I feel a sudden urge to drill a hole in my m-tuned rail and install a damper.

Thought on everything you just posted:

NA miata's had no damper, but had regulator on fuel rail.

NB miatas' had regulator far from fuel rail, and had a damper close to fuel rail.

Doesn't a fuel pressure regulator act as a damper in some way? If so having it closer to the fuel rail would help.

Just some thoughts, I dunno I've never measured fuel pressure on my car.

One last point- in the same log you just posted, AFRs are rock solid. I wonder if the AFRs between cylinders are too?

<p></p><p>Dibs on it, when you inevitably&nbsp;screw it up and buy a new one? ;)</p>

NBs have *two* dampers, one on the rail, one on the fender. The regulator has to sense the drop in pressure and mechanically adjust for it, the more volume there is after it, the larger the lag introduced before it can do that. Putting the regulator on the rail gives it very little lag, so it can respond to injector events more quickly.

AIUI, wideband O2 sensors don't have the response time of a lot of other sensors. The fuel pressure sensor I'm using will do 1KHz, widebands aren't anything like that. That's part of the reason it appears more solid, but yeah, I'm concerned about pressure drop for individual injectors making individual cylinders go lean.

--Ian

I will continue fuel discussion in your new thread: https://www.miataturbo.net/engine-pe...5/#post1244814

First you need a BP ;)

Something like this maybe?
<br />
<br />https://www.miataturbo.net/attachmen...ine=1435625052

We should stop flirting in Ian's thread, unlike the rest of us he's getting real data and solving real problems. https://www.miataturbo.net/attachmen...ine=1435630882

:)

I pulled the trigger on the Radium unit, we'll see how it does.

--Ian

Shiny (well, anodized) new parts showed up today!

https://www.miataturbo.net/attachmen...ine=1435899210
https://www.miataturbo.net/attachmen...ine=1435899210

Off work tomorrow, maybe I'll put it in then.

--Ian

<p>Isnt the selling point of the radium that it works with rising rate FPRs, which yours isnt?</p>

shhhh!!!

Mine is.

--Ian

I thought it wasn't vacuum referenced?

When I first installed it, I did not hook up the vacuum reference. Later, I did, as you can see in the photos in post #275. :)

I talked to FM about why they recommended not referencing it, they said that because it's a long run from the manifold to the regulator, the regulator will lag the boost rise and it can make lean tip-in worse. They also suggested that at 12-15 psi (standard FM2 levels of boost) the referencing isn't really necessary, because with a base pressure of 60 psi it's still getting 45 psi pushing the fuel through. I'm running a teensy bit more than 12-15 psi (currently set at 24, gonna see if it'll do 30 once I get it to the dyno). That means there would only 2 bars pushing fuel through the injectors, which is a bit low.

Thus, I ran the vacuum reference line.

--Ian

Haha a tinsy bit more 24.... Thats awesome hope you get your issues sorted out ;)

So things on the Miata got stalled for a couple of weeks. We got the keys to our new house, and I spent a couple of weekends doing stuff related to that, rather than the Miata. A nice big, paved side yard perfect for trailer storage!

https://www.miataturbo.net/attachmen...ine=1437289941


Today, however, I got back to looking at the fuel, and plumbed in the Radium pulse damper. I decided to mount it on the rubber mounts from the factory pulse damper, so first I needed a bracket. (This is actually the second bracket, the first one turned out to not be long enough). It's just 1/8" thick 2" aluminum angle with a few holes and a corner chopped off to make room for the 90-degree hose end.

https://www.miataturbo.net/attachmen...ine=1437289941

Then the FPD mounts on the bracket with some loose hose ends to check for alignment.

https://www.miataturbo.net/attachmen...ine=1437289941

The pressure sender remote-mount hose needed to be flipped around, so the 90 is now next to the sender.

https://www.miataturbo.net/attachmen...ine=1437289941

Hoses made and fitted:

https://www.miataturbo.net/attachmen...ine=1437289941

Feed lines:

https://www.miataturbo.net/attachmen...ine=1437289941

So ideally I want the pulse damper mounted in the feed line to the rail, but right now it's actually mounted in the remote line for the pressure sensor, because I didn't have the right fittings to do it properly. I'll order those and reroute it later, but right now it works very well indeed. The pressure swings are maxing out at around +/- 2 psi, vs the 15 psi I was seeing before. Yes, the pressure sender probably isn't seeing everything that's happening at the rail due to the routing right now, but I did have the damper in the feed line briefly (just hacked up for testing) and it looked the same there. The weird ringing at idle is totally gone, and I'm VERY pleased with it.

https://www.miataturbo.net/attachmen...ine=1437289941

So my takeaway from this is that FM's big fuel kit needs a pulse damper. I don't know if the stock damper would accomplish the same thing, or if it really needs to be the fancy vacuum-referenced radium one.

The car will now do a 270 kpa run to redline smoothly, without the major stumbling I was seeing before, although there is still a little blip in that datalog which may be a misfire. 270 kpa is probably asking a lot of the Toyota COPs. :)

--Ian

<p>Remind me why you didn't simply&nbsp;move the referenced FPR to just downstream of the fuel rail, as in at typical referenced, return style system.&nbsp;</p>

He has an NB so he would have to convert to return style fueling.

Making a -6 return style system would've required a lot of new hose and fittings that I don't have, several hundred dollars' worth. It would also preclude the use of the stock rail, requiring a lot more parts to be swapped out for California's biannual "regulatory" reasons.

--Ian