1/4 mile - the eBay T3/T4 Chinacharger again - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-28-2009, 10:49 AM   #1
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Default 1/4 mile - the eBay T3/T4 Chinacharger again

Last year the car went [email protected] Boost was 12-13psi in the midrange then dropped to 10psi. Someone didn't have the ebc set up properly.

This past saturday night:

-2540lbs going down the track
-Almost corded, 2003 build 225/50-15 BFG drag radials, 29psi, BACKWARDS (forgot that they are directional)
-It was humid - altitude density 1975
-MBC
-Tell tale showed a max of 14.9psi, no real datalogging
-Button to run on WG (7-9psi) for the launch
-OTS Koni's: front-full soft, rear-full hard
-before the run the peanut gallery was talking smack about lame and slow Miatae.

1.8905 60'
[email protected]

R/T .4339 (this is significant because it was a pro tree)

No in car video but I think there were 3-4 external cams going. I'll post when I get them since it might be the best burnout I've done - in this car.

Last edited by dvcn; 09-28-2009 at 12:22 PM.
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Old 09-28-2009, 01:01 PM   #2
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Nice run.
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Old 09-28-2009, 01:31 PM   #3
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Wouldn't you want the suspension in the rear softer so that it squats?
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Old 09-28-2009, 01:48 PM   #4
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dvcn,
I know you run WI, but what are you using for engine management? Are you still on stock internals?

I can't wait to see the video.

Good job.
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Old 09-28-2009, 02:28 PM   #5
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Quote:
Originally Posted by jayc72 View Post
Wouldn't you want the suspension in the rear softer so that it squats?
Ive never been into drag racing, but Ive done quite a bit of work with road racing suspension, so I may be wrong about this, but I think that 'squat' is something that it to be avoided for off-the-line traction.
Im not really sure why though, haha. I know a lot more about traction once the car is moving.
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Old 09-28-2009, 03:59 PM   #6
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Wouldn't you want the suspension in the rear softer so that it squats?
You do want squat for weight transfer and to not shock the tires. The bad part about squat is that it gives us more negative camber. What happened last year (noticed it while watching video shot from the back) is that the car squatted then when it rebounded the tires spun. Could be that boost hit at this point too or a combination of both.

The OTS Koni's are rebound adjustable only. So I wanted them to squat then slowly rebound to keep the weight transfer as long as possible. Kind of like the 90/10 drag shocks except on the other end, backwards and not as good!

I was going to set the camber and toes to zero but I had autox the next day.

Quote:
Originally Posted by sixshooter View Post
dvcn,
I know you run WI, but what are you using for engine management? Are you still on stock internals?

I can't wait to see the video.

Good job.
Engine management is the ultra lame Wolf 3DV4. It has an internal MAP sensor that is going bad. I've been too lazy to wire up the external GM 3 bar in its place. It's on of the reasons why I held back from turning up the boost and doing more runs.

Yup, same '96 stock motor with 203k miles on it. It does burn some oil but adding in some 15-50 really slows down the consumption.

Fuel and timing are very conservative. I probably wouldn't knock w/o the WI. It is just insurance and to keep the carbon from coming back. I was overly rich on the fuel, 11.2-11.3 almost all the way down the track.

I can't wait to see the video too!
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Old 09-30-2009, 09:10 AM   #7
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Camera angle 1. They missed the burnout, makes me sad. To be fair, the GSXR-750 was late on the lights, had a bad 60′ and let off around the 1,000′ mark. Still, it was fun and makes for a great video!

I hope the burnout video shows up someday.





Timeslip:
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They were running a .400 pro tree that night.
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Old 09-30-2009, 11:02 AM   #8
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nice run man
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Old 09-30-2009, 11:31 AM   #9
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Squat is bad, when your car squats its because you are transferring torque into your suspension causing it to compress. when the rear lifts it is actually the tires pushing into the ground.
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Old 09-30-2009, 12:07 PM   #10
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Nice, Lev should bet some tips from you
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Old 09-30-2009, 02:42 PM   #11
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Great run, your 60' time is great and judging by the video, it pulled hard all the way through.
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Old 09-30-2009, 03:03 PM   #12
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Ryan and I were standing behind Craig's car in the staging area on this run; he did a great job. The burnout was also very cool

Craig's level of performance on his 'low budget' kit is very commendable, and inspirational.
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Old 09-30-2009, 04:34 PM   #13
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Quote:
Originally Posted by Gotpsi? View Post
Squat is bad, when your car squats its because you are transferring torque into your suspension causing it to compress. when the rear lifts it is actually the tires pushing into the ground.
It's not so much that squat is good but that it is going to happen if you have a vehicle with a suspension.

I agree with you but what goes up must come down. After the midpoint of the rebound cycle there will be less force on the tires, reducing the amount of traction. This effect would be worst on an underdamped system (rear shocks set on soft). That's why I was going for overdamped (rear shocks on hard). Just trying to make transients happen slow enough to be insignificant.

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.....is very commendable, and inspirational.
and so far..... LUCKY!
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Old 09-30-2009, 05:56 PM   #14
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The problem with independent rear suspension (IRS) cars in drag racing, is that there is a pause between the time you dump the clutch, and the time the car moves forward. There is a lot of suspension travel in IRS cars, and it takes more time for the car to travel downward (squat). Once the car stops moving downward, than the car will start to move forward. During this downward movement, the clock is ticking away.

Ever notice that straight axle cars have a quicker ETs than IRS cars (assuming they both have the same power to weight ratio and or similar trap speed) Straight axle cars do not loose that time squating.

There are other problems with IRS cars when it comes to drag racing, but they can be improved with the right set up.
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Old 09-30-2009, 07:51 PM   #15
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that's a great 60ft! i don't see anything wrong with a china charger. i know of and have or have had many cars with them. used in drag,road,drift, and street use. all have lasted many years. the cars that are still around have had them for over 3 years now, and still running strong. we have a crx demo car for our shop on a china charger running 12.1 @113mph on 9 psi. gonna be at SAR soon to see what it does at 15-18 psi! my personal galant vr4 has one too. after my turbonetics turbo's seals went out, i figured, what the hell, if it lasts a year at the price i paid, it was worth it. that was back in 2005! i've run 26psi on race gas and daily drove it @ 18psi on pump.
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Old 09-30-2009, 07:52 PM   #16
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Quote:
Originally Posted by miata2fast View Post
The problem with independent rear suspension (IRS) cars in drag racing, is that there is a pause between the time you dump the clutch, and the time the car moves forward. There is a lot of suspension travel in IRS cars, and it takes more time for the car to travel downward (squat). Once the car stops moving downward, than the car will start to move forward. During this downward movement, the clock is ticking away.

Ever notice that straight axle cars have a quicker ETs than IRS cars (assuming they both have the same power to weight ratio and or similar trap speed) Straight axle cars do not loose that time squating.

There are other problems with IRS cars when it comes to drag racing, but they can be improved with the right set up.

Agreed that IRS isn't the way to go for drag and that there are a lot of dynamics going on. Straight axle cars do squat too though. Was just trying to make an excuse for running the shocks on stiff instead of soft. If possible, I'll set the camber to zero next time.

(for people who haven't been down the 1/4) I never drop the clutch. It's bad for a lot of reasons. Shocking the driveline is hard on parts and is more likely to spin the tires. After staging I'll let the clutch out until it barely engages to take the slack out of the driveline. Then I'll push the clutch in just a bit. Having the clutch pedal just below the engagement point keeps pedal speed down and reaction times more consistent. On the launch I slip the clutch for about 10'. Reduces the chance of bog, doesn't shock the tires and doesn't hurt the driveline.

If you are trying to get a good ET shallow stage and don't worry about reaction time.
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Old 09-30-2009, 07:58 PM   #17
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Originally Posted by spoolin2bars View Post
that's a great 60ft! i don't see anything wrong with a china charger. i know of and have or have had many cars with them. used in drag,road,drift, and street use. all have lasted many years. the cars that are still around have had them for over 3 years now, and still running strong. we have a crx demo car for our shop on a china charger running 12.1 @113mph on 9 psi. gonna be at SAR soon to see what it does at 15-18 psi! my personal galant vr4 has one too. after my turbonetics turbo's seals went out, i figured, what the hell, if it lasts a year at the price i paid, it was worth it. that was back in 2005! i've run 26psi on race gas and daily drove it @ 18psi on pump.
What shop?

A friend is bring out his 550awhp Evo out to SAR next week, might go watch him run. I'm not going to run again until I install the new MAP sensor and can turn up the boost and tune it more aggressively.
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Old 10-01-2009, 03:29 AM   #18
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it's a car audio shop called competition sound in corpus christi tx. we sell performance parts and accessories also though. it's good for me, i get a deal on any parts i need, plus i get to drive the crx at drag and road racing events, and occasionally, i do a few auto-x too. it's a fun car, it only weighs 1950lbs. and made 238whp @ 9psi. and hopefully close to 300 at 15-18psi. we'll dyno it soon. for road course events 7-9psi is plenty though.
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Old 10-01-2009, 09:43 AM   #19
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Quote:
Originally Posted by dvcn View Post
Agreed that IRS isn't the way to go for drag and that there are a lot of dynamics going on. Straight axle cars do squat too though. Was just trying to make an excuse for running the shocks on stiff instead of soft. If possible, I'll set the camber to zero next time.

(for people who haven't been down the 1/4) I never drop the clutch. It's bad for a lot of reasons. Shocking the driveline is hard on parts and is more likely to spin the tires. After staging I'll let the clutch out until it barely engages to take the slack out of the driveline. Then I'll push the clutch in just a bit. Having the clutch pedal just below the engagement point keeps pedal speed down and reaction times more consistent. On the launch I slip the clutch for about 10'. Reduces the chance of bog, doesn't shock the tires and doesn't hurt the driveline.

If you are trying to get a good ET shallow stage and don't worry about reaction time.


I would agree that setting the rear shocks to a harder setting would be the way to go. Can't prove it though, because my shocks are not adjustable. I have adjusted my front and rear wheels to point as straight as possible and gained considerable mile per hour at the trap. It was the final adjustment to put my normally aspirated car in the 13s. Try it, I think you will be pleased with the results.

Sure straight axle cars squat, but the squating distance and time is shorter than an IRS.

I do have a question. What spring rates do you have on the rear? I always thought that having a higher spring rate would correct the problem of excessive squating.
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Old 10-01-2009, 10:08 AM   #20
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Quote:
Originally Posted by miata2fast View Post
I would agree that setting the rear shocks to a harder setting would be the way to go. Can't prove it though, because my shocks are not adjustable. I have adjusted my front and rear wheels to point as straight as possible and gained considerable mile per hour at the trap. It was the final adjustment to put my normally aspirated car in the 13s. Try it, I think you will be pleased with the results.

Sure straight axle cars squat, but the squating distance and time is shorter than an IRS.

I do have a question. What spring rates do you have on the rear? I always thought that having a higher spring rate would correct the problem of excessive squating.
I didn't think it would do enough to go through the hassle of changing the alignment. What was your toe/camber settings before and after and how much of a difference in traction, ET and mph did it make? Did you just set the toes to zero and the static rear camber as close to zero as possible? I will definitely do it next time.

Spring rate? Having a highly developed SSM car I have stock springs in the back with NB top hats. I forgot about those. Part of the reason for previous traction problems may have been from hitting the NA bump stops.
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