I have been using my GTECH to estimate my rear wheel hp. Now, I took the car to a salvage place and they weighed the car with me in it at 3580lbs. See mods below. I run 0-60 with the GTECH avg 5.2, and the quarter at about 104. But when I do a hp run through 2nd gear, I only register 209 rwhp. Assuming a 20-30% driveline loss that means anywhere from 260-300hp, but how can a car that weighs this much go this fast with this little power. I have 3.50 gears. I'm really confused cause I run almost equal and sometimes beat my friend with a slightly worked 99 SS but his comes up with 339rwhp and runs about 111mph. What can be wrong, what can I do to be sure? Thanks guys.

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87 GTA 350 L98
K&N filter, beefed up TH-700r4, Accel Manifold, Superram, Fuel Press. Regulator 49.5psi, air foil, modified MAF, SLP cold air box, Accel 24lb Injectors, Ed Wright Fastchip custom chip w/160 thermostat, MSD 6AL and Blaster 3, B&M shift kit & megashifter, Moser Ford 9in Rear with Richmond 3.50 and locker, Edlebrock TES headers and Cat Back,Gutted cat, removed emissions, Hotchkis setup in rear, Poly suspension and Koni in the front, relocated MAT, bypassed TB coolant

 

Despite all the HP hype, true brake horsepower means NOTHING. The formula at which HP is derived is slipping my mind right now but what matters most in a car is TORQUE plain and simple. HP is derived via a mathmatical equation using an engines torque output at a specific RPM. This is why I believe those G-tech things to be completely innacurate when measuring HP because from what I know, it does not take a constant measure of engine RPM at which the foreward momentum is applied.
Just my .02

PDJ

 

To get an accurate reading on the G-Tech, make sure it is in the middle of the windshields below the mirror. Also make sure that you run each gear to the redline all the way thru 3rd.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER, NO CAT
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat
2:73 GEARS
Rebuilt 700R4, with manual valve body
B&M Megashifter, 5" Autometer Tach w/shift lite
Soon to be installed
3:73 Richmond Gears and 3" Hooker Aero Chamber
Corvette Servo & .500 boost valve
15.61@ 95.2mph G-Teched, 1-2 shift slippage, and just replaced a burnt plug wire
"There is nothing more addicting than speed"

 

Just for fun, The way to calculate hp:
(torque x rpm) / 5250

I believe your friend's SS shows more hp because the LS1 makes more torque up high than a tpi and the g-tech sees your car losing torque at the top end, but the LS1 doesn't so when the calculation goes through on the computer(if it even does) it see less torque per rpm and calculates less hp, but that does not mean you dont have it, especially if you are keeping up to a 98 ss. In my opinion those things are only good for 1/4 mile times and skidpad G's, other wise they are just junk. Just my opinion, hope this helps explain why the reading is the way it is


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82 Z28 have LG4-305"
Rebuilt heads-3 angle valve job,ported and gasket matched. edelbrock performer, chevy 1.6:1 roller rockers,MSD6AL, rebuilt carb,15x4" K&N
3"flowmaster american thunder, Mac high flow cat,headman headers,
700-R4--B&M shift kit, B&M tranny cooler.
Sub-frame connectors, boxed lower control arms and torque arm. 1.5" front sway bar, new BFgoodrich radial T/A's--215/65 front 255/60 rear
RADIO-- premier Deh-p300
2-10"kicker SPLs,ZR240,premier 434x(4 way), custom built fiberglass box for subs. pioneer 6X9 & 4X6, grant GT steering wheel

 

his speed on the g tech show's the hp difference. you do say your running with him, but in a full quarter you wouldn't even be close. there is no way you have a 30% drivetrain loss though. your not running a 14 bolt rear with a 4L80E. your drivetrain loss is more in the 17 to 22% loss area. that number is a rough estimate and is used way too much as in on the new f bodies. a guy running a 12 bolt with a turbo 400 using the same percentage as a guy with an LS1, six speed, aluminum driveshaft, and stock 10 bolt is way off. according to gm they are less than 10 percent drivetrain loss (way less than the vette). your running the good number because your powerband is probably pretty flat and strong all the way through. that's just a well set up car, not a car with alot of hp.

 

I appreciate all the input, but I would just like to make an observation on something. The last post says that there is no way for a 30% loss. Well, on a recent Crank and Chrome episode they dynoed a stock 2000 Vette automatic, and it showed a 25.6% loss. Now that's on a 200 vette. Do you honestly think a 15 year old 700r4 with iron driveshaft matted to a Ford 9 inch rear is going to be any better than that? I don't know. And it's funny. The best time my friend has been able to run with his SS is 13.30 at 111 (GTECH) and I usually run damn close to him with maybe a couple of tenths off. Anyway, just an observation, and I am curious to hear what people have to say.

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87 GTA 350 L98
K&N filter, beefed up TH-700r4, Accel Manifold, Superram, Fuel Press. Regulator 49.5psi, air foil, modified MAF, SLP cold air box, Accel 24lb Injectors, Ed Wright Fastchip custom chip w/160 thermostat, MSD 6AL and Blaster 3, B&M shift kit & megashifter, Moser Ford 9in Rear with Richmond 3.50 and locker, Edlebrock TES headers and Cat Back,Gutted cat, removed emissions, Hotchkis setup in rear, Poly suspension and Koni in the front, relocated MAT, bypassed TB coolant

 

The vette sees 25% driveline loss because of the independent rear suspension. The power has to transfer through the tranny, down the drive shaft and into the rearend, converted 90* then has to go through two u-joints. The U-joints are what rob all the power because they are run on an angle and create way more friction and binding then axle and carrier bearings in a solid axle car.
A 20 year old car could easily be as efficient as 15%, if you look at it the right way, especially if manual.
The power comes out of the engine throught the tranny(if manual prob 3 - 5%, but if auto prob 5 - 8%) down the drive shaft, throught the u joint( but the driveshaft is on a small angle( i dont know exactly but prob 10* - 20*, compare that to the vette's coming out of the differential to the half shafts on each side[20*-30*] and you see how the friction and binding occur and the loss adds up)) converted 90* ( 5 - 10%)(5% if you have some amazing synthetic) and then to the breaks.

So if you add up the numbers--- tranny(5%)+ u-joints(4%) + differential(7%) = 16%

so you can see how the numbers add up. ( I dont know if these numbers are correct but i think they might be close)
This is saying that all your bearings are in good condition and your tranny doesnt slip or anything. This is the conclusion i have come to see from all the stuff i have read about it, it is just my opinion, it is in no means fact. Have a nice day

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82 Z28 have LG4-305"
Rebuilt heads-3 angle valve job,ported and gasket matched. edelbrock performer, chevy 1.6:1 roller rockers,MSD6AL, rebuilt carb,15x4" K&N
3"flowmaster american thunder, Mac high flow cat,headman headers,
700-R4--B&M shift kit, B&M tranny cooler.
Sub-frame connectors, boxed lower control arms and torque arm. 1.5" front sway bar, new BFgoodrich radial T/A's--215/65 front 255/60 rear
RADIO-- premier Deh-p300
2-10"kicker SPLs,ZR240,premier 434x(4 way), custom built fiberglass box for subs. pioneer 6X9 & 4X6, grant GT steering wheel

 

if they dyno'd a stock vette i'm assuming they did a chassis dyno. the factory numbers are not likely to be at the same altitude readings, temp, etc, so unless they pulled the engine, dyno'd it and put it back in the car for a chassis dyno i'm not going with their assumptions. i also didn't look and see that you had a 9 inch which would add a small amount more drag than a stock 9 bolt. i didn't look for it since a 9 inch swap in a 13 second car seems like way overkill.

sounds to me like it's a good time you see the track and a real dyno other than the nice, but almost accurate g tech.

 

I don't see why the 9 inch swap is a waste of time i a thirteen second car. I have a strong 13 sec. car and I've already grenaded one 10 bolt. I'd love to have a nine inch. My second ten bolt (that has various mods BTW) is already whining with minimal hard use.
bsa

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"If they do not run, Then they will die." - Stonewall Jackson
#3
'87 IROC, 355 TPI, Converted to SD, 700R4, B&M Megashifter, 3.42, Trick Flow Twisted Wedge Heads, Edelbrock Intake, Accel Runners, Comp Cam, Crane Gold rockers, Lucas 24# injectors, Edelbrock headers, Flowmaster 3'' exhaust, Mallory Ignition, Shift Kit, Corvette Servo, 2,000 Stall Torque Converter

 

Driveshaft angle on a fixed rear should be at -4 degrees for optimum traction, because he torque twists the axle upward, therefore having around 0 degrees of angle.

I notice how much hp gets chewed away with a 4x4 truck compared to a 2 wheel drive version of the same motor. i know it weighs less, but even with the 4 wheel drive off, the extra drag really takes alot away.

 

if you've broken one ten bolt then you are either being too hard on it or not having them set up properly. there are many at our local tracks running 11's and 12's with slicks and surviving so your "strong" 13 second car shouldn't be that difficult. if you can recall hot rod did a project camaro and was using the 10 bolt with slicks and dumping the clutch over 5grand without breaking it. you either are using the wrong stuff or it isn't set up right.

joel does make a good point in the 4x4 area, although put really oddly. 4x4 trucks use the same estimate for hp and they have alot more to turn. it's all an assumption for pride numbers.

for a good example of using this number for their advantage is a fairly local dealer advertising their "SS berger camaro" at 380 hp. they estimated for these numbers and let me tell ya, it's truley an estimate. with just an air lid, reprogram, and chambered exhaust they are claiming a 55hp over stock reading??? not... they are using chassis dyno numbers with the estimates as everyone else is.

 

i am one of the guys at the local track running low 12's on a stock ten bolt. slicks, too. i have been known to be a little hard on parts on the street too. my 7.625 is still holding on. although, i agree that it won't last forever on the track with slicks.

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88 S10
Dropped 5/5
18" Boyd Coddington Timeless 5s
406 balanced with 6" Eagle H-beam rods, 10.25:1 JE SRP pistons, Comp 284XE cam; 240/246 @.050, .507/.510, Dart 200cc Ironeagle heads, Victor Jr. intake, Holley 750 vac sec.
12.20 @ 115.25 mph