[Diy_efi] Knock retard and Race gas

[James Seabolt]

At 02:13 PM 7/11/2006, you wrote:
>Isn't there someone on this BB that has a masters degree in Internal 
>combustion??? if not Others might know. On a local club board we are 
>discussing higher octane race fuel ( 100/103) vs standard 98/93 pump fuel 
>and knock. We all know how well it will reduce some knock (KR) that our 
>3800 series 2 Supercharged ( pontiac grand prix 97-03) cars from 
>compression ( supercharger) of the air mixutre ( which heats it)... It wil 
>reduce the knock via more complete combustion and reducing the KR we get 
>form the supercharger... the question comes up
>
>   If a car has 0 knock ( detonation) and you put hight octane gas in the 
> tank for race purposes, does it give you  an advantage, or are you 
> waisting your money??? Personally I think that even if you dont get the 
> advantage of reduced knock your still getting a better combustion and 
> therefore a more power from the cylinder... Yes/NO


I had no luck running a knock sensor on my 1980 Fiat Spider. I ended up 
taking it off and going with a system that retards the timing as soon as 
the turbo kicks in. This car has a C/R of 8:1 and before I put the turbo 
on, the sensor said it knocks at high RPMs. There is no way this car should 
knock without a turbo.

Interesting I put some 114 octane gas in it and the meter showed less 
knock. This was before the turbo!

Someone told me if an engine has allot of piston slap will confuse a knock 
sensor and I think that was what was happening.

I replaced the head gasket a couple of years ago but the rebuilt engine 
block has about 60K to 70K miles on it. So whatever is going on in my 
engine must not be causing any problems.

I replaced the head gasket because Fiat 124 Spiders have really bad 
designed cooling systems. The radiator is lower than the cylinder head for 
one thing and if the radiator cap is not functioning properly the fan will 
kick on at a higher temperature than 190F. My fan was kicking on at 235F!

I've been meaning to mount a fan blade from a Lada Niva and bolt it 
directly to the waterpump to get rid of that troublesome electric fan. I 
just haven't done it yet because my fan spacer I made did not turn out too 
well. And I got other projects I've been working on.

The head gasket didn't blow but was leaking oil in all the usual places so 
I thought I'd replace it before it got any worse.

60K is probably the life of a head gasket on an old Fiat twin cam.





James Seabolt
Tennessee, United States
Homepage --->>> http://users.chartertn.net/jseabolt/

2003 Subaru Baja
1980 FIAT 2000 "turbo" Spider
1968 Ford Fairlane 500 (Not a Ford Galaxie!!)
1987 Yugo GV 1500cc also turbocharged
1979 Brava four door, 5 speed
1980 Brava four door, automatic, power steering