NZ951

Hey team, just want to check something...

When removing/deleting the ISV, we take a line from the brake booster and join that straight to the manifold, then cap the other port on the manifold, and any IC pipe plumbing right?

Also, would there be any advantage to keeping the ISV when big injectors are involved? Or are they not related in an idle sense?

dmoffitt

idle problems re: injector size comes from having such a low% / short duration 'duty' that they can't open/close fast enough to properly meter the tiny amt. of fuel @ idle. the ISV meters air, and yeah, while you need the proper mixture of air and fuel, i would think that your biggest idle problem will be due to injector sizing more so than the ISV. what size are you using btw?

NZ951

850cc... Ummmm I can adjust the pulse width etc with the Link...

Looks like the ISV is gone burgers!

tazman

My understanding is if you remove your ISV you are going to have a rough idle when the engine is cold which has nothing to do with what size injectors you are using.

NZ951

Thanks Tazman. I am going to remove it, will clean up under my intake nicely! No oil lines to the IC pipe, CV, or ISV! Was the plumbing I described above correct? One line from the brake booster to the manifold and blank off the other?

tazman

Yes the line that was going to the ISV from the intake manifold can just be blocked off.

NZ951

Sweet. I will post pics once it looks all pretty. I love my catch can!

OriginalSterm

Not sure if it would even be a problem, but as dmoffitt suggested, the opening and closing response may try and overlap each other with a small duty cycle and the injector may not work properly. But again, it may not be an issue. We'd be talking a duty cycle of less than 5% probably. If there is a problem with idle, can't you just set the idle a little higher to bring up the duty cycle?

B951S

Andrew, my Link shows 1% when warm with 55# injectors at idle, there is plenty of room to go lower on the duty cycle if need be so you'll be alright. If you set your warm idle high enough manually, you should be able to keep the engine idling when cold / with AC on etc. It may be a bitch keeping it running after starting on hot nights when the lights are on, and the AC/blower is on as that really bogs the motor down. Trial and error should get it sorted. Only donwside is that you might need a pretty high idle when warm to compensate. Can't wait to see some pics bro.

NZ951

Hmmmmm I dont use AC that much... In fact it is not hooked up to the Link as the turbo is... That will change when I put the 60-1 in. I dont mind warming the car up before I drive, as long as it does not stall. Should not be too far away with my projects. One at a time...

NZ951

ISV is now gone, my car runs so much better! Idle is fine from cold, I think my ISV may have been bung.

tazman

How can you have good idle at cold and warm temps with the same amount of air going into the engine?

NZ951

I have the screw up al the way, and idles at around 650 when cold for maybe 3-4 mins, then at 850-900 when warm. That was my experience this morning. My MAP is set at around 89-90 in the idle zones, IIRC.

NZ951

By the way, does anyone know with the brake booster plastic connector is just for a vacum tap? Ie there is no special valve mech inside it?

tazman

I think there is a one way valve in there to keep vacuum for the brake booster. My 88 TurboS has one without the extra vacuum connection on it so you could probably upgrade to the newer part. Thanks for the info on how the car idles without the ISV.