nitrous questions

[trudsm]

I have just used nitrous for the first time and have some questions. First I'm running a 50 shot using the 37 nitrous jet and 22 fuel jet. And also running 20psi of boost. Normally with 20 psi I see 60 psi of fuel pressure but when the nitrous comes on I see 40psi of fuel pressure and this is with a 255hp fuel pump. Since I'm losing fuel pressure I've had to go a 28 fuel jet to get a 11:1 a/f ratio. And I want to run 25psi of boost and I think that it's going to take a fuel jet in 30's does this seem normal? The logs look great it will hold that 11:1 a/f ratio all the way through. It just seems odd I haven't read anybody saying they lose fuel pressure and have to use such a big fuel jet. And for my next question I see 600psi nitrous pressure and read I should be in the 900 to 1000 psi area. That makes me assume that when I heat that bottle and get that psi I will run even leaner. What is the importance of bottle pressure? Is it just to keep a good tune? Or is there other critical factors besides running out? Thanks for any help you may have for me. Matt T

[fusionsport]

where are you pulling the fuel from?

[Hal]

Assuming your n2o is properly installed, dropping fuel pressure is BAD.

You should stop using the kit until you determine why.

The drop in pressure effects not only your n2o/fuel mix but also the volume of fuel flowing thru your injectors.

If the pressure is dropping, you have reached the maximum fuel flow point for some reason.

The danger in this is the fuel pressure in the rail which supplies the injectors.

The fuel flows left to right, and if the pressure is falling, each subsequent injector sees less fuel volume.

Your overall AFR may be ok because it's an average of all 4, but you risk burning the valves in cyl #1 (rightmost cylinder).

Hal

[Steezy303]

damned you Joe

[fusionsport]

Hal is exactly correct. When you install a nitrous system you need to be very careful where you draw the fuel from. Double check your fuel feed, then check it again.You also need to make absolutely sure you have a good filter and pump. A 20psi drop is very unusual for such a small shot, especially on a 255. If I were you I would double check everything from the pump forward, replace the filter and possibly replace the pump if it is much more than a year old. At 100 bucks to replace it is a fools economy to not replace it if it is even slightly suspect.

If you want to swing it by the shop I will be glad to take a look at it.

[AWD4G63T]

Hal is exactly correct. When you install a nitrous system you need to be very careful where you draw the fuel from. Double check your fuel feed, then check it again.You also need to make absolutely sure you have a good filter and pump. A 20psi drop is very unusual for such a small shot, especially on a 255. If I were you I would double check everything from the pump forward, replace the filter and possibly replace the pump if it is much more than a year old. At 100 bucks to replace it is a fools economy to not replace it if it is even slightly suspect.

If you want to swing it by the shop I will be glad to take a look at it.
I don't really know much about nitrous but could there be anything in the kit that is droping voltage to the pump? Is it rewired? Could the lack of a rewire effect fuel pressure like that?

Jesse

[fusionsport]

not likely- the only way I can think of you could screw that up is to draw the power for the solenoids from the fuel pump circuit and drop voltage to it, but that is almost inconcievable. A rewire might help, but honestly a stock pump should be able to handle a 50 shot, marginal but it would handle it. A 255 shouldnt even care. Look at it this way. a 400whp mustang running a 100shot still has plenty of fuel left with a single 255 and no rewire.

The 20 psi drop is weird- I would almost lean toward a bad regulator or pump, but everything should be checked.

[Bryan Savage]

The fuel flows left to right, and if the pressure is falling, each subsequent injector sees less fuel volume.
Not in mine!

[Hal]

A dual feed rail will still suffer some degree of tapered fuel loss if the fuel volume is not sufficient enough to keep up with the demand.

Regardless of the direction of flow or the number of feed points (1 vs 2), if the volume of fuel entering the rail is not enough to meet the needs of the injector bank (as indicated by dropping fuel pressure), there will be some degree of tapering in the flow.

Hal

[CU DSM]

Sorry to stray off topic, but dang Bryan, that's some nice duct tape you've got on your firewall there! ;)

-Jonathan

[Bryan Savage]

Sorry to stray off topic, but dang Bryan, that's some nice duct tape you've got on your firewall there! ;)
Think it will pass for 0.032" steel at track inspection?
:p

[trudsm]

I have found my problem! I'm a idiot........well when I hooked up dsmlink to control the nitrous I tapped into the fuel pressure regulator wire instead of cutting it. So when the nitrous got grounded so did the fuel pressure regulator making it drop to 40 psi. I put the 22 fuel jet back in and it is running pig rich now just need to lean it out a little. Thank to all the replyed it got me thinking on the right track.

[fusionsport]

what fuel pressure regulator wire? do you mean the little solenoid on the firewall that cuts vac signal to the FPR?

[trudsm]

Yes that is the one. Dsmlink takes control over the fpr solenoid to control the nitrous. I tapped into it at the ecu but to fix my problen I just disconected at the firewall.