Boost Reduction?

[Camptron]

Hi,

This is my first real post on this forum so if i have posted in the wrong thread sorry.

I recently bought an R34 GTR (my long time dream car until the R35 GTR), completely stock. Anyway I took it on a long drive (about 2 hours) and i noticed that after a while, instead of boosting to 0.8 bar the boost dropped down to about 0.6 bar.

Intercooler temp was at max 25c, water temp was at max 85c, Oil temp was at max 90c during the drive.

Has anyone had this happen to them and if so is this a standard thing for a GTR to do?

I am about to install a 3.5inch exhaust, pods, apexi power fc and apexi boost controller. I would like to boost up to 1bar. Would this eliminate my problem in the future?

Cheers.

[Camptron]

Just went out for a spin then to see if it would boost at 0.8bar again. It did for a few squirts, then after that it went back down to 0.6bar.

Any thoughts?

Cheers.

Edited September 20, 2009 by Camptron

[mosquitocoils]

Might sound like an incredibly simple thing, but it could be loose clamp/hose fittings etc. To me, what you've described is once the car is warmer, some boost pressure is leaking a little... which I've been told is more likely to happen when the air is warmer as it can sneak through smaller gaps.

Not sure how true that is, but it did happen on my stock BOV on my 33 GTST. Gasket wasn't sitting properly and had a tiny, TINY gap, so I was loosing pressure through that, but only once the car was at normal warm temperature.

[Camptron]

Thanks for the reply mosquitocoils. I think you might be right.

What did you use to locate the boost leak?

[Camptron]

Sorry double post.

Edited September 20, 2009 by Camptron

[mosquitocoils]

For me it was just a trial-and-error thing, and my problem was accompanied by a high pitched squealing noise - like releasing the air from a balloon while pinching the opening so I could roughly tell the location in my engine bay.

You might be able to find it by getting the car nice and warm (take note if you can get the car to only get to 0.6 bar ONLY when warm), let it idle, open the bonnet and see if you can hear any hissing or sucking noises. Play with your throttle and see if you can get some 'leaking' noises to happen as well and take note of where they come from.

Common places would be from intercooler piping clamps being loose - I undid and took off/put back on all the clamps I could see in the upper area of my engine bay as a precaution.

I then replaced much of the vacuum hosing going around the place - it's all pretty old by now and I figured it wouldn't hurt it any, and it's piss easy to do yourself. Also check your air intake piping too.

Small splits or hairline cracks in any of these three places could give you leaks.

Good luck man, let us know how you go.

[old mate]

im not 100% sure myself but i know when u put a larger exhoust on the car the boost does rise a bit. so this has me thinking that maybe once your standard dumps and exhoust gets hot you get a restriction hence the .6 instead of .8.

[Camptron]

I hope your right old mate.

Im hoping to get the car into the shop sometime this week for the mods to be done, so we will see soon.

Cheers thanks for your help guys.