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Discussion Starter #201 (Edited)
You're courting trouble - you'll have Alfaitalia on your case, HaHa!

But I'm puzzling over this cat problem. I have found a Audi A8 (4.2) cat which rated at 360 bhp. My idea is to bin the Alfa twin cat for this single cat.

I could then combine the two flex - pipes from the Autodelta Manifolds, fabricating a nice "Y - Union" into the single A8 cat. On the output, fit the two lambda probes, either side of the pipe from the cat.

Looking at the way the Alfa one is designed, the Lambdas are virtually in same position in any case with just the "Clarinet Reed" separating them. I just need the dimensions of the A 8 cat. It could make a neat solution. and it should get up to temperature as both banks will be heating it.

P.S. - a bigger cat so it could reduce restrictions even more, which would be helpful.
 

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Nah....I used to have to have one of those "£100 MOTs" on my unsilenced, race tyred , no lights (not actually an MOT failure if used only in daylight hours) Suzuki GSXR......but he would never let anything safety related go through. The bigger issue is if you get stopped by a roadside check....all to bloody common around here....might be different on your patch. That would be a grand fine for no dpf or cat (depending on petrol or derv of course) I don't want to pay. Personal choice really.

PS.Is it just me that "cut and paste" doesn't work for since the forum "upgrade"?
 

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Discussion Starter #203
PS.Is it just me that "cut and paste" doesn't work for since the forum "upgrade"?

Just you, by the look of things - normally me!
 

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Discussion Starter #204
You're courting trouble - you'll have Alfaitalia on your case, HaHa!

But I'm puzzling over this cat problem. I have found a Audi A8 (4.2) cat which rated at 360 bhp. My idea is to bin the Alfa twin cat for this single cat.

I could then combine the two flex - pipes from the Autodelta Manifolds, fabricating a nice "Y - Union" into the single A8 cat. On the output, fit the two lambda probes, either side of the pipe from the cat.

Looking at the way the Alfa one is designed, the Lambdas are virtually in same position in any case with just the "Clarinet Reed" separating them. I just need the dimensions of the A 8 cat. It could make a neat solution. and it should get up to temperature as both banks will be heating it.

P.S. - a bigger cat so it could reduce restrictions even more, which would be helpful.

Found this 3 way Cat on the Web. I think this is an easier option than having my current Siamese Cat modified. It is rated for N/A engines up to 4.7 litre so I think it should be big enough. And If I screw it up - the damage at £97 isn't going to be too painful. But if it solves the problem of that damned drone - that will do me!

I still have my Man - Cats but I cant see them ever going back on the car. And I can't think there is a second hand market for them.

2.25" AP Exhaust Heavy Load Catalytic Converter True OBDII - 608215
 

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Discussion Starter #205
Just done a little more research on Cats as I am concerned that I may have bought one (TWC) which is more restrictive than the Alfa "Twins". However, it seems :-

Three-way[edit]
Three-way catalytic converters (TWC) have the additional advantage of controlling the emission of nitric oxide (NO) and nitrogen dioxide (NO2) (both together abbreviated with NO
x
and not to be confused with nitrous oxide (N2O)), which are precursors to acid rain and smog.[18]

Since 1981, "three-way" (oxidation-reduction) catalytic converters have been used in vehicle emission control systems in the United States and Canada; many other countries have also adopted stringent vehicle emission regulations that in effect require three-way converters on gasoline-powered vehicles. The reduction and oxidation catalysts are typically contained in a common housing; however, in some instances, they may be housed separately. A three-way catalytic converter has three simultaneous tasks:[18]

Reduction of nitrogen oxides to nitrogen (N2)

  • 2 CO + 2 NO → 2 CO2 + N2
  • hydrocarbon + NO → CO2 + H2O + N2
  • 2 H2 + 2 NO → 2 H2O + N2
Oxidation of carbon monoxide to carbon dioxide

  • 2 CO + O2 → 2 CO2
Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water, in addition to the above NO reaction

  • hydrocarbon + O2 → H2O + CO2
These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running slightly above the stoichiometric point. For gasoline combustion, this ratio is between 14.6 and 14.8 parts air to one part fuel, by weight. The ratio for autogas (or liquefied petroleum gas LPG), natural gas, and ethanol fuels can be significantly different for each, notably so with oxygenated or alcohol based fuels, with e85 requiring approximately 34% more fuel to reach stoic, requiring modified fuel system tuning and components when using those fuels. In general, engines fitted with 3-way catalytic converters are equipped with a computerized closed-loop feedback fuel injection system using one or more oxygen sensors,[citation needed] though early in the deployment of three-way converters, carburetors equipped with feedback mixture control were used.

Three-way converters are effective when the engine is operated within a narrow band of air-fuel ratios near the stoichiometric point, such that the exhaust gas composition oscillates between rich (excess fuel) and lean (excess oxygen). Conversion efficiency falls very rapidly when the engine is operated outside of this band. Under lean engine operation, the exhaust contains excess oxygen, and the reduction of NO
x is not favored. Under rich conditions, the excess fuel consumes all of the available oxygen prior to the catalyst, leaving only oxygen stored in the catalyst available for the oxidation function.

Closed-loop engine control systems are necessary for effective operation of three-way catalytic converters because of the continuous balancing required for effective NO
x reduction and HC oxidation. The control system must prevent the NO
x reduction catalyst from becoming fully oxidized, yet replenish the oxygen storage material so that its function as an oxidation catalyst is maintained.

Three-way catalytic converters can store oxygen from the exhaust gas stream, usually when the air–fuel ratio goes lean.[19] When sufficient oxygen is not available from the exhaust stream, the stored oxygen is released and consumed (see cerium(IV) oxide). A lack of sufficient oxygen occurs either when oxygen derived from NO
x reduction is unavailable or when certain maneuvers such as hard acceleration enrich the mixture beyond the ability of the converter to supply oxygen.

Credit to Wikipedia for the above information.

However, in the full article it leads me to the conclusion that, given Lambda, when MOT -ed, was 1.004, 14.75:1 AFR, in closed loop conditions, perhaps the cat I have bought may be helpful in maintaining good emission control. I am still puzzled about the way Alfa placed the narrow band probes in the "Collector". Essentially, due to even the slightest back pressure from the silencer which follows, they are seemingly sharing the same pipe. So I may be over - anxious about having to physically place them in the single output of the replacement cat unit.
 

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Discussion Starter #206
I have Just delivered my old 3.2 JTS to Scholar Engines for stripping down and assessing any major problems with regard to a re - build. But this engine will be sold with the reground original, balanced crankshaft, or new balanced one, plus one new con rod. It is going whole or separate block and heads. Rings and pistons will be checked. If anyone is interested in it after cleaning and assessing then do let me know.

I would recommend Scholar for the rebuild as they do build competition engines, they do not charge the earth for their services and their knowledge and expertise is in my opinion second to none.

However, whilst waiting to organize the dynamometer run I have been doing some calculations on the work undertaken so far. I have been given some figures as to what to expect and on the basis of a median figure, these are the anticipated changes I expect from my modifications/Camshafts/Manifolds. Accepted this is a new engine, but I am basing it on my old one which failed at Bruntingthorpe.

RPM Original Power Revised Power Revised Power with Manifolds.
2250 92.1 BHP 105.92 BHP 113.92 BHP
2750 112.57 BHP 129.46 BHP 137.46 BHP
3500 143.2 BHP 164.70 BHP 172.70 BHP
4500 197.07 BHP 226.62 BHP 234.62 BHP
6000 251.33 BHP 289.03 BHP 297.03 BHP
6670 266.20 BHP 306.70 BHP 314.70 BHP

For those interested, the salient figure is a conservative 15% torque increase across the range and a quoted figure of recovered losses from the Autodelta Manifolds of 8 BHP. It remains to be seen what the Dynamometer results will bring however.
 
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