Newaza

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SOTH probably has more experience than anybody on here drag racing with regular street tires and a stick shift. His words on this subject, whatever they might be, should be taken as gold LOL....
Good point SOTH on mentioning full tank. I didnt think to mention that. The full tank,tool box and whatever else you have in the trunk, adds to rearward weight bias, which is what I was trying to help him to achieve with sandbags. Look for some of the no prep big power guys with weight bars in the back too.
I actually try to run about 3/4 full tank too, I noticed that with the stock fuel pickup location if fuel level gets below about 3/8s of a tank or so is that the fuel pump pickup can become uncovered breifly if launching to try for 1.50s 60 foot time.

Watterson02

I was hoping you’d leave some wisdom for me. I’ll give it a shot. Any reason why you don’t use launch control?

Watterson02

yeah I’m definitely going to try a full tank, last time I was even below 1/4 of a tank. No fuel issues but it’s a good way to add some rear weight without making me feel bad lol

sonofthehill

iTrader: (1)

Yes, fuel all on the rear wall of the tank with extreme acceleration. I can finally rip down to empty, now that I picked up a hydramat pump sock, long side going up the back wall, works great.
I have several reasons for not using launch control, but... Mostly because I am old, just been launching sticks for too long to change now. I just can't seem to make a decent pass with any of that LC/FFS **** on.

Watterson02

I've done a lot of refining with the tune lately. Between fully tuning the ignition table for 100 octane gasoline, closed loop boost control, and a few other small things here and there.

First and foremost: Ignition Timing. I've been adding VP Racing Octanium Unleaded to the tank every time I get gas when I feel like running the full 26psi of boost. I was doubtful that this stuff would be worth it at $26 a bottle from parts stores (or $130 for an 8-pack from Amazon, which is where I will be buying it in the future), but holy **** it is insane. Here are my ignition maps with 93 octane from Weigel's with the VP Racing Octanium vs only 93 octane gas from Shell. Needless to say, the car fees much better now.


After this, I started messing with closed-loop boost control. I got it to be really good in lower gears like 2-4 and then good enough for me in 5th and 6th. My main goal here was just to decrease spool time up to the target boost by utilizing the function that keeps the wastegate from seeing any positive pressure until you're close to the target pressure. I'm ok with small fluctuations when it first cracks the wastegate since my fuel system is able to support the power at lower RPMs. It is the higher RPMs where I want to be extremely precise due to fuel system limitations (my stock NB FPR). These are the settings and number I ended up with. Feel free to point anything out because I wouldn't mind improving here, but for my usage I think it is good enough.




That brings me to today. I've been thinking about doing a little bracket racing with the group that goes to Bristol Motor Speedway (DER Racing) next year. There's a bunch of safety things I'd need to work on since at that point the technical inspections will actually be looking at the car, not just completely skipping over it like they tend to do at Bristol Street Fights. That includes axle loops due to IRS rear suspension and NHRA rules, driveshaft loop so I can put a slick on the car, a fire jacket, harness, and a few other things. I'll probably start working on those this winter starting with the axle loops since I plan on installing my new suspension bushings soonish. Also for this winter replace the 4.3 with the 3.6 ring and pinion that I bought forever ago, brace the differential housing, and possibly upgrade the axle (or at least keep spares on hand).

Also on my way to work today I did a few virtual dyno pulls since there's a couple really good flat spots on my way to my new job. Here are the results:


A few things to note: I was brake boosting on a few of these pulls just to get boost sooner. This also made the initial error worse than normal. Higher gears and brake boosting doesn't get me the best control over boost pressure. This was also taken in 4th gear, so not a 1:1 gear because I like not going to jail for excessive speeds lol. Anyways, I took this data and plugged it into a shift point calculator and it spit this information out.

Basically, I need to shift the car at the revlimiter in just about every gear. I thought surely I'd only be shifting around 7400 in just the low gears, but nope. Apparently, I should take it all the way, maybe even mess with raising the revlimiter. I need to think over that though. I already don't like taking it to 7800 or so.

The next drag race is August 3rd. I plan on running my 195/50/15 street tires to see how they do. I remember being able to get a better 60' on them, with less wheel hop, but less traction once the boost actually came on. I'm also wondering if the reduced rotational mass might improve my time/speed at all. Might not work, but oh well. I'm just testing things out. I might even get someone to haul my 245s and tools in case the 195s are just useless. I'm hopeful they'll work but somewhat doubtful. SOTH does it, but he's also much more skilled with a turbo that doesn't seem to hit as hard down low (Edit: Didn't realize he has a 6758, i thought it was a churbo for some reason). I'll go ahead now and say my goal is going to be a 60' in the 2.0x territory, 12.2 ET, and a trap speed of 119mph. Not too sure how realistic that is, but the reduced rotational mass and probably extra 20-40hp that I picked up from the igntion timing might get me there. I think it really just comes down to the idiot behind the wheel being able to launch the car.

Watterson02

Oh also, in regards to the boost control. You can tell exactly when it cracks open and goes to the initial target values by looking at the boost curve. I'm thinking by reducing the Boost Control Lower Limit to around 20-30kpa might help here. My logic is that when it first kicks on the Derivative term kicks drops the duty cycle significantly causing it to briefly plateau before the Integral term starts to windup causing to overshoot on its way back up. I don't have a great datalog to show this due to the rate of logging I use (I should reduce it next time, but we will see if I remember and am able to). Regardless, here's the data:

I'm not too sure if it is too much I term, or if it the lower limit being too low. I will probably mess with both next time I feel like tuning. Maybe this afternoon on my way home, who knows.

Edit: I just noticed the Injector duty cycle. Lol oopsies

42Miata

Was reading through your drag racing results and figured I'd throw my 2 worthless cents in on launching. Using nitto nt-01s (a very bad drag racing tire).

I run standard tire pressure 28psi all around
Launch control is set to 3200rpm (sometimes I have to go below 3k to not blow the tires off)
Boost duty is 0 in 1st gear, wastegate pressure only
I run reduced boost in 2nd

Even launching at 3k rpm, with the car making as little power as it can, I spin 1st, and if I power shift 2nd, I spin all of 2nd very easily.

I need tips from soth as well, he's cutting a better 60ft. With street tires on a miata, than I did launching a 350whp evo ix at the track.... I was spinning all 4 tires off the line and cutting 1.7s. That dude is a magician pulling 1.7s on street tires in a miata.

My car has:
Stock VVT motor
Gt2560r @ 16psi
Supermiata techna suspension
Nitto nt-01 225/45/15

SimBa

Insane numbers, congrats!

Watterson02

I think I was running 22-24 psi, maybe slightly less on my RT660s when I went last. I don't remember to be honest. I wish there was a good drag tire that was somewhere between full drag slick and otherwise street tire. Those muscle car drag racers don't know how nice they have things with their Nitto NT555RII and similar.

For the boost by gear suggestion, I believe this is MS3 only. I'm still on MS2 which doesn't have anything to support boost by gear. I've been playing with the idea of setting up a separate tune exclusively for drag racing where I use TPS to accomplish something similar. Basically set launch control to activate at say 50% throttle, set my boost target values to 0kpa under 70% throttle for minimum boost possible, and then only once into third gear actually go WOT. Sounds over complicated but I might give it a shot before then and see how difficulty it is to use. I should be around 15psi at wastegate.

I'm also on technas. Have you messed with the damper settings while you've been out? Last time I think I was on very soft damping settings all around. This next time I was thinking stiffen up the rear to autocross settings and put the front to max softness. My thinking was that it might help with weight transfer and in the case of wheel spin, less wheel hop. Who knows though, I'm far from a suspension expert lol. My ability of suspension tuning is about to the extent of "Ehh this seems fine."

I will say my best 60' time was without using launch control like SOTH suggested, but then again I'm pretty *** regardless of the method that I use.

Thanks
Despite the numbers being great, I'm still left wanting more, but impressing internet people makes me feel better about where I am at haha

sonofthehill

iTrader: (1)

I am cutting 1.7 60's on my technas, if the first click soft is 1, mine are on 9 all the way around. My tires are done, 60's got progressively worse last Friday, rotated and cut a 1.7 again. Can't find the ECS' anymore unfortunately. I am also on MS2 and run full boost, at least when my solenoid works, all gears. My newer turbo is a BW 6758, it spools very quickly.

sonofthehill

iTrader: (1)

Oh yeah, DA was about 2600ft on Wednesday, the 4th and 5th weren't much better. It makes a ton of difference.

Watterson02

Just to clarify, lower numbers are softer and higher numbers are stiffer?

Watterson02

Also, I've got my boost control working much better now. Very very happy with it now. You cannot feel any boost fluctuations at all now. Here are the settings and results:

Changes made: Differential gain 23% -> 18%, Boost Control Lower Limit 35kpa ->20kpa

sonofthehill

iTrader: (1)

If full soft is 1 and full stiff is 30, then mine are on 9. Also, my car doesn't have an idiot behind the wheel... It has a loose nut!
I look forward to seeing your sub 2 second 60's.