well, let me preface these results by pointing out the before/after runs were in different weather conditions. The before runs were in around +700 DA ft and the after were in around +1300 DA ft. Not sure how much difference 600ft makes, but I'd imagine it's some. Ok, here are the specifics:

October 16th (+700 DA)
mods: S2 tb, magnaflow xpipe w/stock cats, k&n tie wrapped to open box

60ft... 1.78
330... 5.06
1/8.... 7.73
mph... 93.20
1000.. 10.02
1/4.... 11.94
mph... 116.92

November 8th (+1300 DA)
mods: exact same as above, except vararam in place of K&N

1st run:

60ft... 1.90 (i had a rough night getting out of the hole)
330... 5.21
1/8.... 7.88
mph... 94.88 (personal best by over 1.5mph)
1000.. 10.17
1/4..... 12.09
mph.... 117.12 (first time car ever over 117)

2nd run:

60ft... 1.84
330... 5.10
1/8.... 7.77
mph... 94.51 (car once again over 94)
1000.. 10.05
1/4.... 11.98 (2nd time for me in 11's)
mph.. 117.55 (personal best)

Well, all in all, I was pleased with the results. My short times were really off, but I still managed to go home with one of those elusive 11 second slips. I would have never thought, for me personally, I'd go 11's on such a poor 1.84 60ft.

Interesting enough, the 9 days leading up to my first track trip with the vararam after the install, my butt-o-meter was telling me 1st and 2nd gear felt greatly improved driving around town. This kind of goes against conventional wisdom of the vararam making a difference once at highway speeds and beyond. Well, as my track results indicate, this wasn't the case for me. My 1/8 mile traps improved far greater than the big end.

Oh well, nothing earth shattering, but I have hope better weather and some mid 1.7 60fts will get me around the 11.7 mark, maybe 95+ 1/8, 118+ 1/4. :cheers:

 

Another interesting data point. Ross had the same thing - he got a lot of improvement in the first 1/8 mile.

Your +600 feet DA could make almost no difference, or perhaps some - depending on several other factors. Back when Ross, Ric and I were banging heads, I came across an interesting article or two on DA.

You'd need temps and other info to truly compare.

Basically though, you went a little slower with the Vararam compared to the K&N tie wrapped to the stock box. Your mphs were higher though.

I guess if you are generous, and allow the vararam the benefit of the doubt and figure the higher mphs mean you should get better e.t.s eventually (which isn't a definite thing - if your short times were from spinning, that will increase your mph) then the vararam may have given you a modest improvement - for ~ $425.

I still don't understand why the vararam is showing gains in the bottom half of the track.

 

What kind of tires are you running? I would be very pleased with the 60' times if they are the stock F1s. Hell I would be very pleased regardless. Anyway, very nice runs!!! :cheers: :cheers:

 

Sorry, but this is not true.

Since we got lower DAs my car is now trapping at over 117 MPH while stock Z06 cars with good drivers are trapping in the 113 MPH range. I am also building over 25 MPH from the 1/8 to the 1/4, which is way more than a stock Z06 will do.

 

Good results, Blue.

I don't want to alter the thrust of the thread, but the cold-air intakes, including the Vararam, Halltech Tric, and Vortex, make more horsepower and torque than the stock air box. Period. The increased power produces benefit throughout the run after the 60'. And it helps even more comparatively in warm weather when their lower air inlet temperature results in less loss of timing than the stock air box or other aftermarket underhood air intakes.

My Tric had been sitting in the garage since I removed it trom my 01. I installed it on my 02 when I saw Steve Row (Vortex) and PowerShifter (Vararam) beating my stock times at 60'-330', 330'-660', 660-1000' and 1000'-1320' each by several hundredths of a second. The improvement is NOT just on the big end of the track.

After I installed the Tric, my times met or exceeded theirs in all those increments.

I am a believer in the improved air flow and have learned that you need to experiment with the air filter, if there are options. Some air filters produce more power than others. I finally settled on the PowerStack fliter from Halltec.

Ranger

 

Tom, I don't necessarily agree.

There's a sizeable difference between a 1.84 60ft and a 1.78. That .06 could easily have been .12 at the 1/4. And yes, I think the +600ft da diff would be a slight factor (or I wouldn't have posted it). It certainly didn't help.

I hope to get more results next weekend. Maybe the weather will be more comparable.

 

Either way......Great times. :yesnod: :smash:

:cheers:

 

Hmm, I was under the impression that you got a pretty big improvement in your 1/8 mile e.t.

This is from your initial post when you switched to the vararam. The first two runs were without the vararam, Run 3 was your best run with the vararam.

Did you not get about a 3 tenth and 3 mph improvement in the 1/8 mile?

-------------Run 1-----Run 2-------------------Run 3-----Improvement

60----------2.179-----2.099-------------------2.135-----0.004*

330---------5.675----5.605-------------------5.454-----0.186

660---------8.505----8.449-------------------8.181-----0.296
MPH--------87.48----87.54-------------------90.71-----3.200

1000------10.915----10.852----------------10.508-----0.376

1320------12.943----12.882----------------12.473-----0.439
MPH-------111.18----109.7------------------114.79-----4.350
http://forums.corvetteforum.com/zerothread?id=393349




[Modified by Tom Steele, 8:09 PM 11/14/2002]

 

Your original post on this a while back said that I got all my gains in the first 1/8th and very little gains the rest of the run. Run 3 (with the VR) was done on a day with higher temps and a higher DA.

I have been running the car in lower temps and lower DA and as expected the car is now building way more MPH at the big end. I have been trapping 91 MPH in the 1/8th and 117 MPH in the 1/4. That is a gain of 26 MPH at the big end and it more than my factory car did. It is also a bigger 1/8 MPH - 1/4 MPH pickup than any of the numerous stock Z06 cars at the past few challenge events.


[Modified by rbartick, 11:23 AM 11/15/2002]

 

Actually, that may or may not be the case. More than likely, a 600 foot difference in DA isn't going to make any appreciable difference. My guess would be about .06 if it were TRUE altitude.

But DA isn't a great tool for drag racing. HP correction factor is better.

Here's what I found on DA:

Weather Tech
Chapter 4: "HP Correction Factor"

The HP Correction Factor depends on the fuel system of the engine, that is, the type of fuel being burned and if the engine is naturally aspirated or not. The mechanical efficiency (i.e. friction) of the engine also comes into play for this calculation. The effect of very high water vapor content (above 1.0 in Hg vapor pressure) must also be addressed. PCs are absolutely required to properly handle all the math for the HP Correction Factor. The general discussion below applies to naturally aspirated gasoline burning engines.

These engines do not respond to changes in temperature as strongly as Density Altitude or Air Density Index would predict. Instead, engine power and torque vary with the inverse of the square root of absolute temperature. Racers have incorrectly reasoned that the "volumetric efficiency" (VE) of an engine was not affected by changing weather conditions, but in reality, VE increases significantly with increasing ambient air temperature. This increase in VE is a direct result of the increase in the speed of sound with increasing air temperature. Peak Mach numbers within the intake runners remain relatively constant for a given RPM. The speed of sound in air increases with the square root of absolute temperature as shown in the chart below.

HTTP::Response=HASH(0x8cc1a1c)


However, Density Altitude has been used for years with pretty good results. That's because the math used for the pressure and water vapor content components of Air Density Index are very close to those used for the HP Correction Factor. The largest error is in the way temperature is handled. And this error is generally modest since we only race over a relatively narrow temperature range, typically between 40 and 110 deg F. This range corresponds to absolute temperatures between 500 and 570 deg R. The chart below illustrates the difference between using a correction based on the inverse of absolute temperature vs the inverse of the square root of absolute temperature.

HTTP::Response=HASH(0x8cc1c08)


In summary, use the right tool for the right job. The HP Correction Factor is the right tool for correcting and predicting engine power and race car ET, and for determining throttle stop settings. To further illustrate the errors that can result from using the wrong tool, try the following example using the QUARTERjr.com Home Page Weather Station and Dragstrip Dyno programs.

Assume we just raced at Columbus where it was hot and humid - 400 ft on the altimeter, 85 deg F and 43% humidity. The Weather Station calculates 2690 ft Density Altitude and a 1.079 HP Correction Factor. The next race is a Friday night in Las Vegas, where it's cool and dry - 2100 ft altimeter, 60 deg F and 16% humidity. The calculated Density Altitude is again 2690 ft, but the HP Correction Factor is now 1.096. What do we do?

Tom's Note: IDENTICAL DA's, different HP

Since the Density Altitude is the same, the carb jet remains the same. But the engine will be making less HP in Las Vegas. The HP Correction Factor is designed to be used to correct the observed torque from the dyno to standard day conditions by multiplying by this factor. Thus, whenever the HP Correction Factor is larger, the observed (or actual) engine HP will be smaller. With less HP we will run slower (everything else being the same).

If you're throttle stop racing, be prepared to take out some timer. If you're running Pro Stock Truck, relax . . . your engine's not hurt, everybody will be running a little slower during this qualifying session than they did in Columbus. The Dragstrip Dyno program predicts that a 950 HP, 2300 lb Pro Stock Truck will run .04 seconds and 0.9 MPH slower under this scenario.

http://www.quarterjr.com/members/

[NOTE: There were two graphics in there, that the new forum software doesn't like anymore. You can check the link for more info on DA, Chapter 3 is also very good! Or you can read the whole thing at http://forums.corvetteforum.com/zero...=393349&page=7 ]





[Modified by Tom Steele, 8:08 PM 11/14/2002]

 

Tom, the 600ft additional DA did not help, that was the point.

The horried 1.84 60ft was the main culprit for screwing up a decent comparison of the before/after vararam ET. The car definitely made more power.

I'm going back this Sunday, and the weather should be comparable to the 700ft day according to the forecast. I think a good mid 1.7 60ft will get the car close to 11.7 :smash:


[Modified by BLU-BY-U, 3:30 AM 11/15/2002]


[Modified by BLU-BY-U, 3:31 AM 11/15/2002]

 

Blu,

Congrats on the new MPH numbers, and as someone who has been very up front about telling what works (for you) and what doesn't your input is appreciated. What tires are you running?

Les

 

Hey, thanks alot Les. I always try and post as many facts as possible about my runs, especially after a mod change.

The rear tires are BFG 17" 275/40 DR's on C5 "wagon" 17 X 8.5" front rims.

 

You are most welcome Blu.. I ask about the tires because our MPH is about the same (117-118 in my case) and even with my best 60' of 1.86 (stock tires) I can't break into the 11's. Ranger sent me his spread sheet analysis, and comparing my runs to his and Power Shifter it looks like I lose about a tenth in the 1st 60', two tenths by 660 (includes the 1-2 shift) and another tenth on the 2-3 shift. This is all wheel spin, so I either have to get a LOT better at spinning the tires less or go with ET Streets or BFG Drag Radials. I have given up on my quest for an 11 second slip with stock tires, it is time for me to throw in the towel on that one and set new goals :)

Again thanks for your results - it helps me in the thought process.

Les :cheers:

 

No way!!

:blueangel:

 

I'm sorry, I thought you said it was a slight factor. And it MAY have been. My point is that DA isn't a great tool for figuring out if your car is faster on a particular day. The HP correction factor is what we need to be using.

Two things:

First, with all due respect (and you deserve it with those times) but for most folks, a 1.84 is heaven on street tires.

Second, I didn't say the vararam didn't make more power. I pointed out that - like Ross - you picked up a LOT of your gains on the first 1/8 mile. I still find that intriguing.

Maybe it is cold air? After monitoring IAT's for a week or so, I can see where a heat soaked car has some pretty high IAT's compared to ambient temp. But I still don't understand why the vararam seems to do so much on the first half of the track.

Looking forward to hearing about your runs. Good luck!

 

Tom, I am sure Blu will point it out but if you look at a response to me he is running BFG Drag Radials on the car, not stock.

Ross - I may try ONCE more :)

Les

 

Les,

My mistake - I just glanced at his sig and didn't see them listed there. I didn't notice the reply to you.