Post Dyno sheets here.

[Sean Roe]

Hi Jack,

I guess if you can start the car and do the pull(s) before the PCM senses that one of the primary O2's is not sending out a signal within the preset range, it would be ok. If the car was run for even a few minutes (total) in closed loop, I would suspect the PCM could set a pending code and / or begin adjusting fuel on that one bank. I kind of saw it as a similar situation as what those with 2000 and newer PCM's encounter, rich mixture and code when one or both oxygen sensors don't heat up fast enough with headers. It would be interesting to test on a 2000 or newer model.

Otherwise, I don't see anybody disagreeing with the good sense it makes to dyno with air / fuel monitoring. The dynojet we use does not have one (not all do), so we use our FJO unit with RPM input and logging.

Best regards,
Sean

 

[J DAWG]

ROE s/c with 8lb pulley.

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[BlueGTS]

Sean, would you expect more HP from your 8psi kit than is shown on the previous graph? These numbers only look slightly better than the ones on your car at 5psi. It looks like a ~15rwhp increase. Is this normal? Is the torque increase what should be looked at going to the 8psi versus the 5psi?

 

[RSNAKE]

Take a look at the overall graph not just the peak numbers. It looks to me like there was an across the entire RPM range increase. At 4500 RPM there appears to be almost a 50 HP difference. I am surprised to see such similar numbers too, but it is still deceiving to look at only the peak numbers. It looks like the system is just running into some type of barrier at about 5,000 RPM. I think Sean Roe has posted about this elsewhere and is working on it. Just speculating here, but could be a number of things:

The supercharger may be too small to keep up, turning it that fast may be just heating up the air too much. The heated/expanded air will get worse with more boost and there is a point of diminishing returns. That is why intercoolers work well, because the partially counter act this problem. This is also one of the features of a screw type SC that Sean's system uses. It has nearly full boost at very low RPM, but does not have the ability to continue to supply as much as a centrifugal unit can in the high RPM range.

Could have a restriction somewhere else like at the supercharger inlet, the heads, or exhaust.

The fuel and timing mixture may still not be optimized for the additional boost

The computer in the car may not have figured out how to adapt properly yet.

All just speculation, but I bet that Sean will improve it.

 

[treynor]

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This is my DLM car with the "mild" setup @ 16 PSI. It's the highest recorded SC-only power output I've seen on a dyno.

 

[MaxedGTS]

Treynor, wow amazing numbers your car has only 8 to 1 compression???


Max

 

[J DAWG]

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LETHAL 750 #002 + Heffner SCi

 

[1TONY1]

Can you say torque ????????????????

utahviper's 1999 650R GTS ROE S/C

 

[J DAWG]

DLM Stage 1 on a creampuff

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[Tom Welch]

Did someone want to see torque?? No s/c, just Nitrous........check the a/f.....

 

[1TONY1]

Sorry Tom, That doesn't count. It was a TWO STAGE pull

 

[Gerald]

 

[Gerald]

Honest question here, I've noticed on several dyno charts (couple Roe charts and Heffner charts) that the lines are VERY jagged or smooth out with DIPS of 10-30HP between lets say only 100-200 RPM or so??(the DLM ones , 650R one and BTR ones look VERY smooth...) Is that something you feel when you accelerate as a bog,etc???? Or is it just a normal thing from dyno to dyno...?


Gerald

 

[Tom Welch]

Gerald,

The dyno operator can adjust the "smoothing" of dynometer graphing. A rougher graph can show higher horsepower and torque number because of the spikes from lower set smoothing of the graph. I have found that just about every Viper that I have tested (and we tested another one today) that with smoothing set at 5 (highest setting on the Dynojet 248)will produce a very smooth and accurate dyno graph curve that gives the most accurate reading.

To take this a step further, the operator can terminate the dyno pull with the remote in a fashion that creates a spike in the dyno graph at the end of the pull which can show a substantial gain in peak power. Look for this spike at the very end of the graph. A trained eye can see that power is peak when the graph curve becomes flat or starts a downward trend before the pull is terminated. These spikes can be removed from the pull, should the operator desire, and make the peak numbers read as they truly should.

There are some types of vehicles that will show a more "jagged" graph regardless of the sampling and smoothing settings, but Vipers do not fall into that catagory. There are many things that can be done to "enhance" the dyno performance of any vehicle. The important thing to realize is that consistancy in testing is the most important factor, especially when one is interested in performance results from given modifications or changes.

Tom

 

[GR8_ASP]

There are some types of vehicles that will show a more "jagged" graph regardless of the sampling and smoothing settings, but Vipers do not fall into that catagory.

Tom, I believe the SRT does fall into that category. I dynoed my SRT twice and did try all of the smoothing factors on a Dynojet system. The curves showed significant oscillations throughout. Also an acceleration or torque curve using a GTech Comp Pro shows the same oscillations. The oscillations are real.

 

[Torquemonster]

Thought - this may be a really dumb one - but - I wonder if the SRT10 has a knock sensor that is "over-sensitive"... it therefore makes minor corrections throughout the rpm range to control what it thinks (real or otherwise) is knock, then as it gets it under control, advance sipkes up again, power with it and the result is a seesaw graph line.

Scarier thought - the knock sensor is not over sensitive - it is just doing its job! I assume you use 93 octane Ron?

 

[Tom Welch]

My post about smoothing is related to more of a "jagged" type of graph curve. In viewing some of the sheets in this thread, it seems as there may have been actual stumbling or mis-firing or something of that nature that caused some of the prevelant waves in particular graphs. Without being there and hearing or knowing the actual vehicle, it is almost impossible to make a firm determination. In any event, those waves are not normal or should I say in the norm of Vipers with similar power output and different modifications.

Tom

 

[GR8_ASP]

Torque - don't believe there is a knock sensor. Yes I use 93. However, the oscillations are noticeable in every SRT dyno curve I have seen (about 10 different cars).

Tom - The oscillations are about 2-3 lb-ft. There are not noticeable seat of the pants or by ear. But they can be seen on both dyno and vehicle accelerometer. When I blow up the curves from either source they have the same characteristic shape. That is why I am convinced they are real and not measurement effects. What I can't tell is if it is a control characteristic, like the engine calibration, or a operating characteristic, like inlet air flow, driveline vibration, etc. I believe they occur under both open and closed loop operation. They are also pretty consistent in shape and timing during separate measurements.

 

[Sean Roe]

8 psi pulley on our Supercharger system. No aftercooler. Bolt ons listed below pulls, as well as temperature, pressure, wet or dry bulb figure and final correction factor. Two pulls done back to back to see the effects of heat on the power at 8psi. Smoothing factor of 3. Less "jagged" curve primarily due to new valve springs.

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[J DAWG]

Josoph Dell's DLM Stage II+ S/C at 11 pounds of boost.

 

[Dr Roof]

Impressive!

 

[FranciscoR.]

I didn't know a stage 2 could get those numbers...

 

[Joseph Dell]

Neither did I. And at 11lbs of boost!

I'm too afraid to turn it up to 14lbs... The car is scary enough as it is!

Doug builds one heck of a beast.

 

[treynor]

DC Performance stage I SRT/10. Mods: ported heads, DCX valve springs, upgraded lifters, K&N air filters. Otherwise bone stock down to the 4 OEM cats.

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[Sean Roe]

2002 Final edition.
Forged pistons, Roe Racing heads, Comp Cam, 1.7 Jesel rockers, 10 psi boost on Roe Supercharger, NOS universal EFI NOS kit from Summit ($549) using a single 0.065" jet. No intercooler. Owned by MBN. Exceeded Dynojet 224X limit of 1,000.

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[SlayTay]

My '93 Viper with '97 Cam, mildly ported heads, larger valves with Compcam Springs and Titanium retainers, T&D Roller Rockers, New roller lifters, Compcam push rods, Indexed and Clipped NGK spark plugs, MSD wires, Stock bottom end except for PolyDyn Teflon coated bearings, Borla headers, Roe 3" side exhaust, Hi Flow cats, Borla XR1 mufflers, Dual stage nitrous with Stage 1: Nitrous/Propane jets 51x2/42x2 and Stage 2: Nitrous/Gas 50x2/30x2 at 48psi independent fuel system, and VEC 1.

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Check out the dyno build up progress at http://www.cruisenights.com/redviper/redviper.html

And I am still patiently waiting for Sean's Gen I super charger.(hint! hint!)

 

[WESTCOAST JASON]

1970 Model Human. 6'2", 225lbs , worn out Vans shoes and dyno'd after a light lunch.

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[J DAWG]

2001 RT with Heffner heads and JPHen/Comp cam. STOCK HEADERS, 1.7 roller rockers.

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[99 R/T 10]

2001 RT with Heffner heads and JPHen/Comp cam. STOCK HEADERS, 1.7 roller rockers.



[image]http://vca2.viperclub.org/gallery/data/500/85f9c300cd-thumb.jpeg[/image]

No image JDAWG,
put the picture on the clubs media section then link it.

EDIT, here ya go.
[image] http://vca2.viperclub.org/gallery/data/500/85f9c300cd.jpeg [/image]

Crap, how come it won't come up? TONY!

 

[J DAWG]

Mike, I have been continually having so much trouble posting pics here for some reason. Sometimes it shows and sometimes it doesn't. I put it in my gallery, but when I try to right click nothing happens. I have hosted it at imagestation as well. Will try something else I guess.


ps - Took the car to the Steele, AL track a few weeks ago with 1TONY1. Ran pretty good. We'll have to hook up sometime soon.

John

pps - now I see the graph. what's going on???


ppps - does this work

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