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Discussion Starter · #1 ·
Well I tried to get the car dynoed on Saturday but for some reason the place that I took it to get it dynoed their software or something could not read my car right. They couldn't even print off the torque curve!! I ran it four times on there only to come up with nothing. I was so disappointed about that. I really wanted to know what it gained with going from the out of the Box Trick Flow heads to the new CNC 205s. They printed off one horsepower curve but it only was reading 5 hp above my last run which was 333 with my old trick flow heads but with NO torque curve and I thought to get any kind of acurate reading the computer has to have torque to do the math. Now it was reading 338 I know there is NO way I only gained 5 rwhp with this head change and from what it feels like on the street. I can feel the difference in the car on the street. When they did get that one reading they couldn't even print it off showing the rpm range. He could only print it off showing the mph on the graph. Something was clearly a miss with how their software was reading my car. The dyno operator then tried to tell me it was my MSD causing his system to go haywire. It seemed he really didn't know what he was doing. One run he had it hooked to the positve wire on my coil then the next run he hooked it to the negative, then one of the runs he hooked it to the coil wire!! I really don't know what the problem was but there is another dyno in my area that is close and they have never had any problems running my car so I will have to go their when I can. I was pretty bummed out!! At least he only charged me $35. Has any body else ever had a problem like this while getting there car dynoed or is it just my dumb luck?

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1968 protouring Mustang 342 stroker, 205cc CNC ported TEA Trick Flows AOD/3000 stall 4.11 9inch posi.

<font size=-1>[ This Message was edited by: EricButler on 3/2/06 3:33am ]</font>
 

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Discussion Starter · #3 ·
I don't know how it could be reading right without a torque curve and some of the runs he wasn't even able to print off anything. I will report back when I run it at the other shop. I have never had any problems running it there and I should have just gone there but it is further from my house.

<font size=-1>[ This Message was edited by: EricButler on 3/3/06 4:44am ]</font>
 

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Discussion Starter · #5 ·
On 2006-03-02 14:37, mstngjoe wrote:
What kind of dyno was it?
It was the dynojet 248c. I should have known better to run there twice but I figured that time was just a fluke type of thing that day. The first time I went there last year they had problems then also. Although not near as bad as this but that time they could only get the graph to pull up showing the hp numbers with MPH. They could not give a read out showing the rpm range.
 

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The Dynojet will give hp numbers without the torque.

It's an inertia style dyno that measures the acceleration of the drums. The reason you didn't get the torque readings is because it needs the rpm to compute the torque.

Without the operator being able to correctly attach the inductive pickup, there was no rpm reading to be had.

It's best to use the same dyno/operator when trying to compare power improvements after swapping in new components. But.....first you need to find a better dyno shop it sounds like.
 

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Discussion Starter · #7 ·
On 2006-03-02 20:15, mstngjoe wrote:
The Dynojet will give hp numbers without the torque.

It's an inertia style dyno that measures the acceleration of the drums. The reason you didn't get the torque readings is because it needs the rpm to compute the torque.

Without the operator being able to correctly attach the inductive pickup, there was no rpm reading to be had.

It's best to use the same dyno/operator when trying to compare power improvements after swapping in new components. But.....first you need to find a better dyno shop it sounds like.
Ok thanks for the info. Maybe the heads didn't do crap...LOL but it sure feels way stronger on the steet then it used to. I will take it to the other shop that I have done most of all my other dyno runs with and let you know what happens. I may have to change some other parts in my combo to relize the better flowing ability of my heads. I am for certain the stupid air gap intake is holding me back with the cam I am running and being that it is a 342. I just wanted to change one thing at a time and see how it responds to each change.

_________________
1968 protouring Mustang 342 stroker, 205cc CNC ported TEA Trick Flows AOD/3000 stall 4.11 9inch posi.

<font size=-1>[ This Message was edited by: EricButler on 3/3/06 12:25pm ]</font>
 

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horsepower is a direct function of torque and RPM HP = RPM x Torque/5252- mismeasuring either will throw off everything. The dyno measures angular acceleration, derives a torque, and from the current RPM, develops the HP reading. If you look at a correctly calibrated dyno readout, every graph will cross at 5252RPM - since thats how HP is defined.

Sounds like magnetic pickup was messed up, or the sensors on the dyno itself are messed up. New shop
 

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Discussion Starter · #9 ·
On 2006-03-03 00:47, thekingofazle wrote:
horsepower is a direct function of torque and RPM HP = RPM x Torque/5252- mismeasuring either will throw off everything. The dyno measures angular acceleration, derives a torque, and from the current RPM, develops the HP reading. If you look at a correctly calibrated dyno readout, every graph will cross at 5252RPM - since thats how HP is defined.

Sounds like magnetic pickup was messed up, or the sensors on the dyno itself are messed up. New shop
 

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Discussion Starter · #10 ·
It is a new shop and when I called the other shop and told them what happened they said the same thing you did as far as the pickup that reads off the car being messed up. What is weird though is they just got done doing a dyno day when I got up there and I don't think they had any problems with any of the other cars that day. That is just how my luck works I guess. Thanks for all the replies.
 

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mstngjoe is right... a rear wheel dyno can only measure rear wheel torque, and calculate horsepower from there. It can't know the rearend gear ration, transmission ratio, tire size, and torque converter slip, which all are torque multipliers, and thus can't convert rear wheel torque to engine torque without knowing the engine RPM. It calculates HP from the drum torque and RPM, and then uses engine RPM to calculate engine torque from the drum (rear wheel) HP.
 
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