My friend just got a G-timer (well it is another brand that isn't called a g-timer) and I need some help. For those of you who don't know a G-timer is like a dyno, except you put one in your car, calibrate it and do a run or two. It tells you things like Horsepower, torque, G's, 1/4 mile, 1/2 mile, 0-60, 0-100, and more. It even gives you graphs that you can track the hp you are getting during a run from start to finish. It is sooo cool. Anyways you need to tell it how much your car weighs at that time (including driver, gas ,and everything in it), what the redline is, then calibrate the RPMs, and tell it how many cylinders your car has!?!? You get every option from 1-12 but no option for rotary. So I do my run after telling it I had a six and it says I have 111.1 peak Hp!!! That's outrageous! These things are supposed to be more accurate than dynos. And I have way more than 111.1! If anyone can help, thanks. How many cylinders should I tell It I have?

 

I have one of these and found it massively under-read as well... I'm not convinced they are decent... I've left mine sitting in a box for a while lol...

 

More accurate than a dyno? Are you kidding? If that was true why wouldn't every shop save thousands of dollars and use g-techs instead of dynos? I have used them before and they are not very accurate especially when you are going up or down a hill. All it can do is give you a ballpark figure. Still can be a fun toy nonetheless but it is in no way a substitute for a dyno. Try setting it to 4 cyl since thats about your only other reasonable option.

 

1. Not nearly as accurate as a dyno. In fact, not even close.

2. Tell it you have 4 cylinders and you might like the results better.

3. Still sounds like a pretty cool toy to play with and keep you motivated to improve your car....

 

I just found it annoying having to enter the weight every time on mine. I put it in a box and store it on a shelf now.. too much trouble to play with

 

they arent accurate at all for dyno results, you can make the reading say you have 1000hp if you drive oddly enough. however the 1/4 mile times are pretty spot on, also the skidpad G rating is close enough.

 

thats 111.1 hp to the wheels. how is that so bad? what is your model/mods?

 

My mods should put me in the 225-275 hp range.
* 13B Large Streetport
* RB Header
* RB Pre-silencer
* Flowmaster Muffler
* REPU Carb
* No Smog Equipment

There is more but it is a secret.

 

a 13b streetport put out 275? dude, a 13b full J bridge with 2.25" exhaust and a 3"dia straight thru muffler will get you 275.

My 13b streetport with dellorto put 144 to the ground. Posted it's dynosheet recently; available to search on.

 

First, I said there is more to it but it is a secret.
My Streetport is as big as most Bridgeports.
My engine builder made another engine just like mine which we dynoed at 250+ N/A. You can say that, that isn't possible but It's true.
Also the REPU carb is as good as the best Holleys.

 

Show us the secret porting!

 

Is it an actual g-tech unit or an imation? because mine doesnt have the option of selecting your engine cylinder number. All you need to put in is weight, and what mode you are going for (ie 1/4, 0 -100, - or g force) press the button, and gun it when it says "go" until you have gone through to about 6 in 3rd gear.....

oh, and the reading wasnt too bad for me, I had about 115hp

 

By the Way, I am the friend. G-Tech Pro RR Performance Meter. Brand: Tesla. Don't you wish you had the secrets! MUHAHAHA. Anyways, lol. It was not a valid run, we did not account for wheel spin. It is hard to gain traction in his car, trust me. Imagine this: 2nd gear, 2000-3000 rpms, and then stepping on the gas pedal, and spinning the tires. Thats how hard it is to keep traction. On my dad's 2003 civic lx(automatic transmission) i got 70 wheel hp, when honda claims 115 to the flywheel. this is roughly 61% efficiency between the flywheel and the wheels. My friends 2000 mustang had 130 wheel hp (standard transmission) Ford claimed 190 hp to the flywheel. this is roughly a 68% efficiency.

111 hp, while loosing traction, with an assumed 65% efficiency? Who knows, maybe it is accurate. I think most people say its inaccurate, because they got the vehicle wieght wrong, or are dissapointed. The cylinder input has nothing to do with the the hp output. It is strictly a rpm calibration setup input. Think about it. A regular GTIMER doesn't use cylinder info, doesn't read rpms, doesn't give torque readings. I would imagine the error percentage on hp readings being small. Hp is a function of torque, time and distance. If you don't loose traction, it would have to be very accurate. The only thing that differentiates a accelerometer from a traditional dyno, is a drag coefficent. If you were really ****, you could measure the hp from the accelerometer in 1st, 2nd, and 4th gear. This would give you a function for the decrease in peak hp. Then you could maybe find a hp number trying to use a drag coefficient of 0.

The thing is, is that a certain amount of g's are created by a certain amount of hp. Wrong readings could only be caused by a) loosing traction, b) a lack of consideration for drag, c) or a lack of quality engineering ( i doubt)

 

I always found them to be pretty spot on. Like, within 5% of actual ratings when done at a dyno. Of course, as you said, it just has to be set-up right, with a proper, valid run for maximum accuracy

 

i'll give you one tip on that "secret", its a 4 port 13b, and it most definitely did not follow mazda's standards. The biggest tip, it all began with an engine builder, who got bored with building the normal engine, and got very creative. All naturally aspirated. Also, his 4 port is comparable to a some bridges, so its not like voodoo magic or anything. Keep in mind, its not a common streetport. The secret just lies in how we got such perfectly shaped, ported, polished BIG ports

 

I think the real question, is whether or not our drivetrains actually have that much reduction in power, or if the flywheel hp ratings are extremely optomistic. like a perfectly warmed up engine, on a very cold day for cold air. Also, maybe those engines can put out that much with no exhaust restriction, and other things i can't even think of.

 

My gtech said 48HP haha. I dynoed not long ago at 130... Maybe my unit it stuffed.. still not convinced.

 

i ran a 13.1 with my G-Tech in the rain on my supra, which seems about right. in the dry its good for mid to high 12's

then again it also said i had like 600hp. which is far from the truth.

bottom line, dont trust them. all they are good for is straight line testing speeds. not HP or even handling. has anyone even tried the G-tech handling test? you have to put the thing sideways, set it up oddly and crank the car to ****. it may be accurate according to a few magazines but i'm still not 100% sold. my G-Tech has been collecting dust for over a year for more than one reason.

take it to the track and find out for real is all i can say.

 

^I'll buy it off you, $20. I"m a lowballin ****. And I doubt the drivetrain will account for that much lost power, maybe if it was an automatic.

 

~ 60 effeciency? yikes... there was a dyno run of a stock 12a rated at 100 putting down 85 to the wheels... that's roughly 15% loss, 85% effeciency.. so... nevermind. if that's all it's got i'd rather not know the secret.

 

while wheels were spinning, didn't you see that part, anyways, i'm testing it tommorrow, so i'll let you know what the rwhp is. if its good, i'll brag about it, if its bad, then..... i probrably won't post it out of embarrassment, and go eat my head from inside out or something.

 

haha you couldnt get worse than my "45HP" readout :P

 

We tested it and realized that the secondarys on the carb weren't working. That is less than half power. Once we fix it we're going again.

 

yeah, we got a horrible reading, and i was about to go eat my head, but then we realized the vaccum secondaries on the rx4 carb were failing on us again.
Anyways, I just went to a rotary club that had alot of rx-7s and rx-8s, and i brought the g-timer with me. I rode with a guy in a rx-8, and used it. He had previously got a 167 whp chasis dyno. The g-timer said it had 149 hp at the wheels. If you take account for drag, and the fact that we could have been off a little on the weight, than, a 18 hp differnce seems reasonable. So far, on my gtech pro, from what i can tell, the ratings have all been lower than i would have liked, however, they seem reasonable.
It would be interesting to test all the accelerometers out there. Becasue maybe ones like the $100 G-timer are trash. Maybe my expensive one is better?

 

all i can say is shhhhhhhhhhh they dont need to know... just say your car is fast bob and leave it at that.. If they want to know about the port have them make an appointment with the builder and build a motor for them with there money