solenoid test, weird????
08-05-2007, 10:01 PM
#1
solenoid test, weird????
my car did a wierd thing. i set the system up for a 35 shot (dynotune kit-msd window-zex tps). this is a no nitrous, fuel soleniod test. i figured the engine would bog and lose power. well no the exact opposite happened. the rpms hit 300 and the car pulled harder then it normally does. was that supposed to happen or is there something wrong with this situation?
Last edited by Spanky's Monkey; 08-05-2007 at 10:08 PM. Reason: spelling
08-05-2007, 10:19 PM
#2
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that is a little strange, but i wouldn't say its anything to be worried about.
if you look at a dyno graph (there is a good one on the crate engine depot website for the 2.4 intake manifold mod. take a look) right around 3,000 rpm the fuel mixture goes lean. i have always felt something happen there but never knew exactly what it was from, i figured it was the way the cam was setup. But the mixture gets lean, very lean. I think its around 11:1, If i remember right ideal is 14.7:1.
So basically what you did was just richen up the mixture some, and got it closer to that magic number.
I never really thought about that before until just now, but it would probably be to your benefit to go to a dyno shop and tune the fuel jets on a dyno and get an air fuel reading. the last thing you want is that lean mixture with nitrous. and even that factory level lean might be enough to cause some problems.
if you just want to play with it now i would bump the fuel jets up a size or two just to be safe. play around a little, you are only doing a 35 shot so you shouldn't have to worry about too much.
Did you go with a colder spark plug?
if you look at a dyno graph (there is a good one on the crate engine depot website for the 2.4 intake manifold mod. take a look) right around 3,000 rpm the fuel mixture goes lean. i have always felt something happen there but never knew exactly what it was from, i figured it was the way the cam was setup. But the mixture gets lean, very lean. I think its around 11:1, If i remember right ideal is 14.7:1.
So basically what you did was just richen up the mixture some, and got it closer to that magic number.
I never really thought about that before until just now, but it would probably be to your benefit to go to a dyno shop and tune the fuel jets on a dyno and get an air fuel reading. the last thing you want is that lean mixture with nitrous. and even that factory level lean might be enough to cause some problems.
if you just want to play with it now i would bump the fuel jets up a size or two just to be safe. play around a little, you are only doing a 35 shot so you shouldn't have to worry about too much.
Did you go with a colder spark plug?
08-06-2007, 12:13 AM
#3
that is a little strange, but i wouldn't say its anything to be worried about.
if you look at a dyno graph (there is a good one on the crate engine depot website for the 2.4 intake manifold mod. take a look) right around 3,000 rpm the fuel mixture goes lean. i have always felt something happen there but never knew exactly what it was from, i figured it was the way the cam was setup. But the mixture gets lean, very lean. I think its around 11:1, If i remember right ideal is 14.7:1.
So basically what you did was just richen up the mixture some, and got it closer to that magic number.
I never really thought about that before until just now, but it would probably be to your benefit to go to a dyno shop and tune the fuel jets on a dyno and get an air fuel reading. the last thing you want is that lean mixture with nitrous. and even that factory level lean might be enough to cause some problems.
if you just want to play with it now i would bump the fuel jets up a size or two just to be safe. play around a little, you are only doing a 35 shot so you shouldn't have to worry about too much.
Did you go with a colder spark plug?
if you look at a dyno graph (there is a good one on the crate engine depot website for the 2.4 intake manifold mod. take a look) right around 3,000 rpm the fuel mixture goes lean. i have always felt something happen there but never knew exactly what it was from, i figured it was the way the cam was setup. But the mixture gets lean, very lean. I think its around 11:1, If i remember right ideal is 14.7:1.
So basically what you did was just richen up the mixture some, and got it closer to that magic number.
I never really thought about that before until just now, but it would probably be to your benefit to go to a dyno shop and tune the fuel jets on a dyno and get an air fuel reading. the last thing you want is that lean mixture with nitrous. and even that factory level lean might be enough to cause some problems.
if you just want to play with it now i would bump the fuel jets up a size or two just to be safe. play around a little, you are only doing a 35 shot so you shouldn't have to worry about too much.
Did you go with a colder spark plug?
cars run rich under WOT for several reasons...theres less time for the fuel to atomize and mix with the air so you compensate by adding more fuel so more will be able to atomize and burn correctly. also, fuel serves as a means to cool the combustion temperature. adding extra fuel during WOT will keep the cylinder cooler, preventing knocking
our cars run much better and typically get more power running unusually rich (normal WOT AFRs are closer to 12:1) at values between 11:1 and 11.5:1, so the cars are runing fine...a better question to ask is why theres such a sudden drop in AFR from 14:1 to 11:1 at 3kRPMs, opposed to a system closer to 14:1 at 2krpms 13:1 at 2.5krpms, 12:1 at 3krpms, and so on until a desired AFR is achieved....its a dramatic change at a set RPM point opposed to a gradual richening....thats the only thing i might change in a stock tune
08-07-2007, 08:28 PM
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you are absolutely right. I looked at the graph, saw that the line went down and without giving it too much thought i just assumed gm did something funky like they are known to do every now and then. +1 for catching my mistake
so forget what i said about going richer on the fuel jet, just run what they say, but do spend some time on a dyno to get it set where it needs to be. its a small price to pay.
Normally you want to go with colder plugs with nitrous, how much colder depends on a lot of things. for you i would guess one maybe 2 steps colder would be good. you might even be ok with stock plugs. just keep an eye on them. if the car ever seems like it doesn't run as well pull the plugs and take a look at them. every motor on nitrous i have ever seen has a tendency to eat plugs. The hotter they are the shorter their life is. there are performance reasons for going with a colder plug too.
so forget what i said about going richer on the fuel jet, just run what they say, but do spend some time on a dyno to get it set where it needs to be. its a small price to pay.
Normally you want to go with colder plugs with nitrous, how much colder depends on a lot of things. for you i would guess one maybe 2 steps colder would be good. you might even be ok with stock plugs. just keep an eye on them. if the car ever seems like it doesn't run as well pull the plugs and take a look at them. every motor on nitrous i have ever seen has a tendency to eat plugs. The hotter they are the shorter their life is. there are performance reasons for going with a colder plug too.
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