Tuning help

[bigz]

I need some help with my car. The last time I was at the track I was running about 23 lbs of boost and had a best ET of 13.2 at 107 mph. In four runs my lowest MPH was 104 best was 107. I'm running alcohol injection with a TA49, Blue tops, etc. I went to the track today and could only manage a best MPH of 100. Our track is at 5800 feet so altitude has a definite impact. The big disappointment is that I recently replaced the stock valve springs to CC 980's which I was hoping would improve my mph. I also just had the transmission rebuilt. The other variable is I was running 245/50/16 street tires. The last time I was running 275/50/15 BFG DR's. I did make two runs on 275/50/15 Nittos but that didn't effect the MPH (thanks again for letting me use your tires Lance!). The things that haven't changed from my last outing are the chip RA 108 or scan tool numbers. My O2's are fat on the bottom end and are in the 820's at the top of third. My MAF numbers are in the 230-240 range which was also the same last time TPS was at 4.7. I didn't experience any knock and my boost is the same as it was before. The shift points on the car after the tranny rebuild were 4900 at the top of third and I want through the traps at 4650. I'm stumped and don't know how I lost 4-5 miles per hour? My 60 foot times were a little better on the BFG DR's but still suck. Today I could only manage a best of 2.2 and before I was averaging 2.0's but that shouldn't affect MPH should it? Sorry for making this so long, but it was extremely frustrating and if anybody has any suggestions I would appreciate hearing them.

 

[qwknuf6]

Traction does effect my MPH , if you car is a low rpm torque machine ,like most stock or near stock setups , its the low rpm torque that moves you and without good traction you MPH may suffer , The altitude will slow you down also ,compounded with the rich condition(thin air ) you lose more power (mph).
So get some traction , lean it out and get back to normal altitude and you should be ok .
BTW I dont think valve springs help much on a low rpm engine (4650)

 

[Quick6'n'-K.C.]

give us a run down of the time slips--

100mph just plain ole sucks especially with a REDS 108 CHIP!!

what was the 1/8th mph?

usually these cars will pick up 21-26 mph between the 1/8th to 1/4-

if your car is only getting 80 in the eighth, then something is seriously wrong-


*********************I also just had the transmission rebuilt.


is it slipping really bad?? who rebuilt it? did you get a new convertor or did you get it rebuilt?
were you still running 23 psi and only got 100 mph?

 

[azgn]

what was the weather on both runs.....warmer air at that altitude can affect things a lot?

what was your rpm thru the traps prior to the tranny rebuild?

look carefully for a slipping trans......

are you locking the converter?

(btw, a faster 60' time will generally result in a slower mph!)

 

[bigz]

I've never manually locked the converter. The chip locked it at about 80 mph. My 1/8th mile time was about 80 mph. I can't find my old time slips to see what it was when I had the better mph on the previous runs. My converter was bought about a year ago so they did not do anything to it when the tranny was rebuilt. The weather was decent in the morning about 75 degrees and got hotter as the afternoon progressed. I don't think the tranny is slipping the shifts felt pretty solid. Quick 6 I agree the mph does suck, I was fairly happy with the 107 prior to this and thought with the valve springs I might pick up 1 or 2 additional mph so I'm definitely concerned about this. About the only thing I can think of is adjusting the TV cable to see if I can raise the shift points. My 1-2 shift used to be at 5200 and now it's at 4900 so I'm not sure what I'm going to do. The tranny was rebuilt by a local guy who was recommended by Bruce. Thanks and keep your thoughts coming.

Mike

 

[Quick6'n'-K.C.]

what is the time frame between the 100 mph and the 107 mph trap speeds??
1 YEAR????

my guess is the car is out of tune, and needs 02 sensor, wires, plugs, fuel filter, and check to make sure it does have the 108 race chip

 

[bigz]

All of the things you suggested have been done within the last year. I don't drive the car that much maybe 3-4 thousand miles a year. One thing I forgot to mention and I'm thinking this might at least be part of the problem is the way I was launching. When I ran it before my 60 foot times on the drag radials sucked to say the least, but I was leaving with about 5 lbs of boost even though the tires were spinning. Today I tried that twice and absolutely fried the tires so I had to get out of it or risk losing control. The only real runs I made were launching off idle. I still don't think that should affect mph but maybe I'm wrong. I'm going to take the car to a friend of mine next week and see what he thinks. The car was still pulling at the end of the quarter as well so I'm not sure if that means anything. Thanks for all the advice so far.

P.S. Quick 6'n'KC If I ever get this thing running right I might take a road trip with it to KC which is my hometown. I would love to run it at KCIR with it tuned right to see what I could do at sea level.

 

[UNGN]

Put 20-30 psi of air in a right side air bag to reduce the uncontrolled tire spin.

The density altitude could have been 7000ft, but 23 psi of boost should have done something to overcome this.

What is your fuel pressure? It should be less than 44 psi. If it's 50psi, there is one of your problems.

 

[Quick6'n'-K.C.]

BRING IT ON OVER!! im 24.5 miles from the track