New, custom tune yields big improvements!

[Lowndex]

I have been struggling with low end performance problems after purchasing a Precision torque converter, SCT X3 flash tuner, ram air and custom map from Reinhart Automotive last December '07. My main trouble was low end stuttering at low to mid rpms.

Based on a referral, today I visited a wonderful automotive performance tuning shop near me called, Speed Freaks Industries (http://www.speedfreaksinc.net/) (SFI). I just returned from SFI where they performed multiple dyno runs to create a custom map for me. Most of the time was spent adjusting the prior torque converter settings RA supplied in their custom tune. In addition, SFI significantly improved my rear wheel horsepower.

Examine the attached two graphs and notice the significant difference between the SFI tune and RA's. I now have 284.1 rwhp @ 6000 rpm and 282.5 ft.lb. @4750 rpm. Measurements are taken at the rear wheel (real-world data).

If your Marauder has a similar setup to mine (see details in My Garage), I highly recommend to call Ravi at SFI (contact info on the graphs).

[2,4shofast]

Damn they came up with some pretty good numbers! Congrats...on the considerable change I bet the fun factor went up as well:burnout:

[Lowndex]

Because they are leaking on the ground everywhere I go now - burning rubber baby......:)

[sailsmen]

Mustang Dynos have a large number of operator selected variables.

[Lowndex]

Sailsman,
What do you mean, please?

[Lowndex]

Mustang Dynos have a large number of operator selected variables.

Please elaborate.

[Lowndex]

Dynojet
The Dynojet chassis dyno is referred to as an inertia-type dynamometer, because large drums provide an inertial load to the drivetrain instead of a friction brake. The working end of the Dynojet includes two 48-inch diameter drums that are mostly below the surface and driven by the vehicle's drive wheels. In the photos of the Dynojet, notice how the rear wheels are centered on the drums and there is one drum per wheel. This will become important later. The vehicle is typically run in the transmission gear closest to 1:1 (Forth gear for manuals and Third gear for automatics) to or a variable load that maintains a preset engine rpm or vehicle speed. This feature is ideal for forcing the vehicle to operate at certain loads for tuning. The Dynojet can also measure air/fuel ratio while testing.

Mustang
The Mustang chassis dyno uses an Inertia load as well as an eddycurrent brake load to simulate the "actual" load (combined aerodynamic plus rolling frictional load) that the vehicle would experience when in motion. Notice in the photos how the rear wheels sit between two smaller 10.7-inch diameter rollers. There has been some discussion about the tires getting "pinched" between the rollers and creating more rolling friction, but no substantial evidence of this could be found. However, Mustang has a dyno (MD-1750) with a single 50-inch diameter roller per wheel that alleviates the wheel-pinch concerns. The internals of the Mustang dyno are composed of an eddy current brake to provide a variable load and an inertial disc to provide a fixed load.

Mustang claims because its dyno loads the vehicle as it would be on the road, you can perform 0-60 mph, 0-100 mph, and quarter-mile measurements on its chassis dyno. Launch dynamics are simulated on the Mustang dyno, which includes weight transfer, acceleration, jerk (the derivative of acceleration - how fast the acceleration occurs) and some other variables. The Mustang dyno can also measure the air/fuel ratio while testing.

Correction Factors
Correction factors are used by both dynos to account for varying atmospheric conditions such as temperature, pressure, and humidity. The measured horsepower and torque are multiplied by the correction factor to obtain the corrected values. This is similar to the corrected times and speeds provided by some quarter mile tracks. Theoretically, you can dyno on a hot day in the high altitude of Denver and on some other cool day at sea level and produce the same corrected horsepower even though the observed horsepower you are producing at each location is different. Both dynos calculate a correction factor based on a Society of Automotive Engineering document (SAE-J1349).

When testing was performed on the Dynojet, the correction factor was 1.10, which means the observed numbers were multiplied by 1.10 (adding 10 percent) to get the corrected values. The correction factor for the day when testing was performed on the Mustang dyno was 0.9595 (removing 4.05 percent). The correction factor when road-testing at Keystone Raceway was 0.962, a correction reduction of 3.8 percent.

Why Is loading the Vehicle Important?
The answer to this Question is twofold. First, the engine produces horsepower at the flywheel (brake horsepower) that is reported by the automobile (http://g35driver.com/forums/showthread.php?t=26743#) manufacturers. Engine power is coupled to the rear wheels by a transmission and a rearend. But this is no free ride - there are losses in both the trans and the rearend. Therefore, the power to the rear wheels is equal to the flywheel horsepower minus the drivetrain power loss. The drivetrain losses are mainly composed of three loss areas: friction loss, inertia loss, and viscous loss. The friction loss is largely due to the surfaces of the gear teeth rubbing against each other. Gear friction is related to the torque being transmitted through the drivetrain. The gear power loss is related to the speed at which the torque is being transmitted.

Inertial loss is related to the rotational acceleration (i.e., angular acceleration) of the drivetrain components. The inertial loss does not result in a power loss (i.e., heat) but absorbs energy that can be coupled to the rear wheels. This energy actually gets stored in the drivetrain components. The stored inertial energy in the flywheel keeps the revs up while the clutch is pressed in during shifts. The inertia loss is more pronounced in lower gears (i.e., First or Second) when the acceleration is highest. The viscous loss is basically the pumping of lubrication fluid in the transmission and the rearend. This is one reason why you get better e.t's when the drivetrain is warm, because the oil is thinner and provides less "pumping loss."

Therefore, to measure the actual rear-wheel horsepower, the drivetrain must be properly loaded to obtain the correct drivetrain loss. If the dyno provides a lower drivetrain load, then the drivetrain losses will be lower and the resulting rear-wheel horsepower will be higher.

The second reason why vehicle loading is important is that the newer computer-controlled vehicles use engine load as a control parameter. For example, ignition timing is a function of engine load. You will see higher timing advance when revving the engine in Neutral than you will when the vehicle is fully loaded at wide-open throttle in Third gear. This engine loading factor (and airflow dynamics, which is beyond the scope of this article) can help explain why some people have dyno'd identical to a friend's engine on a Dynojet dyno but got different results on a Mustang dyno.

Conclusions
Realize that both the Dynojet and Mustang chassis dynamometers are useful tools that have excellent repeatability. Both dynos measure the correct horsepower and torque for the load that they apply. Both dynos will show losses or gains from modifications. It is recommended that you pick a dyno for your baseline testing and stick with that dyno type and dyno location (and dyno operator) for subsequent testing.

The bottom line:
dyno numbers are for show, and track times are for the dough!

-author unknown

[dohc324ci]

NICE numbers! I was thinking of having my MM dynoed there, what did that run you? Also, did you have a custom tune from DR then you had SFI modify that or did they replace it all together?

Are you located in tracy?

[Lowndex]

NICE numbers! I was thinking of having my MM dynoed there, what did that run you? Also, did you have a custom tune from DR then you had SFI modify that or did they replace it all together?
The SCT X3 holds 4 maps. I have stock, RA's and now SFI as my primary.

Are you located in tracy?
Yes. Ask for Ravi and tell him LOWNDEX sent you. Ravi's phone number is on the dyno graph or

Speed Freak Industries
http://www.speedfreaksinc.net/

[red]

...Dynojet vs. Mustang info...

How many times did you paste this thing? :rolleyes: As I mention here (http://www.mercurymarauder.net/forums/showthread.php?p=605366) and here (http://www.mercurymarauder.net/forums/showthread.php?p=605368):


Dynojet also offers a brake (eddy current/loading) dynamometer (http://www.dynojet.com/automotive_dyno/224xLC_dyno/default.aspx), like the Mustang. So, if the goal is to be accurate, then the type of chassis dynamometer (brake or inertia) should be specified, not the brand of dyno. Brake dynos will provide "real world" numbers, which will be lower than what is read on an inertia dyno. Though the inertia Dynojet has a fixed mass, the operator can apply several corrections. For example, they can set the dyno on SAE or UNCORRECTED (depending on environment) for a before tune run and then switch to STD for the after tune run, yielding higher numbers. Also, smoothing can be used to manipulate the output; jagged "curves" will show higher peak numbers. Generally, the operator can make a before tune run while the car's heat soaked (say after driving it to the shop) and an after tune run on a cool motor, giving higher numbers. Another variation is running the before in the middle of the afternoon and the after in the evening. Other tricks include increasing the load on the car for before runs (e.g., turning on accessories or tightening the straps) and further software adjustments.

[dohc324ci]

Thanks Lowndex!

What fuel are you running to get those numbers? I ask because I know there is a gas station here in Tracy where you can get 95/100 octane.




Yes. Ask for Ravi and tell him LOWNDEX sent you. Ravi's phone number is on the dyno graph or

Speed Freak Industries
http://www.speedfreaksinc.net/

[magindat]

This is typical when comapring a true dyno tune to a mail-order tune.

Every car is slightly different. Variables such as mileage and especially initial break-in mean every car is different. A mail order tune must account for the 'low end' as well as the 'high end' of the spectrum of variables and build a safety factor around it. Comapring these tunes is like comaring off the shelf clothes to a custom tailored suit.

Congrats on your improved numbers. A good dyno tune is always money well spent. Enjoy!

BTW, I think what sailsman means is that numbers can be manipulated. I don't think he's saying the are... just that they can be. For example, I used to compete in car stereo. Used to beat the pants off a shop team here locally when in sanctioned competition. Always lost at local shows. Their man operated the SA3055. One show we finally caught him with his finger on the mic gain.... it could happen. Take EVERYTHING with a grain, you know?

Anyways. Congrats again. Glad you found a shop you trust and HP you enjoy!