Dyno Question?

[MTCFORUM]

First, I realize that when you buy a chip “off the shelf” it is a generic version. It hopefully will show an improvement but is not quite the same as an “on the dyno under a load” tune. Even though all similar engines receive the same hp rating from the factory there are slight production variations “or factory freaks” as some people call them. This post is not to discuss which is better, running the engine under a load while tuning should be a no brainer.

Second, there are two different reasons to use an in-ground dyno. First is to see how much rwhp your vehicle actually puts down, you know bragging rights (LOL). The other is the true reason and that’s to actually tune the vehicle under a load.

Finally, my discussion point….on a manual transmission car you simply place it in its 1:1 drive gear and mash the throttle till the numbers quit climbing. With the throttle wide open you can get a smooth pull from 1000 to 6000 or more rpms without any slewing of the numbers like an automatic. On an automatic Ford transmission you have the ability to put it in second gear and run a similar profile like the manual only it’s in second instead of a 1:1 gear. I guess my main question is while trying to get a smooth acceleration curve using drive, the 1:1 gear in an automatic, does it handicap the curve or final numbers to accelerate from a lower rpm with the transmission in drive since you can’t actually open the throttle all the way until you are past kickdown points of the automatic?


P.S.
I'd really rather have the dyno tune but the question is based on the bragging rights part (ha ha).

Bill

[MTCFORUM]

You're right, that is a problem. So, in order to get the real numbers from an automatic transmission car, you need to lock the transmission in the 1:1 gear. Thankfully we have electronic transmissions so this is easy to do with the right tools. Also, you need to lock the torque converter clutch to keep the converter from multiplying torque before reaching its stall speed so it won't give you bogus torque numbers. This too can be done with the right tools.

Without the tools and know how to do this, there's 2 ways to get at least some data. One is to use manual second which will throw the HP numbers off, but we are really interested in making sure the air fuel ratio is safe, not max HP numbers. You still have the unlocked converter problem unless you happen to have a calibration that locks the converter at WOT, but if it's a stock converter or close to it, that's not too big of an issue. The other way is to not start the pull in 3rd gear until the RPMs are high enough that the transmission will not downshift and the converter is above the stall speed. This gives the correct HP numbers up high, but you can't get the lower RPMs this way.

Then there's my problem. Too much power, so the torque converter clutch just slips even when commanded to lock. Since it's a 4k RPM stall speed, I can't get good data below 4k RPM. Fun huh?
KD

[MTCFORUM]

Kris is correct. You give up about 3% more in 2nd gear rather than 3rd, not a big deal. I do not tune a car to an absolute power level, that's meaningless. I tune to an a/f ratio that I want. If you are someone like me and Kris, then I go for a less conservative a/f ratio. If it's someone else, I usually shoot for a little more conservative.

Then I start to tweak spark to look for gains in power. Add a few degrees across the board and look at the power. If it's up everywhere, that's good. It may up in some places but down in others. You play with this and see what happens.

For the most part, I know what it takes to make max power from a spark standpoint on a 2V or a 4V naturally aspirated engine. The quesion is do you have enough fuel octane, plug heat range, thermostat, to run at this spark value?

We found in NYC that JohnnyN was running off the knock sensors for the total dyno run. This means if he put in better spark plugs (which he is going to), he will pick up some power since his engine will now be less knock sensitive. Steve's car did hit the knock sensors around the torque peak, in the low 4000 rpm range. He'll gain some torque, but not peak HP with better plugs. Both cars would have problems in the summer with the knock sensors taking timing out.

jerry

[MTCFORUM]

Oh, and Kris, you just need to block the converter regulator valve in the open position and run line pressure to the converter. With the 9.5" converter you won't balloon it, so you need more pressure.

jerry

[MTCFORUM]

Yeah we talked about that. I'm going to have the clutch in the converter replaced too, since I feel like it will need to be cut open anyway and loosened up for changing over to the torqueless wonder 4V engine

[MTCFORUM]

Kris,

I know first hand how you can get inacurate numbers from the dyno. I was rated at 156rwt the first time I went to the dyno. Not quite right for a 94 SC. <IMG NAME="icon" SRC="http://images.zeroforum.com/smile/emwink.gif" BORDER="0">

I see from the posts that you can hold the car in second and adjust the results (3% per Jerry's post). But how do I get the converter to lock without a chip or a tuner? What tools are you talking about, or is it not really needed since I have the stock converter?

LEt me make sure I understand everything, I should get the low-end numbers (torque) in 2nd and get the high RPM numbers (HP) in 3rd. Thanks,

Paul