determining max boost

[jantheeven]

I know this is probably pretty basic stuff, but I just need to make sure that what I'm doing is okay. Forgive my ignorance... ;)
How can I determine the max boost pressure my engine can handle? The turbo's specs say max boost is 28 psi, but maybe that's not very wise, is it? How do I know my engine can handle a certain boost?? (check my profile for car's specs)

[jantheeven]

...and I need a safer way of telling that than blowing my engine to smithereens and saying: okay that was too much boost :laugh:

(it's set at 23psi now)

[James George]

think most have felt 23psi is as far as you want to go before it all gets a bit hairy.
you have a lambda prob so just make sure fueling ok, then you have to listen for detonation, and if your measuring 23 psi at the manifold you want to go pretty careful. you either need a knock detector or get a pair of stethoscopes and have a listen

[minty83]

i personally wouldnt go much high than 23 psi on that spec maybe even turn it down a touch.. also depends on what you use the car for.. always correct the fueling when the boost has been changed..
Was it you that we meet at the last ring trip in october, car looks similar???

[DaveMayGTT]

I've not run that boost so im not sure but surely once you get to that boost you need to be worrying about the max boost your gearbox and clutch and things are gonna take aswell and not give out on you reguarly?

[jantheeven]

Was it you that we meet at the last ring trip in october, car looks similar???

Yeah that was me ;)

[jantheeven]

think most have felt 23psi is as far as you want to go before it all gets a bit hairy.
you have a lambda prob so just make sure fueling ok, then you have to listen for detonation, and if your measuring 23 psi at the manifold you want to go pretty careful. you either need a knock detector or get a pair of stethoscopes and have a listen

Yeah fuelling is spot on... I even had to enlarge my a/c jet from .9 to 1mm because it was running too rich @ WOT & full boost... so how does detonation or knocking sound anyway?? :crap:

[Mart]

Like a metallic rattle. If you can hear it, the damage has already been done.

As for boost levels, if on standard pistons, you're asking for trouble (read ringland collapse/failing) if you plan on running more than 1.5bar boost.

[dave j gtt]

[quote=Mart;20623]Like a metallic rattle. If you can hear it, the damage has already been done.

What damage is likley to orcur on the sound of that rattle. have heard it on many a car thats being bangered, and have heard it once b4 on my car when it was getting punished ? :crap: :confused: car still seems to go the same. was a couple of months ago.

[djinuk]

Like a metallic rattle. If you can hear it, the damage has already been done.

As for boost levels, if on standard pistons, you're asking for trouble (read ringland collapse/failing) if you plan on running more than 1.5bar boost.


didnt realize that at the first sign of detonation that damage has already been on, when setting the dizzy timing on a pug, the usual way of setting it , is to advance it and drive up a hill and see if you can hear detonation, ... if you can retard it until it stops, and if you cant advance it some more.

[Rob@Backyardracing]

didnt realize that at the first sign of detonation that damage has already been on, when setting the dizzy timing on a pug, the usual way of setting it , is to advance it and drive up a hill and see if you can hear detonation, ... if you can retard it until it stops, and if you cant advance it some more.

Or use a timing gun :rolleyes: The timing on the GT is fix unless you modifi the tdc pick up.

What do you think the noise is then? a warning? NO its you cylinder melting away. If peeps are trying to set det by ear with no steph then thats the most stupid thing ive heard.. ;)

[Adam L]

If you're getting det on a turbo car, I bet you're chipping the turbine blades away aswell. I've seen it so many times.

[fidos got a raider]

New poster! (less than 10 posts)

If the pistons are low compresion than their can run higher psi but you need steel liners other wise bang. Cause standard liners can only take 25psi

[5teve L]

Dunno about that Chris ;)
Accidently ran 2 bar through mine once :scared:

[Mart]

New poster! (less than 10 posts)

If the pistons are low compresion than their can run higher psi but you need steel liners other wise bang. Cause standard liners can only take 25psi

If the pistons aren't forged, they can still suffer with ringland failure at high boost levels. Standard liners are good for a fair bit more boost than that.

[fidos got a raider]

well i would,nt go other 25 pound of boost with standard liners

[rs250nut]

in my old five i have seen 32psi on a flat out run to top speed with standard pistons and liners.

[Trevhib]

in my old five i have seen 32psi on a flat out run to top speed with standard pistons and liners.

aye cause using the car once is all you ever need :laugh:

[Trevhib]

[quote=Mart;20623]Like a metallic rattle. If you can hear it, the damage has already been done. quote]

I think it's more accurate to say; 'if you can hear it, some damage has already been done.'

Now I await my dressing down :D

[Mart]

Now I await my dressing gown :D

Cooo eeee http://www.lancerregister.com//images/smilies/gay.gif

:D

[markey b]

well i would,nt go other 25 pound of boost with standard liners

mine runs 27 with dished std pistons, and std liners.. recently cracked a liner due to a leaking water pump, but never due to too much boost, and thats in 3 years of ownership

[Trevhib]

Now I await my dressing gown


Cooo eeee http://www.lancerregister.com//images/smilies/gay.gif

:D

Ahahaha, don't fiddle with my shizzle.

[Scoff]

mine runs 27 with dished std pistons, and std liners.. recently cracked a liner due to a leaking water pump, but never due to too much boost, and thats in 3 years of ownership

you won't have cracked a liner through over heating, more likely it detonated a lot for some other reason.

[jantheeven]

Okay guys... thanks a lot (again) for all the useful comments. I think I'd better play it safe and run no more than 1.5bar with my std pistons & liners. This project has been expensive enough as it is! ;)

[markey b]

you won't have cracked a liner through over heating, more likely it detonated a lot for some other reason.

did cyl one, on the turbo side, had a water leak for a while, pistons have no det whatsover either, or pitting of the head, liner etc.

it was gettin warm on the way up to the pod, was water pump bolts in the end that looked like apple cores and leaked the water out under pressure

[Scoff]

did cyl one, on the turbo side, had a water leak for a while, pistons have no det whatsover either, or pitting of the head, liner etc.

it was gettin warm on the way up to the pod, was water pump bolts in the end that looked like apple cores and leaked the water out under pressure

yeah, maybe that didn't help, but it will have been detonatating if the liner cracked. most times the liner will give way before the piston has chance to deteriorate. I've been able to use the same piston most of the time when I've swapped a liner, usually no marks atall as you say.

detonation needs to hapen for a while before pistons start to melt. they melt/expand/wipe because the layer of fuel that once lived on the piston and liner wall, which used to protect the materials from combustion heat, has just been disturbed by detonation. the piston, liner, rings are exposed to temperatures that are high enough to cause harm and/or melt stuff when this occurs. I think people think they melt because combustion was too hot, not so, it's usually cooler during detonation, because the piston etc are sinking the heat away - shown as a drop in EGT if it occurs long enough to see.

if the liner gave away early on then it was a lucky escape. better still would have been for the gasket to let go, but, those nasty blue uprated things people fit often dont.

[markey b]

fair play, learn something every day! lol

it just felt like i'd lost a cyl, got to the A45 bp before it started to white smoke, that prob didn't help either lol

1st liner prob i've had in 3 years, 4th or 5th time at the pod with it too, maybe it was just its time to go lol

[Scoff]

yeah, wierd how it hung on for a while, maybe the crack was quite faint to begin with.

[markey b]

possibly, its had a fair bit of abuse that engine :cool:

only ever change the bit i break, and it still manages to make good power every time lol