Wait, now I'm confused. If the step is causing turbulence that dramatically reduces effective diameter, how does that not lose power?

 

We're all talking about theory. No one has yet to post up A/B testing showing said dramatic power losses. I'm guessing 1-2hp, but if I'm wrong then we'll port that sucker asap

*edit: I'm also pretty sure there's a step from the IM to the head, those are not perfectly port matched either.

We can re-dyno tonight if you want and see if it really did lose power

 

The step is not helping flow. Perhaps on a NA miata, the air speed through that spot is low enough that the actual reduction in flow is small (trivial, 1hp, whatever) but it's there. As mentioned a 30* change in temps is probably the main difference in your dyno numbers, but I'd still port match it.

 

waaait, I just thought of something!

Lets do a baseline, portmatch on the side of the road, then virtual dyno plot again!!! A/B test!

Pleaaaase??? I'll even buy the carbide burrs!

 

Then, when we find that it lost power, I can cry about it.

 

yeah that's what I'm getting at.
but I'm completely open to being proven wrong. I'll admit I don't know much about porting/polishing and intake resonance and all that voodoo
LET'S DO IT

 

It'd be cool if we could stop using the word "dyno" to refer to VirtualDyno guesstimates.

 

A dyno is a friggen tool. It shows you gains. Just like virtual dyno shows you gains. When you do a baseline pull, and then repeat it minutes later on the same road in exactly the same circumstances (we literally used a marker to start/stop pulls, doing them in the identical fashion every single time).

Are you trying to imply it is still a guesstimate vs you showing us dynojet plots which are usually within a couple hp?

Please

*edit: No one is arguing that this is better than a real dyno. But to call it a guesstimate is dumb in this case cause of the way we're doing this. One could even make the argument that the VD output is more realistic than a dynojet because the car is actually loaded up on the street like it is naturally, vs just spinning a drum. No offense.

 

Guys, guys, guys, lets keep this on topic.

 

The point of a dyno is consistency, not realism. Nobody is going to argue your point because it's not relevant to the discussion. If you're not taking VD pulls in a controlled space, then no, it isn't consistent. As to how much variation in wind/temperature/etc is OK before it starts affecting results in a noticeable way is not something I can comment on.

 

We were doing the pulls in a controlled space. As I've already posted.
The last part was just an observation, not an argument, hence my comment as well as disclaimer.

I'm not getting into a peeing contest over dyno's, It's pointless. OP can throw the car on any dyno he wants, I can even arrange a trip to the local mustang dyno if he wants.
I just don't appreciate the guesstimate comment is all.

 

This entire thread is prefaced on the notion that VD showed a 10whp loss by bolting a Skunk2 onto the car. If you can't see the blatant inaccuracy in that data, I don't know what to tell you.

Until it's capable of compensating for simple things like ambient temperature changes, in my opinion, it's a guesstimate. If you want to use it for direct A-B changes within minutes with calm winds on the same road on the same day, that's fine, but that's clearly not how it's being used.

 

Hey guys, my 1Hz SoC GPS that VirtualDyno uses is super good guys!

(cellphone GPS chips are incredibly noisy and bad if you want something that resembles accuracy)

 

cellphone gps chips? lolwut
Fair enough: OP just blurted out that statement which is clearly incorrect/inaccurate.
It does compensate for temp changes, I just totally derped and forgot to enable it. My mistake.

And that's exactly how it's being used, I keep saying that and people keep ignoring the posts that clearly say that.

Anyways, I'll just post up a proper comparison with all the data and we can all see if power was lost or gained and go from there.

I'm just as curious as everyone else regarding what power is gained or lost here.

 

Except for the part where that's not how you used it:

I'm sure VD can be used to obtain solid A-B data, but this entire thread is predicated on 100% bullshit data. That's where my "guesstimate" comment comes in, because if you're taking datalogs from different days and expecting it to be considered as "A-B testing", then "guesstimate" is about as nice a word as I can come up with to describe it.

 

We never performed controlled A/B test with matched vs unmatched squaretops & Skunk2 TB. I feel pretty confident that the step that exists hurts power though. Our standard recommendation for adding a Skunk2 to eliminate shaft breakage without gaining significant power is based on A/B from OEM to Skunk2 on an unmatched VICS manifold.

 

Ultimate butt dyno

Race-team owner Chip Ganassi almost comes clean in exclusive interview | Autoweek

 

I also port-matched my Squaretop to the Skunk TB...
https://www.miataturbo.net/build-thr...-62620/page24/





I recommend replacing the idle set screw and the screw that it stops against. They break and come loose.

 

I port matched my squaretop to the Skunk2 TB as well. As you can see there's a significant step around the perimeter and the after picture looks much more "flowy."

Before:




After:

 

The problem with the skunk2 is the return spring seem to break at about the same frequency as the OEM TB breaks shafts. The throttle sticks wide open when it does but at least you don't have to worry about sucking screws through the motor.