[mshred]

Was finally able to get out to the track last weekend and start to really try tuning the car on the nitrous. A little about the combo

3470lb Mopar A-body
4**ci small block, 10.25:1 compression, aluminum heads, old school solid roller, locked timing, 94 octane pump gas motor (same fuel pump and fuel feeding motor and nitrous)
904 three speed
Caltracs, monoleafs, D/A shocks, 275 pro tire with a 4.10 gear out back
Cheater plate kit

Made a couple of passes on the motor just to check for repeatability and see if N/A performance changed with getting the converter tightened (Tighter converter netted slower e/t's but also less mph...not sure if that is how it is supposed to work still since MPH I thought was to indicate HP?). Went 11.12-11.13 at 120mph.

Now for the nitrous passes. All passes were made with the bottle pressure at 950psi leaving the line, and off a transbrake. Jetting in the plate is .063N/.055F. Pulling all the timing out at the hit with a Mallory hyfire 6 box (Cannot ramp anything back in) and running NGK 9 plugs (8's on motor) with .025" gap in them...no other electronics

1st pass
12 degrees of timing pulled (From 34 to 22 total), 5.5 psi flowing fuel pressure
Launch at 3000rpm (although car left somewhat sluggish, I think I didn't have the pedal matted on the brake), shift at 6700rpm
60ft-1.57, 1/4 e/t- 10.58, 1/4 mph-126.72

2nd pass
I added 1/2lb of fuel pressure (6 psi flowing), everything else staying the same (actually had the pedal matted).
60ft- 1.59, 1/8 ET-6.82, 1/8 MPH-102.5, 1/4 ET-10.64, 1/4 MPH- 126.10

3rd Pass
Left everything the same, except I only pulled 10 degrees of timing (total of 24) in hopes that it might pick up some mph with the added fuel pressure as the timing mark looked low on the bend of the plug. Also tried some shock adjustments
60ft- 1.59, 1/8 ET-6.87, 1/8 MPH-101.06, 1/4 ET-10.77, 1/4 MPH-123.95

4th pass
Seeing that the car slowed down, I tried pulling a little more timing then what my first passes were like- 13 degrees pulled, for 21 degrees total, with the same 6psi flowing fuel pressure as the last pass. Again tried more shock adjustments (All passes were spinning BIG TIME...but this would be my last pass since afterwards a bad shock had me packing up).
60ft- 1.69, 1/8 ET-6.98, 1/8 MPH 102.05, 1/4 ET- 10.83, 1/4 MPH-125.36


After all of this I know I need to work on my suspension...Big time! Car is just spinning like crazy. Also, it seems like once I get above 6800rpm the car starts to break up. It is not fuel related as my fuel pressure gauge is rock solid all the way down the track at 6.5lbs. I am thinking it might be a valve spring issue, but not sure how much that is leaving on the table, and I am not going to make any full passes until that is sorted out.

As for the tune up. I was pulling the plugs (fresh ones) after every pass. I am no expert, and was basically just trying to read for detonation, the timing mark, and the base fuel ring. I tried the safest ways I could to make changes, but not sure I even went in the right direction at all. I found it a little strange that on such a small hit the car ran better with 12 degrees pulled then with 10 degrees pulled, even when I added fuel to try and be safer. I know it is pump gas, but 12 degrees on a 150 hit seems like a lot...do i need even less fuel jet in the plate or less fuel pressure? Looks like my first pass was my fastest.

Any insight as to what I may be missing here, things to try? This was my first time actually really getting a chance to spray the car more then 1 pass and make a couple of adjustments along the way to see what would change. I would eventually like to see a bottom 10/high 9 out of the car if possible with a little more jet.

 

[vegaman924]

6 degrees out for that shot is a lot,but 12 and id back up the fuel jet to 47andmake a 1/8 mile pass

 

[FATNFAST]

Yeah, I pull 8 degrees for a 93 jet. its a nitrous converter or it isnt. who cares what it does on motor. keep spraying til you loosin it up.

 

[us7race]

If it were mine U would go back to the 1st pass and see if it repeats. If it does I would take away 1/4 pound of fuel pressure and see what the MPH does. Doing an 1/8th mile pass first would be safer as well. It seems like you added fuel and took away timing causing it to make less and less power because it may be over fueled. JMO.

 

[mshred]

6 degrees out for that shot is a lot,but 12 and id back up the fuel jet to 47andmake a 1/8 mile pass

That much of a spread between fuel and nitrous is safe? Even on pump fuel?

Yeah, I pull 8 degrees for a 93 jet. its a nitrous converter or it isnt. who cares what it does on motor. keep spraying til you loosin it up.

Pump gas? I don't care so much about the motor performance, was just wondering about the mph drop...always knew mph as indication of hp, so even if the converter was tighter, I assumed it would ET slower but would mph the same.

If it were mine U would go back to the 1st pass and see if it repeats. If it does I would take away 1/4 pound of fuel pressure and see what the MPH does. Doing an 1/8th mile pass first would be safer as well. It seems like you added fuel and took away timing causing it to make less and less power because it may be over fueled. JMO.

Ok, so less fuel pressure to try next time with the 12 degrees pulled. I had actually added fuel, then added 2 degrees of timing and the car slowed, so I pulled back, but 1 degree more then before (from 12-13 pulled) and it was still slower. If it likes less fuel pressure, does that mean I should try another 1/4 pound back? At what point do you start changing fuel jets instead of adjusting fuel pressure?

I am just trying to be very conservative and cautious starting out since I am running pump gas for the motor and nitrous fuel side.

 

[vegaman924]

Put the jet in the fuel your motor wants not what others are doing, lots of other variables in the works carb jetting carb size cam etc.. I have 57- 40 in mine but that my motor, give YOUR motor what it wants

 

[mshred]

Put the jet in the fuel your motor wants not what others are doing, lots of other variables in the works carb jetting carb size cam etc.. I have 57- 40 in mine but that my motor, give YOUR motor what it wants

I know I need to tune for what MY motor wants...I am still trying to figure out though what exactly it wants lol. I thought I already had a pretty large spread between fuel and nitrous to begin with. Didn't even think of going more, especially with pump fuel.

 

[FATNFAST]

A/F meters are nice to have. I actually just use mine for quick reference. I have learned If you really want to give your car what it wants... LOOK AT THE PLUGS! You'll see Timing on the strap and Fuel on the porcelain! It will talk....Just Listen.

 

[mshred]

A/F meters are nice to have. I actually just use mine for quick reference. I have learned If you really want to give your car what it wants... LOOK AT THE PLUGS! You'll see Timing on the strap and Fuel on the porcelain! It will talk....Just Listen.

I have an A/F meter, but it was not working the weekend I was testing. I was looking at the plugs, after every pass actually! But I am no expert...I thought I was going the right way reading the strap, which is why I added timing. I thought that the base ring will determine jetting, porcelain to determine detonation?

 

[91RsNate]

Thats not that large of a spread.. take half pound of fuel out of it and make a hit I bet it cleans up and runs faster too

 

[FATNFAST]

look down inside the plug at the base of the porcelain, you should have a nice thin pencil line fuel ring down there. If it's a fat line....IT'S FAT. Yes, you do look at the upper part of the porcelin for speckles. look close, as some specks can actually be the porcelain boiling, but most of the time they look like little sparkles in the porcelain, and be too hot of a plug. The dark black speckles are detonation.

Read your plugs, But, I would bet you can't even see a timing mark on the strap of the plug pulling that much timing for that jet. Invest in an otoscope for examining your plugs. I always install new plugs, make a pass shutting the car off as I pass the stripe, coast up the return road, then either get towed back to the pits or pull a couple and replace them with old plugs and drive back.

I'll bet guys will be asking to see one of your plugs! If you post up plug pics, be SURE they are fresh after you shut the engine off right after a pass. Get one good shot of the strap and porcelain area, and one with the threads cut off exposing the base of the porcelain. You will be surprised at all the answers you will get then.

 

[67DartGT]

I run a much larger jet spread then that. I would take some jet out.

 

[BlackRS]

Call me crazy, but I would be wondering what a plug looks like after a motor pass to start with. :smt102

Second, I would be wondering exactly how much this cheater plate could put out for different jets on both sides nitrous and fuel? With what solenoids being used? Things of that nature.

 

[vegaman924]

its fat take out jet

 

[mshred]

Thats not that large of a spread.. take half pound of fuel out of it and make a hit I bet it cleans up and runs faster too

So from 5.5 to 5lbs flowing?

look down inside the plug at the base of the porcelain, you should have a nice thin pencil line fuel ring down there. If it's a fat line....IT'S FAT. Yes, you do look at the upper part of the porcelin for speckles. look close, as some specks can actually be the porcelain boiling, but most of the time they look like little sparkles in the porcelain, and be too hot of a plug. The dark black speckles are detonation.

Read your plugs, But, I would bet you can't even see a timing mark on the strap of the plug pulling that much timing for that jet. Invest in an otoscope for examining your plugs. I always install new plugs, make a pass shutting the car off as I pass the stripe, coast up the return road, then either get towed back to the pits or pull a couple and replace them with old plugs and drive back.

I'll bet guys will be asking to see one of your plugs! If you post up plug pics, be SURE they are fresh after you shut the engine off right after a pass. Get one good shot of the strap and porcelain area, and one with the threads cut off exposing the base of the porcelain. You will be surprised at all the answers you will get then.

Thanks for the tip on reading the porcelain down in the bottom! I do have a otoscope to look down there, but again, I don't know 100% what I am always looking at...it is a learning curve for sure, especially without wanting to blow shit up. I shut my car off after I pass the stripe, and then pull a few plugs at the bottom of the track usually. I do have the plugs, and they are clean (not idled on....Ill try to get some pics

Call me crazy, but I would be wondering what a plug looks like after a motor pass to start with. :smt102

Second, I would be wondering exactly how much this cheater plate could put out for different jets on both sides nitrous and fuel? With what solenoids being used? Things of that nature.

Umm, first off, motor passes I make on a NGK 8 plug...Not sure about your second question or what it means- its a cheater plate kit though, with the cheater nitrous and fuel solenoids as well.


Seems like consensus is I have too much jet...Any suggestions of where to start for how much jet I need on the fuel side???

 

[BigRicky3]

This isn't what your going to want to hear, but take the system off and spend the money on getting it flowed and blueprinted (IS, or otherwise). I've been sorting mine out for 2 years now, and the money I spent on filling nitrous, and T&T trips, and now a torched engine, I could have gotten mine flowed 3 times over.

Dad & I bought a flowed system from IS, and from the very first pass, the plugs were good, and we just played with timing to clean them up... I wish I had spent a little up front to get mine where his system is. Your not spending money on just getting a jet chart, the after sale tech help has been invaluable.


And, concentrate on fixing this, because a perfect engine tune up wont Band-Aid this, no matter how hard you try. Get the car to 330'... the rest will fall into place.

After all of this I know I need to work on my suspension...Big time! Car is just spinning like crazy....I am thinking it might be a valve spring issue, but not sure how much that is leaving on the table, and I am not going to make any full passes until that is sorted out.

 

[mshred]

This isn't what your going to want to hear, but take the system off and spend the money on getting it flowed and blueprinted (IS, or otherwise). I've been sorting mine out for 2 years now, and the money I spent on filling nitrous, and T&T trips, and now a torched engine, I could have gotten mine flowed 3 times over.

Dad & I bought a flowed system from IS, and from the very first pass, the plugs were good, and we just played with timing to clean them up... I wish I had spent a little up front to get mine where his system is. Your not spending money on just getting a jet chart, the after sale tech help has been invaluable.


And, concentrate on fixing this, because a perfect engine tune up wont Band-Aid this, no matter how hard you try. Get the car to 330'... the rest will fall into place.

I hear you man! I have seriously considered taking the plate off and sending it out to get flowed over the winter. I don't plan on doing much else to the car over the winter, so I should be able to fit it into the budget.

As for the chassis, trust me, I am not overlooking it...It pisses me off to no end lol...I didn't really get to tune much that day on suspension since a shock ended my day early. I am going to try and get the 275 radial pro to work, but I really don't want to have to use a progressive to do it...I would like to one day add more nitrous jet, and I have a feeling the radials, if not now, will require it then. I want to wack the bitch right off the hit, thinking maybe a bias ply might be in my future, but that might need a progressive too lol. I am just trying to keep things as simple as I can until I absolutely need to upgrade...Balling on a budget is tough, I am sure you know

 

[BlackRS]

Umm, first off, motor passes I make on a NGK 8 plug...Not sure about your second question or what it means- its a cheater plate kit though, with the cheater nitrous and fuel solenoids as well.

Pull those -8 plugs out after a motor pass and have a look. The motor tune needs to be nailed down before moving on to the nitrous. Maybe you have already done that? The second part, Big Ricky hit on it. Buying a system with good tune-ups to start with will advance you much faster in your nitrous experience. That might be an option for you? Good luck with it.

 

[James Ratliff]

I ran that same jet spread on my super powershot kit a couple weeks ago. I ran 5.5psi fuel pressure and dropped 8 degrees of timing. I left the fuel where it was as the plugs looked clean, but I did not cut them apart , just used a light and looked down in. I added a degree or two back on timing. I normally run 36 on motor and think I ended up around 31 on nitrous. It put the timing mark just out of the bend about a 1/4 of the way into the flat of the strap. I probably could have pulled a degree back out and set it on 30 but left it on 31. I did have race fuel and I run -8 plugs. For a 150 shot I think a -9 plug could be a little cold, couple that with the amount of timing you are taking out and the added fuel pressure, I would expect it to be really fat.

You can lean it out by either taking out fuel jet, and if i were to do that, I would set the fuel to 5.5 psi, you can take away fuel pressure as you have described but I would only go 1/4# at a time and read your plugs, or you can add some more nitrous jet which will increase your shot.

That is just my guess as I am learning same as you.

Good luck man.
James

 

[mshred]

Pull those -8 plugs out after a motor pass and have a look. The motor tune needs to be nailed down before moving on to the nitrous. Maybe you have already done that? The second part, Big Ricky hit on it. Buying a system with good tune-ups to start with will advance you much faster in your nitrous experience. That might be an option for you? Good luck with it.

Part of the reason why I am just getting around to spraying it now was because I was trying to nail down the motor tune. I was pulling the 8's after every motor pass, but on the motor my lack of plug reading skills doesn't worry me so much since as long as I am not detonating it, I can play with jetting and timing and see what the car likes/dislikes...that is not to say i didn't follow what the plugs were telling me (or what I thought they were).

I am seriously considering getting my system flowed...we shall see what happens this off season. Thanks!