when to go with a taller tire?

[trbojo]

i am getting a little bit disgusted with this car. with a good tune, i was only able to get a best of 12.33 @ 108.7 at atco the other night. the 60' on that run was a lousy 2.03. i spun through 1st gear, leaving at 2 lbs of boost. this is on a 26" tall M/T et street. most of my other runs were 12.4-12.5, 1.7x 60's, and the same mph. a lot of people tell me i should should be in the 113-117 mph range with my combo and tune. i just feel that something is really holding this car back. i have been told that a 3" downpipe is the missing link. these runs were at 23 psi boost, 25* timing, a c-16/sunoco 94 mix, 760 o2's, and 0 knock. i'm just wondering if maybe going to a 28" tall tire would spin less, giving me a better 60', and also give me more mph on the top end. the car picks up 20-22 mph from the 1/8th to the 1/4. any help appreciated.

Thanks,

Joe

 

[Quick6'n'-K.C.]

Hi Joe-

What kind of intercooler and how hot out was it?

I dont think a 3 inch downpipe is going to give you what your looking for, i only saw 1mph increase when i went from a 2 1/4 to a 3 inch pipe.

What did you do differently to get the car to run a better et with a lousy sixty foot? were the 12.3 and 12.4 times and 2.0 and 1.7 sixtys the same night?

Those et streets arent the best tires, was it test and tune night with street cars? Was the track slippery, dusty or high in humidity?

28s should give you 1/2- 1 mph increase if you have enough horsepower, Hoosier makes a good tire and you dont have to drill the rims to keep them from slipping on the rim

HTH
BW

 

[azgn]

are you running 16" wheels?

 

[trbojo]

precision front mount. the track was supposedly sticky according to other people. i could not get mine to hook if my life depended on it. the 1.7x 60s were leaving with no boost at all. i think i left with 5 psi on the 12.33 run. i literally came out sideways! i think it was in the high 80's, low 90's. humidity was maybe 85-90 %. of course the lower times came as the night cooled down.

 

[trbojo]

yes. 16" gnx rims. yes. street night.

 

[azgn]

there is part of your problem....not enough sidewall on 16's to hook well.....that plus a crappy track.....if you decide to change tires, get some 15's and real slicks

 

[trbojo]

ttt. anybody else? why does the mph seem so low for my combo.

 

[crownvic96]

i think the temps/humidty might have really hurt your trap speeds.

i gave up on trying to tune my car right now because its so freaking hot and humid all the time here in huntsville, AL. i just set the trans + really safe(lots of fuel and timing retard at wot) until i can wait for some 70ish degree temps and low humidty again.

 

[Bens87tr]

Way too low of a MPH, look at his best in the sig. I've run my car in hot weather as well, and only lost a few MPH. Something isn't right. The boost and timing should be enough for 116 or so. Is that tranny/converter slipping? The 60' isn't good either, but that will take finding the sweet spot. Should be able to cut 1.8's with those tires (I run a 16" as well). Any Directscan files?

 

[TTA850]

there is part of your problem....not enough sidewall on 16's to hook well.....

I dont think thats his problem, I've gone 1.47 on racegas with 26x11.5x16 ET Streets at E-Town and 1.51 on pumpgas and 27x10.5x16 ET Streets at Atco a few weeks ago.

Before you buy new tires my sugestion would be to try again, maybe it was track prep or the hot humid day or a combination of the two.

HTH,
Steve

 

[streetknight]

I went a 1.52 60 with 26x10.5 et streets(were 15's though). In 90 degree weather on that pass the car went 11.73 @ 113MPH and this was with a stock engine, tranny, and D5 converter, TA60, 3" THDP, 009's, and Stock IC.

Suspension was all stock except for 2 airbags, right set at 24psi and left at 5psi. Also boost was at 25psi.

HTH

 

[azgn]

TTA850, you are making a bunch more power than he is, so not really relavant

local car (12.0 type) switched from 16" 26 ET Streets to 15" ET radials and chopped a .1 off his 60'

16" tires on a drag strip is an unnatural act

my car runs low 1.5x on ET radials and low 1.4 x on ET drags...15"

 

[TTA850]

I know I'm making more power than him, but that was kinda my point - that 16" tires can hook. Yes 15" tires hook better, I'm not arguing that point, but in his case I dont see the tires holding him back.

Here's my car on a 16" rim:
pic

 

[Jeff Rand]

When you do your burn out make sure that you are not in the water( drive through it or back up into it then pull forward out of the water). It will splash up in the wheel well and will drip down giving you poor traction at launch.
Jeff

 

[Bens87tr]

The 60' is the least of his problems. Any idea where his MPH went?

 

[trbojo]

my point exactly. the hell with the 60' right now. i'm trying to figure out why this car won't mph!!

 

[azgn]

you were within 1.5 mph of your previous best, right? Lousy weather can account for that

on the other hand, you are leaving .5-.6 on the table with lousy 60' times

i would try bumping the timing some more and running straight race gas.......you could use something else to tune with also....egt, wideband

where do you shift?

what rpm thru the traps? (you do have an accurate tach, right?)

 

[trbojo]

shifting at 5200 rpm. good tach. traps about 4800-4900.

 

[azgn]

I agree you should be going faster.....run the boost and timing up (on straight race gas) and see what happens....

will the motor pull beyond 5200? If so, try 5500 or so....

maybe you got a flat cam?

maybe somebody with a similar speed can advise what rpm they are getting? (possible slippage in the trans?) I seem to recall that my car with a locked converter would do 120 or so at 5000.........foggy memory though

 

[MSDGN]

Just a thought but everytime I start to lose MPH and everything else seems to be OK...tune.. no knock...plenty of octane...etc... I check my spark plugs...usually after a few runs the gap opens up and I lose 2-3 MPH...now I just change them out everytime to the track...