RossD said:
I know it is cooler to have it computer controlled but what about a progressive throttle. The first 2/3rds operates the usual throttle body and the last 1/3 does the VICS ones (or whatever they are called). You could have a heavier spring on it too so you could feel the added force required.
But if MPG is the end goal, MS would probably be the smarter way.
The VICS butterflies are not throttles. They open up another chamber in the intake manifold, increasing the volume and thus changing the resonance. It's pretty easy to figure out when they should open, just do one dyno run with them open and one with them closed. Where the lines cross, you change. It's right around 5700 rpm. No need to waste an MS I/O on this, just use an RPM switch.
Ah, I knew I had this chart. Blue has them closed, green is open, red is controlled.
https://www.flyinmiata.com/tech/dyno_runs/99_050400.pdf
Some people have claimed that hollowing out the intake so that the VICS butterflies effectively provide a short vs long intake path will make a difference, but in my dyno testing it did not.
Keith Tanner said:
The VICS butterflies are not throttles. They open up another chamber in the intake manifold, increasing the volume and thus changing the resonance. It's pretty easy to figure out when they should open, just do one dyno run with them open and one with them closed. Where the lines cross, you change. It's right around 5700 rpm. No need to waste an MS I/O on this, just use an RPM switch.
Ah, I knew I had this chart. Blue has them closed, green is open, red is controlled.
https://www.flyinmiata.com/tech/dyno_runs/99_050400.pdf
Some people have claimed that hollowing out the intake so that the VICS butterflies effectively provide a short vs long intake path will make a difference, but in my dyno testing it did not.
^This
I did something similar several years ago when I inadvertently bought a Volvo Variable Intake System (VVIS) equipped engine to replace the non-VVIS engine in my 850. It's vacuum actuated, so an RPM switch, a solenoid valve, some plumbing, and some wiring were all that was needed. I semi-retired the car about 6 months ago, but the Lee-ified VVIS still works.
I wrote about it long ago on a Volvo forum:
https://www.matthewsvolvosite.com/forums/viewtopic.php?t=30281
In reply to RossD :
After running the engine for an hour and then letting it sit for a few hours, the crap that came out of the cooling system really wasn't that bad. There was no chunks and the vinegar was a medium color brown. I'm not sure if the vinegar needed more time or the cooling system really didn't need cleaning. Anyway, the car runs exactly at 195 F now.
Here is a section of the datalog file that shows the engine temperature. The temp ramps up to 212F and then bounces around a bit and finally settles at a solid 195F. I know, its hard to get excited about stuff like this, but I'm really happy with the way the temp stabilizes. The old engine the temp would wonder from 140 to 215.
In reply to Keith Tanner :
Thanks! You saved me a whole lot of time!
....Because yesterday I went ahead and build a little hand held switch circuit and started fooling with the VICS.... After about an hour I had a feeling the VICS didn't do much at part throttle or in cruise.
Hand held VICS controller and butt dyno confirmed Keith's inside knowledge of all things Miata.
Somewhat interesting, when opening and closing the VICS at low RPM the A/F will bounce a bit before settling. I have no idea what is going on.
Stay tuned!
In reply to bigdaddylee82 :
Awesome writeup! Thanks for sharing!
Looks like the RPM switches can get a bit pricey. For now I'm going to let the megasquirt trigger the VICS at 5700 RPM for datalog purposes. .
FunkyCricket said:
That's a neat picture.
Thanks, I wish I knew about this camera feature a long time ago.
OK, One more update, I forgot to mention I have been using the car to commute these past two days. Today when I topped off the tank I was mildly surprised to find out the car managed to get 36 MPG.... not too shabby.
Stay tuned
Doc Brown said:
OK, One more update, I forgot to mention I have been using the car to commute these past two days. Today when I topped off the tank I was mildly surprised to find out the car managed to get 36 MPG.... not too shabby.
Stay tuned
Ok, forgive me for being a little slow here. I've been following along, but can you summarize what you've done so far? Seems like you have gotten to 36mpg pretty quickly. I normally get about 25mpg in my NA8...
In reply to AWSX1686 :
Whelp, I wish I had an answer because I didn't really do jack E36 M3. The tune is still in its beginning stages and the tune is for power not economy. Let me clarify that statement... The tune doesn't waist fuel unnecessarily...My rough draft of the tables keeps the engine happy at cruise and well fed at WOT, or in other words, the Megasquirt more or less keeps the engine in stoich except at idle and when you hammer it.
Although this is now 'just another Miata', the car defiantly isn't stock. Perhaps the 3.90 axle and the RX-7 5th gear plus the El' Cheapo 4-2-1 header and the Obnoxiously noisy lightweight Yonaka exhaust. My commute includes a 30 mile stretch of expressway and the modified gear set certainly helps.
In reply to Doc Brown :
Ahh, I forgot you already had modified 5th gear, I'm sure that helps a lot. My commute is about 30 miles each way, mostly highway, but it goes over 2 mountains so my miata is generally revving a bit to keep up with traffic up the hill.
So just to try and list it out:
-MegaSquirt ECU + Custom Tune, not tuned for efficiency yet.
-Modified 5th Gear
-3.90 Rear End
-Cheapo 4-2-1 Header
-Lightweight and Loud Catback.
That really isn't a whole lot to be getting that good of fuel mileage. I am impressed! I'm sure driving technique has a lot to do with it as well. Once I find a new NA or NB to daily I may have to look into the rear end and 5th gear mods and see how far I can get on a stock ECU. Keep it up, I appreciate the info your builds provide!
Yea, the final and 5th gear change is something I’d like to do, too. For summer driving, I’d always get 30 mpg in my ‘99. Those two changes should drop the engine speed enough to make a huge difference.
AWSX1686 said:
In reply to Doc Brown :
Ahh, I forgot you already had modified 5th gear, I'm sure that helps a lot. My commute is about 30 miles each way, mostly highway, but it goes over 2 mountains so my miata is generally revving a bit to keep up with traffic up the hill.
So just to try and list it out:
-MegaSquirt ECU + Custom Tune, not tuned for efficiency yet.
-Modified 5th Gear
-3.90 Rear End
-Cheapo 4-2-1 Header
-Lightweight and Loud Catback.
That really isn't a whole lot to be getting that good of fuel mileage. I am impressed! I'm sure driving technique has a lot to do with it as well. Once I find a new NA or NB to daily I may have to look into the rear end and 5th gear mods and see how far I can get on a stock ECU. Keep it up, I appreciate the info your builds provide!
That is the basic list. Let me add some items that may be subject to debate but are different from stock.
The EDIS-4 crank trigger ignition.... While I really don't think the EDIS is better that the stock crank trigger that was on the engine, the EDIS is connected to the Megasquirt and the Ignition table is different. The odd thing about the ignition table was poached from the B3 configuration and was slightly tweaked to accommodate the larger RPM band.
The throttle body heat plumbing was deleted. My experiments with the smaller B3 engine indicated positive results for both power and economy when the throttle body was not heated. An argument can be made about this mod, but with the smaller 1.3 engine the heat hurt performance and economy suffered, however with the larger 1.8 engine, I don't have any proof that this is a righteous mod.
Oh, the cam sprockets..... They currently should be dialed in for factory spec cam timing, but I pretty much eyeballed it so who knows...
In reply to alfadriver :
I'm real happy with the 5th gear and the 3.90 but the holy grail may be the 5th gear set and a 3.63. Its hard to say how much low end would be lost with the 3.63 on a street driven Miata.
In reply to Doc Brown :
3.63, 5th gear, and a turbo could be pretty sweet if you can keep your foot out of it... Most of the time in 5th gear probably wouldn't be in much boost, then you'd have it when you need it down low. Just dreaming here...
In reply to Doc Brown :
That’s where the Rx7 gear set would fit, making 1-3 almost the same with 4 & 5 a lot taller.
Would you care to share your target AFR table? I can't keep my foot out of it long enough to get good gas mileage (250whp will do that) but I'm curious to see what your cruise cells look like all the same. Some guys on Miataturbo.net have had luck going leaner than stoich under cruise.
morello159 said:
Would you care to share your target AFR table? I can't keep my foot out of it long enough to get good gas mileage (250whp will do that) but I'm curious to see what your cruise cells look like all the same. Some guys on Miataturbo.net have had luck going leaner than stoich under cruise.
I'm trying my best to keep my foot out of it as well..... it's not easy
. On the expressway the car runs between 2900-3100 RPM. On a flat stretch of highway the car will run 70+ mph @ 10% throttle.
In reply to Doc Brown :
Why so rich in idle? My cruise cells are almost identical to yours, so I suppose that's good. I'd pull more fuel if I had an EGT, because it still seems to run fine, but with the turbo I'm putting enough heat through it as-is.
In reply to morello159 :
Idle quality is much better if you run a bit rich.
You should be able to get it to idle very well at stoich. You may have to use ignition advance to control it.
Doc Brown said:
In reply to morello159 :
Idle quality is much better if you run a bit rich.
I'm with Keith - mine idle is rock solid at 14.7, but my closed loop idle controls advance and the IAC valve.
In reply to morello159 & Keith Tanner:
I took Keith's advice and set the idle to 14.6. I'm still fiddling with it, but without idle air control it may be a lost cause.
I missed something, why is there no IAC? I was able to run it on a car with four throttle bodies. Makes a big difference, especially when the engine is cold.
Doc Brown said:
In reply to morello159 & Keith Tanner:
I took Keith's advice and set the idle to 14.6. I'm still fiddling with it, but without idle air control it may be a lost cause.
Use spark. Like more of it.
In reply to Keith Tanner :
No IAC on this engine, I took it off and blocked off the hole. I may put the IAC back in, but it will be a while. Anyway the car was not wired for IAC because I couldn't fit it on the smaller engine that previously occupied the engine bay.
