Thermal reactor replacement pipes wanted

[Nige-912E]

I would like to replace the thermal reactors on my 912e with some straight through, 'Y' pipes, replacements. I'm struggling to find an exhaust fabricator over here in the UK who'll entertain making a pair up for me. If any one has a set that they would like to part with or knows anyone who stocks them I would be very interested to hear from you. I will also be interested in selling or p/x the thermal reactors once replaced, they appear to be in reasonable condition.

[thomasz]

There are occasionally Thermal Reactor replacements out there. Before it expires take a look at ebay Item # 1831466648 which settled at $138.49. The picture should be a help at least. If you get a set yoou may want to sand blaast them and have them "Hot-Jet Coated" before you install them. It is a very good idea to put in the replacements.

I just saw a post of yours at ShopTalkForums yesterday. If you did not see my reply it was:

I would definitely NOT disconnect the air pump.
By page 2.17 of Probst's book (on Bosch FI,) "...A small amount of exhaust gas is rerouted back into the combustion chambers, diluting the combustion mixture and lowering the combustion temperature. You'll remember that excessive combustion temperature is the cause of NOx formation." (The cheapest most convenient source of an inert oxygen free gas -and thus unburnablegas- is the exhaust gas.)
So your 912e should run cooler with the EGR intact.

The power require to drive the pump should be minimal. And the EGR system is adaptive. A vacuum line from the intake controls the opening of the EGR valve.

The Thermal Reactors DO focus the heat so that unburnt hydrocarbons can be consumed. There were bypass tubing available, although there are probably not a lot of new ones out there. If you find the bypass pipes save the old ones, you could probably rent them out to Californians.

The official Porsche service manual does not list any catalytic converter. Many other sources such as Snap-on guides and the Bosch technical bulletins mention one but it seems to me to be an old wives' tale.

The fuel injection should be much more efficient than carbs. It does not have a lambda sensor for feedback but it still gives very close to a 14.7:1 stoichiometric fuel/air mixture. It is an analog computer and although it does not have the ignition mapping of later model cars, it does a great, fast job of control.

Of course if you weight the advice and decide differently, please write to me. I'll buy the parts you remove from your car.

Tom Zuraw

[COLDBASS]

Nige,

This is a long shot, however, I was referred to these folks by Type IV exhaust guru Chris Foley.

" In the UK-Justkempers". I had originally requested a custom SS exhaust and Chris indicated that I should check with these folks...

thomasZ,

Excellent post!!! Many still believe that the EGR causes the motor to run hotter and as you have clearly explained quite the opposite is true. I was enlightened early last year.

I have stored my TRs in my personal 912E time capsule hoping to never have to install those items again.

I have never seen an unaltered 912E exhaust. Everyone seems to have installed the defacto Bursch exhaust...

Good Luck,

Bob

[WFBowen]

Nige:
I think your best bet is to either try to find some on Ebay (like the ones mentioned above) or see if any parts houses happen to have a set of these NOS laying around. Our hosts here at PP seem to have sold them at one time:
http://www.pelicanparts.com/catalog/shopcart/911M/POR_911M_exhaus_pg6.htm
I assume that Bursch is still in business, so maybe someone can special order them. Your problem, as you know, is that you're dealing with a US only model, so you'll most likely have to deal "across the pond." Also, keep working the 912 boards, as someone in the US will eventually pop up needing your parts or willing to swap.
As for the EGR/Air pump info mentioned, these two systems are independent. Keeping EGR is not a bad idea - it helps lower combustion temp under load. The air injection, however, can be dumped. Granted, there's little HP to be gained, but removing at least the pump/filter cleans up the engine compartment and usually reduces engine noise (the unpleasant kind.)
As for the FI unit itself, it does do a good job, but for performance (not smog) there's nothing like one venturi per cylinder with a straight path to the combustion chamber.
Good luck,
Bill.

[thomasz]

I have the highest appreciation for the 912e L-jet system, with perhaps the exception of the Thermal Reactors.

EGR
To reduce NOx emmisions they wanted to introduce some inert gas into the combustion chamber to reduce the high temperatures that can give rise to N0x. Carrying cylinders of Argon gas is not practical so they used exhaust gas as a free source of unburnable gas. Because it lacks oxygen to contribute to combustion, this hot gas actually cools the combustion chamber instead of heats it. Very clever! But reducing NOx by reducing temperature is at cross purposes to reducing (unburnt)hydrocarbons emmisions.

Air Pump
To clarify what I posted about the air pump, it does inject some fresh air near the exhaust ports. The purpose of the thermal reactors is to contain heat to promote the burning of unburnt gasoline (petrol) in the exhaust stream, aided by the additional air injected. If you can get Thermal Reactor replacements the heat right beside the heads will be reduced. With the proper air/fuel mixture in the engine, the unburnt hydrocarbons should be low as should be the associated temperature rise. The HP difference from combustion should be nil because it occurs after the exhaust valves, with the only difference in HP coming from driving the pulley of the air pump.

The fuel mixture should be pretty precise from the analog computer. Many people do not appreciate the power of an analog computer. Finding the logest piece of spaghetti (uncooked) is done digitally by measureing each piece, sorting them and keeping track of the longest. An analog calculation is to tap the handful of spaghetti down on the countertop and simply pick out the protruding longest piece. Digital computers are quick with a fast clock and lots of clock cycles, but don't sell short analog computers and the 912e L-Jet analog ECU. Maintain everything properly and the fuel mixture should be good - close to that 14.7:1 ratio.

I do like what WFBowen says about uncluttered and quieter engine compartment.

Tom Zuraw

[Nige-912E]

Cheers for the excellent info, it took me a couple of reads to take it all in! I have been running the car without the air pump for over a year as its bearings were shot anyway, other than that everything else is stock, for the moment. I will aim to keep the EGR system but will at some point replace the TR's somehow.

[david c.]

I am looking for a set myself. If anyone has one, let me know. Thanks,
David