too much N2O?

[redrumracing01]

ok so hears the deal my freind (pro5.0mcbarron)has a lx hatch with the bottom end consiting of a stock 94 cobra short block,we put nitrous on the car a month ago and it was only running a 100hp shot pulled the plugs after fartin around on the street pulled the plugs and they looked brand new,now after a few drinks on sat we threw in the 150hp jets(dont worry we didnt take it out untill today)and we were on i-90 in 3rd and sprayed it all the way threw 4th and no problems so iguess my question is are cutting it close with those pistons,possibly thinking of going 2 steps bigger just on time to see how much harder it will pull because it pulls like a bat out of hell.i think he will be fine in the fuel dept he has a 195lph in tank pumpany one have bad luck with the 94-95 stock short blocks?any who the cars best et is 11.49 @121mph and the car regularlly sees the street

 

[YardSpecial]

Just watch your timing and keep it fuel fat.

Detonation is the killer here............

Thats why a magnifying glass helps big time, look for pieces of pistons on the plugs..........

 

[281pony]

i wouldnt go over 150 personally. if he wants to spray it till it dies though and its taking it now, may as well go up.

94 cobra's had hyper pistons right? my uncle has a 94 cobra who i rarely talk to, i think he mentioned going to forged when he rebuilt it. those hyper pistons definately wont like nitrous detonation though.

just my opinion, i have no experience with nitrous.

 

[Boostn]

I am curious to know what timing does he have it set at for 150 shots? I am going to run only 100 shots of nitrous for this weekend at PIR while bumping up the base timing from 13 degrees to 16 after checking the spark plugs.

Its really hard to tell if it is detonating or not. Its the price to play

If my car ran good, I would considering going up to 125 shots. Just taking it one step at a time. I only had 2 runs last time I went and without practice I had 12.6 at 107.5 mph. That run was only at 75 shots.

 

[WaterPog]

The hyper pistons won't breakup from too much HP like a cast piston will, but when/if they do let go they tend to let go big from what I've seen. There is a guy on TM.com who was over 600whp with a stock '93 shortblock (same as yours) for quite some time and it was still the block that let go first. If the tune is where it belongs it'll last just as long as a forged piston shortblock.

 

[redrumracing01]

bumping up the base timing from 13 degrees to 16 after checking the spark plugs.

huh that sounds like the wrong derection to go on the timing?my freinds running 10 degres of base,i tink you would wanna atleast drop it 10 deg,water pog or any one else please chime in on this so this can be clarified cause so far my freinds car has had no problems with 150hp N2O

 

[codemonkey]

nitrous is like a hot girl....

 

[Black 93 Fox]

nitrous is like a hot girl....

LOL taking my signature saying are ya

 

[WaterPog]

16* on a 150shot does sound awefully high to me now that you mention it, aren't you supposed to remove 1.5-2* for every 50hp?

I'm no tuning wizard, but I'd expect you to be more in the 8-12* base timing range on a 150 depending on what your motor likes and how agressive you want to be with it.

 

[Boostn]

huh that sounds like the wrong derection to go on the timing?my freinds running 10 degres of base,i tink you would wanna atleast drop it 10 deg,water pog or any one else please chime in on this so this can be clarified cause so far my freinds car has had no problems with 150hp N2O

I do take off 1.5 to 2 degrees of base timing for each 50 shots of nitrous. I assumed 16 degrees was the base timing so when I ran 75 shots, I was between 13 and 14 degrees of timing. The car ran great and had no problems. I even looked at spark plugs, no lean conditions. I know its not very efficient way of checking so that is why I am going to see if horsepowerfreaks.com have the wideband o2 sensor system, Innovative LM-1 with rpm kit, so I can install it on my car and see how it actually performs.

I really hate this idea, but I did consider to try (this came from the owners manual for Holley Systemax Big Shot Kit):

"4.2.1 Determining Optimum Ignition Timing
The following scheme for determining ignition timing should allow you to determine the optimum setting for your vehicle, without
incurring engine damage during the tuning phase.
1. Estimate the reduced ignition timing that you think will produce the best power, based upon the 1.5 to 2 degree retard per
50 horsepower increase rule.
2. Set the ignition timing 2 to 3 degrees retarded from your best power estimate setting.
NOTE: Nitrous bottle pressure should always be set to the same level at the start of each run. NOS systems are calibrated to
run at nitrous pressure levels of 900 to 950 psi.
3. Perform a dynamometer pull or a full throttle pass down the racetrack. Note the power reading or vehicle mph.
4. Increase the ignition timing 2 degrees.
5. Perform a dynamometer pull or a full throttle pass down the racetrack. Note the power reading or vehicle mph. Examine
the spark plugs for signs of detonation.
5A. If power increases or vehicle mph increases and spark plugs show no sign of detonation, increase the ignition timing 2
more degrees.
5B. If power increases or vehicle mph increases and spark plugs begin to show slight signs of detonation (very light
peppering or speckling on the porcelain)—STOP. Do not advance the timing further. You may choose to reduce the timing
2 degrees at this point for an extra margin of safety.
5C. If power decreases or vehicle mph decreases, reduce the ignition timing 2 degrees.
6. Repeat step 5 until optimum ignition timing is obtained."

Oh well I could use the wideband to help me see if I am getting too lean, like more than 13.0 or more.

 

[D347643]

detonation has to do with more than just timing, whats your comp ratio at. Im running 9:1 flat, let than stock and im gonna run 14 with 150 shot. im also running a fp safety switch too though...good investment.

 

[Boostn]

I am at 9:1 compression also. What FP safety switch?

I did run 175 shots before but I retarded so much down to 10 degrees base timing and so much fuel pressure. But that was nice extra power

I expect I could do better when I get the wideband with some tuning.

 

[D347643]

they have a fp shutoff switch that you wire inline with your n20 setup. when your fp drops to low itll cut off the power to your solenoids so you dont detonate. summit sells them, not to spendy either

Drew

 

[Boostn]

Thats interesting safety feature. That would only help me if something gets plugged up before the sensor. I have external aeromotive fuel pump that'll supply fuel pressure more than I need.

Also would help if my gas tank gets too low too!

I'll put that down as an item I should have.