How to bypass decel valve?
 

Do I connect the two hoses on the back of the decel valve (#9) to each other or do I cap them both off? I removed the valve because it's faulty. I also removed the AAR (#4). Now the car won't start. Is it because I capped both hoses?

http://forums.pelicanparts.com/uploa...1252864467.jpg

Looking at the pic above, my car does not have #s 4, 5, 7, 9, 13, 14, 15, and 16

When I recently removed my decel valve, I removed all the hoses and capped-off all associated ports (including the tiny one on the throttle body) . . .

That's what I just did, along with the AAR and it won't fire. I crank it and it catches for a second and then dies.

cap all the connections that went to the decel valve.
since you removed and capped the cold start aux airslide valve you'll have to hold the gas pedal down about a 1/4" or so to let enough air in to start the car and keep it running.

you could install a porsche 944/BMW 320i plastic heater valve in place of the aux air slide valve. it fits the hoses perfectly and with a long cable would make a nice hand throttle for CIS.

all those silly throttle body air bypass devices do the exact same thing as holding the gas pedal down just a little bit beyond idle speed at certain times like decelerating (the saucer shaped deceleration vacuum limiter valve and saucer shaped AAR valve used on the 79 and earlier 930) so nitrogen dioxide emissions or NO2 are reduced and or at cold start ( the cast aluminum auxilliary air slide valve or whatever you want to call it today) so the motor will keep running without you feathering the throttle when it's cold.
they do nothing more than that... totally optional.

here's my 1987 saucer valve.
charming isn't it?

it lives in a box and will never go near my car again.http://forums.pelicanparts.com/uploa...1252867775.jpg

Well, I figured out why it won't start, I keep blowing the fuel pump fuse but I have no idea why. It ran before and I didn't touch anything electrical. I'm stumped.

I've blown that fuse in the past. I wonder if I have a bad fuel pump, both are original. $400+ for the pair, does anyone have an aftermarket source?

Do a search on ebay and amazon for current items and here's a link I saved.
The 044 pump is a good one, second down this list. I think you need to use an adaptor for the line connection.
I've seen it on sale for less so try a search.
http://www.boschfuelpumps.com/

Thanks. A little fuse blowing testing shows pump number one is the culprit. When I remove the relay (new) and run only on pump 2 it doesn't blow the fuse. I've been having power issues lately and now I'm wondering if this is related.

I know most want to remove the throttle bypass valve as they think of it as a smog device.

I have noted this before but it also helps minimize turbo stall between shifts in a way similar to the compressor bypass valve dose.

This helps keep boost up between shifts and makes things easer on the turbo shaft and bearings between shifts.

It also adds a little safety as if the CBV fails you will not be as likely to snap a turbo shaft.

The AAV is just a cold start feature.

If either are removed, yes, block them off and use clamps to prevent blow off.

I removed it because it is no good and I'm not spending $500+ to replace it.

...and you can just not let your foot off the accelerator all the way between high speed shifts and do the exact same thing without being married to it if you believe that theory.

along with that, by removing this emission device you get quicker deceleration of the engine during low speed around town gear shifts so the engine rpms match perfectly during casual upshifts making pleasent smooth driving.

and by golly you'll also have a much more stable idle speed with one less artifact from the early days of fuel injection thats just waiting for you to close the hood so it can play vacuum leak and mess with you.

All points to consider.

On a normally aspirated car I will be the first guy to pull the throttle bypass valve.

On a 930 I want it to work but would have a hard time paying $500 for a new one.

The best.

I removed all that stuff from my engine a decade ago. You learn to match revs between shifts very quickly and it becomes second nature. I like having that control to keep spool up when running through the gears at less than full throttle.

Well, it's definitely the front fuel pump causing it not to run. I disconnected the wires and checked the hot wire to ground and had nearly ∞ resistance. I then checked resistance across the fuel pump terminals. The reading was .5Ω Ohm's Law tells me that it's pulling 24 amps. I guess I'll start looking for a pump. The bad thing is the rear probably isn't too far behind (no pun intended).

I never had any issue on my 930 or C2 Turbo with the throtle bypass valve installed.

I learned of it's benifit from a respected 930 tuner may years back but there are more than one way to skin a cat.

I'm only pulling it because it's bad. I'd leave it otherwise, doesn't matter to me.

Well my front pump died in a different fashion. The "o" ring seal inside the housing gave up the ghost. First I could notice a slight gas smell, but could not find a source. Then a few days latter I saw a small drip on my garage floor when I
parked it that evening. Fired it up the next morning to go to the office....shower head city!! Man could not believe the volume of gas that could came out past that dead old "o"ring, glad it happened while at home.

I bought my pump through "Performance **********" new Bosch for $240.00 (sorry host) fit perfect, works perfect.

Mark

I dought it absoulity necessary for performance to pass air around the throttle body.

We just need enough bypass somewhere to minimized the Turbo from slowing down between shifts.

If boost gage drops between shifts enough that we can watch it build up- or you feel the power building back for a one or one-two count, then the throttle bypass might help to a degree. (And again, it s a little insurance if the CBV fails.)

On my car the combo of the TBV and a higher flow aftermarket Compressor Bypass Valve plus a couple of other tricks gave me instant full boost between sport shifts so I did not have to wait for boost to build back up helping me maintain higher average HP. However I mostly attribute that to the higher flow CBV.

In should say I have never tried running without the TBV. Again, I was told to keep the TBV by a respected 930 tuner.

If it works well enough with out it that is all that matters.

On a c2 turbo it would be a benifit to get rid of it if not needed just for the ease of removing and instaiilig the intercooler. I was wondering if it could be removed. I canned the aaa valve a while back as it is easy to just set in car and play with the throttle when cold.