DHRP

iTrader: (2)

My F completely stock ran the 1/4 mile at 12.8 @ almost 112 mph. A year later I added a Joe Z intake pipe and ISS DES Exhaust and ran a 12.6 @ 113 (March '12). Last week I headed back to the track and the car will not break into the 12's. I'm running 13.0-13.2 @ 109-110 mph. My 60' times are still the same ~2.0, Sport mode, Trac/VSC off, I'm paddle shifting at the beep. I lost 3 mph in the 1/8th and 3-4 mph in the 1/4. I thought it was bad fuel so I ran it down and got a 1/2 tank from Sunoco 93. I even reset the ECU. Headed back to the track a few days later and same results. Looking for some ideas on what could be the issue

Here are a couple of vids stock and after intake/exhaust.

Boma

iTrader: (4)

There are a lot of factors that go into these 1/4 mile runs. Weather, temperature, humidity, etc and even driver skill. No offense!

Seeing how you ran it earlier in the year it was bit cooler I'm assuming. If that's the case it may be a little warmer last week than your last run so that's something to keep in mind.

If you really want to find out if you're actually losing power, try running your car stock and again with the mods to have a better benchmark.

Evil Teo

iTrader: (13)

Ed did you take out the spare? are you on stock wheels? change the intake back to stock and see if any changes. what are your mods so far? also what boma mention plays a big factor.

DHRP

iTrader: (2)

Both March and September were both cool days in the 50's low 60's. I don't think it was enough to lose 4 tenths from stock. I understand the Joe Z gets very warm. Maybe I'll try going back to stock. I had about 30-45 min between runs. Spare is out of the car. I'm running Mickey Thompson Street ET's. I'll probably get it back on the dyno to see if there was any hp loss.

vbb

iTrader: (3)

If the conditions were basically the same, the track prep basically the same, and your driving ability/style basically the same, then yeah, you should not have lost 4 tenths over stock. I'd definitely take it to the dyno to see what might be different.

Boma

iTrader: (4)

That's a good idea.

Tire pressure is another thing to look at too, less pressure gives you better traction and vice versa.

caymandive

iTrader: (2)

Weather is most likely the culprit. With the same setup but in different weather conditions (density altitude) I've run anywhere between 11.9 and 12.5. Check the weather history for the days you were at the track and calculate the DA to see for yourself.

PS even on a dyno you won't be able to tell much as you'll also get varying results on a day to day basis. Obviosly if the results are way off then you may have something to go on.

Dv8tion388

iTrader: (2)

Weather matters more than just the degrees. Honestly with DR's you should be cutting at least 1.9 60' if not 1.8s.
Anyway. I would drive it for a couple weeks if you reset the ecu. I always got good results from using sport mode when I was actually hauling *** around, not stuck in traffic going nowhere. I dont know for certian what sort of learning the ecu does on/off of sport mode, but I do know I always posted good-great times everytime I went out.

~Dv8

ToothDoc

Check the BAROMETRIC PRESSURE. I've cut 2.0 and down to 1.8xx completely depending on the pressure. That's with MT and low weight. My best was 12.3 and recently did a 12.8 and the only difference was barometric pressure.

Everytime I go drag racing now, I check to see if the barometric pressure is 30.2 inches or higher. If it's like 29.8 inches I'm only going to hit 12.7-.8 I ran my 12.3@30.4

DHRP

iTrader: (2)

You guys are probably on to something. The DA in March when I ran was -822 and when I ran last week it was 553. Barometric Pressure was 30.24 vs. 30.10. Temp was 51 vs 65 degrees.

DV8 - I still can't figure out what RPM to launch this car. I've tried off idle upwards to 3000 RPM and can't get this thing to take off. I'm running tire pressure as low as 20 psi to 30 psi. I also took cayman's advice of burning out to the top of 2nd gear.

ISF001

Weather conditions make a noticeable difference in how my car runs. I doubt it is much more than that.

zazzn

Also, spark plugs and other things eat up a few hp as time goes on.

Dv8tion388

iTrader: (2)

Taking a page from Cayman, I would launch around 1500-2000, but time the last yellow so I get that momentum push off the line. In otherwords, im not holding the RPMs up on the brake the whole time. That can push through the brakes or bog. Idealy, if the track prep is good and the tires are sticky, then stabbing the accelrator should be all you really need to do since 1st gear is fairly torquy. I never ran my IS-F below 64 degrees, but I know if I had some 40 degree weather i probably would have ran a 11.9-12.0 N/A.

~Dv8

Joe Z

iTrader: (10)

FWIW.... I recently changed my battery on the IS-F.. The + & - terminals were unplugged for 3 days.

From time to time I like resetting my ECU, using the Fuse Pull procedure.
I have also done it by disconnecting the battery for a few minutes..

BUT this time I noticed a major difference in how the car responds and how it launches.. I feels like it did when I first bought it.. Plus the extra kick from the performance parts...

Try leaving the battery disconnected for a longer period.. or as long as you can...

Just my .02 cents

~ Joe Z

Just F Me

Though there are many differences in comparison from a top fuel nitro dragster and a street car, I follow the NHRA Drag Racing Series and those guys that run Top Fuel, Funny Car, etc, these guys are obviously extremely talented and very skilled and have pretty deep pockets, and those guys from time to time will run different times.

Track setup, weather conditions, engine maintenance (1 year later), we don't know how the condition or specs of the internals of your car. However, given all things the same, like someone mentioned, it could very well come down to track prep as well. I've seen at some NHRA events where the different lanes weren't prepped the same. Considering that, depending on which track you went to and the budget that's put in place for track setup, could be something that was skimpped on.