Overboosting?

[nuffsaid]

Hi all

I recently had a split dump and hi flow cat + 3" exhaust fitted to my GTT recently.

Last nite was pretty cool and I took my car for a little thrash. Prior to the exhaust mods, the boost guage would read only a little over 0.5km/cm, but last night I found that the boost guage was reading a bit under 1 kg/cm.

It looks like my car was boosting up to almost 12-13psi. Other than the exhaust, my car is stock and I dont think I will be modding it much further.

When giving it, in low revs, the boost needle climbs at hits around 0.6km/cm and stays there until about 5000rpm at which the boost needle jumps to like 0.8-0.9kg/cm which is close to 12-13psi maybe. I also found that when the car hit clost to 0.8-0.9kg/cm, the car seem to stop accelerating as hard closer to redline, I think this might just be the car's protection against over boosting? Could this be right?

I didnt think a full exhaust would have increased my boost by that much.

I want to limit the boost down to about 10psi for safety reasons. How can I go abouts doing this? will the $35 boost tap help? or will I need an electronic EBC?

Thanks all

[Freddy Kruger]

buy a boost controller of some sort. theres a thread in the Forced induction section title "a boost controller for $22" or similar... just put it on and loosen it so it makes less boost. easy peasy lemon squeezy

But wait for conformation from someone else, but that is my understanding of it.

Edited February 28, 2006 by Freddy Kruger

[nuffsaid]

Yeah looks like the car is spiking due to the exhaust, I dont really like the idea of spiking as I noticed that my car kind of pulls back a little when it does spike, probably some protection mechanism in the car itself.

So a boost tap will stop spiking guys? Or is it more for just upping the boost?

[race_snooze]

well with the boost tap, mine spikes at .9bar before dropping back to .75bar so 14.5psi to 12psi and this is an apexi bleed valve.

[nuffsaid]

I wonder if the Turbotech $35 boost tap that everyone raves about on this forum will work better than the Apexi since its a tap and not a bleed valve.

[SECURITY]

ebc

[Oblivion]

I have seen no spike really on mine....when it is cold it gets more boost of course, but i dont have a prob with spike atm, but then again i only have a front mount and no exhaust ...but soon...

[nuffsaid]

Well with my exhaust being too loud for my liking I decided to change my muffler back to the nismo one.

Basically I left the 3" piping and the resonator from my new exhaust, but because it had a flange just underneath the diff, I had an exhaust shop make some piping from my old muffler to that flange.

Only problem is that it is 2.5" piping from the muffler to the diff flange (had to be done this way because the muffler is a 2.5" inlet one). Exhaust shop said the effect on performance is tiny.

The car does not start boosting until a bit later compared to when I had the big loud exhaust. And I am no longer boosting more than 11psi which is good. (Some of you may say the more boost the better, but I think its safer now). Do you think the exhaust is too restrictive at the back and so caused this drop in boost?

Boost goes up to about 0.6 bar, then moves towards 0.7 max 0.75 bar. No more 0.9 bar which was getting scarey for my car. No more acceleration slow down near redline.

Is it worthwhile investing in a EBC to get 0.7 bar boost at full boost? My car seems to full boost at 0.6, but it always creeps up a bit more towards redline. I want it so that past 4000rpm, its always on 0.7.

Edited March 6, 2006 by nuffsaid

[The Mafia]

my R33 did that after I installed the exhaust and FMIC.

Wanna know how I fixed it?

Installed a powerfc and got it tuned. Now with the $22 boost tap, it is within .5 of a psi.