75 shot, tune needed?

[g3t_t0rk]

Hello again, all! My question today is this; for a 75 shot of nitrous, is a tune needed? Mods are K&N intake, Mopar race exhaust, and email canned SCT tune. My friend who's running a 550whp E55 AMG says I don't need a tune, just some good gas however, I know these motors aren't cheap and I just wanted to make sure I'll be alright. Also, I'm guessing with a 75 shot and my current mods, I'll be around 550whp/600wtq? I made 454whp/486wtq stock. Nitrous gurus, please post up! Thanks in advance

 

[plumcrazy]

dyno tune = ~ $300, you can gamble, i wouldnt

BTW, if its a dry shot, you DEFINITELY need a tune. but i would never use a dry shot on a NA viper.

 

[345s-bspinnin]

Most "tunes" are more aggressive on ignition timing and leaner on the air/fuel; both which are typically big negatives for nitrous use. You also need to evaluate your friends knowledge with respect to his "good gas" advise. Most race fuels have a leaner stoichiometric levels under the same demanded mixture. In other words, if you simply move from 93 to 116 fuel, you will run a lean mixture for that fuel. For example, if you are running a 13:1 on 93 (stoich= 14.7:1), most tuners would agree that its a reasonable ratio for an all motor setup. If you move up to race fuel, lets say VP109 (stoich = 13.4:1), that same 13:1 ratio is way very lean for a fuel whose stoich ratio is 13.4:1. Talk to your nitrous compnay,

I would recommend not a only a re-tune, but also colder spark plugs, rpm window switches, and other tools available to keep your engine in one piece.

My $.02. Good luck.

 

[g3t_t0rk]

Thanks for the .02 cents! It's a wet shot btw

 

[345s-bspinnin]

I just realized that I never finished my "talk to your nitrous company" thought....lol

For a wet shot, the typical kit is jet for 93 oct fuel. If you are going to use some sort of race fuel, be sure find the proper fuel jet for the intended shot size. Your nitrous company will be able to guide you. Even with a wet kit, I STRONGLY recommend a window switch. I would for an engine to be lost just because a mis-shift while the solenoids are spraying.

 

[anton28]

Colder plug and -2 degree timing is a must assuming your running a wet kit. I ran nitrous on my 396 stroked firebird. I put 100s of bottles through that engine and when it was time to pull the motor and sell it, we did a compression test and it was in great condition. I ran a MSD 6bt box which I set up to tetard my timing 2 degrees everytime I engaged the nitrous system along with a colder plug. I was running 150 shoot. Another important factor that everyone overlooks is the bottle temp which affects the bottle pressure. You have to be in a 950psi range so make sure you get a bottle warmer.

I'm in Cali so 91 octane is the best fuel we can get so I always ran fuel additives that boosted my octane to 105.

 

[plumcrazy]

not all nitrous cars need colder plugs. you wont know till you tune and drive it. a 75 shot is pretty tame compared to 200 shot. my 200 shot did not run better with one or two step colder plugs

 

[anton28]

Your right. I was just reffering to my personal experience and the info I have gathered over the years. I personally would run a colder plug either way.

 

[g3t_t0rk]

I got the kit today from my friend. He was kind enough to do all the wiring for me as well! Only thing I'm missing now is the jets, tune, and the window switch. The kit is from NOS and from what I see, I'll probably be wanting to run a 42 jet for the nitrous and a 28 jet for the fuel. I'll be playing with a few different jets just to make sure the AFR is nice and neat. I'll definitely be getting a tune to pull 2 degrees of timing as well. Just to be certain, the stock fuel pressure is 55-58 psi, correct? Thanks again for the advice!

 

[Nine Ball]

You will want a WOT switch and a window switch.

 

[plumcrazy]

WOT and window are a must IMO

 

[g3t_t0rk]

I'm working on the window switch. Trying to order one and figure out how to wire it in. Do I wire it into the 4 cylinder coilpack and run it as a 2 cylinder? Read that somewhere with the Gen 2's... Also for a 75 shot, does the .042 cover the nitrous side/ .028 jet for the fuel side?

 

[plumcrazy]

mine was setup different so i cant say. but if i recall jackB has some great wiring diagrams and is a wealth of knowledge in this area. look thru his gallery for answers

 

[Nine Ball]

From this thread:

http://forums.viperclub.org/threads/633669-Shift-Light-Installation?highlight=tach+signal

I followed the suggestion on reply #18. There isn't currently a wire in Pin #31 on the factory harness plug. I removed the harness from the ECM, then I had to drill a tiny hole in the backside that corresponded with Pin 31, and insert my own female pin and wire. It is the tach signal. Then set the shift lite to 5 cyl mode.

I bought a wire plug kit like this from Radio Shack and just robbed one of the brass pins from the set. Soldered a wire to it. I run my window switch and my shift lite off of this signal.

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