bypass valve doesn't open in 2nd gear

I installed my capristo exhaust about a week ago and wired open the bypass valve, the car sounded amazing at any speed. Long story short, today I unwired the valve and noticed it never opens in 2nd gear at any rpm. Seems to be working great in every other gear. I never noticed this with the stock exhaust although I could never hear the valve open in stock form.
Is this normal? Why the heck won’t it open in 2nd gear?

 

It opens at a higher RPM in 2nd gear for European noise regulations or something like that, strange that yours isn't working in 2nd but in every other gear.

 

It doesn't seem to be just RPM dependent, I can push and back off the throttle and hear the bypass open and close. Try doing a run in 2nd where you progressively get into more at different RPMs.

 

Yes, RPM and throttle position dependent but 2nd is different from the other gears. He should still hear it open though, somewhere around 5000 RPM I believe.


Rob

 

80 percent throttle position and above 2800 rpms in 1,3,4,5,6
80 percent throttle position and above 4000 rpms in 2

The triggering of the valve is handeled by the ECU sending a signal to a switch to allow vacuum pressure to hit the valve.

 

This is interesting I'll have to give it a try in 2nd and pay attention to the RPMs. I thought I got over 4,000 but maybe not. I can really hear it open with the capristo exhaust, honestly I would like to leave it wired open I just don't dare with what others have said it can do to the engine.

 

One thought about that. The concern about damage to the cats/engine is based on the mixed path between the upper and lower outputs on the headers. The capristo keeps these two paths totally separate so wiring open the bypass would not have the same concern as it does on a system that mixes the two paths. The only real concern then is the times when your stuck in traffic with a cop and don't want attention and at cruise so you don't get the drone. You could also use the remote control valve that they sell so you can lock it open when you want.

 

this is how understood it to be, that is why Capristo can sell their bypass valve controller without the worry of leaving the bypass open at all times.

 

Exactly why mine is always open, my Mille Miglia does not mix the main and bypass paths in the muffler.

It's nice to see that some people are finally grasping this concept.


Rob

 

It may keep the pathways seperate, but will not eliminate "check engine" and "slow down" lights if the valve is left open constantly. I have both the Capristo bypass valve and Capristo exhaust...along with QV rebuilt oem manifolds and oem catalysts. My local dealer (technical director) is very knowledgeable about 355s and I asked if he could put a switch to control the bypass valve on my car. He said it should not be a problem and even devised a circuit to spoof the Motronic not to throw a CE light when the valve is always open (since that will heat up the thermocouple that monitors bypass valve operation on a 5.2 Motronic 355). After he wired it up, and it was working, his testing found almost all the exhaust is running through the bypass, and insufficient exhaust runs through the catalysts. It started throwing codes for the O2 sensors and catalysts. He said the more it ran, the Motronic kept richening the mixture...this was changing both the short and long term fuel trims.

This is not a problem on later 360 and 430 because the valves are AFTER the catalysts and O2 sensors, not before them.

What was learned, is leaving he bypass valve open all the time on a 355 is not a good idea.

 

An interesting thing happened on my first long drive with the Capristo and bypass wired open last week, after driving about 40 miles at highway speeds I pulled into a parking lot and my idle dropped to around 500 rpm and was running very rough as if she was going to die. I should also note that after a total of about 100 miles I never did get a slow down or check engine light. I did not install the thermocoupler after the bypass valve, I left it plugged in to the computer just not installed in the exhaust system.
Now with the stock exhaust and operating bypass valve I don't have any problems with the idle.
After reading the above this makes me think that it was due to the o2 sensor giving bad info to the ecu.

This is discouraging since I have driven with an operating bypass valve and with the bypass wired open. And I’ve decided the Capristo is truly best with the valve open all the time, the sound gives me a grin from ear to ear.

 

I agree, the sound with the valve always open is glorious. I tried it once by simply unplugging the hose to the Capristo valve...which causes it to default open.

Eric, does your "check engine" light work? When you first put the key in the ignition and turn to the "on" position, does the "check engine" light illuminate? This is the position prior to the 'start' position.

 

Yep, check engine light works fine on start up.

 

I think relocating the primary O2s upstream of the 'Y' in each header would be a relatively easy solution. I think that will be part of my major at the end of the year. My car has been running fine so far and is averaging around 20mpg but it will give me some peace of mind that all of the exhaust volume is sampled, bypass or no.

 

Well wouldn’t you know it… I just went out and wired my bypass open again (couldn’t resist the sound), shut the battery off for 10 min and then turned back on and started the car and let her run for 10 min to reset everything. Shut down car checked oil, got back in started her up for a drive and the slow down light was blinking. So I guess it’s going to be a functioning bypass valve for me unless I can figure out a way to trick the damn ecu.

Also I checked my exhaust tip temps with an IR reader while the bypass was wired open here is what I found. Outside tips 202 degrees fahrenheit, inside tips 356 degrees fahrenheight. Not sure which one is the bypass?

 

I believe the inside pipes are bypass, outside go through the main catalysts.

Do you have an OBDII code reader? If so, could you connect it up and see if you have any pending codes stored?

 

That would be a pretty good solution.

 

"Verified" This is how mine works...

When the bypass is wired open my inside pipes (bypass path with capristo) are hotter than outside pipes, according to the above post this makes sense. With bypass valve working and the car at idle I discovered that indeed more exhaust exits through the outside pipes than inside ones. Outside pipes get hotter than inside ones thus opposite of when the bypass is wired open.

I do have an OBII reader, although I no longer have the slowdown light since I unwired the bypass valve so it is working and ran the car to reset the motronics. Everything is working as designed now and I no longer have the slowdown light.

 

That is the point, an beauty of the Capristo bypass, you can open it up for some fun but most of the time you can run with the normal operation and the car doesn't tend to experience any of the issues of a wired open bypass.

 

My car experienced the same in 2 nd gear, I fitted the Capristio valve and opens fine now , apperantly the Capristio valve requires less pressure to open, also fitted decat pipes, sounds awesome

 

Mine has stock bypass valve and capristo level 3 and the valve opens in second about 6500+rpm....really at top end.

I am interested in the comment about the capristo valve opening sooner in second ....any others experienced that ? what about other gears ?

Mine is ratteling too :-(......not sure if worth the grand to change.

 

My setup is the same as yours and my valve opens around 6500 rpm in second gear. I love it when doing a high speed run from first gear, the valve is open most of the time in second as well before shifting into 3rd.
I wish there was an easy way to program the ecu to open in 2nd gear around 2,800 rpm like all the other gears.

 

I have the Capristo valve...it seems to open more willingly...but it could also just be my imagination. I would consider the Capristo valve if only to fix the damn rattle permanently. There are a few shops that can rebuild them, search threads here, I saw a post recently.

 

Old thread, but relevant for me.

I can also verify that my '95 valve opens 2800rpm except in 2nd gear which seems to contradict what's written in the owner's manual.

What's the easiest way to "wire" open the bypass valve just to test how my Capristo sounds?

 

I must say that my 95 doesn't open in 2nd gear either, unless you're in it from first (to the floor), then it stays open in 2nd, but while cruising in 2nd if you punch it, it never opens. Its very frustrating!

The easiest way to rig the stock bypass valve open is to route the vacuum hose coming off intake directly to the pipe on the air rail going to the bypass valve, or you can put a straight connector in place of the solenoid valve (basically bypassing the solenoid valve).