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* :) :)

Why get a link when you can have a unichip?

.... why dont we all just use carbies?

I use my LINK to run my MOTEC which runs my quad webbers.

[QUOTE=POLARBEAR666]I use my LINK to run my MOTEC which runs my quad webbers.[/QUOTE]

Charlie Murphy! :D

:rolleyes: :D

"What did the Five Fingers say to the face...... SLAAAAAAAPPPP!!!!"

"Bitches, *clap* *clap*, Have sex with charlie murphy"

i run the VF35 to its physical limit, it holds 1.6/1.5 bar for as long as it can, then tapers down to 1.2bar at redline

even though i have a front mount, i rarely see intake temps exceed more then 5-7 degrees more then ambient even at full noise.

unfortunately your top mount is what is holding you back

Front Mount Inter-Cooler Mehn!!!.... Do It... Do It!!! :p

if you keep your vehicle speed constantly above 60km/h a topmount will suffice, although as soon as you slow down, or stop the topmount will heat soak, the only safe way around this is water/methanol injection to drop the intake temps.

personally if i had my time again, i wouldnt do a front mount, i'd keep the stock tube and fin core (or upgrade to the GD sti one) and run methanol injection.
you get the benifits of a short inlet track and very efficent cooling.

Well last night we did a bit of road tuning. Basically timmed the timing back a little bit and dropped boost to 1.2bar. We watched the logging all night and all seemed perfectly fine.

However, a hot summer's day will obviously be the biggest test :)

I'll have to look into this meth. injection...or a fmic...either way.

Thanks for the input people. :D

id boost stock internals to 20psi - spike only

[QUOTE=tuna]i run the VF35 to its physical limit, it holds 1.6/1.5 bar for as long as it can, then tapers down to 1.2bar at redline

even though i have a front mount, i rarely see intake temps exceed more then 5-7 degrees more then ambient even at full noise.

unfortunately your top mount is what is holding you back[/QUOTE]


i dont feel so bad now coz someone else runs 1.5 bar

[QUOTE=creepin]i dont feel so bad now coz someone else runs 1.5 bar[/QUOTE]

Only diff being properly done.

get a fmic over meth injection. keep it simple. the less things that can go wrong the better.

I have a vf35 and a "fresh" ej207 and my latest tune sees me boosting up to 2bar in fourth gear onwards. This is as per my boost gauge which shows like 28psi. I've driven it like this for a month or so (plenty of WOT pulls) and its been fine. No detonation as per my obd2 app. Should I assume my boost gauge is reading high or should I turn the boost down (don't really wanna do this[emoji3])

It's reading from this hose.
Oh and I was told by the tuner its set to 24psi

2 bar is a lot. Even for a 207. Mine hits 21 pound ~ 1.5 bar and tapers off to around 16 psi. I would be getting a second opinion.

A boost gauge mechanical or electrical is usually pretty accurate.

using the Perth-WRX mobile app

[QUOTE=Brett Allan;825316]2 bar is a lot. Even for a 207. Mine hits 21 pound ~ 1.5 bar and tapers off to around 16 psi. I would be getting a second opinion.

A boost gauge mechanical or electrical is usually pretty accurate.

using the Perth-WRX mobile app[/QUOTE]

Ask Sean from ASG how much boost his 500hp gc8 (stock 207 bottom end) was running.

[QUOTE=V3 RA;825317]Ask Sean from ASG how much boost his 500hp gc8 (stock 207 bottom end) was running.[/QUOTE]

From memory he had 30psi in there but good tip I will ask him👍

[QUOTE=Brett Allan;825316]2 bar is a lot. Even for a 207. Mine hits 21 pound ~ 1.5 bar and tapers off to around 16 psi. I would be getting a second opinion.

A boost gauge mechanical or electrical is usually pretty accurate.

using the Perth-WRX mobile app[/QUOTE]

Seems most people don't tend to stray above about 1.4/1.5bar on the 207, however theres the odd person running up to 2bar seemingly without issue. I found it very interesting when my tuner said that the much higher boost is safe so long as your afr and timing is safe as well, which I believe it is. I will keep asking around though.

[QUOTE=V3 RA;825317]Ask Sean from ASG how much boost his 500hp gc8 (stock 207 bottom end) was running.[/QUOTE]

I thought it had 14mm head studs?

[QUOTE=dnbosiris;825179] Should I assume my boost gauge is reading high or should I turn the boost down (don't really wanna do this[emoji3])

Oh and I was told by the tuner its set to 24psi[/QUOTE]

What you should really assume is the fact that your tuner's software isn't configured correctly and isn't reading your engine parameters correctly...
...and also sees knock on engines that are running perfectly.

[QUOTE=RJ999;825331]What you should really assume is the fact that your tuner's software isn't configured correctly and isn't reading your engine parameters correctly...
...and also sees knock on engines that are running perfectly.[/QUOTE]

The assumption here is that the tuners software is configured correctly, I've got no reason to believe that's not the case.

[QUOTE=dnbosiris;825333]The assumption here is that the tuners software is configured correctly, I've got no reason to believe that's not the case.[/QUOTE]

reading 24 when pushing 28 psi is a perfect reason.

Ah which model JDM 207 did you buy? I hope for your sake its a v7 with 2 bar going into it

using the Perth-WRX mobile app

It's a my03 with hypereutectic pistons

This is literally going to end bad. More boost=more heat. Something you dont want with hyper pistons.

Tick tock till hole in the block [URL=http://s1137.photobucket.com/user/Gtfozza/media/Mobile%20Uploads/received_985147844843249_zpsuv8ndudt.jpeg.html][IMG]http://i1137.photobucket.com/albums/n503/Gtfozza/Mobile%20Uploads/received_985147844843249_zpsuv8ndudt.jpeg[/IMG][/URL]

using the Perth-WRX mobile app

[QUOTE=dnbosiris;825321]Seems most people don't tend to stray above about 1.4/1.5bar on the 207, however theres the odd person running up to 2bar seemingly without issue. I found it very interesting when my tuner said that the much higher boost is safe so long as your afr and timing is safe as well, which I believe it is. I will keep asking around though.[/QUOTE]

The main reason is that 2 bar for those on 98 means that a lot of timing needs to be pulled (which means lower efficieny & Torque) even on E85 winding in big boost won't net the gains a slightly larger (higher CFM) turbo would with less boost - mainly because the VF turbo is working outside it's efficiency range & adding exponentially more heat to the intake charge v additional boost.

Let's look at flow: A VF35 (420cfm @ 14.7psi) isn't flowing anything like the amount of air a bigger turbo does, ie a Td05-18G flows (585cfm@ 14.7psi).

The main point being the bigger turbo is running in it's proper efficiency range whilst providing more air volume at far lower outlet temps than the VF35 would to produce the same CFM at higher pressure ratio's - which means more timing & more power.

All of the Techy stuff aside, I ran 1.7 bar daily with a VF34 on 98 (and P100) in my 'entry level build' 207 since it was built - it made just over 300hp. Turbo outlet temps would peak at 106 degrees during long pull on boost..... No point in pushing more boost on those temps.

2bar of boost for only 268hp, am I missing something here?

Got a Dyno plot you could post up?

Here it is.
Previous tune @ 1.4bar is the dotted line underneath.