What Limits Boost?

[W0rp3D]

Today i decided to up my boost in preparation for calder tomorrow, i was running around .9bar and at 1.0 (which it only ever flared to once) it broke down, since then i have put new plugs in and gapped them to .8mm, the old ones were at 1.1, i have a new k&n panel filter and a new 3" Xforce hi flow cat (the old one was the factory 2.5") and i have also changed to a blitz lm return piping intercooler.

The problem is today i couldnt get over .95, the highest it has been is 1.3bar when i was playing around with the duty cycle on the avcr so i know it can do the 1bar i was aiming for, in the end i took the vac line off the turbo completely and still only got a best of .95, the only way i could get it higher was to remove the panel filter and even then it only went up to 1bar, then only things i can think of is that the turbo is just running out of steam, which is odd because it has spiked past this point before or maybe the rubber pipe between the afm and turbo is sucking closed (only just thought of this whilst typing), so the question is what else should i look for that could be holding the turbo back, my set up is:

standard ecu

standard injectors

standard fuel pump

k&n panel filter

jjr one piece split dump

3" exhaust system with Xforce hi flow cat

hi flow turbo with t4 front (i believe) and vg30 rear and hks adjustable wastegate(disconnected)

avcr also disconnected

Will be heading off to calder tomorrow so if there is any easy fix (might put a bit of 3" pipe in the intake pipe in the morning) any one can think of your help would be appreciated.

Also i know a lot of ppl dont think much of them but i put a bottle of octane booster in when i filled up today, every little bit helps.

Edited October 18, 2008 by W0rp3D

[Strik3r]

a highflowed turbo should get to 18psi easy. Things to look at:

- intake pipe like you said (easy fix, brace the pipe or replace it)

- exhaust restriction (collapsed cat)

- Problem with the actuator on your wastegate. wastegate pressure is probably around 0.95bar.. so if your not getting any higher, i'd say your gate is opening when it shouldnt be. Check the AVCR settings and the actuator as well.

[Brocaine]

Had a similar problem on my RX7. Check vacuum lines running to BOV if your car is running one.

[W0rp3D]

- exhaust restriction (collapsed cat)

- Problem with the actuator on your wastegate. wastegate pressure is probably around 0.95bar.. so if your not getting any higher, i'd say your gate is opening when it shouldnt be. Check the AVCR settings and the actuator as well.

Better not be the cat, only put it in a week ago.

Atm the waste gate is not connected, so essentially im running unlimited boost

Had a similar problem on my RX7. Check vacuum lines running to BOV if your car is running one.

Checked for vac leaks yesterday, could not find any, i will remove the bov and put a block of plate on to make sure though.

I guess i will just have to run it as isand see what happens

[R31Nismoid]

Atm the waste gate is not connected, so essentially im running unlimited boost

You mean the actuator isn't connected?

If the actuator isnt connected, then all thats gonna happen is the internal gate flapper will blow open

1. Causing not enough boost

2. Poor response

The job of the actuator is to control the gate flapper. If your not using it, then thats the reason you cannot increase boost past "X" as its all being vented via the gate when it needs to go via the housing.

Removing the actuator doesn't create unlimited boost. Its the opposite. Welding/wiring the gate shut creates unlimited boost... you've got it backwards.

[Adriano]

Ash, i think he means he just remover the vac hose(boost signal) in which case it should run fairly unlimited boost. Although there is obviously a problem, my point is there is no point running anywhere near 14 psi with a stock ecu, as it will be running so rich, with no timing that it negate any power increase the added boost would create.

[joeyjoejoejuniorshabadoo]

I'd be setting it lower for a track day with the stock ecu... Not higher

[W0rp3D]

You mean the actuator isn't connected?

If the actuator isnt connected, then all thats gonna happen is the internal gate flapper will blow open

1. Causing not enough boost

2. Poor response

The job of the actuator is to control the gate flapper. If your not using it, then thats the reason you cannot increase boost past "X" as its all being vented via the gate when it needs to go via the housing.

Removing the actuator doesn't create unlimited boost. Its the opposite. Welding/wiring the gate shut creates unlimited boost... you've got it backwards.

Ash, i think he means he just remover the vac hose(boost signal) in which case it should run fairly unlimited boost.

That is what i meant, anyway took it for a spin this morning and all of sudden im getting 1.2bar, it was not breaking down or hesitating or any thing so i left it that way, being my first time at a calder i took it relatively easy for the first 2 runs and then on the third i got to the top of second and the revs died, changed to third and the revs died again, i back off after that and cruised across the line, did not run any more after that.

Im assuming its the rubber pipe sucking closed as there was no pinging (although it was hard to hear with the helmet on) and no breaking down or spluttering and as soon as i backed off it was fine till it hit high boost again.

Any way i will fix the rubber hose and attach the vac line to the wastegate again and prepare for the next street meet.

Here is my time slips.

[R31Nismoid]

2.5 60ft

you need to be around 1.9-2.0

[W0rp3D]

2.5 60ft

you need to be around 1.9-2.0

this grasshopper has much to learn master, i did all that my teachings have taught me master, my teachings have taught me that my average road tyres are not good for 60' master, this grasshopper will rectify that on the next meet master

Was only really out there to get some practice and get use to the car on a track and the track, next time i will be more prepared and will do better.

Edited October 19, 2008 by W0rp3D

[R31Nismoid]

nah roadies shouldn't be "too" bad.

I was 2.0-1.9 with just 225/16

Drop the psi a bit too helps

[W0rp3D]

nah roadies shouldn't be "too" bad.

I was 2.0-1.9 with just 225/16

Drop the psi a bit too helps

I have 235 18's, didnt really have much practice time, will be back there again on the 22nd of november to try again.

[Adriano]

I would try turning the boost down to 12 psi (.8 bar) and do a run, i would bet the MPH goes up.

[W0rp3D]

I would try turning the boost down to 12 psi (.8 bar) and do a run, i would bet the MPH goes up.

We will see how it goes, im hoping to get a tune by the time i go back on the 22nd of nov, also hoping to have an external gate as well.