Need some quick Dyno advice !

[pliot_guy]

Hey guys, quick question ! I am going to put the Cobra on the dyno this weekend ( just to get some hp numbers). I've never dyno'd a car before. Anything specific to watch out for? something in particular to Cobras that I should have them do? or not do? Also, where should I have them tie it down at? thanks for the help !!!

[bobcowan]

Nothing special, really. They'll know how to tie it down and get the job done. If they don't, you picked the wrong shop.

The biggest thing to watch out for is the engine temp. If it overheats, you could pop a head gasket.

[pliot_guy]

Thanks Bob !

[AL427SBF]

Ask the dyno operator when he intends to start recording data, if you motor is near stock (not a radical build), a pull from 2500 RPM up should be no problem and you'll get the big picture on how it builds power. Goodies speed shop in San Jose can do a chassis dyno which is a better way to go imo.

Our on-site Dynapack 4000 chassis dyno is great for testing your base-line performance output or squeezing that extra horsepower and torque out of your vehicle by our carburetor and fuel injection tuning experts. This dyno is superior over typical roller-type dynes. Instead of parking on a couple of large metal drums that can give incorrect readings due to loss of traction between the drum and the surface of the tire and the freewheeling drums are unable to correctly apply a “load” on your drivetrain to mimic a true driving environment, the Dynapack special hub adapters bolt straight to the drive axles on the vehicle and the power absorption boxes are able to apply a full “load” on the chassis during the dyno test.

[ERA Chas]

Take the hood off when there and have them put the floor fan right in the grill opening.
Be sure the rear tires have equal pressure.

[patrickt]

Originally Posted by AL427SBF

Our on-site Dynapack 4000 chassis dyno ... the Dynapack special hub adapters bolt straight to the drive axles on the vehicle and the power absorption boxes are able to apply a full “load” on the chassis during the dyno test.

Adios to the stub axles.

[MaSnaka]

I'd make sure your oil and oil filter is fresh and full, your coolant level is up, a clean air filter, good gas (oxymoron). The dyno is hard on the engine and will expose weakness. Be prepared for a little HP/TQ dissapointment just in case. Also watch the hood, when the car is hitting 5k+ rpms it may be shaking the hood pretty good with only a prop rod holding it. Oh one more thing...bring any jets, powervalves you may have laying around incase you need to do some A/F tuning assuming you have a carb.

Good luck,
John

[Legless]

Slicks/ semi slicks/ drag radials will rob some hp.

[DonC]

Some things to watch out for.
Top 30 Dyno Tuning Disasters - HD - YouTube

DonC

[itstock]

If you are going to a reputable shop, then you don't need to give them your 2 cents. However, I don't know what air filter you are using on your engine, but I would have them do a run with the filter off and see if there is any difference (there was over a 20rwhp loss with my small circle K&N in the turkey pan). Also, and they should know this, there is no need to rev it to the moon.

[ERA Chas]

Originally Posted by MaSnaka

Also watch the hood, when the car is hitting 5k+ rpms it may be shaking the hood pretty good with only a prop rod holding it. Oh one more thing...bring any jets, powervalves you may have laying around incase you need to do some A/F tuning assuming you have a carb.

A. See post #5.
B. They only let your 'tune' if you pay for each pull. They usually won't permit it because of the time it costs to make changes between pulls.

[PurpleVenom]

I have a solid axle car and they usually tie around the axle housing in the rear, and round the frame member in the front. They also chock both front tires. Make sure you are pretty well centered on the drum with the rear wheels. Raise the hood to full open and have them put a fan right in front of the grill opening. Make sure the car is warmed up to full operating temp (oil and water). They should put a sniffer port in one of the pipes, make sure they blow out the condensation on the sniffer so you don't get a bad a/f reading (air to fuel). Once the car is started and in gear, go through the gears to 3rd or 4th pending what rear gears you have. At this point, you should be able to 'cruise' at 2500 rpm and see your a/f around 12:1 - 13:1 ,could be higher or lower at this point pending fuel injection and size of jets on your carb.

Once the pull starts (when you stab the gas pedal) if there is any sort of popping out of the pipes or any a/f above 14:1, let off the gas. If you are 'driving' the car, don't hit the brakes, the drum has it's own brake and will slow the wheels to a stop, best to clutch in and put it in neutral. Dyno's are a great tool determining what changes need to be made to your fuel system, air system and other things that affect performance. For instance, I know that the difference between the typical oval Cobra air cleaner and the K&N Xtreme top air cleaner is about 40 rwhp and 35rwtq. I also know the difference in a carb being jetted to much will rob your car of rwhp, rpm's and driveability.

If it's a good shop, they can tune things out by looking at the air/fuel line. Pay special attention to this and let them tune it, don't try to tune it by ear or by feel. The computerized dyno does not lie. I've dynoed my car probably 12 times over the past 4 years. Changes in air cleaner, rear gears, intake porting and new valve springs have all made huge differences. My first dyno was 356rwhp. The latest 2 weeks ago was 447 rwhp and I spent less than $2,000 for that 91 rwhp.

Good luck! It's fun to see the big numbers, just make sure the numbers you see are the result of a safe tune for a long running engine.

[razerwire]

A good shop will know - how to tie car- how to keep cool air flow through radiator- will warm up water and OIL before pulls- ask you what you are looking for-ask max rpm you want to go to-will ride in car before hand so you can explain your wants or problems- give you printouts when done. Interestingly I did not know that some builders dyno other components. The transmission in my car came with dyno sheet. They also measure pump pressure and include on sheet.