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Dyno measurements .. RWHP and RWTQ

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Clayton used to teach that the rear wheel measured horsepower(they sold chassis dynos, worked on one in 73-74) was 35% less than flywheel horsepower which was 10% less than gross horsepower, which was measured without any drag, alternator, water pump, etc...
 
Bob A.... not sure if you are correcting me or just making a point? I've been told by a number of sources to figure a 15% loss on a solid axle car... my Corvette has a 16% loss because it's an independent rear suspension (probably some other factors but those are the biggies). I was taught to take the rwhp.. such as the 83 and divide by .85 for the 15% loss .. this makes the crank hp of 97.6 (I was just giving rough rounding numbers when I said 100 hp)... you can take the 97.6 and subtract 15% and it gets you back to 83 rwhp to check the math. If anyone has other approachs would be happy to hear them.

Cheers,
Steve
 
Hi Steve,

I was just speaking in general. I was always told it broke down like this:
12-15% for a front wheel drive car
15-20% for a rear wheel drive manual
20-25% for a rear wheel drive automatic.

You're correct in using the 15% number. If you had an overdrive, I'd imagine it would be up closer to 20%

I misread your first post about your power numbers.
 
Doug,
I had seen this before but forgot about it.... love the black/white Healey. I agree with you, based on the research I've done I think the output graphs are pretty accurate for that level motor.....and, it's a torque monster...really strong. Thanks for bringing it back up!!

Cheers,
Steve
 
Hi guys,

I'm mostly a lurker here about every day, but don't feel that I have much to contribute, just soak up information. I'm restoring my Father 100/6 BN4, that he raced through the 60's. He had some dyno trip notes from about '66. This engine made about 150HP at the RW and about 190 ft lbs. He had two egnines I think this was the 12 to 1, 2.6 with a niceley done head, stock ratio rockers, Delong cam (don't know the specs), headers that he made (none were comercially avaiable), and through bored HD6's. What I'm getting at is the numbers sound like they are in the ball park, of course every dyno is a little different.

Barry
 
Barry,

Good to hear from you again. Keep us posted on your progress with old # 7. We need more Big Healeys on the track.

Dougie
 
Barry, thanks for that....I think we're beginning to see a pattern, which is a good thing :smile:.

Doug, great pic!....your car looks really super!!

Cheers,
Steve
 
Steve and others:

On Thursday I will be visiting the VIPER Drivetrain and Performance Lab at VIR (Virginia International Raceway). I have scheduled the day to put my car on the dyno, get some performance assessments and do some tuning. I am in the process of doing some research on the process, but wondered what advice the Forum posters might share on specific things I should hope to accomplish while I am paying for the machine and technician time. I don't know much about this so any tips would be appreciated. My primary goal is to get the engine tuned as well as possible before I undertake my cross-country trip in May.

The Lab was written up in the January Issue of Classic Motorsports.

Cheers,

Lin
 
Lin said:
but wondered what advice the Forum posters might share on specific things I should hope to accomplish while I am paying for the machine and technician time.
Click to expand...

If the time includes gas analyzer testing in addition to the rolling Dyno test, I would HIGHLY recommend purchasing a variety of SU needles (some fatter, some thinner) which will allow you to fine tune the mixture under various loads - this will give you the added advantage of more power and better fuel mileage.

Properly done, you can increase power on your car 5%+ , and maybe improve mileage 10%+. Time well spent if you plan on driving the car all the time.

If needed I have an SU Burlen needle catalog and can photocopy the relevant pages for you. What is the stock needle for your car, and the lean needle?

SU Burlen stocks most of the needles....
 
Lin, I'll look forward to your results. I agree with Alan's suggest of carb needles. I'm also assuming they have a good timing gun to find the optimun static dist. setting...I doubt you'll be able to change the dist. curve at that session but if you can that could be beneficial.

Have fun, take you camera.

Cheers,
Steve
 
Alan and Steve,

Well unfortunately I cannot play with needle replacement this trip. I have no time to get alternative needles.I had to take the slot on Thursday for the equipment. They are starting to get busy with race season approaching. So I will just have to get it as close to optimal as possible and perhaps go back again later.

I will definitely take my camera and plenty of notes!

Lin
 
Hi Lin,

If you don't have a selection of needles a cheap trick is to move the needle up and down in the piston. Take a dial caliper with you and make a note of where you are starting. Depending on the profile of the needle you have .010, or .020 thou change can make a signifacnt difference. Also they can be moved a considerable amount in either direction.

Barry
 
Guys

Was searching the healey list for something else and Jack posted this for his bj8:

quote "Yesterday I took my car to a Speed Center to have my carbs adjusted and
the ignition checked. It's a bit frightening to see a beautiful BJ8
being rigged onto two rollers, being wired like a nearly dead patient in
a hospital ward to a computer and then the brand new engine is carefully
brought up to 3000 rpm, cooled down, run up to 4000 rpm, cooled down and
then up to 5000 rpm. End result was 137.5 real horsepower out of the
rear wheels at 4878 rpm and a max. torque of 253 Nm at 1717 rpm."

Andy
 
To put that in context, And compare Jack's std BJ8 with electronic ignition against Chris's Black and white race car :
https://www.myaustinhealey.com/dyno_sheet.html

All at rear wheels:
Jack 137.5 hp at 4878 rpm with max 253 Nm torque
Chris 159 hp at 4800 rpm with max 339 Nm torque

Not bad for a pretty std BJ8

But adding on the 15% or 1.25 for crank figures you get 158 / 171 hp ?

Quite a bit more than factory 150hp?

Andy
 
Hi Guys:

Just returned from the Virginia Institute for Performance Engineering and Research at Virginia International Raceway (VIR). I had a fun and informative day. VIPER is a joint venture involving Virgina Tech, Old Dominion University, VIR and Institute for Advanced Learning and Research. Victor Seaber was the engineer with whom I worked. He was assisted by Corey.

My goals for the exercise were to get some baseline data on my car's performance and to tune the car for best behavior at highway speed - the 60 to 70 mph range. I am making a 7,000 mile cross-country (and back) trip in May hence my desire for smooth running and as efficient operation as is possible with these motors. We are avoiding interstates on the trip so 60 to 70 is about right. It isn't a race car so peak power and maximum performance weren't too important to me. I told Victor to only push it to 4,500 rpm.

I have a BT7 block with pistons 40 over, BJ8 cam grind, Denis Welch Aluminum Head, 1-2-3 electronic distributor, Phoenix headers with 2" exhaust, lightened flywheel.

Rear wheel HP was 113.2. So is that 130.18 HP at the crank?
Rear wheel torque 146.8

<span style="font-weight: bold">Disappointment of the day</span> - there was no instrumentation (digital or analog) that could measure the smile on my face from driving the Bloody Beast the three hours from my home to the lab!
<span style="font-weight: bold">
Most satisfying experience of the day</span> - We changed almost nothing about the setup of the car. We experimented with timing (but returned to original setting) and did enrich the mixture at high speed ever so slightly. So, I was happy to have my previous work validated rather than disappointed with how out of tune the car might have been.

Here are a few photos taken at the lab:
 

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That's a beautiful facitlity!!...and your car looks super! The way I was taught to calculate it was 113.2 divided by .85(the 15% drivetrain loss on a solid axle car)giving 133.2 at the crank. What was your rpm at that reading? Did you get a graph of the hp/tq curves? I wonder how much more there was if you ran it up to 5,200 redline?...you might get a sense of that from the graphs...i.e. had the curve rolled over and was headed down or was it still climbing.

Thanks for sharing! Sounds like a fun day all around (trip there and the experience).

Cheers,
Steve
 
Those numbers were at slightly over 4500. The torque curve was VERY flat but was starting to drop off at about 4200. The Rear Wheel Horse Power was still on the rise, but beginning to flatten (not as steep a rise) so there were still a few more horses to coax out of the Bloody Beast.

Their facility is immaculate. There were two race cars out of view in the garage for suspension tuning.

Lin
 
Well, it sounds like your engine is a real torque monster...and all things considered torque is what really gives you the punch in the back when you step on it. So it's not unreasonable to project a few more HP but the TQ had peaked...which is what you would expect.

Cheers,
Steve
 
Well,

I guess it was time to revisit this subject. I had another dyno run at Loynings Motor Service on Monday. With my newly assembled race motor conservatively build for power and <span style="font-weight: bold">reliability</span>, triple 2" SU's, 268 duration cam/293 lobe lift/440 valve lift, HD valve springs, J &E .40 forged flat top pistons, larger ss valves, matched ported and polished iron head and custom rebuilt stock rockers, 1.50:1 ratio, etc.

After some final carb adjustments, needles, etc. my pulls were 170 RWHP @5200 rpm and held linear through 6100 rpm and 180 RWTQ @ 3000 rpm and held steady through 4500 rpm. These results exceeded my goals especially when my compression ratio fell short what I wanted at 9.7 to 1. In hindsight this should really help in extending the lift cycle of my motor.

Portland Historic Races 7/10-7/12 will be the first outing with the "fully" tuned rebuilt big six-cylinder......................can't wait.

Dougie
 
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