In reply to Robbie (Forum Supporter) :
At lower speeds where aerodynamic drag doesn't come in to play, it can be remarkably accurate as a way to calculate horsepower.
If you can calculate how many G you are accelerating by speed/time/time, and know the weight of your car, you know how many pounds of thrust there are at the tires. If you know the tire radius and gear ratios, you know how much torque is at the engine.
Of course, what's really more important than "engine power" is "quicker acceleration" so all that math is irrelevant compared to knowing that a change shaved (or added) 2 tenths to a 3000-6000 2nd gear pull.
There's a free windows program called Virtual Dyno that is just for that, you need to do logs with your ecu/datalogger showing throttle position, rpm and time (you can add others but that is the minimum), input a bunch of vehicle info (weight, drag, gear ratio etc) and it will spit out a dyno graph for you. If you get all of your inputs perfect the results should be quite accurate. Even if your inputs are off though provided the test environment and all those inputs remain the same you'll get a very good comparison to see if/where you have improved. Here's some more info on it
The key is finding a flat, straight road where you can make your pulls without drawing attention. I typically prep a few tunes ahead of time and then go out and do the pulls finishing up with the one I started with to bookend the runs with the same tune to see how consistent things are.
dps214 said:
That's right, I glossed over that initially. Hand stroking can give you an indication of something being really wrong, but that's about it. The hysteresis that was felt could be a problem or it could just mean the damper was laid on its side recently. My memory is a little fuzzy but iirc non pressurized dampers also generally take longer to cycle oil back into everywhere than gas charged ones do.
Yes, twin tube shocks often need to be cycled a few times in a vertical orientation before they really start to work.
Peabody
MegaDork
2/21/25 11:28 a.m.
Andy Hollis said:
As mentioned earlier, he said proprietary blend -- dino juice, not synthetic -- 5W. Suggested just use whatever 5W you can find.
I suggest you use a shock fluid and not a fork oil, or at least a very high quality suspension fluid. I like Redline but there are other good ones. The SAE W designation is archaic and doesn't work for suspension fluid, but it does give you a general starting point. By that I mean that there are big differences between manufacturer's oil that is designated 5W. The spec should always be in cSt at 40C or 100C depending on the application
A good general guideline on oils here
Keith Tanner said:
dps214 said:
That's right, I glossed over that initially. Hand stroking can give you an indication of something being really wrong, but that's about it. The hysteresis that was felt could be a problem or it could just mean the damper was laid on its side recently. My memory is a little fuzzy but iirc non pressurized dampers also generally take longer to cycle oil back into everywhere than gas charged ones do.
Yes, twin tube shocks often need to be cycled a few times in a vertical orientation before they really start to work.
I have seen (inexpensive) twin tube shocks break the pistons off if they weren't cycled before being installed and driven.
Pete. (l33t FS) said:
In reply to Robbie (Forum Supporter) :
Of course, what's really more important than "engine power" is "quicker acceleration" so all that math is irrelevant compared to knowing that a change shaved (or added) 2 tenths to a 3000-6000 2nd gear pull.
yeah, the math is fun but "measure what you treasure". You're simply trying to reduce time to get from rpm x to y. So measure the time directly and then reduce it.
In an x1/9, luckily there is plenty of time to consider your methods while waiting on rpm y.
Really good point to cycle them by hand a few times before install. I'm also getting fresh bumpstops (vw Jetta/golf ones are very cheap) before install.
