Couple of questions about the SC

F

FlyingLow90

Registered User
when i started getting into cars when i was younger i was always told never use a platinum plug in sc or nitrous cars. it is puzzling me that these cars us platinum plugs. plus no where i go carries the right plug for me. where can i go to get some plugs and what besides bosch do i stay away from.

also being a sc car normally they would be low compression. if the SCs are low compression why do we have to run high octane.

lastly i dont understand what i hear about intakes and exhaust. when putting free flow exhaust and intakes on why do we loose boost but gain power. sorry for the dumb questions but my freinds and i seem to be fighting over the reasons for each so i would just like to know for good.
 
There are several different place and types of plugs to buy. I opted for the OEM plugs straight from the dealership. A lot on the pricey side, ($10.00/plug) but they work.

SC's have to run high octane fuel because under "boost" the compression ratio increases. I don't know the exact mathmatical formula, but on our 8.0 compression ratio cars I think we approach a compression ratio of 16.0:1 at 14.7 psi (1 bar) or 2 times normal atmospheric pressure. I know it's not exact, but it's closer than 8.0. Basically, forced induction is putting more air into the chamber than could go in under normal atmospheric conditions.

Lastly, boost equals back pressure. When you see 10 lbs of boost on your guage, what you are seeing is the result of back pressure created from exhaust, heads etc. If you free up the exhaust, there is less back pressure and the air travels more freely in the system. More air can flow into the system because of that. More air is more power. More air does not mean more boost. The less boost (with out changing any drive ratios for the supercharger) means that the overall system is more efficient. Boost is explained well at the magnum powers website where the talk about the magnaport supercharger. I can check and post the link when I get home.
 
AutoLite Double Platinum

I heard somewhere (probably on this site) that the MotorCraft plugs were actually AutoLites, or AutoLite was the "New OEM" plug, or something like that.... Anyway, if you can't get MotorCraft plugs at a reasonable price, or if they are just unavailable, use AutoLite Double Platinum plugs. They are at least as good as MotorCraft if not better, and are generally available.
 
hello

personally i use bosch plugs in my 94 sc and the car runs the exact same, but who knows maybe its just my car all cars have there own attitude, i know in my uncles race shop weve done tests on different plugs and things for his race car and believe it or not most of them didnt make a difference, keep in mind that this is a 800 hp stock car to and things really do run better in a motor of that caliber, so you know the only way to be sure about the plugs is to get the ones it came with, but me im going to use bosch cause they really have worked great im my car, as long as you get the gap right youll probally be cool with a few different kinds, why dont you try a few and examine them after a month and see what they look like, maybe thatll tell you what ones you want. some people like some kinds and some poeple dont and i think im the only one that can say that bosch plugs actually worked for them, atleast thats all ive seen
 
WHAT TO USE

HAD VERY BAD RESULTS WITH THE BOUSH PLUGS..............WOULD SHUT OFF UNDER HIGH BOOST........WENT TO AUTOLITES DPP,S NO PROBLEM..FAST FREDDIE:rolleyes: :cool: :D
 
I have to agree with FREDDY, if your car runs good for any lenght of time on Bosch plugs it would be the first car I ever seen or known of that does. I cant count the times I have changed out Bosch plugs in someones car to get rid of a mysterious miss that developed shortly after a fresh tune up where they used Bosch plugs, and I'm not just talking about an SC either.
I have found that Bosch plugs make a good sinker for fishing however.:)
 
like i said cars have there own attitude at the engine shop we have all kinds of differents things that work on some engines and not the other, thats why i said try a couple different kinds and see what your best is, then youll know what your car wants, thats the only way to be sure is to let the car tell you what it wants not what you want it to have
 
FlyingLow90 said:
when i started getting into cars when i was younger i was always told never use a platinum plug in sc or nitrous cars. it is puzzling me that these cars us platinum plugs. plus no where i go carries the right plug for me. where can i go to get some plugs and what besides bosch do i stay away from.
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Ordinarily you wouldn't use plats in a performance application. Various theories have been floated, such as the platinum changing the chemical reaction like in a cataltyic converter. Or, more likely, the harder platinum just doesn't lose as many particlesto help spread the heat in the igntion "kernel". Plus there are the issues of high-speed glazing that happens to any plug in acceleration contests. A SB Chevy will improve it's ET's by about a tenth or so if you change the plugs after about 10 passes. Ford V8's tend to go about 15-20 passes, supposedly due to better heat dissipation from the plug.

However, in the case of the SC it is such a PITA to change plugs that platinum is the only way to fly. That and the increased wear from the DIS hitting the plug twice each cycle (one power one exhaust).

FWIW, I have regualr plugs in my Cougar (and they're WAAAAAAY overdue for change by about 30K miles) and it operates normally driving around.


also being a sc car normally they would be low compression. if the SCs are low compression why do we have to run high octane.
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As has been mentioned, the boost increases cylinder pressure which in turn increases the heat generated. Too much heat in the air/fuel mix will lead to the mix going boom before you want it to. This is called preignition. If the mix goes bang when you touch it off with the spark it called detonation. And yes they sound similar, yet different. Preignition is much more solid-sounding if you know what I mean. Plus the increased temp of the compressed air runs you closer to detonation with regular fuel. Any forced-induction engine requires premium fuel for these reasons.


lastly i dont understand what i hear about intakes and exhaust. when putting free flow exhaust and intakes on why do we loose boost but gain power. sorry for the dumb questions but my freinds and i seem to be fighting over the reasons for each so i would just like to know for good.
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Simple. These cars have VERY restrictive exhaust systems. The supercharged engine is just capable of creating more exhaust volume than the exhaust system can handle. So the supercharger just stacks more air on top of it. Put a better exhaust that can outstrip the 'charger better and the boost drops to about what it should've been in the first place.
 
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