This year, I made an agreement with myself to chase points at our local track with the understanding that IF I did well enough, I would look into getting a real racecar and leave the Duster for tearing up the city streets..

Well, the last two raceing weekend I've encountered something I just cant figure out and am turning to you guys for wisdom and guidance..

The car drops a tenth for no explainable reason..

First, I'm hitting the tree with decent numbers, R/T times avg .02x and this is with foot braking. The 60' times are usually 1.62 or 1.63 and given the adjustments for weather, wind and DA, the car normally is predictable..

I look at the playback tach after each run, the launch and shift RPM's are all within reason yet when its time to advance to the next round, the car doesnt want to do it..

In April, the runs were as follows:
TT1 11.494
TT2 11.506
ER1 11.493 (11.48 dial-in)
ER2 11.580 (11.49 dial-in)

Yesterday
TT1 11.448
TT2 11.452
TT3 11.464 (headwind picked up)
ER1 11.560 (11.46 dial-in)

EDIT.. After reviewing the incrementals, the car is dropping off after the 330' mark..

Spending all the time, money and energy only to see my name slip further down in the points chase is getting frustrating and probably the worst thing about it is... I'm totally clueless whats going on..

Soooooooooo.. do any of you all have any words of wisdom or advice.. maybe even a pep talk to hang in there?

Are you going into the next round running the same temps? Do you have a gauge to read trans temp? I'm omly guessing here but it sounds like it is tied with temp changes or fuel delivery.

Do you have a fuel pressure gauge you can see while going down the track? Is the mph falling off with the e.t.? If so how much?

I have the same thing happening with my car right now and its killing me in points too.

My car seems to work good when its cool out and when the heat and humidity go up it will loose .05 or more from one round to the next.

Been blaming it on being too rich so after it did it to me first round I took out 5 in jet and it did it to me again yesterday first round.

I guess if it keeps up we will just have to bag a tenth and at least have a chance at the finish line......



Very frustrating...

Also wanted to add that I had something similar to this happen along time ago and I had a 8 3/4 rear end that was eating itself up and it would be OK the first 2 or 3 passes and then start slowing down as it got heat in it through eliminations.

Just something to check and eliminate as a potential problem.

Don, are you keeping track of the weather? If so post the numbers on temps, humidity, baro. press and so on I have a freind who was having similar problems, his car would slow down .1 (1/10) to .25 ET (in the 1/8 mile) in the afternoon after our lunch break and drivers meeting. He lean the carb down 1 jet size(Holley type carb with aftermarket parts) and the car would drop .1, he leaned it down one more jet size on all four corners and the car would not drop much more then .03 Cool, thick engine oil, trans fluid, rear end grease and water temps can and do affect the way the motor and car runs

I'm trying to keep all the variables as constant as possible... ie: water temp, oil temp, trans temp, fuel and so on.. Obviously, depending on the length of time in the staging lanes, the temps will vary slightly.. But I dont think I experienced anything out of the ordinary to explain the full 10th of a second loss..

Cab, I did log the temp, humidity, DA, wind and etc and there was not a 10th of a second different from the 3rd to the 4th run..

Since I am a beginner and since I have a ton of learning still to do.. How common is it for other racers to drop a 10th without any explainable reason and what do you all do to compensate when this occasionally happens? I feel very confident the last two losses is directly related to car not running consistently..

Two things Don..One is the weather, which does change a lot around here from about 11-2 on race day. Part of that being the wind, which is ALWAYS an issue at Infineon, usually a head wind and it WILL affect your ET. How much only time and laps will tell. Secondly would be you being consistent with that you do in regards to temp control with the car. Making sure the car is at the same coolant temp, and oil temps on each of the runs, this gets harder in later rounds but you need to know how it affects the car. All this is even harder with a dual purpose car, but knowing what will happen as the car gets warmer is the key. Cars will pick up or loose ET depending on how warm/cold fluids in the car are. Also the tune up will be affected by this.

Oh yeah I know where you can get a great car..Works well, always consistent

Al, you and I talked about this in depth Sunday and yesterday and I took in everything you said.. So that's why I am focusing on the car and not the weather.. The track conditions did not change that much from run 3 and run 4..

The water and oil temp was the same for the 4th run as they were earlier in the day and not having a trans temp gauge, thats the only thing that could have changed.. but, I was first in the staging lanes and went thru the same routine to warm up the tranny as I approached the waterbox.. So if the trans temp was up or down.. I dont think it was by very much..

Because of your opinion.. I've opted for a tight dial vs bagging and keeping a little wiggle room, but I gotta tell you. I've had more success playing the fender game at the end.. lol So I wanted to know how do I compensate for when the car just isnt up to the task..

Well like I say you have to be able to drive the stripe. However leaving a tenth is a ton. You know I hold a bit but not that much.

IMO you need to get a better handle the tune up for sure. Probably two different set ups will work better, one for driving it around and one for the track. At any rate trying to have both with the same car is ALWAYS a compromise. It is hard to keep a car happy on the street and still consistent on the track. Just my opinion and what I have experienced over the years.

I know where there's a nice Demon - ready to race - hehehehe

Quote:

---

How common is it for other racers to drop a 10th without any explainable reason and what do you all do to compensate when this occasionally happens?

---

Not very common to drop that much in a few passes for anything I have ever raced aside of maybe a stock street car.

And you know the only thing you can do to compensate is have a tenth in the bag, or a big shot of NOS on it so when you know you slow you can make it up.

The other thing is lose, just like I have the 4 times it has happen to me.

Mine is lazy from the hit of the throttle. It even make,s my RT worse.

Yesterday .018 RT 9.77et 1st time run
.002 RT 9.77et second time run

First round DA is up a few hundered feet I dial 9.79 and only manage a 9.849 flat out and RT falls to .059

I am blaming mine on fuel and carb issues right now untill I find out otherwise.

Don,
I've always followed my Dad's recipe for consistancy.It seems to work very well as LilDemon can attest and verify.
My Dad has always run his cars on the very rich side.His theory has always been a lean car will show bigger variations that a rich car. He also dialed back the timing. Of course this meant he wasn't squeezing every last HP out of the combo.But it insured he would be consistant and the car would run cooler. He must have been on to something... He won over 400 rounds of bracket racing and was a 3 time Goodguys Hot Rod Champion.All in the span of 5 years running a limited schedule from the cool of winter to the heat of summer his dial did not vary more than .15
I applied the same theory to my Dart....went lots of rounds. But the best example was witnessed by Bill (LilDemon),My car was stored in my trailer for a whole year...March Meet to March Meet. I rolled it out with a 10.77 on the window,aired up the tires,threw in fresh fuel. Then went out and went 10.771 on the first pass.
We also clean our air bleeds with WD-40 after every 3 passes....you would be suprised how semi-clogged air bleeds can affect performance.

It just takes time to dial in your package.....make minor tweaks to your program or tune up.

Looks like the 4th pass of the day is when it really slows down. Could be heat related.

Something is off, my car varies a bunch throughout the day if I drive it to the track, but over hundreds of passes I've learned to get a handle on what its gonna do and I can dial accordingly.

Does the car always lose the ET on your 4th run? Or is it random?

Don,I think you are on the right path. Dont sell yourself short. Your reaction times are getting consistent and that for many is a big hurdle. Once you can get and maintain that consistency you can do things mechanically to change those results.

I also think the logbook is going to show you things that you may not be seeing just looking at slips. Once you right it down, put it on the pages and start to digest the info you will undoubtedly find a pattern. I think you will be surprised what you find. Try to write down as much info as possible in there, I have found when bracket racing information is King, you can never have to much. I thank Moprbilly for that tidbit of knowledge.

As we discussed this past weekend a fat race car tends to be a happy and consistent racecar. Not always true but I think with a car like yours it will be the trend. I think especially in street cars or dual purpose rides it tends to work best. I think the results are showing that. Things to think about that you will not see with the instruments you have. Trans temp, and that can make a WORLD of difference in ET's. Things like oil temp are also something that affect consistency. One other thing to consider are the temp of the intake, and if you have a mechanical fuel pump maybe you are having issues once you put some run time on it. One last thing I cannot stress enough is weather data. Weather plays a huge role is consistency. Certain combinations dont like certain things. For example my car does not like a lot of humidity, if the humidity goes up my car will loose more ET than with any other single weather change.

To ehlp get a handle on it go here and check the weather against the slips you have.

http://www.dragtimes.com/da-density-alti...rect+ET+and+MPH

Collect that info and then write it down in your logbook and start crunching numbers. I think you are going to find a common denominator once you look hard enough. This is not rocket science, but sometimes it can seem like it is.

Thanks to everyone that contributed in this thread.. You all gave me a lot to think about and things to keep an eye open for.. and for that information, I cant thank you enough.. But in this case, something else is going on with the car..

The last time the car ran consistent, which was 3 days of racing in March of this year at MATs in Vegas, the wind, temp and DA was all over the place and yet every single pass, a total of eight for the weekend, everyone was in the 11.7x range..

I get the car back home, pull off a couple of consistent runs back to back and then boom, the car loses a 10th which puts me on the trailer.. The first time it happened in Apr, I shrugged my shoulders and said that was wierd.. but now that its happened for the second time, I know there is something wrong with the car, but cant seem to get a handle on where to look..

Do you run and air filter? I've seen more than one engine slow slightly because of dust sticking to the entry of the air bleeds. Especially if your tune is that dead on (ie Stock Eliminator/brackets). I used to hit the carb with carb clean down the air bleeds as a first step to diagnosing. Also pay attention to fuel level in the tank.

Hi Davey.. I was wondering if you were gonna chime in.. glad you did!!

After the race in Apr, the thought of low fuel did come up.. so this last weekend, I made sure there was at least a 1/4 tank for all runs..

Regarding the air bleeds.. I need to change the bleeds to improve the idle and thats on my list to do, but I do not normally clean the bleeds.. That is something we will be doing on a regular basis from now on..