Hot air NOS/timing question

[tony taylor]

Hello guys,

I have an 84 hot air with a 33 turbo, 36# injectors, Lee Thompson 3"DP, 2 1/2" up pipe, 30 over block, built bottom end with Diamond forged pistons, ported and polished heads, 3 angle valve job, 212/218 cam, Lee Thompson built trans with 3300 stall, and a 1987 computer with 26 degree timing in 1st and 2nd gear, 23 degrees of timing in 3rd and OD. I want to spray 80-100 shot of NOS after the turbo. I run 116 octane in the car.

I plan to run 23-25 pounds of boost off the bottle.

I would like to know what is a safe boost number to run on the bottle?

Do I have too much timing?

On an old setup, all stock except for drag chip, I ran an 80 shot before the turbo and on 110 octane at 17 pounds of boost with no issues.

I would appreciate any advice...

Thanks,
Tony
NOS4LYF

 

[burnout]

I would start off with 18 degrees of ttiming and 15lb of boost and work your way up.


Burnout

 

[racemybuick]

I dont usually hear anything about NOS in our cars. I considered 100 shot myself, but I have seen huge gains from alky injection at a fraction of the cost in comparison to NOS. I am opting for alky right now, but if you get some time slips and report back here, I just might be knocking on your door for info!!! lol. i have to agree with burnout though, it seems that if you start off @ a base of 18*, and boost set for 15lbs, you'll get some better numbers to work with the tuning and drivability. After that, follow a pattern of advancement until you get the NOS in optimal conditions. I think with a 33 turbo, 22-23 lbs is a good zone to end up in from what I have learned from other users of that turbo and the racegas application. As for the timing, I would play it out as you creep the boost level up. I expect there might be some knock or detonation issue at the higher levels, but like I said, I dont know much about the NOS venue. Good luck.

John

 

[Lee Thompson]

Tony!!!!!

Now that we have added somewhere in the neighbor of 100 HP to your car, I was hopeing you would throw the NOS away. It is almost Unamerican to run a killer turbo and NOS!!!

 

[WhiteT78Supra]

Tony,

I think you will be just fine if you start out with the boost set at about 18 pounds to start with and work your way up from there, just make sure you have some 116 octane in the tank and monitor knock. I think you are OK on the timing.

All alcohol injection does is raise the octane. It does not add more oxygen.
Nitrous oxide adds more oxygen and will help cool down the intake charge. You need more oxygen so you can add more fuel in order to make more power.

Spraying is a good thing on a non-intercooled car.

 

[buickpower]

alky doesn't add octane in the most literal sense, it cools the intake charge, making it much more resistant to knock , almost like an intercooler in a bottle. In a way i guess this could be considered like adding "octane", i never quite thought of it like that.

 

[6SENSE]

Primary reason for alky injection, and sole reason I got into it, is to cool the air charge. Cooler [more dense] air = more hp and less detonation. Fueling is an additional benefit (especially with methanol, or denatured). Alky and NOS are to totaly different things. It seems that alot of people have the wrong notion about alcohol injection. Its not power in a bottle like NOS (by the way bottles ARE for babies ), but it makes available the opportunity for much much more power

 

[cool 84]

I don't like nitrous but I have a little experience with it. My dad's hotair came with a 100shot and a nitrous chip when we bought it. For what it's worth the chip had 18 degrees of timing so the advise you've been given is pretty good.

Methanol is around 130 octane so it does add some octane. We've also seen intake charge temps below ambient spraying methanol on the intercooled car on a 22psi run. I think that says a lot about the cooling properties. Right now on the daily driver we're running 24 degrees of timing with 22psi on 91 octane with no knock with methanol injection. The 1 gallon reservoir has lasted a months so far.

Another thing to consider is with nitrous the stock wastegate can't always keep good control over the boost. You can end up with big boost spikes or just uncontrollable boost. You might possibly have to go with an external gate. If you were planning on running a 100 shot, why not run a TA62 or something in that range?

 

[WFO]

Originally posted by cool 84
We've also seen intake charge temps below ambient spraying methanol on the intercooled car on a 22psi run. I think that says a lot about the cooling properties.

FWIW...on Derek's MKIV Supra we saw temps in the low-30º's spraying methanol...this was on a nice warm ~80º night running some decent(26+) boost.

It also acts as it's own fuel enrichment,as was already stated.

 

[WhiteT78Supra]

Alky injection primarily allows you to increase boost by 5-7 psi over the point were knock starts on pump gas. It does cool the intake charge somewhat. The main reason you would run alcohol injection is if you want to run more boost on pump gas or if you are pushing the limits of your fuel system. Think of it as an octane booster that also reduces the intake charge temp.

If you go to alcycontrol.com even they market it as an octane booster that will cool intake temperatures.

Nitrous oxide on the other hand is composed of 2 parts nitrogen and one part oxygen (36% oxygen by weight). During the combustion process in an engine, at about 572 degrees F, nitrous breaks down and releases oxygen. This extra oxygen creates huge additional power gains by allowing more fuel to be burned. Nitrogen acts to buffer, or dampen the increased cylinder pressures helping to control the combustion process.

Nitrous also has a tremendous "intercooling" effect by reducing intake charge temperatures by 75 to 90 degrees F. Nitrous is also widely used to quickly spool up larger turbos so as to minimize “turbo lag.”

I think it would be pretty cool to spray both at the same time.

 

[cool 84]

I realize methanol and nitrous are two completely different things. I guess my point was that with a motor that flows a lot of air like with ported heads/intake/cam/big turbo, being able to turn the boost up another 7 psi could very possibly add 100hp.

I know everyone says nitrous, when tuned properly is safe but in the real world I've seen too many engine failures using it. Turbos are gentler on the motor at the same hp level. I worked at a speed shop and I've seen first hand the difference in the two.

 

[WhiteT78Supra]

I agree that methanol will let you run more boost than just pump gas alone. I believe it will have very little gains on a car that is runing 116 octane.
I would think that if he runs 25 pounds of boost off the bottle and has no knock issues spraying methanol will not give that much of a gain. He may gain 15-20ish hp from the small amount of cooling the methanol provides.
The nitrous should provide a lot more cooling benefit as well as the chemical power potential, even if he has to turn the boost down a little, the nitrous will still provide more power than high boost alone.

 

[WhiteT78Supra]

You are right that boost is easier on the engine than nitrous.

I too have seen a lot of people gernade a motor on the bottle.

I havent heard of many turbo guys that broke pistons or rods from just the shock of a small to mid size nitrous shot coming on. Most of our cars, turbo guys, have the good forged internal parts in them from the factory. His car is built with all of the good stuff.

Most of the horror stories I have heard of were lean / fuel related problems with cars that had cast pistons and weak rods. Too high EGT's can melt a piston so even if you have strong parts in your engine you still have to run good gas and back out if you see knock.

You do have to make sure you have a good reliable way of monitoring knock as well as EGT's so you dont shock a piston hard enough to break a ring land or bend a rod.

If you are careful you can do it reliably.

I know Titan Motorsports Sprayed a 300 shot an a little internally stock 183 cu in Supra bottom end to spool their T88H turbo for some time before it gave out.
Not saying to spray that much, but I think a stout / built GN motor should be able to hold up to a 80 - 100 shot with no problem as long as you are careful.