Bad performance at the track...????

birdofprey

Registered User
So last year i was running low 14's with a best of 14.1. My mph were right at 96mph or right around there. I have been fixing all the little things wrong with my car like vacumm leaks and exhaust but still to no avail. the last couple times at the track i have been running high 14's, with trap speeds of 93mph.
Now the only thing that has changed from last year is 3.27 gears, and march underdrive pulleys. now I would think with those two mods there i would at least be able to take a tenth or two off my times, much less not get any slower. But my car just doesnt seem to pull as hard as it used to.
My boost gauge it seems like im runing like 13.5 psi as to were last year i was running a little more than 14 psi. My car has 87,000 miles on it. Im going to start out doing some compression tests today. But any ideas???
 
WHat are your 60 foot times..Just curious...

If your boost level has gone down chances are you have some sort of belt slippage or boost leak issue...Try a new Dayco, Gates or Goodyear belt,,Change the jackshaft to crack belt as well as the jackshaft to blower belt.
 
well I'm still kind of new hear but if you are running underdrive pullies then I would think it's going to underdrive the supercharger as well. and another thing to think about is how is the weather compared to last year?
 
3.27 gears commonly result in slower times at the track with a stockish 5spd. You end up with worse traction and you also end up spending a lot of time in 4th gear well below your power peak. I do not recommend 3.27's for a stockish 5spd.

Weather plays a big role also. Post both slips if you can.
 
track timeslips

run one:
60' 2.178
1/8 9.488
1/8mph 74.799
1/4 14.776
1/4mph 93.220

run two:
60' 2.171
1/8 9.488
1/8mph 74.671
¼ 14.773
¼mph 93.109

It was about 66 degrees out last night, and it was in the mid 70's last year when i was running low 14's last year. 60' are about the same, traction doesnt seem to be that big of a problem with the drag radials. So i really dont know what is going on.

Also the car has all new gator back belts on it.
 
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Might have figured it out

So after looking everywhere i can not find any of my time slips from last year. Just got done with college so im guessing they got lost some where along the line of going from here to there.



But today when i was driving around all of a sudden a very loud exhaust leak started to appear(cant hear it at idle, only under load). After looking into it im leaking somewhere by the exhuast manifold. But its not where the manifold connects to the down tubes. So maybe a gasket? I dont know ill have to look into it more. Maybe it was starting to go the other night at the track, and i would think that would explain the low boost and other power problems.
 
Underdrives vs. Blower speed

1990_XR7SC said:
well I'm still kind of new hear but if you are running underdrive pullies then I would think it's going to underdrive the supercharger as well.
NO, Underdrive pulleys DO NOT change the speed of the blower. Reason: The balancer pulley has to pulleys on it. Only the one that drives the accessories is a different size. The one that drives the jackshaft, is OEM size.

68COUGAR
 
Hold'in 3rd.

XR7 Dave said:
3.27 gears commonly result in slower times at the track with a stockish 5spd. You end up with worse traction and you also end up spending a lot of time in 4th gear well below your power peak. I do not recommend 3.27's for a stockish 5spd.
Dave,

My times dropped quite a bit with 3.27's. Also, what's this about 4th. gear? When I first got the 3.27's I thought I had to shift into 4th. about 200 ft. from the traps. Now I just hold 3rd. at about 5200 through the traps.

68COUGAR
 
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