How safe is Nitrous on a stock GT?

[03Glock]

The thing to remember is you are not pulling timing only to make it safer, by reducing timing you are actualy allowing the car to make more power.

Never heard that B4.........

 

[matt texass]

The thing to remember is you are not pulling timing only to make it safer, by reducing timing you are actualy allowing the car to make more power.

 

[matt texass]

Never heard that B4.........

I actually had a long post about it earlier in this thread I believe.

 

[chopstix]

I actually had a long post about it earlier in this thread I believe.

http://s197forum.com/forum/showpost.php?p=234694&postcount=35

...wonder where you got that from

Once you understand cylinder pressure vs burn rate it all starts to make sense.

 

[Mustangfreak]

close but not 100% correct.

The rule of thumb is 1-2* per 50 HP....it will all depend on the car and what is needed for that application.

I am currently pulling 8* from my base WOT timing for a 200 shot.

The thing to remember is you are not pulling timing only to make it safer, by reducing timing you are actualy allowing the car to make more power.

I'm asking this again because I want a clean cut answer.

If I take my current 91 Race tune, and pull 4* of timing from 2000-8000, I will be good to spray a 100 wet? Nothing else for the tune right? I don't absolutly have to have a nitrous tune?

 

[chopstix]

I'm asking this again because I want a clean cut answer.

If I take my current 91 Race tune, and pull 4* of timing from 2000-8000, I will be good to spray a 100 wet? Nothing else for the tune right? I don't absolutly have to have a nitrous tune?

without knowing more about the car it is not possible to give you a clean cut answer.

1) What is the NA timing?
2) What is the NA A/F ratio?
3) What is the nitrous A/F ratio?
4) What spark plugs are you running?
5) Do the plugs show that they are the "right" heat range?

Now for a not quite clear cut answer....if the tune-up is correct as far as heat range and air fuel ratio...start by pulling 5-6* then watch for detonation and your HP output, I would start adding timing back to the motor until you find the sweet spot.
HP output can be determined by dyno reading or drag strip trap speed. Most likely 4* from your NA tune will be OK, but I cannot insure you will not have a problem. But if you follow these guidelines I can tell you that you will have years of nitrous enjoyment.

Every car will be different, even the same car at different HP levels will like different timing retard amounts.

Learning to read spark plugs will tell you exactly what the motor wants. The plug is your "eye" into the combustion chamber. Install fresh plugs then make a WOT pull, immediately kill the engine and coast to a stop. Then pull the plugs, by looking at the ground strap will tell you heat range, the plugs base ring will tell you A/F ratio, and the porcelin will tell you if you are getting detonation/preignition.

Here is a good link for learning to read plugs....

http://members.uia.net/pkelley2/sparkplugreading.html

 

[Mustangfreak]

without knowing more about the car it is not possible to give you a clean cut answer.

1) What is the NA timing?
2) What is the NA A/F ratio?
3) What is the nitrous A/F ratio?
4) What spark plugs are you running?
5) Do the plugs show that they are the "right" heat range?

Now for a not quite clear cut answer....if the tune-up is correct as far as heat range and air fuel ratio...start by pulling 5-6* then watch for detonation and your HP output, I would start adding timing back to the motor until you find the sweet spot.
HP output can be determined by dyno reading or drag strip trap speed. Most likely 4* from your NA tune will be OK, but I cannot insure you will not have a problem. But if you follow these guidelines I can tell you that you will have years of nitrous enjoyment.

Every car will be different, even the same car at different HP levels will like different timing retard amounts.

Learning to read spark plugs will tell you exactly what the motor wants. The plug is your "eye" into the combustion chamber. Install fresh plugs then make a WOT pull, immediately kill the engine and coast to a stop. Then pull the plugs, by looking at the ground strap will tell you heat range, the plugs base ring will tell you A/F ratio, and the porcelin will tell you if you are getting detonation/preignition.

Here is a good link for learning to read plugs....

http://members.uia.net/pkelley2/sparkplugreading.html

I'm not going to be able to do a WOT and immidiatly shut the motor off.

 

[MrClean]

ive ran nitrous on my s197 ever since i got it. 75shot no tune needed.. 100shot ur gonna want a custom tune and spark plugs that are one heat range colder. ive been running 100 on it for the last 2 years, and has probably seen about 20 bottle fills. made 390whp 460rwtq through the auto tranny.. and ran 12.3 @ 118 on stock tires.

i wouldnt go over a 125 with stock fuel pumps. even with pumps, anything above 150 is risking it.

Yeah, I got the GT40 fuel pump for added insurance...and the cooler plugs.

 

[MrClean]

I run my 91 Bama race tune when not spraying and it is hot. I love it. Do you have his race tune?

Yes, I have his 93 Perf, 93 Race, 93 Torque, and 87 Perf tunes, but my favorites is the torque tune...I Think I'll datalog it with -7º and see if I can approximate what I datalogged on the 87 Perf-4º 9 (between 17º and 21º spark advance). I thinkj his torque tune does something to the variable cam timing to increase the low-end torque. A;ternatively, I can just run the 93 tq tune w/o spraying for daily driving...the problem is that I like having the NOS valve on in case "business" crops up (pesky C5 vette, etc).

 

[MrClean]

I actually had a long post about it earlier in this thread I believe.

Outstanding post Matt, BTW.....that is what got me to pull the 4º even though when I dynoed it (383 whp with a cold bottle, 402 whp with a warm bottle) I had the Bama Perf 87 with no timing backed off (but running 93 octane fuel)

 

[MrClean]

I'm asking this again because I want a clean cut answer.

If I take my current 91 Race tune, and pull 4* of timing from 2000-8000, I will be good to spray a 100 wet? Nothing else for the tune right? I don't absolutly have to have a nitrous tune?

Ok, this is about as clear cut as you'll probably get. DISCLAIMER #1: Every engine has a different '"tolerance" for different parameters. My engine doesn't like timing with a big MAF housing when NA, it pings like crazy. I had to use the AirAid CAI with the insert in for it to be able to run Bama's 93 Race, 93 Perf, and 93 Torque tune without detonation. This is probably due to a higher compression ratio than other motors.DISCLAIMER #2: I'm runnign a GT40 fuel pump and cooler plugs (for my 125 shot)Having said that, here are my current parameters:- I'm running 93 Octane fuel (ONLY Chevron)- I'm running Bamachips 87 Tune with -4º- I'm running a ZEX 125 ShotChanges from mine to yours:- Your running the Perf 91 tune (rule of thumb is 2 points of r+m/2 octane is = to 1º of timing, so you're 4 points higher, so you would have to pull 2º more than I'm pulling.- You're running a 100 shot instead of the 125 I'm running/ The ZEX manual says no timing pulled for 75 shot, 2º pulled for 100 shot and 4º pulled for a 125 shot, so you would be able to add back 2ºIf you follow that logic, even though you're only pulling 4º, you could run the 91 tune because instead of my 125 shot, your'e spraying a 100 shot.Does that make sense? Maybe you should try -5º first, then "graduate" to -4º.One thing I would do is get in 4th gear, close the windows, turn off the radio (and make sure you don't have a chatterbox woman next to you), and get to 3000 rpm, and hit the spray, and as the revs climb, carefully listen for ping/knock. Good luck.

 

[chopstix]

I'm not going to be able to do a WOT and immidiatly shut the motor off.

Please explain why you can't ???

This can be done at the track or a deserted stretch of road....it doesn't have to be a 1-4 gear pull...just a few seconds in your 1:1 gear. You also don't have to pull every single plug. It is best if you can but pulling 2 or 3 is better than nothing at all.

You also don't need to do this every time you run, only to get your base tune-up set.

Another option to insure proper timing and A/F ratio is to use some type of datalogging and a wideband O2 sensor. This way you can watch for knock retard and directly monitor A/F ratio.

KR can be watched through an OBD2 scanner or datlogger, and good widebands can be purchased around the $2-300 mark. Some wideband controller can even datalog so you can easilly go back and look at the A/F over time.

I know this seems like a very in depth procedure to go through...but please realize that I am trying to show the proper way to "tune" a nitrous car. For those that don't know me I have been using nitrous on my own cars for almost 10 years now. My current car is a purpose built nitrous application that I will be doubling the NA HP output with nitrous...this means I will be running more HP in nitrous than the 4.6L 3v engine makes.

 

[chopstix]

The ZEX manual says no timing pulled for 75 shot, 2º pulled for 100 shot and 4º pulled for a 125 shot

This is assuming a stock tune...for examples sake lets assume the following

Aftermarket tune has advanced the timing 2* from the OEM setting.
To follow the ZEX guidelines you would need to run the following.
-2* for 75HP
-4* for 100HP
-6* for 125HP

This is a rough starting point to begin dialing in the correct combination between timing and fuel jetting.

For those running the ZEX kit please note that the NMU has no way of monitoring A/F to adjust the mixture. Not knocking the ZEX kits they just have, shall we say, creative marketing.

 

[MrClean]

This is assuming a stock tune...for examples sake lets assume the following

Aftermarket tune has advanced the timing 2* from the OEM setting.
To follow the ZEX guidelines you would need to run the following.
-2* for 75HP
-4* for 100HP
-6* for 125HP

This is a rough starting point to begin dialing in the correct combination between timing and fuel jetting.

For those running the ZEX kit please note that the NMU has no way of monitoring A/F to adjust the mixture. Not knocking the ZEX kits they just have, shall we say, creative marketing.

Correct. The only thing the ZEX NMU adjusts is the amount of fuel injected as the NOS pressure decreases, to avoid dumping fuel when the NOS runs out.I'm running 93 Octane, on an 87 tune (roughly equal to -3º), and -4º on the tune, so essentially I"m at -7º. I guess I could add back 1º ? (BTW, the degree sign "º" is Alt+167)

 

[Bkid]

I'm asking this again because I want a clean cut answer.

If I take my current 91 Race tune, and pull 4* of timing from 2000-8000, I will be good to spray a 100 wet? Nothing else for the tune right? I don't absolutely have to have a nitrous tune?

NO you can not run a race tune with timing pulled. You have to have a nitrous tune specifically made for your car. You can blow your motor up.

 

[chopstix]

NO you can not run a race tune with timing pulled. You have to have a nitrous tune specifically made for your car. You can blow your motor up.

And just why is this.....????

The only difference in my "tune"...I.E. the engine control parameters..... between a motor pass and a nitrous pass on my car is the timing retard.

 

[MrClean]

NO you can not run a race tune with timing pulled. You have to have a nitrous tune specifically made for your car. You can blow your motor up.

Actually, Doug on his website claims the only difference between his Perf 93 and Race 93 tunes is the throttle response. He says the timing is the same for both.

However, Bkid is right; get a dynotune done. It will also help you maximize low end torque to enhance drivability when not spraying (I think they can play with the variable cam timing, etc). I think I'm going to get PSI in Webster to do it. Probably run me ~$400, but should be worthwhile. Richard at Strictly is a good tuner and knows his stuff too, but I get the impression he's a little more of a "cowboy"...

 

[MrClean]

Nice thing about the Harris plate is it sprays full 360 degree's.

Does anyone have a pic of this HSW plate installed? I'd like the nozzles to be on the driver's side (fuel rail side), not the passsenger side. Do both sides of he plate look that same? Can it be installed either way?

I'm seriously considering getting this piece prior to getting my dynotune...so that the tune is done with the improved atomization in place.

 

[Bkid]

Mr CLean I would go with Richards tune any day. He is one of the few in the country I would let tune my car. I would stick with a fogger as well. You will be happier .

 

[Bkid]

And just why is this.....????

The only difference in my "tune"...I.E. the engine control parameters..... between a motor pass and a nitrous pass on my car is the timing retard.

Well you need to figure on A/F which is very important. I hope you have a wideband A/F guage. STILL you need a good tune, I just would reather be safe than replacing a motor . I am only trying to help .