ok went to the track tonight

previous best with 2.77 gears and stock LCA location on eibach prokit lowering springs

13.89 at 96.6
8.80 at 77 1/8mile
1.895 60 foot

now with 3.27 gears, lower control arm relocation brackets on bottom hole. no other changes

14.17 at 91mph
9.003 at 75mph 1/8
1.92 60 foot

i couldnt beat that on my 3 runs before the rain hit. 91.4mph i believe was my best trap

traction seems to not be there for some reason. same tires, same PSI

but it was a hot day... 87-90 degrees with like a 95 degree index. track temps probly way up there

could that really affect my times that much?

 

When did you do those runs with the smaller gears? The summer kills your cars performance..

I wouldn't doubt that the heat stole you .2 or .3 in the 1/4. It's alot harder to get those 3.27's to hook.

 

Atmospheric conditions will have a big effect on the times you run. It's also posible that you will have more traction problems. So maybe you are slipping more comming out of the hole. Get some sticky tires.

 

Granted I'm currently jetted for consistency so I'm slower naturally, but 3 or 4 weeks ago the air was fair for summer weather (dont have log book here) but was dialed in at 11.25-.26 at 118-119mph

2 weeks ago weather was terrible and with nothing changed on the car I was dialed in at 11.48-.49 and mph was down to 117, yes the track temp was very high due to 100% sunlight and 106* temps aka "greasy track", I still dead hooked, but 60's were slower than normal due to lack of good air.

Last Saturday night we had 82* temps, 76% humidity, 29.16 BP and DA of 3300' running 11.25-.26 again at 119mph....

Weather has a HUGE effect on car performance. Whenever your doing basline testing, you MUST note current weather conditions, then later after you've done this or that to the car you can note the weather at that time- better/worse and guage weather the mods netted anything or not when looking at the BIG picture.

Same with going to the dragstrip for ANYTHING, I've said it too many times, you NEED to have some sort of sticky tires so traction will be at 100% every pass, otherwise trying to learn anything is just a waste of your time and fuel since you WILL NOT hook the same all the time. trying to stick higher numeric gears in with the same daily driven tires is just asking for traction problems, you can read it over and over and over and over again in this drag racing forum.

Cars are just like anything else, you need solid reliable concrete info to base opinions and gains/losses of modifications. Those results are not possible when your not making attempts to make every pass the same, just wasting time, gas, and rubber!!!

 

I was racing my truck last weekend. The Saturday night, the density altitude was about 5200 feet and I managed a best of 15.0x. Sunday morning it was cool and damp. I really wanted to get one or two T&T passes before the rain came but it didn't happen. The density altitude had dropped to 3500 feet and I should have been able to get a 14.8x pass if the track wasn't too cold preventing me from hooking up.

In 24 hours the conditions changed enough that I could have knocked a 1/4 second off my time without doing anything to the vehicle. Theoretically if I went to sea level, the truck would run 14.6x on the 1/4 mile. I've also raced the truck at close to 7000 feet density altitude was was happy to get a 15.7 out of it.

You're down 7 mph so the engine wasn't making as much hp on the second run. That will relate to slower 60' and 1/4 mile times. The weather conditions are probably the main reason for the loss of hp.

Move your LCA so it's level to the ground. Don't assume moving it down to the bottom will work better. Chassis adjustment is a tuning aid. What works good on one car may not work on another.

Give me a complete timeslip breakdown of each run.

 

well heres my situation.

the best run took place in may. but the slip didnt print a temperature but i was sure it was in the lower 70's and it was a nice clear day. that was with 2.77 gears and i ran a 13.89 at 96.6 mph with a 1.89 60 foot. on this run i ran a 8.80 at 77mph in the 1/8. another run with a 1.94 60 foot gave me a 14.02 at 95.5mph i think


today was HOT and i figured i would be hurting abit, but NOT this bad. i have since had the lower control arms brackets welded on and the tranny guy placed the lca in the lowest hole. it seemed to work ok on the street. Tonight i had no problem hooking.

first run.
1.929 60 foot. this was with a 2000rpm brake stall, drop brake and lay into it, not stomp. it hooked well and i let her go thru the gears. first shiftd at 5grand. tranny shifts 2nd at 4900 rpms

330 foot... 5.762
9.003 1/8 mile at 75.4mph
1000foot... 11.794
14.19 at 91.13 mph in the end

second run,
again, tryed to brake stall to 2500 rpm like i did on my career best but my pads are worn and the brakes wont hold the car so i only got 2000rpms again.

1.971 60 foot
5.773 330'
9.003 1/8mile at 75.77mph
11.783 1000 foot
14.17 at 91.44 mph

third run
tryed to brake it to 2500rpms, but the car crept into deep stage so i just mashed off idle
spun all the way thru first

2.28 60 foot
6.234 330'
9.509 at 74.85mph 1/8
12.318 1000footer
14.727 at 90.7mph in the end


i believe my problem lies in the fact that my car cant brake up to my normal launch point, 2500rpms. the tires hook well enough for me to get into the high 13's, but i lost alot of power to the heat. i guess it affects TPI alot more than i thought it would. the car runs hot tho too in the heat, engine temps reached 220-230ish every time i staged.

and i know sticky tires will help a ton, but i wont run them right now. i need it to be a street car with street tires that grip well for handling too. and i dont have enough money to buy a set of cheap rims and slicks jsut for the track, i dont track often. LOL

thursday its gonna be cooler around 70 instead of like 92 today, so i will go out if i can. i will also change out lower control arm location to level. it seemed to do best there before so i will try it again.

 

A better breakdown of the runs gives more information. If your local track only gives 60', 1/8 mile and 1/4 mile, it's harder to find out where on the track you gain or lose time.

Breaking down the run from available information

First run
60' - 1.929
time between 60' and 1/8 mile - 7.074
time between 1/8 and 1/4 mile - 5.187

Second run
60' - 1.971 (a bit slower)
60' to 1/8 - 7.032 (faster than last run)
1/8 to 1/4 - 5.167 (faster than last)

Third run
throw out the window. It's not good because of all the wheel spin.

So your second run was only slightly quicker in et but if you break the run down you can see that you actually gained .062 between the 60' and the 1/4 mile but gave up the gain by losing .042 in the first 60 feet due to wheel spin. Good sticky tires can make the 60' times more consistant.

 

oh i will edit the above post to post the whole slip info.

 

Nother thing that slipped my brain last night, the addition of the steeper gears WILL affect convertor performance/attitude since you have mechanically increased gear reduction, thus making it easier to over power your tires "power braking"

 

I wouldn't worry about .2 in the 1/4. Seems like it was a combination of 3 things slowing you down. Heat, Traction, Inexperience (obviously you race, but new gears take a week or two to get used to)

I think if you were to run it now, with the same conditions you ran in may, you would be a ton faster than a 13.89.

 

Losing 6 MPH in the quarter is major; more than can just be explained by weather IMO. I've seen up to 3 MPH difference between passes in good November conditions and hot and humid summer weather. So a 98 MPH pass was down to 95-96 MPH. Same track? If it were me I'd start hunting for a hardware problem.

 

yeah i do need to get used to this new combo. on the street, i realize today i can only power brake to about 2300rpms now before the wheels brake loose. so i guess i am gonna have to go from there. but i do need new brake pads so maybe it will hold stronger


on one of my runs in may, before my best, i ran a 2.02 60 foot, and ran a 14.2 at 92mph. next run was 13.89 at 96.6mph with a 1.89 60 foot

my car seems very dependent on how you launch it. makes all the difference

but it seems to run fine lately. no mechanical problems so maybe its just the weather?

 

Those engine and air temps are the reasons why. 230* is pretty damn hot for any SBC. I wouldn't be worried! Grab yourself a set of Hoosiers and take it to the track. Like IHI said, its much easier to diagnose and tune with sticky tires.

good luck man

 

Oops, missed the part about engine temps over 220 degs. You saw a 4 MPH difference on consecutive passes? Wow, that's over a 30 HP difference. Most I've seen is a 1.4 MPH difference over a span of 6 passes in the space of 3 hours.

The most likely explanation for the previous 4 MPH difference you saw and the low MPH on your latest passes (in addition to the weather) is that the knock sensor removed major timing. This will be more of a problem if the tune is based on lower than stock temp thermostat. Definitely work on the cooling issue via the Fan On temp settings in the PROM and/or manual fan switches. Datalogging your passes is extremely helpful in understanding the conditions present during a given run. Cooling the plenum with dry ice or plain old ice really does help on our cars. I do it even in cool weather. A less aggressive timing curve in the PROM may cost a few HP but increases pass-to-pass consistency because the knock sensor isn't pulling timing at inopportune times. Good luck finding the "lost" MPH.

 

thanks for all your help guys. the car does run pretty consistant, between 95-96.6mph most times. i think its all in the launch.

i definately have to look into fan switches. the thermo is a stock 195degree unit, so i gotta get the motor cold.

but even on my best pass, the motor was around 200 or so.

 

well it is very cool today and i want to go back out to the strip tonight and see what she will do. but i dont know if i will.

i raised my LCA's one hole to make them level and traction seems to be just a tad bit less than before on the street but handles nice so thats not a problem. it still spins like before so i cant really tell if it made much of a difference. but we'll see, maybe tonight

 

For radial tired car depending on your set up it's gonna be a playing game. Some cars take to having LCA in bottom hole so it puts more force into the tires, others want it in the stock/level location so the chasis takes the hit.

 

Get some Drag Radials and race in good conditions and you'll hit mid 13's easy, maybe low13's if you get a stellar 60'

 

^ ugh, i thought so but apparently not, check my other thread