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Re: Chasis Dyno...
[Re: Al_Alguire]
#886404
12/23/10 01:08 PM
12/23/10 01:08 PM
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Joined: Oct 2009
Posts: 1,288
Oregon
sg66mopar
pro stock
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pro stock
Joined: Oct 2009
Posts: 1,288
Oregon
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I ran mine on a chassis dyno this year. It really helped getting the jetting and timing dialed in. I also found a major glitch that had been causing a high speed miss. Never would have found that running the car down the track. You probably already know that the numbers might not be very realistic but that's not what you're looking for anyway. I found out the hard way that the chassis dyno can be hard on the car. I didn't have a fan on my trans cooler and should have let the engine idle a lot longer after every pull to get the trans fluid cooled down. The fluid got hot enough to burn the paint off the converter, cook the fluid and damage the high gear clutch pack. Maybe in a way that was good because now I have a new cooler, twice the size of the old one with a 10" fan mounted on top of it, plus a trans fluid temp gauge. I used an old pair of slicks that were about gone and I'm glad I did. The rollers will do some damage. All in all I think it was worth the time and money. I don't know what you'd have to pay but my dyno guy didn't even want to take any money. He just wanted to see the car on his dyno. My wife left $125 laying on his desk and I hope that was enough to pay for his effort. 
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Re: Chasis Dyno...
[Re: dannysbee]
#886407
12/23/10 02:04 PM
12/23/10 02:04 PM
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Joined: Feb 2003
Posts: 4,953
Houston, Texas
TheOtherDodge
master
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master
Joined: Feb 2003
Posts: 4,953
Houston, Texas
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lol... I was wondering when someone was gonna ask that!  The numbers themselves were not great. After the pull, both the dyno operator and tuner (person that did my turbo and FAST system) asked how big my converter was. When I told them it was around 4500 they both said, "that makes sense"... 411 rwhp. They said a big converter like that will "hide" the true power numbers. He said don't worry about the numbers, just go run it. If someone asks what hp did it make, tell them "411 rwhp, do you want to run?". I was told a tighter converter would show much bigger numbers on the dyno but could hurt et if I was not able to spool enough on the line. And, I may have too loose of a converter but suggested I try it anyway to see how it does. Also, I don't know the shape of this converter. It may be slipping alot in upper rpms. Im thinking about getting a 3500 Precision Converter. Right now, the truck rips the tires and runs killer. I was thinking it made around 500+ rwhp.. so anyway...I will report what it runs when our tracks open next year.
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Re: Chasis Dyno...
[Re: TheOtherDodge]
#886408
12/23/10 04:04 PM
12/23/10 04:04 PM
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Joined: Feb 2006
Posts: 698
Alberta Canada
Edge
mopar
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mopar
Joined: Feb 2006
Posts: 698
Alberta Canada
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Sorted out my last combo as far as baseline jetting and timing also found a gremlin in the fuel system on the chassis dyno. Well worth the time and money. Did also damage a slick on the rollers as well.
76 Duster
work in progress
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Re: Chasis Dyno...
[Re: Edge]
#886409
12/23/10 04:16 PM
12/23/10 04:16 PM
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Joined: Jan 2003
Posts: 6,314
The Swamp
MegaDart
master
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master
Joined: Jan 2003
Posts: 6,314
The Swamp
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As already mentioned they can be a valueable tuning aid but can also be hard on parts. I am like you and prefer an engine dyno on a new piece but not on rebuild, unless it's free! After 3 unsuccessful trips to the track I finally put the Dart on chassis dyno when I first put it together. It would drive around and idle fine but would die in the water box  During a pull on the chassis dyno to figure out the constant flow mechanical injection I could see enough flames to cook a hot dog inside the injection hat  So we pulled the heads off to find the material between #2 and #4 was not there! Fixed that and severe valve float and the rest is history!! I don't like the engine braking with that #2k drum driving the tires, pretty hard on parts. check the video [image]  [/image]
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Re: Chasis Dyno...
[Re: 2QUICK4U]
#886416
12/24/10 04:01 AM
12/24/10 04:01 AM
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Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Too Many Posts
Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
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Quote:
SCHOOL ME HERE.ON A ENGINE DYNO ITS ALL THE MOTOR. WHAT IF CONVERTER OR TRANS IS HAVING ISSUES,OR TRANS IS SLIPPING ENOUGH THAT YOU CANT TELL ON A DYNO. HOW ACCURATE IS THE CHASIS DYNO AT THIS POINT? THESE WILL AFFECT THE MOTOR HP AND TORQUE.
I'm not an expert on the subject, far from it, but they can calculate converter/trans slip based on engine rpm versus rear wheel rpm.
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Re: Chasis Dyno...
[Re: Jeepmon]
#886417
12/24/10 11:38 AM
12/24/10 11:38 AM
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Joined: Oct 2004
Posts: 3,097
back in Georgia
dthemi
master
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master
Joined: Oct 2004
Posts: 3,097
back in Georgia
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I have a chassis dyno in my Conyers shop and it's a great tool for set up, and finding problems. Everything from drive train, to A/F. I really don't care how accurate the power reading is. I use it more as a comparison of where we start, to where we finish. Jetting, nitrous, timing curves, and so on are a snap on the dyno. For sure a good data logger at the track can’t be beat, but at least traction is no issue on the dyno. I can grab the motor under full load and make sure everything holds together, and that the mix isn't going to be destructive. Better sitting still and finding a weak point than at 100 mph.
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Re: Chasis Dyno...
[Re: 2QUICK4U]
#886418
12/24/10 11:52 AM
12/24/10 11:52 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
SCHOOL ME HERE.ON A ENGINE DYNO ITS ALL THE MOTOR. WHAT IF CONVERTER OR TRANS IS HAVING ISSUES,OR TRANS IS SLIPPING ENOUGH THAT YOU CANT TELL ON A DYNO. HOW ACCURATE IS THE CHASIS DYNO AT THIS POINT? THESE WILL AFFECT THE MOTOR HP AND TORQUE.
If the trans is slipping(for what ever reason) its
not giving a true number.... remember that the HP
number is just a calculated number based on the torque
reading at 5252... so if its slipping you wont see
the torque applied to the roller... all the chassis
dyno's that I have seen do the pull in high gear so
its a 1:1 pull for the torque reading.... they are
a useful tool and can save alot of time
Also.... turn off your caps lock... thanks
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Re: Chasis Dyno...
[Re: HardcoreB]
#886420
12/24/10 01:56 PM
12/24/10 01:56 PM
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Joined: Jan 2003
Posts: 19,363
Las Vegas
Al_Alguire
OP
I Live Here
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OP
I Live Here
Joined: Jan 2003
Posts: 19,363
Las Vegas
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Thanks for the input guys. I dont care what the numbers are power wise. I know what the engine makes, it was dynoed last time and should be close to those numbers. I am more concerned with getting it broken in and making sure all is well and the tuneup is close. Also how hard it can be on the car itself, tires converter etc. I have a big cooler and fan so no worries there. I just wantto find the best tune up I can. If it dont happen I am sure we will be fine, after all it is basically the same engine and we have the old data. Now gotta runa dn start and finish my Christmas shopping. Good thing I am a big ticket guy, usually makes it go quick. One gift a piece ya know 
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Chasis Dyno...
[Re: Al_Alguire]
#886421
12/24/10 04:01 PM
12/24/10 04:01 PM
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Joined: Jun 2007
Posts: 2,646
Plymouth Meeting, PA
bigtimeauto
Trophy Winner
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Trophy Winner
Joined: Jun 2007
Posts: 2,646
Plymouth Meeting, PA
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A dyno jet chassis dyno is a inertia dyno and thus measures power by rate of exceleration and engine RPM,(That is why you do the pull in high gear 1:1) then computes torque if you so ask it. Remember that the horsepower is what the dynojet is made to read first so as long as the operator sets the parameters correctly and the spark is clean and not erratic its results are usually correct .
I take EVERY car that leaves my shop to a friends dynojet before it goes racing. I would rather spend a hour or two on the dyno then a day at the track looking for a issue. The other bonuses of the chassis dyno is you are logging way more than the average car has, you can watch gauges, you are using the cars ignition and fuel system, you can video blower belts and....., you can make instant changes without worrying about the track and or the weather. I could go on but you guys see what i mean.
Tire pressure is critical, you need a minimum of 20lbs or the tire is not round!! and we tie he car down tight unlike a car sitting free going down the track. I use 25lbs. Do not use new slicks or the webbing on the rollers will tear them up. High power cars with drag radials or slicks need to be screwed to the wheels because when the dyno gets loaded they will slip on the wheel's and may come off the rim.
Its like other tools, when used correctly its great. Unfortunately it may not always be the *number* you are hoping for.
Quick example. Car is on the dyno and looking at the plugs versus the AFR we are lean at the top of the pull. We put more jet in it make another pull car is the same, we scratch are heads go back and look at all of our data fuel pressure, AFR, boost. Nothing there ok we measure our jets and throw in a even bigger set of mains, smaller air bleeds to, now we are way fatter up until 1000 rpm to our rpm limit. Hmmm fuel pressure is good, were fatter GUESS what, the single needle and seat holley bowls would not let enough fuel by them and the bowls were emptying out. this took 2 hours at the dyno. Nothing got hurt and the problem was found. New bowls a week later one pull all is good. So how would you have ever figured a problem like that out driving up and down the track making attempts every hour or so without a data logger on this guys 1200 RWHP street car??
BB, TT5,Procharged 3300lb Street Car 4.79/154
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Re: Chasis Dyno...
[Re: bigtimeauto]
#886425
12/24/10 06:04 PM
12/24/10 06:04 PM
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Joined: Jan 2003
Posts: 19,363
Las Vegas
Al_Alguire
OP
I Live Here
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OP
I Live Here
Joined: Jan 2003
Posts: 19,363
Las Vegas
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Well I have new tires so that will be an issue for sure. Maybe I can find a set of 33x10.5's or soemthing to throw on there.
Thanks again for the info guys...
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Chasis Dyno...
[Re: bigtimeauto]
#886427
12/26/10 12:47 PM
12/26/10 12:47 PM
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Joined: Jan 2003
Posts: 4,243
Canada
Kam*Kuda
master
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master
Joined: Jan 2003
Posts: 4,243
Canada
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Quote:
A dyno jet chassis dyno is a inertia dyno and thus measures power by rate of exceleration and engine RPM,(That is why you do the pull in high gear 1:1)
Any thoughts on the different of dynos and the type of tuning you can achieve.
The one with the 2 rollers (steady state?), I understand that you can hold a load at any given rpm and tune to that area
The one with the big roller (inertia?) would it extrapolate the data over the acceleration curve?
Are there benefits of one over the other
ie street/ strip (steady state)?
race car (inertia)
Carb versus Efi tuning?
I say tuning of an efi system on a 2 roller system dyno (street car) and there were able to hold load over a series of rpm ranges and adjust the timing/air-fuel for low to mid range and see immediate changes in #'s output.
This looked like a great system for a street strip car
Any thoughts?
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Re: Chassis Dyno...
[Re: Al_Alguire]
#886429
12/26/10 03:03 PM
12/26/10 03:03 PM
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Joined: Apr 2004
Posts: 12,339
somwhere
smokinwoody
I Live Here
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I Live Here
Joined: Apr 2004
Posts: 12,339
somwhere
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ya know AL I realy dont have faith in chassis dynos..I know I'll get flamed for what Im going to say but its thru experience that I have had.. one thing...who ever is going to do or does chassis dynoing had better know what they are doing...know the car first or whats in the engine like operating RPM...thats another key we had the duster done when it had the 448 engine...we trusted the guy...were we wrong...he buzzed it up and said it was down on power from the year before...now how can this be...he changed jets and picked up some...then he adjusted the valves..and this is where it all went wrong.. he buzzed the engine so much...splitting my ear drums...like RPM I have never heard out of this engine...we were down on power so he popped the valve covers after he said he heard a noise inside while it was idleing...sure enough..spun bearings and now a slight vibration.. I pulled the engine to find a snapped rod and all sorts of internal damage...those were LY rods..told him they were...he buzzed that engine passed 8 grand...nice guy HUH?? I can see if the operator knows the engine or whats in it and knows how to tune...and has a good following..then I say fine...but I am still a firm believer on dynoing an engine after its been built to tune... and see how its all working together and to break it in...at least the bearings...and if its a flat tappet cam... I know Im long here but that chassis dyno guy realy cost me a ton...and Im still Pissed.. 
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Re: Chassis Dyno...
[Re: smokinwoody]
#886431
12/26/10 04:49 PM
12/26/10 04:49 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
ya know AL I realy dont have faith in chassis dynos..I know I'll get flamed for what Im going to say but its thru experience that I have had..
one thing...who ever is going to do or does chassis dynoing had better know what they are doing...know the car first or whats in the engine like operating RPM...thats another key
we had the duster done when it had the 448 engine...we trusted the guy...were we wrong...he buzzed it up and said it was down on power from the year before...now how can this be...he changed jets and picked up some...then he adjusted the valves..and this is where it all went wrong..
he buzzed the engine so much...splitting my ear drums...like RPM I have never heard out of this engine...we were down on power so he popped the valve covers after he said he heard a noise inside while it was idleing...sure enough..spun bearings and now a slight vibration..
I pulled the engine to find a snapped rod and all sorts of internal damage...those were LY rods..told him they were...he buzzed that engine passed 8 grand...nice guy HUH??
I can see if the operator knows the engine or whats in it and knows how to tune...and has a good following..then I say fine...but I am still a firm believer on dynoing an engine after its been built to tune... and see how its all working together and to break it in...at least the bearings...and if its a flat tappet cam...
I know Im long here but that chassis dyno guy realy cost me a ton...and Im still Pissed..
I've only been on a chassis dyno once and after it
was strapped down and the sensors were in place...
the first thing out of the operators mouth was....
what do you want to turn it to
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Re: Chassis Dyno...
[Re: bonefish]
#886433
12/26/10 05:48 PM
12/26/10 05:48 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
the time i did it i was sitting in the car controling the rpm,s 
I forgot I did it twice... once on the Woodward cruise...
they asked if I would display and run on the dyno...
in that one I was behind the wheel... but the second
time a operator ran it with me standing there
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Re: Chassis Dyno...
[Re: bigtimeauto]
#886435
12/26/10 06:30 PM
12/26/10 06:30 PM
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Joined: Apr 2004
Posts: 12,339
somwhere
smokinwoody
I Live Here
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I Live Here
Joined: Apr 2004
Posts: 12,339
somwhere
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Quote:
Quote:
ya know AL I realy dont have faith in chassis dynos..
he buzzed the engine so much...
I pulled the engine to find a snapped rod and all sorts of internal damage...those were LY rods..told him they were...he buzzed that engine passed 8 grand...nice guy HUH??
C'mon now, you had bad operator not the dynos fault!
First question is always what's done to the engine and how high do you want to take it. If its a new tune we always do pulls in 500rpm steps after 6K to see where it falls off without going past. As for where they make HP you can tell when the car isn't making power and you should pull your foot out of it.
Maybe this topic should have been titled *Chassis Dyno operators!*
good point...
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