double pumper bad for road race events?
Dec 14, 2012, 06:33 PM
#1
double pumper bad for road race events?
I need a new fuel pump and i have almost everything in order to build a double pumper for the evo. i do mostly drag races but next year id love to get into road racing. Ive heard that with a double pumper on part throttle or wherever you have the extra pump to turn on, the afrs get all wacky. anyone who road races have any problems with a double pumper?
thanks,
josh
thanks,
josh
Dec 14, 2012, 07:13 PM
#3
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....i have almost everything in order to build a double pumper .....next year id love to get into road racing. Ive heard that with a double pumper on part throttle or wherever you have the extra pump to turn on, the afrs get all wacky. anyone who road races have any problems with a double pumper?......
Last edited by sparky; Dec 14, 2012 at 07:29 PM.
Dec 16, 2012, 05:36 PM
#7
AFRs will get out of line if the fpr cannot maintain the correct rail pressure. This can happen because either the fpr is being overrun, or the return line is being overrun, or the siphon is not drilled out to the correct diameter (or a combination of the three). There are a few ways to deal with it. The lowest budget way to deal with it is to have the second pump kick on when the fuel demand is getting pretty high, e.g., maybe at 10-15 psi. Just need to be sure that the second pump is spinning up fast enough to keep up with fuel demand as boost climbs further. The other way to deal with it is to install an aftermarket FPR and larger return line. Some people who choose to upgrade the supply line will use the factory supply line as the return.
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Dec 16, 2012, 09:39 PM
#8
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It might be a good idea to log AFR's and boost on the primary pump alone up to whatever boost level the single pump starts to go lean.
Once you have determined the boost level at which the primary pump starts to go lean. Then you stage the secondary pump to kick in a couple PSI earlier. If for example the primary pump starts to go lean at 24-25 PSI, then stage the second pump to kick in at 21-22 PSI.
Once you have determined the boost level at which the primary pump starts to go lean. Then you stage the secondary pump to kick in a couple PSI earlier. If for example the primary pump starts to go lean at 24-25 PSI, then stage the second pump to kick in at 21-22 PSI.
Last edited by sparky; Dec 16, 2012 at 09:43 PM.
Dec 16, 2012, 10:15 PM
#9
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I used to run dual 340's on my Buick on an ATR, in-tank, staged double pumper with a billet aluminum Y, and I had the secondary pump activate at about 17 PSI. That is the beauty of having the adjustable Hobbes switch controlling voltage to the second pump. You don't have the second pump kick in until youneed it to: under load, at WOT, high revs and high boost, so your motor's fuel consumption is relatively high. Thus, a larger return line is not necessary.
The larger return, the drilled out siphon, and etc. are only needed under light fuel consumption, part throttle, low boost and idle scenarios, with a setup wherein both pumps are on full time.
I used to road race that Buick some and if you have the activation point setup carefully, then the second pump kicking in should not be a problem. If you heard of the second pump causing "wacky" AFR problems, then those guys have the second pump kicking in too early. If setup properly, it should be almost seamless.
I used to monitor the exact boost level at which the secondary pump kicked in at WOT with a FP gauge right next to my boost gauge. The fuel pressure gauge needle will jump about 1-2 PSI for a split second when the second pump kicks on. And then the needle settled immediately back down to normal.
To adjust the activation point of that secondary pump precisely, you need to be able to check the activation point of the second pump on the fly at WOT. So, I got one of those tiny little pencil sized, Autometer shift lights mounted on the bezzle of my boost gauge. The telltale light was wired go on when a circuit was made across the terminals of the Hobbes switch. This way I could tell exactly at what PSI the second pump would kick in.
I guess that nowadays you could do all that with a standalone, or maybe a Zeitronix. But I didn't have that technology back in those days.
The larger return, the drilled out siphon, and etc. are only needed under light fuel consumption, part throttle, low boost and idle scenarios, with a setup wherein both pumps are on full time.
I used to road race that Buick some and if you have the activation point setup carefully, then the second pump kicking in should not be a problem. If you heard of the second pump causing "wacky" AFR problems, then those guys have the second pump kicking in too early. If setup properly, it should be almost seamless.
I used to monitor the exact boost level at which the secondary pump kicked in at WOT with a FP gauge right next to my boost gauge. The fuel pressure gauge needle will jump about 1-2 PSI for a split second when the second pump kicks on. And then the needle settled immediately back down to normal.
To adjust the activation point of that secondary pump precisely, you need to be able to check the activation point of the second pump on the fly at WOT. So, I got one of those tiny little pencil sized, Autometer shift lights mounted on the bezzle of my boost gauge. The telltale light was wired go on when a circuit was made across the terminals of the Hobbes switch. This way I could tell exactly at what PSI the second pump would kick in.
I guess that nowadays you could do all that with a standalone, or maybe a Zeitronix. But I didn't have that technology back in those days.
Last edited by sparky; Dec 16, 2012 at 10:33 PM.
Dec 17, 2012, 06:42 AM
#10
sparky - Nice job on setting up the double pumper. One question though - no problems with running momentarily lean if rapidly climbing through the boost range, e.g., coming out of a corner off throttle with the engine rpms in the turbo efficiency range, and then stomping the throttle?
Dec 17, 2012, 10:48 AM
#11
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Fred: I keep trying to post replies but am having difficulty with my router and I get disconnected. My experiences with a dbl-pumper were long ago and on a different platform altogether than Evos. My tips are probably no longer relevant.
In the early days of turbocharged EFI cars, tuning was done via EPROM flashes and the GM cars had an ECU with a removable "chip". Burning these chips was usually done on desk top computers with "burning" hardware. Only standalones datalogged and tuned in the car with laptops. We really didn't do data logging back then.
We gauged the tune by looking at the color of the spark plug tips and kept an eye on our fuel pressure gauge and EGT's at WOT. Primitive, and clumsy, I know. Sorry for the OT discourse.
In the early days of turbocharged EFI cars, tuning was done via EPROM flashes and the GM cars had an ECU with a removable "chip". Burning these chips was usually done on desk top computers with "burning" hardware. Only standalones datalogged and tuned in the car with laptops. We really didn't do data logging back then.
We gauged the tune by looking at the color of the spark plug tips and kept an eye on our fuel pressure gauge and EGT's at WOT. Primitive, and clumsy, I know. Sorry for the OT discourse.
Dec 18, 2012, 07:40 AM
#13
You don't need to worry about a drilled siphon pump with our setup, and as long as the regulator and return line are up to snuff you shouldn't notice anything when the 2nd pumps kicks on.
We like to see the 2nd pump come on at just a few PSI of boost so when it really matters (high boost) both pumps are rolling already. The only time you would typically see that low boost transition turn on the 2nd pump is when you're coming out of a corner. The rest of the time should be decel or WOT if you're doing it right ;-)
Andy
We like to see the 2nd pump come on at just a few PSI of boost so when it really matters (high boost) both pumps are rolling already. The only time you would typically see that low boost transition turn on the 2nd pump is when you're coming out of a corner. The rest of the time should be decel or WOT if you're doing it right ;-)
Andy
