side effects of boost increase on 03/04 cobra

Prometheus

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May 19, 2004
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I'm not referring to the obvious gain of horsepower here. What I am concerned with is if there are any serious detrimental effects to using a smaller pulley (or any other methods to increase boost) on the stock Eaton blower. I was reading the latest and greatest MM&FF magazine (March '07) and the "Under Pressure" article mentioned that increasing the boost on the blower will exceed the design limitations of the boost bypass valve, and could be detrimental to the blower. The author contends, "The increase in airflow taxes the flow rate of the stock bypass valve. Since the reversion wave (when the throttle is quickly shut) cannot escape through the bypass valve, it has nowhere to but back out the rapidly spinning blower. At the very least, this will likely shorten the life of the blower."

If anyone could either confirm or deny this information I'd appreciate any comments. Thanks!
 
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Eaton works OK up to 15-16 lbs boost, then experiences drop off and vastly increased heat with little or no gain in HP.

Blower porting can allow the eaton to run 500 or RWHP with a 2.8 upper pulley and still do well, anything over that and you should consider a blower upgrade, whipple, KB etc.
 
I'm not referring to the obvious gain of horsepower here. What I am concerned with is if there are any serious detrimental effects to using a smaller pulley (or any other methods to increase boost) on the stock Eaton blower. I was reading the latest and greatest MM&FF magazine (March '07) and the "Under Pressure" article mentioned that increasing the boost on the blower will exceed the design limitations of the boost bypass valve, and could be detrimental to the blower. The author contends, "The increase in airflow taxes the flow rate of the stock bypass valve. Since the reversion wave (when the throttle is quickly shut) cannot escape through the bypass valve, it has nowhere to but back out the rapidly spinning blower. At the very least, this will likely shorten the life of the blower."

If anyone could either confirm or deny this information I'd appreciate any comments. Thanks!
As far as the bypass valve reversion wave theory as it relates to damaging an Eaton, it's the first I've heard of it. The Eaton is a really tough little blower and reports of failures are far and few between. All they do when spun hard like that is get really really hot and eventually the inner teflon rotor coatings wear off quicker.

Do you believe the article in MM&FF is stating the stock boost bypass valve is incapable of venting off enough boost when the engine is suddenly unloaded? I imagine there may be an initial hit on the bypass if you were in max boost (WOT) and then you just chopped the throttle off, but enough to do damage?

Personally I think it's the additional heat which causes the most engine wear & damage when a stock Eaton is spun past it's peak efficiency level. That's why most people who want to stick with the Eaton eventually get it ported and add a larger HE. The porting allows it to flow better at those high RPM's and it also reduces the amount of heat generated.

So to try and answer your question... :D

...will adding just an upper pulley with no other supporting mods (like better cooling and blower porting) eventually cause damage to my motor? Probably not for quite a while, but eventually if the car is beat on hard enough and long enough it may end up melting the teflon on one of the piston skirts, or even melt a piston. The PTW on these motors is too tight and the added heat from an over spun Eaton doesn't help. As for the blower itself, it'll be fine.

U.M.
 
As far as the bypass valve reversion wave theory as it relates to damaging an Eaton, it's the first I've heard of it. The Eaton is a really tough little blower and reports of failures are far and few between. All they do when spun hard like that is get really really hot and eventually the inner teflon rotor coatings wear off quicker.

Do you believe the article in MM&FF is stating the stock boost bypass valve is incapable of venting off enough boost when the engine is suddenly unloaded? I imagine there may be an initial hit on the bypass if you were in max boost (WOT) and then you just chopped the throttle off, but enough to do damage?

The article does seem to indicate that increasing the boost will exceed the capacity of the boost bypass valve to vent off the boost. Here are a few sentences that preceded what I quoted initially, "The factory bypass valves included on the Lightning, Cobra and GT 500 were obviously sized to meet the flow needs of their respective factory power outputs. Unfortunately, it is difficult to increase the size of the bypass valve for those high boost applications. The problem arises when when individuals crank up the boost on their factory Ford motors." (The sentences I initially quoted follow this.)

The problem is the author never identifies what he considers "high boost." But his statements lead me to think that any increase in boost could cause a reversion wave that would harm the blower. :shrug:


Personally I think it's the additional heat which causes the most engine wear & damage when a stock Eaton is spun past it's peak efficiency level. That's why most people who want to stick with the Eaton eventually get it ported and add a larger HE. The porting allows it to flow better at those high RPM's and it also reduces the amount of heat generated.

So to try and answer your question... :D

...will adding just an upper pulley with no other supporting mods (like better cooling and blower porting) eventually cause damage to my motor? Probably not for quite a while, but eventually if the car is beat on hard enough and long enough it may end up melting the teflon on one of the piston skirts, or even melt a piston. The PTW on these motors is too tight and the added heat from an over spun Eaton doesn't help. As for the blower itself, it'll be fine.

U.M.

Thanks U.M. Do you think its worth getting the Eaton ported? I'm not certain if the cost would justify the horsepower gains. But then again, I'm not certain how much horsepower porting is good for! I'll have to look that one up. I'm seriously looking at the SLP performance package for the Cobra and calling it good.