LT1guy

iTrader: (1)

My TA has a former TBI motor in place of its original 305 (carbureted), and I want to put the original type mechanical pump back on it if possible (it now has one of those universal electric pumps, installed by the previous owner). Does the TBI cam have a lobe to drive the fuel pump pushrod? I'm betting it does, but just wanted to check before I tear into it. Thanks guys!

dimented24x7

iTrader: (2)

Good question. I think they did, but im not sure. Anyone pull their cam recently?

dimented24x7

iTrader: (2)

The camshaft specs appear to be the same as one for an LG4 so that being I would imagine it has teh fuel pump eccentric as well. This assumes the specs Im looking at are accurate.

25THRSS

I believe so, but I would stick with the electric pump to keep from wasting hp with a mechanical pump.

Stekman

The gains/losses are minimal at best. Either or, your going to lose something. The pump pushrod has the friction on the cams eccentric, sure. The electric adds load to the alternator.

IMO just stick to a good mechanical pump. I have a Carter on my Lg4 in my Caprice. The thing (pump) runs perfectly.

ShiftyCapone

iTrader: (7)

All Gen I cams have a fuel pump lobe. That includes the LO3 cam as well. There is a pic of my LO3 cam in the LT1 cam install sticky that points out the lobe.

Damon

Have a 1992 305 TBI cam in my basement right now. It's got a fuel pump eccentric.

LT1guy

iTrader: (1)

Thanks guys!

25THRSS

The alternator won't work any harder with an electric pump, it will spin the exact same regardless. He already has an electric pump, so why downgrade to mechanical?

Stekman

When the cam lobes present more lift than the fuel pump "lobe", then I will consider it a viable reason to free up hp. Until then, the losses are still minimal. Especially when looking at the fact that it is on a TBI (presumably stock) engine.

Why downgrade? Don't ask me. I am merely giving my suggestion on the assumption that the original poster wants to convert to a mechanical.

JPrevost

No it won't. An electric pump puts more load on the electrical system. Not to mention that the electric pump is running full steam all the time, even at idle. That's 3-5amps depending on the pump and fuel pressure. Running a mechanical pump is by far the best for ANY power savings. Same with the waterpump but that system has more lag so it's a touchy subject. Back to fuel pumps. The mechanical pump is by far the most efficient because it's mechanical energy converted to mechanical energy with very little heat loss. Converting mechanical energy into electrical then back into mechancial is less efficient because of the heat energy that's lost.
I like mechanical fuel pumps because they are directly propertional. Engine revs high, needs more fuel flow, pump is pumping more fuel .
It just so happens that small in-tank electric pumps are by far the most economically priced for street machines but in a race car even with EFI I'd consider a belt driven fuel pump (only if I had the money to burn). But since mechanical pumps off the block for carbs are cheaper than electric pumps for EFI... go for it. It's a smart move.

25THRSS

I gained about 7 rwhp with an electric wp on the LS1. The engine isn't going to work any harder to power an electric fuel pump. It doesn't say, "damn I need to produce more amps so I have to strain myself even harder." It works the same regardless, but with a mechanical pump it must waste hp to turn the cam to push the pump. Friction and weight suck. Besides, amperage is a non issue above idle on pretty much any accessory even with underdrive pulleys.

dimented24x7

iTrader: (2)

I think the power losses from each are negligable.

25THRSS

probably right, you won't gain or lose any huge amount of power, but I was simply saying if you already have the electric, it doesn't make any sense to want to downgrade to mechanical.

JPrevost

You will make more horsepower with a mechanical fuel pump. It's very slight but it's there and yes the alternator will "remind" your engine that it has extra electrical parts. What it sounds like is that you think that an alternator is always drawing 105amps whether it's used or not.... is that your understanding?
I would personally keep the electric pump for a daily driver. Having no vapor lock because of the return style system is always a good thing.
Gaining horsepower by removing the mechanical water pump isn't the same as a fuel pump like I said before. I can bet right now $1000 that I don't even have to bet that your electric water pump doesn't have nearly the same water flow rate as the stock LS1 mechanical pump. Hence reduced cooling capacity on the street and road racing. Hell, if you're only going down the 1/4 mile you're probably better off getting a damn spring and rigging it to supply 6psi of fuel pressure for only one 1/4 mile .
Look at all of the real racing pumps and you'll find mechanical pumps everywhere.
The good thing in this guys case is that the TBI pump is still an "efi" pump of sorts. This means that at the carb fuel pressure (lower) it'll flow a LOT more fuel to support way more horsepower than it could at TBI fuel pressure. I'm guessing the stock pump would be good for 400hp at 6psi.

25THRSS

My meziere electric wp flows 55 gallons per minute. I'll take that $1000 as a money order. Anyways, please explain to me how the engine has to work harder to produce more amperage? It will spin the alternator at the same exact speed regardless of which type of fuel pump you have. Like I said amperage is no issue above idle, even with underdrive pulleys.

dimented24x7

iTrader: (2)

Its not the speed, its the drag. When there is a load there is a torque that resists the engines rotation. The more current, the more drag there is and the more work the engine has to do to meet that load.

JPrevost

You think 55gpm is more than a stock pump
Stock chevy waterpumps flow 60gpm and stewart components pumps flow about 120gpm. I've had it blow off my upper radiator hose twice now! Belt driven pumps flow over 180gpm and are extreamely efficient. When can I recieve my $$$$. I accept paypal .
Oh, and just a heads up about the rating of electric water pumps (since I test a bunch of them)... they don't flow as much at they say they do because they aren't tested under pressure. Those ratings are usually free flowing to make you feel like it's sufficient. The instant you put an engine, radiator, and thermostat into the loop the pressure drop increases making it harder to pump resulting in higher amp draw and lower than rated flow.
The Meziere pump I tested was for a SBC at rated at 35gpm. With the upper radiator hose going into a bucket on a scale I reported 10amps at 13.6v and only 26gpm with the thermostat propped open. Granted if you've got a pump control circuit installed you can PWM the motor and run no thermostat resulting in again, 10amps of drag but a much higher 32gpm, still short of those damn ratings.
A stock Honda F4i 600cc motorcycle mechanical water pump flows more!!!
My point is don't go thinking just because it's electrical that it's freed up all kinds of horsepower. It's only moved it to a different kind. I'd go with an electric water pump on my car anyday if it wasn't daily driven so don't get the impression I'm biased. I just want to edjucate you and the rest of the thirdgen community about the differences.

About alternator drag, amperage is drag, drag as in costing your engine horsepower that would otherwise be put to accelerating the vehicle. If the alternator is having to support a large electrical load it is harder to spin! The only thing proportional to alternator speed is the horsepower needed to accelerate the internals. Ever pick up an alternator... it's not exactly light and the majority of that is having to be accelerated where in a mechanical water pump has just an impeller to accelerate.

I've done the math and my senior design for engineering was the cooling system on an FSAE car that had no cooling fans. The study took me 9 months so please don't argue.
Not that I need even more examples but look at the mechanical belt driven fuel pumps vs the electric fuel pumps.

LT1guy

iTrader: (1)

If this was a decent electric pump, like a Holley or Aeromotive or Carter, I'd agree, but that isn't the case here. The car has some cheap Autozone universal electric pump that is mounted in the engine compartment, and has several problems. One, its location makes it so that the car can't be parked with the front end higher than the rear...let the car sit for even a few hours, and it won't start. The helper pump can't overcome gravity and that the system is bleeding down. Sure, I could re-mount the pump at the rear, and run a power lead back to it, but that would be a pain. Besides, the main problem is that its too much pressure for the stock motor to handle...it will flood out and die in heavy traffic. Even if I put a regulator on it, the problem of it losing its prime (its very sensitive to how much gas is in the tank too,far more than any car I have ever seen) is still there. For this car, which is currently otherwise stock and is driven occasionally but about to be completely re-done in the next few months, its doesn't make sense to rengineer the fuel system, or buy a bunch of parts that won't be used later. Putting the stock mechanical pump back on makes the most sense, considering cost, time , and reliablity. I actually prefer electric pumps on modified vehicles, and this car will be getting a good one later, but since the whole fuel system will be changed by then (cell, braided lines, etc) and for a much higher HP level, none of the components would be sutiable now.

25THRSS

I still don't understand how the alternator will be harder to turn. There is nothing that will make it harder to turn. The crank speed controls the alternator. Explain exactly how the alternator will become harder to turn? The LS1 gained 7 rear wheel hp with the addition of an electric pump only, not to mention I can cool the car in the staging lanes much better than a mechanic pump. I drive this car every day to work as well.

dimented24x7

iTrader: (2)

Hmm... Easy way to explain it...

Lets see if I can explain it without getting it all wrong.

In order to induce a current to flow when there is a load on the alternator, a force must be exerted on the free electons in the coils contained in the alternator. This translates into a torque on the alternators input shaft. The larger the load and the more current that can flow, the more torque itll take to turn the alternator. Now, torque times angular velocity equals power. The more torque on the alternator, the more work that must be done by the motor at that speed to turn the alternator. After all, that power must come from somewhere. It jsut doesnt appear out of the sky. It comes from the engine being forced to turn the beltline in order to drive or idle. The reason it continues at the same speed is that either you have the accelerator pressed down or the computer is opening the IAC to maintain the proper idle speed.

A good example of beltline drag and parisitic loss is turning on the airconditioning in a crappy 4 banger. The engine has a harder time accelerating because it must do work in order to turn the A/C compressor and compress teh refrigerant. The same thing happens when a cooling fan or fans turn on and the rpms drop a little bit at idle. Its due to the current spike from the accesory turning on and further loading the alternator. The engine speed falls when it has to convert over some of its power to make electricity rather then use it to maintain the idle speed.

dimented24x7

iTrader: (2)

The reason you gained power is due to the fact that there is less power lost to operating an electric pump vs. an actual waterpump. I imagine at 6000+ rpm a standard pump probably gets pretty hard to turn due to it spinning so fast.

This isnt a problem with an electric motor as it jsut operates at one speed. This can be a disadvantage, however, because at high engine speeds a mechanical pump may be able to circulate more coolant then an electric can.

dimented24x7

iTrader: (2)

This reminds me.

Way back when I remember seeing an article on one of those dB drag competition vehicles that was stuffed with subwoofers and amps. The thing could generate sound levels something like around 180 dB.

Anyway, it was an Astro van with a slightly modded 4.3L that had been fitted with bullet proof glass, heavy duty seals, lots of other crap and something like 4 or 5 chain driven alternators to power all the amplifiers. When the sound system was going at full blast, they had to run the motor at WOT just to generate enough power to run everything. The power used was something on the order of 170 HP, or around 126 kW, which was jsut about the peak power output of the motor. Now, if thats not proof that it takes power to turn an alternator, I dont know what is

JPrevost

What dim said.
Also like I was trying to say, for drag racing an electric pump is good, road racing and high revs it's bad. For a really mild street driven car it can work well too because it flows a constant rate unlike a mechanical pump. The LS1 gained rear wheel horsepower at peak power but it lost power at lower engine speeds. This is because the electric motor is drawing a constant amount of power completely independant of the engine speed. I like mechanical pumps for street and many forms of racing, drag racing and low mile street cars could use an electric water pump. For a carb, the fuel delivery is proportional to engine speed (faster the engine, faster the pump) this is a good think with a carb and EFI. Expensive electric fuel pump controllers use pulse width modulation to control the fuel flow so as not to draw excesive power at lower engine speeds!

25THRSS

Actually, no it didn't, nowhere on the graph did it lose power. There are many circle track guys using the electric pump as well. Like I said, I drive this car every day to and from work, as well as play all the time. This 500+ hp car is not driven lightly. Do I think it is really worth it for the money, no, but it's a proven modification. Besides, the gain in hp, the biggest advantage I saw was the ability to cool the car in the staging lanes.