I have a GTECH competition pro and cannot get a good RPM reading in the Vette. I had minor problems getting the S2000 to work but it did work consistantly. The Vette can't get a reading even with the everything in the vette turned on I can't get the RPM to read.

For those that don't have a gtech, they read RPM through the cigarette lighter and use that in caculating things.

Anyone one else with a GTECH that's had this problem and solved it in a new C6?

Thanks,

-mikey

 

It must try to read alternator whine in order to determine RPM. In the C6 a new type of alternator is used. The ECM directly controls the alternator output through high frequency pulse width modulation. So I don't think the GTECH will get a signal it can understand.

 

I have a G-Tech Pro Comp. that's about 1 year old, it reads the RPM's fine. I set it up per the manual from G-Tech using their calibration for the RPM function.

Try the calibration per the manual.

 

I agree, although my g-tech is over one year old and was recently firmware upgrded. Used it successfully at Lone Star Corvette Weekend.

 

I have the Gtech pro comp too. I set the RPMs per the manual and cannot get a good RPM reading with the Corvette either. Much like you I had an S2000 and it always worked perfectly in that car...

 

Thanks for the help, I've actually called Gtech. It's a tough issue with no clear answer. They say wiring directly to the battery may help. The new firmware is on mine as well. It helped many people but hurt others. It has a new sensing algorythm that won't work for everyone. Aparently it will never work for everyone so it's jsut a trial and error thing. They say every car is unique. It helps to have very good wiring. It helps to have direct wiring, for a stronger signal.

Now here's what their forum says.

It is going to need the alternator working. If the battery is fully charged you may not get a signal from the alternator. That is why they say use the air and the lights and turn everything on. A great tip I have yet to try is to run those things without the engine for 3 min or so the run down the battery for a few minutes. Then when you start the car and calibrate and use the gtech you may not need to have anything extra on. I will try this today on my way to work.

Lots on the forum had better luck with the old firmware, me included. Though I did get the s2000 reasonably consistant with the new firmware. On the forum there is a link to beta firmware that is a tweak on the new firmware that is suposed to help some. You can move back and forth between firmware with no issues. Only thing I don't know is if you need the old PASS software if you do or can all the firmware work with PASS 2.0??

I'll be checking that stuff out if I get a good signal today. If I don't get a good signal today with 4.01 I'll update to 4.1 beta. If no good there I will try firmare 3.0.

Thanks all....

P.S. For those that have it functional:

What HP/TQ are you getting at the rear wheels with drag and everything added in?

What weight are you using with full fuel load and youself subtracted for a pretty empty car?

 

I can answer your last question; My car (6spd,Z51,all options) on certified scales weighs 3251# w/1/4 tank of gas and some tools and such, I add my body weight and any gas in excess of 1/4 tank to get the weight to enter for the horsepower function. To get a reasonable HP figure you have to use the weight as tested, not empty weight.

 

AWESOME, much appreciated. I'll base my weight on that and I'll make a chart for empty to full. I've found that the guage full to empty is only calculating on 16gal keeping 2 in reserve past empty for 18 total gallons. I'll calculate empty weight to be 3251 - 1/4 16gallons and figure out what each .1 amount of that 16 gallons is to get to full so I can easily gtech with any load of fuel. I have some tools and such too so that should be close for me. I'll get weighed when I get a chance.

Thanks again.
-mikey

 

I've been guesstimating gas at 6# a gallon with a full tank @ 108#'s, 3/4 @ 84#'s, 1/2 @ 60's and 1/4 @ 36#'s.

BTW; My DIC "average fuel mileage" is pessimistic, I end up with around 1MPG better than it's estimate.

 

Well today the Gtech RPM worked fine!!

All I did was run the lights and airconditioner and seat heaters for a few minutes before calibration.
Then I did a 1/2 hour road race drive to test it out. The RPM worked nicely.

I'll to some testing next week.
-mikey

 

Okay so it's not working perfectly fine.
Today I tried it again in road race mode driving around and when I downloaded I noticed the same spikes I got earlier.
The RPM drops ocationally for a fraction of a second it loses the signal here and there.

So that was with 4.01 firmware, tonight I downloaded the beta 4.1 firmware into the unit and I will try that on the way to work tomorrow. After work I will do a few HP runs in first and then also in second gear to see how 4.1 works. I'll post the results on firmware 4.1 soon.

-mikey

 

Remember that the ECM is the regulator in the C6. It shuts down the alternator in certain situations, when the battery is at full charge, when high output is demanded from the engine, and probably at a number of other times too.

 

Thats not the problem here, I had teh lights and air on a few min prior to starting up and ran them the entire trip.
It doesn't cut off completely. It just has drop outs for 1 sample here and there. That's 1/20 second.

-mikey

 

Did the 4.1 firmware help with your issues?

A buddy and I went out and did some g-tech runs this
weekend (C6 Z51 MN6 1SA). The g-tech was able to
pickup RPMs OK during calibration and general driving
around. However, we'd do a run and the HP/TQ results
would look way off.

After experimentation, we noticed the RPM reading
was fine until heavy acceleration. Under heavy
acceleration, the RPMs would jump down to 1000
or so several times per second.

Haven't yet tried the trick of turning on headlights to
load the alternator. We will give that a shot and see
what happens.

We used a g-tech pro competition with 4.0.1 firmware.

-Rahul

 

What is the weight of unleaded Gasoline?

Depends on the API gravity of the gasoline, which varies by grade and refinery. Usually, regular unleaded gasoline has a gravity of around 58 and a weight per gallon of 6.216 pounds per gallon. Premium gasoline may have a gravity of 54, or 6.350 pounds per gallon.

The internet is a wonderful thing

 

Well I've been working with tech support and I've tried:

4.01
4.1 beta
and now I'm back to 3.0

3.0's RPM is solid

I had the same problem as you, that RPM looked fine until you were doing a run and then you'd get drops in RPM signal throught the run here and there.

3.0 works perfectly. The problem with 3.0 is that you lose the Road Race ability and some features such as angle compensation where you set your cars tilt angle which defaults to .2 deg.

So 4.1 and 4.01 would be more accurate but they RPM is porked.

Long story short is that I'm using 3.0 right now and it works much better for HP testing and Drag runs but you lose a teeny bit of accuracy and you totally lose road racing recording.

If you want RR you can always go back to 4.1 for those days.

Until a new firmware comes out 3.0 works best for me.

By the way the Gtech seems to show lower numbers than I'd expect.

I did weight very similarly to the above person who used Gtech and got results like this:

HP280
TQ290

400 at crank
/ 1.15 = 347 rwhp
347/280=1.239

Could rolling resistance and drag account for 24% of RWHP usage to 110MPH?

If so then 280HP is reasonable for 3rd gear at those speeds.

Drag with our car doesn't use very much HP at those speeds. So it seems that rolling resistance is using lots of HP. Anyone know of a way to calculate rolling resistance seperate from drag?

What do you guys get with your gtech?

-mikey

 

I don't understand your results. Are you saying that 3rd
gear runs show 280 rwhp?

Why don't you take the data in 2nd gear? That way you
remove most of the power loss due to drag, at least as
compared to a 3rd gear run.

Can't you take a single run including 1st, 2nd, and 3rd
and look at data/results for each gear? A 1st gear run
would show very little loss due to drag, probably less than
10hp.

Pat

 

It was my understanding that drag is a variable that increases with vehicle speed and that horespower at a given engine speed is fixed.

Adding HP will give you more speed by overcoming drag with power but adding drag will not decrease HP, only speed.

 

Cool. That is very useful info. I'll revert back to 3.0
and will give that a shot hopefully this weekend.

Like you, turning on headlights did not help.
Nor did recalibrating at various different RPMs.

Sounds reasonable to me. Way I look at it, rolling resistance +
drag must equal 100% of RWHP at 186MPH. So it is quite credible
they'd be 24% at around 100MPH. See below for more scientific
answer.

So at 6000 RPM (peak HP) in 3rd gear you'd be going around
90-95MPH. At that speed my car simulator software shows the
C6 has 40HP lost to drag, about 10HP to rolling resistance, and
about 70HP to the transmission/drivetrain. Total loss =
120MPH, so total realized HP = 280HP. Looks like your g-tech
results are spot on!!

I'd agree with catpat8000 though. You should do you HP/TQ
runs in lower gear. If you run in 2nd gear, your 6000RPM
HP peak will come around 65MPH. At that speed, the simulator
graphs look like wind drag = 10HP and rolling resistance = 5HP.
Only 15HP (approx) off from your RWHP.

Our RPMs were too garbled for the poor g-tech to reach
any sensible conclusions. I think one run it said 340HP,
and another one it said 48.

-Rahul

 

firmware3.0
1-4th run
248 in 1st 6180
280 in 2nd 5850
279 in 3rd 5420

2nd gear only run
271 in 2nd 5760

1-4th
246 in 1st 5740
278 in 2nd 5920
277 in 3rd 5570

4.1beta
2nd
277 in 2nd 5500

Various runs in differant versions of firmware.
The smoothest RPM is in v3.0, it loses the pitch variable.
So if the car pitches 2.0 deg during the run that's not accounted for in v3.

Note that when running a string of gears 1st gives very low HP #'s.
2nd gives a decent # but 3rd isn't much worse than second even though your moving quite a bit faster? Some of this could be the breathing the engine does.

If you smooth out the clutch and let the car coast forward in second and then smoothly get on the gas to do just a HP run in second you'll find the numbers don't equal the 1-2-3rd gear run results. For some reason you get more out of higher speed runs and I'll be part of it is breathing but I'm not sure that's all of it.
-mikey