weld in plates to the runner tops to beable to siamese them to pull more rpm range. I'd love to do that to my 401 twin turbo motor since my RPM range now could fit into a siamesed TPI setup if it can flow, and First flows as well as some mild ported single planes.

I'd still be very curious to see an under throttle body injected setup with high fuel rail pressure using proven cam/head/intake combos and compare results.

Or even a near plenum mounted port injection type setup instead of the typical near head port injection stuff like most EFI intakes. I figured there is a reason why most all intakes including sheetmetal stuff uses injectors mounted on the base of the manifold near the head intake port pointing at the intake valve as much as possible. I wonder if there are any reversion effects? On a large plenum I dont think there will be much, but could have some issues on a small plenum like on some EFI carbed based manifolds. Those plenum volumes just seem tiny compared to other EFI intakes like TPI/Miniram/stealth ram, etc. Carb intakes seem to have half the volume of a typical EFI front throttlebody type manifold.

1989GTATransAm

iTrader: (3)

Regarding wet or dry flow in our testing I think the dry flow is better for CFM. With a wet system you want to keep the runners walls somewhat ruff in order to help keep the fuel in suspension with the air.

In the testing we have done it appears the smooth runner walls helps with the cfm and increased power. This is with runners, plenum,etc that have been Extrude honed and with my setup that has been internally coated with a thermal barrier that in essence fills in the voids and makes for a smooth surface. I was going to get my system re-flowed during my recent motor swap but time would not allow for it. I would have loved to have seen the results. Bottom line those cars we have dyno'd with the smooth walls appear to make a little more power than their brethren.

Regarding the First intake manifold and the SuperRam. When I was measuring the First intake manifold I could see where one could get a 2" diameter opening where the runner mates to the intake manifold. On the other end it is no problem getting it opened to a Felpro 1206? gasket. I think with a little welding one could go larger. I believe BadSS was looking into doing that.

If I was going to do it I would make the adaptor plates like did for the SLP's and cut off that portion of the Super Ram runners, weld them on and blend them in so that you could get a 2" hole if need be. That would flow some serious air if you taper it from a 2" hole to a Felpro 1206? gasket. While doing this still maintain a runner of 13" or maybe even 14" with some divider wall inside the runner. I bet we are talking an easy 350 cfm of air flow.

anesthes

iTrader: (12)

That is exactly what the motorvation unit is that injectors plus sells. It runs 4 peak-n-hold port injectors mounted under the throttle blades.

Thats what I was curious about. How would a combo like that work (with like a '747/'749 ecm) on a dual plane carb manifold vs like a miniram, hsr, singleplane port intake.

Good question. Everything I've read over the years tells me that it would run similar to a carb. The fuel would mix and go where the air goes.

But..

-- Joe

RednGold86Z

iTrader: (1)

I wonder how many people would buy affordable ITB's for thirdgens if there was a software that could make it have excellent street manners (idle control, accurate MAP reading, perfect transients and starting, and such)? Probably just too much headache's, but there may be a few brave soles. If they could make a decent one with an electronic throttle control actuator, I'd be all about it (and can control ETC just fine).

I also make an air-bypass system for carbs that makes them closed loop (can only go leaner than the base tune, though). That same ECU can do spark control with a coil driver on board, and can even use toothed crank wheels such as 60-2, 36-1 or 2, 24-1. Actually, any of our ECUs can run this air bypass software. The only problem is getting an air bypass valve that is good enough - IAC or PWM valves are OK, but IACs are slow to move from min-max, and PWM valves are hard to find that are big enough full-on, with a low minimum opening flow.

FYI - I'll be getting our prototype 8 coil driver box back soon. Has 2 knock inputs as well, and an ETC driver (for use on generators and buses with CNG/LNG).

1989GTATransAm

iTrader: (3)

"I wonder how many people would buy affordable ITB's for thirdgens"

What advantages do you see with a ITB outside the "cool" factor? I can think of some dis-advantages for our street cars.

Orr89RocZ

iTrader: (20)

I'd be more impressed if anyone can develop a variable intake runner geometry intake. TPI torque with miniram top end... Best of all worlds

RednGold86Z

iTrader: (1)

Cool, better power, real snappy response, and adjustable lengths and diameters. If horizontal, they can clear any hood.

Synching, linkage, and filtering are always a difficulties of course.

I have software that can read a single cylinder's MAP very well if used with a toothed wheel. That also can substitute for a cam sensor.

Heck, you could use 4 ~TPI throttle bodies bolted to a special base. Put some really weak springs on them, and have the linkage actuator be an electronic throttle controller's guts, and you can have idle control right there.

RednGold86Z

iTrader: (1)

Take a super ram, and put a throttle between each 2 runners. At high RPM, the throttle will open and the length of the runner is effectively cut down to the point of the throttle.

Orr89RocZ

iTrader: (20)

ITB with linkage and intake air boxes sorta like this intake for LSx motors?
I cant help but think you'd want to tune that setup with either wideband o2 input on each cylinder and/or EGT probes on each cylinder to be safe but I guess if they all flow the same you'd be confident fuel delivery would be equal?

Thoughts on a dual plenum setup with 2 LS1 throttlebodys, with the plenum for each bank slightly tapered like this viper setup?

Offers the ability to package good runner length with large plenum volume in a low rise application. Waterneck can be cast into the space between plenum openings. Can just about setup whatever cylinders you want to feed from one plenum. You could experiment with plenum volumes to work with the intake pressure pulses in the intake to tune into the ideal 3rd harmonic. Could give a snappy response as well but be cheaper than ITB's.
Also gives guys planning to run twin turbo setups to have two small intercoolers underneath the car like prochargers dual intercooler setup and have each turbo feed one side of the motor. May beable to package that under the hood much easier than trying to route larger single pipes to the single TB. Just some ideas.

Either way seems like port injection is ideal with majority of the intake being dry flow.

ericjon262

Joe-

I notice you mention the 747 ecm, I can't really think of anyone who runs a stock 747 ecm, IIRC, its because they are slow, they don't take in information as fast as say a '427, or a 747 w/EBL flash.

Orr89RocZ-

if you look at the vortec (Gen 1 not III/IV) intake, it's very similar to an LSx style intake, the only big difference is where the throttle body and the plenum meet, and the port layout. on a vortec, the TB goes down in between the runners from above, whereas on an LSx, it enters on the front.

InjectorsPlus

iTrader: (1)

It exists, look at open wheel racing. Those cars idle at 9000 RPM and the plenum changes size based on demand.

Orr89RocZ

iTrader: (20)

I know alot of factory cars use or have used a design like that, i just havent seen it with a street sbc.

dimented24x7

iTrader: (2)

Speed density works well with dryflow systems. Im sure your aware of this, but with wetflow, the internal air charge temp goes all over the place as fuel responds to quantity of vacuum and begins to boil and vaporize in the incoming airstream. That can really pull a tremendous ammount of heat out of the incoming air charge, which makes estimating the incoming air density difficult. Im sure with sufficient modeling it could probably be made to work.

GM uses what they call dyna-air, or dynamic air to estimate the airmass during transients. The PCM either uses a partially blended MAF/SD airmass, or pure SD alone during transients, and then calculates delta airmass terms based off of the throttle opening, MAP changes, etc. and then integrates the changes together to get an estimate of the future air charge. It seems to work within reason, but the filtering they use is overzealous in a perfomance app. They also have considerable filtering for the MAF at the signal interface level, too. So much so that I dont even bother using any of the software based filtering. Its a little more stable than my straight MAF read in code in the TBI software, but the transients have a noticable exponential attack/decay on the wideband. Not so much to be noticed, but from an OEM standpoint, it would likely cause a momentary rise in NOx/HCs during transients, depening on the conditions.

I've found that typically its enough to model the intake using table based functions using a small, TPS based pseudo-SD logic that estimates the additional entering airmass from surge filling within the manifold. Same with the residual air during throttle closings as well. The MAF seems to be pretty blind to these as the former is too quick to register, and the later takes place entirely within the manifold. I replaced a lot of the dyna-air logic in my vortec PCM with more traditional AE logic, and seemed to get better results. The dyna-air stuff is too involved to tune from a DIY perspective.

dimented24x7

iTrader: (2)

My take on it is to keep the injectors close to the intake ports. Putting them further up introduces live fuel into the equation, which then introduces the need for modeling the fuel wetting/boiling that takes place during MAP changes. There is already a need for that to begin with, but that would just compound the problem.

I have a vic-e, which is basically a victor single plane with injector bungs. I can say one thing that you DONT want to do is point the injector straight down at the floor of the intake runner like they do. The fuel just plops down on the intake runner floor rather than entering into the intake port on the head. I had to move the injector firings several hundered degrees of crank rotation out to give the fuel enough time to vaporize and mix at low speeds and temps. Otherwise, the engine would be real chunky when driving.

Orr89RocZ

iTrader: (20)

I havent seemed to have noticed any issues with driveability on my Victor E setup, even with the large injectors but i'm still batch fire. Does it show up with SFI?

1989GTATransAm

iTrader: (3)

Again from another forum and MadBill. Some interesting points with #5 in particular. Maybe this is what separates the men from the boys in being able to vaporize the fuel and keep it there right up to the combustion process. Notice the difference from vaporization and atomization.

1. Vaporization (liquid to vapor transition) as opposed to atomization (liquid pureed into miniscule droplets, very easily vaporized, but still liquid), cools the charge, thus increasing its density, due to the fuel's heat of vaporization. However the resulting fuel vapor displaces air (referred to as charge displacement), offsetting the gains and in fact for most fuels, per a spreadsheet by David Radzus a year or so back, causing a net reduction of the intake air mass and so power potential.
2. Liquids don't burn, any fuel that is still liquid after the flame front passes through the cylinder contents cannot add heat/pressure to the cylinder contents (the purpose of fuel), in fact it can remove it, by vaporizing too late to burn effectively if at all.
3. It might be ideal, but isn't possible, to atomize 100% of the fuel in the carb or through the injector, but vaporize it only in the cylinder after the valve closes.
4. The trade-off as too how much of each occurs outside the cylinder is controlled by a number of factors, including droplet size, charge and fuel temperatures, manifold vacuum and the distillation curve of the fuel.
5. One effect of very high compression, ignored by the thermodynamic equation that defines the diminishing returns of same, is the resulting greater cylinder temperatures during the compression stroke, which can vaporize any remaining fuel after the valve closes, thus harnessing its energy without causing any further charge displacement and possibly also reducing temperatures enough to stave off detonation. (akin to the benefits of direct injection of gasoline)
6. From these points, it would seem like a fuel should be (and probably is, but I haven't read of it) brewed for, in addition to all the other well-known requirements, application-specific distillation curves for CR, charge temperature, carbureted Vs. EFI Vs. DFI, etc.
7. Several of these points would bear on what AFR gave best results in a specific engine, e.g., fuel burned late or not at all would skew the optimum in the rich direction.

dimented24x7

iTrader: (2)

With SFI, each injector fires a fixed (but adjustable) angle ahead of its associated cylinder TDC. With the firing too close, the fuel wouldnt have time to vaporize. I actually tried firing thte injectors after TDC during the intake event to minimize scavanging of raw fuel into the exhaust, but the motor didnt run that well, especially when it was cold. Keeping it a couple hundred degrees ahead of TDC seems to work best. With batch fire, thats sort of done for you as your firing them all at once w/o respect to each cylinders TDC.

RednGold86Z

iTrader: (1)

Exactly right - injection on an open valve is very bad for atomization and vaporization at lower RPMs - the fuel often flies right to the cylinder wall. This causes misfires and high HCs.

If you get it earlier in the open valve, there's a little bit better chance for atomization as there is still a lot of sheering going on through the low lift flow. But once the valve opens and flow through the valve is slowed down a lot, the fuel just waltzes right to the far wall (according to some SAE papers).

At high RPM and warm engine, it's OK sometimes to shoot at an open valve, according to Bosch. Fuel atomizing in the cylinder might be able to suck in some more air.

1989GTATransAm

iTrader: (3)

So would it be safe to say that the compression stroke does a lot of the fuel vaporization? That would be vaporizing the small fuel droplets(atomized) into a fuel/air vapor. So the smaller the fuel droplets(atomization) the better or better yet turning it into a vapor. I would think spraying the fuel into the backside of a warm intake valve would be a good thing in accomplishing that task.

RednGold86Z

iTrader: (1)

Resting on the hot valve, getting blasted by the exhaust, and flowing through the barely cracked open valve do most of it. Compression heat is combatted by higher pressure - I'm not really sure which one wins when it comes to vaporization. The tumbling and swirling helps, though.