Dyno time

I had hoped to dyno the truck before headers, but covid lock down prevented that.

So finally book in next Thursday to see how the truck is doing, its a same shop I've been before and it's the same dyno where I had dyno other cars, so I have a baseline to compare with.

Question is, what gear should I limit the truck to on the pull?

 

4th. It's a 1:1 transmission ratio. Direct drive, so to speak.

 

You will want to:

1. pull the absII fuse
2. Put it in 4th
3. Roll into the throttle as if you’re trying to pass somebody. Aggressive, but not flooring it.
4. Listen to it shift gears. Pay special attention when you hit 4th.
5. In 4th at 3900 rpm, floor it!!! That’s your run.

floor it too soon and it downshifts. Don’t take off aggressive enough and it downshifts. Floor it too late and you get a false low reading. Consistently doing the above steps will result in a consistent control group. then, do the same steps after the modification and you have something to compare.

I hope you use a dynojet or a dynocom. While their numbers are higher than a mustang Dyno, they are the industry standard and it’s easier to compare your numbers to what I’ve seen during my hundreds of Dyno pulls.

 

It's a dynojet but not an AWD dyno, so will be dyno it in rwd.

got it on 4th gear, will set it in manual mode hold? or will it try to kickdown?

 

Set in S4 but don’t shift the lower gears. Follow the steps Keith mentioned above in post 3.

 

It will try to kick down, but it won't kick up to 5th. If you have a tune where you can lock it into 4th that'd help too. Stoked to see what you get, hoping to have mine on a Dyno soon too!

 

@Downytide I can't recall, are you using vF Tuner? There are instructions in one of the S/C PDFs that outline how to prevent downshifts for dyno runs...

 

Per Keith’s post - the way to avoid the downshift is to wait until you get up to 3900RPM in 4th gear before you floor it - roll into the throttle up to that point. That will get the RPMs high enough it won’t go back to 3rd.

 

Man, I need more coffee, I constantly read Keith's post as 4hi instead of 4th.

@dirtydeeds , where is the abs fuse? And is there a reason I have to pull it?

Nothing yet for 2021, this is a baseline so I can have as a reference.

 

Can’t help with fuse location on your truck but I believe you pull the fuse so the computer doesn’t kill power when you hit the speed governor.

 

If you don’t do the above steps it will either kick down or it will read low. Read the steps outlined above.

 

You also have to consider how aggressively you got to 3900. If you pussyfoot it til 3900 it will still downshift and blow the run.

you have to drive it as if you’re aggressively taking off from a light. Like 3/4 throttle. Then, at 3900 in 4th you can floor it. It comes fast and is easy to miss. It’s pretty much a talent to get accurate, repeatable numbers on a Dyno with a tundra.

 

It’s under the hood. The lid has all the fuses labeled. You have to pull it so you don’t have issues with torque management and or traction control.

 

Is that what I sometimes feel like power being held back when launching on the 1/4? I swear I sometimes feels like there's power being cut back even with all traction control off.

 

Yes. It’s very very intrusive.

 

Keith, I assume with the fuse pulled I'd get ABS light on, would it register a code if I drive around with that off for too long? cause now I'm tempted to head back to the track with that fuse pulled, it sounds silly, but the truck feel now like it can do a solid low 14s pass, the first 1/2 of 60ft it feels just "blah", then it rips like its an pissed off badger.

You mentioned ABSII, does that mean there's a second ABS fuse?

 

Once absII is pulled the ecu is blind to the speed sensors. That’s all that matters.

 

Would that also remove the speed limiter? cause right now I can't go pass 92-93mph (150km/h), does it work in 4hi as well? because if so, I'm going back to the track this weekend!

 

@dirtydeeds By not having it at WOT before 3900 RPM, won't that miss peak torque, which is noted at 36000 RPM? Or close enough?

 

I believe that ground speed is read via the ABS wheel sensors....so, I seems likely.

 

Will report back after the weekend.

 

Unfortunately, yes. You can only test above 3900 unless you gear lock with OVtune

 

Yes

 

A Dyno must be able to adjust it's readings if you tell it your gear ratio isn't 1:1? Or just scale the readings of a 3rd gear pull by it's transmission ratio? Is there more going on that dictates it must be 4th gear?

 

What matters more than anything else is that each and every run is done exactly the same way. Doing the before run one way, then the after run another way could show a gain or a loss of 40-50hp.

it’s common knowledge that you do your tundra Dyno runs in 4 th gear. Given this knowledge and the above procedures, one could compare not only their before and after results, but also the results of others whom have followed the above procedures.

a guy could do their run however they want. But 1/1 ratio and advice by a guy whom has done literally hundreds of Dyno runs with a tundra (me) will increase the chances of successfully achieving repeatable, verifiable, quantitative results.

 

So is there an actual reason to do a run in 4th besides "everyone else does"? It sounds like it's inherently a pain in the ass and you can't even be WOT at peak power/torque. Is there a reason it can't be done in a lower gear where you just floor it? If we're talking about being scientific, the method you proposed has a lot of potential for human error it sounds like, why is that more preferable than just mashing the gas in 1st for instance?

 

Anything other than a 1:1 ratio gives or takes advantage the same way that changing the differential does.

 

That's why I asked why that can't be accounted for in the prior post. Besides the gearing being different, which is a single variable and easy to compensate for (unless I'm missing something), I don't understand the hang up with 4th. I'm not trying to be an asshole, I'm just failing to understand or get a real answer, and will hopefully be dynoing myself in a few weeks so trying to learn.

 

Here’s what you want to do:

follow the directions above so that you can compare to everybody else’s numbers. If you come up with 500 Hp on your bolt on truck you didn’t do it right. If you deviate from the formula above you’re starting with numbers that you just made up.

Also, do it the same way each and every time. That way you have something To compare to when you decide if your new mod actually did anything.

that’s why. That’s your answer. The two answers in this post. Which were summarized from the answers to your other questions asking why in previous posts.

To summarize in one word consistency