Eliminating spike

[GrndNatnl]

Plain and simple question. I searched and cannot find an answer that makes sense...

How can I eliminate bad boost spike? I dont like looping the boost line from the compressor to the actuator, due to the severity of the lag in spoolup. Even though I get no spike that way, I like the fast spoolup using the solenoid. I replaced my old wastegate solenoid with a brand new one. Also a new adjustable actuator with very little milage on it.

I have like a 3-4 psi spike, weather its from a standstill or a roll at any speed, and it knocks BAD on the spike. This has to be stopped! I have my boost set at 15 psi for pump gas, and it does not knock at all during steady boost. The spike is causing, in some cases, audible detonation and KR. Really ticks me off that I cant just thump the gas and be gone without so much spike.

Stock turbo (rebuilt at one time), stock intercooler, new boost solenoid, fresh stock adjustable actuator, stock exhaust elbow & the 2-piece 3" downpipe.

What the FRICK? How can I stabilize or at least minimize this spike before I go nuts???

I take it adding dual solenoids is only for boost command setups? I was thinking of going that route, but I dont have the cash, and I feel its unnecessicary for my car anyway. Any feedback appreciated.

 

[Turbo6inKY]

Have you tried one of the "Heavy Duty" wastegate actuators?

I had an adjustable on mine once upon a time, bought it at the Nationals right after I got the car. Lo and behold, nasty boost spike. When I pulled it back off the car and fiddled with it, I noticed that the factory actuator was much stiffer than the adjustable I'd bought. So, I slapped the factory one back on. Boost spike went away. My theory is the things are so flimsy that they simple take too much air to start moving.

I control my boost with a ball/spring type MBC I scarfed from a Subaru guy, though I'm toying with the idea of an electronic unit. I'd like to be able to drop the boost a couple pounds in 3rd and 4th gear for safety, and you can't do that with an MBC or a shortened actuator rod.

 

[Whtlightning]

Aren't the HD actuators for applications above 21psi. I know Kirban sells a HD one, but I believe they recommend a stock actuator for between 14-20 psi.

 

[Slow91z]

I think the HD actuator is for 18 PSI Minimum...BUT I can say that i have used a HD Actuator below that....It just spooled REALLY slow

 

[420]

FWIW, I was never able to get the HD actuator any lower than 17/18 #'s on a T64-1.

 

[iamjeff]

i have a hd actuator, and the least amount of boost i can get on it is 16. could a electronic boost conrtoller get me down into the 14-15 range? im happy with 16#, but i have to be running my alcohol to prevent knock. i would like to be able to reach a boost level where knock isnt a problem.

-jeff

 

[TurboJim]

Originally posted by GrndNatnl
I have like a 3-4 psi spike, weather its from a standstill or a roll at any speed, and it knocks BAD on the spike. This has to be stopped! I have my boost set at 15 psi for pump gas, and it does not knock at all during steady boost. The spike is causing, in some cases, audible detonation and KR. Really ticks me off that I cant just thump the gas and be gone without so much spike.

Way I get around this in most cases, and I'm sure Eric is aware of this, is to at the anticipated point of the spike, lower boost DC, then put it back in the next frame. This way the turbo is told to "slow down" just before it hits max boost, then the next frame it levels off.

Seems to have worked for me in most cases.