[HWYSTR455]

Originally Posted by 78w72

the robbmc pump runs great in all conditions... except for hard launches with traction at the track running into the mid to low 11s...

OE replacement and some Carter mech pumps do that. What makes that sufficient?

There's a problem if you can't have it with no 'except' conditions.



Yes Tom, understand, pump controllers that use PWM and voltage varying methods are more efficient, and will make pumps last longer, depending on the pump of course. Those methods require a certain type of pump that is capable of varying voltage, it has to be linear, and granular. And that makes the pumps much more expensive.

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[78w72]

Originally Posted by HWYSTR455

OE replacement and some Carter mech pumps do that. What makes that sufficient?

There's a problem if you can't have it with no 'except' conditions..

not sure i understand that statement... OE replacement & carter mech pumps wont run low 11's in heavy mostly street cars with lacking suspensions. granted more race inspired & F.A.S.T. guys might do that but they have a lot more going on that isn't considered standard street equiptment.

i agree there is an 'except' issue with going that fast with mechanical pumps, but the majority of the 'problem' is what i described above & cliff has talked about numerous times... at some point of power & e/t, a mech pump just cant keep the fuel supplied sucking through 20ft of line under hard g-forces. an electric pump back at the tank can do it much easier pushing the fuel & having a proper return set up.

for now im more than happy with the times the car runs at the track given its combo. & am still amazed how well it does on the street with 89/91 fuel.

would love to hear examples of someone at those times with a mech pump that uses a smaller pusher pump to assist or fix a fuel starvation issue with just the mech pump.... ive been on here for a long time & cant really recall anyone doing that or seeing it in hot rod magazines or in use at my local track.

[Tom Vaught]

You might want to read this article.

http://saac.memberlodge.com/resource...3-flawless.pdf

The 427 Ford Shelby Cobra used a Mechanical Fuel Pump and a pair of small pusher pumps in Production.
Cobras could run mid 11 second times.

It used two of the Stewart Warner 240A Electric Fuel Pumps to feed the fuel forward to the Mechanical Fuel Pump.

At one time between the late 1950s and the middle 1970s, these were the fuel pumps to run as "pusher pumps" for the competition engines. Unfortunately compared to todays fuel pumps they are very small in fuel flow capacity.

I had one on my 64 GTO early on in its life. At the time they were the best that you could get.

Tom V.

[78w72]

Originally Posted by Tom Vaught

You might want to read this article.

http://saac.memberlodge.com/resource...3-flawless.pdf

The 427 Ford Shelby Cobra used a Mechanical Fuel Pump and a pair of small pusher pumps in Production.
Cobras could run mid 11 second times.

It used two of the Stewart Warner 240A Electric Fuel Pumps to feed the fuel forward to the Mechanical Fuel Pump.

At one time between the late 1950s and the middle 1970s, these were the fuel pumps to run as "pusher pumps" for the competition engines. Unfortunately compared to todays fuel pumps they are very small in fuel flow capacity.

I had one on my 64 GTO early on in its life. At the time they were the best that you could get.

Tom V.

great article & i love cobras! i was waiting for an extreme example like that... while that's awesome they can run 11's with a mech/elec set up, cobras are not what i would call a normal or heavy street car like i mentioned above, they are basically a factory backed race car.

i dont plan to add an electric carter pusher pump, just curious if anyone at this power & time level has used one successfully with a stock type mech pump.

[Tom Vaught]

PM to You, 78w72

TV

[HWYSTR455]

My point was that you step up to a 550 or 1100 pump and still have the same problems other mech pumps have, what's the point of upgrading? If a pump is rated to a certain HP level, it should support that under whatever circumstances. And yes, the Carter pumps did get cars into the 11s. And heavy cars at that.

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[TAQuest]

Originally Posted by HWYSTR455

My point was that you step up to a 550 or 1100 pump and still have the same problems other mech pumps have, what's the point of upgrading? If a pump is rated to a certain HP level, it should support that under whatever circumstances. And yes, the Carter pumps did get cars into the 11s. And heavy cars at that.

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Exactly!

Crazy that folks are adding pumps when they are not needed.

What will it take to get them to fix it right?

I'm guilty of doing that too. Sometimes I can go 10 years being a butthead and not fixing something right. Stubborn and paying for it.

[78w72]

Originally Posted by HWYSTR455

My point was that you step up to a 550 or 1100 pump and still have the same problems other mech pumps have, what's the point of upgrading? If a pump is rated to a certain HP level, it should support that under whatever circumstances. And yes, the Carter pumps did get cars into the 11s. And heavy cars at that.

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i didnt really "step up" to this pump, i did a stroker motor build on a pretty tight budget ~5 years ago for this car that is 90% street & i didnt expect it to run this fast at the track so a big bad electric fuel system wasnt in the plans or budget. not everyone can afford the best or see the future when building a car.

at that time tanks inc was around but very few people on this forum/section had used them or posted about using them & the current drop in pump modules weren't around or popular yet. so, i used the edelbrock mech pump rated for 'up to' 600hp that i had with some parts i bought & it worked "ok", got ~520hp on the dyno but the car was stuck in the low 12's & was fuel starved still.

so fast forward a couple years & i found a new but never installed robbmc1100 for a very good deal, so i thought that was worth $150 to try it out, being still on a budget, & it proved to be a step in the right direction & with no other changes the car was doing mid 11's. got some new m/t drag radials & dropped another almost .5 off the et & best so far is 11.2x & have gone 123 mph. this with a soft launch off idle & shifting around 5200, i know there is more in the car if i can address the traction/launch issues. the car has a mild auto-x PTFB suspension on it so the stiff springs & no traction aids really hurt its weight transfer & traction, with proper traction id be in the high 10's.

so with all that said, i still dont think or know of any carter or OE mech pump that will run a heavy street car with a suspension not set up for drag racing to consistent low 11's at that mph. im sure someone has done it, but its not a common thing that you can claim OE type pumps can do that on any type of regular basis. if that was the case we would all be running a carter mech pump into the low 11's & high 10's & electric pumps wouldnt be needed at this power & et level.

as for pumps supporting the power they claim under whatever circumstances, you should take that up with robbmc, he will explain what i said in that pumps are rated standing still on a bench, their power ratings dont apply to actual drag racing situations, if that were the case the 550 pump would suppply most the cars in here that run these times, & we all know thats not the case.

[TAQuest]

Just checking the theories here;
So if you have 1/2" tubing leading up to a robbmc1100, not funny cobbled lines with too many bends and splices, and 1/2' tube up to your carb, it's not going to be enough fuel to run just about any Pontiac through a full quarter mile?
If that's true then I definitely am learning something today because it doesn't make any sense on paper volume wise.
The numbers show that you would have plenty extra fuel. What is exactly going on with this? Is it the carb? Because the pump and lines can be predicted with math. Something isn't adding up.

[ta man]

Originally Posted by TAQuest

Just checking the theories here;
So if you have 1/2" tubing leading up to a robbmc1100, not funny cobbled lines with too many bends and splices, and 1/2' tube up to your carb, it's not going to be enough fuel to run just about any Pontiac through a full quarter mile?
If that's true then I definitely am learning something today because it doesn't make any sense on paper volume wise.
The numbers show that you would have plenty extra fuel. What is exactly going on with this? Is it the carb? Because the pump and lines can be predicted with math. Something isn't adding up.

Mechanical pump pulling a huge wall of fuel against g force.

[TAQuest]

Originally Posted by ta man

Mechanical pump pulling a huge wall of fuel against g force.

Nope. The physics doesn't support that theory. Not anywhere near enough G force. Maybe inside the carb or fuel tank, not in the lines or pump.

Must be something else.

[HWYSTR455]

I hope I wasn't taken as being pissy or anything, not my intentions, I jump back and forth here to comment, and don't always have the time to phrase things in a PC manor. Apologize for that.

It's not just what it will run at the track, keep in mind, the psi also combats vapor lock, as well as better supply under g-forces. (such as a hard launch or hard cornering). You can still suffer deficiencies even if you don't feel it.

You step up to a 'performance' fuel system, and you will be surprised what improvements start popping up.

You can add a pusher pump, but it also adds a layer of complexity that can make troubleshooting more difficult, and by the time all is said and done, you end up spending more money than if it were done 'right' to begin with. Sure, people do it, and are successful, but again, many don't realize what they're missing until it's recovered.

A fuel system is one thing that should be over-engineered. Design it to a level you know you will never attempt to reach, it gives you room to grow, and lower duty cycle makes it last longer.

You can do it to where it doesn't detract from the OE look either, like you can gut a mech fuel pump and run an in tank pump, hide the regulator somewhere and done.

That would be cool if someone came out with a mech fuel pump that was actually a regulator. That would satisfy all the folks who want it to look factory.


.

[HWYSTR455]

Originally Posted by TAQuest

Nope. The physics doesn't support that theory. Not anywhere near enough G force. Maybe inside the carb or fuel tank, not in the lines or pump.

Must be something else.

Well, kind of true. I've seen where folks step up line size with a working system, only to find out the volume is suffering. That column of fuel is a factor, how much, not sure, but believe it's more a matter of volume.


.

[TAQuest]

Originally Posted by HWYSTR455

I hope I wasn't taken as being pissy or anything, not my intentions, I jump back and forth here to comment, and don't always have the time to phrase things in a PC manor. Apologize for that.

It's not just what it will run at the track, keep in mind, the psi also combats vapor lock, as well as better supply under g-forces. (such as a hard launch or hard cornering). You can still suffer deficiencies even if you don't feel it.

You step up to a 'performance' fuel system, and you will be surprised what improvements start popping up.

You can add a pusher pump, but it also adds a layer of complexity that can make troubleshooting more difficult, and by the time all is said and done, you end up spending more money than if it were done 'right' to begin with. Sure, people do it, and are successful, but again, many don't realize what they're missing until it's recovered.

A fuel system is one thing that should be over-engineered. Design it to a level you know you will never attempt to reach, it gives you room to grow, and lower duty cycle makes it last longer.

You can do it to where it doesn't detract from the OE look either, like you can gut a mech fuel pump and run an in tank pump, hide the regulator somewhere and done.

That would be cool if someone came out with a mech fuel pump that was actually a regulator. That would satisfy all the folks who want it to look factory.


.

Doesn't seem to be vapor lock either.
What is being described is at full volume fuel flow and that is also cooling.
Vapor lock would more likely be happening at low flow where you can create some vapor with slow flow of fuel.

[TAQuest]

Originally Posted by HWYSTR455

Well, kind of true. I've seen where folks step up line size with a working system, only to find out the volume is suffering.


.

I have worked in manufacturing with hydraulics and bigger lines never hurt volume. They just make the flow easier. GM sent me to hydraulics school so I learned a great deal about pumps and lines.

[Tom Vaught]

When people add a 1/2" line to a suction side of the Mechanical Fuel Pump fuel system, the greater weight of the fuel in the line, under acceleration, actually just keeps more fuel from being able to be pushed forward by atmospheric pressure. The Atmospheric Pressure does not change entering the tank.

The Pusher Pumps: (RMP (Rear Mount Pumps & EFI Pumps) all push the fuel forward to the engine. They can push a lot more fuel thru a 3/8" fuel line at 20 psi vs trying to suck fuel thru a 1/2" line where the "PUSH" (Atmospheric Pressure) does not change.
The surface area on the top of the fuel remains the same.

Tom V.

[ta man]

Originally Posted by TAQuest

I have worked in manufacturing with hydraulics and bigger lines never hurt volume. They just make the flow easier. GM sent me to hydraulics school so I learned a great deal about pumps and lines.

Well make me a believer. As my highschool math teacher would say" show your work".

[Tom Vaught]

Originally Posted by TAQuest

I have worked in manufacturing with hydraulics and bigger lines never hurt volume. They just make the flow easier. GM sent me to hydraulics school so I learned a great deal about pumps and lines.

Truth but most hydraulic machines are not trying to accelerate down the race track with under 1.6 60 ft times, lol.

In a static world the fuel line could be 2" in diameter and the fuel pump would just have a closer volume to draw off of.
Think Smokey Yunick and his fuel line driving home with no fuel tank in the car.

Tom V.

[78w72]

Originally Posted by HWYSTR455

I hope I wasn't taken as being pissy or anything, not my intentions, I jump back and forth here to comment, and don't always have the time to phrase things in a PC manor. Apologize for that.

It's not just what it will run at the track, keep in mind, the psi also combats vapor lock, as well as better supply under g-forces. (such as a hard launch or hard cornering). You can still suffer deficiencies even if you don't feel it.

You step up to a 'performance' fuel system, and you will be surprised what improvements start popping up.

You can add a pusher pump, but it also adds a layer of complexity that can make troubleshooting more difficult, and by the time all is said and done, you end up spending more money than if it were done 'right' to begin with. Sure, people do it, and are successful, but again, many don't realize what they're missing until it's recovered.

A fuel system is one thing that should be over-engineered. Design it to a level you know you will never attempt to reach, it gives you room to grow, and lower duty cycle makes it last longer.

You can do it to where it doesn't detract from the OE look either, like you can gut a mech fuel pump and run an in tank pump, hide the regulator somewhere and done.

That would be cool if someone came out with a mech fuel pump that was actually a regulator. That would satisfy all the folks who want it to look factory..

wasnt taken pissy at all, you are one of a select small group of members here that i value your opinions & trust your advice. was just trying to reply to your comment about OE type pumps doing what a robbmc 1100 can do, majority of OE or carter pumps wont support the power a robbmc will. another thing to consider is tank design on some cars, under a hard launch the fuel will be pushed to the back of the tank & uncover the pickup or aerate the fuel even at 1/2-3/4 tank. on my 2nd gen firebird thats not as big of a problem but i still run 3/4 tank to be sure. but without a doubt an over engineered elect fuel set up is best, i just didnt have that in the budget on the initial build but am leaning towards that if i want to keep going faster.

on this car im not too concerned with looking factory, the main limitation was $$$ for going top of the line with everything, im sure you know but building a car from the ground up takes a lot of money & trying to keep important areas strong enough to handle the engines power like the driveline had more importance than the fuel system, at least for the first phase to get the car on the road/track. i will play with what i got a little more for now, but am prepared to go intank elect in the near future.

thanks for the input

[78w72]

as for the guy claiming he knows everything about fuel systems because he worked in hydraulics 40 years ago, as usual you dont have a clue! talk to any of the fast guys on here, including the fuel experts like cliff or even robbmc & you will learn that G-forces play a huge roll in fuel delivery... in the lines! & a mech pump can not pull fuel as well as a elect pump pushes fuel. funny how you talk about "doesnt make any sense on paper" but whenever people told you about the RV cam you have & your detonation issues, you tell everyone they are just guessing on paper & you are the expert in the real world! LOL!

untill you have a car that can run these times with this power, please, kindly keep your delusional opinions to yourself. & put me back on ignore like you claimed you did but still keep replying to my comments.