My guess would be 13-15% difference for a manual tranny.

 

I was always told it was around 20%-25% drivetrane loss, depending on auto or manual. It's hard to make an estimation on power/torque on any car. What compression ratio does the motor have? Do the heads have any work done to them? There are a lot of variables to account for. You are probably in the 200hp at the wheels ball park, but without every piece of engine component info, it's only a guess.

 

What would be 'normal' hp/torque at the wheels for the stock 350 back in the day? The only things I have added since '79 are the intake and headers. Not sure what may have happened to it before me. I need to find my casting numbers on the block and heads and list them here so you guys can help me figure out what I have, and what I should expect to see at the rear wheels.

 

I get 20% auto and tall gears, 12% with 4spd and short gears. JMT's.

 

I don't think compression ratio, heads or engine particulars would matter on drivetrain losses from flywheel to rear wheels, but that is just me...

I agree 20-25 is the ballpark on autos thou.

 

with automatíc trans. subtract 20 percent from engine hp to calculate hp at the wheels is what I have heard from an experienced dyno-tuner.

I figure you can subtract about half with a manual trans, since it only absorbs about half the hp compared to an aut.

 

It also depends on the dyno being used. I know a dynojet is a lot more forgiving compared to a mustang dyno. Mustang dynos are extremely accurate and the one I used is acurate enough to give you a 1/4 mile time. To give you an idea my 408 stroker dynoed at 520hp/518tq on the engine dyno. When done on the mustang dyno (car has 4 speed muncie, 342 gears) my car dynoed at 350hp/402tq at the rear wheels.

They told me at the shop that a mustang dyno is more real world numbers. I could take my car to a dynojet and pick up probably 75 additional hp at the wheel.

 

My car was on a Mustang Dyno a couple days ago. It shows 198 peak hp at 4400, 262 ft-lb of torque @ same rpm, measured at the rear wheels.

Doesn't sound very accurate to me. 198 hp @ 4400 rpm requires 236 #ft of torque, conversely 262 #ft of torque at 4400 rpm would equate to 219 hp. How does the Mustang dyno work, anyway? What makes it more accurate than other models? How does it calculate your 1/4 mile time?

 

My car was on a Mustang Dyno a couple days ago. It shows 198 peak hp at 4400, 262 ft-lb of torque @ same rpm, measured at the rear wheels. They tell me the torque runs fairly flat through the rpm range, but the engine doesn't want to rev beyond 4400, almost like there is a limiter on it. I came away pretty shocked at how low the numbers were. This is after they converted the ignition over to the electronic module under the dist cap, new coil, plugs and wires. The car is still in the shop, as I am trying to get everything I can out of it in current condition.

I am looking for some more power, but want the best bang for the buck without spending a whole lot right now. At some point I want to have the motor rebuilt, but that may be a year or so down the road since I just paid for my new paint job, and my oldest 2 daughters are in college this year. I am open to any and all ideas, so lay them out.

Also curious what would cause the motor to wimp out at 4400?

 

Also curious what would cause the motor to wimp out at 4400?

The cam that is in it has a great deal to do with it. It's probably got a stock cam in it. I can't see it having much more than that if it only made 193hp. You could install a better cam and pick up 50-60hp, maybe more, but it depends on what you want the car for. If you want a street car, something with torque, then you are going to want a cam that builds its numbers lower in the RPM range. If you are trying to build a drag strip car, then you are going to look for a cam that builds its power starting around 3000rpm, but then you are going to lose some streetability. You are also going to need a stall converter if automatic. If you build top end power, you are going to sacrifice low end torque and vise versa, if you build low end torque, you are going to sacrifice top end power.

 

How much does gear ratio affect the numbers. In Hot Rod mag, they talked about the competitions at car shows with dino's. All things equal, going from 3.08 to 4.11 gears should give more power to the ground.

 

If I not mistaken, the Mustang dyno uses a water type resistance system. It can put more drag on the rollers by manipulating its water flow to account for real world street type or drag strip driving. The water system is controlled by its onboard computer and is pretty accurate at the times it gives. It can do 1/4 mile, 0-60, and of course tq and hp. It's a nice unit, but as far as actual numbers, I don't think the Mustang is too far superior than a Dynojet. It may be off by a few, but I don't think 75 like the guys told Carbo. I think they were gilding the lily a bit.

 

I have a Mustang Dyno at work ( a trade school ) heres my take on them, First they are a current eddy dyno uses electicity to load. What makes them more accurate than a Dynojet is that the Mustang figues areo losses, I have my car put in at 13 hp @ 50mph, meaning it takes 13 hp to push car 50 mph. I find that auto are about 20% on a stock car, heres the tricky part, when I modify the engine why would the drive line absorb more,it should be the original 20%. It absorbs say 80 hp stock, it should absorb 80 hp no matter what power the engine has, within reason. Driveline changes ( looser converter, rear end changes, tire sizes ) should be the only thing that change driveline losses. When I run mine I actually read it off ground readings they are the most accurarte when tuning. Niether dyno nows what TC I have in. When it says I have 255hp/ 435tq,( in 3rd, I have a 200-4r ) thatis what I have when I'm driving. When I put it in 2nd, hp stays the same tq goes up. They both make assumtions on the math going from wheel to flywheel. This was told to me by someone who teaches tuning not a "Mustang " guy. my 2 cents. Ron

 

When I put it in 2nd, hp stays the same tq goes up.

I thought torque was directly related to horsepower, as in HP = Torque x rpm/5252. Are we talking about a new form of horsepower? Maybe it's called MP for Mustangpower...

 

I think there might be more than 20% loss from motor to rear wheels.

The old HP numbers were bare engine, measured off the crank. In the early '70's manufacturers switched from gross HP to net HP. This means with all the accessories on the motor, which reduces the measured HP quite a bit (maybe 20%). Remember in the 70's some of the muscle car ratings suddenly went from 450HP down to 250HP (partly from detuning and partly from changing the way it was measured.

Now go another step and add the drag of the transmission, driveshaft, rear axle, and wheels. With manual tranny there might not be too much drop (10% more) but with automatic it can be quite a bit (20-30% more), by which I mean additional drop from net numbers. Some of the older auto transmissions were very wasteful of power, but modern ones not so bad.

That is how I understand it, but I'm not an expert on this.
Gersh

 

Exactly... ofcourse torque reading is higher in 2. gear. As i understand, a dyno should be performed with the trans in the gear nearest to 1:1. as equal to no , or as little as possible, multiplication of torque. But then again, I'm no dyno-tuner.

 

I've take the Mustang Dyno and ran it using the ignition to get my tach signal, then ran the same car 10min. later with out using the rpm and just used the rollers only,
and gotten the same readings or very close ( less than 3% ) on a car that was just ran on a Dyno-jet, and only been off the numbers I put in for aero losses, with the dyno-jet sheet in front of me. That is a pattern, that's what I'm basing my info on. That has happened more than once. My Mustang dyno was checked, by Mustang 4 months ago, and given a clean bill of health. I was not taught how to use the dyno by a mustang rep. but by a pro tuner who used the school to hold a class for tuning ( for what ever that's worth ) and the school of hard knocks. I can tell you what that thing does'nt like, made lots of mistakes the first many months I ran it. Ron