Thread: first time at the track

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I've had this up before, but this is dyno results on a 460 =.030 Ford with a solid lifter cam (spec'd by Comp Cams), a Coan glide with a 3800 stall converter... This car weighs 2485 with driver and fuel, runs consistent mid 10's with 500 rwhp... This is real world, not overely optimistic desktop dyno numbers.....BTW, real efficiency numbers for your desktop dyno are probably closer to 80% then they are to 100%. I guess if we just all used the desktop dyno numbers, we wouldn't have to bother building the car or taking it to the track, huh?????

When i put my car on the chassis dyno, the chassis dyno owner told me to add around 30-35 percent to the numbers to get close to what the engine horse power should be.

The way i looked at it was, i didnt really care what the engine was putting out, I wanted to know how much of that power was getting to the ground, as thats what really counts. My engine builder informed me that this was the 8th engine he has built with the same specs and all the others were putting out just over 800 horse power on the engine dyno...

With Cobra Jet heads, your restricted to the amount of power you can get from an engine. You can bet the next set will be the Blue Thunder heads...

im guessing very high 12's low 13's and dave is right that stahl is way to high for a street application. you migh want to go to the strip first so we can hear the numbers, thats before you melt the tranny driving it on the street.

Engine horsepower is good for bragging rights, APPLIED horsepower at the rear wheels is what wins races!!!! With a good chassis dyno and a knowledgeable operator you can make about 3 runs on it and your car is track tuned and ready.... IMO time on the chassis dyno before you go to the track is a very worthwhile investment...

Like Dave said all the H/P in the world isn't any good if you can't get it to the ground.

Originally Posted by GGRacing

Maxed_out_rpms, you might be really suprised how much more power your making if you were to put your engine on an engine dyno, vs a chassie, the big converter is a huge power loss and will not register how much power your actually making, or take into account the tq multiplication that the converter provides, so imho chassie dynos are kinda worthless on automatic cars, you really need to run an engine dyno to find out shift points, max HP/TQ, A/F

The chassis dyno we use measures air/fuel ratio, shift points, and many other things. It records all the information numerous times and prints out graphs when the run is over. Carefully analyzing the data will tell you everything you need to know about all aspects of engine and driveline performance.... All the engine dyno does is measure horsepower and torque at the crankshaft which is a good R&D tool for an engine builder. Tuning a specific car for max performance IMO a chassis dyno with the correct sensors and operator provides far more worthwhile information. Shift points are very easy to calculate using a chassis dyno, just study the graph for peak torque and/or horsepower readings......

Thats the same type as i was running the car on Dave. First thing we did was shove the probe into the exhaust ( opps...had to jet down alot to be close to peak power.. ) I still, like in all the posts i have posted on here, agree that the chassis dyno is the best way to go for accual numbers on how your car will perform on the track/street.

Like GGRACING was saying, if you just want to know what the engine puts out, go to an engine dyno, BUT, if you really want to know what the car puts out, use the chassis dyno. Atleast that way you will know excactly ( or as close as your going to get ) to what the car will put out after going threw the torque convertor, transmission, drive shaft, rear gears and tires.

The graph he handed me when it was all over showed me everything i needed to know ( except my reation times.... )

We are not saying that engine dyno's are not the way to go, they are good. If you have the extra cash and availability get the engine done first, that will help you pick a proper torque convertor, then have the chassis done also.

Pending on what you have bolted to the back end of the engine, it might have an impact of what your shift points will be also, as there are unlimited amounts of combinations to run. If your running transmission gears that are close together and a broad power band, you might not want to turn the engine so high, but if your running a 2 speed you know there will be a bigger drop in engine RPM when you shift, so you might want to turn the engine a little higher knowing the RPM's will drop alot more than they would with say a 4 speed manual for instance. Those are the kinda things you find out with the chassis dyno.

The chassis dyno guy that i used even told me how much fuel i was going to burn on a pass ( and he was really dam close...fooled him because i rejetted before making a few passes... )

Well ill put some backround to what i stated earlier, iv seen 600+HP cars putting in the 300's on the chassie dyno with big loose converters like are being discussed and the cars would run times that were typical of their power level, so what the chassie dyno is registering is pretty inaccurate way of getting power levels if this is the case, however stated also is the fact that it is like making a typical dragstrip run on a dyno and that will feed you different information about the car, so like i said i believe that chassie dynos are nominal in trying to calculate hp/tq in automatic cars, but if that is not your concern as it dose not appear to be, then a chassie dyno is for you, i was just trying to make a point about the cars with big non-lockup converters
Steven

I think your missing the point GGRacing, we know that the chassis dyno will not give you the true reading of excactly how much HP the engine ITSELF is putting out. What we like to know is how much of that power is accually getting to the ground where it counts and what we can do to get more of the engine power to the ground.

Think about it this way, If you lifted weights at a gym, lets say you can lift 250 pounds over your head. Now you go to work and your work involves loading heavy boxs from the floor to a platform. Can you still lift a box that weighed the same 250 pounds? NO, because the box is oddly shaped so alot of your muscle power is used to hold tight to the box so you dont drop it. So in all fareness, you cant accually tell your boss that you can lift his boxs that weighs 250 pounds. ( This might not be the best exsample...but i think you get the idea )

The engine dyno is very good for checking out your engine combination, a chassis dyno measure how the power is applied to the ground, including dubious converter and tranny setups..... I'm still a manual tranny guy so "loose" converters aren't a concern... Both dyno's server their purpose well, however the specs from the engine dyno don't tell me as much about the overall performance potential of the car as does the chassis dyno.... I've spent way too many hours using both types of dynos. The power numbers of the engine matched to the applied power numbers of a chassis dyno is the most accurate indicator of drive line and parasitic horsepower loss. Engine dyno results by themselves are little more then numbers used when R&D'ing the next engine parts combination.....And bragging rights at the coffee shop....

Hey, I have an idea. How about getting this truck to the strip and actually seeing what it does and then reporting back??

It will be interesting to see how close any of us were. I'm still betting it just cracks into the 12's. That isn't a slam, it is just that I know how hard it is to get a truck to run quicker than that, regardless of HP.


Don

Everybody thinks that thing will be a brick in the wind . i,ll bet it,ll post some potent 1/8 mile times though. And its way cooler than a camaro.Good luck with her and hope she runs like an arrow for you.

maybe it was spinning on the dyno too. but who cares what the dyno says its in the 9's , wow. fast ride!

thanks for all the help guys and I didnt mean to get everyone up in arms over the dyno thing my motor just came off the dyno this week and the numbers were
618 hp @6200 and 643 tq @4100 and the dyno guy said I should knock off about 15 to 20 percent for rwhp. so as soon as I can get this thing assembled and street worthy the first place its going is the chassis dyno then to epping and I'll be sure to put the slips up thanks again guys Jim