Sunday Driver, Stock LX9 and Boost Limit.

[Weatheralls Auto]

This will not be a DD, Mainly for Summer weekends and such.

Stock LX9 (approx 11 000 miles) what would the boost limit be?

I have been planning on 8psi, but starting to think I could bump it up some?

What do you think?

[robertisaar]

lets see: a 3BAR MAP will read ~29PSI.....

[Weatheralls Auto]

I mean how much Boost engine will take with out serious long term durability issues,
Stock, without a build up.
My engine has approx 11 000 miles, so its just broke it lol, just looking for opinions on boost level before shortening the longevity significantly.

[1988GTU]

7lbs is safe with tuning and intercooler. 2Bar map is plenty.

[IsaacHayes]

many are running 10 or more psi regularly on a 3400.

[Weatheralls Auto]

Ya, I see a wide spectrum of answers, guess I will have to start of low and build up.
However, would be nice to know limits before hand to properly plan everything.

[1988GTU]

There's no set limit. It's like asking what ONE cereal a kid likes. There's going to be multiple answers.

[Weatheralls Auto]

Yes, a variety of answers.
But there should be a general guideline even though it would also depend on the tune and the aggressiveness of the driver to some degree.

Years ago, 8 psi was a standard limit IIRC on stock engines, however, the engineering has change vastly since then.

For the better or worse? Bet there will also be a great variety of answers on that one as well lol.

[robertisaar]

engineering always gets better.

simplest way to go: get ready for a rebuild and bump up the PSI by 2 every time you drive it. when it blows back it off a notch or two

i'm planning on ~14psi on a 95 3100. not planning on it lasting forever, but it should take abuse for quite some time. i honestly would expect the trans to go first though.

[RedZMonte]

general consensus among my turbo buddies is 10PSI with proper fuel and tune on stock motors is a good point... after that you want to start looking at making things a little stronger.... but honestly there is no real answer to that question... i have seen stock motors that have been turboed run 15-20 psi and beat daily... again had a proper tune and fueling system.. did they break down occasionally yeah (head gaskets usually)... for sake of longevity i would start at 5psi and work your way up to a max of 10psi..

Im running 7psi on mine.. daily driven and beaten. no problems.

S

[Weatheralls Auto]

.... but honestly there is no real answer to that question...
S

Ya I am seeing that now.
The main thing for me is, being sure the Turbo I am getting will be compatible with what I am building.

Running 8psi with 1.502 pressure ratio
or
Running 14psi with 1.95 pressure ratio

With Torque @ HP meeting @ 5200rpm on both could mean two different Turbos would be needed.

Selecting a Turbo for 5 psi and bumping it up would not result in optomised Boost would it?

Or am I totally off on al this?

[robertisaar]

you're correct to a point: any one turbo has a best efficiency at one specific pressure ratio for any given engine. taking a turbo 3400 with a T70(example only!!!) and is making 300HP at 7psi, then just adjusting the wastegate to allow 14PSI, it may make 400HP, but there will be an efficiency loss, meaning more heat in the air charge.

http://www.squirrelpf.com/turbocalc/index.php?version=4&target_peak_power=300&pr_ref=14.696&engine_disp=3.1&engine_disp_factor=0&target_af=12&bfsc=0.428&max_ic_loss=1.5&rpm_redline=6000&rpm_peak_power=5200&rpm_max_boost=4000&rpm_min_boost=3000&vol_1=78&vol_2=80&vol_3=72&vol_4=65&vol_1=78&vol_2=80&vol_3=72&vol_4=65&intake_temp_1=90&intake_temp_2=120&intake_temp_3=135&intake_temp_4=140&turbo_n=1&map_sel0=56

click "Refresh Maps" and play with it a bit. you'll see that by increasing/decreasing the target HP, and therefore raising/lowering the pressure ratio, will push the plots on the compressor outside of what i like to think is the optimal range for this specific setup(should be easy enough to figure out what it is...)

EDITL: actually more PSI could be found with that setup without losing efficiency, possibly gaining more, but this is with stock, worn internals. i don't think it should be pushed any further.

[MidnightriderZ24]

t70 will be laggy. heres a 6psi video of my 3400 with ported heads and a t70, 2nd gear roll from 35ish.. http://www.youtube.com/watch?v=YEjsga93N8s

[IsaacHayes]

What car is this going into?