horse power loss through drive train ?'s
01-25-2016, 06:15 PM
#1
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horse power loss through drive train ?'s Hello everyone! I'm new here and was hoping you guys could help me figure some things out.
I have a 71 chevelle that I put a brand new Turn key engine supply LQ9 in with a performa built 700 rwhp 4L60e.
The car runs like a dream but my issue is, is that when I put her on the Dyno she made 354 hp and 356 torque rwhp. Now according to turn key, the engine I bought was rated at 470/420.
Now to give you some background, I had big stupid wheels on her at the time and only had 273 gears in the rear end at the time of the test. Due to the gear ratio she hit 126 mph in second gear so they wouldn't do the Dyno in 3rd gear.
If the advertised HP was correct that's a huge loss through the drive train. My question is, does anyone know how much HP loss one might expect? Would being in 2nd gear make a huge difference? Thanks.
I have a 71 chevelle that I put a brand new Turn key engine supply LQ9 in with a performa built 700 rwhp 4L60e.
The car runs like a dream but my issue is, is that when I put her on the Dyno she made 354 hp and 356 torque rwhp. Now according to turn key, the engine I bought was rated at 470/420.
Now to give you some background, I had big stupid wheels on her at the time and only had 273 gears in the rear end at the time of the test. Due to the gear ratio she hit 126 mph in second gear so they wouldn't do the Dyno in 3rd gear.
If the advertised HP was correct that's a huge loss through the drive train. My question is, does anyone know how much HP loss one might expect? Would being in 2nd gear make a huge difference? Thanks.
Last edited by Kouba71; 01-25-2016 at 06:21 PM.
01-25-2016, 08:00 PM
#2
The internet rule is about 85% for 6-speeds... (which I assume you have given you were dyno'ing in 3rd vs 4th) but it's closer to about 70rwhp with a fairly stock F-Body drivetrain on a 400+HP motor. But that doesn't help you.
So for you, I don't know what the rearend, tires, trans, clutch, and driveshaft are actually "using." But 85% gives you about 400rwhp. Even if it was 80% it's 375. So you seem like you're down at least 25HP and possibly 50 given their ratings.
Automatics can eat a lot more especially with a high stall converter. Dyno numbers are to be taken with a grain of salt in those combos.
Either way, I'd run it and see what it traps. That'll give you a better indication of the power being made.
So for you, I don't know what the rearend, tires, trans, clutch, and driveshaft are actually "using." But 85% gives you about 400rwhp. Even if it was 80% it's 375. So you seem like you're down at least 25HP and possibly 50 given their ratings.
Automatics can eat a lot more especially with a high stall converter. Dyno numbers are to be taken with a grain of salt in those combos.
Either way, I'd run it and see what it traps. That'll give you a better indication of the power being made.
01-25-2016, 09:34 PM
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Thank you for the reply. I have the 4l60 trans which is a 4 speed auto that is the truck transmission. I'm sure it eats a lot of power it just seems the numbers are pretty low. I know it doesn't really matter, she starts every time and I can drive it coast to coast and do donuts along the way!
01-26-2016, 09:05 AM
#5
You aren't as far off as you think but there could be a little on the table. Hard to say without knowing a lot more details about the engine and everything done to it and the car.
2nd gear dyno run will be lower and it means the converter for sure was unlocked, depending on the converter that will be 20-30rwhp down the drain (my yank ss3600 is right around 25rwhp)
What exhaust is on the car? Headers? 3" duals?
You should realistically be able to make around 380rwhp with the bugs sorted out on a 3rd gear pull. They are wise to do your pull in 2nd though. My driveshaft with a LS and 4l60e and 12 bolt is 56" long. I blew one out on the dyno because it passed critical speed. Tore up all kinds of stuff including the transmission case and most of the guts. If you don't already have a good 3.5"-4" diameter driveshaft that is high speed balanced I highly recommend you get one. It's the best $250-300 you will spend on the car as far as safety.
For reference my ls1 with ported 799 heads, 230/238 cam, fast intake, full exhaust, underdrive pulley, etc made 389rwhp unlocked in 3rd and ran 11.7@114mph that way with a best ET of 11.67 and best MPH of 116mph.
Now with the LS2 and a little more head work and more compression but everything else the same it made 418rwhp unlocked and went 11.46@117
2nd gear dyno run will be lower and it means the converter for sure was unlocked, depending on the converter that will be 20-30rwhp down the drain (my yank ss3600 is right around 25rwhp)
What exhaust is on the car? Headers? 3" duals?
You should realistically be able to make around 380rwhp with the bugs sorted out on a 3rd gear pull. They are wise to do your pull in 2nd though. My driveshaft with a LS and 4l60e and 12 bolt is 56" long. I blew one out on the dyno because it passed critical speed. Tore up all kinds of stuff including the transmission case and most of the guts. If you don't already have a good 3.5"-4" diameter driveshaft that is high speed balanced I highly recommend you get one. It's the best $250-300 you will spend on the car as far as safety.
For reference my ls1 with ported 799 heads, 230/238 cam, fast intake, full exhaust, underdrive pulley, etc made 389rwhp unlocked in 3rd and ran 11.7@114mph that way with a best ET of 11.67 and best MPH of 116mph.
Now with the LS2 and a little more head work and more compression but everything else the same it made 418rwhp unlocked and went 11.46@117
01-26-2016, 11:20 AM
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Thanks! The converter has a 2500 stall and the cam is 226/236 .525 lift and it does have headman headers and 3" duals and a 4 " aluminum drive shaft. I changed the gears to 4:11. I was given a possi that would only fit 4:11 or shorter so instead of buying a new one I just used that one. So now she barely hooks up through second gear. A lot of fun though!!!
Last edited by Kouba71; 01-26-2016 at 11:22 AM. Reason: Pic added
01-26-2016, 04:26 PM
#7
Very nice car.
You might be a little on the low side, but it could also be a stingy dyno or just because it was done in 2nd.
Unless you race it pretty regularly I wouldn't stress over it so long as everything seems mechanically and electrically sound. Could also just be a conservative tune.
You might be a little on the low side, but it could also be a stingy dyno or just because it was done in 2nd.
Unless you race it pretty regularly I wouldn't stress over it so long as everything seems mechanically and electrically sound. Could also just be a conservative tune.
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01-26-2016, 05:13 PM
#8
Which rear end? A 12 bolt will soak up more power than a smaller 10 bolt. 9 inch and IRS rears will eat up at least as much, if not more. Doing the run in 2nd hurt you, I would not assume the guys running the dyno can do the math conversion correctly. Big heavy rear wheels/tires will eat up your power number too. Autos and heavy rears easily make your conversion 18% loss or more. Add in a TH400 or 4L80 and a stall, now you're over 20%. Go see what it traps in the quarter, that math will give you a great average.
01-29-2016, 08:05 AM
#11
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What tune does is it have in it? Or are you a carb setup. I know big wheels,auto,big rear and a second gear pull will make your #'s lower. Could also need some timing and wot fuel corrected. I think your are close to the ball park and it should pickup as it breaks in.