tuning with nitrous.

[compression]

does anybody have experience with nitrous on a moderatly modified dsm? i set the boost at 12 psi hit the nitrous (50 wet shot) and the boost shoots up to 25 psi (i run about 24 psi usually off the bottle ), is this normal? it felt fast and i logged it but the inconsistancy with the knock is driving me crazy , im almost 100% sure its the lifters throwing off the readings, 3-7k rpms ranges from 10 - 23 counts, then another log shows no knock until 5500 so i leave the tune from 5500 down the same and richen up the top end a little bit , knocked all the way this time, and my indc's were up in the 102% on 12 psi shot to 25, and the 50 shot , and its a wet shot right at the throttle body , i havent checked for boost leaks yet i suppose there could be a boost leak at the throttle body where i tapped for the fogger nozzle, but off the bottle it runs fine. i bought this kit for like 300 bucks, including the bottle, all brackets, fuel , nitrous ,and purge solenoid all the lines and jets everything. plus i just wanted to break 11's but not until i figure this thing out. i guess im just asking for experience or any kind of help or hints for tuning with nitrous.


thanks in advance tuners.

 

[GVR4592]

I've seen the boost creep up a couple psi with a 50 shot but nothing like what you are describing. Is the turbine housing ported? Does the boost creep at all without the nitrous?

To safely use a 50 shot of nitrous you should do a couple things. Get one heat range colder plugs, retard the timing 2-3 degrees(use the cas if you have to), and make sure your fuel system is up to the task.

 

[Kevin Jewer]

I would also HIGHLY recomend non-projected plugs (remove the P from the NGK part number). I'm thoroughly convinced that these plugs saved my motor twice. I've lost enough motor to know when they should pop, and I've made full quarter mile passes at 13.5:1 with 22 degrees of timing, EVO8 turbo completely maxed out (vac line pulled off WGA), plus a 75 shot. I was running BR8ES plugs, and they didn't even look like they were overheated, never mind not coming apart, which is what usually happens to me.

I can't comment on the boost rising unfortunately, since I run the turbo completely maxed out anyway... But that does seem like an awfuly big jump.

Only tips I can offer are to get the jetting set so that AFR doesn't change when the nitrous comes on, or it goes a little richer if that's what you want, so when it comes on you don't have to completely retune. And watch bottle pressure. The two times I ran very lean was due to higher bottle pressure than when I set the jetting up in the cooler weather. It has a huge effect on AFR.

 

[red91gst]

I would also HIGHLY recomend non-projected plugs (remove the P from the NGK part number). I'm thoroughly convinced that these plugs saved my motor twice. I've lost enough motor to know when they should pop, and I've made full quarter mile passes at 13.5:1 with 22 degrees of timing, EVO8 turbo completely maxed out (vac line pulled off WGA), plus a 75 shot. I was running BR8ES plugs, and they didn't even look like they were overheated, never mind not coming apart, which is what usually happens to me.

I can't comment on the boost rising unfortunately, since I run the turbo completely maxed out anyway... But that does seem like an awfuly big jump.

Only tips I can offer are to get the jetting set so that AFR doesn't change when the nitrous comes on, or it goes a little richer if that's what you want, so when it comes on you don't have to completely retune. And watch bottle pressure. The two times I ran very lean was due to higher bottle pressure than when I set the jetting up in the cooler weather. It has a huge effect on AFR.

Kevin, your still be Hero, you know that right?

Not sure about the rest of the guys, but I always start with one lower fuel jet on nitrous setups for turbo/boosted cars. ie. on a 100shot setup I would use the recommened 100shot nitrous and the next lower fuel jet, usually a 75 shot fuel.

I agree with Kevin and thats why I set the jets up that way. Jet the car so that there is as little change in AFR as possible when the nitrous comes on.

Nate
TPG Tuning
Home of the World's Fastests Pump Gas 4cyl
10.65 at 133

 

[sbiggi]

My boost will raise when I use nitrous. 55 dry shot.

I've never tried it at low boost to see how much, but I usually see a good 1-2 psi spike initially.

If yours raises that much you need to do some porting. your wastegaste is not flowing nearly enough.

Also, I dont think you want the nitrous right at the throttle body, you might get uneven distribution. I set mine as far back as I could which was about 6"