Chris, as you know ,some years ago on an insane moment, I bought a Stuska
engine dynamometer (XS-111, waterbrake). In manual mode, I hold the engine
(WOT) at constant rpm,say 4000, then 4500, and so on. The inertia doesn't
matter then, because there is no acceleration. And calibration for manual mode,
constant rpm, is very simple : the loadcell (electronic sensor) is loaded with
a known weight on a bar of 3 ft long to the center of the shaft of the
waterbrake. But when I make automatic runs, the software is asking for an
inertia value and calibrating for automatic runs can be done in 2 ways : by
actually measuring the weight of the rotating components of the engine being
tested (weight of the components times the mean distance to the centre of the
components). In practice this is not possible. The 2nd way is by trial and
error : I fill in a value for the inertia of the engine and then compare the
power results of the manual mode and the automatic runs during one and the same
session; I change the inertia value untill manual mode and automatic runs give
the same results and then there also will be no difference in the power and
torque curves between a fast run(WOT and low braking action of the dyno) and a
slow run (great braking action) . If the inertia value is not correct, the
curves of fast and slow runs will be different. The faster the run, the bigger
the deviation.
The inertia value of the rotating components of my dyno is 0.07Ft-Lb-sec?. the
inertia of a small chevy block is 0.25. A Tr 4 or 6 cylinder engine has not
much less inertia. By giving in an exaggerated inertia value in the software
program, the power and torque results are way off, as much as you like. The
results in manual mode are always correct if the simple calibration is done
correctly and the manual mode has also the advantage of being able to test the
engine at wide open trottle at high rpm during a long time and looking if the
power is going down after a while by overheating of the combustion chambers and
detonation. You will not find that out by a fast acceleration run on a chassis
or engine dyno.
So I think we are talking about different things concerning the influence of
inertia?
Marcel
<fot at autox.team.net>
Aan: "fot" <fot at autox.team.net>
Verzonden: Woensdag 5 september 2018 14:56:14
Onderwerp: Re: [Fot] 89MM piston question
Hi Marcel,
inertia of the engine and the drive train influent the results at very high
power figures >500 hp, wenn the rolls of the dyno get accelerated very quickly.
The TR engines are not powerful enough it takes several seconds to shift the
revs on a run from 2000 to 7000 so the inertia is not a thing to care about.
Cheers
Chris
Von: Fot <fot-bounces at autox.team.net> Im Auftrag von van.mulders.marcel---
via Fot
Gesendet: Mittwoch, 5. September 2018 10:34
An: Jim Gray <toodamnfunky at comcast.net>
Cc: fot <fot at autox.team.net>
Betreff: Re: [Fot] 89MM piston question
It seems I've a chance someone here knows what the inertia is of the rotating
parts of a (standard) TR4 and TR6 engine?
PS : most chassis dyno's are measuring horsepower out of the acceleration of
the very heavy cylinders (great inertia). The wheels of the car are resting on
these cylinders and accelerate them during the runs. But the engine has also to
accelerate the rotating parts of the car(crank, transmission, wheels..). I
suppose that the dyno operator has to make a guess of the inertia value of
these parts and add it to the inertia of the cylinders. Here is a comfortable
opportunity for the operator to make the customer happy : if he is adding an
exaggerated number for the inertia of the rotating parts of the car, then the
horsepower is exaggerated. As far as I know , chassis dyno operators never
mention or ask about the car inertia. It would be very interesting though to
know the value he is using, because then you can always use this same value for
runs on different occasions and compare the results a bit better. A chassis
dyno is really only usefull to compare the results of changing things on the
engine during one and the same session.Don't be fooled by the absolute numbers
: Once I went to a chassis dyno with my TR3 : my car must have looked pitiful
against the modern cars the operator was normally testing, because the result
was 210 bhp at the wheels and I knew it surely had no more than 180 bhp at the
flywheel! I don't know if some chassis dyno's have a brake to hold the engine
on a constant rpm at WOT : then the inertia of dyno and car doesn't matter and
you know the right horsepower at the wheels. About right at least : you can
cheat yourself a bit by overinflating the tyres and the dyno has still to be
calibrated rightly.
Marcel
Van: "fot" < [ mailto:fot at autox.team.net | fot at autox.team.net ] >
Aan: "Bill" < [ mailto:Bill at ponostyle.com | Bill at ponostyle.com ] >,
"Larry Young" < [ mailto:cartravel at pobox.com | cartravel at pobox.com ] >
Cc: "fot" < [ mailto:fot at autox.team.net | fot at autox.team.net ] >
Verzonden: Woensdag 5 september 2018 02:44:00
Onderwerp: Re: [Fot] 89MM piston question
You mean something like this ? Measured on a chassis dyno. The notes on the
left are the suggested power train loss
as described by the dyno shop. But, whatever the final numbers are in truth the
5250 mark is right there.
This was the comaprison to my 2015 engine spec.
I shouldn?t have advanced that cam me thinks.
jim g
From: Fot < [ mailto:fot-bounces at autox.team.net | fot-bounces at
autox.team.net ] > On Behalf Of Bill via Fot
Sent: Tuesday, September 4, 2018 3:08 PM
To: Larry Young < [ mailto:cartravel at pobox.com | cartravel at pobox.com ] >
Cc: [ mailto:fot at autox.team.net | fot at autox.team.net ]
Subject: Re: [Fot] 89MM piston question
I?m being a bit facetious, I understand what people mean (sort of) but I?ve
heard ?Horsepower wins sales, torque wins races.? and the equivalent spoken or
written sagely, with solemn nods all around, too many times not to comment. One
is a functional equivalent of the other, both in a mathematical and practical
sense. The relationship is linear. Torque is force. Horsepower includes a
circular distance component to express work.
As you say, the numbers for the power and torque curves should equate at every
point (adjusted by the function). The fact that they often don?t is
ridiculous?horsepower measured by a dyno is calculated from torque and RPM, not
directly measured. The shorthand bullshit detector for dyno curves expressed in
Imperial units of ft-lbs and horsepower is to see if the curves cross at 5252
RPM. Many don?t, including those published in car magazines.
Sheesh.
On Sep 4, 2018, at 9:21 AM, Larry Young via Fot < [ mailto:fot at
autox.team.net | fot at autox.team.net ] > wrote:
P = T*R/5252
When people talk about a torquey engine, they usually mean it makes its power a
low revs.
I once ran an engine on two different rolling road dynos (a Dynojet and a
Mustang Dyno. The guys at the dyno shop said the second one would give less hp
because they used a brake in their setup. I said, "you didn't calibrate for
that"? They backpedaled and gave me a line of BS. Then the power and torque
curves they produced did not agree with the equation. To get an explanation, I
worked my way up the chain and eventually talked to the dyno companies head
"technical" guy. He said he thought it must be the calibration! I said, "it is
basic physics, like saying F = ma". Since then, I have never trusted dyno
numbers. Good for comparative tuning runs only and of course, bench racing.
- Larry
On 9/2/2018 10:46 PM, Bill via Fot wrote:
BQ_BEGIN
It always puzzles me when people say that. Horsepower is torque times RPM (and
a conversion factor). Torque is horsepower/RPM. So how can one count more than
the other?
BQ_BEGIN
On Sep 2, 2018, at 4:13 PM, Mordy Dunst via Fot < [ mailto:fot at
autox.team.net | fot at autox.team.net ] > wrote:
Its the torque that counts. So, I suspect the motor enhancements took the
benefit of the tractor stroke. If the motor is able to produce that power at 6k
rpm with shift at 6500.
I shift at @ 6200 - my motor produces max power @5800 on the dyno. I use a
kastner designed cam for which I have the masters.
MDunst [ http://headgasket.com/ | Headgasket.com ] [ tel:626.358.1616 |
626.358.1616 ]
Fax [ tel:626.628.3777 | 626.628.3777 ]
Triple R Munitions, Inc [ tel:626.201.9471 | 626.201.9471 ]
T FFL 6,7 SOT 2
On Sunday, September 2, 2018, John Styduhar via Fot < [ mailto:fot at
autox.team.net | fot at autox.team.net ] > wrote:
BQ_BEGIN
What kind of modifications were done to the engine to extract over 200 HP from
a tractor engine? Nitrous shot.
On Sat, Sep 1, 2018 at 3:05 PM Thomas Boyd < [ mailto:tom at trenterprises.com
| tom at trenterprises.com ] > wrote:
BQ_BEGIN
All of our FIA race cars are running legal 87mm engines.
Just rolling roaded the latest SLR build at well north of 200bhp
Thomas Boyd
Director
TR Enterprises
[ tel:01623%20793807;302 | 01623 793807 (ext 302) ]
[ http://www.trenterprises.com/ | www.trenterprises.com ]
On 1 Sep 2018, at 17:02, John Styduhar via Fot < [ mailto:fot at autox.team.net
| fot at autox.team.net ] > wrote:
BQ_BEGIN
If you really had serious compliance with most group's rules, I would guess
half the TR cars would not pass muster. Let's have fun together.
On Sat, Sep 1, 2018 at 9:40 AM Terry Stetler via Fot < [ mailto:fot at
autox.team.net | fot at autox.team.net ] > wrote:
BQ_BEGIN
Indeed there are Glen.
Sent from [ https://go.microsoft.com/fwlink/?LinkId=550986 | Mail ] for Windows
10
From: Fot < [ mailto:fot-bounces at autox.team.net | fot-bounces at
autox.team.net ] > on behalf of fubog1 via Fot < [ mailto:fot at autox.team.net
| fot at autox.team.net ] >
Sent: Saturday, September 1, 2018 7:34:26 AM
To: [ mailto:rkramer56 at gmail.com | rkramer56 at gmail.com ]
Cc: [ mailto:fot at autox.team.net | fot at autox.team.net ]
Subject: Re: [Fot] 89MM piston question
BQ_BEGIN
everybody else seems to be using 89.
HaHa not everybody, rules say 87mm, there are still a few guys running them
(and winning)...
Glen
-----Original Message-----
From: Bob Kramer via Fot < [ mailto:fot at autox.team.net | fot at
autox.team.net ] >
To: van.mulders.marcel < [ mailto:van.mulders.marcel at telenet.be |
van.mulders.marcel at telenet.be ] >
Cc: fot < [ mailto:fot at autox.team.net | fot at autox.team.net ] >
Sent: Fri, Aug 31, 2018 11:26 pm
Subject: Re: [Fot] 89MM piston question
I've always used 87 MM due to the rules but everybody else seems to be using
89. The procedures are the same so It'll be the same. I blew a head gasket last
time out, compression into the cooling system and blew off the bottom hose. I
guess it wasn't tight enough, and scuffed two pistons before I could shut it
down.
Bob Kramer
On Fri, Aug 31, 2018 at 12:43 PM, < [ mailto:van.mulders.marcel at telenet.be |
van.mulders.marcel at telenet.be ] > wrote:
BQ_BEGIN
Bob,
It is definitely necessary to make that modification to the liners. The relieve
should correspond to the shape of the combustion chambers : about 4 mm wide on
a 89mm engine.
Marcel
Van: "fot" < [ mailto:fot at autox.team.net | fot at autox.team.net ] >
Cc: "fot" < [ mailto:fot at autox.team.net | fot at autox.team.net ] >
Verzonden: Donderdag 30 augustus 2018 00:05:43
Onderwerp: [Fot] 89MM piston question
Do the guys running the 89MM pistons and liners need to relieve the liners to
clear the intake valve, or does the extra MM make the difference?
Bob Kramer
On Tue,
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