I recently dyno tuned my car on the N2O. Every pass, on every size shot had a short lean spike in the high 13s on the A/F. I am looking for recommendations on a Nitrous Solenoid Delay. Are any of you using one with any success? Models with links would be helpful.

 

Anyone???

 

What some guys do is run a FPSS after the fuel solenoid and they use it to control the nitrous Noid. However, the lean spike probrably isn't from the N20, I think it was NX that did a test that showed the nitrous and fuel usually make it to the nozzle at the same time. More than likely it's from your fuel system trying to recover to the intial hit. If you havn't alresy done so, it's a good idea to eliminate your stock FP regulator in the tank and put an aftermarket one at the rails. A fuel accumulator might also help.

FWIW: I really don't think it has been proven that the intitial lean spike hurts these motors. It happens to almost everyone. I regularly see lean spikes in excess of 16:1 on the intial hit.

 

If you have the line from the fuel solenoid to the nozzle longer than the line from the nitrous solenoid to the nozzle that could contribute to the lean spike.

Even if they are the same length if you lengthen the nitrous line or shorten the fuel line I think it would help reduce the lean spike.

Remember you have about 1,000 psi pushing the nitrous and about 55 psi pushing the fuel. Which do you think will get to the nozzle sooner through the same length line?
I won't argue with NX but it sure seems to me like the nitrous has to get there sooner with equal length lines. And if it does I think it has to create a lean spike.

I believe my reasoning is sound. However I have no idea how much a given length effects the time it takes the nitrous or fuel to travel through the lines. Maybe some of our experts here have done some controled testing on this.

I can't see how a lean spike could be good for the motor. Of course the longer and or the leaner the spike is the harder it is on the motor.

 

I have used line lenght on dry hits many times for a poor mans window switch, so yes, line lenght does affect travel time. Now, a short line lenght of say 12 inches changed to 8 inches will likely produce marginal results if detectable at all.
Robert

 

would going from a 24 inch fuel line to a 8 inch line be noticeable

 

On a wet hit this would probably help or eliminate a lean spike. Fuel travels much slower than n2o.
Robert

 

I wanted to have both sets of lines for the dyno tommorrow and try them both.
I couldn't make it to get te shorter lines so the after tests will have to wait

 

One of the two stage window switches Dynotune/Nitro Dave sells might do the "trick" (pun intended, little play on the manufacture ).

Hook up the fuel noid to stage one, set the RPM for 2900 (or whatever), then hook the second stage to the Nitrous noid, and have that kick on at 3000 (or whatever RPM interval is required to get rid of the lean spike).

 

a stand alone fuel cell whould take car of th e lean spik right?

 

Maybe, but $500/700 compared to maybe 10/20 bucks? A stand alone is great for an inadiquate fuel supply on bigger hits, however sometimes on smaller hits it is really not needed.
Robert

 

My initial thought was it would take about 1/3 the time to travel through the 8" line. But the more I think about it that may not be true. It would be true if there were no fuel in the line and it was starting at the solenoud and traveling through an empty line to the jet (nozzle). This would happen the first time you spray if the line is empty. However it would seem to me that the fuel line probably stays full or nearly full after the solenoid closes and the next time it opens the fuel is at the nozzle ready to flow so I expect there is no noticable difference in the time it takes for the fuel to get to the nozzle no matter how long the fuel line is.

However I think the nitrous line is different. We know we need to purge the nitrous line to get to the solenoid so over some period of time the nitrous disapates from the line. So I suppose depending on the length of time between sprays the nitrous line would be empty but I do not know how long it takes to disapate.

So my conclusion is that shortening the fuel line will not help the lean spike but lengthening the nitrous line could help a lean spike depending on how long it takes for the nitrous to disapate in the line.

I have 8" lines on both nitrous and fuel. My data logging shows no lean spikes. Every time as soon as the log shows wide open throttle the air fuel ratio immediatly starts to get richer. My thought is the fuel hits the nozzle immediatly when the solenoid opens and the nitrous never gets there first.

Robert or any other experts if fuel stays in the line like I think it does how do people get lean spikes? There must be something wrong with my analyses of how it works because if I am correct anyone with a longer nitrous line should be more prone to not have a lean spike. Yet mine is about as short as you can get and I see no lean spikes. Is it possible that the fuel is some how pulled through the nozzle after the solenoid closes? I do not see how this could happen. But if this is true then long fuel lines could cause lean spikes.

 

There are many scenereos for a lean spike. the most common is draining of the the rails. Depends on shot size also. A fuel pump is often enough to eliminate spike, and/or a hot wire kit. Next is a return and reg at the rails. Also a bap can cure this. Now the fuel line can be a problem for some when long, and can be self draining and/or pulled dry from starting car and subsequent vacuum/venturi effect? don't know for absolute but playing with line lenght has been a tuning aid for some time. Like you say, maybe the real answer is a longer n2o line. I have no lean spike either, but have pump, hot wire and return and reg, which also helps on the big end. So in conclusion, so many areas and every car is different, we need to find what works for our particuler needs. Good insight though Terry.
Robert

 

well i ordered a standalone and im hopin it will take care of the lean spike. im sure it will as the pressure for the fuel will be there. same thing as running a return line and reg but wiht out doing that. on motor car got plenty of fuel, but i do notice when the nitrous hits fuel drops alot on my gauge. and i have a 255 pump and hot wire kit. i think ill benfit fro mthe stand alone. plus ill have it for when i build a motor and go DP

 

I did not say so in my post but I when I asked how people get lean spikes I was assuming the fuel system could keep up with the demand. You certainly will get a lean spike if the fuel system can't keep up and the fuel pressure drops. My fuel system is stock and fuel pressure runs 58-60 psi. It will drop as much as 3-4 psi when the 50 shot hits. I will see what happens when I up it to a 100 shot.

I don't know for sure either but with the solenoid end of the fuel line closed I would not think that any venturi effect could pull more than a very small amount of fuel out of the nozzle end of the fuel line.

 

Well I think if the line is basically horizontal then you can get a venturi to act like it should. Meaning, take a straw and pull some liquid with finger over the end out of a glass of water verticaly, it will hold the liquid right? then take and lay the straw with finger still over the end horizontaly and you'll see the water go glug glug out of the straw. I am not a fluids dynamics expert so, take this with a grain of salt.
Robert

 

I'm no expert either. I could see this happening if the line were level or even going down hill to the nozzle and if the end of the fuel line were completly open. But if the line goes up hill to the nozzle and even if it does not, the hole in the jet is so small compared to the inside of the fuel line I have a hard time believing the fuel line gets drained.

Robert: In your spare time could you put a clear fuel line on your car so you can see if it stays full or not and let us know?

 

You know I do have a 3rd stage wet that is hooked up and in working order (pulling off the rails), but haven't had the ***** yet to spray my planned 300rwhp combined shot.
Robert

 

I'm getting a stand alone this winter