et, trap and other questions
 

I've searched around more than just this site for info on this. I have seen many explanations but I just have a few questions. First off I know this isn't a drag car but I am just having some fun before replacing my clutch.

Now my times have been terrible because of my launches I guess. My best time tonight was 15.7 @ 92 mph with a 2.537 60 foot. As I understand it with that mph my times should be better than 15.7, right? I know my launch is not what it should be and I am working on that. The track just seems different each time I go but I guess that you have to learn to adapt each time. Tonight all I could do was spin the tires.

With a passenger in the car the lowest I could run was 15.9 @ 89 mph but that was another trip to track. Below are pics of 2 runs on separate nights, both my 'best' of the night with no passenger. I've done a 2.3 60 ft but never been able to break into 2.2 or better.

My main question is if I am trapping 92 mph, what should I be getting for an ET with a decent launch? I saw some other posts of people trapping 90mph and getting around 15.4 but those were s1 which are geared slightly different I guess and I don't know how much of a difference that makes. I'm just trying to figure all of this out and welcome any helpful comments.

I'm 15.716 and 15.801 on these. https://i.imgur.com/X8hO4n6.png https://i.imgur.com/PWMPqf0.png

As you said, the launch is your weak point. Try dropping the rear pressures down if you didn't already. I'd suggest starting at 20psi and if that feels stable keep dropping it by a few psi on the next runs. Your trap speed is right where it should be, but you should be able to get low 15's. For reference Car and Driver measured an '09 at 15.1@93mph.

I usually have the pressure at 34 or 36 psi cold. I tried dropping it slowly, 32 psi, 30, psi, 28, 25.. The times actually got worse as I dropped it. My best run of 15.7 was with 36 psi. Since I have the sport model I should also have a weight advantage over the R3 that seems to be the one tested by everyone. My car isn't exactly brand new compression at 53k miles but it is not bad, I still cannot expect brand new results though.

better tires with around 20psi will get you in the low 15. keep practicing the launch to get 2 or below at 60 feet.

I see a lot of people saying if you are on street tires and not some type of drag radial that keeping the stock psi is the best idea. Next time I go out I am just going to stick to 34 psi until I have a better grasp of launching the car to remove at least one variable.

I would definitely recommend lower pressure as I mentioned. I've taken cars down the 1/4mi with much more torque than you have and the effect is noticeable, even for street tires. I have gone down to 16psi or lower for the driven axle, as long as the car still felt stable. Lowering the pressure makes the tire contact patch longer and should make it easier to launch.

It may not be 100% accurate, but a 0.1sec improvement in 60' can get you roughly a 0.2sec improvement on the trap time, so as mentioned above try to get that down.

Visual example :)

Attachment 222590

That is a bad example though as those are drag slicks which are actually made to wrinkle/flatten to give a bigger contact patch. They have a much softer sidewall which helps accomplish that.

Now if you lower the air in regular tires with stiff sidewalls you will not be getting the same effect. The general consensus about it seems to be that with the stiffer sidewalls and low pressure it could actually cause the middle of the tire to bow up(even if just ever so slightly) and reduce your contact patch. Of course everyone has their own opinion on it but that is what I have picked up from reading about it.

on street tires in a stock RX8 with likely a lot of mileage at this point???

:spew: