TNT nitrous dyno run.....graph looks similar to 2001 GTS'.....

[kwkshift]

My '97 GTS now has a TNT nitrous sytem on it. We took it to the dyno this evening to see what it's doing. This is the first time I've ever dyno'd my car at this location and the 2nd time dynoing it ever. The car has a K&N intake setup, a B&B exhaust and Autolite 3923 plugs in it. This graph is the baseline pull and the final nitrous pull. the system is jetted for a 150 shot, but the A/F does some funny stuff. The graph looks a lot like "2001 GTS'" nitrous dyno.



The bottle pressure was @ 975 psi. The jets are .025 fuel and a .042 nitrous. These are SAE numbers.

Is there any way to smooth out the nitrous run? The TNT systems, from what I was told run quite rich and they like lots of bottle pressure to help compensate. On the baseline run, it looks like the car is running lean by itself. But then with the nitrous there is a lean spike when the system hits and then it goes very rich.

What do you think?

Thanks for the replies!

[bwhitmore]

I used to run a TNT system on my 2001 Z06. The kits do run rich, which isn't necessarily a bad thing, as I would much rather run rich than lean. But what is a little un-nerving about the graph is it appears to bottom out, which makes you wonder if in fact is going richer.

This is a graph of my Z06 on a 100hp shot back in May of '02. The bottle pressure was about 1075psi. As you can see the graph was a lot smoother.



I would suggest you try to get the bottle pressure up a bit more. Either with a bottle heater or simply with the sunshine. Really anything under about 1100psi will work just fine on a TNT system. The last thing I would do is mess with the jetting.

Those numbers though are pretty awesome though, it reminds me of why I got rid of my Z06.

[plumcrazy]

get a VEC2

[Jack B]

Kwkshift:

Plumcrazy is right, get a Vec2. A couple of questions:

1. What are the length of the lines from the solenoids to the nozzles.
2. What type of headers and exhausts do you have?

The next time the you dyno, tell the operator to turn the smoothing all the way off. Inherent to the dynojet brand a/f sensor, is the fact that it has a large time constant which means it reacts slowly so it kind of averages the a/f to begin with.

You can see that something is wrong because the inherent lean spike when the nitrous lands is not there. What has happened is the smoothing was on and it is averaging a fixed time prior to the rpm being read. This makes it very hard to assess the real a/f ratio. In general the dynojet sensor reads high at the start and low at the end.

I think if you use a more accurate a/f analyzer you will see you are not that lean initially. The issues with this curve are not TNT related is is just basic nitrous 101. Like Plumcrazy said, the VEC2 will help you by pulling fuel.

Once again, what are the lengths of the lines and what does the exhaust system look like. Just remember, a clean running nitrous install puts out a fixed hp, if that number is 100 hp, that 100 hp will be added throughout the curve. The exception would be if you have a poor exhaust system.

As far as pressure goes, it is only important as it relates to consistency. You can make as much hp at 800 psi if it is jetted correctly. If you are using a thermostaticaly controlled blanket, change the thermostat to a pressure switch. Take a look at the Dynotune website, lots of nice candy.

One last item, you may have been spraying gas instead of liquid when the nitous came on. The car stumbled (35 hp) and than recovered, you are lucky it didn't backfire. We all know it is hard to get the lines to the front without picking up heat. Just remember, you want to spray liquid nitrous, not gas. It is smart to lay out the system so it runs as cool as possible, otherwise, purge prior to a pull or race. If you had a change in phase due to temperature or a poor system design (like using a filter or a ninety) it might explain the car dropping below an a/f of 10. Contrary to belief, it is not gas that makes hp, it is liquid nitrous.

[kwkshift]

Kwkshift:

Plumcrazy is right, get a Vec2. A couple of questions:

1. What are the length of the lines from the solenoids to the nozzles.
2. What type of headers and exhausts do you have?

The next time the you dyno, tell the operator to turn the smoothing all the way off. Inherent to the dynojet brand a/f sensor, is the fact that it has a large time constant which means it reacts slowly so it kind of averages the a/f to begin with.

You can see that something is wrong because the inherent lean spike when the nitrous lands is not there. What has happened is the smoothing was on and it is averaging a fixed time prior to the rpm being read. This makes it very hard to assess the real a/f ratio. In general the dynojet sensor reads high at the start and low at the end.

I think if you use a more accurate a/f analyzer you will see you are not that lean initially. The issues with this curve are not TNT related is is just basic nitrous 101. Like Plumcrazy said, the VEC2 will help you by pulling fuel.

Once again, what are the lengths of the lines and what does the exhaust system look like. Just remember, a clean running nitrous install puts out a fixed hp, if that number is 100 hp, that 100 hp will be added throughout the curve. The exception would be if you have a poor exhaust system.

As far as pressure goes, it is only important as it relates to consistency. You can make as much hp at 800 psi if it is jetted correctly. If you are using a thermostaticaly controlled blanket, change the thermostat to a pressure switch. Take a look at the Dynotune website, lots of nice candy.

One last item, you may have been spraying gas instead of liquid when the nitous came on. The car stumbled (35 hp) and than recovered, you are lucky it didn't backfire. We all know it is hard to get the lines to the front without picking up heat. Just remember, you want to spray liquid nitrous, not gas. It is smart to lay out the system so it runs as cool as possible, otherwise, purge prior to a pull or race. If you had a change in phase due to temperature or a poor system design (like using a filter or a ninety) it might explain the car dropping below an a/f of 10. Contrary to belief, it is not gas that makes hp, it is liquid nitrous.

The length of the lines from the solenoids to the nozzles are about 18". I have stock headers and a 3" B&B catback. I think it may hve the high flow cats, but I'm not sure. I haven't pulled the side sills to check that out. The bottle heater is controlled via a pressure switch. It comes on @ 900 and turns off @ 1050. I talked to TNT yesterday and they said that they do make their systems run rich, but he said something is wrong with mine. He told me to check the ground on the N2O solenoid. I check it out and it, along with the fuel solenoid and the window switch are all grounded together at the stud on the frame rail just below the ECU/ fuse panel area. Before each pull, I purged the system so that a liquid "head" of nitrous was at the solenoid. There is no nitrous filter or funky fittings on the system.

I have WinPeP so I can view my runs. Below is another comparison. This is a 100 shot vs a 150 shot. I have turned the smoothing off, as well. They look almost identical!



Any other ideas?

[plumcrazy]

""It comes on @ 900 and turns off @ 1050""...too big of a gap if ya ask me.

my initial dyno run had that same drop. sean roe had to keep taking out fuel with the vec2 to get rid of it. but he WAS able to. when it would hit, you could really feel the drop in power, now its shoots straight up like its supposed to.

before the vec2 changes it was 602rwhp/820tq then after all the tuning and 20 pulls later i netted out at like 555rwhp/700tq but a smooth curve and safe tune.

then i made a bunch of changes, changed to a dyno tune pressure switch that keeps it at 1000-1050 consistantly with a digital nitrous pressure gauge,switched to using BOTH bottles at the same time for volume,got rid of the nitrous filter and then the numbers are what ya see in my sig.

im REALLY happy with the way it performs now. I've been able to beat a few much higher HP/lower torque cars on the street consistantly and safely.

[Jack B]

The smoothing I was talking about was during the run. I don't know why Dynojet does it, but, they apply smoothing during the pull. This is bad because it distorts the curve and cannot be removed when you view it. You also have to be careful, in general, their sensor/logic has a long time constant which means it is slow and cannot pick up everyting which is happening. I have been running a super fast a/f logger and it shows you what the Dynojet doesn't, and that is plenty. The next time you do a pull tell the operator to remove smoothing during the run, it will help, but, it is still not the best.

What is strange, on your 150 shot, it flows about 60 hp initially and then at 3600 it flow another 50 or so hp, then, the flow is reduced again. I can tell you this with 18" lines to the nozzles, there would be one large lean spike, because the nitrous beats the fuel to the tubes, however, the spike doesn't appear on the plot. That indicates the a/f sensor is not working correctly. Basically, the data tells us something is wrong, but, does not give us enough detail.

I had a similar problem to you, the solenoids were turning off. I changed them twice and went thru the wiring multiple time and couldn't find the isssue I decided to start fresh and installed the WON solenoids (from Racetested). They pull about 1/4 of the current of the conventional solenoids. I also do not use a frame ground to energize, I run two wires in all cases and all the ground wires come from one central ground terminal.

The last, but, it might be the most important is the power drop when you initiate the nitrous. This can turn into a backfire and you don't want that. To start with I would put in 36" lines (nitrous to nozzles) and would keep the fuel at 18", that at least will allow you to start without an initial lean condition. I would then rerun all the wiring, running two wires to each device. Run a #14 or #12 to the solenoids and the relay power. Once again, I believe that the NOS and NX solenoids have a lot of issues, one, being a large current inrush, this brings out the worst in a 12V electrical system with a common ground. If anyone want some almost new NOS solenoids, I have a bunch that I will let go cheap. I also have dozens of both NX and NOS jets that I want to get rid of.

[J DAWG]

Greg

On my TNT system I run a 46 nitrous and 25 fuel for a 150 shot. You stated you have a 42 pill in the car. May wanna switch to the larger pill so the top end doesnt get so fat.

Like Jack said you can try to go to a longer nitrous line which will help smooth out the lean spike but from what I have researched and after speaking with many people the lean spike is unfortuantely pretty common with many nitrous kits. It can be lessened with longer nitrous lines or even a VEC2 dumping fuel at that rpm which I have done.

I tune my NA for 12.8 and when the 150 shot hits it will end up around 10.5 at the upper rpms. TNT likes to stay on the rich side and that is where they get some pretty good torque numbers which is what you want.


Your car would benefit from a VEC2 while using the nitrous and when you dont, but you can safely tune the nitrous with various jets and run a little longer line to reduce the initial lean spike. Your bottle pressure is fine. I wouldnt start increasing it at all. I have tuned mine around 950 and I just try to keep the bottle pressure consistent.

So if you are using a 42 nitrous and 25 gas I would first go with the 46 nitrous and a little longer line and maybe consider a purge.


John

[kwkshift]

Thanks for the replies.

John, I do have a purge on the car.

Is the VEC2 pretty easy to install and tune with? Does Sean Roe provide good customer support with the opurchase of one?

Will that lean spike hurt a piston in the long run or is this something that everyone just deals with?

[plumcrazy]

vec2 is easy to install and not easy to learn if ya sk me. sean support is just the best though.

[J DAWG]

Greg

I ran the kit on my cast piston car and didnt have any problems with the pistons. It was pretty scary to see a lean spike at times that would hit 18 or 19:1 for roughly .3 seconds and then come back to an acceptable a/f.


That is when I stepped back and starting talking to other nitrous users with various makes. When you think that the nitrous is coming in at nearly 1000 psi and the fuel is coming in at 55 psi then it is almost unavoidable and I dont think other cars are anymore immune to this than ours.

A 150 shot is only an additional 15 hp per cylinder when you think about it. You have forged pistons with a 60% larger ring land than I do, so I personally dont see any issue with the momentary 16 or 17:1 spike as I am sure many others experience the same thing.

I am gonna scout around a few boards to see what others are saying again.


John

[J DAWG]

ps - and I believe both Jack and Phil are using the VEC2 for their fuel versus a solenoid. The VEC2 is relatively easy to install and many including Sean use it so you wouldnt have a problem getting tech support, but honestly you can tune your system with the nitrous and fuel jets. It just so happened I had the VEC2 before the nitrous system but when I ran my best time it actually wasnt being used.


John

[J DAWG]

Hmmmmmmmmmmm.....disregard what I said earlier.....as I look back at the graph I see your lean spike is coming in about 700 to 800 rpms after the nitrous hits. That doesnt make since.

The lean spike I am talking about occurs when the nitrous hits initially, not a couple of seconds later. That isnt a normal nitrous lean spike.

If you are not getting the lean condition when the nitrous first hits then you are good there.

Where was the a/f being read? Need to get a bung before the collector welded in and read it there. Do you know of anyone with an a/f gauge that you can use to log a/f or at least compare to the dyno's a/f?


To me this is not an issue with the kit but more the inherent way the car adds fuel and timing around the 3500 to 4000 range(our pcms suck). The VEC2 would definetly smooth that out, but before I did that I would want to get a good a/f reading just before the collector and go from there.


I wouldnt worry about changing line lengths at this time either. That will only help if the lean spike occured when the nitrous first hits.


John

[kwkshift]

John,

The A/F reading is taken at the tailpipe. From what I was told, that is the reason that the lean spike occured after the initial hit because it took a little bit of time for the A/F sendor to get it's reading due to the length of the exhaust pipe.

[J DAWG]

I would get your local muffler shop to weld you a bung in the exhaust right before the collector. Dont put it on the bottom since condensation will build up there. On the side works fine.

I would do this before anything else so you can get an accurate reading. Do you have cats? They can really alter a/f when spraying.