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Deep into the 13's

Posted: Sat Feb 18, 2012 8:12 pm
by wxo
We had a beautiful 60 degree day at Piedmont Dragway today. It's an eighth mile strip about an hour from home. Jim's strong running new motor was too much for the tires, but Smoke did quite well. My first run was the best one. I took the air pressure down to about 27 psi and staged up against a mid 90's Firebird with an LT1. I was expecting a normal countdown tree, but was greatly surprised when all the yellows lit after we staged and the Firebird was off. I followed closely behind and ran him down at the end. The following picture shows me playing catch-up. I turned an 8.786 at 83mph to his 9.133 at 79mph. The 8.786 converts to
13.75 in the quarter!! I looked up the time slips on Smoke when it was bone stock. It ran a best of 9.41 (14.70) at 76 MPH on a hot night of racing.
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I messed up and came to the track with 3/4 of a tank of gas. That's a little more than 15 gallons. I also took my laptop and logged one of my runs with HP Tuners. I ran an 8.836 (13.88) at 82MPH that time. I haven't had time yet to analyze all the data I logged, but I noticed that my maximum advance during the run was 23 degrees. I think something is pulling out timing or my tune needs to be tweaked because I understand that I should be seeing more like 28 degrees. Before you ask, I had both the traction control and Stabilitrak turned off. So, even though it was a great day at the track, it looks like there may still be a bit more to coax out of the TBSS. Who knows, a cooler day, less gas to carry, and a good tune.....

Re: 2008 Trailblazer SS

Posted: Sat Feb 18, 2012 11:03 pm
by Fred32v
Nothing like going to the strip and coming home with your best times ever.
Those are impressive numbers. That tune sure paid off.
It does look like there is more there. just for starters, 12 xtra gallons of gas is 100 lbs..
60 foot time?

Re: 2008 Trailblazer SS

Posted: Sun Feb 19, 2012 7:11 am
by wxo
60 foot times were 2.1 secs.

Re: 2008 Trailblazer SS

Posted: Mon Feb 20, 2012 7:13 am
by MostMint
You have that SS running well. Cursory check shows my SS at 9.16 in the 1/8 and 14.16 in the 1/4 with 2.1 60' times.

If you can't find the timing issue in the tune, you may want to check the logs to see if your timing is getting reduced due to the knock sensor.

Re: 2008 Trailblazer SS

Posted: Mon Feb 20, 2012 9:11 am
by wxo
I'm running with the dyno tune setup that was done before the cold air kit was installed, so the MAF table is probably not giving the ECM the correct airflow info. From what I understand, that alone can throw all the other stuff off. One of the first things I checked was the knock sensor and it is not detecting anything. I'm still studying the logs and the books and the forums, but getting a handle on all this is slow going. I should really just take it to the dyno and get the tune tweaked, but I would like to understand more before I do it. There is a right way and a wrong way to approach this tuning. I don't know if I will live long enough to understand enough to start tweaking the running parameters, but it's interesting and maybe a light bulb will come on soon. In the mean time the TBSS is running better than I would ever have expected. I haven't dug out the time slips, but I seem to remember the best pass on my 2000 Vette was around a 13:50 with BP at the wheel. The TBSS is very close to that now. I really liked this vehicle when I first got it, but it just keeps getting better. :D

Re: 2008 Trailblazer SS

Posted: Mon Feb 20, 2012 10:01 am
by Maverick
I really liked this vehicle when I first got it, but it just keeps getting better.


X2!!! If its in the 13s that's huge!! One of these days we'll have to try the 1/4 mile.

To spin or not to spin? That is the question.

Posted: Tue Feb 21, 2012 8:29 pm
by wxo
I've been analyzing the ECM logs I captured at Piedmont and I verified that I'm leaving the line with no wheelspin. I could see on the burnout I did just prior to that, that the wheels were spinning at about 56 MPH. I was just wondering what the collective experience of this group has to say about leaving the line. I know everybody does it, but does spinning the wheels help you get going faster or not? :?: What say you?

Re: 2008 Trailblazer SS

Posted: Tue Feb 21, 2012 8:52 pm
by MostMint
My best 60' times are with no wheelspin. Maybe add more low end torque or raise the stall speed to get it to leave harder.

Re: 2008 Trailblazer SS

Posted: Wed Feb 22, 2012 7:25 am
by wxo
After thinking about the question for a while longer, it seems reasonable that the answer is somewhere in between. Leave harder with some spin, but not too much. Which is, I think, what Andy was trying to get across to me.

Re: 2008 Trailblazer SS

Posted: Wed Feb 22, 2012 1:26 pm
by Fred32v
Me thinks that burnout is why the SS just left, w/o a burnout the tires don't heat up and get softer.
If the traction felt marginal on my first run, I would really punish the tires next time to improve my bite.
Works every time, the better the burnout, the better the 60 foot time.

Re: 2008 Trailblazer SS

Posted: Wed Feb 22, 2012 2:08 pm
by wxo
Besides, burnouts are great fun. :mrgreen:

Re: 2008 Trailblazer SS

Posted: Wed Feb 22, 2012 3:07 pm
by Fred32v
I like 'em!


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Re: 2008 Trailblazer SS

Posted: Wed Feb 22, 2012 4:07 pm
by wxo
Was that picture before or after the rear-end bolt broke? :(

Re: 2008 Trailblazer SS

Posted: Wed Feb 22, 2012 5:59 pm
by Fred32v
Before.
Rearend support broke during the last race of the season.
I can hardly wait to do it again! :D

newest dyno pull

Posted: Wed Apr 04, 2012 8:46 pm
by wxo
Since things are a little quiet till BP gets his S/C S-10 running, I thought I'd update y'all on the latest tweaks to Smoke's computer.
Just to bring you up to date, I had installed the Cold Air Plumbing but the tune had not been updated to bring hardware and software into a working relationship. The first session on the dyno on 8/4/2011 in stock form resulted in 323 HP and 341 lbs/ft. Then I installed the CAI. The dyno session on 3/12/2012 recorded 329 HP as a base line with the CAI. The final tune brought it up to 340 HP and 354 lbs/ft. So the CAI and tune was worth about 17 HP and 12 lbs/ft.


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This was the setup I took to Benson the last time. I expected some much better times, but that didn't happen. The warmer day may have taken away some of the gain I expected. Furthermore, I logged the data on the runs at Benson and saw that I was getting some detonation and subsequent reduction in timing. I took it back to the tuner and he added a bit more fuel to the tables. I took it out again after that and logged a WOT run through the gears. The detonation was gone and all is well. I'm still not happy with my shift points and I'm working on that. The tranny doesn't want to do what I'm telling it to do via the HP Tuners. I hope I get it where I want it by 4/19 because I have another date at Benson with that pesky Maverick.