Yesterday i installed my new Forge DV. I used the yellow spring. (was i supposed to put in the spacer??) Anyway now the car seems to spike really hard. It pins itself past 1.5 in 2nd gear. Now that scares me so i wont let it happen again but. Can some one tell me where to look to see what the problem is. The only thing i could think of was the vaccum lines to the wastegate or factory boost control selenoid . I know they do not have anything to do with the DV but i tought that maybe i pulled one out and the wastegate wasent oppening. I couldnt find anything wrong! The DV shouldn't have anything to do with boost control on throttle, i mean the only thing it could do is leak not cause spikes right! Please help im confused!!!

 

it s very comon for the 05 to boost spike, i ahve the jdm mr DV and i spike to 24 psi once in a while, it s not a problem don worry about it, as long as the boost is not constant u wont hurt your car

 

This is not good advice in my opinion. The guy has a problem that did not exist previous to the DV swap. Just because your car spikes in its current condition doesn't mean his should suddenly spike higher than it used to. This indicates a problem that should be diagnosed more closely. Also, you shouldn't spike anywhere NEAR 24psi with stock boost. We only peak at 20.3psi, and you only go a little higher than that if you roll into boost in top gear. If you have an MBC and are saying that you spike to 24, then that has nothing to do with having an 05...that just means your boost is turned up too high. I only hit 24psi at the track on race gas. I never let it spike higher than 22psi on pump gas.

EMR8, I'd do a quick and easy test by re-installing the stock DV, then going out to check your boost again. If the problem persists, then you have an issue not related to the Forge DV that may have occurred during the installation process. If the problem goes away with the stock DV, then you will need to do some more research on what spring is proper and whether or not to use the spacer you referred to...

 

i have no boost controller, bt i have observed boost spikes in my evo and friends evo ( all 05) goign up to 24psi ( maybe boost gauge inacurracy in high boost reading i dunno) in 3rd, 4th and 5th gear , the reason y it might go that high is because we all have TBE.

 

That IS the reason - it's your TBE (the downpipe mainly). This is causing you to overboost, so you should get an MBC to bring it back down. 24psi is way too high and is definitely causing knock, especially in the peak torque range where the factory tune is very lean. Now, on race gas, leaving it like this would get you tons of power, but driving like that on pump gas is a no-no.

 

even if it goes to 24 for less than half a second? and doesn t always do it it s only from a roll in the higher gears

 

Yeah, because your entire boost profile is higher. A spike of 24 means you are running 22psi or more through the majority of the range. It's not like you went from 20.3(spike)/17(taper) to 24(spike)/17(taper); you are now at 24(spike)/20(taper). Everyone spikes from a slow roll-on, but if you are spiking that high, your boost is too high. As I said, I set my MBC so that it only spikes right at 1.5bar (21.75psi) or a little bit higher in 5th (22psi), but any higher than that and it knocks like crazy in the mid-range.

 

Same here. 24 psi on race and 21 on pump.

 

i get 23-24psi spikes rolling into boost in 6th...no MBC,no reflash,stock ecu

 

You Guys Rock! Thanx. I will try the factory one again and see. I had this prob on my STI but i didnt put a DV on besides the stock one. The fix for the suby was to port and polish the wastegate! But if it didnt do this proior to the DV im not sure how the DV is realted unless i did some thing wrong!

 

weird i never experience any knock tho, i should hear it or feel it if the car was knocking no?

 

glad i am not the only one

 

No, you wouldn't know it or hear it. There would be less power than if there was no knock, but it wouldn't really register on the butt dyno. You'd have to see it on a dyno or do some logging to see that your timing is being pulled.

You're definitely knocking...people never know. They just add mods and think everything is cool without ever going to test it and see what's going on via dyno'ing or hitting the track.

 

That's different; he has a 6spd, which means in 6th gear he has much more load, which causes an artificial spike. He doesn't even have a boost gauge that reads over 21.75psi, so he doesn't know how high it is spiking. You have a TBE, which is causing it to be higher than stock.

 

all right thanks i ll try a mbc nxt time i go to the track and see how i do.
thx for the advice