hosrom_951

22psi without falling off at redline?

SimonK

Ok just to be sure I asked this before here but did not quite get the answer.

I have superchips installed. This was done:

1. Boost control valve (plastic restrictor was removed from the pipe leading to the compressor.

2. Boost control valve was wired as to on when ignition turned on.

3. Aluminum restrictor was fitted into compressor hose on the intercooler pipe.

4. Chips were fitted.

First time round the aluminum restrictor was wrong size - overprotection kicked in. Then different size was fitted - now is fine and boost is at 14.8PSI in top gear and 14PSI 1-4th. (Thanks Danno - explained this one).

Chips give me boost earlier at 3000rpm and at the top end I think they roll off as stock chips.

Questions:

SO IF I SHIM THE WASTEGATE BOOST WILL HOLD LONGER AND WILL NOT AFFECT OVERPROTECTION ON CHIPS?

ALSO WILL I RUN LEANER OR RICHER?

THANKS GUYS I REALLY WANT THIS ONE ANSWERED?

hosrom_951

Basically, NO, you would not hit overboost-protection that is another function

Running leaner/richer depends on the boost level the MBC you have is set for

The Wastegate just holds your desired boost longer/to redline

SimonK

Thanks mate I better do it asap then.

hosrom_951

Just remember (hope this doesn't confuse you more ) The WG is to HOLD boost, you set the boost, you MUST watch the A/R ratios (through the WHOLE rpm range)..........

Your chips are for 15psi, don't go more/less, tuners like Guru Racing/Vitesse customize chips to run any level you want (almost), I know that Guru can customize chips to run 15psi~18psi, so you can raise/lower boost in that range.........

Get a boost gauge (stock ones are crap, they say).............

Danno

"No I have superchips - boosting at 15PSI.
So I guess overboost protection would become an issue if I shim?"

It can if you end up with too much boost. Typically shimming 4.5-5.0mm will increase boost by about 2-3psi across the board. So you'll need to get another restrictor that lets more air through to lower max-boost in the mid-range back down to 15psi. Bonus is that your high-RPM boost will be increased by 2-3psi, so you'll get a flatter overall boost-curve. But what the air-fuel ratios to make sure you don't go lean in the upper-RPms.

A lot of aftermarket chips are optimized for a falling boost-curve. I've got the latest GURU chip-kit customized for each customer's car at 18psi. Some people with just a shimmed stock wastegate will see a 18->15psi boost-curve. Others with aftermarket wastegates and the larger K26/8 turbos may get a flat 18psi boost-curve. But about half of those ends up with an 18-15psi boost curve as well. So we need data on your particular car to get a fully optimized mapping.