An opinion on in-tank double-pumper setups.....

[Blazer406]

Take it for what it is worth..... as it is only my opinion.

A in-tank double pumper setup is a bad idea.... and is a hurt motor looking for an opportunity.

I bet I have your attention now......

I have been helping with a friends car for several years. We have been running an intank double-pumper setup but have had several issues with the system over the past couple seasons. We sumped the stock tank at the 1st of last year and bought a large Weldon external pump and setup to put on when we got around to it. We were still running the double pumper setup when we went 9.4x's @ almost 147 mph with the car in Reynolds in the fall of 2010. I got to thinking about what would happen if the second pump failed.

Look at it ths way..... a single 340 is (by my definition) marginal if you are running bottom 10's w/o alky to assist in the fueling. If pump #1 s good for say 600 HP.... and you are making 900...... when will you know you have an issue with pump #2? If your luck is anything like ours, I can tell you it will be after 1/2 track when all the pistons are beginning to melt.

My point is this.... with a big single pump..... at least if it quits.... the car will not run. When you are running a DP setup..... it will run fine until it goes way lean but won't quit.... cause you got a good pump giving you 600 HP worth of fuel.

I would expect to get some flack from the die-hard DP fans.... but prove that what i say isn't the truth......

Just thought I would plant the seed for people considering a DP setup but have not thought about how it works....

IMHO, with the new bigger in-tank pumps out there...and a Razor's alky kit.....you should be able to safely get well into the 9's with one in-tank pump. If you need to go faster than that..... step up the entire fuel system with something like a 2015 Weldon and a sumped tank.

HTH Somebody.

 

[KevinB]

No different than alky injection...

I run my pumps at the same time all the time. Also run them off the same relay/power wire. If one pump is dead, I will have an issue at idle with fuel pressure.

 

[Blazer406]

No different than alky injection...

I run my pumps at the same time all the time. Also run them off the same relay/power wire. If one pump is dead, I will have an issue at idle with fuel pressure.

Please explain.

IMHO, if one pump is running and the other is supposed to be running (at the same time) ..... the idle FP should be satisfied with the one pump running. I don't understand how you might know the other one was not on......... or possibly... if it was running... but something was physically wrong preventing it from making pressure or volume at pressure.

 

[KevinB]

Maybe it because of the big -10 feed and the small return. It loses 3-5 psi at idle with one pump.


Explain to me though what the difference of relying on a second pump or a pump flow Meth. I bet more engines/head gaskets have been hurt with poor Meth distribution than double pumper failures.

 

[2QUICK2B6]

out side fuel pressure gauges help ALOT ! cheap insurance

 

[Blazer406]

Maybe it because of the big -10 feed and the small return. It loses 3-5 psi at idle with one pump.


Explain to me though what the difference of relying on a second pump or a pump flow Meth. I bet more engines/head gaskets have been hurt with poor Meth distribution than double pumper failures.

In a system that has alky ....and you count alky as the 2nd pump...... not much at all..... except if you loose the fuel pump... it probably won't run on the alky alone..... no more than is squirting in there...... but good point. Alky wouldn't be spraying unless in boost.... so at idle.... the car would die if the fuel pump died..... no?

In your case where you do have a 5/8" fuel line coming in and small return line..... maybe it does offer a small difference in idle fuel pressure..... but to your argument.... if your return line is adequately sized.... you probably wouldn't see the drop in idle pressure when only on one pump.....

 

[Steve]

There are dozens of things that can go wrong and kill a motor so I always come back to the the audible knock detector. That way if anything goes wrong there will almost always be some knock and I can lift and investegate the problem.

 

[KevinB]

At wot, what happens if your alky pump hiccups? What if your fuel pump dies? What if you hit a fuel cut off in a chip? Melted parts.

My point is, you can not call a double pumper dangerous but consider an alcohol system safe in the same post. Both rely on 2 pumps. If one dies, inadequate fueling takes place.

 

[KevinB]

There are dozens of things that can go wrong and kill a motor so I always come back to the the audible knock detector. That way if anything goes wrong there will almost always be some knock and I can lift and investegate the problem.

relying on the knock gauge is not always the best thing. A lot can happen before it sees anything.

 

[Daniel Jost]

what if.... what if... what if....

What if your trans fails and your engine over revs and scatters...

What if your manifold pressure line comes off or breaks causing overboost/low fuel pressure...

What if the throttle sticks and at the same time you cant get the ignition shut off....

Lets face it in any aftermarket part there is a high risk for failure, so unless your driving a bone stock GN (And not even then) there is a chance for failure its just a chance you take with any mods on these cars...

,Dan

 

[Steve]

relying on the knock gauge is not always the best thing. A lot can happen before it sees anything.

I know its not the best because there really isn't a best way to prevent failure but in most cases there will be detonation before a disaster. Gauges in general are not good for catching problems during a run because you can not stare at all of your gauges for the entire run so I like the audible part because you can be alerted to a potential probelm without having to see it. There is no way to make a car blow up proof so you just have to do your best to maximize your chances of cathcing a problem when it occurs.

 

[TurboBob]

part of the issue is knowing where the weak links are.... and doing what you can to ensure they are properly maintained.

Gauges, knock or otherwise, help to tune the combination. If something gives up, gauges won't help much.

The higher the power, the more sensitive to fuel/octane failure.

I even wonder on the 'single pump is better than two' discussion if the one pump in question couldn't fail partially, causing the same issue.

Bob

 

[KevinB]

I even wonder on the 'single pump is better than two' discussion if the one pump in question couldn't fail partially, causing the same issue.

Bob

Especially on the voltage sensitive pumps. Your alt takes a dump, pump takes a dump too. Have seen a few cars get hurt over that.

 

[TurboBuRick]

Pros and cons no matter what. It's a valid point. No doubt it can happen. That's why you have to be on top of your stuff. Data logging is key. Bob said it. Know the weak links. Watch them closely when pushing the envelope.

Kevin makes good a good point as well. I can say from experience, alky pumps fail. They only last a couple years at best. Two things that happen. The pump looses pressure or fluid leaks/pumps out on the ground. Either way you don't know. From the cockpit, lights are on, alky appears to be working. Unless your monitoring/logging alky pressure you can't say for sure whats happening.

One other flaw in the alky system is the tank. By design the fluid flows away from the pickup when the car is pulling . The faster the car, the more G's, the more the fluid is pulled away. That's something to think about. All alkyholics, keep your tanks full check your system pressure often.

Nothing can be taken for granted. We have come a long way with these cars. We push them hard and we get away with it. Until one day something goes wrong and we have to point the finger. Was it fuel? Alky? Octane? Or?

Sorry for getting a little off topic but felt it to be relavent.

RL

 

[Blazer406]

In our particular case.....we were using alky only for cooling......not fuel.....so it was only injecting a small amount......only enough to cool the charge air off due to our less than optimal airflow across our intercooler....which wasn't getting the job done..... Anyway.....if our alky pump failed.....the WOT closed loop correction would compensate for the lack of alky flowing. In our particular case.....it would make no difference.

Now if we were in the middle of a 9.4x pass and lost one of the 340's....... we would need a dustpan to pick up all the pieces.

 

[Blazer406]

out side fuel pressure gauges help ALOT ! cheap insurance

IMHO.... on a mid 9 capable car........ things are happening so fast.... I'm not sure you can watch a hood-mounted fuel pressure gauge even if it was the size of a monster tach.

I would agree that for troubleshooting....a fuel pressure gauge is great.

 

[Grumpy]

Sounds like just a case of the woulda, coulda, shoulda's" **** happeneds.. Especially with faster cars.. Nature of the beast

 

[Blazer406]

There are dozens of things that can go wrong and kill a motor so I always come back to the the audible knock detector. That way if anything goes wrong there will almost always be some knock and I can lift and investegate the problem.

I too am a fan of an audible knock gauge. I have one on my own car....but we didn't have one on the IROC (XFI) . I have thought about installing a stock knock sesnor just to hook an audible knock gauge to.

 

[TurboBuRick]

Always use to think you had to have a knock gauge or alarm. I have not had either for 4 years now.

RL

 

[KevinB]

Always use to think you had to have a knock gauge or alarm. I have not had either for 4 years now.

RL

Same here. I check plugs after each run and go over data logs.