Technical Tips Tasmin/280i

Improved Tasimin/280i Exhausts

I live in an area that doesn't have emissions inspections, so I could do some things to make my 280i run better. Mine is pretty stock except I have real dual exhausts -- each bank goes straight down and towards the rear. I have the oxygen sensor in the left exhaust pipe as close to the header as possible. I have small turbo mufflers at the rear and super trapps on the ends. It is still VERY loud, but accelerates like a bat out of hell! I autocross it, but it is in A Street Prepared because of the exhaust change. I have heard that this change is worth 25 hp because the exhaust is so restrictive. It revs to 6000 rpm very quickly in low gear now.

The original 280 in the USA has each exhaust pipe going forward and turning VERY tightly in front of the engine to a collector pipe that contains the Oxygen sensor. Then a catalytic converter is located UNDER THE ENGINE SUMP!! and the pipe goes down the right side of the engine (passengers' side) and splits to dual exhausts. Then under the seats it turns to mufflers and then goes to the rear with resonators / small mufflers right ahead of the rear "bumper". The tubing is 1 5/8". I installed 1 7/8" tubing and the aformentioned "real" dual exhaust without a catalytic converter. It is VERY loud. I read somewhere (probably Steve Heath's book) that 2" pipes will fit, but I don't know how. It is a VERY tight fit now. It doesn't rattle on the frame, but when raised off the ground on jack stands the exhaust system fouls the rear halfshafts -- touching the shaft. I don't have pictures, but perhaps can draw a diagram. I'll try.

The guy who made my system ($240 is all it cost) had to make quite a few parts and weld them together. He did a good job, but has retired. I don't know where I am going to get a replacement, which is starting to be needed. There are a few leaks at joints. I bought it almost 8 years ago.....

We have had this discussion on the TVR group before. I remember the comment (also in the Tech Tips book -- you guys need to join the TVR Car Club North America and order the tech tips book as well as the parts manuals / repair manuals for your cars -- Yes TVRCCNA has them for sale!) that someone said if you adjust the fuel injection full lean (not a good idea for everyday use) you would meet the emission requirements in those areas that have testing. But Chuck Linn commented that not only is that illegal, but the inspector LOOKS for the catalytic converter. Some others commented that they wouldn't know where to look (probably true). [Inspection rules vary by state and sometimes by county. In my part of PA they plug it into a machine and if the machine says it is clean, it passes. - Webmaster]

It was suggested that we make a system that has 2 free-flow catalytic converters under the seats where the original mufflers are and relocate the mufflers to the rear of the car. Well....... as it turns out it is illegal to move the catalytic converters. Not that this is enforced, but that is the law. The only legal exhaust system for a 280i is that crap at the front leading into the converter UNDER the engine sump. From the "Cat back" you can do anything. Unfortunately, that is not enough to make it drive as it should. You are sacrificing about 25 horsepower.

Now..... will anyone know that or check that? I doubt it. But I don't live in California or New York. In central Illinois, where the Republican Party started (and don't our local pols know it!) there are no emission checks. The only disadvantage I have to my exhaust system (besides the noise) is that I have to run in A Street Prepared in autocrosses.

Two years ago I replaced the restrictive stock exhaust system on my US spec '83 with a custom one. The manifolds were reversed from left to right and right to left as on the European,( no cat) versions and two small catalytic converters running fore/aft replacing the transverse under-the-seat mufflers. The rear mufflers are small Magnaflow CM50 originally with straight tips. This was too loud so I had curved ones added similar to the stock ones and this quietened it down to an acceptable level. Piping was only 1.75" (I wanted 2") as that was all I could fit around the rear suspension. There was definately an improvement in performance. Cost: US$580.00 parts and labour.

It still isn't a rocket so I am very seriously contemplating swapping the engine with a Ford 5.0 litre V8 with aluminium heads. The weight increase isn't too dramatic but the HP is. Naturally, brakes and suspension will be upgraded also, not an insignificant task. This will probably keep the Tasmin off the road for most of this year.

The current mish-mash of federal and state laws are very confusing. These only seem to apply if the car is driven on the street. IE cars only used for racing are not regulated. The real reality is what does your local vehicle inspection require? Note that California and New Jersey conduct random stops where they look for missing equipment. In California the CARB (California Air Resources Board) may certify your modified car as being legal. They have books listing what part must be on what engine when mounted in a given year and model car. Pennsylvania and other states have "classic car" plates for cars for which emission control parts are no longer available.

Corrections and tips should be sent to CRC


Last updated on April 20, 2003.