What no BISS?

[cheekychimp]

The aftermarket throttle body I have, has no BISS adjustment. Are they so well designed that idle should just fall into the 700-900 rpm range or, if not, how do people set base idle with these?

 

[Terry Posten]

Does it have a set screw for the throttle blade?

Like the old carbs?

 

[iLLeffeKt vr-4]

Some use the throttle stop to adjust it.

 

Yep, on my BBK the throttle stop is a screw, and that is how you set your idle.

 

[strokin4dr]

Paul, are you still using an ISC on that throttlebody? If so, you can use your dsmlink to set the idle properly.
-Ryan

 

[gtluke]

if its a ford throttle body, ford actually made an insert between the TB and idle motor that is a BISS for problematic cars. some aftermarket companies replicate them as well.

 

[cheekychimp]

It's actually a Wilson Manifolds throttle body, modified by Jackson to fit the Forrester Manifold. I believe it does have that throttle stop screw you mentioned. You adjust that so that the throttle plate does not completely close, that is what you are saying right?

Strokin, we were looking at the throttle body last night and have decided we can get it machined to accept the OEM ISC, but doesn't setting the idle speed through DSMLink and ISC still rely on a correctly set BISS or throttle stop in this case?

 

[toybreaker]

Paul, does this throttle body have a closed throttle switch?

The ecu requires a closed throttle switch in order to control the isc.

Without it, the ecu won't know you want it to control the idle.

 

[strokin4dr]

^ If you have the values for your TPS setup correctly with dsmlink you can simulate the closed idle switch, so that is not a problem with his setup.

Paul, there is nothing wrong with the adjusting the throttle stop to get closer to your target idle; BTW, how far off is if? If it is not far off and you get the TB machined for a ISC then you could easily use dsmlink to find a target idle. So either way, or a combination of both, depending on what you are idling at now, will work. (Having a ISC for other reasons too will make the car feel more refined and less like a "racecar" /ubbthreads/images/graemlins/wink.gif)

-Ryan

 

[grocery_getter]

You do not need an isc or an idle switch to set up idle. DSMLink is well equipped enough to get around this. I did it with a stock TB, I did it with a Q45 TB with a Nissan TPS and I did it with an Accufab TB with a Ford TPS. All done with dsmlink.

Run the car as is and adjust the mechanical throttle stop to place your warm idle rpm where you want it. Go to dsmlink and click simulate idle switch. Adjust your tps so that you can read 10% or .5v at without touching the throttle pedal, after that is accomplished, adjust your throttle cable slack so that you can get 100% tps or 5v when you press the pedal all the way to the floor. Don't over pull the throttle cable or you'll bend and snapped that throttle shaft someday. Make sure you still have a hair of slack at the throttle cable next to the TB when the pedal is not touched to account for thermal expansion/alien landing/stock price drops etc.. It is also a good idea to fab a throttle stop on the floor so that you can really avoid snapping that flimsy throttle shaft when you stab that throttle hard and swing the butterfly plate past where it supposed to stop.

This is all done with the key at the ON position and motor not running off course. You just need the ecu to be ON so you can communicate with DSMlink.

The only reason for me to suggest someone to keep their ISC functional is if they still have AC. It helps with the rpm drops when you have AC system turned on, especially when its in the evening when the headlights are also turned on.

Hope that helps...

 

[grocery_getter]

I forget to say that without the ISC or FIAV unit hooked on the only issue is cold start. YOU will now become the human choke, aka, sit in the car lightly pressing the throttle pedal to lightly raise rpm to 1500pm to help with cold start. After the coolant temperature raises a bit, idle should stabilize enough to the point that you can let go of the throttle pedal. The stock fuel map is a bit richer when temp is down, so you'll have to manually introduce the air that usually gets there via FIAV and ISC. Now if only dsmlink can do fuel trim based on coolant temp.

 

[cheekychimp]

Andre,

That was excellent! I have to keep A/C. A tropical climate and no A/C would mean only driving the car three months a year. Consequently I may still go with the ISC, although that isn't set in stone. We also have a fast idle valve that operates off a relay that we may use and link to either coolant temp or the A/C compressor switch to get us past this issue.

Paul.

 

[iLLeffeKt vr-4]

I ran without a FIAV/ISC for a long time in my car. It idled like a dream once warmed up and even in cold weather I only had to keep my foot on the throttle for about a minute or so.

However, once I built the motor and installed the BC 272/272 it didn't like it anymore. No matter what I did it didn't want to idle. I played around with the BISS, the idle switch, the TPS, DSMLINK, throttle cable, simulate idle switch, etc. Nothing worked. Idle was either too high or too low or sometimes it would just shut off as soon as the fan would come on. Sometimes it would work fine for a day or two then go haywire.

I couldn't take it anymore and I put the ISC back on. I set the TPS, BISS, and idle switch and its been fine for the past 6mo now.

 

[grocery_getter]

If you can make that aftermarket FIAV to leak in a bit more air in conjuction with AC operation then you are set for the tropical climate there! The only reason you can't do it with stock FIAV is only because our FIAV is completely dependent on coolant flow only. I might be visiting HK for my sister in law wedding in December but that's not set in stone yet.

 

[Rausch]

^ That is exactly what he is setting up to do....He should be good to go.

Now I still say put the 840's in if you're going to drop in the link.....Rather than set it up twice, but that's just me. /ubbthreads/images/graemlins/tongue.gif

 

[atc250r]

What about a solenoid valve that will let a little extra air into the intake whenever the AC compressor is running? Maybe one of the emissions vent solenoids? It'd just have to be plumbed back into the intake tract after the MAS in order to avoid a lean condition when its open.

John

 

[cheekychimp]

John,

That's exactly what this valve I have is, we were just worried about two things a) How it will stand up to seeing positive boost pressure when the throttle plate is open? and b) How it can be adjusted if the amount of air it bypasses is too large?

Paul.

 

[atc250r]

You could get a small, brass gate valve and put it in-line between the valve and where it connects back to the intake tract. I looked for a pic online but I didn't see anything. Any hardware store in the U.S. has them for a couple of dollars. I thought I remembered you mentioning that you were going to use a solenoid but I wasn't sure. LMK if you need me to pick up a valve and mail it to you. I can get some from work but they will probably be a little bigger than you'd need but they'd probably work quite well.

As for the solenoid dealing with the boost, how much are you planning on running?

John

 

[cheekychimp]

John,

Realistically on the street maybe 22-23 psi. Motor is supposed to be good for 35 psi (9.0:1 compression). The valve sounds good, can you get smaller ones than the ones you have at work?

 

[atc250r]

I can get you a picture of one from work next to a ruler as a point of reference so you can decide if you really need a smaller one. It might be good to stick with a larger valve as it will allow you do bleed off a little more if you need to.

John