Wouldn't the 1/4 mile time slip depend on the driver and their ability?

No matter the reaction time, my skill/ability to get down the strip might differ from yours or any other forum member.

I would think a calibrated machine would tell a more accurate story.

Perhaps the same driver, using the same fuel, in the same lane, with the same weather conditions might be pretty accurate. As long as he doesn't eat a bad taco between runs.

If forum members are not interested in dyno numbers to make their decision, Then I'll save my time and money

I would assume that a 14% larger pulley is a 14% larger pulley (just math assuming weight is the same). The ECU tune would be the wild card.

 

That's why I said Before and After times slips. I was implying that they be from the same car with the same driver. I have found that these cars run VERY consistent at the track, so even an average driver should be able to consistently reproduce the same times...

I think there is MORE variation from one dyno to another. I've dynoed cars on three separate Dynos with the same mods and gotten three vary different readings. There is also a broad range of options for viewing dyno charts. Peak numbers are all over the place depending of if its SAE corrected, takes into account humidity, temperature, Altitude etc.. Then there is the smoothing curve. Smoothing 0 will show higher peak numbers, with no smoothing which is not very accurate. Smoothing 5 takes out all the peaks and valleys in the chart to show a "true" power curve. A lot of dyno racers will quote "raw" uncorrected and smoothing 0 charts to say they made more peak power than they accurately do.

Mustang Dynos, Dynojets, Dynapacks all read very different numbers with the same car hooked to them. Therefore, in my mind, unless I'm there to interpret the dyno chart in person, it doesn't mean that much because you don't know how it was read, set up or what type of dyno it is. A dyno is great for tuning a car for the track, but only the track gives you the full story...

To me, quoting dyno numbers is the same thing as quoting numbers out of a magazine... Verifiable time slips that show a progression of mods tell a much better storya dn show a much more accurate tale of what is really going on while testing ONE car.

 

The RENNtech kit is claims 45 BHP.

The ASP Pulley is the same size as the RENNtech pulley but minus 2 pulley's in the kit. The numbers of 20 hp increase is rwhp.

I believe that if the individual only received a 20 rwhp increase there is either an issue with his ECU programming or with his IC pump.

If you compared the HP generated by the RENNtech Pulleys & the ASP Pulleys the difference would be within the margin of error on the dyno.

 

They both use the stock belt so ASP must provide a smaller water pump pulley and thus they both will increase boost (SC RPM) at the same engine RPM's.

Hence the first question of this post.

After researching and calling, I believe that Powerchip and InMotion are the two best ECU upgrade options with the ASP Pulley. They both compensate for the increased boost. Although others may be just as good or better, they might not be around in years to come should I require a re-flash.

This prices the ASP Pulley/ECU upgrade at $1,300.

After reading the replies on this post, there really is no true way to baseline or compare ASP, Renntech and EVO. Some say dyno, some say 1/4 ET. I guess how you would measure and compare depends on if you looking for HP gains or shaving your ET.

I'm just looking for increased (noticeable) street performance at the best price I can get. I don't think I could ever tell the difference, if there is any, between the three pulley options. I don't go to the track but would like to know the HP increase over stock for my own curiosity.

I figure the money saved will pay for a SL55 Y-pipe and boost gauge, a new in-dash stereo/DVD player with built in Bluetooth (JVC KD-AVX33), front and rear cameras and molded CF center consoles (maybe medium burlwood). = About $2K

I guess it comes down to simple economics.

 

I can go along with that. I know its unlikely to see a before and after for both the ASP and Renntech setup. I just wish there was some legitimate way to tell the true difference between them. I'm sure the ASP is a good product as is the Renntech. I just wished ASP would give us some claim numbers to go by.

 

My co-worker is considering the Renntech. Maybe I can talk him into going to the track, and the local dyno PRIOR and AFTER getting it done...although it will be tough.

I, on the other hand, would likely end up with the ASP due to cost. I WOULD get a baseline before, and updated 'AFTER'.

My main concern is warranty...lord knows the computer logs all of the increased boost, not to mention the likely noticeable ECU upgrades.

SQ

 

I have read through this entire thread and have seen many opinions bantered about. If you are trying to determine increases a particular mod gives, you must have a baseline to compare. 1/4 mile times are not the baseline you want. There are too many variables to contend with temp, humidity, the ability of the driver to reproduce the same results is nearly impossible. There isn't a driver in the world than can register the same exact 1/4 mile time twice.

The answer to your question is the dyno. If you are concerned as to how accurate reproducing the same readings will be, then try this.

1) Use the same dyno each time.
2) Have the same tech work with you.
3) When positioning the car on the dyno ensure the same alignment as much as possible. To achieve this you can measure from the front or rear bumper to a fixed point in the shop on 2 corners
4) Record the temp and humidity the day you do the baseline run.
5) For subsequent tests, select days that are as close to the original temp and humidity as possible.
6) Do a minimum of 3 runs.
6) Allow for proper cooling between runs. Hot cars produce less hp. approximately 30 minutes is fine. If you want to get real technical bring a thermal imaging camera to read the surface temp of the engine. Select a temp that is equal to the temp the engine is after idling for 15 minutes. After each run wait until the engine temp drops back down to this temp.
7) Hp power should be measured in 3rd gear.

With a supercharger of the type in our vehicles, a flat torque and hp curve should be visualized. Unlike turbo chargers that increase thrust with the increase in rpm. The hp reading you will read is RWHP not brake hp. The difference is RWHP is the hp the car is putting to the ground. The brake hp(this is the one listed in the cars literature) is measure prior to the engine being installed in the car. Some refer to this as the hp at the flywheel. Hence it does not take into consideration the hp loss thought the drivetrain. The transmission, torque converter, and rear-end consume hp. Automatics lose between 18-22% of the hp from the fly wheel(brake hp number) to the ground(RWHP). So our cars list @ 330hp this roughly calculates to 264 rwhp using 20% loss through the drive train.

As for the debate over not needing to re-tune for the additional thrust when changing pulleys, that may be true if a very small increase in thrust is added. Remember more air equals requires more fuel. A crossfire does not use an MAF to measure air density/volume. It uses a fuel map. this fuel map is variable to a point but can not adjust for large changes. So if you increase the thrust and the ECU does not sense the increase, and increase the amount of fuel, your air/fuel ratio will drop and you will end up with detonation. The car will be running to lean. The AIT sensor reads only the air temp not CFM's or air density. You will need to increase fuel flow as air flow increases. This is what the tuning of the ECU does. Like I stated earlier you will get away with some additional thrust unaccounted for but at some point you will lower the air/fuel ratio low enough to create detonation.


I have rebuilt 7 cars. 4, 1/4 mile cars and 3 rally cars. Simply changing a pulley can give you additional hp but not monitoring fuel ratios can lead to a lot of engine damage. Have the ECU re-tuned for the pulley change as a soon as possible. The exhaust and other changes you make will less likely put the engine at risk. They make very small changes in most cases, surely not enough to damage the motor. The expected hp gain with a cat back exhaust is minimal, especially on a car that is already exhausting well like the srt6.

If you are interested in really big gains in hp install a NO2 kit with a 150 shot and hold on for dear life.

Leadfoot