| Author | Message | ||
| Henryk (Henryk)
Junior Member Username: Henryk Post Number: 150 Registered: 8-2001 |
Steve: Thanks for the info. While these pipes may be difficult to fabricate because of the bends, I feel, rather than spending $2400, I would try and have them done locally.......I have a strong feeling that this can be done for much less. I like the idea of getting rid of the pre-cats, and cats, with one pipe. However, this will have to wait till Winter, since I am enjoying the car too much right now. | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 909 Registered: 1-2001 |
Henry -- the over-temp thermocouple goes in the exit side of the regular cat so no change there for me (if all the cats are removed, it doesn't matter whether you have the thermocouple in place or not since unburned fuel in the exhaust stream will not self-ignite without a cat). I got that set from T. Rutlands for ~$1,100 (and they wanted ~$2,400 for the longer SA version) -- probably not my best deal (but being a curved, and "parallel", pipe it's more difficult to fab a homegrown version)... It's a little cooler under the bonnet without the precats (but still damn hot by any measure), and it loudens up the exhaust note a bit (but still nowhere close to sans all cats). I think the precat's purpose is to work in conjunction with the air added by the air injection system to try to clean things up better during the cold running phase when the KE system is intentionally adding some extra enrichment (i.e, the extra leftover hydrocarbons from cold-running and the O2 from the air injection are supposed to react together in the precat). A lot of TRs have the honeycomb/steel wool structure broken up and removed from the precats turning them into hollow bypass pipes, but I wouldn't encourage anyone with decent used TR precats to do this -- there are plenty of TR precats out there that have failed (melted) when the injection system went wacky so if someone wants a hollowed-out set they can be found for about $400/set (I've got a hollowed-out set and would sell them for that -- or I'd be glad to trade them plus a few hundred $ for a decent working used set -- anyone interested either way please give me a shout). | ||
| Henryk (Henryk)
Junior Member Username: Henryk Post Number: 147 Registered: 8-2001 |
Thanks Steve: According to the pictures in the manual, those are the ones......have you put in the thermocouples into the pipe? Still, what are the pre-cats for......just to heat up the exhaust, with no catalytic effect? What difference have you noted when you did this? Where did you get them, and how much? Thanks | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 908 Registered: 1-2001 |
Henry -- the factory makes two different sets of test pipes for the TR (I don't have my SPC with me so can't do PNs) -- the shorter ones replace the pre-cat only; the longer ones (used on the SA version TRs) replace both the pre-cat and the regular cats. Here's a shot of the short ones (just replacing the pre-cat)  | ||
| Henryk (Henryk)
Junior Member Username: Henryk Post Number: 146 Registered: 8-2001 |
What are the pre-catalysts for? There are two of them on my 88TR, one for each side, coming off the exhaust, and before the regular converters. Would one also replace these? In the parts manual, there is a replacement: part nos.: 128589 and 128590. It states that these are for the US car, delivered at the factory. They look just like one would expect the test pipes to look. What gives? Then, to do an 88TR conversion, one would replace the pre-cats, and the cats. One can use the factory test pipes for the pre-cats, and get two flanges and a piece of pipe, some welding, and BINGO.....one fast TR. The pipes would, of course, be stainless, and have the fittings for the Thermocouple, and O2 sensor. Does this make sense? | ||
| tCoupe (Allen)
Junior Member Username: Allen Post Number: 70 Registered: 3-2001 |
Mondial t by-pass pipes set w O2 bung and "Ferrari" tag.  | ||
| tCoupe (Allen)
Junior Member Username: Allen Post Number: 69 Registered: 3-2001 |
Erik and Mike, thanks for the info. I did find a set of Factory Ferrari Cat by-pass pipes locally. They're new out of the box and have the "Ferrari" name badge on them. I needed them since I was taking the Cats off for inspection. The "Slow-Down" lights were coming on and I wanted to bring the Cats in for evaluation. These By-pass pipes have "Woken-Up" the engine. No big sound increase but better throttle response and more top end power. I still have the stock Silencer on. HenryK, I installed mine myself. Took about 2hrs each side due to clean up on old exhaust gaskets and rusty flange bolts. Yes, you do need to keep the O2 sensor hooked up and be gentle with it. The Thermalcouple and exhaust ECU has been unplugged. No more "Slow-Down" lights!!!! Looking forward to installing a Tubi soon. My 348 engine is coming alive!!!! | ||
| Mike C (Concorde)
New member Username: Concorde Post Number: 2 Registered: 8-2002 |
STEBRO makes a cat bypass test pipe... it has a sound resonator chamber that's probably about 3/16 wider than the ends of the pipe, with a small amount of stainless steel wool in that expanded area to deepen the exhaust sound. VERY nice on my 308/QV with otherwise stock exhaust. These units aren't listed on their website (www.stebro.net) but if you call them at 1-888-8-STEBRO and ask for "Dan", he can set you up. They're much better sounding than a straight through pipe (which can sound kind of harsh), and still gives you the benefits. Their pipes include the bungs for the O2 and/or thermocouple, whatever you need. | ||
| Erik R. Jonsson (Gamester)
New member Username: Gamester Post Number: 37 Registered: 3-2002 |
I will happily make a set for your Mondial T, I have already made units for Martins 348 from stainless steel and he is pleased with them. Email me at [email protected] I can and will make them for any other model as well from stainless, with the O2 bung. Erik | ||
| tCoupe (Allen)
Junior Member Username: Allen Post Number: 63 Registered: 3-2001 |
Anyone have a source for a set of test pipes for a 1989 Mondial t Coupe? Thanks | ||
| Henryk (Henryk)
Junior Member Username: Henryk Post Number: 113 Registered: 8-2001 |
Thanks Geoff, Very clear description. It is obvious that the O2 sensor is needed, and appears to have nothing to do with the converter, since it attaches to the exhaust before it. | ||
| Dave Penhale (Dapper)
Junior Member Username: Dapper Post Number: 142 Registered: 4-2002 |
Geoff, brilliant simplistic description, thanks for taking the time. Problem without the cats fitted over here (UK) would be meeting the tight emissions test at annual MOT (Ministry of Transport- as was) test time. Could mean refitting them every year pre test and refitting post test. | ||
| Geoff J. Germane (Germane)
New member Username: Germane Post Number: 5 Registered: 7-2002 |
The following information may be of some help in connection with this topic. The O2 sensor is essentially a solid state (zirconium dioxide) switch triggered by excess O2 in the exhaust, upstream of the catalytic converter. One part of the sensor contacts ambient air, the other contacts the exhaust stream. The sensor voltage drops rapidly near stoichiometric conditions (chemically correct fuel-air ratio for theoretically complete combustion), and remains low as excess air increases (fuel-lean mixtures). Its purpose is to provide feedback to the fuel management system to maintain a fuel-air mixture at approximately stoichiometric proportions by adjusting fuel flow into the engine. This is necessary because optimum functioning of the catalytic converter requires an exhaust mixture and operating temperature that can be achieved only with combustion of near-stoichiometric mixtures in the engine. Practical application of this may be assisted by the following: Maximum power is produced under slighly fuel-rich mixtures, richer than the control system provides with a functioning sensor. Maximum fuel efficiency occurs under fuel-lean conditions, perhaps 10-15% leaner than stoichiometric and limited by the lean misfure limit of the engine/fuel/operating conditions. A sensor without a catalytic converter enables the fuel management system to function normally. Removal of the sensor will create an open loop condition whereby the engine will no longer operate, or a default condition is achieved, which might be slightly fuel-rich under some conditions, and slightly fuel-lean under some conditions. | ||
| Frank Parker (Parkerfe)
Intermediate Member Username: Parkerfe Post Number: 1159 Registered: 9-2001 |
The test pipes I put on my 328, TR and 348 all had fittings for both the O2 sensors and the thermal couplers. | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 879 Registered: 1-2001 |
I think the effect of no and/or wacky O2 sensor input siganl to the injection ECU will vary depend on the system so more than one answer probably. I know KE TRs tolerate no O2 signal pretty well (working sort of like a weird K-Jetronic with an "electric" warm-up regulator with no O2 signal), but not the greatest IMO, and putting the O2 sensor in roughly the same position in the test pipe will work just fine. The later cars with multiple sensors might get more unhappy even if the sensors are in their original positions (but are they O2 sensors or something else?). With a single O2 sensor in the exhaust stream(s) the first approach has got to be to duplicate the orignal position even if it requires adding a bung -- JMO. | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 1924 Registered: 12-2000 |
Some "Test pipes" include fittings to accept the oxy sensors. What affects this has on mixture levels I'm not sure... At least, they are still getting readings. | ||
| Henryk (Henryk)
Junior Member Username: Henryk Post Number: 112 Registered: 8-2001 |
I have often read how people remove their catalytic converters, when installing a new exhaust. What do they do with the wires coming from the O2 sensors.......just cut them? The wires go to the ECU to regulate mixture, so how can one just ignore them? It would seem to me that one would have to also replace the ECU, with a version that does not include input from the converters....but now one gets into a whole can of worms......or is it really that easy? Thanks |