Dry system + returnless = ???

[Sonic Blue 2V]

I acquired an Edelbrock dry kit for my 03 GT and since I have 03 cobra tank and pumps installed, Edelbrock says I don't need the VBU (voltage booster unit) installed since the cobra pump can supply all the fuel I need. Isn't the ECU going to try and keep the fuel pressure constant at 40psi? When I inject nitrous on a dry kit, is it all on the ECU to keep up with the rich/lean condition with no addition of fuel pressure? The only dry kits I have used before was on a return style fuel system and fuel pressure was spiked up to supply the fuel. Just want to make sure I'm not building a modular grenade before I push the button!

[Loud412]

i think on the returnless cars u have to put the nozle before the maf. When the system gets activated , the maf sees the nitrous as an increas in the air entering the engine and adds fuel. U would probably want to get a custome tune with it though.

[Sonic Blue 2V]

I've read some other posts about putting the nozzle before the MAF but talked to Edelbrock and they insist that it needs to go right before the throttle body.
What kind of tune would you imagine that I need? If O2 isn't reading rich or lean, wouldn't I be fine without a tune? Not sure what else a tune might do besides adjust timing and with an 80 shot, stock timing should be good.
Still not positive how quickly the computer can adjust to the lean mixture that the O2 sensors will surely see when the dry system hits? Should I be concerned or just shut and spray it?!?

[Joe Lynch]

Your concern is justified!! The Edelbrock guy didn't tell you right. If, on the dry kit, enrichment is provided solely by increasing fuel pressure, then you DO need to install the VBU!!

If you don't do it, there will not be any enrichment, and you will run lean.

The fact that you have the darn good '03 pump just means that the pump will keep up pretty well and you won't run out of pump. It does NOT mean that you will automatically add fuel when the nitrous is activated.

I strongly suggest you call Edelbrock back and go over this again with them. The bottom line is this--you MUST have a fool proof way to force additional fuel proportional to the nitrous shot over what you have on motor alone.

You do not need to retard timing below 100 hp. You DO need cooler plugs, say NGK TR6 or Motorcraft AWSF-22C. Do not use nitrous with the platinum plugs that come in your engine.

Joe Lynch

[vrtical]

I run a dry kit. If you run the nozzle before the T/B like I do, you need a nitrous tune. I am against running any nitrous kit with the nozzle before the MAF.

Stock fuel setups can handle 100 hp nitrous pretty decent with colder plugs and a safe tune.

[Sonic Blue 2V]

Originally posted by Joe Lynch
Your concern is justified!! The Edelbrock guy didn't tell you right. If, on the dry kit, enrichment is provided solely by increasing fuel pressure, then you DO need to install the VBU!!

If you don't do it, there will not be any enrichment, and you will run lean.

The fact that you have the darn good '03 pump just means that the pump will keep up pretty well and you won't run out of pump. It does NOT mean that you will automatically add fuel when the nitrous is activated.

I strongly suggest you call Edelbrock back and go over this again with them. The bottom line is this--you MUST have a fool proof way to force additional fuel proportional to the nitrous shot over what you have on motor alone.

You do not need to retard timing below 100 hp. You DO need cooler plugs, say NGK TR6 or Motorcraft AWSF-22C. Do not use nitrous with the platinum plugs that come in your engine.

Joe Lynch

Well I'm glad you responded Joe, I already had your cell phone number written down to call and bug you! You seem to have gone down the nitrous tuning road and know a lot about it. What the Edelbrock told me was that the VBU would only amplify the voltage from the computer to the fuel pump (and not over ride the signal) and raise the pressure. I ask him " won't the computer still try to keep 40 psi at the fuel rail"? And he says " let me go ask". When he returns he tells me that his supervisor says I don't need to use the VBU since I have the cobra pumps. No it makes me wonder if the VBU really does just drive the pump in order to raise the fuel rail pressure??? Seems like that would throw a code since the fuel rail sensor would see too high a value?
If I did try to use the VBU, I'm not sure it would be capable of driving the dual pumps since it was made for a single pump? Dang it! I just want to go fast!:eek: :hammer:
What would your suggestion be Joe? If it makes a difference, I just received my SCT tuner and haven't learned enough about it to know how it can help me with this combo.

[Joe Lynch]

I think Edelbrock needs to explain exactly how the VBU works on a returnless system. I think they don't understand the returnless system and that they need to be challenged to tell you exactly how their system is supposed to enrichen the mixture.

The only way to do it is to lie to the computer about what the fuel pressure in the rail really is. If the "VBU" tells the computer the fuel pressure is 30 psi instead of 39, it will speed the pump up until the signal received back from the fuel rail is 39. The REAL pressure may be 50 psi, and you will enrichen the mixture about 13%. They would have to lie to the computer a bunch to get the pressure up enough for 70-100 shot.

You are correct that speeding the pump up will only work until the computer slows it back down again.

Now you are beginning to understand why I like wet systems on a returnless car.

Tell Edelbrock they need to convince you that they really know hot to richen up a 99 up returnless system. They might well know how to do it, but the guy you have been talking to hasn't convinced anyone yet. Your hardware may turn out to be fine, but it is too critical to install it without understanding exactly how their stuff works. You have got to talk to someone who knows exactly what they are doing. I'll be happy to review whatever they can tell you.

I really hope Edelbrock has their act together on this, and I hope the problem is really just the green guy on the phone.

Joe

[Sonic Blue 2V]

Thanks for your thoughts Joe. I will call again tomorrow and quiz them on it until I feel like I have a handle on it.

Saw one of your writeups on the eFPC. Is that what is used to adjust the value of the fuel pressure rail sensor so the computer will continue to raise the pressure to where you want it?

[DARKHRSE99]

Yes that is what he used. I plan on buying one for my setup also..

[Joe Lynch]

I started out with the MAFterburner Plus first and tuned the engine with it. When I changed the fuel pump and installed the regulator and Mark developed the eFPC for the supercharged cars, I decided it would work great on a nitrous car as well, especially in tricking the computer to work with a return style fuel system.

The good thing about both devices is that you can switch settings with the nitrous arming switch, and then the programs switch automatically when you go to wide open throttle. So you have four calibrations--two wide open throttle (open loop) settings and two part throttle (closed loop) settings. This is perfect for a nitrous car.

But I need an SCT tuner setup to do all the things I can't do with the MAFterburner Plus and eFPC. Advance, idle, rev limiter, knock sensors, all that stuff.

"cubic money, not cubic inches"

Joe

[Sonic Blue 2V]

Got in touch with a more experienced tech at Edelbrock today and he tells me that the VBU (voltage booster unit) "overrides" the signal coming from the ECM to the fuel pump when the nitrous system is activated. He helped me with the schematic of activation and he is indeed correct, the fuel pump is driven directly by the VBU when the nitrous switch is activated. It will raise the fuel pressure above the factory 39 psi and allow more fuel when the nitrous is injected. Now my dilemma, I have already installed the 03 cobra pumps and the VBU is made to work with around 10 Amp max draw (has a 15 Amp fuse). It is made by MSD and MSD tech tells me that a dual pump setup may draw too much current to work with it??? I guess I will need to put a amp meter inline to the fuel pump (from the VBU) to determine the max amp draw and see if it stays below 15A or blows the fuse.

Next question...if the VBU can handle the dual pump current draw, isn't the cobra pumps going to force more fuel at this overidden voltage than the stock pump would? And in turn be way too rich as compared to the stock pump volume at the overridden voltage? Edelbrock tells me that the VBU is adjustable but is at the lowest setting to work with an 80 shot. I guess if it was too rich with a .042" nitrous jet, I could just pill it up until the air/fuel ratio came out right on a dyno with wideband O2? And here I thought this was going to be a plug and play!

[DARKHRSE99]

I wonder if the VBI would work on a wet kit? It sounds like a great
Idea

[Sonic Blue 2V]

Originally posted by DARKHRSE99
I wonder if the VBI would work on a wet kit? It sounds like a great
Idea

Should work with it fine. It is a MSD Fuel Pump Voltage Booster P/N 2350 but according to the MSD tech, it should only be used with a fuel pressure regulator and return style system. The reason Edelbrock is getting away with it on a returnless system is the dual relay circuitry they use to only use the VBU when you hit the nitrous switch (and not as a full time circuit.) Let me know if you want the schematic that came with the Edelbrock kit so you can wire it up as a "nitrous only" booster.

[DARKHRSE99]

Could you post it for me? I really appriciate it

[Sonic Blue 2V]

Originally posted by DARKHRSE99
Could you post it for me? I really appriciate it


I made several notes on the drawing so I'll need to clean it up and get it scanned when I get a chance.

[DARKHRSE99]

Thanks

[Joe Lynch]

Sonic Blue 2V -- That's a little better. But you have essentially lost control of the fuel pressure without a regulator. But it will work if you add the regulator, then adjust it until the air fuel ratio is right.

I don't know about the amp rating. Maybe for 12 seconds it will be fine.

OK, I did my part. Good luck with it.

Joe

[Sonic Blue 2V]

Originally posted by Joe Lynch
Sonic Blue 2V -- That's a little better. But you have essentially lost control of the fuel pressure without a regulator. But it will work if you add the regulator, then adjust it until the air fuel ratio is right.

I don't know about the amp rating. Maybe for 12 seconds it will be fine.

OK, I did my part. Good luck with it.

Joe

Do you mean add a non returm style regulator like a holley blue uses? Since I don't have a return fuel line, that's the only way I can think that it would work. Then adjust the VBU to raise the fuel pressure to say 56 psi under full load, then regulate it down to 50 psi right before the fuel rail? Might just work!
Thanks for all your help Joe. You ever come to Dallas area to race? I know it's a little drive from Midland but we have 6 drag tracks within an hour of me:D

[DARKHRSE99]

You have to buy a Aeromotive Adj regulator and run a return line back to your pump.I think the part# is 10006

[Joe Lynch]

A return style regulator like a Aeromotive A1000-6.

I'm going to tell you the truth, as I see it. You will need a chip tune to go with the pump controller. That is all there is to it. No way would I run that system without running it on the dyno.

But that is true with any nitrous system.

Joe