I was wondering when you adapt mega squirt to a stock 86 rx7 13b, do you disconnect all vacuum ports and solenoids. eliminate the stuff like the dash pots and thermo valves and plug up the BAC? all the emissions? i know that if you leave the Bac on it is partially open and air is flowing through it.

the sample msq file on the ms website, what hard ware changes are required if needed?

 

Read the FAQ, it answers most of your questions....

Most people from what I've seen remove the emissions stuff.... and just tune the megasquirt to get decent emissions. That's what tofuball and I are doing on his 'vert (although we haven't tried taking it for emissions yet).

If you read the FAQ, you'll see that it's possible to actually USE the BAC valve... and no, it's not partially open if there's no power going to it, it's spring loaded and completely shuts without power.... I tested this on an S4 BAC and on an S5 BAC. tofuball and I are using the BAC on his car for idle speed control... During warm-up it provides a high-idle based on rpm (we have it set to 1800 rpms) and once warm, it keeps the engine at 800 rpms.

 

i disconnected the power to the BAC at this time. and pluged up any vacuum ports that bypasses air past the throttle plate. My efi tuning skills must suck at this point. i can get the car to idle but it surges from 1000 to 2000rpm. do you think the problem is in the constants or the VE table, or could it be a hard ware issue? im using the factory harness. i have it set up where i can just disconnect the stock ecu and plug in the megasquirt when im playing around with it. when i need to drive the car i just plug in the stock computer. req fuel is at 9.1 i think, 2 squirts, 2injectors, pw current about 65-85, been playing around with the numbers. pulse with thershold is at 2.0. i noticed that if i raise this number it seem the idle is a little better but at a rpm about 2000-2200. i also noticed that it does the same thing when i change from 2 squirts to 1 squirt per cycle.

any clues or hints on which direction i should go?

 

I'd use 2 squirts per cycle... and assuming you're using the fully stock setup, you don't want to have the injector PWM stuff set up.

You want to set the threshold to 25.5, and the pwm to 100 assuming you have left the stock injector resistor pack in place... I'm sure that'll help you quite a bit.

If it's still running poorly after that, the oscillation between 1000 and 2000 can be any number of things... most likely you need to tune the idle area in the ve table to be around 12.3:1- 13:1 AFR. Figure out where you want it to idle, and tune the 4 points around that so that they're all around the same number... I'd also use bins set up so that one of them is around 600, and the next one is around 1000, so you can more accurately bracket the area around the idle.

The ocillation is caused by the following series of events:

1) speed goes up, engine starts running lean at that point in the map...
2) because of number 1, the revs and vacuum drop
3) at which point the map is richer, so the engine starts running better again

These things will happen over and over again, causing the oscillations. The same sort of thing can happen with your spark table, and can happen if you're running closed loop at idle (the megasquirt will add and remove fuel to match the AFR you set.. which causes the oscillation).

 

Do you have the stock thermo-wax fast-idle device in place? If so, that'd explain the source of at least some of the extra air causing the 2000 rpm idle. The hunting can be eliminated by richening the mixture at the 2000 rpm idle area. Go to the tuning screen, and chase that bouncing ball with the cursor, and enrichen the bins in that area. You'll notice it smooth out immediately.

The 2000 rpm fast idle does seem a bit high with thermowas alone. IIRC, my old FC idled around 1600 rpm with the thermowax providing fast idle, and then dropped to about 800 after warm. You may want to check for other vacuum leaks if you've had the intake off since the conversion.

 

yeah the thermowax is still in there. when its cold the tps reads at 10% i think. I think i just have to play with the numbers. too bad the megasquirt couldnt highlight the VE box i was at bouncing around at. i know there is a 3D map on the tuning menu but it looks so small on my laptop. i'll get a chance later today to mess with it. i must say this is pretty fun. reminds me of tuning my weber Ida ten years ago. that seems so much simpler now.

 

ok i just realized you could raise and lower points on the VE table on the 3d graph under the tuning section. cool. still surges. when i change required fuel to 15 seems that the surging minimizes to within 500 rpm. it sounds like it stumbling because it too rich though.

i tried adjusting the VE table around the bouncing ball.
as rpm goes up it runs into a lean spot on the map, which vacuum drops and rpm drops. falling back to thr rpm where it is rich, causing rpm to go up, vacuum goes up. When vacuum is low, do we want more fuel? and when vaccum is high we want less. somehow i need to balance this, right? this is gonna take me a while.

 

You can start off by just playing around with the req_fuel number, as it is simply scaling the entire table. Once you get a feel for how far off you are in the idle area, go back and re-set the req_fuel, and manually scale those entries in the idle area.
Watch the bouncing ball during these idle surges. Enrichen the bins around the top of the ball's travel. You should immediately here a change in response, where the rpm drop is not so agressive. BTW, you want to do this with a warm engine, as warmup enrichment settings will change things as well during that phase of operation. Is the car drivable in it's present state?
The tuning process is very well documented at megasquirt.info. Unfortunately, it appears to be down at the moment, but check back there later, and have a good read.

 

Sounds like exactly what I said... I'd richen up the upper spot, and lean out the lower spot a bit until the oscillations calm down.. I'd also put your rpm bins closer together around the idle... and try to bracket the idle rpm area in between those rpm bins...

 

ha!! i found my idle problem. the wire i was using for tach ref had a break in it. the connection was good enough to run but was causing my rpm signal drop off causing my surging problem. i changed it out. now megasquirt idles smoothly i think it idles better than my other car, stock turbo II.

 

ahh, well it's good that you found the problem.