over boosting

[tjc]

so I have an EVO 3 turbo and even with the flapper on the waste gate wide open/actuator disconnected I still get 7 PSI of boost. I'm going to port the internal waste gate this weekend to see if I can get it to around 6 so it is safe on my stock nytro fuel system (AFR was 13.5 in a short blast with the gems setting on boost and wot maxed out). Lets say this does not do the trick, I have heard that lowering the RPM will alos lower boost. Say I get the RPMs down to 8200 or so, will that be enough to lower the boost?

I know the correct answer here is upgrade the fuel system and run 7-8 pounds of boost but it is not in the budget right now.

I guess another answer is external waste gate but again probably not in the budget.

I plan on doing some upgrades this summer but the way this winter is going I doubt I wil get more than a couple weekends on this thing this winter.

 

[powder muncher]

Where does your wast gate exhaust to?

If it goes right into the exhaust close to the turbine outlet you may have lots of back pressure that does not allow the system to work well.

That is why some systems have separated the waste gate exhaust from the main exhaust . You will also hear of divorced down pipes etc same thing .

Long story short your waste gate needs to go to a low pressure area in the exhaust to work properly.

 

[rxrider]

X2

 

[tjc]

it does combine close to the turbo, I was thinking the same thing you guys were saying so I ported the wastegate and enlarged the pipe from the wastegate to to the exhaust. Im hoping this will help. I think an external wastegate is going to be in the list for summer mods. That seems like the best option to me right now.

I have a muffler on it but it is a 3" pipe so I thought it would be ok.

 

[rxrider]

IMO the problem is not the pipe downstream of the muffler but the pipe in front of the muffler, in my view it's too narrow, may add to your overboost problem.

 

[gsxr]

I had to port my wastegate last year to lower the boost enough for pump gas.

 

[tjc]

well I have ported the waste gate, made some changes to the muffler and still cannot get below 7 pounds of boost. I have not held it wide open for more than probably 500-600 ft because my AFR is around 13 at 7 pounds.

What is the best way to get this to work with 7-8 pounds boost? regulator and pump? I Was wondering if apex injectors would fit and adjust the low end fuel with the CO settings? I have a purelogic box now and it runs great aside from WOT.

Do I need to mess with timing at 7-8 pounds of boost?

Im at sea level to 2000 ft. Stock engine pump fuel 91-93 octane.

 

[kinger]

At 7 psi your at the ragged edge of 93 gas. You need to get it down lower, timing may help a little but honestly you need more octane or less compression. IMO I would tear down and shim the head and run 9-11 psi and hold on!

 

[yooper1]

I run 9 psi with 93 and torco.

 

[gsxr]

Check your gauge with another manual one,
I had a brand new Autometer boost gauge that was out 3 lbs at 8 lbs , drove me crazy until I found it !!

 

[DooAssassin]

Its going to probably take more money solving this problem. Especially if you start divorcing the turbo. Instead buy a 125$ external fuel pump off ebay and enjoy. Live is too short

 

[tjc]

I think that is the route I am going to go. Im looking into pumps and regulators now. Why not just run the extra boost right? haha.