crazy4c4

hey guys I know that the g tech isnt all that accurate but it is how I measure my mods so here goes... I have a 94 auto with x pipe removed cats, tune, and all the little cheap bolt ons. I ran the car on the same road in the same weather conditions 40-44 deg. outside. With aftermarket aero turbine mufflers the car ran a 14.1
with aero mufflers and the ltx pipe 13.7

here is the strange part. I put stock mufflers back on to make it quiet and went out and ran it today...

with stock mufflers and x pipe 13.3 and 13.02

why is it that with the stock muffs the car ran incredibly faster? I mean with slicks I could be in the 12's! thanks!

Nathan Plemons

You really need to take it to the track or dyno it. There are entirely too many variables for gtech to be accurate enough for such comparisons.

Aardwolf

I had a G-tech that I got free from some tire deal, I thought it was so inaccurate I threw it away.

65Z01

How did the air temp, humidity, baro compare with the prior run?

Are you able to get a repeatable launch?

With the increased air flow had you increased fuel flow to match?

Do you have stock maniflods or LT headers?

crazy4c4

ok lets try to answer all of the questions... I have been told both ways on the g tech, I think it is somewhat accurate (within a few tenths) humidity and temp were about the same, 40-44 deg. so only about a 4 degree variance, I have stock manifolds, I had the comp flashed by pcmforless.com in order to accomodate the increased air flow and I think I got the launch down considering the first launch the car was in OD b/c I am an idiot lol

65Z01

So, assuming the baro was not wildly higher on the 2nd trial I would suspect that the stock manifolds need a little more back pressure, which would not be needed with FL headers.

Nathan Plemons

You can't launch the car in overdrive unless you have a full manual valve body or your transmission isn't working properly. If you came to a dead stop, it doesn't matter if you had the shifter in 1 or in D, it still started off in first gear.

crazy4c4

I just meant that I had it in the OD position, sorry for the confusion, if that doesnt mess w/ your time then why does everyone always say to make sure its not in OD when you launch?? thanks

also about the headers, b/c I have stock manifolds does that mean it needs backpressure? please forgive me I am young and still learning thanks again

rickneworleansla

No.

Forget about the G-Tech. Take it to the track and get some real readings. You need track conditions, 60ft, trap speed, etc. to really know what is going on.

Iroc57

I have read that the g-tech is somewhat accurate. All of the variables listed in this thread would be present at a track as well.

The question is then why wouldn't it be a good tool for DIY tuning or to check the differences when adding mods? All that you need is a baseline and I see no difference in using the g-tech or a track timer for comparison to that baseline as long as there is a safe place to do it.

Am I wrong?

MTVette

I agree that the only consistent way to evaluate your car's performance is to take it to the track. Too many variables in the g-tech, especially with regard to the orientation of the accelerometers.

For instance, you may have had the device cocked at an angle relative to horizontal for the earlier runs, then more exactly horizontal for later runs. This would have the effect of apparently better acceleration with the later runs.

Another issue is the quarter mile time it said you got - 13.02. For a basically stock LT1 engine with a stock differential, that's really exceptional for a C4 on street tires. The earlier times, 13.7 to 14.1 are more reasonable.

pologreen1

screw it I'll throw it away

crazy4c4

yeah I know that it is extremely impressive for a basically stock lt1 but guys post fully stock lt1's running at 13.3 and13.4 on a lot of other forums so it has been done. Keep in mind that it was 40 deg. outside, most people prob. run around 60 to 70 deg. here in tx if not higher at night so I dont think it is too far fetched. I would love to go to the track but have heard reports of stabbings and shootings out there and would not take my family and put them in harms way... I think with a good baseline and watching the weather it makes a good comparison tool. thats all

crazy4c4

by the way, on your official time slip thread there are fully stock times of 13.07 13.23 13.32 and 13.37, my car has 3.07 gears no cats, an x pipe that relieved a big bottleneck and a decent tune, I would hope that would make the car at least .1 faster so it seems its not too far fetched someday I will make a trip to the track to see how acc. it really is.

Aardwolf

The problem with it being 40° is much less traction in the cold. FYI there's no way it's your tune as suggested on DC.

crazy4c4

I agree, I think the x pipe made the biggest change to the car, that and the temp, I ran it at 100 deg. once and ran something like a 14.5 w/ the aero muffs and no x pipe

Aardwolf

I went from running 13.1 in summer to 14.2 on a cold fall day with lots of wheel spin. This is at a drag track, traction makes more of a difference then ambient temp. That 14.5 was from your G-Tech too? I think your not getting it mounted right or it's an older POS one like I had and you should throw it away.

BTW what are those turbine mufflers? It's possible they have more back pressure then stock.

bobmic93

Those comparisons equate to a 100 rwhp difference. 2+2 dont equal 4 here.

bobmic93

Put a set of grears and a high stall(2800 or higher) and 12s will be realistic unless of coarse your car is a freak which is possible.

JOHN89

Instead of throwing it away why not test it at a drag strip? I made three passes with my G-Tech when I purchased it and it was only off by .01 sec. Yes thats 1/100 of a sec! Now obviously the road has to be flat and the device has to be level.
My unit is the old style led face. Not the new style LCD screen that is downloadable to a computer.

You might be throwing away something that is working fine!

Cheers,
John