Boost Spike

[Wht87T]

I'm running a RACEgate w/ a manual boost controler. When running high boost it will normally spike up 3-4psi over what I set it to, then it will settle and hold solidly. Is there any way to get rid of the spike?

[turbo buicks]

how long are the boost hoses. longer hoses have been known to induce lag and cause spikes. if this is not the case, do you have a bleeder valve. if so i believe they have been known to spike. finally, if you dont like the spike you could try setting the BC a couple lbs. under what you desire. you wouldnt risk overboosting but you wont get the full boost you want in the end.

Hopefully someone has a cure. I have boost set to 17 on the street and upon the initial hit, spikes to 20 and then settles to 17.....

[turbo buicks]

i use a MBC also but with a ball/spring design. when i had it set for 15 psi it was pretty accurate and only spiked to about 16 psi a few times then quickly went down. of course when my car shifted to 2nd it dropped to 10 psi so i really cant say how long it held the boost there but it seems to work now that i have it set at 10 psi. it holds it there everytime and rarely fluctuautes but if it does its no more than a lbs. of boost.

[Chyke]

I am trying to fix a similar problem. While dyno tuning this past weekend, I had the boost pressured logged by the dynojet. I had boost set to 26psi by the gauge in the car. While reviewing the graph of the run: Boost pressure vs rpm vs AF, I noticed that my boost varied between 21 to 26 psi from 3000 to 6000 rpm. The AF stayed a consistent 12.5 to 1 the entire run. Any ideas??

[turbo buicks]

what type of boost control are you using(bleed valve, in car controller, ball and spring valve, adjustable WG, etc)? my car goes to 15 psi in first then to 10 psi in 2nd and slowly will climb and stop about 12-13 psi @ the top of 2nd gear. im thinking that its just the spring trying to regulate the wastegate. As soon as the WG opens the spring shuts off the boost to the WG and that closes the the WG and then boost climbs and the spring opens again and that opens the WG which then tries to keep boost steady. of course once the BC's setting is reached it opens the spring which opens the WG and the whole process is repeated. Chyke, tell us what kind of method you use for boost control. HTH

[Wht87T]

I'm running a bleeder valve inside the car. The vaccuum lines are somewhen lenghty. That could be the problem. I think the only way to get rid of the real problem is the bleeder valve. Just my .02

[Chyke]

We are running a manual valve inside the car. I believe it was purchased from ATR. It's the kind that after it's adjusted you lock it in place by pushing the knob down. To be honest, I'm not sure how I feel about it.

[Wht87T]

My boost dosent fluxuate between gears, its only coming out of the hole, then it will settle back down. I'm tryin to eliminate the boost spike.

[turbo buicks]

i think both of your problems are related to the length of your hoses. the more hosing the air has to go through, the longer it takes for the boost reading to get to the wastegte, hence the more spike you have. Wht87T, i believe if you get rid of the bleed valve and replace it with a manual controller that utilizes a ball and spring design you will get better boost control and maybe faster spool up b/c the manual controller holds the boost until its set level is reached where as a bleed valve bleeds off a portion of the boost. just a thought. everyone i have talked to around my town that knows about turbo cars basically that bleed valves are not the greatest thing for effective boost control. you can find the manual controller on ebay. there are a ton of them if you do a search for a manual boost controller. they are priced around $20-$25 usually. i say go for it and if it doesnt solve your problem its only $20. no big deal(i would see it that way, dont know about you). Chyke, i think my boost controller is like yours. mine has a adjustment screw that you twist it inward to turn up the boost and outward to lower the boost and when you have reached your desired boost level you tighten the lock nut on the bottom of the srew to hold the screw in place. does the way i adjust mine sound anything like how you adjust yours? if so we probably have the same type of controller. i think all the MBC's on ebay have an "L" shape to them and this is good b/c it allows you to use the stock wastegate hose and turbo outlet hose. it just plugs right into each of the ends and looks almost factory. it eliminates that "Y" fitting in the stock lines and boost solenoid. just remember to reconnect the electrical parts of the boost solenoid but not the pressure line to it so you dont set off any codes. you may also get faster spool up due to shorter hoses.
HTH

[Wht87T]

The problem was that the vaccuum line was too long by running it into the car. The installation of the vaccuum lines was also somewhat incorect. I re-routed the lines with the help from a diagram about wastegate plumbing on gnttype.org.

[Turbojorge]

It's funny how someones "problem" is another persons desire. My car would be way too rich out the gate if the boost didn't spike. Even after trying numerous chips, a 1-3 psi (depending on temp) spike was the only thing that would give me quick spool up at WOT.

Yes, I did extend my boost lines to achive this.