Lousy 60 Foot Time

[Bowtiez]

I originally set the s30 for track days and autocross.  Due to my age, I have now started drag racing instead.  The 260Z JTR conversion has a Richmond Super T10 4 speed, 500HP supercharged 350 V8, and a 3:69 R230 Dif conversion with 315:35:17 Nitto drag radials.  The best an experienced friend of mine could get out of the car was is a 1.95 60 foot time with 12.32 et in a quarter.  I have 275 springs in the rear and 300 in the front. He said this should be a high 10 or 11 second car if we could hook up.  Any ideas?

[RebekahsZ]

Switch to real drag slicks. To run that 315/17 tire Im going to assume you are flared. So, get some used 15x8 4.5" backspacing weld Draglites and mount up some 26x9 or 10 Hoosier or Mickey Thompson bias ply slicks. Put 15 psi air pressure in them. Let them smoke for a couple of seconds at 5000 rpm in a second-gear burn-out. To do a decent burn out you really need a line-lock system. With this setup and only 400hp I can 60' in the 1.6s all day and I occasionally go 1.4s. Be ready with a spare driveshaft and some spare axles, cause once you start hooking you will start breaking things. Install a driveshaft hoop of some kind. Remember, you will want to spin a little-dead hooking really breaks stuff. Do slicks before doing anything else. Just like autocross, tires do more for you than anything else. Ask around the track for who has any used 4-lug mustang Draglites (that's a dual pattern wheel: one set of holes is for Mustang; the other 4 are for Datsun). You may also find some used slicks. If you get this stuff used, you could be set for about $200 total. Buy new and it will be around $800-900. With a 4-spd, 26"tires and 400hp, you should go 11.0 at 125-130mph. A 2-step can be really helpful too. Try starting to leave the line at 2500rpm and work your way up till you find the point where you neither big, nor spin. Sometime you will break stuff when you find that sweet spot. If you only want to drag, you might re-think that manual trans.

Edited February 2, 2015 by RebekahsZ

[RebekahsZ]

Switch to real drag slicks. To run that 315/17 tire Im going to assume you are flared. So, get some used 15x8 weld Draglites and mount up some 26x9 or 10 Hoosier or Mickey Thompson bias ply slicks. Put 15 psi air pressure in them. Let them smoke for a couple of seconds at 5000 rpm in a second-gear burn-out. To do a decent burn out you really need a line-lock system. With this setup and only 400hp I can 60' in the 1.6s all day and I occasionally go 1.4s. Be ready with a spare driveshaft and some spare axles, cause once you start hooking you will start breaking things. Install a driveshaft hoop of some kind. Remember, you will want to spin a little-dead hooking really breaks stuff. Do slicks before doing anything else. Just like autocross, tires do more for you than anything else. Ask around the track for who has any used 4-lug mustang Draglites (that's a dual pattern wheel: one set of holes is for Mustang; the other 4 are for Datsun). You may also find some used slicks. If you get this stuff used, you could be set for about $200 total. Buy new and it will be around $800-900. With a 4-spd, 26"tires and 400hp, you should go 11.0 at 125-130mph. A 2-step can be really helpful too. Try starting to leave the line at 2500rpm and work your way up till you find the point where you neither big, nor spin. Sometime you will break stuff when you find that sweet spot.

Edited February 2, 2015 by RebekahsZ

[RebekahsZ]

Sorry for double post. Just how old is old??

Edited February 2, 2015 by RebekahsZ

[Ryan Merrill]

Tell us how your launching the care? IS it spinning? Hooking? Bogging out of the hole? What RPM do you leave at?

[Bernardd]

I'm curious what your trap speed is. What is the weight of the car? Can you post up your time slip?

[skirkland1980]

Putting slicks on isn't a cure, it's just a bandaid for a poorly setup suspension. Get the rear to squat and make sure the car sits level at rest. Make sure the rear and front suspension have enough travel and isn't binding.

[Bowtiez]

1) I am 68.  The last time I was on the Hallett track in Tulsa, I was racing with a Ariel Atom.  The guy got a little frustrated, passed me on a short straight into a very tight curve, realized he could not make it and slammed on the brakes while I was still at full throttle.  If I had been a split second slower to react, two cars would have been totaled. That made my decision.

 

2) I'll try to find a time slip.  I believe 113 was my trap speed with a 10.4 1000 foot.

 

3) We tried every kind of launch including a second gear clutch burner.  The result was still tire spin.  I think the key is getting the car to squat.  What spring rates do you recommend.  I have about 50/50 weight distribution now.

 

4) The T10 is rated for 325 lbs of torque.  My engine is about 500 lbs.  I am using an R230 TT Viscous LSD rear end set up with 3:69 gears and Moser axles. I am using 1310 Chevy Ujoints.  I wonder if use slicks, I will blow the transmission.  I think that is my weak link.

 

5) I am using TT brakes.  I don't think that 15s will clear the calipers.  I have an extra set of 16 X 8's that will clear as well as a couple 17 x 9s.   I can run 28's if I raised the coil overs.

Edited February 6, 2015 by Bowtiez

[skirkland1980]

Try raising the whole car up a bit to gain some travel. You can also try limiting the amount the front shocks extend to see if that helps it squat. If the front can't rise then the rear will have to squat. You may not need to change any parts yet. Just try working with what's there.

[weedburner]

-

Edited February 6, 2015 by weedburner

[weedburner]

Rear squat is not your friend if you gain camber. The bigger dia your wheels the less forgiving is the sidewall, and more the tire will be edge loaded with camber gain. You want the rear contact patch as perpendicular as possible to the track at the point of maximum acceleration.

 

Don't limit your front shock travel, maybe even extend the travel of your front shocks to get as much front rise and weight transfer as possible. Looser worn out front shocks would be better, as would softer front springs. Your rear spring rate is stiffer than ideal for a solid axle car, but that works in your favor to reduce the amount of irs induced squat.

 

Balancing "torque vs clutch" will help your ST10 live longer. Remember- your crankshaft/flywheel assy is an energy storage device. Any change in rotating speed represents a change in the amount of energy stored within. As an engine gains rpm, some of it’s output is diverted/stored as inertia added to it’s spinning crank/flywheel assy. Inversely anytime that engine’s rpm drops, the inertia energy removed from the spinning crankshaft/flywheel assy must go somewhere to make that happen. 

 

Example- say a vehicle is launched at 5500rpm and rpm is pulled down to 3500 as the clutch locks up. That 2000rpm drop directly represents inertia energy removed from the spinning crankshaft/flywheel assy that was directly discharged into the transmission’s input shaft. This discharge of energy is added alongside the engine's output, creating a momentary "spike" of increased torque output.  As rpm begins climbing while the vehicle continues to accelerate, some energy is diverted from the engine output to recharge inertia back into the spinning crank/flywheel assembly. 

 

The speed with which the rpm change occurs has a direct effect on the intensity of this energy exchange. If the duration of the exchange is doubled, it's intensity is cut in half. This is where the balance of "torque vs clutch" comes into play. If the torque capacity of the clutch is closely matched to the engine's torque, any extra torque "spike" will be dissipated as additional clutch slip and not passed along to the transmission's input shaft. This added clutch slip is actually helping in a few ways, extending the duration of the energy exchange (less intensity), and reducing the amount of rpm change (less overall energy to discharge).

 

Instead of changing clutches everytime i want to experiment with something different, i found it much easier to get some of the same advantages by installing more clutch capacity than required, then adjusting the duration of clutch slip using a small adjustable hydraulic cylinder attached to the clutch pedal. It's proven very effective. My Shop Mule is running 5.70's with 1.30 60's (700+ to the tire) using a 1-1/16" input / 28 spl output Toploader and 28 spline axles using a 2900# diaphragm PP for several years without failure. I've since started producing a more compact version of the cylinder used by the Shop Mule, here's a link.

 

An interesting note- if rpm remains constant from launch until clutch lockup (controlling clutch slip can make this happen), no energy is recovered or spent changing the speed of the spinning assembly. Because having a torque "spike" requires leaving enough reserve strength in the drivetrain to deal with that surge of energy, removing that temporary energy surge allows one to actually add more engine power while still staying below the ultimate strength limit of the drive train. This is the area i'm exploiting with the Shop Mule.

 

[skirkland1980]

Limiting front travel was something I did on my camaro but yeah you're right it might not work so well with irs.

[Bernardd]

Follow RebekahZ's advice.  He's right on the money.  You might want to consider an auto swap if you're going to be drag racing exclusively.  I have an auto with my L28ET and with 400whp and I hit 103 in the 1/8th mile and run 1.6 60ft times.  All stock suspension.

[RebekahsZ]

I don't know where you are located where it is still warm enough to race but I'm jealous. The car wont squat if it doesnt hook. Hook then squat. My car doesnt squat at all in the burnout area. If you get the chance, get a buddy to video the car a bunch as it launches (cell phone works great). Paint a stripe on the front and rear tires with shoe polish so you can see when and how much it actually spins. Get one of the grand kids to help you slow down the video so you can actually study it. You will get conflicting advice, so use whatever works. I race with a guy with a stock fendered, stock suspension (soft) with 26x10 MT ET Drag slicks and a T350 and he doesn't spin. I talk with jnjdragracing who runs blown SBC and A/T (glide?) with 28x10 MT ET drags, stock suspension and hard foam bumpstops after an inch of suspension travel (so basically no suspension) and he doesn't spin and totes his front end all the way down the track. I think tires are gonna be your solution. Borrow a set of rims and see what it would take to run them. I have AZC disc kit and I have to run 1" spacer adapters to clear the calipers, but with flares fenders, who cares? They were like $44 from eBay. I inspect them regularly and the studs stay torqued and have never loosened up. Look at my YouTube channel (search RebekahsZ) and you can see some of my launch videos and learn what you can from them and laugh about the stupid ones. Track conditions can vary so much day to day. I don't have enough power to rest do the 28s justice-I e only run them at our stickiest track and I was dead-hooking and running slower than I did on 26s. I let my tires spin a little so I can just drop the clutch and forget about it. Too much tire spin=slow. Too little=slow. It's all about trying to find "just right" and that formula varies with the track and even the weather. Wish you lived next door and we'd share some tires, but there won't be any consistent racing here till May. You can't worry that much about the suspension behavior until you hook at least enough to move the suspension. Then come back to shocks and spring rates. Those things do matter but not at the point where you are now.

Edited February 7, 2015 by RebekahsZ

[weedburner]

This is a 3000rpm no-prep launch with 3.73 gears, 2.78 1st gear, and 28" tall 275/60 radials...

 

 

Without the clutch slipper, it would be bog city.

[Bowtiez]

Try raising the whole car up a bit to gain some travel. You can also try limiting the amount the front shocks extend to see if that helps it squat. If the front can't rise then the rear will have to squat. You may not need to change any parts yet. Just try working with what's there.

The car was set up as a track day car.  I have 275 lbs coil over springs all the way around with Tokico adjustable shocks.  Gabriel is sending me some camber plates which will allow me to use 10 inch long springs in the front with 300 lbs instead of the current 7 inch springs.  I am going to replace the back springs with 200 lb springs.  This may help.  I called Qa-1.  The tech recommended to replace the back springs with 200s and the front with 225s.  This may also encourage me to drive the car more.

Edited February 9, 2015 by Bowtiez

[skirkland1980]

On a sticky track with sticky tires you can get away with little to no travel. When you have the opposite the only thing you have is the suspension to transfer the weight to the rear for you. You'll also have to play with your launching techniques since you have a manual trans which is not ideal.

[RebekahsZ]

Weed burner-I will be contacting you next winter to setup a slipper. I'm all in, but I have some other stuff to get done first. But I'm a believer.

[weedburner]

The car was set up as a track day car.  I have 275 lbs coil over springs all the way around with Tokico adjustable shocks.  Gabriel is sending me some camber plates which will allow me to use 10 inch long springs in the front with 300 lbs instead of the current 7 inch springs.  I am going to replace the back springs with 200 lb springs.  This may help.  I called Qa-1.  The tech recommended to replace the back springs with 200s and the front with 225s.  This may also encourage me to drive the car more.

 

A 113 mph trap speed has potential for around 1.60 sec 60'. With that much improvement in your 60, you would probably be around 11.50 et.

 

I run 100 lb/in springs up front. That gives more rise up front on launch, which raises the CG resulting in more weight transfer. I've even added 200lbs of lead inside the back bumper when it's needed. Basically you want all the weight transfer you can get until the tires hook, you can always decrease the weight transfer later if wheelies become a problem

 

After you get all the weight transfer that you can get, adjust your staging rpm until you find the sweet spot between bogging and spinning.

 

Don't give up on your ST-10 just yet. Here's something to think about...

...what happens to engine rpm when an automatic car launches? rpm basically rises from staging until the transmission shifts, no torque spikes created to knock the tires loose.

...what happens when the typical stick car is launched? rpm quickly dips down from the staging rpm, indicating a torque spike was created. The larger the dip in rpm, the larger the torque spike the input shaft and tire patch will see. Eliminate that torque spike, you can get more power down before killing the transmission or knocking the tires loose. In the past you had to buy an expensive adjustable clutch to consistently achieve this, but not anymore. You can probably use the clutch you already have.

[Bowtiez]

Gabriel at Techno Toy Tuning is sending me some 200 lb 10 inch springs for the rear.  I want to try the 275s I have on the rear on the front first.  I get mixed opinions on springs.  I need to weigh all 4 corners of the car.  The 50/50 is a guess based on where I put a floor jack so that the front and rear tires lift equally. The last time I ran, I discovered that the supercharger had lost boost due a blown hidden intake gasket. With the supercharger working properly, it should be all in by 2500 RPM and produce approx. 500 lbs of torque.  This may make for a brand new ball game.

Edited February 10, 2015 by Bowtiez