Arrvaxx's quest for the 10s.
 

The insane power that my Fast Intentions turbos provide and the lack of boosted 'representation' on the 1/4 mile thread has inspired me to taking on a quest: 1/4 pass in the 10s.

There are some rules. This is not about a drag build. My 40th Anniversary is a daily driver, a track car, a show car, and now a drag strip car and I will not ruin one aspect to maximize another. Versatility is one of the things that I love about the Z cars.

Rule #1: No permanent mod may significantly impair the car's ability to perform in any other category.

Rule #2: A permanent mod is one that cannot be used when driving the car to an event, cannot be changed or modified in 60 minutes only hand tools and a floor jack, or cannot be carried in the car to an event where it is installed. This time is cumulative both at home and at the event. A mod is considered permanent also if it requires changing fluids.

Rule #3: Driving characteristics can be changed as long as I can change them back to 'normal' and still conform to other rules.

These rules mean:

- I cannot use slicks because slicks cannot be driven on the street and I cannot use a trailer to transport them with me.
- I can swap coilovers with different spring rates either at home or at the event.
- I can change brake pads but not brakes.
- I can do a bit of weight reduction. Not sure I could swap seats and make other changes in the 60 minute limit but it would be legal.
- I can adjust camber -if- I can prove to myself that I can get it back to 'normal' consistently. If I can't and changing it requires an alignment then I will have to deal with the camber I have since some camber is required for the track and show.

This thread is about my quest, my journey from strip virgin to seeing 10s on slips. I'll post setups, pics, vids, slips, and impressions after each event.

This thread is -not- a drag racing tech thread. That thread, as it relates to me, is HERE. There we can discuss and debate everything. Please leave this thread to laughing at my noob shifting technique (but offer advice on the -other- thread) and other general nonsense.

:driving:

First drag event ever is next Wednesday, August 27th at Brainerd International Raceway.

Since it is my first time *blushes* I am leaving everything the way it is except camber. I would like to see if I can get it closer to 0 and back without much fuss. We'll see.

My OEM tires are shot so I ordered new ones all around, Hankook R-S2s. 275/35s front and 305/30s rear. I'm going to leave the OEM fronts on but mount the 305s to the rear. After the event I'll change to the 275s in front. Technically this isn't against my rules since I am not mounting tires just for the event. I am moving to 305s for every day use anyway and just not mounting the 275s (stocks are 245s) until afterwards. Not that it will matter if I have 245s or 275s on the front when I am likely to miss three gears during the run. :D

Unless my first run is magic I am going to stick with 93 octane on my 91 octane tune. It is hard enough to keep the tires from letting go even in third. I need to get a few dozen runs under my belt before unleash 604hp!

Youre about to find out precisely how crappy the 370z is as a drag racing platform in its natural state!!!

I think with a lot of work, practice, and thinking you should be able to get an occasional 10 second pass following your guidelines (which pretty much limit you in every way except for running a big 18 or 19" tire)

Adjusting the alignment yourself for the camber can be done, but its not as simple as just adjusting the camber. When you move the camber, the toe changes a ton. I would recommend putting the car on an alignment rack and setting the alignment both ways using only the eccentric bolts to make the settings, and scribe the 2 positions for each adjuster on the crossmember so you can go back and forth as you wish. You will probably find that with 0 camber you dont notice any negative effects in handling on the street, and just leave it that way. The only negative I have found of running at almost 0 camber is that it looks stupid on this car... due to the body shape it actually looks like positive camber. But even on the street, you will want all the traction you can get, and I dont imagine you dialing the alignment back in to the slip-and-slide position after you see what a little more grip feels like.

Good advice. We are lucky and have a hardcore alignment guy in the cities. He does a lot of the race car setups. I'm sure he would be willing to let me move and mark. If that worked I'd be pretty pleased. Can't have 0 camber in a show!

First drag night...not the worst ever.
 

Went to Brainerd International Raceway's Wednesday Night Drag Races last night. Results were mixed but overall for being my first time I am pretty please...and had a hell of a time anyway.

For you guys that just can't wait:

Tires: 305/30r19 R-S3s rear inflated to 25psi cold/30psi hot. 245/40r19s Protenza inflated to 38psi cold and hot.
Suspension: Swift lowering springs, Whiteline rear diff bushings.
Gas: 93 octane on 91 tune, half tank.
Weather: 75 degrees and overcast.
Other: Zip. I didn't take anything including the spare out.

Best run: 13.21 @ 115.92mph.

Ok, now the more interesting stuff...this is a journey thread anyway. :)

The car is 100% responsible for not making the driver look like a fool. No, not kidding. I have a long way to go when it comes to launch. I had a really hard time holding a consistent RPM below 3500 or so. I gave up and tried launching at 3500 but would either get wicked spin or red light trying to ease the clutch out to avoid that spin. Annoying but hey, virgin over here so whateva'.

Out of 10 runs I only blew three shifts which made me happy since the week before at an autocross that included a runway run I was missing them all day. I really saw the benefits of a short shifter. Put that on the list.

The car is a monster. We don't have a lot of 370Zs up here in Minnesota, fewer that are boosted (most are supercharged), and even fewer are raced on the 1/4 or track. So when I would screw up a launch and still run down a Mustang XYZ I got some looks. Even the announcer made a comment about what was hiding under my hood. That was fun.

So I have 1.21 seconds to shave before the 11s. I know that 100 octane will get me most of the way there and a proper coilover setup will seal the deal but I want to get in to the 12s without either first. They are so close and getting there will tell me a lot about my launch control improvement. And at this point it is clear that to get in the 10s it will take a combination of 50% launch improvement and 50% improvement in the set up.

I found with this car you'll need somewhere around a 125 trap to get low enough in the ETs. Like Charles said these are just not drag cars. Hell up here James (Jmac88) is doing everything he can just to get into the 11s at ~120MPH.

Your making a very tall order for yourself, but I look forward to seeing how you go about it.

Goodluck!

IIRC a factory sport touring (with a professional driver) will do a 13.1(ish) in the 1/4. With your power and some practice I don't see why you can't drop that 13.2 way way waaaay down.

With your current tire setup, I wouldnt even be trying to launch at all! I would roll out and ease in the throttle. Those tires arent gonna hold nuttin!! Ease in that throttle and dont try and pull much harder than stock through first gear, and into second push it a little harder, then by 3rd you should be able to go full throttle if the track is a little sticky.

Your trap speed shows some promise. You will get well into the 12's with your current setup and practice. I think you will need tires and alignment to get middle 11's.

Thanks phunk.

Talk to me about what you consider a roll out. Like aggressive red light launch or not even that?

What about when to shift out of 1st? 6500-7000 comes so freaking fast. Should I shift a lot sooner like at 4500 or 5000? The turbos really come on hard in second but I feel like they aren't helping much, or are hurting even in 1st so I feel like I want to GTFO of 1st quick. But psychologically it is hard which is why I didn't try it last night.

What about RPMs after 2nd? Like I said, things come up so fast and while I think my shifting is crisp I don't have a short shifter. So I was shifting at 7000. This leaves me one tick from redline in 4th crossing the line. I know that I have to be well in to 5th if I go any faster...question is how to get in to at the right time. *Edit: I just watched the videos...I was shifting after 7000 but before readline.

Generally, you always shift as late as you can due to torque multiplication. But when you have a scenario where gear A or gear B will BOTH just light up the tires anyway.... well in that case it makes no difference aside from what is easier to drive... and that will be the taller gear. If you still cant go full throttle in second anyway, then I would experiment with early shifting and seeing if you can do it without the car landing too low in the powerband in second. Otherwise, always shift as late as you can.

One thing I have noticed about my car, it doesnt like to shift while the wheels are spinning. I havent really sat down to think about that one... but I have observed that if I am in first gear banging the rev limiter from tire spin, its not going to let me into second (nasty grind) unless I let off for a moment. I assume the tires and drivetrain need to decelerate down for everything to be happy and allow the shift, just havent really thought about it yet.

I have the same issue. I try to get out of first as fast as I can with reasonable throttle input, then mash *within reason* the right pedal from 2nd, on.

Never thought of that before but you guys are right. Banging second gear can be difficult, it would be so awesome to have a torque limit per gear so you could contain it down low. Every other gear works flawlessly, I can no lift shift all the way down the track with no issues. Its just that 1-2 which kills the ET.

I too recall having that issue several times! id drop the car down into first to do a little pull and shifting at 7500-2nd gear my clutch would just screech instead of changing gears. makes me worry about no lift shift in my racelogic honestly I don't want to be causing inadvertent damage to a trans/clutch/flywheel.

I will come off spinning while feathering through 1st to 7.7k and bang the **** of second with no problems with the tires spinning.

If you want to hit your goal, you will need to run M/T street Pro's and click off at least a 1.4-5 60'. I like your ambition but you will never hit into the 10's without leaning more towards a real drag set-up. I got a friend that has a 2013 ZR1 with a tick over 1000whp and runs cheater slicks and best yet was a 10.1. He isn't really launching but rolling on the throttle. He can roll on throttle and catch up at the big end with the power, you are going to have to heat the tires up and launch the **** out of it. You don't have the power to pull a 10 down in the big end, you are going to have to make between the 60 and also the big end.

Oh, I am not boosted and was on **** rears when I clicked off a 13.4 @ 103. You have the MPH at the finish, but your first half has massive room for improvement. And 1.9 60' which is still crap.

Yes, massive room for improvement. Which I expected having done this once.

Thanks for all the feedback. Validates my own thoughts on what needs focus. I think this Wednesday night I will try a few things including shifting in to second earlier. I think I might try shifting before recline. If I remember correctly my hp peaks at 6800 or 7000.

*Edit: Using the 91 octane tune numbers.*

- So my torque ramps fast and starts its gradual decline at 3500rpms.
- Torque and HP cross at 5250rpms.
- From 5500rpms to peak HP at 7250rpms the HP difference is only 10%. By redline I've lost that 10% and am back down to 5500rpm HP.

My thoughts on what this tells me...looking for validation or correction:

- If I launch at 3000rpms my torque is a full 100lbs less than 3500rpms. Launching at 3000rpms vs 3500rpms should help to keep the spin down. ?
- I should shift from 1st to 2nd at 5250rpms. Landing in 2nd should put me at peak torque. If the R-S3s are warm I won't spin in second.
- I should shift from 2nd to 3rd at 6500rpms which will land me at 5250rpms...right when HP overtakes torque.

Finally...4th. As I mentioned on Wednesday I ended the 1/4 mile just a tick shy of redline. I'm 'thinking' that I should shift from 4th to 5th at 7000rpms. At 7250 it drops like a stone so I think it would be better to shift earlier than later or risk the chance of shifting too late. I might even do it at 6500. But the car pulls sooooo hard in 4th it is hard to not let it have every moment it can there. But it has to be better to get the car in 5th sooner than shift 10' from the end or even worse hit the limiter and watch it suck out the power.

http://www.the370z.com/members/arrva...pecialty-z.jpg

Do you load up the suspension at all before the tree drops?

If you are not spinning top of second or into third, then you want to take second gear all the way to redline. Dyno graphs are a little misleading... see, even though we call that graph "rear wheel power", it is NOT rear wheel power. That graph is ENGINE power as measured at the rear wheels. So it does not take into account gearing. It only takes into account drivetrain loss.

With the 370z stock final drive and transmission gears, first gears absolute ratio is 14.00. Second gears absolute ratio is 8.58, and third is 5.99.

Reference your dyno chart at any RPM you wish. Take the number either HP or TQ and multiply it by your absolute gear ratio. THAT is your power to the axles. When you do the math, you will find numbers that are insanely high in low gears. YUP! Imagine what 100fb lb of torque feels like when you tighten a lug nut with a torque wrench, and then try to imagine that amount of torque powering a honda civic to 14 second 1/4 miles... Then it will start to make sense. 100ft lb can only do that after its multiplied several times through gearing.

This is why, unless you are spinning the tires, you keep the car in the lower gear AS LONG AS YOU CAN!!! Power applied to the wheels in second gear is nearly cut in half from first gear. You loose like 25% from second to third, not as bad, but obviously very significant.

Interesting. Thanks!

If you want to do the supreme calculations to figure out how to drive your car on paper, input your dyno graphs and gearing into a spreadsheet and make yourself a graph like this one. This graph reflects torque to the axles in an ITR for each gear comparing 3 different final drive options.

Build a graph like this, and you can figure out when its best to shift, which will almost always be redline.

Another thing you can TRY and do but its really sloppy, is estimate roughly how much torque it seems like your tires can take before they let go, and try and stay under that but close to it as possible. Tons of error in there though as so many things will cause the tires traction limit to fluctuate heavily on a street car. It can get closer though if you work at doing things consistently as far as tire pressure and temps and application of clutch.

http://www.team-integra.net/images/B...erx/itrfds.jpg

Haha. Maybe when I am trying to break in to the 9s. :)

LOL its not really required for selecting shift points anyway, its more for deciding on gearing changes. You can see for yourself on that ITR graph that there is never any point on the graph where the next gear up was able to get more power to the axles than the gear before it. So you shift at redline for best acceleration.

You can also notice that the transmission gearing was intended so that if you shift at redline, you are landing in the peak of the next gear. To shift any earlier would cost major power... so you only do that if you cant use the power anyway.

This might help you out, made it awhile back just for fun.

http://www.the370z.com/nissan-370z-g...readsheet.html

Just got back from my second ever drag night. I am very pleased.

I shaved .8 seconds off my best run on my first night (down to 12.47 @ 117.62 mph). I was going to credit all of the improvement to it being slightly better turbo weather but then I looked at my slip. My 60' was .3 seconds faster and my 330' was .5 seconds faster. So I am claiming .4 seconds of the improvement for myself and better launches. The other .4 can be claimed by my lovely, lovely turbo twins.

I've had this EXACT issue both on the drag strip, as well as the road course. 2 gears inparticular stick out to me, 3rd and 5th. I remember being on the straight stretch 4 laps in a row, and the car literally would NOT LET ME PUT IT INTO 5TH?? I was like, wtf, there is NO WAY that I simply cannot find the gear??? Then I realized when I lifted completely off the accelerator early and shifted early with no redline, it allowed it to go in.

This past weekend, I had the same issue going into 3rd, causing me to shift early and actually held the clutch in early, delayed, and then shifted just to make sure I could get a run in without the car refusing me to get it into 3rd.

THEN, of course the fuel starvation. Have had this on the road course, saying I had over a half tank, yet completely shut the car off in the middle of accelerating on the straight. Wouldn't start back up, disconnected the battery hoping it wasn't something electrical. Sure enough, once I reconnected, the fuel meters/lights were completely empty. Have also ran out of fuel/cut off during auto-x events and exit ramps on the way to events.

uggggh, the struggles of the 370, yet I still love this damn thing and can't get enough of ittttt!!!

Arrvaxx: Quick question... on the last pass, you was running at 492hp?

His car is probably making less power . Only reason I say this is because 492 hp was basically at sea level(tuned in California I'm assuming) and that track was at 1200 ft. above sea level.

Explains why he wasn't able to trap in the 120's. If he wants to break into the 10's, moving down in elevation may be one of the things he has to do to get there.

Is it that high? I had no idea. Good to know, thanks.

head out to the east coast. :stirthepot:

got my best ET's in MD.

I don't know how linear the power loss is as you climb from sea level to whatever elevation, but I'm at 3,500' and if I come down the hill to 1,200', there is a significant difference in the performance. I'm also guessing the car will run a little richer at elevation as well.

It's most noticeable in launching the car....

Found this:

Wallace Racing - Braking HP Loss at Altitude Calculator

500hp at sea level = 482 at 1200' = 464 at 2400' = 446 at 3600'... linear (18hp/1200')? Really? That doesn't seem right.

I'm pretty sure my numbers are largely due to -me-. I'll get better.

Crazy number of calculators at the site: Wallace Racing - Automotive Calculators

Remember to that there is about a 18 to 20% difference between bhp and whp...whp being the lesser of the two.

Right but I was just investigating the affect of altitude on HP; was it linear or not. It appears to be linear which doesn't feel right but hey...who am I.

10-4, I'm not an engineer nor did I sleep at a Holiday Inn Express!!!

That peak hp calculator is a gross over simplification of reality as it is based only on standard atmosphere with elevation. Also, that calculator does not really apply to your car since you have turbos which will just work harder (up to a point) to make up the pressure loss from increased altitude and temperature (aka density altitude). It may take your turbos a little longer to get peak boost and peak torque and therefore it will feel less responsive in the low and mid range rpms, but generally speaking your peak HP numbers will be much less affected by changes in altitude when compared to us lesser NA folks (and even supercharged vehicles to lesser degree). Superchargers are mechanically driven so they will only increase manifold pressure by a fixed amount relative to the outside air pressure. Your turbos will keep working until they hit the wastegate spring pressure (regardless of the outside air pressure).

As I alluded to, density altitude is the more relevant factor in assessing power loss of an engine as it accounts for changes in air density from both altitude and temperature. Density altitude is not linear but its kinda close. At 1000ft elevation and a temp of 70F, the density altitude is more like 2000ft. Humidity will also rob power as the air mass is replaced with water vapor at the same pressure.

Outstanding explanation and according to my butt dyno is spot on. It's weird how on some days my car's responsiveness is like a dog until it gets wound up and then other days she just move out like being at a lower elevation. I assumed that is was mostly a factor of atmospheric conditions. Humidity and high temps are killer period!

Thanks and repped...

seeing that makes me feel accomplished since i still have a better time than most of the guys at lower almost sea level areas lol :stirthepot:

By the way you should try the da calc on dragtimes

Cool! This has density.

DA Calculator - Density Altitude Calculator - DragTimes.com