14 replies to this topic

[Tom Hampton]

Ok, so I bought a g2x from cy. It supports two tom inputs, gps data, plus 12 external analog inputs. I'm trying to decide what to do with these.
One rpm input will be engine the other wheel speed. Should I use driveshaft or lf wheel speed?

For the analog inputs i've come up with the following potential list:

Steering angle
Throttle
Brake pressure
Afr
Water temp
Oil pressure
Fuel pressure
Fuel flow
Egt
Intake air temp
tire temps

Obviously that is more than 12. Thoughts on what to throw out?

I plan to do this in stages. Driver stuff first, then setup related, then engine.

[James York]

Ok, so I bought a g2x from cy. It supports two tom inputs, gps data, plus 12 external analog inputs. I'm trying to decide what to do with these.
One rpm input will be engine the other wheel speed. Should I use driveshaft or lf wheel speed?

For the analog inputs i've come up with the following potential list:

Steering angle
Throttle
Brake pressure
Afr
Water temp
Oil pressure
Fuel pressure
Fuel flow
Egt
Intake air temp
tire temps

Obviously that is more than 12. Thoughts on what to throw out?

I plan to do this in stages. Driver stuff first, then setup related, then engine.

Each of those sensors will set you back a bit to get each signal to the G2X. Unless you know of some way other than I do, it's not cheap.

Here my thoughts:
Wheelspeed; (or drive shaft speed) forget it. GPS speed is good enough. Unless you have something different than I do under the hood, this data doesn't really provide any value.
AFR; an absolute MUST in a 1.6 for tuning as the weather/temps change
Throttle, Steering and Brake; Can be useful if you really into data analysis
FP; probably good to have to see if a lean condition is from a failing pump.
Water Temp and Oil Pressure; might be better to use a guage with a warning light to save some money.
EGT; Are you running a turbo?
Fuel flow; don't waste your time. Conservative rule of thumb, 10 mpg.
Intake air temp; besides knowing it, can you change it? why log it?
Tire temps; I have never seen this done. I don't think those little IR sensors will do much. A lot of variables, where on tire, are they moving around, etc.


On my 99 I log:
AFR, FP in addition to the data the G2X box grabs by GPS with tach hookup.

I can see:
Water Temp, Oil Pressure, IAT from other cockpit monitoring tools.

[Tom Hampton]

Thanks, James.
The trick to keeping the costs down with the G2x is to get the universal sensor module. It accepts 4 analog inputs for $200. Then use normal electric gauge senders for engine stuff, and potentiometers for measuring positions. Some creative work with Digikey and McMaster-Carr can make a lot of stuff for relatively little money. The other thing I've found is that AiM has a lot more sensors for a lot less money than RacePak does. The AiM sensors can be interfaced to the USM quite easily.

[James York]

Thanks, James.
The trick to keeping the costs down with the G2x is to get the universal sensor module. It accepts 4 analog inputs for $200. Then use normal electric gauge senders for engine stuff, and potentiometers for measuring positions. Some creative work with Digikey and McMaster-Carr can make a lot of stuff for relatively little money. The other thing I've found is that AiM has a lot more sensors for a lot less money than RacePak does. The AiM sensors can be interfaced to the USM quite easily.

There you go. Figured someone smarter than me had a way to make it all work.

[steveracer]

James is spot on, many of those sensors will just be "noise".

If you're willing to share, I'd like to see what/how you use for steering/throttle/brake inputs that's cheaper than buying the kit from Racepak.

[Tom Hampton]

Steve-

I had a nice long reply written...then my ISP trashed it. grrr....I'll post details of everything I do on my blog.

Shorter version:

STB kit from Racepak is $1400. It includes Steering, Throttle, and two brake pressures.

The universal sensor module is $200. A 1500psi brake pressure sender costs about $100. AiM makes a steering angle sensor kit for $140 (you can make one from parts for less than $100, if you are inclined). A plunger pot can be bought for $20 or so.

So replicating the kit would cost about $560. If you don't want the rear brake pressure....then its down to about $460. Roughly 1/3rd the cost of the kit.

[Tom Hampton]

The USM can interface to just about anything that puts out a proportional voltage between 0-5VDC, resistance (~10-20K), or RPM (50% duty, 5-18V) pulse trains. It can handle linear and non-linear inputs (with 32 calibration points---so called, piecewise linear approximation). So, it can handle essentially any standard electrical automotive sender, and pretty much anything else you could dream up using bits from Digikey.

In all but the most unusual of circumstances rigging your own sensor to interface with the USM is cheaper than the equivalent Racepak Module+Sensor by $100 or more each.

[forestdweller37]

Obviously that is more than 12. Thoughts on what to throw out?

I plan to do this in stages. Driver stuff first, then setup related, then engine.

I'm just an autocross DAQ hack, so take anything I write with a tablespoon of salt. If my first goal was to work on the driver, I'd go straight to the throttle sensor to work on my early throttle application and time-on-throttle.

[svvs]

What Forest Dweller said. GPS speed, RPM, a throttle position sensor, and some type of brake indicator (even if it's "on and off" wired from the brake lights) will give you a huge amount of shareable data from the driver perspective.

[NigelStu]

The tools you should really have to improve the driver:

• RPM / GPS speed
• Throttle position
• Steering angle
• Brake on/off at minimum (the switch is already there). Better idea is to collect pressure (single out of master cyl is fine)
• optional rear axle speed

I'd suggest the next step is car health (you can interpret the above data along with G data to help with setup)

• AFR
• Oil Pressure
• Water temp
• Volts

Both oil/water should be setup with warning lights on your dash for on-track use. If you're pulling this data, watch for changes that could be telling you a rebuild or part replacement is necessary. Since you're running a 1.6, use the AFR data at the track to fine tune - check it after every session.

For car set-up / extra vehicle health items:

• axle wheel speeds - one for front, one for rear. This can pinpoint weight balance issues, wheel spin and brake lock-up. Useful for brake compound selection and teaching your foot what to do at turn exit.
• Suspension pots
• Fuel Pressure
• Oil Temp
• Diff temp
• Tire temps (but to do this right, you'll be using all 12 of your inputs)

BTW - nice build blog

[Tom Hampton]

Ben-

You realize that I asked how to narrow 22 inputs down to 12...and you added 5 more to the list, right?

YOUR NOT HELPING!

Just kidding, your ordered list is in the same priority order as my own thoughts. Thanks.


PS: thanks for the compliment on the blog.

[NigelStu]

Yeah, I know... its fun to dream though!

All of the reasonably priced systems have the limitations to the number of channels - And while G2x, Traqmate, R-T DL1 and RLC are great systems, especially on a club level, they just don't have the numbers of inputs or processing power to achieve a complete set of data inputs with fine detail. You'd need to bump up to a top-end Aim, RaceLogic, Pi, R-T DL2 or similar system.


For now, you're already going to have data-overload, so prioritize on what's most important and where you can get the most benefit for $/time spent. The first 10 items in my list cover probably 95% of usable information for most club racers.


Remember - once you get baseline stuff setup, you can always swap out inputs if you are looking for specifics - say on a practice day, you could swap shock pots in place of AFR, oil P, water T and Volts (and then trust you stock gauges).

[Weekend Warrior]

When I glanced at this in the "View New Content" I thought it said "Seniors: what would you do.".... is it that time already? I haven't even received my AARP application yet?!? I am already looking for discounts....

[Tom Hampton]

When I glanced at this in the "View New Content" I thought it said "Seniors: what would you do.".... is it that time already? I haven't even received my AARP application yet?!? I am already looking for discounts....

Don't worry, the application is in the mail.

[Bench Racer]

I haven't even received my AARP application yet?!? I am already looking for discounts....

Reference, receiving the AARP application. Please request by mail including postage. Discounts are no longer provided.

Why, you ask. ALL AARP $$$ is spent on sponsorship with Jeffy. Naw, the other Jeffy in NASCAR.