Bigger Turbo with Nitrous????

[jgkurz]

Hi all,

Someday I'm planning to add nitrous oxide to my Z. At this point I'm not sure which system or HP level I will chose. I'll probably go with a dry setup and extremely large injectors. My current turbo will support a maximum of 400 flywheel HP. If I'm already making close to 400HP I'm wondering if adding nitrous would necessitate a larger turbo? I'm not an expert, but in theory I should not need a larger turbo. If I understand how nitrous works, the additional power is from being an oxidizer. This means N2O actually adds oxygen to the combustion burn. So if I'm correct, adding more a larger turbo would probably not be required.

 

Am I in left field?

Thanks,

[Guest Zcarsmakemyheadhurt]

Your right, do it on a wet system.

 

Alex C

[1FASTKINGCAB]

Most of the HP you get from NOS is due to the much MUCH colder intake charge entering the engine. and the added O² helps too. But for sure got with a WET kit. Larger injectors will have your car running hella rich off the bottle and you won't have the added HP/Torque control of a wet kit. A higher NOS to Fuel ratio and you'll get more HP than torque when on the bottle and a lower NOS:Fuel will give you more torque.

 

Also, (not 100% sure though) When it is said that your turbo is good for 400hp I belive that only counts when the turbo is the power adder bringing your N/A motor up to 400HP. If you where to throw a 50 or 75 shot on top of you 400hp turbo I'm sure you would hit the 450-475hp out of it. if that all made sense

[BLKMGK]

Horsepower increase from nitrous is PRIMARILY from the added oxygen content when the oxygen breaks it's bond with the nitrogen. The cooling is nice but it's FAR from the biggest part of the power increase

 

A wet kit is fine until you have to worry about mixture distribution issues and intake wall wetting. I personally get the heebie jeebies thinking about a dry system. You won't want a big shot anyway, say 50-75HP to spool the turbo more quickly, wet is fine for that IMO. I'd bet that if he runs a 50 shot he sees at least 60-70HP, turbo cars seem to really love nitrous!

 

Big injectors idle and drive just like smaller injectors if you've got control of them. Injectors are NOT carb jets! I run 6 72lb injectors on a 3liter 2JZGTE motor and it idles 14.7:1 or leaner as I desire - no problem. I know guys running 1000cc injectors on the same type of motor daily driven idling just like mine. At some point you get so big the injector cannot be idled but that point is apparently fairly big. My injecotrs are Peak Hold with a resistor pack.

 

In a dry system the injector duty could be modified or the nitrous pill changed in order to change the A/F ratio.

[jgkurz]

Just for the sake of excess, let's say I'm going to use a 75hp shot or above. I believe I can handle as much as 72lb/min injectors on my L6 with the Tec3. If this is the case, and I can manage my A/F mixture properly, why would I want a wet system? I'm may be off base, but it seems like I could have more accurate control over my A/F mixture with a dry system. Thoughts?

 

By the way, I've never been able to get my car to idle smoothly at anything leaner than 13:1 A/F ratio.

 

Regards

[Guest Anonymous]

I belive that a dry system with your Tech 3 would be unduly complicated.A single fogger wet setup would be fairly straitforward.Done right it would be very entertaining.You don`t need a bigger turbo with nitrous.

[TimZ]

What is your plan for controlling the fuel mixture while the nitrous is on from the TECIII? I'm not seeing much that would give you terribly precise control in their software.

 

You could probably use the (inadequately documented) fuel enrichment function from one of the A/D inputs, but unless you have some sort of analog voltage that is proportional to the amount of Nitrous being injected, this will be pretty much the same as running a wet system, as far as precision goes. It's not like you are going to have a 16x16 trim map at your disposal - you will just have the one enrichment value that adds pulsewidth in proportion to the analog voltage at the input.

 

I guess that it wouldn't be much worse than a wet system, and far better than the enrichment methods traditionally used with dry systems, though.

 

You will still have potential problems with uneven cylinder to cylinder distribution of the nitrous, just as you would with a traditional dry system, and there is nothing that you can do about that, aside from running a seperate dry nossle at each cylinder.

[TimZ]

Okay, this would be kind of hokey, but if you did want a 16x16 map for your nitrous (I refuse to say NOS ) enrichment, you could probably put a low pass filter on one of your GPO outputs, gate it with your nitrous activation signal, and run that into your analog input. You could use a simple DPST relay for the gating function - just remember to ground the other relay contact so that you get a solid ground to the analog input when the nitrous is off.

 

You could do a pretty good job with a setup like this, although since you are going through a few stages in the analog domain, your precision won't be quite as good as it would be if you had a 16x16 map to access directly for this.

[jgkurz]

TimZ, For me it's either N20 or Nitrous...

 

As I read your posts and look further into controlling N20 with my Tec3 and it probably would need to be a "switched on" enrichment rather than the precide metering I had hoped for. Like you say, I could use a GPO pull to ground to close a relay. The relay would then activate an Analog input with a preset enrichment. This wouldn't be any better than a wet system. Oh well...it was a good discussion.

 

Do you think the O2 sensor could properly sense A/F ratio if I were to try an run in closed loop with the above setup? Currently I run closed loop from 1K RPM up.

 

By the way, are you able to get your car to idle at 14.7 with your Tec2?

 

Thanks!!!

[TimZ]

Originally posted by jgkurz:

As I read your posts and look further into controlling N20 with my Tec3 and it probably would need to be a "switched on" enrichment rather than the precide metering I had hoped for. Like you say, I could use a GPO pull to ground to close a relay. The relay would then activate an Analog input with a preset enrichment. This wouldn't be any better than a wet system. Oh well...it was a good discussion.

Now hold on, there - you would still use the normal type of activation switch system for the nitrous. The relay coil would be controlled by this same switch. When the nitrous was off, the relay would ground the analog input. When the nitrous was on, the relay would route the filtered GPO output to the analog input.

 

The idea is that if you low pass filter the PWM'ed GPO signal, you will end up with a DC voltage proportional to the duty cycle of the GPO output. For instance if your filter consisted of a resistor to +5V and a properly sized capacitor to ground, then 100% duty cycle would result 5Vdc at the filter output. 50% duty cycle would result in 2.5V. If you route this signal to the analog input, you could use it to dynamically modify the fuel mixture, using the fuel enrichment setting for that input.

 

Do you think the O2 sensor could properly sense A/F ratio if I were to try an run in closed loop with the above setup? Currently I run closed loop from 1K RPM up.

NO. Even with a wideband O2 sensor, the feedback loop is too slow to rely on for something like this.

 

By the way, are you able to get your car to idle at 14.7 with your Tec2?

Yes. Although I am currently switching over to a TWM induction setup, which nobody seems to be able to get to run that lean. With my ported stock intake manifold and 72lb injectors (running at 36psi, so more like 64lb), I was able to get stoich at idle. One very good trick is to use less ignition timing at idle (lowers the idle speed), and open the idle air bypass to let more air in (leans the mixure).