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Discussion Starter #1
Anybody know the answer to this question?

Reading the online Motorsport magazine Nov. 1991 issue, describing the Alfa Romeo 164 3.0 Cloverleaf the author stated the manufacturers claims of extensive modifications to the engine to avoid 4 valves per cylinder, changes included:-

1. Enlarged intake and exhaust manifolding
2. Elevated Compression Ratio
3. A camshaft profile shared with the Alfa SZ.

All three distinctions were mirrored in the SZ sales publicity.

I know the cloverleaf ECU, AFM and pistons were specific to this model if compared to the Lusso and standard 164 models so with all modifications combined the increase in HP/Torque seems logical.

But...

the non Cat equipped Cloverleaf claimed 200bhp at 5800rpm and 198Lb/ft at 4400rpm. The SZ/RZ type 61501 claimed 207bhp at 5900/6200 rpm and 185 Lb/ft at 4400 by comparison. According to a number of websites and SZ/RZ owner groups standard cars, not trophy versions, routinely produced between 220 and 240bhp on rolling roads.

How..?

Would the tubular exhaust manifolds fitted to the SZ/RZ really make such a difference?

I do not doubt those owners claims, but would like to understand how the Alfa engineers produced that extra bhp power in the SZ/RZ engines and would be interested by the torque readings standard cars were producing, as they are not mentioned in the articles I've seen.
 

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The 164QV 12V has long runners so it has lower peak HP. I really doubt those dyno numbers. Dyno numbers are meaningless if done without context, when you consider the same car at dyno A gives 200 bhp and at dyno B gives 220 bhp. Dynos are only good for measuring power before and after modification. I had a 12V engine similar to the SZ, but compression was up a bit at 10.5:1 compared to the SZ's 10:1. The headers are much better compared to the cast manifolds. I now have a 3.2 24V in the 75 and even at 6000 rpm it puts out 240 wheel hp on a dynapak. So that's going to be more than a 156 GTA, but I attribute that to the shorter 75-style runners. I have numbers for long and short runners and the short runners gives more power.
 

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Fascinating information 75evo. You confirm what I have understood trolling through the gtv6 .com and stratosec .com discussions.
Can I ask whether The 12v engine to which you refer, had "s" type (cloverleaf) pistons before you increased its compression ratio and did you keep them or replace with an after-market set . If it was an "s" block and heads do you recall whether your final 10.5:1 CR tune was dictated by camshaft lift or other criteria?
On a slight tangent, I am considering the RJR 570 or 590/744 set, so value your experience based opinion on the benefits over stock 64301 cams, how would you make best use them by way of engine prep?
 
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