209 replies to this topic

[CSPCRX]

since this is a group of racers trying to pick a TBar size for the front. I am running 27.5s now and its not enough for my b16 powered CRX. I have 500lb rear springs.

 

trying to decide on 31mm or 29mm. thoughts or feedback?

[gtpilot]

What's the intended application?  Street?  AutoX?  Track duty?  If it is not going to be for the street I would opt for the 31mm...be prepared to get some stiffer springs for the rear too - 

[CSPCRX]

I run time attack NASA events. This is why I noticed the 27.5s are too soft and also raised the rear spring rate. I switched to 500lb rears and have Koni typeR race shocks in the rear.

 

I already have double adjustable shortened revalved Koni fronts so they should have no trouble handling the larger bars.

[gtpilot]

We ran the 31mm fronts, with two front sway bars...900 lb rear springs with a really beefy custom cockpit adjustable rear bar when we road raced with the torsion bar setup.  YMMV.

[CSPCRX]

My car was originally setup for autox and the belief back then was softer was better so my front bar is a dx, which I believe is the smallest.

 

sounds like 31s would be perfect than. thanks. Now just need to find them.

[Andy69]

I just got back from vacation, so a late post about the June 24th SCCA autocross at the coliseum

 

I was 1st in PAX after the morning run group.  I was significantly faster in the PM group but I didn't have a clean run, so I finished 5th.  This is the 3rd event in a row where my fastest morning run was my fastest of the day due to hitting cones.  My fastest coned run would have put me in first by a second.

 

I'm pushing the car hard, especially in the slaloms, and  that's where I am running into trouble.  I had one shining moment in Grenada this spring where I was able to get the back end to rotate very quickly [kind of like a "waggle", like you see in the 2001 videos of Bret Norgaard on You Tube) AND I could keep the steering up which resulted in a very speedy slalom (as proven by data analysis), but I have not been able to duplicate it since.  

 

I'm close, very close, to a breakthrough in speed that will put me in front of most if not all the other regular mid south drivers.  The limiting factor right now is the steering, which I think is a combination of it being slow and my brain being slow - I am definitely NOT overdriving the car.  I'm not spinning or losing control because the tires are losing grip - it's because I cannot steer the car fast enough. I need to invest some tire in fun runs to test some techniques and iron things out, because I know there is a way through a slalom in this car at these speeds.  That and some small suspension adjustments, as I think the removal of weight last year created a tendency for the car to push slightly, so I need to up the rear spring rate by 50 lbs or so.

Edited by Andy69, 22 July 2018 - 12:39 PM.

[Andy69]

AutoX at the coliseum today.  I was 10th after the 3rd run group and managed to move up to 4th over all.  I ended up beating a top 3 nationals driver in PAX.  I was running up on the sidewalls, which means I'm faster.

 

Now the bad news: I don't like the HF transmission. I put it in for the taller 2nd gear, but it's too tall.  Granted, this was a tight course, so I;m going to wait until Blytheville in two weeks to make a decision.

[Andy69]

Summer is getting fun.  This coming weekend is the ARSCCA event at Blytheville, which is always fun, and then the following Saturday is Mid South event 4 at the Liberty Bowl, Sunday is Hub City Speed at the Jackson TN dragway.

 

I'll try to get some videos.  I backed off on the analysis and data collection while I was trying to get the car sorted out.

[Andy69]

Holy mackerel! Last weekend was fun. Long, but fun. Blytheville is an hour and a half drive from Memphis and the event usually attracts all the drivers from Arkansas Region who are going to nationals as one last tune up event. Lots of very good competition.

I was 24th of 48 Saturday and 14 of 44 Sunday. Sunday’s event I consider particularly successful, since I was right up there at the tail end of the “good” drivers.

I also learned I’m not using enough air in my A7s. Last weekend at the Liberty Bowl I was up on the sidewalks, so I upped the air pressure by 5 psi in each tire for the morning on Saturday, then by another 3 for the afternoon. I was considerably faster. I left it at the same air pressure for Sunday but I think I could have moved up another 2 psi. That sounds weird I know, moving up 10 psi, especially when I’ve been competitive locally, but I think it has a lot to do with the concrete surface at the Aeroplex vs asphalt at Liberty. I attribute some of it to being faster, too.

On to the interesting stuff. This new transmission is rubbish. The gears are way too tall. Even on a wide open course like Blytheville I can’t get into a useful rpm in second. But one positive came out of it - I made a concerted effort to not slow down so I could keep the rpm up as high as possible. Due to the nature of the gear ratios, downshifting into first is not happening, so it was second all the way. I think it made me way faster. Here’s a snapshot of Track Addict from Saturday showing 1.49Gs. Sunday I had a 1.56G



Looks like the car is getting good traction. It pushes at the limit still, so another spring change in the rear is in order.

Best run Sunday:
Edit: have to wait with the video


Sent from my iPhone using Tapatalk

[gtpilot]

Is that the Pro version of TrackAddict?  Oddly, I just downloaded the free version today to play with...

[Andy69]

Is that the Pro version of TrackAddict?  Oddly, I just downloaded the free version today to play with...

I figured I could spring for the $9 pro version :-)

It’s extremely useful. I can do side by side analysis of runs while in grid or between run groups and see where I lost time.


Sent from my iPhone using Tapatalk

Edited by Andy69, 14 August 2018 - 06:19 PM.

[gtpilot]

I figured I could spring for the $9 pro version :-)

It’s extremely useful. I can do side by side analysis of runs while in grid or between run groups and see where I lost time.


Sent from my iPhone using Tapatalk

 

Cool - do you use an iPhone for the platform?  I am limited to Android...do you have an external hi res GPS?

[Andy69]

 

I figured I could spring for the $9 pro version :-)

It’s extremely useful. I can do side by side analysis of runs while in grid or between run groups and see where I lost time.


Sent from my iPhone using Tapatalk

 

Cool - do you use an iPhone for the platform?  I am limited to Android...do you have an external hi res GPS?

 

 

I use a Dual WAAS-enabled 10hz bluetooth GPS.  The WAAS standard calls for 7.5m accuracy but practical application is on a par with differential GPS, which is 1m.  What makes it great is it's smaller than my phone and sits on the dash.  DGPS would require a mounted receiver and an antenna.  Anyway, it's significantly better than the built in GPS - 10 readings per second vs 1 for the phone, and it's substantially more accurate - submeter vs 30m.  Simply put, the data quality you need for the most basic analysis really isn't there without this part.

 

I was using my old iPhone 4 but it won't work with the GPS so I use my iPhone 6.  I don't even have a mount - I just duct tape it to the rearview mirror.  It has enough adjustment range that I can point the phone any direction out the windshield.

 

Total cost including the phone was $750, but I had the phone anyway, so it's actually around $150.  The ability to do a side by side comparison of runs I just completed while I'm sitting in the car in grid makes it totally worth it.

 

Trackaddict can also control other bluetooth sensors or sensor groups, plus I think up to 4 GoPro cameras, and you can connect a cable to your OBD2 or install a bluetooth transmitter on the OBD2.

 

The downsides are that the built in iPhone sensors are not as accurate as external sensors will be. I think that 1.56G reading I got on Sunday represents a one-time reading.  You'd need to run a Kalman filter on the data to clean it up but even that isn't as accurate as a good quality sensor.  It does give you an idea though and you are able to tell the difference between a car that does 1.2G and one that does 1.5G.

 

It also only works with GoPro cameras, so the $40 Ebay action cameras are out and you need to spend $400.  This sucks because I REALLY need to have cameras down the sides of the car to gauge cone distance.

 

The other big downside is that the CRX does not have OBDII, meaning if you want that extra data you have to add the sensors.

Edited by Andy69, 15 August 2018 - 08:49 AM.

[Andy69]

2nd overall today.

I’ll post some videos soon. I just can’t post them from my phone.

Using the TrackAddict software to analyze my morning runs at the break is paying huge dividends. I was able to determine where I was losing time and adjust my afternoon runs accordingly, and I ended up slashing 1.4 seconds off and I moved from 7th to 2nd overall.


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[Andy69]

I went over to Jackson, TN, for the Hub City Speed event at the Jackson Dragway.

 

There were about 25 participants.  I was 5th overall and 1st in Super Unlimited.  It was a very fast course, which put me at a disadvantage to the faster cars.  The overall winner was a novice with a ZL1 Camaro.  He reached 120 mph on the big straight, where I could only manage 75.  Can't compete with that.