NOS question

wannaberacer · 02-11-2002, 03:39 PM

I'm just about to put in my rebuilt head, cam, new lifters, springs and water pump onto my car. All this at about $600 less than I thought it would.So I was thinking that maybe I could put in 65 shot of Zex to make sure I would blow a few fenders of the local import crowd. The thing I'm worried about is my bottom end has 118k miles on it, and about 225hp with nitrous. I just don't know if my motor will last with VERY sparatic use of it. The other thing is that I have a friend who says he knows people who have broken gears with nitrous, especially 5th. Can that be true of an 84' gearbox??

pete13 · 02-11-2002, 04:41 PM

....it's spelled "sporadic" instead of "sparatic".....

Britwrench · 02-11-2002, 05:26 PM

it's spelt....anyone got a trans for sale?

Roger Hall · 02-11-2002, 06:09 PM

dont do it that $600 could cost you thousands more

PorscheG96 · 02-11-2002, 06:31 PM

How much have you read about Nitrous applications? You'd be a better judge than anyone else concerning the strength of your bottom-end. A 75 shot like you're suggesting definitely won't kill the engine if you have everything tuned correctly, did you have cams and valve springs installed with Nitrous in mind? You'll kill the ring and pinion of the NA gearbox before you break a gear...

Devildog2067 · 02-11-2002, 06:48 PM

You wanna explain to me WHAT THE HELL you're doing running nitrous in 5th gear?

I'm running a ~65 shot, haven't broken anything yet... my head and block are completely stock. Did a complete fuel system cleaning (but not an upgrade) before I put the NOS in, haven't had any problems.

Nitrous is for 2nd and 3rd gear only. Running it in 5th will probably cause your clutch to slip, among other things.

justin · justin's Garage

I am running the 65 shot also, and agree with Devildog, not one problem yet,but I barely use it too,and when I do it is very short bursts. 5-8 sec. max.

wannaberacer · 02-12-2002, 04:04 PM

Devildog,
Why can't you use it in fourth??? I also know more people who melt more pistons than tearing the ring and pinions off thier cars. But then again those cars are civics, probes, golfs, and not 944's.

BTW: The races I've been in hit far into 5th gear, so as for nitrous I now know that I shouldn't touch 5th(and 1st). But the people I know redline 4t with it. So I want to know why 4th couldn't be used.

Devildog2067 · 02-12-2002, 07:42 PM

You can use it in 4th, I guess... I never have, since 3rd gear is good to ~80-85 mph...

I don't use NOS in 1st because it's too easy to bump the rev lmiiter in 1st, and that will instantly grenade your engine (supercritical lean = detonation = blown head + holes in pistons + other bad stuff). Besides, it's easier to get a smooth launch by simply revving slightly (I go to about 2.5k, so as not to beat the clutch up TOO much). Launches with lots of power are harder to control.

5th is a bad idea, it's a really tall gear designed for cruising and doesn't take the high hp and torque very well.

2, 3, and 4 are ok... I just don't use it in 4, like I said. 3 at redline is fast enough.

TheStig · 02-13-2002, 08:19 AM

ehhh you'll blow your head gasket on the car thats the worse case scenario of using 65 shot several times. put a widefire headgasket on the car. Oh and the 5th gear thing....are you guys sure that causes a clutch to slip? or could it be because of the crappy factory rubber center and the lack of a spring centered one...i'm asking this cuz i will be using nitrous later on and i will be installing a carbon kevlar spring centered clutch

Devildog2067 · 02-13-2002, 08:57 AM

Nope. Bump the rev limiter in a 944 and the DME does what? Shuts the fuel off. Completely.

Now you've got a cylinder full of hot air and pure o2 and gasoline fumes. Super insanely lean mixture. That leads to detonation and all kinds of bad stuff. How's a widefire headgasket going to fix that?

The key to running NOS successfully is fuel control...

The clutch hub doesn't have a whole lot to do with whether the clutch will slip or not. It's a function of the clamping force; the clutch hub affects clutch engagment mostly (unless the rubber clutch center grenades).

Besides, I have a sping-centered Sachs clutch, and hitting the juice in 5th will cause mine to slip.

wannaberacer · 02-13-2002, 12:15 PM

devildogg,
Well you anwered my clutch question that I didn't ask( I also put a sachs in). But I have another, its if you powershift with nitrous?? I think your answer would be no, but I think a few poeple who do use nitrous would say yes. If that's so, would even slightly redlining just once guarantee a blown widefire gasket??? Also note that there are companies(like zex) who make nos kits that run nitrous based on the amount of fuel going to the motor. Hence no fuel, no nos= no blown gaskets.

BTW; I suspect that when a tranny blows with nitrous, its because there wasn't a progressive boost controller involved in feeding nos to the motor. Some companies sell them for about $300, and its one of the rules I have heard when using nos.

Chouse · 02-13-2002, 03:11 PM

It's not that you'll blow the widefire gasket , but rather that the detonation that the super lean mixture produced will do alot of other things instead of blowing the headgasket, even with the stock one. When an engine goes lean and detinates, it will melt a hole through the piston. My understanding is that detonation is basically pre-ignition, with a mixture that lean the gases will ignite too early, when the piston is still too early on the upstroke, as its compressing the gas. The lean mixture creates a hotter than normal combustion, which is made even hotter due to the still increasing pressure. This will melt a rather nice hole in your aluminum piston. Also since the explosion tries to push the piston back down too early, it will insanely increase the wear rate on your bearings. I found this out on my G60 Corrado (no NOS), which one late night after doing the timeing belt and water pump, I was too lazy to check my ignition timing, I did it a few days later, but i had done enough damage that about a month later, it wouldn't run and I found a nice 1/4 inch hole down the side of one piston, and a slightly smaller one in another, and my bearings were pretty shot (down to the bronze on the upper rod sides). So as long as you have enoguh fuel to keep the correct air/fuel ratio with the nitrous, you shouldn't have a problem, but if go lean while feeding nitrous, or your timing is overadvanced, you end up with holy pistons. (No, you won't go faster becuase they're lighter)

Eturbo924 · 02-14-2002, 06:35 AM

Britwrench You noted anyone selling a transmission. I can get you a 1987 924S transmission with 53K miles on it for $450 Plus S&H. Remember this will give 944 superior power in 5th gear due to the 924S shorter gearing. Easy bolt on upgrade to 944 highway performance.

Let me know if you are interested.

Eric
Eric.Lynch@itt.com

Afterburner951NOS · 02-14-2002, 08:02 AM

I currently do not have NOS in my 951 but did on my other car. I would not recomend NOS on an older car unless the engine is very strong and has a new water/fuel pump and all new seals wich can get pricy. I mainly used NOS in 3rd or 4th gears for an extra boost but I would modify you car in other, less dangerous was such as a chip or a MAF or a larger intercooler combined with a larger turbo.