8 second OEM 4 link drag race chassis setup

[Alky V6]

Changes for next time out.
Front end rebound travel limiters shaved 1/4".
Larger ID main CO2 feed line to boost control solenoids.
Nitrous shut off delay after transbrake release changed from 0.0 sec to .500 sec.
GPO1 nitrous activation window upper limits stepped up from 5600rpm/160kPa to 5700rpm/170kPa.
New ignition timing table.
Engine idle changed from 1,100 rpm to 1,350 rpm. An attempt to raise staging lane engine temp and engine temp at initial nitrous activation.
New boost control curve. BOV clamped shut for the launch. Wastegate launch setting increased 1 psi. Much more aggressive boost rise after the 1-2 shift. Checking upper boost limit fueling. Tire slippage is expected. Be prepared. Clean underwear with no holes.

 

[Alky V6]

I tried the unthinkable. I took the car to Qualcomm stadium for some 1/8 mile night and dewy drag racing. The stadium is basically a section of the parking lot used for street car drag racing and has always been like ice skating for me in the past, so I de-tuned the car expecting the worst. Nines had been the quickest for me in the past due to traction issues.
There was a lot of moisture in the air. Dew settling on all the cars, frosting the rear window, and my breath fogging up my glasses with my helmet and neck brace on. Pretty hairy trying to defrost your glasses while waiting for the tree to come down. After a few passes and more de-tuning, I was able to punch out a 6.55 et. The car handled great.
They had put down some VHT for the night, but I don't think it took very well. The 60 foot was the main problem for everyone that night. A lot of cars spinning at the launch.

 

[Squid4life]

Agreed, once you detuned it a bit, the car flew! What did you end up turning the boost down to? I have some vids, trying to create a youtube acct and upload them right now. Will post the link in the SW QC thread.

 

[Alky V6]

Agreed, once you detuned it a bit, the car flew! What did you end up turning the boost down to? I have some vids, trying to create a youtube acct and upload them right now. Will post the link in the SW QC thread.

Cool.
The 6.55 run was using a straight 15-16 psi boost through the whole run. The launch still could have used a little more de-tuning, but luckily on that pass, she hooked well enough.

 

[Alky V6]

After the experience at the stadium, I have the feeling that I would have benefited greatly had I been able to adjust the front end extension travel limiter.
I'm going to work on a system that will allow me quicker adjustment of the front end extension travel limit.

 

[Alky V6]

Here is the track pic that I was referring to earlier. Once I got the picture in my hands, I could see that it appears the rearend lift/squat is neutral and body roll appears to be nil. Exactly what I was aiming for.

 

[Alky V6]

The increased ID CO2 feed line to the boost control solenoids did help the reaction time of the wastegate control. Not all the lines were increased in size. Only the main feed line from the CO2 bottle up to the control solenoids. From there the lines tee off into a smaller ID line size. Judging by how the actual datalog of the control pressure curve looks compared to the input boost control curve, I can't imagine the reaction being any better. The step ups in control pressure viewed in the captured datalog have become very pronounced with the better reaction to the increased feed line ID size.
The regulated CO2 pressure feeding the solenoids has been 100 psi in the past. I tried shimming up the regulator to give 125 psi feed pressure and it appeared to be too much. The pressure targets in the input boost control curve were being overshot. Went back to 100 psi, and the targets were much closer to being hit when commanded.
Something I've recently learned with this boost controller (AMS1000). Let's say you want a large WG boost control pressure drop to occur for the 1-2 shift at 2.2 seconds into the timeline of the run. You would think that you simply need to input the pressure drop to occur at 2.2 seconds in the control curve input table. It's not that easy, unfortunately. If you perform a dry run of the control pressure curve and study the datalog, you will find that the actual recorded control pressure curve may not exactly match your input control pressure curve timeline.
What you need to do is fudge the timeline numbers, and the other numbers for that matter, a little until the recorded datalog of the control pressure curve more closely matches your intended control pressure curve target. Then, you will need to match that control pressure curve to an actual test run with the car to see if the overall control pressure curve is giving you the intended performance target on the track. A lot of grey area to work around with this boost controller. Not a cut and dry deal at all. Once you've realized the required fudge factor, the procedure for producing a good boost control pressure curve becomes less aggravating.

 

[charlief1]

Waiting on the vid Donnie. Looks like you've got it pretty much nailed down now.

 

[Alky V6]

Waiting on the vid Donnie. Looks like you've got it pretty much nailed down now.

I'm going to try to get my son down to the track this weekend to take one.

 

[Alky V6]

I'm going to shave another 1/4" off the front suspension rebound travel limiters. I think I've figured out a system to make the limiters adjustable. Not as simple as a long bolt and locknut welded to the upper A arm, but it should get the job done. And easier to fab up. It only takes drilling one 5/16" hole in the frame to mount the travel limiter, as far as modification to the chassis goes.

 

[Squid4life]

I'm going to try to get my son down to the track this weekend to take one.

I plan on being there as well, with video cam in hand too. How close will they let someone get to your car when staged? I ASSume since your name is on a sign there, they wouldn't have much beef standing ~8-10 ft behind and slightly to the side of your car when staged? If your son is videoing as well, maybe we can figure out two places to get multiple views. Should be interesting.

 

[Alky V6]

I plan on being there as well, with video cam in hand too. How close will they let someone get to your car when staged? I ASSume since your name is on a sign there, they wouldn't have much beef standing ~8-10 ft behind and slightly to the side of your car when staged? If your son is videoing as well, maybe we can figure out two places to get multiple views. Should be interesting.

You'll need to go up to the tower and sign a media waver. If they ask, tell them you're the photographer in my pit crew. It won't be a problem being behind the car after the burnout. The angle you mention sounds good. Try to get lower than the above pic so that both front wheels can be caught in the video.
We're going to try out a drag style rear wing this weekend that I'm borrowing from Squid4life, too.

Sounds like fun. Hope you can make it, James.

 

[Alky V6]

I went ahead and cut an additional 5/8" off the front end travel limiters for a total of 7/8" removed. Each limiter will use a shim pack of 3 - 1/4" and 1 - 1/8" spacers to change the amount of front end rebound travel.
The limiters can be removed all together to provide a stock amount of front end rebound travel, or the limiters can be installed with any combination of the shims to give different levels of front end rebound travel.
All that's left to do is fab up the eight 2" x 2" aluminum shims and drill a pair of simple 1/4" holes through each shim that will be used to retain them in the travel limiters.
I can even fab up a couple of 1/16" shims, if I find that level of fine adjustment to the front end rebound travel is necessary.
The travel limiters are retained to the chassis by one 5/16" nut and bolt.

 

[charlief1]

If you get your boy there as well one of them needs to be directly to the side of the launch Donnie. That will give you 2 sperate views so you can see if everything is working right.

 

[Alky V6]

If you get your boy there as well one of them needs to be directly to the side of the launch Donnie. That will give you 2 sperate views so you can see if everything is working right.

Good point, Charlie. If we have two cameras there, I'll make sure we cover that. Thanks.

 

[Alky V6]

The travel limiters measure 15/16" high on the left and 1.250" high on the right without any shims installed. The shim packs for each side total 7/8" high.
For this coming TnT, the limiters were installed with no shims. This should give me about 2+ more inches of rebound travel on each side.
I took out the 1/6 turn preload I had on the ARB. The ARB now has zero preload.

 

[Alky V6]

Note.
If the car still has the tendency to steer left with the ARB at zero preload, start to slowly take away weight jacking from the left front and right rear corners.

 

[Alky V6]

Made a lot of changes today to the chassis setup. Want to put them down for the record.
The right front rebound travel limiter was shaved .100". This will mean less offset as far as when the right side will run out of travel compared to the left side when the front end lifts. The thinking is, if the right side tops out too far before the left side, it could mean more weight put on the right rear tire, steering the car to the left.
The RR spring spacer was changed in height from .800" to .400". The available spacers for the RR spring are now three separate spacers that each measure .200" thick. Each spacer should equal a spring preload of 25 lbs. The reason for changing the corner weight spring preloads is because of the stadium races. With the limited traction, the car wanted to steer left. The change I made to the dynamic gain rate of the IC may be putting more weight on the RR tire. Taking some weight off the RR spring preload is an attempt to counter the higher dynamic gain rate of the IC.
The front spring was lowered on the shock body 1/2 turn of the spring seat to go along with taking the weight off the RR corner.
The rear fender lip heights with driver in the car measure even. The RR spring height measures .250" shorter (not including spacer height) loaded than the LR spring, with driver. That would be about 31 lbs. of spring preload on the RR corner (125 lb/in rate springs).
The ARB is neutral with driver for now.

 

[Alky V6]

Important! Check tire pressures before measuring chassis. Doh!
All w/driver.
Loaded rear spring heights: LR 10 1/16", RR 9 3/4". The difference in rear spring height is 5/16" (.3125"). Rear spacer height is .400". Spring preload on RR, 39 lbs.
Corner fender heights are;
RR 29"
LR 29"
LF 26 1/4"
RF 26 1/8"
ARB neutral.

 

[Alky V6]

I didn't get a chance to try the wing yet. On take off, the car was moving left while in the air. That needed to be corrected first. I pulled the two preload shims at the RR corner, took about two turns out of the ARB, and the launch straightened out. The new static/dynamic IC offset was having quite an effect. I'll have to weigh the car and check heights when I get the car back to the shop. I'm getting the impression that the new IC settings have done away with the need for as much RR corner preload, if not done away with the need altogether.
On one launch, I got some tire chatter. The car stayed straight, just had some chatter. The next run, I increased the launch boost by one psi and the chatter was gone. Could of just been a fluke that I got chatter on that one run.
An interesting thing happened today. In the past, before I started playing around with the suspension settings, the car would roll down the staging lanes on its own. The staging lanes have a slight downhill grade to the front of the lanes. That makes it nice moving up the lanes without having to start the engine. Just let off the brakes and the car begins to roll downhill. After I started working on the chassis, adding preload to the RR, the car stopped rolling down the staging lanes on its own. Well, today, after removing the preload shims from the RR corner, the car has started rolling down the staging lanes on its own, again. The chassis seems happier without the preload.

I'll be installing the wing at the shop for the next TnT in two weeks.