Ok i just used a G-tech Pro to measure my cars 1/4 mi time and Hp/Tq and i was a little disappointed . But my question is "Does the weight that you put in for vehicle weight matter a whole lot?" I put in 3500lbs. I know my car weights a lot more ( like 4200lbs.) but I think it would make a differnce, right? Well just looking for some input thanks!

 

a stockish thirdgen is around 3,300 to 3,500 w/o driver.
so u guessed right.

 

yeah but it gave me 119Hp/ 129tq! That is insulting to any v8 if you ask me . I have an LO3 that was rated at 170Hp/255Tq and it is hard to believe that 114,000 miles will drop the numbers that mutch plus I put a full exhaust, ultimate TBI mod, and removed the smog pump. I'm baffled

 

Yeah but the G-tech are measuring your actual performance at the ground and the factory ratings are at the motor. There off a little bit too.

Then you got figure in the G-tech measures off the line horsepower when any other chassis dyno would run your car into a 1:1 ratio on the transmission then pound it. So you got to account a little bit for wheel spin, roll in hesitation (if any), and just the accuracy of them.

My G-tech was telling me I was making around 230 HP or so and the dyno said 211. There fairly close and there decent to use as testing and tuning tools. Anymore I only really use mine for 0-60 mph time... maybe 1/4 mile if I want to stay on the gas.

 

Garbage in, garbage out. It needs to know the total weight of the vehicle with driver, fuel stereo etc since it does calculations based on accelleration with weight. Giving an incorrect weight will give an incorrect HP/ET etc.

 

Yeah but you got to admit the 0-60 and 1/4 mile would be nice things for tuning since they don't have any weight settings on them. That way you can compare the times to the G-tech's previous runs... it seems to be pretty consistent. Just gotta make sure you level it out each time properly.

 

I have a '91 gta 305 tpi. My weight with my stereo, spare tire and me in it was 3690.
Make sure that you are inputting that number into your g-tech other wise it scews the figures. I have the same gtech.

Also, remember that for every 100lbs, it is a tenth of a second in the 1/4 mile(roughly 10 hp).

 

so the Gtech gives the hp att the wheels, and not the motor?

so with a automatic trans. i can add 20%?

example: Gtech (i got the cheap version) gives a 160 hp, so thats 192hp the engine delivers.

right?

 

Yes, rear wheel hp. But it depends on traction.

So yeah,20% .

LB9GTA

 

20% is only a rough guess. Different transmissions and differentials give different hp losses. Swapping transmissions can decrease the hp loss without touching the engine.

Lets say your engine produces 200 hp and you guess at a 20% loss giving you 160 hp which is a loss of 40 hp. My 600 hp engine with your powertrain loss of 20% means I only have 480 hp losing 120 hp through the same powertrain instead of 40 hp.

That's why a percentage loss is only a rough estimate and shouldn't be used to calculate engine hp from RWHP.