I have a question for anyone who has raced using nitrous. Is there a significant change in engine sound when the nitrous is turned on? I am using about a 90hp shot on a plate system. My air fuel ratio with nitrous is about 11.8:1. The car pulls stronger when the nitrous is on, but it sounds funny. It sounds "rougher" almost like the ignition is breaking up. I have checked everything I can think of in the ignition system and nothing appears to be wrong. As soon as the nitrous is turned off it returns to the normal sound. I am cutting 6 degrees of timing using an msd6al-2 programmable box. I am starting to think there is nothing wrong, but I want to be sure before I try it for a full pass. Thanks.

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Ryan Covalt
62 Plymouth Valiant Race Car 2170# 11.008 @ 117.65 MPH 1/4 Mile Best
72' Dart Swinger Street Car, 4 spd, 3330# 14.061 @96.58 1/4 mile Best

Sounds like detonation to me as detonation under nitrous sounds more like rumbling than knocking/pinging. Are you sure the timing retard is activating? What fuel are you running?

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Joshua

What about the spark plugs

gap
heat range
extended tip or not

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Spark plugs are NGK UR6IX (iridium plugs)
I cant remember for sure but I think the gap is set at 40
I think the msd said to use a gap of 45-50, but with nitrous it was supposed to be closer? Correct me if I'm wrong on this.
Fuel is currently 93 pump gas, when I race I run turbo blue (106 octane?)

One other thing. When then nitrous initially comes on it sounds good and pulls stronger (lasts about 1/2 second) then immediately the sound changes and power drops slightly, still pulls strong but not quite as strong as the initial burst.

Last I checked the laptop reading was showing the timing retard working. I will double check this. Will detonation cause a loss of power or simply break parts? When the rumbling sound starts is when the power drops slightly.

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Ryan Covalt
62 Plymouth Valiant Race Car 2170# 11.008 @ 117.65 MPH 1/4 Mile Best
72' Dart Swinger Street Car, 4 spd, 3330# 14.061 @96.58 1/4 mile Best

Are those plugs a "long reach" type plug? You don't want those with nitrous. You want a plug with a short ground electrode. If the the ground electrode is too long, it will not dissapate the heat, and will act like a glow plug (very bad). This has no relationship to the plug heat range.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

The ur6ix is the same reach as the ur4 that it had originally. The electrode appears to be the same design on the UR6IX and the UR4. So I am thinking it is NOT and extended reach? I was told the Iridium plugs were better in high stress and high heat applications so I tried them, I can switch back to a standard ur6 if you think I should. I guess I should try some racing fuel to see if it clears up? compression ratio is 10.8:1 so maybe it is detonating?

Thanks.

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Ryan Covalt
62 Plymouth Valiant Race Car 2170# 11.008 @ 117.65 MPH 1/4 Mile Best
72' Dart Swinger Street Car, 4 spd, 3330# 14.061 @96.58 1/4 mile Best

What is your total timing with 6 degrees pulled out?
How do the plugs look after you test? (do you have a strong light and magnifier?)

Simple test... pull more timing out and try again.
DD

Total timing is 30 degrees, so it is at 24 degrees with the timing retard. I will pull more timing and try it. I have a strong light but I don't have a magnifying glass. I will get one. The car is a daily driver so will I need to change the plugs to read them properly? or can I get a good idea from checking the current plugs?

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Ryan Covalt
62 Plymouth Valiant Race Car 2170# 11.008 @ 117.65 MPH 1/4 Mile Best
72' Dart Swinger Street Car, 4 spd, 3330# 14.061 @96.58 1/4 mile Best

Nitrous is like boost with plug gaps.....

You need less gap. I'd start with the stock .035. Go to .025 if you have too.

Also 1 step colder in heat range may help.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

You can get an idea off the current plugs.
If the engine went into significant detonation, you start to see small specks of silver colored (aluminum) melted onto the plug tips. The plug tips start to look pretty "torched" at that point.

With clean plugs and the right N2O tune, you will find black specks on the white tip insulator. (a light "peppered" look)
DD

Get rid of the NGK plugs and put a set of Autolites in it.

I never had any luck spraying with NGK's.

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Official Cookie and Mater Tormentor.

I checked the plugs last night and did not notice anything strange. They are black like it is running slightly rich, but I didn't notice any specks on the ground strap or electrode.

I cut timing back to 20 degrees total when the nitrous was on and it still sounds the same. It sounds like it is running rough or missing, and as soon as I turn the nitrous off it goes back to normal. I do not have autolite plugs but I will get some and try them.

I am going to drive to the Elk Creek race tomorrow, so maybe one of the guys there will be able to listen to the car and hear what it is doing. Any other ideas would be great. Thanks.

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Ryan Covalt
62 Plymouth Valiant Race Car 2170# 11.008 @ 117.65 MPH 1/4 Mile Best
72' Dart Swinger Street Car, 4 spd, 3330# 14.061 @96.58 1/4 mile Best

May-be a little too much fuel if it starts strong, weakens and the plugs are getting real black. (the N2O "hits" faster then the fuel)

What is your N2O jet size vs fuel jet size? How much fuel pressure?
I am getting the best results with my fuel jet just one size bigger then the N2O and 5 psi of fuel pressure.
DD

Also I think you should try to get rid of the irridium Plugs on the spray and possibly stick to the ur4's or autolite equiv. that dennis mentioned.


Greg

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http://www.youtube.com/hyperpack

Nitrous will change the sound of the motor, but it just gets deeper and louder. If anything it will be crisper than on muscle only. (Since no one actually answered that part)

Oh yeah, go 2 steps colder on pugs and gap them at .025". Trust me, you don't want a plug to get wet and go out with the hose on.

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Official Cookie and Mater Tormentor.