| Author | Message | ||
| Modified348ts (Modman)
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As in regards to adding the Tubi then bypass of the cats- Adding the Tubi not only helped the car sound better but gained more power according to 1/4 mile times I received. If you have a 91 348 like mine, the tubi cut the weight down more than half on the muffler since the stock ones used 2 mufflers- rediculous, and also lowered the heat factor. As far as hollowing the cats or adding test pipes I lost low end torque and quarter mile times remained the same, I may have lost low end but in the upper range power was there which made up for low end torque loss. Wasn't worth the exchange but definately reduced the problem with check engine lights and reduced the overheating readings from the sensors. Tubi designed their mufflers to work with the stock cats on but without them not much benefit of any significant power increase but the sound was slightly louder though.. If you want real power increase then add a turbo.. there isn't to much you can do to get much more power then what Ferrari has already done to their motors, you can play with adding a custom made chip or chips. | ||
| James Pai (Jaymus)
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I have a 90TR with Tubi, and bored out pre-cat and bypass pipes for the main cats. I would definitely recommend the pipes. It sounds much better with the pipes. I only had Tubis on before, but after putting on the pipes (Nick's) the sound became much louder, sounds great underload on the freeway at full throttle. James | ||
| Michael A. Niles (Man90tr)
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Steve, You are correct. I must have transposed those numbers from one of the ferrari books I read that contained an error. I also show the 380 at 5750 rpms. Thanks for the correction. Michael | ||
| Michael A. Niles (Man90tr)
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Steve, I was going off of memory, i am going to double check now -- I may be wrong but I thought i saw that. back in a bit. Michael | ||
| Steve Magnusson (91tr)
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Jeffrey -- since you used the words "dramatically" and "junior F1" I think you'd need to replace both the pre-cats and the cats to get that loud (as I mentioned earlier, items #57 and #58 come in two versions so the longer ones would replace all cats). Michael -- which US OM are you quoting for the TR HP figures? I have both 536/88 -- for 1989 US models and ???/90 -- for 1991 US models (I'll look up the print number this PM) which I think both list 380 HP at 5750 RPM (in Section 1 page 11) -- where is the second HP spec shown? | ||
| Michael A. Niles (Man90tr)
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Thanks, Steve. I agree that the heat aspect and the reduction of the cat fire hazard is probably the key advantage. My US manual shows two horsepower ratings based on rpms. 380 at 4750 and 390 at 6800. I like to live in the 6000 plus zone so the less heat the better. Michael | ||
| Jeffrey Cheng (Cigtopgun)
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Adam - I think the real answer to your question will come when I replace the cats with the bypass pipes per Steve's post. The Tubi by itself definately changes the sound of the exhaust and makes it throatier at idle and louder (racier) under acceleration, however, I have this pre-conceived impression that the car should sound like a junior F1 car when car when accelerating down the road. It does not sound like that with just the Tubi and all the cats in place. Steve - Thank you for going over and above the call of duty in replying to my post. The diagram is very helpful. My cursory glance under the engine led me to believe that the pre-cats were part of the header, however, I see that they are not. I am assuming that part #58 is what I am looking for to replace the pre-cats. I have a question though. The pre-cats appear to be significantly smaller than the regular cats. By eliminating just the pre-cats and not the regular cats ... will the sound change dramatically or do I really need to do both to achieve my junior F1 sound? Once again ... thanks and I appreciate the pic and the diagram! | ||
| Steve Magnusson (91tr)
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Michael, I'd guess that the HP increase (sans all cats) would be ~5% max -- my recollection is that the US version TRs are rated at 380 HP while the SA (cat-less) version is rated ~400 HP (although the SA version may also include the "reprogramming", via different pin groundings, of the ignition ECU to give more ign. advance too). For me, the (slight) power increase and the more aggressive low-RPM acoustics are nice things, but there are two other advantages: 1. the underbonnet temps will be lower, and 2. the stock cats are preserved if they are not on the car. | ||
| Michael A. Niles (Man90tr)
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Frank, That is the reason you recommend the pipes?. I recall you mentioning this in thread not too long ago but darn cannot remember fully. If I recall you liked the sound at higher rpm with the load Tubi sound at low rpms. But was there a horsepower or more peppy feel with the bypass pipes? Steve, from an engineering perspective what do you believe is the horsepower increase with the light off cats and cats out of the car? Thanks. Michael | ||
| Steve Magnusson (91tr)
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Argyle -- yes, items #18 are the regular TR cats -- got to give the F Engineers some credit here as the stock TR cats have much larger honeycombs (~5" diameter) compared to the typical US V8 cat that uses a ~3" x ~4" oval honeycomb size. | ||
| Frank Parker (Parkerfe)
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I had the bypass pipes on my 1986 TR , 328 and 348 and loved them. I would recommend them over the Tubi's. | ||
| Argyle Co (Argyleco)
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Steve, What is item 18, is it the cats | ||
| Steve Magnusson (91tr)
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Jeffrey -- the TR pre-cats are not part of the headers (but you are right that a "pipe" to just replace the regular cat is simpler than a "pipe" used to replace the pre-cat) -- the pre-cats are labeled #23 and #24 on this jpeg of TAV 20 from the SPC:  The "official" F bypass pipes (items #57 and #58) come in two flavors -- short ones to replace the pre-cats only (F PN 142166 and 142167) and longer ones that replace both the pre-cat and the regular cat (F PN 128589 and 128590). Bypass pipes to replace just the regular cat are not an official F part and must be purchased from an aftermarket supplier. I purchased the "official" short bypass pipes from T. Rutlands (not cheap even from them), but a lot of guys just "clean out" the precats by breaking up the internal ceramic honeycomb structure to remove it and pull out the surrounding "steel wool" padding too. Here's a jpeg of my '91 with the short bypass pipes + stock cats + Tubi:  (I still think it doesn't make much engineering sense to bypass the regular cats yet leave un-cleaned-out pre-cats in place.) | ||
| Adam Goldman '86 TR (Icnsltmfg)
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Jeffery; Did the Tubi make the car louder or just throatier? I am still torn on spending 3K for something that is only slightly louder. I am still thinking about the Koenig Racing version. Adam | ||
| Jeffrey Cheng (Cigtopgun)
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Just installed a new Tubi on my TR on Friday. It is definately "throatier" than the stock system, however, still not aggressive enough for my taste. Next will be to straight pipe two of the four cats. In a previous post it was suggested that I should replace the pre-cats (light off cats) with test pipes first followed by the main cats second if it was still not loud enough. However, upon closer examination it appears that the main cats would be much easier to replace than the pre-cats. The pre-cats are actually one piece with the headers. Unless someone has done something different it would appear that you would either have to cut the pre-cats off and weld in straight pipes or simply custom make new headers without the pre-cats inline. On the other hand the main cats are straight cylinders that would appear to be much easier to replace with straight test pipes. If someone has done this or has a different perspective to offer ... I would appreciate hearing it. If not, I guess the main cats will go first and we'll see what happens then. |