How to bypass decel valve?

[mooney265]

does it hook to the lower or upper connection of the decel valve?

[Speedy Squirrel]

OK, there's alot of questions here:

BeepBeep - "Which cars open idle valve on deccel?" An example that I have seen recently is the 2004 Dodge SRT4. After '04 most cars switched to ETC. There is no more IAC. In current cars the throttle is held a little further open with the ETC to produce the same effect. The 2004 Porsche Turbo is one that I have seen in that category.

For modern cars, the ability to shut off the fuel enables the IAC or ETC to be open further. Otherwise you get a big RPM flare when you add air to all that fuel. That is the CIS "lazy throttle" effect. Keeping the manifold vacuum from getting too low is good. When you get back into it there is less time needed to build boost back up.

IAC's are too slow? I don't think so. Maybe the big old Bosch rotary ones on the original Motronic? I don't know about those. I have a GM IAC on my EFI conversion. I "clocked" it tonight. To go from 10 steps to 150 steps takes only 0.55 seconds. More modern LIAC's like the later Motronic systems are even faster, and ETC is faster still.

This is way off track from the decel valve issue though. To summarize:

Decel valve is good because it limits manifold vacuum. A high vacuum manifold is an empty manifold.

Decel valve is good because it can dump some of the pressure spike during shifts before the bypass system can react.

Decel valve is good because it burns the fuel injected by the CIS, which some claim might help turbo response. We know for sure that exploding it in the muffler certainly doesn't.

Decel valve is bad because it can fail, and fixing it costs money, maybe more than it is worth.

[JFairman]

if you mean my thought of adding a second adjustable blow off valve where the deceleration valve was plumbed in it would go to the upper hose connection from the intercooler or intermediate manifold and either vent back to the turbocharger intake pipe downstream from the CIS air flow meter just like a C2 or use an adjustable one that vents a little to atmosphere if you like the chirping and wooshing sounds.

that ebay one i linked to is a joke. i googled noisy blow off valve for it.

there are much higher quality blow off valves out there and probably over 50 different ones to choose from.

[JFairman]

speed skwirl.. i think everyone that has tearfully removed their golden saucer valves should mail them to you asap so you can build a temple for all of them and worship them faithfully.

[mooney265]

Originally Posted by JFairman

if you mean my thought of adding a second adjustable blow off valve where the deceleration valve was plumbed in it would go to the upper hose connection from the intercooler or intermediate manifold and either vent back to the turbocharger intake pipe downstream from the CIS air flow meter just like a C2 or use an adjustable one that vents a little to atmosphere if you like the chirping and wooshing sounds.

that ebay one i linked to is a joke. i googled noisy blow off valve for it.

there are much higher quality blow off valves out there and probably over 50 different ones to choose from.

I'll pass on it, anyway... Definitely too loud... Need to keep the popping to a minimum in the neighborhood...

[beepbeep]

Originally Posted by Speedy Squirrel

OK, there's alot of questions here:

BeepBeep - "Which cars open idle valve on deccel?" An example that I have seen recently is the 2004 Dodge SRT4. After '04 most cars switched to ETC. There is no more IAC. In current cars the throttle is held a little further open with the ETC to produce the same effect. The 2004 Porsche Turbo is one that I have seen in that category.

But "Throttle-By-Wire" is no idle valve. It's a servo-controlled throttle. The same exists in SAAB 9-5 and is mapped to open little further than requested to mask turbo lag. It's also closes quite slowly in order to keep emissions low...which is very annoying as revs shoot upwards between shifts when clutch is depressed (even when throttle is released). This can be mapped away in the software.

Once again, this has nothing to do with turbo longevity or decreasing spool time...this is purely emission strategy, and annoying one to boot!

[Speedy Squirrel]

You asked for which cars open the IAC, and I gave you an IAC example and an ETC example. You also contradicted yourself in the same statement, first saying it "masks" turbo lag, then claiming it is "purely emissions strategy". This thread is getting pointless.

Fairman, I will take all the decel valves you can send, as they are worth 500 bucks apiece!

[RarlyL8]

If you want the popping on decel to stop completely you use another manual method, your left foot.
The more CIS equipment you remove the more participation required to operate the car as if all the equipment was still there. This is not for everyone.

[beepbeep]

Originally Posted by Speedy Squirrel

You asked for which cars open the IAC, and I gave you an IAC example and an ETC example. You also contradicted yourself in the same statement, first saying it "masks" turbo lag, then claiming it is "purely emissions strategy". This thread is getting pointless.

Fairman, I will take all the decel valves you can send, as they are worth 500 bucks apiece!

Yes. It "masks the lag" by overshooting throttle opening when you press on the pedal. It virtually opens throttle more than you wanted. This on other hand has nothing to do with idle valves or engine braking vacuum limiting as it happens in accelleration phase and not deccel.

And I still say: deccel valve's only function is to limit popping on deccel....that's it. Turbo couldn't care less as it's protected by BOV.

Further: there are no cars with idle valve which is opened by ECU on overrun. There are cars which close their servo-operated throttles in lazy manner and there are dashpot-dampers on throttle levers. But no stepper-valves opening on overrun.

The only sure-fire way to eliminate popping is to either install EFI or to use feature introduced in KE3-Jetronic: EHA-actuator which quickly raises controll pressure on overrun and thus shuts down flow into to engine.

[mooney265]

The only sure-fire way to eliminate popping is to either install EFI or to use feature introduced in KE3-Jetronic: EHA-actuator which quickly raises controll pressure on overrun and thus shuts down flow into to engine.
__________________
Thank you for your time,
Goran

Goron, where would I locate an EHA-actuator and is there any thread on how to install?
I did a search on the "word" and came up with nothing...
Thanks, Shannon

[RarlyL8]

The only time the TBV has noticeable effect on turbo spool between shifts is when it is malfunctioning and hanging the idle. This is what I described earlier that I do intensionally with my right foot, hang the idle between shifts to help maintain momentum of the spool between shifts. The idle drops faster when the TBV is removed so the desire to manually over ride is increased. This is a bi-product of the TBV's function to reduce chop throttle exhaust gas burn. You can see this in action yourself when manually hanging the throttle. The burble or pop is eleminated just as it is by pushing in the clutch.
A faulty BOV can manifest itself in ways that are sometimes blamed on the TBV, and vice-verca, such as the jerky "engine brake" or "teeth in windshield" as Goran calls it. Many CIS components do similar things, have similar functions, which can hamper troubleshooting.

[beepbeep]

Originally Posted by mooney265

Goron, where would I locate an EHA-actuator and is there any thread on how to install?
I did a search on the "word" and came up with nothing...
Thanks, Shannon

It's a no-go for "classic" K-Jetronic unless you can hack something yourself. I included this just as an example of why popping occurs and why deccel valve is there. EHA is basically a electrically controlled valve which bleeds off controll pressure according to what computer says (=further development of lambda frequency valve used on US cars, on early CIS).


I assume that you could program the DWUR to quickly raise control pressure for RPM>1500RPM and MAP <30kPA. That would do the same trick. One way or another, you have to have programmable electronic which keeps tabs on MAP and RPM.

EHA is black thing on CIS head:

[mooney265]

that's a good idea on the DWUR... Maybe one more reason to go in that direction...