Chassis Dyno Tips?

[NHRA Super Gas]

I'm going to try to hit the dyno this week, and I seem to recall several things you need to do/think about when on the dyno.

1. I remember locking the converter making a difference, although I don't think I want to unless it's a must. Seems like it would be a false positive of sorts.

2. How do you avoid the car downshifting into 2 from D when you floor it? Unhook the cable perhaps?

3. Any thoughts on the correct A/F ratio specific to a dynojet?

Thanks in advance,

EW

 

[Roc87]

1. I locked my converter, can't tell you if it made a difference, locked it each run.

2. DO NOT disconnect the cable, that controls how much pressure is in the tranny, perhaps someone with a little more "vocabulary" will help out here. Mine downshifted and they just ignore that area on the chart/they don't start it recording until they heard it shift to 3rd.

3. Can't help ya there. I tried making mine richer than 12.9 and it started backfiring when I'd let off the gas.

Good luck and post the #'s!

 

[NHRA Super Gas]

Great, thanks. I haven't even looked to see if the TV cable is the only one going to the trans, luckily this car has been somewhat plug and play for me.

 

[SloGN]

when i dynoed my car a yr ago i had to run the speeds up to 70+ before i could nail the throttle so it would not down shift and spin the tires on the rollers. I would shoot for a A/F around 11.4-11.5 with leaded gas. If your going to tunes on alky i would shoot for 10.9-11.0 A/F just to be safe.

I locked the converter in my car and it didn't seem to hurt it or help it.

 

[turbodave231]

Strap the car down good. make sure the fan is blowing right into the radiator with the hood down.

If you are running slicks, air up the tires to 25 psi or so.

AFR's should be 11.5 to 11.75 on gas.

DR

 

[TurboJoe3.8]

Good Luck and let us know how you make out

 

[bison]

With a BR vb you should be able to go WOT at 61 mph or so with no kickdown from 3rd to 2nd. Lock converter for highest numbers possible. Alky and pump gas 11.0:1. Alky and c16 11.3:1. You could go a tad leaner but it becomes more of a risk.

 

[bobc455]

Are you going just to see how much HP/torque you make? Or are you also going to tune while you are there (i.e. change a/f ratio, change timing, etc.)?

3. Any thoughts on the correct A/F ratio specific to a dynojet?

Why not try a few and see what gives you the best torque? (remember that torque is more important than HP)

If you are going for the purpose of tuning, disregard the first run of the day. It always gives higher #'s than subsequent runs. Also, if you make changes, remember to compare the entire torque curve and not just peak torque.

-Bob C.

 

[bison]

If you are going for the purpose of tuning, disregard the first run of the day.

-Bob C.

Not in my experiences. Almost every car ive seen was way to rich for peak hp. Last time i dynoed i picked up every run. Ive picked up 56hp and 75ft/lbs at the rear wheels. Ive seen over 300hp gains in a dyno session.

 

[NHRA Super Gas]

Results!

OK, just got back, not bad I would say:

First hit was base 19/20 lbs boost, base fuel curve, 5.5 on the alky knob made 370HP 448TQ at the wheel. Not locking converter.

Last hit was 24/25lbs boost, plus 5% fuel, 6.5 on the alky knob made 411HP 544TQ. This was good air, the uncorrected numbers were actually 424/563.

One thing I noticed was the A/F curve starts at say 12.5 at 3K RPM and comes gradually down to below 11 at 5K RPM. As it dips below 11 you can see the power fall off considerably. My guess is the progressive alky is sort of drowning the motor a bit at the very high end, and I might need to tweak the controls under the dash?

I think there is still some more power to be had, but all in all I'm not disappointed.

 

[V6POWER]

Nice numbers but did you have any knock? I always thought that we should shoot for an afr of 10.9-11.3 with 93 octane + alcohol. Were you running race gas + alcohol?

 

[NHRA Super Gas]

Knock...See my other post too!

We did see some knock and it was hard to decide if it was real or not, especially with AF ratio coming down instead of up. Could have been rich knock, rather than lean since the AF above 5K RPM was about 10.9 or less. I'm definitely looking for people's experience on that.

This was straight meth and 100 unleaded Sunoco.

 

[bison]

I hit peak power at 11.3-11.5:1 on 110 octane and a little methanol . Going from 10.2 to 10.9:1 was worth 34 rwhp. All in all i picked up 56hp going from 22 psi to 24.5 psi and adding in 2 degrees timing (26 degrees total).

 

[Boost231]

We did see some knock and it was hard to decide if it was real or not, especially with AF ratio coming down instead of up. Could have been rich knock, rather than lean since the AF above 5K RPM was about 10.9 or less. I'm definitely looking for people's experience on that.

This was straight meth and 100 unleaded Sunoco.

are you saying you had 10.9 Knock or less?

 

[NHRA Super Gas]

no AF was in that range. But we did have some big knock numbers, they were not real. See my other post on that.

 

[Boost231]

no AF was in that range. But we did have some big knock numbers, they were not real. See my other post on that.

ok good. i just read the post again. makes since i dont know what i was thinking.

 

[Razor]

Never unhook the TV cable. You'll burn up the tranny.

Your Air fuel at upper 10's isnt a problem, and usually power starts to drop off past 5k especially on stock motors. Your factory cams are only like 200 degree's duration.. if you want the motor to breathe past 5k.. then you need a roller cam and some flowing heads.

The alky is used for knock suppression. Your to only use enough alky so the knock sensor doesnt go off, more than that doesnt provide too much of a benefit. And when you see false knock, your ECM cant tell if it is real or false.. so it will pull timing robbing HP.

Anytime you drive on and off a dyno it was a successful event

 

[NHRA Super Gas]

Thanks razor, this car has 206/206 cam and champion irons, so I would think we could pull past 4k. What I'm interested in hearing is from your experience, should my A/F ratio be as inverted as it is? What I mean is starting at 12ish at 3500 and moving to 10ish at 5000, shouldn't it be the otherway around? I had previously thought I might be out of injector but now it's more the opposite, i'm giving it too much. I would think I need to "flatten" this curve to be 11ish the whole way, 3500-5500+....thoughts?

 

[salvageV6]

Most stock motors make those numbers at that boost level.

I think the knock, real or false, pulled some timing.

With a heads and cam. motor I'd want about 100 more HP.

Locking the converter might help.

Dyno. is less of a load than the pavement, I'd try 11.5 on the wideband.

Gotta get rid of the KR for sure to make a clean run.