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Proper fuel pressure under wot??

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Old Jan 20, 2006 | 03:28 PM
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Default Proper fuel pressure under wot??

Are there any set #'s on a minimum fuel pressure you should have while under WOT?? My car idles at 60-61 psi {autometer cobalt gauge with sender taped into fuel rail} but it will drop off to low 50's at 3kish under wot. havent been any higher in powerband yet due to bad clutch. but i have a tnt nitrous kit installed now and im just wandering some basics on what an ls1 should have for fuel pressure under WOT and WOT with spray. I have a fuel pressure switch but have no idea how low my psi has to be to close the circuit?? The car also has a thirsty 236/230 cam. would these be grounds for a better fuel pump?? Im just a lil leary of the drop in pressure on just motor without feeding the fuel solonoids yet If i get some free time ill pull out the safety switch and put pressure to it on the bench and see what its set up at. Id like to be as safe as i can when using the juice
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Old Jan 20, 2006 | 04:33 PM
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Having the system loose 10psi without recovering is not good. I would be replacing the fuel pump. I think TNT jettings are rated at 50-55psi, it should say on your jet card. I try to run 55+psi.
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Old Jan 20, 2006 | 05:11 PM
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I know for the vette guys a adjustable reg and return line at the rails will help a lot in the high demand area of fuel consumption. i agree, dropping 10psi and staying there is asking for trouble. check, fuel filter, pump, return system and the such, a pump my be needed, or something as simple as a hot wire kit can help a pump as much as 20% in maintaining press/volume.
Robert
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Old Jan 21, 2006 | 08:20 AM
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ok, the car is an 02 with 35k miles. i changed the fuel filter at 30k. i think ill just need the bigger pump if i should be able to retain 58-60 psi at all times?? I can only imagine how bad it will fall off when the fuel solonoids start drawing off it too!!
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Old Jan 21, 2006 | 09:09 AM
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With a walbro pump and hot wire kit your see about 62psi, would probrably drop to 58-60psi on the bottle. You could get away with just a Walbro but you might as well stick in a Hot Wire kit at the same time. Racetronix sells the whole set up in a plug and play set up, it's pretty nice and priced decent.
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Old Jan 21, 2006 | 11:21 AM
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http://www.harrisspeedworks.com/shop/home.php?cat=330

mine only drops to 58psi and usually idles at about 63psi. upgrade fuel pump kit should be done regardless.
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Old Jan 21, 2006 | 12:15 PM
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ok good deal
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Old Jan 21, 2006 | 01:52 PM
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On most of the cars I tested the LSx non-return style system looses 6-10PSI under load. I have tested about a dozen or so cars
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Old Jan 21, 2006 | 05:01 PM
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would that be safe to be spraying nitrous with low 50's on a 100 shot??
and down the road i might try a 200...either way ill just have to get a bigger pump that can maintain atleast 58# at all times.. would injectors be causing me to loose psi too??

Ive also got a bunch of braided line and fittings laying around.. would #6 AN fuel lines be overkill??
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Old Jan 21, 2006 | 05:39 PM
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Originally Posted by TwoFast4Lv
On most of the cars I tested the LSx non-return style system looses 6-10PSI under load. I have tested about a dozen or so cars
I know that's true on the vettes. The stock Walbro can support 550hp easily, but you do get pressure loss under heavy load. The answer is moving reg and return line to fuel rails. Racetronics has a new reg to replace pulser and line in a kit. Supposed to be out by know but after they posted this, they quite talking of it. You can always use GM rails/reg from 97/98, which I will be doing one of these tricks for mine.
Robert
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