+1 ........... all currently true ..... however there is a new set of shielded 355 manifolds under development in the gothspeed abyss ...... we'll see what they do on the dyno once completed ..... +1 ......... the only downside IMO of using 360 manifolds is the primary cats would no longer be bypassed ......... which is not entirely a bad thing though ... Yes .... the main benefit is the reduction of heat soaked metal, weight and complexity. The F1 sound can be preserved with a well designed system. The difference is some later 360 manifolds have an integrated pre-cat, which will not fit in the 355 configuration. CS manifolds are very close to 355 manifolds but with a slightly larger collector and of course no post collector diversion.
Pics! Your twin bypass systems? I would guess you do that for more flow area than a single valve but the exhaust merges in the muffler and is divorced from primary flow. Just a guess! Very nice stuff
I'm curious to hear Rifledriver's opinion on the Write-up on The Capristo exhaust system for our 355's. Exhaust system for the F355. Made of (T309) stainless steel. This system fixes the known circular vacuum problems with the original F355 OEM system. The problem begins once the OE cat bypass valve opens. Once the valve opens, the exhaust gases do not flow through the main catalytic converter but through the bypass channel. As exhaust gases flow upwards through this bypass channel, a vacuum is created within the primary catalysts and hot exhaust gases within the muffler (!) are drawn backwards through the main CAT and then back upward into the bypass channel! Indeed, when the exhaust gas valve is open, this gas flow is circulating ceaselessly generating more and more heat. This causes a huge reduction in performance and additionally heat up the gases. This problem was welll known to Ferrari. For this reason the F355 was changed in 1996 (2.7 to 5.2) and the manifolds were modified (lengthened) exactly in the place where the vacuum is generated. But the problem was not eliminated by this measure. This extreme backpressure problem is the reason why the stock F355 never produces the quoted power output. The Capristo exhaust was designed to eliminate this problem. Irrespective of the volume leve, each Capristo is designed so that the channel from the main catalytic converter to the outer end pipes is completely seperate from the upper bypass channel to the inner end pipes. Consequently it is not possible for a vacuum in the main cat to be generated - reducing temperatures and increasing performance.
Admittedly, I'm a new kid here, but this is the first I've heard of this problem. Are you saying that Capristo is the only 'aftermarket' header/system manufacturer who has succeeded with a design that has fixed the problem?
Ferrari went from 2.7 to 5.2 (OBDII) to comply with new emission requirements. And IMO the OEM 2.7 manifolds diverge the bypass and main cat flow more equitably than the 5.2 manifolds. That said, the post collector investment cast diverge on newer fabspeed headers, divies the flow much better and smoothly than OEM 5.2 manifolds. After many tests with stock/aftermarket manifolds and exhausts for the 355 ....... the few times I have observed reduced flow through the main cats, was if the bypass for whatever reason was open during low throttle/load situations. Higher throttle flowed through the main cats as normal. Having an exhaust/muffler that combines the flow paths after the bypass and main cats ..... in and of itself is not a problem ....... as long as the bypass flow is complementary to main cat flow. Having separate flow paths is a positive as long as the bypass valve(s) are operating properly (closed at low RPM and open at upper RPM). But, if the flow paths are separate and the bypass is wired or stuck open at low throttle/load .... one could draw some atmospheric air through the main cats, which would affect O2 sensor readings. So in summary ...... make sure your bypass valve is functional and not stuck open .... primarily on the multiple main cat O2 sensor 5.2 355.
When you guys are talking about cat delete / bypass, are you doing this on 1995 cars or later OBII cars? If on later cars, what are you doing to avoid check engine lights, etc.
I just called Nick Forza for price on a Capristo 2. $3900 with 2 week lead time. He wouldn't go any lower. When the valve is closed, the Capristo 2 under low rpms should be the loudest of the 3 variations (cap 1,2,3). When the valve is open, all 3 should sound the same. Under low rpm, the cap 3 is too quiet for me. Almost mercedes like. Even with my bypass wired open. I need it louder , so i would like to try out a Cap 2. My Capristo 3 will be up for sale soon. $3,000. $100 to ship. Pick-up in So Cal no problem.
Hmm, I thought 1/2/3 was referring noise level with closed bypass, 1 quietest 3 loudest. 2 is not very loud at all unless the bypass is open
I know. It seems weird, but this is from the Capristo rep's own words. If you want 3, we can do a straight trade .
Yes I read it. Rather counterintuitive numbering if you ask me Yours is a 2.7 correct? You can order it without the bypass thermocouple bung if you like. (which is what I did). You should see if they will make you a custom 3/3. When I looked inside the primary inlets it appeared to be a sort of restrictor plate, like a percentage of the primary flow was blocked to quiet it down. I'm just going off of what I could see so not 100% sure, but looks like it could be made to easily be louder on the primary side. (You could probably have a fab shop do the same to yours, just cut the inlets off of the muffler, remove the restriction and weld the inlets back on).
Under normal/low rpms Tubi was significantly louder and throatier. I would like the Capristo to match that at the very least. When valve opened, the Capristo is a screamer. There's not much of a pitch change with the Tubi.
The preliminary design involving tube sizes and the proprietary new 'goth' collector is completed ...... now working on CAD drawings for the CNC parts of it .... Yes, twin valves offer quite a bit more top end flow capacity ....... and on the 5.2 example in the video .... the flow paths are 'essentially' separate .... but on my 2.7 version the flow paths are creatively merged down to 2 'monster' exits ...... I should still have room ...... I will have to see what is going on with that .....
