fun with EFI

[bobtodd]

Alright, I just got back from trying out the 50hp shot of the juice for the first time since putting new head gaskets in and getting my heads done. Just the 50 shot alone put a smile on my face. After 4,000 rpm's that thing just wants to keep pulling. I love it.
Here's the dilemma though. I have an Extender. Extenders dont come on(so I have heard) until 4000 rpms....and I can definately tell when driving my car. My window switch is set for 3200 rpms. I put down the accelerator to engage my WOT switch when the 3200 rpm mark comes I really dont feel anything until the 4,000 rpm mark when the Extender must come on. Then that sucker smoothes out and really goes.
What can I do as far as tuning for anyhting below 4,000 rpms? Do I need to find an alternative way to tune my car? I dont want the thing running rich or lean at WOT before the Extender comes on. I know I should get the car on a dyno and see what all is happening. Any ideas? I thought about throwing a 4000 rpm pill in the window switch, but then I am losing those additional rpms. Then again I would only be going below 4000 rpm in first gear(or second) if I am shifting right.

[Mark302]

what setting are you running on the extender? Also your motor is probibly just really coming on at 4000 and that is what you are probibly feeling. On the dyno the a/f doesn't make sudden change when the extender comes on for me.

[bobtodd]

I've got the Extender set at 12.5:1. If I up the juice should I set the A/F lower? On just the motor I can feel the power band kick in around 3,200 rpms and go on up to just under 5,000 rpms. You would think thats when I would really feel the nitrous kick in wouldnt it? Now it feels like the powerband with nitrous is 4,000rpms and keeps on going up. The guy I bought the car from said the cam was a nitrous grind cam. Is this how a nitrous cam works? Cause usually from around 4,500rpms on up the car(N/A) feels flat and now I can feel the car(juiced) actually pull on the top end....it feels awesome!

[Greg@GLD]

The Extender should not have a huge effect on the nitrous. It sounds like you have your timing retarded too much. You should be getting a thrill from the moment you hit that juice. What bottle pressure are you spraying at? Are you using a purge valve? You might be feeling the effects of air in the line. It might be taking until 4000 RPM for the juice to actually make it to the nozzle.

These "critical stats" are what we need to know:

1. What bottle pressure did you spray at?
2. Purge or no purge?
3. Base timing?

With a 50 shot you really do not need to retard timing much, if at all. My guess is that you do not have your timing advanced or it's even retarded a little bit. Also, a "nitrous cam" is really meant for copious amounts of the squeeze... If you have retarded timing coupled with a nitrous cam and a 50 shot, it probably isn't feeling real strong.

[Mark302]

It may just be alot richer in the lower rpms on the n20 and changes how the power comes on???

[Greg@GLD]

I really think the whole issue revolves around timing as well as the manner that the nitrous is being used.

I ran a "nitrous friendly" cam in my Cobra about 6 years ago and it actually ran pretty good off the bottle (and I actually also ran it with an Extender!)
I had aluminum heads and had my timing advanced as high as 18 degrees when off the bottle and the car trapped 110MPH in the 1/4. 116 with a 80 shot spraying in 2nd and 3rd only.

Greg predicts timing is the culprit...

[bobtodd]

Bottle pressure was just a bit over 900 psi. I used the purge. Base timing is 16*. I'll get some more runs in tomorrow and see how it runs. I really dont think this is some wild nitrous cam in my car. The car felt great with the nitrous in the higher rpm's....I really liked it. It's just the lower rpms below 4,000rpms that I didnt feel anything. Maybe I didnt purge enough. Once I make a run and let off the throttle is it necesary to purge again before I do another run?

[bobtodd]

I'm not saying the car runs crappy off the bottle either. I think the cam in the car is a good set up. This car really does run good...260hp N/A at the wheels. Nothing wild but it is a good runner. I can mess with the timing and see what that does for me.

[bobtodd]

So if my timing is retarded then my lower rpms will suffer?

[Greg@GLD]

900 is a little low- allowing for inaccurate guage reading, you could still have been spraying from a gas to a gas or getting a surge.
Remember- 875 PSI is the point where nitrous changes from a gas to a liquid, so let's say your guage is off by a little bit- if it read 900 you could have easily been in that area where the juice was in a gaseous state from the time you sprayed to whan it came out the nozzle. By going up into the 900's or 1000 PSI this is going to be eliminated and what you will do is be spraying liquid N20 which will change to a gas when it is released out the nozzle. This action will draw a tremendous amout of heat from the surrounding ambient conditions and create a "supercooling" effect that extends all the way to the intake valves. Result? Hang on for dear life! :D

16 degrees base is plenty, I assume you do not run any sort of retard device when spraying Bob?

Agree with Dan, spray at 1000 PSI. You don't HAVE to purge if you make more than one pass in a short time. Try raising the bottle pressure without messing with timing first.

[Greg@GLD]

So if my timing is retarded then my lower rpms will suffer?


For SURE!!! An old racers trick on high HP cars is to retard timing down low to help keep the tires from blowing off at launch. When you run a hotter cam, timing off idle means a lot. I find it makes quite a big difference Bob.
I run my 347 at 20 degrees base off the bottle.

[bobtodd]

No retard device Greg. All this nitrous stuff is still new to me. When I get up into the bigger shots should I be using one?
I will try raising the bottle pressure and see what this does for me.

[bobtodd]

I have a brand new autometer gauge mounted in my dash.

[bobtodd]

I'll mess with both timing and bottle pressure tomorrow. Maybe I could get the car over to WIR friday and have you guys help me out.

[Greg@GLD]

No retard device Greg. All this nitrous stuff is still new to me. When I get up into the bigger shots should I be using one?
I will try raising the bottle pressure and see what this does for me.

I run a nitrous computer in my Cobra Bob. It allows me to run full advance when off the bottle, and dial the amount of timing I want to pull when on the spray. It has window switches on the dash that are dial-adjustable (versus pills) and it also has the ability to "dial the hit". Kind of overkill for the small shot I run now, but I have all the things I need to run a bigger shot (enhanced fuel system, lower-comp heads)

Come to WIR friday, we can see up close what you're doing. The timeslip can help you- Do some dry runs charting timing settings and I bet you see your 330' times decrease as you increase timing.

[BlackLX]

I agree with Greg Bob-
A nitrous computer will allow you to run full timing off the spray which is a nice thing, then retard the timing when it is needed.

There is nothing wrong with NOT USING one of those though. A 50 shot is pretty conservitive. Keep the base timing at 16* and make sure you run higher octain fuel.

Once you start getting into the 100 shot, this is when you want to retard the timing. Start low like 10* with the 100 shot and make sure there is no detonation when spraying. If you pull the plugs and they look OK then slowly put timing back into it. A degree at a time to avoid detonation.

It all depends if you want to spray it on the steet or just at the track. If you are just spraying at the track, just leave the timing at 16* and retard it when you get to the track. This is what I did and it worked well. A n20 computer like Greg said would be nice and convienant-but its just more money.

ps--Time for me to go back on the bottle :) Good luck Bob!

[bobtodd]

My nitrous isnt doing anything at all. My car was just running better. My car is an open can of worms right now. I dont know what to think. There is no difference between the nitrous on or off.

[Greg@GLD]

My nitrous isnt doing anything at all. My car was just running better. My car is an open can of worms right now. I dont know what to think. There is no difference between the nitrous on or off.

Then you simply need to test the system and make sure it's actually working.
As in "test fire" it Bob. Perhaps you have made a mistake in wiring the system? Even with a 50 shot, you should be feeling it and feeling it good. So the thing to do is to make sure the system is working. You can use a voltmeter to make sure things are working electrically. You can use a ohm meter for continuity tests as well. Things like making sure the WOT switch is working. Perhaps your window switch is not wired correctly.

If you feel like taking a roadtrip, come on down to the house and we'll go thru everything and make sure it is working/arming...

[bobtodd]

Yeah...so many things to test out. I know the WOT switch works. The window switch is brand new but I havent actually gotten under the hood and checked it the way I should I guess. Maybe I will make it over to WIR on friday. My gf said she'd be up for going.

[bobtodd]

I think I may try taking the fuel pressure safety switch out of the equation also. It's brand new too though.