I i30 back to the track last night.

Track prep:
Removed throw rugs, spare, rear seat
MT DRs (255/55/16) aired down 15 psi
No air filter
Rear BCs raised 1" and turned to full stiff

Year of Engine: 2008 Altima
Engine Modifications: 3.0l timing, upper and lower oil pans, drilled intake cams/sprockets, 09' Maxima upper intake and (75mm) TB, 4" Intake, Q45 MAF, BPI flow stack, Aeromotive AFPR, Cattman headers, 3" SS exhaust Y-back.
Tuned: Rough tune with EMU, launching at 3800 WOT dump with 2-step
Transmission: AE 5MT VLSD

PBs
60 - 2.049
1/4 - 13.44
mph - 104.16

Slips: (7447)


My previous PB was a 13.66 at a slightly higher mph. The major differences are a 4" intake up from 3.5 and now using launch control. I think I lost a MPH since I'm revving 1st and 2nd longer and not quite hitting the top of 3rd at the finish.

This time at the track was beyond strange. I would hook ok then at the top of 1st all the way down the track it would feel and sound like either the tires or clutch was slipping slightly the rest of the way. The tach would sometimes hang and I could hear the engine revving up. Or the rpms would hang, the engine would sound like it was hanging but I'd still be accelerating.. When I looked at the EMU logs, the rpms and vehicle speed didn't have any spikes indicating slipping.

The only way I was able to get a couple 13.5s and the 13.4 was just by staying on it even though it felt like it was slipping. But at the same time that method also netted me a 13.9. Just weird.

I can only think of 3 things that might be happening.
-The pull of the revs up top is breaking traction
-The pull of the revs up top is causing the clutch to slip
-My axle vibrations at 25-30 mph and in general are creating tire vibes that break traction.

The first 2 don't make sense since dumping it at the line should also break traction or clutch grip. There's also no burnt clutch smell and I can't get the clutch to slip on the street..

Here's my ride height. I do run taller tires (225/50/18)


My question to you guys is.. have axle vibes done the same for others at the track?

Any other ideas?

 

Looking back over my logs, I'm leaning more to high rpm clutch slippage.

Here are my 13.5, 13.4 and 13.9 runs in order.
Go easy on me as the tune is rough..
I let off on the 13.5 since it felt like I was breaking traction
I bounced the limiter on the 13.4 but I stayed in it the whole time.
I also stayed in it the whole time on the 13.9 run but it felt like it slipped the most.. The rpms just hung in 3rd while I picked up mph. I didn't look at the tac because I think the rpms hung on the last one so my shift points were a little lower.





So possibly a high rpm slip even though I can launch a 2.0 60'?

Without any sporadic mph changes I would have to assume there's no tire slippage.

 

not inclined to try to decipher data logs while i'm on my phone but what you are describing sounds a lot like a slipping clutch to me.

regardless, nice mph. your car runs strong.

 

What gets me is, why am I able to dump it and hook a decent 60 with a slipping clutch?

 

nice wish you posted that you were going I would have went to watch, been dying to see this car in person. my guess is clutch slipping at higher rpm

 

t6378tp, same goes for your car man. That's a pretty refined turbo 4th gen you got there. I'll have to hit you up next time.

I'm on the fence about when I would do the clutch if I do.

 

What clutch are you running?

Get slicks, I wasted a lot of time racing with drag radials. Slicks make a night and day difference off the line. I was getting similar 60' to you when I had drag radials, then I got slicks and went to the 1.7x range.

 

I'm running a stock AE clutch that has about 40+k on it. 3.5 swapped the whole time. At this point I don't think the clutch really owes me anything. It's just weird I can't get it to slip at launch or on the street.

No doubt I could pull a lower 60' with slicks but if I think the car is capable of a 13.0 or 12.9 as-is with DRs. I would be perfectly happy with that.

 

There's going to be a open/meet at Pride Auto on Sandmeyer street this Sunday hopefully you can swing through. I'll be there but not with the max long story and I haven't updated my thread so don't want to spill the beans but can bring you up to speed there