Some nitrous notes

[the head]

Well I managed to best my old time on the 50hp jets. And tried some 100hp jets. I did things a little differently this time around. I was running 93 octane, about 5 gallons or so and also added a gallon of 104 octane unleaded. I did this to help with the 100hp jets not causing detonation or at least curb it. Consequently I only ran a 14.95 best on motor. But the 50 hp jets did indeed wake up a bit.

What was most interesting is the 100hp jets I put in. It ran just slightly leaner than the 50hp jets but was still reading 'rich' on my a/f gauge all the way through the runs. I didn't notice any pinging or anything like that. What I did feel was that the truck definitely pulled harder at the lower rpms but at the upper rpms near the shift points it felt no different than the 50hp jets. In fact, the ETs were about the same as the 50 hp jets but it was running about 1.5mph faster through the traps (best 14.01@98.3). I ran them about 5 times. The first two were progressive runs, meaning I hit it in second gear, let off for the gear change, and then hit it again. Second run was second gear and letting it shift into 3rd with the NOS going, and then the last 3 were all-out, hit it at 3500 rpm in first gear and let the truck shift through it. In no run did the tranny slip, the tires break loose, or anything else out of the ordinary.

If anyone remembers, I also got the same result with the 75hp jets I tried before but thought that it was too rich (fuel). Looking at those results and tonight, I think 50hp jets are about all my truck will take successfully. As far as why that is, I can think of a few things:
1) It is detonating but the computer (knock sensors) are pulling out the timing to keep it from damaging anything.
2) The stock fuel system is getting maxed out at the upper RPM range. Even though I have a gauge, let's face it - it ain't that accurate to tell me what's exactly going on.
3) The stock ignition can't burn everything well enough.
4) There is still some restriction in the exhaust that the spent gases simply cannot overcome to get out and make more power.
Insert your reasons here.

I've ordered some other jets that will be here soon and they include a 60hp jet setting so I'll try that next. I may also try a 40 hp set to see what happens as well. In any event, I may be at the point that I have to add a separate fuel system to deal with the nitrous. Not a big deal, just more $$.

Track conditions were pretty good - 59 degF with some humidity, but there was about a 10 mph cross/head wind that wasn't helping. I did install a bottle heater yesterday to deal with the lower temps.

And if you're wondering, yes - I was getting ready to unbolt my bumpers to get that 13.9 run in, but I'll save it and just settle for when I get my wheels in and different rubber for track use. Timeslip for best motor and 50hp shot for your viewing pleasure.

Until next time...

[phillipyang]

no words...

[SupraTitan]

Originally Posted by the head

1) It is detonating but the computer (knock sensors) are pulling out the timing to keep it from damaging anything.
2) The stock fuel system is getting maxed out at the upper RPM range. Even though I have a gauge, let's face it - it ain't that accurate to tell me what's exactly going on.
3) The stock ignition can't burn everything well enough.
4) There is still some restriction in the exhaust that the spent gases simply cannot overcome to get out and make more power.
Insert your reasons here.
:

What makes you think that your on the brink of Detonation. I'll be willing to bet you have a ways to go, espcially if your running 100+ octane.

Also I learned a sometime ago with tuning turbo cars that an A/F ratio guage off the stock O2 sensor is pretty much useless, if you ever get it to read lean under WOT its more than likely too late. But I think you already know this.

I also think your not giving the ignition enough credit, since the late 80's the japaneese multiple coil ignitions have been hard to improve upon. Usually the only issue's with such systems under high boost is to much of a plug gap, will show itself as a high rpm miss or flutter. Reduction in plug gap ussually cures the issue.

I agree about the exhaust, without a doubt the cats and factory manifolds are choking off alot of flow.

To give peace of mind on the fuel situation you should run it on a dyno with a wide band 02 sensor, also I don't see why an Apex'i SAFC(super air flow computer) wouldn't work on the titan, with this piggy back computer installed and sometime on the dyno with a wide band you can get your A/F ratio's just about perfect as long as the stock components can keep up with the required flow. Usaully the weak link in the stock fuel system is the fuel pump, I have no clue what the stock pump is rated at but you might want to look into a walbro 255LPH pump which will give the injectors everything they can handle. Just throwing out some idea's, I have no doubt that the bottom end of the VK56 can handle pretty much everything you throw at it as long as the fuel stays in check. If the bigger jets are not giving more power, my guess would be that the injectors are operating out of their duty cycle and going static and simply just dumping fuel into the engine. The only way to really verfify this is with a wide band 02. Are you blowing black smoke under
WOT? good luck and keep up the good work.

[the head]

I guess I should've put "maybe these are some reasons". Thanks for the feedback. I post the info so we can learn stuff and so that I can get sanity checks so it's appreciated.

The 104 was mixed in with the 93 octane so it was probably around 95 octane all together.

The a/f gauge takes about a second to register changes. Sometimes it is more immediate but yeah you can't compare it to the widebands.

On my vehicle I have the Banks and resonators replaced so any exhaust restrictions would have to be in the cats or the stock exhaust manifolds, I would think. I'm just speculating, though. But I doubt that is the reason.

Does Wlabro make a pump for a returnless fuel system like we have? I run a wet system so the duty cycle on the injectors is irrelevant to the amount of nitrous going in, unless it is so rich (fuel-wise) that it is cutting the injector cycle back. And then it would be losing power just from being too rich as a whole. No black smoke that I can see or other spectators there with me watching the run at various places on the strip.

I hear the Chevy guys are doing a dyno day soon so I'll probably hook up with them and see what gives.

[DV8]

I would think the loss of power would be computer related. Since you are running a wet shot, there should be no physical reason to lose power on the top end, since you have enough air velocity in the intake manifold to prevent pooling.

The ECU is probably pulling timing to save the tranny. GM has something similar called "torque management" that kicks in before every shift to reduce damage to the tranny.

Ever think about buying a cheap wideband O2 and sensor and having a new bung welded at the Y-pipe to keep an accurate eye on your a/f ratio? You could also borrow an OBD-II scanner to check KR and Timing during your run.

Nice times by the way. Where is the dyno day going to be held at?

[the head]

The cheapest wideband I can find is like $450. I'll keep playing with it before committing to that.
I forget where the Chevy guys go. I'm going to tag along with them next time they head out. It is on the west side of town, I think.

[Tim Sloper]

I've done alot of LS1/LS6 tuning... you need to get on a chassis dyno with a wide band O2 sensor. You also need a scantool to determine what is happening with the timing. It will be alot cheaper to pay for a few dyno runs than it will be to keep burning nitrous and fuel at the track where there are too many variables to draw any real conclusions.

Tim

[scr38]

I bought a OBD 2 cable and software to use with my laptop computer. It works well, and isn't very expensive ($122.00). You can connect it and have it scan all functions, then play back the file. You can read timing, intake temp., air flow, etc. You can get it here: www.obd-2.com

[DV8]

Originally Posted by the head

The cheapest wideband I can find is like $450. I'll keep playing with it before committing to that.
I forget where the Chevy guys go. I'm going to tag along with them next time they head out. It is on the west side of town, I think.

they are most likely going to MTI on dairy ashford and oxford drive. ask Jayson or the tech guy who dynos your car to hook up the scanner on your truck and see if it is pulling timing due to KR or another reason. the dyno will be the best way to get that puppy tuned. a wideband for $450 will be worth every penny when running a power adder.

good luck.

[the head]

Thanks for the advice guys. I'm thinking that the wideband will probably be the way to go since I want to try different jetting and I'm sure that will burn $$ on the dyno to find out. Eventually there will be some other parts that come out and that'll probably force some further jetting changes as well.

Due to my inexperience with the wideband, is there some way it will indicate detonation due to a wild reading or something? I'm thinking the OBD scanner will be necessary as well.

[DV8]

Originally Posted by the head

Due to my inexperience with the wideband, is there some way it will indicate detonation due to a wild reading or something? I'm thinking the OBD scanner will be necessary as well.

a wideband will only tell you the a/f ratio. if you want something that'll give you a detonation count, you'll need the OBD-II scanner to show you the knock count. since we don't really have a tuning program, you'll just have to look at the a/f ratio and knock and jet accordingly.