in search of the smooth idle

[linuxman51]

....without an idle speed motor. This wasnt such a big deal with the old setup, but has been something of a dance on the 16v. Since some people have posted about getting their cars to idle smoothly, I figure'd i would post this up to provide a little help and insight.
This also does wonders for consistency (assuming the rest of your hardware is up to the task).

I had some info about it in my FS thread, but didnt actually get around to putting mine on my car until today. The "map bomb" (sam named it, after he blew an endcap off his and thought his motor had come appart). on the best of days the kpa signal at idle would cycle up and down from 33 to around 37 or so (maybe not that bad), which would then cause twitching with the pulse widths (mmmdamnit), this in turn led to changing afr's at idle (boo) which would induce further twiching and/or rpm changes, and all of a sudden you've got an inconsistent idle.

So I threw my map bomb on my car (made in december, lost for about 2 months, found, lost, and found again today, and promptly installed), turned off tpsdot, turned on mapdot, and maaaaaaan the accel is so nice and smooth. but back to the idle...
now at idle the map is at a constant 34. no jumping or shifting, and at 8psi, it holds the 8psi line, not the 5-10 skew with 8 in the middle that really makes tuning a bitch.


so if you havent made one, they come highly recomended. take about 6 inches or so of 1.5 or even 2 if so inclined, pvc pipe, get a couple caps that fit it, and two vaccum nipples.
Put the nipples side by side on one side of the canister, install, have fun (oh and do glue the caps on, otherwise you'll scare the daylights out of yourself and others nearby when one does blow off).

[MikeSr.]

So this dampens out MAP fluctuations? Any pics available?

[kyle242gt]

A-HA! I'd been wondering if you'd forgotten to explain that to those of us in the trenches.

[linuxman51]

So this dampens out MAP fluctuations? Any pics available?


yes and not yet (heh)

[benflynn]

to smooth out the idle i just made all the bin the same where it idles, if it searches around the afr's stay constant, but this fixes the mpsdot accell, i was trying to get my accell fixed yesterday but i gave up, my tps dosn't seem to register the slight changes

[ovlov760]

seconded for pics.. on and off the car.
Does this hook up to the two hoses that the IAC would have? Does it help with cold starts?

[linuxman51]

to smooth out the idle i just made all the bin the same where it idles, if it searches around the afr's stay constant, but this fixes the mpsdot accell, i was trying to get my accell fixed yesterday but i gave up, my tps dosn't seem to register the slight changes

that doesnt work for me. I tried that, and shockingly it didnt fix my issue (yeah, i know, wtf?!)

no this goes inline with the map sensor line to the megasquirt box.

[The Aspirator]

Wow, isn't THAT interesting. I can picture exactly what you're talking about. Does it still react quickly enough to pressure changes? I guess it would, wow that's pretty genious. Did you come up it or did you get the idea from msefi somewhere?

Could you post up your mapdot settings? I've never been able to figure out how to tune that. We can't easily fit a TPS to Erik's car so it's been running a crappily tuned mapdot for a year now.

[Morley]

I had to do the exact same thing to keep my boost-gauge from vibrating into death at idle...

[peanut]

I'm wondering if you could achieve the same effect by putting a small constriction inline before the MAP sensor, or is there a good reason not to??

[linuxman51]

I'm wondering if you could achieve the same effect by putting a small constriction inline before the MAP sensor, or is there a good reason not to??

i suspect you could, some experimentation would be required, and it might not pulse dampen as much.

[malloy1]

So, you place this thing inline with the vacuum line for the MAP? Does it look something like this:


http://www.brickboard.com/GALLERY/images/6082.jpg

[linuxman51]

So, you place this thing inline with the vacuum line for the MAP? Does it look something like this:


http://www.brickboard.com/GALLERY/images/6082.jpg


yeah just a lot shorter.

[ovlov760]

I made one of these today. It does seem to work and actually helps my cold starts. The car will start and idle on the first try rather than the 2nd. Does it matter how long the hose is from the mapbomb to the ms map sensor? Cus I mounted my mapbomb down near the overflow reservoir.
http://www.cramptonstation.com/mapbomb.jpg

[kyle242gt]

And then you can tell your buddies its for the nozzzz

[ovlov760]

And then you can tell your buddies its for the nozzzz
I was gonna tell them it was a boost catch can.

[linuxman51]

I made one of these today. It does seem to work and actually helps my cold starts. The car will start and idle on the first try rather than the 2nd. Does it matter how long the hose is from the mapbomb to the ms map sensor? Cus I mounted my mapbomb down near the overflow reservoir.
http://www.cramptonstation.com/mapbomb.jpg


longer hose will add "lag" to the map sensor, but nothing other than that. it doesnt have to be that long, you could cut most of that off.

[ovlov760]

The pipe is 6" in length but the caps add to the length. I'm thinking of moving it behind or under the glove box.

[JohnLane]

I made a nice even idle in my six with telling Electromotive to give a fixed pulsewidth with the throttle closed at idle speed. Dial in the mixture at idle (I shoot for 2% CO) and enter the value.
Are you guys taking your signal for the map sensor from a runner or a plenum? Runners have all the pulse ugliness all the time to screw things up. Big plenums tend to be our friend.......
JL

[PetesDustyVolvo]

I made a nice even idle in my six with telling Electromotive to give a fixed pulsewidth with the throttle closed at idle speed. Dial in the mixture at idle (I shoot for 2% CO) and enter the value.
Are you guys taking your signal for the map sensor from a runner or a plenum? Runners have all the pulse ugliness all the time to screw things up. Big plenums tend to be our friend.......
JL

John,

I'm only gonna say this to you because I saw you ask if people were taking boost signals off a runner in two different threads now.

Knowing that turbobrickers are the laziest peopl on earth, how many redblock intake manifolds with extra vacuum nipples coming out of the runners have you seen? ;-)

[The Aspirator]

how many redblock intake manifolds with extra vacuum nipples coming out of the runners have you seen? ;-)B21FT. BA-ZING!

[JohnLane]

Knowing that we are in Turbobricks+intersnet-land I never just assume that people would know better then to tap into the really easy one that feeds the brake booster on most old turbocharged (AKA B21ft) four cylinder Volvos...... Would you?

Careful with the sarcasm...... I've been doing this for more then a few weeks now........

John if it will help I can show you how to fit a TPS to your throttle body that will make a .5 to 5 volt signal. That is a problem I solved for my car using Electromotive......

[PetesDustyVolvo]

Knowing that we are in Turbobricks+intersnet-land I never just assume that people would know better then to tap into the really easy one that feeds the brake booster on most old turbocharged (AKA B21ft) four cylinder Volvos...... Would you?

Careful with the sarcasm...... I've been doing this for more then a few weeks now........

John if it will help I can show you how to fit a TPS to your throttle body that will make a .5 to 5 volt signal. That is a problem I solved for my car using Electromotive......

lol oh i didnt know the B21FT had one

[The Aspirator]

Yeah the stock B21FT manifold is a peice of garbage design, JL I sincerely hope you don't think I'm running one! :). I've got a B230 intake mani, so there was little problem adapting an 850 TPS to it. Erik on the other hand is using the plenum style B21F intake mani, and when using a B230 throttle body there's lots of things in the way when it comes to mounting a TPS, so we haven't yet. We need to either figure out how to mount one, or build one of these potato cannons. Accell enrich is the only real problem he's experiencing with mapdot, it's way finnicky.

[linuxman51]

I made a nice even idle in my six with telling Electromotive to give a fixed pulsewidth with the throttle closed at idle speed. Dial in the mixture at idle (I shoot for 2% CO) and enter the value.
Are you guys taking your signal for the map sensor from a runner or a plenum? Runners have all the pulse ugliness all the time to screw things up. Big plenums tend to be our friend.......
JL

from the back side of a b230f/t intake (where the other vaccum ports are). its still "noisy".

same with the 16v intake, and its more of a plenum style.

[JohnLane]

It sure seems as though our four cylinder toys could benefit from a bigger plenum......
Are you guys running enough cam for this to be an issue with it making vacuum at idle?
John the TPS I've fitted to my V-6 takes up the same space as the OE thing that had WOT and Idle switches.......Seems like something like it should be able to find it's way into your sled......