N2RACINGLS1's

iTrader: (2)

Here is my take you changed from 26's to 28's you need to check you pinion angle on the drive shaft. You also need to either remove or at least unhook front sway bar. You also need to get adjustable shocks on the front along with the correct coil over springs for the front. If you cannot get the front end up and the weight of the car on the back tires traction will always be a problem.

I would not adjust shift points I would adjust the rev limiter to at least 6,600 RPM's to take care of the shift extension. Your gear is OK for now! The photos I included are what you need to get your car to do! Well you do not need it that high but you need the front tires with very little weight on them.

Good Luck!

N2

Vetal

iTrader: (3)

So when I went 26 -> 28" slicks, I had to change pinion angle? Could that really affect anything?
Everyone says about front sway bar, seems I have to do that first
Yes I've ordered front Strange from Midwest Chassis about 3 weeks ago but they still haven't even ordered them from Strange... Waiting...
Yes I see what you mean about shift points/rev limiter but I think it's pointless setting anything now since revs go up very quickly since I'm spinning a lot

heymoej, on the video I had street wheels. But weight of front wheels doesn't affect traction I guess, it's that front end doesn't want to raise above front wheels...

Vetal

iTrader: (3)

So when I went from 26" slicks to 28", my rear end raise 1", and pinion angle became more negative, but according to this post from Madman it shouldn't affect traction in a negative way...
https://ls1tech.com/forums/4507351-post8.html

heymoej

iTrader: (67)

front end weight is bad for weight transfer......
more weight is harder to transfer, which means you have to have your suspension that much better dialed in.

the lighter the front end the easier the weight transfer is to the rear.......then on launch it is easier to transfer that less weight to the rear end.

1ltcap

it looked to me like you spun the **** outta those tires. couldn't tell if it was just on launch, or when you were trying to load the converter.... but you lost a LOT right there on the line.

Vetal

iTrader: (3)

Yepp exactly spun like crazy, and that's what I'm trying to solve and ask for advises... I know track is very bad, but 28x11.5 at 9-11psi should hook a lot better (and I did hook a lot better few years ago).

I don't know, maybe key is that rear end now sits so much higher relative to the front than it was back then?

Sixspeed02TA

iTrader: (4)

I'm normally just a browser but I'm partial to black TA's so I thought I would offer some advice.

I have not followed your build from the beginning so please excuse the ignorance for the specifics of your setup. I agree that with your trap speed (Mid 120's) you have a mid to high 10 second car. You gain or lose that time in the first 300 ft.

Starting with the obvious:
A poorly prepped track is ..... a poorly prepped track. Traction will be challenging. That being said, plan accordingly.

Launch Consistency:
You now have a turbo car. It will not react the same way a NA, S/C or N2O car does off the line. As you know, you can’t drive up to the line stab the gas and go. You must learn how to effectively stage, spool and launch the car without upsetting the rear end or burning up the transmission. In the first clip you were actually spinning the tires before you ever released the brakes. In the second clip you blew the tires off in the first 3 feet. Once the tires break loose, the torque generated by your setup is going to spin the tires to the moon, irrelevant of your shift point, rev limit, or rear gear ratio. A 4L80 has so much rotational mass that getting the tires to hook back up is challenging. At a minimum for you to be consistent with your launch technique, you need a two step rev limiter. It is much easier to dial in your launch RPM and build boost if all you have to do is stand on the brake and mash the gas.

Gears?
Your final gear ratio is not your immediate problem. In fact, I run 3.73 gears with a 4L80E and stock shocks / springs with consistent 1.4X 60’ times (3700lb race weight). Note: a 4L80E actually has a taller first gear (2.48) than a 4L60E (3.06). The lower rear gearing isn’t such a bad thing.

Rear Setup
Check your pinion angle. (Yes it matters) MT ET Drags aren’t the best but; tire pressure should be 15 - 17 psi. I would recommend MT 275/60 15 DR or a set of Hoosier DR.
Don’t listen to anyone who tells you the rear of the car is supposed to “squat”. On a properly setup drag car, the rear should actually rise a half inch or so when the rear is planted into the track. The front suspension should also raise slightly indicating weight transfer. I assume you have lowered your car, hence the relocating brackets. Those should be adjustable; experiment with different settings. You want the LCA’s parallel with the ground or slightly sloped down toward the rear of the car.

If you don’t already have one, get a rear anti-roll bar (Not a sway bar). Wolfe and BMR make nice units. The purpose of this bar is to balance the weight of the car on the back tires. To set one up properly, you need to have the car on a set of corner scales with you in the driver seat. Adjust until the weight is evenly distributed between the rear tires. You mentioned in another post you were having problems with your posi-unit slipping. I couldn’t tell in the video, but if you had one tire spinning half way down the track that won’t help you at all. If it’s not a street car, throw a spool in it and be done.

Boost Controller?
A good boost controller like an AMS-1000 is irreplaceable on the track for tuning the power for the track conditions. It’s super easy to change your launch boost and ramp rate to accommodate a slippery track. All your boost coming in at once can often overload the track even if you manage to hook it out of the hole.

Rev Limit?
I don’t know anything about your motor, but if you have a good set of heads with decent lifters and springs, there should be no reason why you can’t turn that motor to 6500. Unless you have an exhaust side flow problem (turbo housing or exhaust), your car should be making tons of power in the 6000 rpm range. LET HER EAT!

I’m not trying to fill you with a line of crap or brag about previous accomplishments. Please take my advice at face value. Seat time will help you more than anything else at this point. Your car runs well, is a hell of a lot of fun to drive around, and will smoke the tires for 1/8th mile. Take pride in that for the brief period of time this brings you grins. The speed bug never quits and you will always want to go faster.
Peace

Vetal

iTrader: (3)

I didn't reply here cause I wanted to measure all angles before posting more. Finally did it.
Sooo... my torque arm is -2.5* (lower in front) and my LCAs are 6* and 7* (higher in front).
That was with 20-24 psi in slicks (street driving) so at the strip rear might sit 1/2 lower with 10-12 psi in slicks.
Suggestions please?

Sixspeed02TA

iTrader: (4)

Vetal,

The torque arm value you provided isn't especially useful. The Pinion Angle referenced is the angular difference between the pinion shaft inside the rear axle and your drive shaft.


Read this thread for how to properly measure pinion angle:
https://ls1tech.com/forums/suspensio...ion-angle.html

The reason this value is important: As torque is applied to the axle it has a natural tendency to rotate the pinion up. For drag strip applications we typically set the pinion angle at ~ (-2.0deg) so under acceleration the drive shaft and pinion gear inside the rear axle are a straight line. However, for normal driving, this may introduce a very small amount of drive-line vibration.

I wouldn't expect dropping your tire pressure is going to have a very dramatic effect on that measurement.

Your lower control arms slope down toward the rear axle. You never want them to slope up. That's why lowered cars usually have to run relocation brackets.

10 psi pressure in bias ply slicks can be a handful at 120 mph. Get some radials! They hook just as good.


If you don't have at least a 2 step rev limiter it will very difficult for you to get consistent launches. If you don't know what a 2 step is:

The factory computer is a 1 step rev limit....it kicks in at what ever you program it to (ie 6200) no matter what.
A 2 step gives you another rpm setpoint to limit rpms to....for your application it would be activated by your brake lights. So as long as you have your foot on the brake the motor is limited to what every you program it to (ie 2800). This lets you stand on the brake, press the gas to the floor and not instantly take off. As soon as you release the brake that rpm limit goes away. This lets you dial in your launch rpm and to some extent your launch boost. You will always have that 2 step rpm set low enough that it's impossible to spin the tires prior to releasing the brake. (Which is something I saw you do in your video.)

Go back to the track and get some more videos for us. Racing is the fun part.

Vetal

iTrader: (3)

Sixspeed02TA, thanks for that valuable post!I actually was expecting it would be much easier to launch since I went to A4. It probably is, but I'm clearly doing smth. wrong
P.S. Didn't notice I was spinning standing at the tree already
Yepp I also didn't think this gear is SOOO too short, I think many are running even shorter gears with tons of power

It's between -2* and -2.5* depending on tire pressure. Obviously it increased when my rear end raised at the tree...
Yepp I learned from here solid axle doesn't have to squat. BUT my squatting much less powerful Nissan gets better 60ft LOL. I don't know whether this what you see in video is "tires planted" or the opposite, car trying to rotate over front wheels, reducing weight on rear tires...

hmm, I don't know what it is, must read then Although shipping to here is sooo expensive that it prohibits from ordering big heavy hardware. I didn't feel problems with spool this time - perhaps I didn't give it enough power before? :/

yepp controlling boost off the line might help, but can't afford 1000$ EBC...

Nothing too fancy - Patriot Stage2 heads, mild cam. TC78 might be limiting though (might be not, at least not at this power level)
I very much agree with you - it was long way, enormous amount of money (and work) for me, it's loud and brutal and fun, but I want it to FLY Maybe not 9.x but at least mid-10's.
Problem with seat time is huge - we just don't get many races here. Perhaps 7-10 a year, most of them are on the old dead asphalt (basically - small stone chips). Hell I need AWD

Vetal

iTrader: (3)

TA angle = rear end = pinion angle. I actually like Madman's way of dealing with pinion angles. Angle between pinion (=rear end) and ground = pinion angle; angle between pinion and driveshaft is driveline angle; only pinion-to-ground angle affects launch traction...

Well, 1" less sidewall is same as going from 28" back to 26" at the same pressure... About 0.6* if I remember correctly for 1 inch of change in rear height

Yepp they slope down toward rear, but 6-7 degrees...

I don't know, no drama actually... Yes I sail a bit but nothing that feels dangerous

Yes I know, I think it even can be set up in HPTuners. But, it's not that hard to set RPMs with foot actually. At least not after Nissan which you rev in neutral at the tree

I was at my local track which is nightmare actually... 7.82 @ 98mph spin spin spin
here's one low-quality vid:

Sixspeed02TA

iTrader: (4)

Sorry...fixed the link in my other post. Retard Error

LOL Well, it sounds like your having fun anyway. We are lucky enough to have numerous fantastic tracks thru ought the states. We tend to forget that.

Your car makes a lot of power early. If the track conditions are as slippery as you describe, you'll have to make a conscious effort not to hit it as hard off the line.

I believe MSD makes a 2 and 3 step for LS1 computers:
http://www.thunderracing.com/shop-by.../Rev-Limiters/
Something to think about.

The rear anti-roll bar I was referencing:
http://www.bmrsuspension.com/?page=p...&productid=299

Stripping all excess weight out of cars can help some, but I figure your pretty nose heavy with your Turbo. Yes.....you need to build an AWD Turbo TA. That would solve your problem.

heymoej

iTrader: (67)

I was at my local track which is nightmare actually... 7.82 @ 98mph spin spin spin
here's one low-quality vid:
[/QUOTE]


just for reference because of your mph......^^^^^^
my old 98 z28 a4 pt4000 373 gears on 26" et street tire dynoed 407rwhp....

it ran....
1.48 60'
7.00 1/8 @ 100mph
11.08 1/4 @ 121mph

good luck!

Vetal

iTrader: (3)

Damn! I was hoping I have more like 550whp, not 400, since your mph are similar

Vetal

iTrader: (3)

Just to let you know how bad our only track (this, where last video is from) is, couple of pics...

Vetal

iTrader: (3)

Guys what do you think from the vids, did I stage my car correctly at all? Is it OK that it raised rear end considerably when I brought the revs up?

Vetal

iTrader: (3)

I've also remembered that my timing was around 11-12 degrees in those runs, at 11-12psi of boost, is that too low? I probably should set it to 17-20 degrees I think?

Roarin_8

iTrader: (5)

Those are small rocks?! I'm sure those get very slippery.

I personally wouldn't race there especially at the trap speeds you are going, things can get nasty pretty quickly.

Vetal

iTrader: (3)

That's the only track in my country (Latvia). Yes this is what is left from what used to be asphalt It's here I can only manage 7.9s in 1/8

Roarin_8

iTrader: (5)

oh man, becareful out there.