anesthes

iTrader: (12)

If one were to use a modified intake with only 4 injectors (think wet flow), would the '730 drive just the four 85lb high impedance injectors ok?

Would you just use one driver, or do 2 and 2 split like the factory did?

I'd imagine since they are batch and fire at the same time, using one bank would be just peachy?


Of course the next question would be, can a '730 idle properly with 4 85lb injectors, but that is probably more of a diy_prom question.

-- Joe

RBob

iTrader: (1)

Sure, saturated is saturated. No peaking off of the driver. Note that the '7730 only has one injector driver.

RBob.

anesthes

iTrader: (12)

Hi,

I thought it was two but they were wired together ?

Either way good. My plan may work.

-- Joe

junkcltr

iTrader: (1)

There are two fused power wires to each bank when using 8 injectors. The ground side is tied to one pin on the 730. The one ground is controlled by the single injector driver. You can run just one fused power wire for the 4 injectors.

You may or may not have a difficult time tuning the 85 lb/hrs. It depends on how big the cubic inch, cam, heads, intake, etc. I am running 42 lb/hr on a 355ci, small cam, etc and the PWs are down around 1.2ms. I wouldn't go much lower than that with saturated, but I have heard of newer designs going a fair amount lower.

Over at DIY PROM dimented24x7 mentioned he is working on $0D code with bank fire. It is nice because with bank fire you can alternate banks at low RPM so the injector is pulsed like it 1/2 the size. Then at higher RPM you can do batch fire so that the big injectors can support the HP.

anesthes

iTrader: (12)

I was looking at the fast 4bbl 4150 flange throttle bodies, 900cfm, with four 85lbs injectors. For complete, working, go-fast carb motors it seems like a cheaper way to just bolt-n-go.

The fast unit is $864 which comes with the injectors, rails, tps, iac, map, and an iat. Add a trick regulator for $75 = $939

http://www.compperformancegroupstore...Code=4150Style

Alternatively, a swap I'd do using a singleplane, 4bbl TB, etc would require:

Manifold $350, Fuel rail kit with reg, $275, throttle body $459, injectors $300

$1,384


So I'd say, if you already have a 500+ hp carb motor with a good intake manifold, the 4bbl quad injector solution seems more economical.

Thoughts?


-- Joe

RBob

iTrader: (1)

The issue you will have trying to do this is the injector firing rate. Need to fire the injectors often enough for proper fuel distribution. A standard GM 2-bbl TBI set up fires each injector alternately on every plug firing. On an 8-cyl each injector fires twice per revolution.

With the '7730 doing a double fire, this is all injector once per revolution. Not going to work.

Now, the '7730 was used on 1-bbl TBI 4-cylinder engines. So I'll bet that with the proper MEMCAL strapping it is capable of firing the injector(s) every time a spark plug fires. Which is what is required for a single injector set up.

However, this will severely limit the injector duty cycle on an 8-cylinder. And even more so using saturated injectors.

Another choice is to use a '7749, and PnH port style injectors. Each driver is capable of running two PnH port injectors. The trick is, can it fire them at the proper rate. This I don't know. Although, using PnH injectors opens the duty cycle constraint a bit, as they open faster.

The FAST TB you linked also has progressive linkage. Which is another issue when used with an ECM that is dumb about that.

RBob.

anesthes

iTrader: (12)

Bit confused on this. My logic was, the firing scheme is batch so rather than 8 42 lbs injectors, run 4 85 lbs injectors but leave the injector constant to 42. Should be exactly the same amount of fuel in the same firing window, right?

I had considered that, however the fast unit mounts the injectors under the throttle blades, so the fuel is being shot at the floor of the manifold, so it shouldn't be a problem I think unless you think the fuel will puddle?

On the 4bbl holley units, the injectors are mounted above the throttle blades so I don't know how you'd fix that when the rear two blades are closed.

-- Joe

junkcltr

iTrader: (1)

You are correct about the four 85 lb/hr vs eight 42 #/hr. The problem is the wet flow in the intake and spraying into the plenum and not into individual runners. When you dump all that fuel at once into the plenum you will get poor fuel distribution. The first cyl to fire after the spray gets most of the fuel being too rich and then the last one to fire is too lean. The TBI does alternate fire to not feed it all at once.

Some may not like my theory about using TBI to make high horsepower. It just doesn't work well. The issue with it is you need big injectors with pulse width problems and then you get this plenum problem. If you are worried about hood clearance then I would opt for a modified LT1 intake. It does have slight air distribution problems, but way better than the fuel problem with the TBI.

A complete used LT1 intake is around $150 and with a 110v MIG, some alum wire and argon, holesaw you could have it done in a day. A new set of 42 #/hr injectors are less than $300. If you keep you eye out on ebay there was a guy selling new bosch port PnH 51#/hr for $17 each shipped. They come without the caps which is $20 for a set.

I would consider using PFI especially if you plan on boosting it later. TBI is great for low HP engines (around 400Hp and less). The sky is the limit with PFI.

EDIT: Is this for your second gen Camaro? I know a holley HSR will not fit with the stock hood. Not sure about a TPI intake, but they don't make HP anyway (nice truck torque though). The LT1 intake fits with a mile of room to spare. The bad part is the water lines and remote thermostat housing. I am running this setup and it is just plain ugly, but the intake looks neat with it being almost the same height as the tall valve covers.

Orr89RocZ

iTrader: (20)

Probably the best bet here. You can do victor E EFI manifold with rails, 411 bucks. Regulator...100-150 bucks or so, edelbrock intake elbow for LS1 TB--100-150 bucks or s custom aluminum one from intake elbows.com-225 bucks.
Stock LS1 TB of 75-78mm will get you by for now until you can upgrade to something abit bigger for that motor. 50 bucks for a stock TB.

Then you'll need the rail fittings and some -6 an lines to connect to your fuel lines. That may add up.

4bbl type EFI tb is best bet for power unless you use a good designed intake elbow that wont restrict any flow. More expensive to go EFI single plane but its better than a TBI type application


For about 1800 bucks or so, you can have the FAST injection system with FAST EZ EFI ecm/harness. Tunes itself and I've heard it works pretty good.

anesthes

iTrader: (12)

Didn't really think of it that way. so rather than the fuel for each cyl puddling on it's own valve, it puddles in the center and then the valve that opens first gets the huge shot of fuel.. Lame..

This motor won't get boosted, only because the block will break. It has a forged crank, rods, and great pistons however it's a 2 bolt main 400 block. It should make a little over 500hp naturally aspirated. I think if it took boost, or made more than 600+hp the mains would break.

Yep. really, the whole point was I wanted to break the motor in with the RPM air gap intake I have, run it for the summer, than convert it to EFI in the winter using the harness/ecm/stuff I have left over from other conversions. Really, I just didn't want to swap the intake because. well. It's paid for. Normally when I do EFI motors I run the holley singleplane.

That is my only gripe about it. I actually have access to one that has been modified for like.. freeish. maybe $50 or a case of beer. I just can't bring myself to run that remote thermostat setup and have the 5/8" heater hozes running around the engine bay..


Like I said. I just I wanted to run it carb, dyno it, flog it at the track, then swap a wet flow EFI. The combo I'm running - rpm airgap, afr 1040 heads, xr288hr cam makes 505hp on a 383 with 9:1 compression. Like, it was a common mail order mill. I did it with a 412 instead, and brought the compression out to 10.8:1, so I'm assuming thats good for another 50hp and maybe more vac at idle/efi friendly?

I guess maybe the best route, as suggested, is swap the intake, ebay it, and do it the way I've been doing for 10 years.

-- Joe

anesthes

iTrader: (12)

That holley intake with aaron's elbow and the LS1 throttle body I ran on the corvette a few years ago worked out pretty good. I actually saw the car for sale on craigslist last month, guess the owner isn't happy with it.

Truth be told, the one I built a looong time ago with the truck throttle body mounted vertical, and the block of aluminum as an adapter had the best throttle response.

-- Joe

RBob

iTrader: (1)

The issue is the injector firing rate. To ensure proper fuel distribution the injectors need to be fired often. More often then in a batch fire set up. This is why I mentioned how GM does the TBI injector firing rate.

And, GM also uses PnH injectors for a faster opening and closing. This allows more time for spraying fuel then a saturated injector. But this is done because they are being fired more often.

With the injectors under the blades, the progressive linkage isn't an issue. A true TBI such as the Holley this would be. Although the Holley ECM uses the TPS to know when to activate the second set of injectors. So the progressive system works when used with their Commander 950.

TBI systems can be power, but like any EFI system it needs to be set up properly. Which makes me wonder about the FAST TBI unit. I just can't see using saturated injectors in this type of application.

I know of several people using the Accel TBI unit with PnH port injectors being driven by a TBI ECM. And with port PnH injectors having twice the resistance and half the inductance of a TBI PnH injector. The TBI ECM can drive two injectors per ECM driver.

Then the TBI ECM provides the proper injector firing rate. It works. Some are even on super charged engines and they do make power. Just need to set up the EFI with the right parts.

If you are set on using the '7730/$8D combo, then port is the way to go. If you want to use the FAST type TBI unit (or Accel), then PnH injectors and a TBI ECM is required.

RBob.

anesthes

iTrader: (12)

I have the '747 ecm as well, two of them in fact. But then we run into the progressive linkage problem if I go with a holley type 4bbl TBI, in that the '747 cannot disable the other injector driver when the rear blades are closed.

Or do you have a patch for that?

All I was really trying to do was keep the manifold I have. If it's more expensive to do so than it doesn't make much sense.

I suppose, a mechanical connection like a nitrous switch could be used to 'enable' the rear injectors when the throttle arm moves?

-- Joe

RBob

iTrader: (1)

I don't know of a 'fix' for the Holley TBI with progressive linkage used with a '7747 type of ECM. Usually the injector driver upgrade to drive four injectors has two in parallel. If power is cut to one of the two injectors, then the one remaining injector current doubles. Not good for the injector.

Since the injectors fire alternately, shouldn't cut power to the two on one driver as then the fuel distribution gets goofy. Holley gets around this by using 4 individual injector drivers. Although I have known people to run the two normal TBI injectors to fire together on every other plug firing and it worked OK.


The way I handle this on a large 2-bbl TBI (2-1/16" bores), is to extend the linkage so that the pedal has more throw. This reduces the amount the blades open per gas pedal movement. So re-link the 4-bbl for 1-1 front/rear, and change the pedal to TBI linkage ratio.

On a cable type throttle linkage using a snail shell shaped cam on the throttle blade shaft works. This is along the lines of what GM did on the larger TB units. Such as the mono-bores for port injection.

RBob.

Gumby

Good thread so far




but why I never under stood TBI as a performance mod, I think it should be a carb or MPFI, there is no good in between cause of that.

And atleast with a carb its a constant flow or fuel with the air, though you can still have some cylinders rich n lean.

But ill keep reading to see where this goes

RBob

iTrader: (1)

Please take Joe's comment in context. It has to do with using an incorrect injector firing rate with a TBI type induction system. This is not how it is done in a proper set up, which will not exhibit this characteristic.

TBI does provide performance. It is just that so many in the past did not understand how to do this, which piled onto the "TBI isn't a performance system" myth.

I could go on & on about how TBI has been done badly (implementation). And, go on and on about the TBI set ups that provide power and driveability that folks just can't believe. But this isn't the thread for that.

RBob.

anesthes

iTrader: (12)

Right. Point of post was trying to hack something together that was not an intended OE design.


RBob, How do you think this guy is pulling it off:

http://www.howellefi.com/customer/tb...v8-engine.html


An OE TBI would be great, but with the largest injectors available being 85lbs/hr, you can't support 550-600hp with just two.

-- Joe

Gumby

The largest possiable or just made n sold now?
No custom build option from a race shop?

anesthes

iTrader: (12)

Not that I'm aware of but I'm not a TBI expert.

In theory, if the ECM can handle it from idle to 6500rpm, a throttle body with two 58MM bores, and two 180# injectors should handle 600hp no problems. I've never seen such injectors, and am not sure what the limitations are of dealing with the pulse widths on the TBI ecm.

-- Joe

anesthes

iTrader: (12)

What about a vortec L31 throttle body? I've made adapters to run them on 4150 singleplane EFI intakes. What about simply running four injectors aimed at the horn? Or even just four P&H injectors in the adapter plate, just under the blades. Would the '747 with the resistor mode be able to handle the required pulse widths/firing rates of four 454 injectors from idle to 6500 ?

Attached is a picture of the adapter I made in 2004. Had a 1/2" iac passage too, and this thing ran WAY better than the 4bbl progressive mpfi throttle body I replaced it with.

Port style P&H injectors can run into the base, or 4 TBI style in the air horn ?

-- Joe

RBob

iTrader: (1)

Well, they don't provide much information on the system. Although they do say, "Recommended for mildly modified engines." Which means that it is duty cycle limited on the injectors. And if the ECM is a '7749, they could also be using PnH injectors for a faster opening time.

This is what I was saying above, about the injector firing rate. The '7730 can fire all four injectors (saturated) every time a spark plug fires. This will give good driveability, but be RPM limited (severely). Figure at 3200 RPM a plug fires every 4.7 msec. (8-cyl). Takes a saturated injector about 1.2 msec to open. Closing time I am not sure about, say a half a msec. So 1.7 msec to operate the injector, leaves 3 msec (4.7 - 1.7) to spray fuel.

That is equivalent to 12 msec of fuel on a double fire MPFI set up. Which is about what is used at 3200 RPM at WOT.

Once above 3200 RPM, the amount of time left to spray fuel quickly decreases. At 4800 RPM there is only 3.1 msec between injector/plug firings. So, will it work? Yes. Will it work on a performance engine. No.

So, strap the MEMCAL for a 4-cyl MPFI set up. Now the injectors will be fired on every other plug firing. This over doubles the amount of time available to spray fuel. But, at the cost of fuel distribution at low PWs.

At 4800 RPM, there will be 6.2 msec between injector firings. Which opens up the duty cycle limits and allows higher RPM and more fuel to be delivered. At WOT it will work and with properly sized injectors, probably rather well.

But because it is not a proper TBI set up, driveability will suffer.

With the currently available 80.5#/hr GM TBI injectors, 480 - 500 HP is the max with 2 injectors. And even at that will need to run 36 - 38 psi fuel pressure. Which is above the 32 psi that GM ever used their TBI injector pods at.

RBob.

RBob

iTrader: (1)

A stock TBI ECM is capable of driving 4 port style PnH injectors. No mods required. The firing rate will be alternating on each plug firing.

A '7730 ECM is capable of driving 2 port style PnH injectors, or 1 TBI PnH injector.

A '7749 ECM is capable of driving 4 port style PnH injectors, or 2 TBI PnH injectors.

RBob.

anesthes

iTrader: (12)

What about a '747 with your mod?


To do it with a '749 however, you couldn't run $8D could you? Would you have to run $58 ?

-- Joe

Orr89RocZ

iTrader: (20)

FWIW I have the 730 running 8 80lb siemens new style injectors. Saturated type. Idles fine with pulsewidths as low as 1ms. Will idle stable at 18 to 1 air fuel if you wanted to. The newer siemens stuff does well with lower pulsewidths from the injector vendors i've talked to. The LSx guys seem to like them too.

RBob

iTrader: (1)

The 4-Injector Upgrade in a TBI ECM is capable of driving 4 PnH TBI injectors. Or, 8 PnH port injectors. Or an army of saturated injectors.

Running $8D in the '7749 loses the TCC lock up function. Otherwise it is a drop in. The '7730 and '7749 use the same PCB, they are just loaded differently.

RBob.

anesthes

iTrader: (12)

Cool, So if you load $8d in the '749 you can run the 4 port PnH injectors?

Although I'm leaning towards the '747 because I have a few of them, harnesses, etc.

So - whether or not you run 4 TBI PnH injectors above the blades, or 4 port PnH below the blades, the '747 with the injector mod will work properly? (assuming the blades are not progressive in the TBI app)


-- Joe

junkcltr

iTrader: (1)

The 749 ECM is easily upgraded to 8 P&H port injectors.

Using TBI with 500HP requires things to "get exotic" like turning on extra injectors at a set RPM or running goofy fuel systems. If I was forced to use TBI I would go with the extra injectors and set RPM control. No goofy VAFPR and over-taxing injectors with port like fuel pressures.
A stock TBI hampers performance by clogging up the TB with the injectors. Does that Fast TB at least have the injectors external? No matter which system you use with the control fuel squirts for TBI you end up with PWs that could be problematic or a goofy fuel system (reminds me of using FMU with boost). The other thing is the problems of IAT with wet flow and tuning. Take a look at Dimented24x7's thread on going with a MAF on TBI to try and eliminate wet flow problems. The MFPI is plain worth the extra money. TBI is great for trucks and other low HP engines. If you look at modern engines......TBI became extinc t except for people wanting the look of a carb (FAST TBs, etc.)

If you want to go with the TB then I would look into the injectors that Orr mentioned and go with the 749 ECM. Or better yet go with the 427 ECM that does TBI also and can handle the injectors you want. No one mentioned it here, but it seems ideal for your goals. It is also free and he is working on different fueling modes. It is all controll via software so you could to ANY fueling mode you want while it is running and swtiching between them on the fly. It even has unused outputs so you could add more injectors. Really, it is the only setup I would consider running a TBI unit.

junkcltr

iTrader: (1)

Yes, lame. But that is how it works for TBI. That is why they do a high injector squirt rate with smaller injects. That means smaller injectors to work right.

You ended up doing it the way you did it because nothing else performed as well. I question why are you now reverting to a way you won't be happy with when already having the best setup? TBI is one step up from a carb. You have to ask, will you really be happy with that? The average 300-400 HP engine works OK with TBI, but you are well beyond that.

RBob

iTrader: (1)

Yes to running 4 PnH port injectors with the '7749. GM did this with the Quad-4 engines.

You are better off with $8D code then '7747 ($42) code for a performance engine. Or for that matter, $8D over any of the stock-ish GM TBI code.

Driving injectors: the stock '7747 will drive 4 PnH port injectors. Once modified to drive 4 TBI PnH injectors it shouldn't be used for 4 PORT PnH injectors.

Remember, port PnH injectors are twice the resistance of a TBI PnH injector. They also only require half the current before peaking off. Which is why you can't mix up the injectors on a PnH system. They are set for a particular peak and then hold current.

RBob.

woody80z28

iTrader: (2)

You guys really know how to kill a party! I was hoping this idea would work for my ~400hp 80Z28 that is currently carbed.

Since the FAST injectors are modified LS7s and cant be replaced, there is basically no way to make it work? How does the FAST EZ-EFI ECM work then?

anesthes

iTrader: (12)

It probably has more than one injector driver, so rather than all firing it once it varies which get fired when.

I don't think the limitation is the throttle body, it's trying to use a GM ecm to drive it.

As Rbob pointed out, even the holley 4bbl TBI 'commander' ECM has 4 injector drivers vs the 1 on the TPI ECMs.

Junkcltr is right, I've always had success with port so why ruin that now.
I've also ran a converted carb intake, and that ran damn good at the track so nothing I guess is stopping the both of us from drilling and pressing in 8 injector bungs. The RPM air gap has a tall enough neck that creating brackets to hold the fuel rails is easy. We're talking $200 in parts to make it work. A junk 900cfm carb base with the addition of a TPS sensor can be used as a throttle body in a pinch.

-- Joe

woody80z28

iTrader: (2)

I was wondering if an AirGap manifold could be converted...

So it would consist of something like this?
http://www.summitracing.com/parts/EDL-3630/
http://www.summitracing.com/parts/ACC-150836/
http://www.summitracing.com/parts/EDL-3878/
http://www.summitracing.com/parts/ACC-74740/

anesthes

iTrader: (12)

Yes, but I probably would use some generic rails, since those come with mounting clips that are specific to the edelbrock e manifolds.

Probably use a regulator out of a 2.8l camaro or if you wanted adjustability, you could get an aftermarket for around $80.

-- Joe