VF35 "safe boost" threshold.
 

Hey people,

Just a quick question. I've been trying to find out roughly what the safest maximum boost pressure is on a VF35 with an STi standard topmount.... to no success.

I've just had my car tuned, and in the midrange for roughly 2000rpm it generates 22psi...only to taper back to 17psi.

I picked my car up on Thursday and all was good. However, after doing a fair bit of "start stop" city driving today, I managed to hear it detonate. Not good.

I'm thinking that, due to the fact that it has only happened in city driving, the intercooler is probably heat soaked and thus creating relatively high inlet air temps....which is probably causing the detonation.

My tuner is coming out to my house tonight to trim it back, so I'd like to lower the boost.

Im thinking 19psi? Any opinions?

Forgot to mention....

The detonation seems stop as the boost level tapers back. It's only happened once and it only happens for a split second.

Hopefully nothing has been damaged :(

22psi+ easy, as proved by motec logging though you obviously need supporting mods and a FMIC + CAI would be included among these

I'm running a motec as well. Also has data logging enabled so I can keep an eye on things.

On the dyno they had it running with 45deg inlet air temps and everything was fine....

This is what I don't understand :(

I better mention the mods just to be safe...

- Motec M800
- Turbo back exhaust
- Stock intake but with K&N Panel filter
- GFB Stealth BOV
- Bosch Motorsport 910 pump

Everything else is bone stock.

get the waterspray 'automated' to spray at a set boost limit.

I reckon 22psi with a toppie's pushing it - 18-19's fine all day long.

Yeah he told me he can ditch the switch and just let the motec run the waterspray. Might be an idea.

Fred, your car runs 18-19psi yes? But it spikes to 22psi as well doesnt it? Bit different with your car though seeing as you have the FMIC.

I'll lower it to 19psi tonight I think. Might also trim back the timing a little bit just to be extra safe.

I had run 18.5psi on my 02STI with the VF35 and std topmount for a while...the TMIC was very very hot most of the time with any hard driving regardless of season. When competing, the bonnet was up everytime the car was parked and I would spray the cooler with water to get the temps down as i could not touch it! Ended up upgrading to a bigger TMIC for safety...problem solved.

my 2c.

Dan,

I know its not quite the same engine, but my VF35 spins quite happily around 20psi with an 05 STi TMIC - no probs. On competition days then yes I agree with Bruce, water spray comes on and bonnet comes up at rest.

Water/Meth injection would be another option to investigate for drastically lowering intake temps.

my 2 cents :p

Its the motec, get a link

*quickly jumps into flame retardant suit* :) :)