talonted,

Very nice car you have, BTW. The numbers aren't even close between a 2wd Dynojet and ours. I remember we pulled your car an extra time or two and re-tied it down to drop the wheel spin, which I think we accomplished. One of your guys said it hooked up much better on the MD than on the Dynojet if I recall correctly.

The reason we did the pulls in 3rd gear was we calculated RPM from roll speed. The gear is suppose to be 1:1 but I was honestly chicken with 100's of people standing right next to the cars to run them to 150 mph in 4th gear, atleast the cars that could have made it. Some of them were pretty sickly and barely made 80 mph in 3rd! The tack pick up was not working worth a ****, I actually threw it on the floor at one point. I know have a good pick up and could pull a tach signal. Even then I would have been chicken to pull the cars in 4th, the gear is so much longer, so many more things can happen and there were just too many people standing right next to the engine. That is why.

The Dynojet doesn't "load" anything. It is just a big *** heavy roller that spins around in circles and gives you a nice big number. That's all it is. The rollers weight about 4,000 pounds, so when you start your pull it is like pulling a trailer and when you end they are just spinning with a bunch of momentum. Useless for tuning.

The weight I used was not 3250 for all the cars. I used 3250 for all the 2g FWD's. The weight was changed per car per run unless the cars were the same. There is a large database in the computer that you have to look up the car, year, FWD or AWD and then it gives you the weight to enter and the HP the car uses to go down the road at 50 mph (HP@50) number.

Thanks for attending.

David Buschur
www.buschurracing.com

 

A bone stock FWD 2g (manual transmission) weighs 2915 pounds.

 

So if you enter a number that is higher than the car's actual weight, it would spit out a lower number than what it should be, correct? If that's the case, I would invest in some corner scales so you could easily weigh each car as it comes in. They only cost $800-$1000.

 

Did the dyno plot you got show the RPMs climbing to 9000RPMs? Or did it stop at 6000RPMs?

My AWD Eclipse can do over 100mph in 3rd gear at 7500RPM. Revving an Evo from 30 to 80mph in 3rd gear might make sense. But 80mph in 3rd gear is nowhere near redline on a DSM.

 

Thanks David. Actually it was my last pull on your dyno that I spun the tires, you had re adjusted the straps because my wheel was clocked a whole lot. I never spun on a dyno before this year, but I think that is probablly due to the fact that I was doing pulls in 4th on AMS's dyno. For that last pull I had made a few changes to the EMS, bumped up timing a bit up top, because of the new exhaust manifold, and also cranked up the boost to about 39-40 psi. I have the AEM log avilable for anyone who wants to see it.

I always was under the impression that the whole attraction to a mustang dyno was that you could hold the car at certain load points, and tune each point?

In any case I was going to say to Josh, my dyno graph ended at 8000 even though I wound it out to 9000. However Dave said that for most of the cars he was using vehicle speed to base the rpms on I believe. But with my car I asked him if I could use a RPM pickup since I am so used to doing that for a dyno, and I already know wich trigger wire to use off of my COP setup.

 

When I dyno a car, I want the weight to be about the same as if it was the car and driver on the street. So if a FWD 2g weighs 2915lb and the average driver is 200lb, you want the weight to be 3115lb. If David entered a weight of 3250lb, then basically the dyno is simulating an extra 135lb of stuff in the trunk....something that really isn't going to affect how the car reacts on the dyno.

The road load simulation has no significant effect on the hp and torque numbers that the car produces. The engine is still producing the same amount, it's just pushing a little more simulated weight. You might notice a few horsepower difference.

I was there on Saturday helping David if he had any questions or problems and all of the 2g DSM's I saw run on the dyno were right inline with the numbers I produced on our dyno in our demo lane when tuning my buddy's 2g Eclipse GS-T with the BR475 kit.

Tim
Mustang Dynamometer

 

So how is doing a pull in 3rd gear going to affect the actual hp values vs. doing a pull in 4th gear? My guess is that it would drop the values in compairison to a 4th gear pull.

 

Numbers are slightly lower in 3rd than in 4th, around 8-10 whp.

David Buschur
www.buschurracing.com

 

I understand what you are saying but it just seems worth it to me for it to be that much more accurate. I posted the weight of the 2g FWD bone stock so that one could assume that Talonted's fairly high HP car was pretty serious. Therefore it would have a decent amount of weight reduction done to it and maybe weigh 150 pounds less than stock. So if the driver does weigh 200 pounds, that would put the total weight at 2965 which would be nearly 300 pounds less than the inputed number.

 

I've been curious about just what the weight and HP@50 parameters are used for. I gather it's just to set the load and not used to derive a net power after accounting for drag. If that's the case then, if at all different, should a load that's too high give a slightly higher reading due to the slower RPM slew?

Oh, what are the practical limits on steady-state operation? For example, how long can a Mustang hold a set RPM at 300HP?

Dave

 

mike 99gsx,
When you have a car that is highly modified, you probably also know the weight of the vehicle. If that is the case, put the weight of the vehicle plus the driver into the computer instead of what the look-up tables say. That way you are tuning for that individual car.

djh,
Correct, those 2 numbers are used in the Road Load Simulation program that comes with our dynos. The weight is obviously the weight of the vehicle and the HP @ 50 is the amount of HP it takes to push that car down a flat road at 50mph - aerodynamic coefficient of the vehicle. Usually 10-15 for cars and 19-25 for trucks Basically when your car is on the dyno, the load on the motor is the exact same as if it were on the street....weight, wind friction, road friction are all simulated on the dyno. This is why the car accelerates at the same rate on the dyno as it does on the street and this is what allows you to run 1/4 mile runs on the dyno (although, I don't recommend AWD launches - found that out the hard way ). The two numbers have nothing to do with the amount of HP the dyno is reading. There is a load cell attached to the eddy current that measures the torque of the vehicle and from torque and RPM, we get HP.

As for the steady state operation, David Buschur's dyno should be able to hold 300HP constantly for longer than the car can make it (i.e. car overheats)

Tim

 

Thanks for answering Slorice, couldn't have said it better myself!

David Buschur
www.buschurracing.com