OohShiny

Greetings all!

Wanted to see what everyone thought about ¼ mile time improvement. I’ve got an ’03 Touring 5AT and my ¼ mile times are kind of disappointing.

I’ve got several mods on the car – intake, plenum spacer, hfcs, exhaust, shift kit, 3.69 gears, and I’m tuned. Dyno after the tune showed ~ 235 whp / 240 tq. I’m in CO so adjusting for 5000 ft of altitude at 3% hp loss per 1000 ft, let’s call it approx 275 whp at sea level. ( Which I think is decent for this set of mods? )

Despite all that, I am running 15.0XX quarter miles up here (at Bandimere). Recent mods / tune definitely helped “some” – I was running 15.6s with just intake and exhaust and no tune. However, using NHRA altitude correction, 15.0XX at Bandimere is still only 14.1XX at sea level. I see all kinds of posts that completely stock 350Zs are running high 13s. Sad!

Anyone have ideas on what might be slowing me down? Weight? It’s a touring so I have nav, heated leather seats, custom stereo with a big sub, etc. Also I personally am 215 Lbs.

Wheel size? I read larger diameter wheels will hurt your ¼ mile time. I’ve got 275/30/R19s on the back – which are 25.5” tires. Stock on the track edition is 245/45/18, which is 26.7” - actually LARGER than what I’ve got now. So shouldn’t be tires? ( I’m not spinning or hopping )

Age of the car? It’s 2003 with 105K miles on it. Are there some parts I need to be looking at replacing at this age? Spark plugs were just done.

Scratching my head here – would like some input from others. (I'm aware FI will make me a lot faster. I'm more asking, with all these bolt-ons and a tune, why am I still slower than stock).

dnash

iTrader: (3)

What is your mph at the end? Are you spinning your tires much?

Basically, improve your power to weight ratio, improve your traction and keep practicing.

OohShiny

91 mph (96 mph NHRA altitude corrected) .

No tire spin. The 5ATs stock torque converter has a stall speed of ~ 2200 rpm and we're not making enough power at those RPMs at this altitude, to break the tires loose.

iideadeyeii

iTrader: (6)

First, there is no way you are at a corrected 275whp. That's a 40whp increase over stock and those mods would not give you that. You are pretty much at stock levels and should perform at stock level speeds. mid 14's. What gear did you do the dyno in? 4th gear would no longer be a 1.0 gear with shorter gears.

EDIT* 5th gear would be .93 and still would not give correct dyno numbers. Now I'm not sure if this is accurate, but 235whp x .93 =218.55
I would do a compression test.
I also assume your heavy wheels/tires are partially a factor