ToyotaSupra

iTrader: (1)

Ok...as some of you know I posted on here before about my nitrous problems.

I have a 1998 Toyota Supra non-turbo. I have a NX complete nitrous kit with bottle heater, purge, all that jazz.

I have a msd ignition system retarded to 7 degrees(for 150 shot) and I am running 2 step colder plugs-NGK 6097's

I also have a MSD window switch set to 3200-6000 and a WOT switch for the nitrous.

As most of you recommended that it was definately my fuel pump running out of fuel causing my car to go lean and causing the intake backfire......

So....I just installed a 700hp denso fuel pump and hotwired it for the voltage needed. The car still has the intake backfire. I've gone through 3 MAS's and 4 intake filters already from the backfire blowing them to pieces

So you can rule the fuel out of the question....I am also running 100 octane fuel.

The car did fine on the dyno of 150 shot. The car does fine on the road with a 75 shot and worked a couple times on the 100 shot but the 150 is not working on the street.....backfiring.

I have 45psi fuel pressure and am running 62N and 35F. I also have a bottle heater and pressure is around a perfect 950ish.

It has to be something with my ignition system/timing since its not the fuel.

Either that....or do you guys think my window switch is set too low of a rpm of 3200? Come to think of it, everytime the backfire occurs, its in the 3200-3400 rpm range. Should I try raising it to 3800? or 4000?

If raising the rpm's dont work, what else can you guys recommend????

Keep in mind I am also an automatic transmission if that makes a difference. The car seemed to have the nitrous backfire more when the car was in drive and automatically downshifted itself when I went WOT. And it did better when I put it in 2nd and went WOT...a lot smoother and worked for the 150 shot for the first 2 times....then didnt work anymore and nitrous backfired occured again.



Pic of the nitrous backfire destroying my MAS.....no point to take pictures of the intake filter, thats in a million pieces....



help guys

wyndzer

I kept having n2o backfires and it turned out that the Map sensor was hitting the firewall causing it to go lean and then it would backfire when the map would read correct again. Check to see that the map sensor is mounted solid and not hitting or vibrating under hard acceleration.

MikeD101898

iTrader: (5)

If it keeps happening at that exact RPM, then why not switch it up to around 3800-4k? You've got the RPM space, up to about 8k (depending on mods). Just a thought.

383LQ4SS

iTrader: (33)

ok...much better description of whats happening.

IMO you have to change HOW you operate the system.
If it were my car I would check the plugs and gap them tight. maybe .028

I would then set your window switch to spray at 4000 and above.

Next...dont arm the system and nail it while its in D and chugging along. If your an auto and just chugging along your should really select the appropriate gear to get in your power band...then arm the system...then punch it.
if you cant select the correct gear due to computer controlled tranny...slow down...select the gear...and then get back into your sweet spot of rpm in that gear you want to start in.

There is too much time required for a downshift to spray it in 4th gear chugging along.

If all this works out...i would still do a dual stage setup with a small shot at 3200 and another shot at 4600 or so.

Whats your redline?

ToyotaSupra

iTrader: (1)

First....my plugs are brand new and gapped to .028-NGK 6097's

Im going to see what happens with the window switch set at 4000, and if works, i'll try 3800 then 3600 and so on and probably stop at a low of 3500 if everything works out.

And like you said, instead of being in Drive, I will do it in 2nd and see how that goes.

860 Performance

iTrader: (1)

I previously posted this, but will say it again.
Check your intake valves. A backfire can push them into a piston on an interference motor (which i assume yours is) If they don't totaly seal, you will always have backfires.

It dosen't cost anything to check them (leak down test).

ToyotaSupra

iTrader: (1)

but it works perfectly on a 75 shot.......

860 Performance

iTrader: (1)

small problems escalate when using bigger jets. I went through a similar thing, and that was the problem.

Like I said, its free to check, so why not check it?
Vinny
let me know when you need my paypal address.

ToyotaSupra

iTrader: (1)

maybe i can try mounting my bottle at more of an angle too considering its pretty flat right now..which could be causing air in the lines from the nitrous not being able to get to the siphon tube properly.....which could be causing my nitrous not being able to keep up with my fuel, therefore, fuel puddling in my intake...

Makes sense to me...anybody else?

JustAnIlluzion

iTrader: (60)

check the intake valves like was said earlier

ToyotaSupra

iTrader: (1)

intake valves are fine.....checked. I think its something with the siphoning problem. My bottle was way too flat. I know have it elevated 3" in the front. I think this is going to do it guys! I'll let you know.

But in the meantime if anybody has more suggestions please let me know thanks!

tuff

iTrader: (15)

How doe's your timing file work on that motor?Is it a map (rpm vs load) What im thinking is the motor has to much load at that low of rpm and if your timing map is screwy it could be dumping to much timing at that low of rpm.I know you are taking out 7 degrees but that is only on top of the cell that the motor is hitting at that time.To rule the timing thing maybe take out more and try again.

5_02ls1

iTrader: (20)

this may be a stupid question have you tried re jetting the 150.say go up a size on the fuel if that dont work go down 1 size on the n20.most kits dont come with enough jets to properly tune the system

cantdrv65

iTrader: (3)

I think your problem is ignition timing......Its hard to say whether its too little or too much....It could be caused from either.


Have you checked the plug wires?

tuff

iTrader: (15)

Is your cams stock?If so were they ever out or was the cam timing ever altered.Also could check for a weak intake valve spring.How many miles on the valvetrain.This is just somthing else to check but i still think it is in the timing file.Is there anyway to verify that the timing is coming out and also check to see if the baseline timing is correct.Also you can try putting your map on a rubber hose and strapping it to something,vibration on the sensor direct off your intake can mess with your fueling and cause detonation.

ToyotaSupra

iTrader: (1)

I bought extra jets, so I have just about every possibility to try. 50,75,100,125, and 150.

I have a hard time believing its timing guys. I've tried every possibility. I've went from 4 degrees on a 150 shot to 7 degrees then even to 10 and 11 degrees. Same thing occurs no matter what...

As far as my plugs...they are brand new NGK 6097's(2 steps colder) and are perfectly fine.







But I really think I fixed the problem here with how I have this bottle mounted. At least I hope.

ToyotaSupra

iTrader: (1)

I think its the way my bottle was mounted. Since my trunk slants down going towards the front of the car, even with the elevated t clamps for the nitrous tank, it wasn't sitting at an angle really. It was pretty much flat and I didnt even realize it until I really started looking at it.

So I fabed up some wood blocks that would give the tank an additional 2" of angle. What I think was happening is the nitrous wasnt being able to get to the siphon tube correctly because of the flat angle I had on it. Which explains why the nitrous worked on the street with 150 shot for like 3-4 times and then didnt work the 5th time(repeated use)

Sure I had good bottle pressure the whole entire time, but that doesnt mean anything if its not getting to the siphon tube correctly. I'm also going to try raising my window switch rpm to 3600 or 3800 and try it again.

teal99camarov6

iTrader: (1)

do you have a purge solenoid and a bottle heater? Backfires happen when you dont purge.

Pro Stock John

iTrader: (34)

I doubt it's bottle angle.

What are you shifting at? I'd have the nitrous come on at 4200 and then you eliminate some things as root causes. Only thing I am wondering is, when you are in overdrive, and wack it, it would shift to second right? What rpm does it drop too? Does it shift fast, or hang a bit? Maybe fuel puddling from a slow shift? I also agree that maybe you need beefier and fresher valve springs. Also could just be your spark blowing out. can you hold 3rd gear and spray in that gear at a high rpm and avoid the backfire?

WhyHelloOfficer

iTrader: (5)

Not trying to be a dick -- but in the span of the hour and a half between when it was posted (and agreed with) you did the leakdown test? You are getting a lot of useful feedback from people, and it seems you're only taking the answers that you want to.

I am going to have to agree with the others, I'm doubting it is being caused by the bottle angle.

Also -- just because you've got the correct jets for a wet shot ranging from 50 to a 150, doesn't mean you have the correct jets for your setup. Jet increments usually increase by the .01 or .02 of an inch, and honestly to get it dialed in you might need to spend some time on a load dyno and play with the jetting in smaller increments.

When I was running the 'recommended' jetting for a 100 shot on my car I ended up having a backfire that claimed some lifters and a rocker. When I pulled the plugs the next day the plugs are extremely white. After I got it all put back together I finally got the car on a dyno, turned out I was leaning out almost 12.7 - 12.9. My jetting for the 100 shot ended up being a 52N and a 41F. There are quite a few variables, every car and fuel system are different.

I also think you need to look into upping your window switch to 4000. If it works there, why would you want to drop it down more? Leave it where it works. The difference in 300-400 rpms and the narrow gains in HP (along with increased stress on your bottom end) I really don't think would be worth it.

Have you checked your plugs after these repeated backfires? Are you replacing all six plugs everytime you have a backfire that claims the life of a air filter and mass air sensor? If not -- pull them and see how they look. In my experience a backfire is caused by a lean condition.