RobC7

Lots of good information in this thread but also lots of misinformation.

- Megan y-pipe is 2.5" on the inlet side, 3" on the outlet side (this is bad if you have it mated to a 2.25" or 2.5" mid pipe - ideally you should replace the Y for an H/X pipe)
- Tabane axleback is 60mm = ~2.36" (however, since it mates to the stock midpipe it actually tapers down to ~2" or less by the inlet)

A little bit behind schedule eh?

Rochester

iTrader: (9)

Three years, apparently. Other mods got priority, and kept pushing the tune down the list.

Do you think the tune will affect the sounds of the engine & exhaust? Seems that was my opinion a few years back.

m3clubracer

I take it that you believe the tune is less important and that the tune can effect the exhaust note? Just wanting to clarify.

Rochester

iTrader: (9)

Take it however you want, but it wasn't entirely a calculation of what mods are more important. I mean, plans are flexible, that's what makes them plans and not commitments.

If you're curious on mod decisions, I do actually track all this stuff, and try to keep mod money in the ballpark of $2k annual. So in 2018 I had a lot of maintenance, repairs and tires, where adding the cost of the tune was just too much that year. In 2019 I had poly motor mounts installed, and purchased an expensive brake upgrade. And in 2020 I had the new brakes installed, had some PDR and maintenance work done, then laid low during the Pandemic. Throughout it all, life happens, budgets and plans change.

Even the tune has been budgeted and planned out. Here's the thread: https://www.myg37.com/forums/ecu-tun...ng-ecutek.html

Re. exhaust note... over the years here, and a handful of meet-ups, I've had this opinion that the tune can affect the sound quality of the G/Z. Right or wrong, I don't know. Guess I'll find out soon enough for myself.

rotarymike

iTrader: (4)

Makes sense if the tune affects exhaust or intake valve lift.

Rochester

iTrader: (9)

That would be interesting.

I'd like it to sound like a Ferrari. Or half of a Ferrari.




jk jk. All I really want is a little extra grunt in the midrange. Anything else is a bonus.

rotarymike

iTrader: (4)

I think I misspoke - the VVEL changes duration, not lift - or does it change both? Not sure. Regardless - valvetrain voodoo. Anyone know if this is changed in a normal tune?

For the Ferrari experience - you need individual throttle bodies. More than half of the noise of an exotic is due to the ITBs. It's doable on any engine, but an engine like ours that computer-pilots the throttle plates to mostly open when running (and uses the VVEL to throttle) would be more difficult to get just right.

SupraOfDoom

I just did a e-tune through Z1 so I don't have any numbers to give. I plan on going back for more power in the future, then I'll go all out on the dyno/e85 etc. And yeah my exhaust is probably my favorite mod, and I got a hook up on it .

m3clubracer

I did this over the weekend. I was able to get 5 and one was from a Frontier and was larger than the two from the Y pipe and the two from in front of the mufflers. I put mine in nearly the same place in the Y pipe and mufflers (I have resonated Megan DP's, fleabay Y pipe, and Flowmasters) and the top end RPM at WOT it makes all the world of difference. I have the large one from the Frontier at the Y split to the dual exhaust. I will need to get two more to place on the DP as the low RPM low load still resonate (buzz) at 2500 to 3200. Thanks again for passing this along, it does work.

SonicVQ

You are absolutely correct, it does change the exhaust sound, and here is why.
The G37 runs rich at wide open throttle (like most factory calibrations) , with the air/fuel ratios (AFR) in the low 10s. This is done to reduce the temperature of the catalytic converters.

The tuner will change the WOT AFTs to the mid 12s. This ratio is known as "rich best torque" or "lean best torque" depending where in the 12s the mixture is.
AND with a change in AFR, there is a change in the "flame speed" or how fast the frame front inside the cylinder travels from the spark plug to the edges of the cylinder.
(Note: this change in AFR/Flame speed also requires a change in ignition timing to maximize cylinder pressures at 12-14° after top dead centre TDC)

The faster the flame speed, the "sharper" the exhaust note. (more of a rapid cracking of a whip)
A very rich mixture (< 10 AFR) has a slower flame front and the exhaust note will sound "softer" and will actually be quieter.
(see digram at the end)

If the vehicle has a catalytic converter, this change in exhaust note may be difficult to hear, but it is there

Rochester

iTrader: (9)

(If you do this, then you have to do that, and if you do that, then you have to do this other thing... LOL)

Good post, Sonic! And that change in timing, is that why tunes for the G/Z typically require bumping up from 91 to 93 octane?

I'm hoping to hear some results this week. Pun intended, having reached out to AT to start the remote tune a couple days ago, and still waiting for response. Very anxious now.

SonicVQ

In the VVEL system the valve lift and duration are mechanically linked. You can not have a small valve lift with a long duration.

The graph below shows the valve lift and duration of the VQ37VHR.
Looking at the lowest (dark blue) line, when the VVEL duration is 25° Cam, the valve lift is about 1mm.
and on the other side, a VVEL duration of 70° Cam results in a valve lift just over 11mm.



Depending on the engine mods, the tuner can modify the VVEL system as well as the VTC (variable cam timing) system.

TL;DR
• Valve lift and duration are fixed
• Yes, the tuner can modify the VVEL & VTC systems

rotarymike

iTrader: (4)

Ooooh. That's some solid technical voodoo.

SonicVQ

Thanks! I often wonder if I get too deep in this stuff and bore everyone... BUT I can't help myself, I just LOVE to dig into the small details.

rotarymike

iTrader: (4)

Make a tech thread if you need to. There's enough of us that are interested and either somewhat educated on the engineering basics or interested to learn.

I mean, I made a flow bench back when so I could make sure my rotary engine rebuild ports flowed the same... I get it.