355 bypass valve removal

If Dave and Bruce see no issues with upper RPM tuning I think my next mod will be to relocate my primary 02s to the collectors.

I too am curious as to what the ideal A/F ratio is for these engines.


Rob

 

On my F355 I've wired the valve since 3 years now and I made 25'000km!
There is no cat and I have a Tubistyle with Larini manifolds.
No problems at all until now but...
Of course I mainly drive the car on the street, but I usually goes on track 4 times a year.

 

Uhhhhh.......not sure what you know about the Ferrari ECUs, but there are more than one and they talk to each other (sort of like a primitive CANBUS system.) That's reason #1 to stick with factory electronics instead of a standalone. Reason #2 is to maintain the OBDII diagnostic system that allows the car to communicate with an SD1 or SD2 computer during routine service and repairs.

 

I'm not sure if the 348 even has the liner issues but either way that system you posted won't be a problem because it splits after the O2 sensors. Once the complete volume of exhaust gas is measured it doesn't matter how many times it separates.


Rob

 

good point.

 

QUOTE:"Once the complete volume of exhaust gas is measured".

O2 sensors do not measure the complete volume of exhaust gas.

 

Does a flood title 355 need H2O sensors?

 

lmao....starting kind of early aren't you.....need me to send you some olives?

 

How about some lime slices?

Better yet, as cold as it is, maybe a little drink umbrella so I can have a tropical drink and pretend like I'm somewhere warm!!!???

 

You'll have to contact Dave for the little umbrella...
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Obviously they don't but my point was that splitting the exhaust after the sensor is not going to cause the error in A/F readings as in the current design of the F355 exhaust. Splitting the exhaust before the sensor and sticking the sensor in the more restricted path is skewing the A/F readings. If both paths were equal in restriction there wouldn't be an issue. If the sensor was placed in the collector before the split it would measure an accurate sample. Does this make sense?


Rob

 

That looks like the pecker stiffener medication commercial when they're sitting in the bathtubs at the beach!

 

I have a 1999 F355 spider and was about to put TubiStyle evolution until i heard about Capristo.

It appears that the tubiStyle evolution develoed a couple of years ago are very similar to what capristo had done several years before that. I was also told by a ferrari mechanic that the Capristo sound is awesome to the point that he now prefers it to Tubi. Anyone hear of this Capristo?

Also, this whole open and closed valve issue seems to be addressed by a Capristo valve that avoids the whole issue faced with F355s. Again, does anyone have any experience with this?

Finally, this past january 2010, Trade Partner Europe wrote article summarizing results of tests performed on 4 exhaust systems imcluding Tubi Evolution and this Capristo system again seems to have scored big.

Essentially trying to decid between Tubi, which was my first choice, and this Capristo system that sounds realy tempting.

Can anyone one shed some light?

 

I smell canned meat. Perhaps Spam?

 

Rob, several years ago I had contemplated moving the O2 sensors up to the last collector on the headers, but due to the fact I had basically 2 reversion waves(primary and secondary) converging at a common point(at the split off right after the last collector) the O2 sensors would still be subject to the reversion waves which causes the sampling error. Remember that the reversion wave goes all the way back to the exhaust port and is what cause "backsliding" into the combustion chamber.

Several interesting things to note: the 2.7 header split angles are very different than the 5.2, and the lenght and configuration of the 2.7 upper y-pipe in relation to the 5.2 is also very different. Then I looked at the 360 and 430 exhaust systems which are radically different than the 355 noting that the secondary exhaust system has been completely eliminated and the reduced back pressure now is limited to the muffler internals(for the most part) with by-pass valve posterior to the muffler proper....as far as I know this set-up eliminated O2 sensor skewing but the reversion wave is still present and when the cats fail some of this material is pushed back into the combustion chamber.

All of these issues would be fairly simple to resolve in a race engine where rules did not require emissions or noise levels.

But with the 355 being a street car, smog/emissions and noise levels are regulated(at least here in the USA). Ferrari had no option but to build a system that complied with all the regulations and at the same time trying to produce high performance output. This is a complete system comprised of various mechanical,chemical, and electrical components and when you mess with just one facet of this system to cure a problem you may at the same time create multiple other problems that you never anticipated.

As you come to understand how the 355 works then you can proceed(even then with much caution) to make modifications. And as always you do only one mod at a time and test it thoroughly before proceeding any further.

One other thing, the O2 sensors are only online when the ecms is in the closed loop mode which is approx. 4300rpm or 23 deg tps(based on Erics data)...when you exceed either one of these values the ecms goes into open loop and the O2 sensors are offline.

 

LOL! Cute EUL328, but the questions are legit and i would acutaly appreicate your input as well. Whereas i have a F355, my friend has a 328 and when i asked his opinion, he said that he still has the original exhaust because unlike the 355, the replaced exhausts don't do much for 328s. As for my 2 friends with 355's, they all both tubiStyles.

Hence, "spam smell" comments from EUL 328 aside, my question is quite legit and still stands. Any feedback on TUBI VS CAPRISTO EXHAUST SYSTEMS for a F355 would be greatly appreciate...as much as i like listening to the exhaust systems on YouTube, any empirical info would be preferred.

Same applies for any feedback on a Capristo by-pass valve that apparently seems to address the valve problems on 355s

thank you

 

Now I'll address the above statement.

If both paths were equal in restriction then why would I need 2 exhaust flow paths...what would I gain or benefit from having a primary and secondary exhaust system?

There would be no reason to have 2 flow paths. You would use a single exhaust system period!

The one very unique characteristic of the 355 which seperates it from other Ferraris' including the 360(which has an engine very very similar to the 355) is its' F1 mimicking sound. A 360 can produce this same sound thru a single unrestricted exhaust system, but it violates sound ordinances(at all rpm's) in just about every jurisdiction.

http://www.youtube.com/watch?v=DOQFKgvA9AU&NR=1&feature=fvwp

So the 355 with its' dual exhaust flows can sound very tame and within sound ordinance confines at lower rpm's, but when you exceed a certain rpm or go WOT the ecms opens the by-pass valve and you all of a sudden experience a total change in the exhaust note..ala F1 dreamin..lol

With the ecms controlling the by-pass valve there is a correlation between the valve open/close and the closed loop mode(O2 sensors online) and the open loop mode(O2 sensors offline)...there appears to be some rough spots here in this transition. Apart from a malfuntioning by-pass valve this may temporarly skew the O2 sensor readings until full open and open loop mode are in sync....same in reverse for full close and closed loop mode. This can be easily verified thru diagnostic/monitoring equip. during a dyno run.

 

There are several really good stand alone ecms's available that present great features for RACE CARS.

But what about your street car..that daily driver? Even though the OBDII(factory 5.2 motronic) can be a real pain there are some very important and needful backup/safety systems it has that you will loose with the stand alone systems.

The conversion to a stand alone is very price and would recommend it for a race car that is really competing for a return in the investment. I would not recommend it for your daily driver.

 

A simple search here would have told you that many of us (if not all) have heard of Capristo. It's often a topic of discussion. Your post sounds/sounded suspicious to me. Like an attempt to promote or generate interest.

In any event "sound," like music, is a personal choice. You wouldn't ask someone else what music you should like, right?

It seems the rattling of the OEM exhaust bypass valves can be eliminated by making an adjustment. I regret not trying that before purchasing a Capristo bypass valve. Not that I've had any problems with it.

My opinion is that both TubiStyle and Capristo are well made and well respected and kind of "pricey."

 

I wasn't stating that the paths should be equal just that it would eliminate the skewed readings. Thank you for the detailed explanation, I am still learning all the unique mechanical/electrical tricks on this wonderful car.

I am beginning to think Gothspeed's 360 manifold'ed and bypass-less system is a great solution. What is your take on his method?



Rob

 

Yes but I am yet to better what Bosch gave us on the 355. We have to be careful not to mix the discussion of race V street cars as that will end up one big gray area.

Anyone doing changes without one eye on emissions is shooting themselves in the foot from both a performance and longevity stand point. Remember, these make the most power just short of piston melt down. Making sure the engine is riding that fine line is where the power is. The days of horking gobs of fuel at these engines are long past gone.

Wrong commercial Gary. Anything that comes with a warning of possible side effects that last a half a day scares the hell out of me, hard to get work done like that!

 

Well now it gets a lot more complex because we have to look at 2 different versions of the 355: 2.7 set-up vs the 5.2.(as I stated earlier the header split off angles are different and the lenght and configuration of the upper Y-pipes are considerably different) and with the by-pass remaining in place this is definitely a restriction in the closed and partial opening/closing transition...in fully closed position the ecms should be in closed loop mode with O2 sensor signal being utilized for fuel trim adjustment. The resulting reversion wave produces a partial vacuum that draws outside air into the exhaust stream that may dilute air sampling at the O2 sensor.

A good example of this low restriction exhaust path and one in which the upper and lower systems are fairly equal with the by-pass completely removed would be Verns(Llenroc) an FChat Consultant who owns a 355CH(no lower or upper cats)...here is an exact quote of his findings concerning this:

QUOTE: I have a 355CH with no valve, When I bnought the car the check engine lights were on just as the OP described. Took about 2 weeks to figure why they were. I put a piece of paper over the outside of the exhaust pipe(the outer pipe) and the paper was sucked to the pipe. What I did to correct the problem was to weld 2 header baffles into the upper Y pipe(CH cars use the Y pipe that has no cats) to cause just enough back presure to push some exhaust at idle through the lower exhaust and over the 02 sensor so they could get a proper signal to the ECU(lights went out)
So tell me where the air is going? I still say that valve is there for more than one reason.

Now that is a 2.7(OBDI) and in the 355CH a relocattion of the O2 sensor may have been warranted...what about the 5.2(OBDII) version? Have you ever wondered why Ferrari changed the header split off angle and made the upper Y-pipe much longer?
I will go out on a limb here with an assumtion...maybe they were trying to minimize the reversion wave effect which was causing the O2 skew error...my question again is, did this resolve the problem?

Maybe someone can answer this.....

 

Maybe Kris would be liken some of those side effects you might have for half a day...lol

 

thanks eulk328. I will continue my reading but am increasingly leaning towards Capristo. Will post once the deal is done. Will also take a look at adjusting the valves.
Cheers!

 

I tried tightening my valve and determined that it's not a permanent fix (at least for my car). I also tried making an adjustable block to create a very minor gap to help prevent the rattle. That too didn't last long. Net, I ended up going the Capristo bypass route and so far I've been very happy. I agree it is a little pricey but it's a small price to pay to get rid of that annoying rattle.