Discussion and questions related to the course Practical Dyno Tuning
I have had my dyno for a while but after my recent experience with an engine failure on the dyno (rb26dett spun main bearings after 5 pulls), my friend said its possible it was due to longer ramp rates that might stress the motor not sure if that's true. I was using 12kph (I usually use 10kph-15kph (avg 400-550rpm/sec) ramp rates. Most cars I tune are between 150WHP-550WHP(Mainline HP so about 177hp-650HP Dynojet/Dynopack).
Now for my question is, what is the general rule of thumb as far as ramp rates go? Thanks
The dyno didn't cause the bearings to spin. it's a good thing it was after 5 dyno pulls, and not 5-blocks from the shop on the way home, or two laps on the track the first weekend out.
I think the ideal ramp rate is one that the engine sees when the car is in one of the upper gears as seen on the track. This is usually about 400-500 RPM/sec, so I usually use 500RPM/sec to keep the math simple.
I had someone suggest to me that I should be looking at 600-650rpm/sec ramp rates but to me it seems excessive, even Mainline said that its pretty high. I know if the Ramp rate is too high its almost like running in inertia mode. I usually increase the ramp rate if I have traction issues as this can help on some aggressive spooling high powered FWD cars.
I also generally revert to 500 rpm/s as my go-to ramp rate. It gives a decent run length that adequately loads the engine and replicates the sort of combustion temps you're likely to see out on the road or track in a high gear. If you go too fast with the ramp rate it won't get you realistic results, particularly on turbo cars as it artificially means the turbo won't reach full boost until much later in the rev range.
In some cases with engines that are very knock sensitive, once I've finished a tune I'll do 1-2 runs with a slower ramp rate at around 350-400 rpm/second to really load the engine. If the engine remains knock free under this sort of condition then you can be pretty confident it won't give any trouble at the race track.
Thanks! I try to target 450-500rpm as well.