brillo

I was wondering if we could control our idle speed by installing a small air bleeder screw after the TB to raise and lower the idle RPM in conjunction with the interceptor.

I know that if we tried this stock, the ECU would throw a sh*t fit, but since the Interceptor can control the fuel and timing, could we make it work?

Can the stock DBW TB actually close all the way? I’m trying to think of what the car would do if it saw more air. This would be an easy mod, one that could be easily reversed (especially if it is a screw type) or you could just epoxy it back.

epitrochoid

why would you want to do that?

brillo

because adjusting the speed is a good way to smooth the idle out. The interceptor will allow you to richen the idle mix, which will help also.

Rasputin

Brillo,

It won't work. Whatever you do, the PCM will compensate by closing the throttle. The more air you'll let bleed in, the more the PCM will close the throttle. Until it is fully closed and still measuring air coming in => CEL.

Limit your action to fuel and spark to start with. You might see totally acceptable results!

Fabrice

Moostafa29

Is there any other way to make this type of adjustment. If the engine could idle at like 1k, it probably won't bounce around so much.

rotarygod

I do know that if you remove a vacuum cap from the manifold, idle will go up and the ecu will not compensate for it. One way we got the car to idle smoother with the Megasquirt was to richen the mixture from the high 14's where it is now to almost 11:1. This made it nice and smooth. Brillo wants to get this smoothness without richening it up. While making the mixture richer does mean more fuel consumption at idle, so does a higher idle rpm.

brillo

Rasputin mentioned he had an idea for how to control the idle with a aux rpm dependent switch, which the interceptor has two of.

Hopefully he will expound on his idea here.

Rasputin

Hi Brillo,

My idea was the following. Basically, it's done by cheating the PCM about the ECT. At 65°C (IIRC) the idle speed is 1000 RPM.
So, the principle is to use your RPM dependent switch (set to open under 1025 or 1050 RPM) to drive a relay that would feed a resistance corresponding to 65°C ECT to the ECT signal pin of the PCM. Using a potentiometer (variable resistor) would enable you to fine tune the idle speed.

This idea is compatible with all the conditions of engine operation I can think of :
- Cold start : Idle starts at > 1500 rpm so no influence until we reach the switch speed (at 67°C ECT) where a 65°C signal is fed to the PCM.
- Normal driving : nothing happens above switch speed. If you underrev it at 1000 rpm, you'll get fuelling an spark for a slightly colder ECT, nothing that can damage the engine
- Idle : when you release the gas pedal, the systems enter into idle mode and the idle speed decrese progressively. Here, the speed reduction will be clipped by the device.

The only drawback of this device is the engine temp gauge on the IP will dip slightly in idle. But you know why so no stress!

Fabrice
-

Rasputin

Someone on the French forum identified a possible issue with this idea. It concerns the actuation of the radiator fans.

Fabrice

brillo

couldn't we just create a switch to keep the fan on at all times?

rotarygod

By fooling the ecu into thinking the engine is still a little cooler, it is also richening the mixture up slightly. It doesn't just add more air. At 150*F or so it is somewhere around 10%-15% richer than at 180*F which is the fully warmed up temperature threshold. May as well just adjust richness at idle if that's the case and hold it at the regular idle rpm.

epitrochoid

I still don't see the need for this. My idle is not rough, and most people can correct rough idle by adjusting the maps through the intercetor.

If your question reagards other applications, I think you should move this thread elsewhere in the forum.

BigOLundh

iTrader: (1)

If you can't adjust the fan with the interceptor... this might help
https://www.rx8club.com/showpost.php...3&postcount=26

-hS

MazdaManiac

iTrader: (3)

It will dip a LOT. Like, to just a notch over cold. Not that it matters, its just freaky. Also, you will get no cooling fans at idle - not a good idea if it is warm or you are coming off of a hard run.
I suppose you could hook the same switch to the cooling fans, but now you have a whole bunch of weirdness happening at once. Maybe a second thermostat for the fans?

Moostafa29

Not everyone has had their car tuned by the designer. I am have made several adjustments, but still have a problem sometimes.

brillo

We have to much brain power here to not figure this out, there has to be a way to do this.

epitrochoid

well have you at least exhausted all the tuning fixes that might smooth the idle?

and FWIW, scott never changed the idle setting. it's smooth as hell except if the AC is on. then its rough for 2-3 seconds every 15-20 seconds

swoope

iTrader: (5)

dont know if this will help, but it is something i noticed. if there is a way to trick the ecu into thinking the car is still moving the idle will stay at 1k rpm .

i noticed that with the new flash the idle will not drop till you stop. i had a flash on a bmw motorcycle that did the same thing.

beers

Rasputin

You should read all the posts before posting MM.

Fabrice

MazdaManiac

iTrader: (3)

Often, I hit reply and then walk away from the PC for an hour or so before I type. By then, new stuff comes in.

Moostafa29

Yes

TeamRX8

iTrader: (25)

I may be off-base, but putting a single screen 2" ahead of the MAF solved the issue on my NA homebrew CAI. It's dead steady smooth as butter now even though it is an extremely short ram tube (temporary until the final long version is completed). In fact that's all it is; 2" of tube past the MAF centerline with a huge cone filter on the endwith a screen at the tube entrance.

I posted the screen material info/source in the general Aftermarket area. The 3.5" OD ram tube was donated to me; previous attempts to run it open caused the CEL so it was withdrawn from the market. I haven't had any issue at all with the screen in place and I even cut 2" tube off the end of it making it even shorter and still no issue. The idle was jumping all around and it threw a CEL without it installed. May not apply here so perhaps just FYI.

rkostolni

I don't see much of a point to this either. My idle w/ the intx is completely smooth. Much better than stock. Unless the AC is on. But, there is a setting to adjust fuel % whenever the compressor kicks on. With some tweaking there its possible it could be remedied.

drifter_d

my results are the same as reported by rkostolni ^^^

dd sends...

Rasputin

????!!!!!

F