What do you make of these 1/4 mile #'s

[Jack]

first up

September - US41 temps in the upper 60's lower 70's
best run

60': 1.646
1/8 mile: [email protected]
1/4 mile: [email protected]

Byron last weekend temps in the upper 50's

60': 1.676
1/8 mile: [email protected]
1/4 mile: [email protected]

same mods, same driving style, nothing different in the tune..

my 1/8 traps at US41 were in the 98-100 range and my 1/4 traps were 128-130, whereas at Byron the 1/8 was 102-103 and 1/4 121-123

any ideas?

Click to read more...

 

[Racerx66]

How's the clutch feel?

 

[Bob_Kurgan]

welcome to the "need a clutch" club... that is becoming the norm lately.

 

[Wiked03]

Yeah something isn't quite right at the top end it seems.

First things I would check are belt slip and clutch.

 

[Jack]

How's the clutch feel?

clutch feels OK, the last couple of runs at Byron is was loose off the line netting me 1.8 60 foots

but I just need to re adjust the fire wall adjuster, I had the same issue a few months ago


if the clutch was bad, wouldn't that hurt my ET, and not just the trap speed

 

[UWISHU1]

how can you tell if it's the clutch slipping or the belt?

my times most of the year when I went to the track was
1/8 mile [email protected] and my 1/4 mile was 11.90@119

would data logging some runs pin point the problem?

 

[Bob_Kurgan]

how can you tell if it's the clutch slipping or the belt?

my times most of the year when I went to the track was
1/8 mile [email protected] and my 1/4 mile was 11.90@119

would data logging some runs pin point the problem?

typically you can tell because if your belt was slipping, your 1/8 mile times would suffer too.. you accelerate through 2-3 gears by the 1/8 mile and go from 0-6500rpms.... same as you will in 3rd and 4th at the top of the quarter.. if it were belt slip, it would show up in all gears.. your MPH would be down in the 1/8 as well as the quarter.. i have ALOT of experience with belt slip from the renegade days.

 

[Jack]

how can you tell if it's the clutch slipping or the belt?

my times most of the year when I went to the track was
1/8 mile [email protected] and my 1/4 mile was 11.90@119

would data logging some runs pin point the problem?

the clutch test is to but it in 4th at low rpm ~1,500 floor the gas, if the rpms jump or climb very fast your clutch is slipping

belt slip usually results in belt dust

 

[Bob_Kurgan]

the clutch test is to but it in 4th at low rpm ~1,500 floor the gas, if the rpms jump or climb very fast your clutch is slipping

belt slip usually results in belt dust

sorta true and sorta not... if the clutch is not hot, it may not slip.. put some heat in it and itll slip like crazy.... when you roundy round your car, the clutch slips much worse at the track..

 

[UWISHU1]

sorta true and sorta not... if the clutch is not hot, it may not slip.. put some heat in it and itll slip like crazy.... when you roundy round your car, the clutch slips much worse at the track..

I notice belt dust so I replaced it with a 1" shorter belt. Went back to the track thinking my troubles where taken car off and still the same crap.

One thing that it has always done is 1st and 2nd gear the shift light would come on the tach needle would sweep gradually across the gauge. Then in 3rd and 4rth I'd miss my shift point or bounce off the rev limiter cuz the tach needle would bouce erradically (sp?) from about 5K thru 7K.

 

[gnxs]

Clutch would be my first suspect.

BTW Jack, the day at the track that my Dual Puck went south my ET's were almost right on, but my MPH was WAY off.

 

[Bob_Kurgan]

I notice belt dust so I replaced it with a 1" shorter belt. Went back to the track thinking my troubles where taken car off and still the same crap.

One thing that it has always done is 1st and 2nd gear the shift light would come on the tach needle would sweep gradually across the gauge. Then in 3rd and 4rth I'd miss my shift point or bounce off the rev limiter cuz the tach needle would bouce erradically (sp?) from about 5K thru 7K.

even makes more sense that its the clutch..

Did you see Pratt's clutch? I bet yours looks worse..

500+rwhp + 3800lbs car + spec 2 = angel looking for a new clutch

 

[Bob_Kurgan]

Clutch would be my first suspect.

BTW Jack, the day at the track that my Dual Puck went south my ET's were almost right on, but my MPH was WAY off.

you hit it on the head.. MPH is measured in the last 50 or 60ft of the 1/4 mile.. its 2 timers that measure the acceleration rate from the first sensor to the second sensor... i can hit my chute at 1250ft and run 8.20 @ 150mph or run it through the back door and run 8.18 @ 170... ET is almost barely affected..

 

[Jack]

you hit it on the head.. MPH is measured in the last 50 or 60ft of the 1/4 mile.. its 2 timers that measure the acceleration rate from the first sensor to the second sensor... i can hit my chute at 1250ft and run 8.20 @ 150mph or run it through the back door and run 8.18 @ 170... ET is almost barely affected..

well I'll head out to US41 this week if the weather holds

re-adjust my clutch and see what happens

at MSC I had a slipping clutch issue, turned out my firewall adjuster needed to be adjusted, once I did that my clutch was fine.

At byron I knew my clutch was slipping the last few runs because when I took off, it felt almost like I was spinning the tires, but I knew I wasn't.. it was obvious clutch slip.. then on the highway passing cars at 80-90mph it was also slip

btw I have the DFX & fluidanza flywheel with 6K miles on it and around 40-50 1/4 passes on it, I hope it's not shot this quickly

 

[Bob_Kurgan]

well I'll head out to US41 this week if the weather holds

re-adjust my clutch and see what happens

at MSC I had a slipping clutch issue, turned out my firewall adjuster needed to be adjusted, once I did that my clutch was fine.

At byron I knew my clutch was slipping the last few runs because when I took off, it felt almost like I was spinning the tires, but I knew I wasn't.. it was obvious clutch slip.. then on the highway passing cars at 80-90mph it was also slip

btw I have the DFX & fluidanza flywheel with 6K miles on it and around 40-50 1/4 passes on it, I hope it's not shot this quickly

sounds good..

FYI, us41 is a bad track to make comparisons too.. their 60ft is actually about 58ft and im unsure of the 1/4 mile.. you will almost ALWAYS run your best 60ft at the track vs other tracks in the area.. gld vs byron is always pretty consistent..

good luck, hope it was just an adjustment issue..

 

[Jack]

sounds good..

FYI, us41 is a bad track to make comparisons too.. their 60ft is actually about 58ft and im unsure of the 1/4 mile.. you will almost ALWAYS run your best 60ft at the track vs other tracks in the area.. gld vs byron is always pretty consistent..

good luck, hope it was just an adjustment issue..

well I'd be making comparison of US41 two month ago to the next time I go (likely Sunday) so it's a valid comparison

I adjusted the firewall adjuster and the clutch slip went away.

but I think I may have a header leak, the last couple of runs I heard a weird noise coming from the drivers side front, and now under acceleration/load I hear it everytime... I think it may be an exhuast leak somewhere.

 

[Mystic Terminator]

If you want a used 26 spline DFX let me know. When I was having trans problems I removed the DFX and put in Lyle's used dual friction. It might be worth a shot if you are doing the job yourself, but if you are paying to get the job done, I would suggest not taking a chance and putting in a new clutch. :alcoholic