Chassis dyno question

Old 06-08-2007, 05:20 AM
  #11  
billhendren
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The chassis dyno will get you very close,we tune top running cars all the time and usually pick up some power which shows up on the strip in the time slips.the key is the weight of the drum never changes so there are no variables. if you don't change anything the runs will overlay within one or two H.P. if your tuning on the drag strip its hard to see 2 H.P. gain but on the dyno if you do several things that pick up two H.P. each you will see the results at the strip.about the only thing you cant do on the dyno is tune for traction on the starting line or converter flash.most runs need to be started at an rpm that is close to converter stall.find a chassis dyno near you that has a wide band A.F meter and you can get your jetting dead on,play with ign timing,valve lash different headers or collector length,engine trans and rear end oil weights and types and many other things,all without using up tires and having to wait for other cars to clear the starting line so you can get another pass.Bill
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Old 06-08-2007, 06:36 AM
  #12  
edvancedengines
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Do not get me wrong. I love chassis dynos.

I like to be able to get my customers to get on them, becuase it isd a wonderful tool to help with a lot of tweeking. You will learn things on a chassis dayno that could take you many months of track testing to learn when it is used as a tool.

I hate chassis dynos when it comes to quickee 3 pulls to get rear wheel horsepower for the sake of bragging rights. I had/hve a customer that has a Mopar RB BB and we got him a little over 670 hp using his Mopar heads when measured on an engiine dyno. He put his car on a chassis dyno and the rear wheels showed a little over 360 hp. He was furious with me at that time. What happened to my 670 hp? He asked screaming at me. The engine hp was still there but not on a chassis dyno it wasn''t showing, becuase he has an old school 5,500 rpm TCI torque convertor in his car.

If you have some extra money and want a little fun, seek out all the chassi dyno in your city, {in mine there are many] and take the same car to all of them. You will think that you were testing with different cars when you see all the results side by side.

If you use a chassis dyno as a tool to check and get a baseline of what the car is now, and then use it to monitor any changes in performance and go to the same chassis dyno ecah time, I love them.

Fact of the matter any dyno, chassis or engine, is still to be used as a worthwhile and valuable tool. Even with engine dynos you will not get repetablity from one dyno to the other.

By all means, I do highly recommend using any dyno you have an opportunity to use and to pay for some real dyno testing. It is money well spent and can save you lots of future grief.

Ed
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Old 06-08-2007, 08:40 AM
  #13  
billhendren
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On your mopar, converter or trans slip would affect H.P. as well as any brake drag,excessive rear end friction etc. could also be fuel supply,200 deg air entering the carb,dist got bumped when installing the engine, or a ton of other stuff. a good dyno operator should have been able to find the problem.that engine if it was an automatic trans should put down around 530/550 to the wheels so there was a problem somewhere.
Since dyno Jet drums are all weighed and the electronics calibrated at the factory to all read the same and have absolutely no user changeable adjustments they should show the same numbers going from one to the other assuming same car and same air temp, pressure etc. other chassis dynos that use a load control instead of a fixed weight will vary quite a bit.Bill
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Old 06-08-2007, 08:57 AM
  #14  
woodsman
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Bill an Ed. Point well taken and I will use this info to my advantage for sure. I do understand that there is no time like track time but I am new in this game of Procharger engines and also this amount of power. I feel that I have a very large learning curve looking at me with this whole set up of car being run off of a lap top and so on. But Conley's in Houston has been do this for a long time and don't seam to be the kind that tells you what you want to hear but the truth. So will give it a go and learn something in the meantime. Thank you guy's for your point of views because there are so many ways to look at the same picture. Wesley
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Old 06-08-2007, 12:15 PM
  #15  
buffjhsn1
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ok so let me get in on this.... how much power does my motor make??? i've never had it on a dyno but i do know what the car weight is and i have a best et to go off of....

2750 ready to race and best et of 8.962

i run a glide with 4.33 rear gears.....i know that it won't be exact, but just a ball park figure would be nice 8)
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Old 06-08-2007, 12:23 PM
  #16  
woodsman
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buffjhsn1 there two places that I like to play around on one is Tim McAmis race cars under cool stuff and Wallace Racing automotive calculators go to these web sites and you can learn something and have some good fun playing around. Wesley
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Old 06-08-2007, 12:59 PM
  #17  
edvancedengines
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Woodsman Wesley ,
Conleys' has a Mustang 1750 with the Eddy Current attachments if I am correct. The results you see there will be very helpful for you. Jeff and I think it is Chris know what they are doing.

Let me tell you an unbelievable but true story just recently. A car from Louisiana late model Purple or Blue (?) Mustand with a Pro Charger was on a Chassis Dyno for several days with the making adjustments and tuning corrections. The following week they loaded it on the trailer and went to Indianapolis with the car never yet going down a race track. It qualified as # 1 in the Radial Tire Class the first day. By Eliminations it had been bumpoed back to 2nd qualifier. When the race was over it had won the whole shebang. Fisrt time down the race track and it got everyone's attention. First race and it won him many thousnd dollars.

So,
Does that answer your question about how much a chassis dyno can help if you are using it as a tool, instead of just a horsepower detector? lol.

Are you planning on coming to the big East vs West vs Gulfcoast Shootout at Evadale on July 21st? I will be there. If you are there just ask one of the two promoters who I am. They both are my customers.
We are having big heavy hitters form both coasts coming in for certain. Two magazines will be covering it, and it should be a fun and good show. Look forward to meeting with you. Now If I could get one of those guys to pay attention to my Chassis Article maybe his car would quit playing leap frog. lol

Ed
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Old 06-08-2007, 01:46 PM
  #18  
woodsman
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Ed you are right about Chris's car and that was a very good news story.Vicki and I are going to Paris, France to look around for a week and will do our best to go see the boy's run on the 21st July never been to that track but its not more then 2 1/2 hours away and will look you up to put a face with a name. Looking forward to meeting you in person. Wesley
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Old 06-08-2007, 06:01 PM
  #19  
68bbnova
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Guys, Thanks for all the replys. I asked the original question because I have 4.10's in my car now, but am going to change to 4.88's, and was wondering if nothing else was changed but the gears between dyno pulls, would the runs look different? Reading all this it looks like maybe yes, maybe not, but to just use it as a tool to get higher readings at the same dyno. If I have the extra coin to run it with the 4.10's first, then change, I will post what I find. Unfortuantly, I think I am only going to be able to do it after the 4.88's are installed, but now I am curious! Thanks again, Sean
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Old 06-09-2007, 05:27 AM
  #20  
billhendren
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On the same dyno with exactly the same atmospheric conditions changing from a 4.10 to a 4.88 will show a few less H.P. at the wheels because your using some of the H.P. to accelerate the entire rotating assy at a quicker rate.its just like on an engine dyno if you go to full throttle and hold the engine steady at say 7000 rpm and take a reading then run a sweep test at say 600 rpm per second increase as it passes 7000 and takes a reading it will show 10/15 H.P. less than the steady state test because of the power being used to accelerate the internal engine parts.on the strip the lower gear may help you because the engine will get into the power band quicker after leaving the line.Bill
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