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Bracket Talk Bracket Talk Forum Tech Talk - by Abruzzi Racepak carb pressure...graphsGo | New | Find | Notify | Tools | Reply | |
| Racepak carb pressure...graphs | Login/Join |
| DRR Sportsman |
Here is a single run graph.  Unfortunately i didn't have the af connected. That would have been good to see. Again what pressure are you guys running? My system is only year old. New filter, old filter looked clean but change it yearly. Lines run from rear bottom of cell, pump is fed with -12 about 2 feet of line, then to front -10ptfe line, feeds regulator, and two lines to carb about 3feet away from carb. Pressure gauge comes off the rear line feeding carb per pro system. Per him both should be the same. Regulator doesn't have port for pressure that he supplied. When his SV1 wouldn't perform, i sent it back and paid/kept the regulator. Checked with APD and they said it was fine. Think it's a holley. Just checked with APD and they said set it at 9psi and DONT put it any lower or it will run the bowls low. They said with belt driven systems they run them up to 12psi but you cant with an electric pump or it will flood at idle. Looked up my order and repeated to me keep it at 9.6 psi if that is what the car has been running, the .6 doesn't matter between the gages. I agree with you all though it should be more stable. APD said the system is more than adequate for supply and its probably just the needle opening and closing...This message has been edited. Last edited by: ski_dwn_it, | |||
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DRR S/Pro |
I only run 6.5-7.5 on alcohol. SBC no big wheelies and only 1.22 60' foot feeding it but have never had big swings like you show. I have the tank in the rear and big top Holley regulator.  ____________________________ 2017 and 2018 Osage Casinos Tulsa Raceway Park No-Box Champion 2018 Div4 Goodguys Hammer award winner | |||
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| DRR Sportsman |
Do you have the vacuum port on the regulator hooked up? | |||
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| DRR Sportsman |
There is a hookup, but it is not hooked up.This message has been edited. Last edited by: ski_dwn_it, | |||
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| DRR S/Pro |
Couple of thoughts... The pressure spike up after the launch is not normal, it should drop somewhat,, obviously the floats are moving all over the place here so its likely that has something to do with it. Maybe your bypass at the pump or fuel line routing could also be causing some of this. With a carb and alky, the first question is how much power do you have. APD knows what that are doing but I do feel the lower you can run the FP the better without draining the bowls so I'd keep lowering it until you see issues just so you know where that point really is. When I ran an alky carb I used an electric pump but also used the dual needle and seat bowls so I would need all that FP to supply the carb. What bowls are u using BTW? Bottom line, if the car is consistent and there are no issues,,, you don't have an issue. | |||
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| DRR Sportsman |
The bowls are APD billet enforcer bowls. Suspect there is zero ET to be gained. Or consistency since the most variation is in the 60ft and it's pretty consistent. BtW Ed, when turned up, less retard, the car went 1.328, 1.329, and 1.321. Those were all varying degrees of retard being played with. On most runs I'm pulling a lot too keep the front down. Motor is 555, 13:1. car weighs 3350+me at 215lbs and runs 148mph-153mph depending on weather. | |||
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| DRR Elite |
I'm still quicker/faster and my car works, perfection in motion! | |||
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DRR Trophy |
G,day, If your on alcohol your pressure is fine, don't lower it/ If its patricks vacuum referenced reg its a dead head style and exactly as apd say you will have a variance from it opening and closing. It won't have anything to do with g force unless the suction side of the pump is all wrong and you'll only see that on launch. is it the vacuum deal where idle pressure is lower? You can get a smoother trace by using a diaphragm type bypass reg but plenty of people run what you run and have no issues. A belt pump and diaphragm bypass or electric pump and throttle bypass and diaphragm bypass reg are the go for alcohol. Cheers | |||
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| DRR Sportsman |
It is a vacuum deal from Patrick as you mention, but it's not hooked up to vacuum. ApD said not to when i switched to their carb. I don't know what is in the regulator diaphragm or not. It's not a belt driven pump but rather a magnafuel 500 | |||
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DRR Pro |
Fuel pressure gauges have known  too be a little erratic when car is up on the bumper. Oh my car is not as fast as yours | |||
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| DRR Sportsman |
Just came across this. Red second paragraph in red. It's picking up pressure from needle and seat opening. Mine varying, but maintaining thru run.  | |||
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| DRR S/Pro |
So those are their bowls that were designed to be fuel all the time... and those need more than normal fuel pressure, even on gas! Since the bowls are full, fuel airation is not an issue as it could be with high pressure and normal bowls. | |||
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| DRR Elite |
I don't care what bowls are on it, the fuel pressure is too high. | |||
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| DRR S/Pro |
Ed, the type of bowl matters. Talk to Shawn, he had those bowls. I know a few racers who have had them on gas combos and they needed higher pressure to work correctly. Way more than I would ever thing you would need... I don't know why either, could be the float design, fuel discharge location or whatever... | |||
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| DRR Sportsman |
That's just the optional anti foaming bowls not the standard billet bowls. Denis LeBlanc | |||
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| DRR S/Pro |
How do you get the individual cylinder timing to log? I don’t see that option in the grid.... or was it not a grid J.R. Baxter ""Fathom the hypocrisy of a Government that requires every citizen to prove they are insured ..but not everyone must prove they are a citizen." 2024 Miller Rolla Competition Engines ProCharger Hoosier Tires Abruzzi | |||
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DRR S/Pro |
Yes on Grid, individual data is possible with the V500 because of its extra inputs. . NHRA Pro Stock..........now on a no CARB diet. | |||
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| DRR Pro |
I run a belt drive pump with a bypass regulator at the carb and mine bobs up and down.  -------------------- Bob Payton S/P, T/D, S/C, TOP 309Z, 393, 3093, 8X93  www.apdracing.com www.diamondracecars.com www.callies.com | |||
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| DRR Trophy |
While my racepak carb pressure bobs up and down like the examples shown it lowers about .5 at the hit and comes back after the finish line and has more "frequency" to the cycling of needle and seat which makes me wonder about a fuel volume issue. I run the same 500 pump but run 25 psi to the regulator and 6.5 to carb. Mine is a dragster so 60fts 1.0x. Have you ever checked pressure at regulator inlet? If it is low could cause this issue maybe. Top38 is correct on the billet bowls we dynoed yesterday and had to run 9lbs on the dyno to get O2 numbers and hp to come back to non billet bowl carb numbers at 6lbs. | |||
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| DRR Elite |
again, the fuel pressure is too high! | |||
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Bracket Talk Bracket Talk Forum Tech Talk - by Abruzzi Racepak carb pressure...graphs
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