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Engine Specific Info and Questions => IDI Engine => Topic started by: carrizog60 on October 12, 2006, 08:31:44 am
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as topic says?
i have friend that aren t running stock boost and dont have boost controlers...
any differences in using one? :idea:
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If your stock,you don't need one.
Once you start turning up the fuel,and blocking off or adjusting wastegates and BOV's,then you could possibly overboost,and do some damage.
You only need enough boost to keep the engine well fed,and EGT's down.Anything more is a waste,and could possibly do damage.This is where you use a boost controller,or some method to limit max boost.
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so is just for sfe?
no performance advantage?
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Too much boost is a waste.....there is no additional performance gain,unless you add more fuel to go with it.
At higher boost levels,you also start to lose efficiency,unless you step up to a bigger turbo.
Keeping the boost down,to just what you need will great extend the life of the engine,turbo,etc.
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i dont use a boost controller, the wastegate is always closed.
the boost dont go to high, i can increase with putting more diesel in to the engine. i drive 18psi now.
Greetz, Benjamin (sorry for my bad english)
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^^^thats my question...
why to use a boost controller when you can simply close the wastegate and control it with fuel?
better response?any gain beside safety?
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While you can control it with fuel.....why ?
If your happy with the power level,and boost levels aren't alarmingly high,then yes,you can run without one.
If the boost levels are too high,with out the right stuff,you will lift the head off the block,and pop the headgasket.At this level,you need to control the max boost,and maybe switch to a more efficient turbo.It allows you to keep your fueling to make the power,yet not damage stuff.
What kinds of mods have been done ? What boost levels are you seeing ?
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Are you sure?
More boost doesn't up cylinder pressures (more than the boost pressure, insignificant) unless equivalent fuel is added. Yes the compressor efficiency may drop off and outlet temps go up a bit when overboosting, but thats what intercoolers are for.
Just more air (boost) just ensures all the fuel is burnt?
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More boost doesn't up cylinder pressures (more than the boost pressure, insignificant)
Oh, but it does. The boost pressure at the start of compression is multiplied by the compression ratio. At atmospheric pressure (zero boost, 14.7 psia) and 23:1 compression ratio, end of compression pressure will be 323 psi. It will actually be higher due to the heating from compression but for the purposes of this argument we'll leave that part out. The same 23:1 compression engine will have an end-of-compression pressure of 668 psi @ 15psi boost. At 25psi that figure rises to 898 psi and at 30 psi it hits 1013 psi.
These are rough figures, volumetric efficiency and other losses/gains are not taken into account , but you get the idea.
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QuickTD beat me to it,I don't think I could describe it much better than that.
While I'm no fancy scientist,who can figure out all the math and stuff,I have blown my fair share of head gaskets due to overboosting.I learned the hard way.Keep the boost down to only what you need to keep EGT's in check.That would probably explain why most turbos use a wastegate,it's there for a reason.
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but will 15 psi kill the engine running a stock 1.6l?
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These are rough figures, volumetric efficiency and other losses/gains are not taken into account , but you get the idea.
I do indeed, feel like deleting my post it's so stupid, as I could probably do that calculation myself at a push :oops:
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the engine is all stock now.
it is a 1.6D rebuilted engine so i cant go crazy...
it has 1.6 euro gtd injectors pump.also kkk24 turbo.
it has a bmw intercooler (60x23x5cm) but the pipes still missing.
i am seeing 0.6 bar and the engine doesent smoke but it start to heat after a short moment of high way boosting...
i will try to see how the i.c helps on that and maybe change the thermostat with a lower one as the temperature always sits in the midle mark.
as soon boosts kiks in it will start to heat and i have to ligt gas to prevent over heating... :?
no oil/water consumed...
i removed front lip, some says thats the reason as the termo may be getting fresh air from the front and doesent open at the right temp...
cars still pulls fine(180km/h easy)
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Oh, but it does. The boost pressure at the start of compression is multiplied by the compression ratio.
What about peak pressure during combustion? Wouldn't that be the limiting factor because it's that maximum pressure at tdc plus the increase in heat from combustion? For instance, on a NA, when the piston is at TDC at ~325psi, won't the pressure when the fuel is injected and combusts be much higher than that? In other words, isn't there some maximum safe level of boost w/o increasing fueling that can be achieved, because during combustion the peak pressure is much higher?
Or for that matter, wouldn't that be more of a problem with timing advanced, because the cylinder has to move up a bit before it can move down, so the peak pressure is higher compared to retarded timing, when the fuel combusting can push the cylinder down faster, instead of building up pressure until the cylinder passes tdc and then being able to relieve it by pushing it down when the timing is advanced?
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You asked why to use boost controller instead a simple wastegate adjustment..
Wastegate works in a way that it's opening slowly when boost is raised, and at the given max. boost, it's opened completly....
So, with wastegate adjustment, you cant't get the boost "instantly", as the wastegate regulates it slowly til it's max. value that is given...
That is what I was told when I asked the same question....
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What about peak pressure during combustion? Wouldn't that be the limiting factor because it's that maximum pressure at tdc plus the increase in heat from combustion? For instance, on a NA, when the piston is at TDC at ~325psi, won't the pressure when the fuel is injected and combusts be much higher than that?
Ideally, the pressure should not greatly exceed the end of compression pressure for remainder of the combustion cycle, that's what engineers shoot for. The holy grail is to hold the combustion pressure constant near to end of compression pressure for the entire power stroke. The reality is, of course, somewhat different. There is a sharp rise in pressure when the cylinder fires, this is aggravated by excessively advanced timing.
In other words, isn't there some maximum safe level of boost w/o increasing fueling that can be achieved, because during combustion the peak pressure is much higher?
Running boost just for the sake of it isn't really productive. The only reason to increase boost would be to burn more fuel. Stock boost is fine for stock fueling, increasing the boost without increasing the fueling will do little in the way of performance. It may be possible to run 50psi of boost (with a small enough turbine A/R) if the fueling isn't increased but it won't increase power one bit.
When you increase boost and fuel, naturally the combustion chamber pressures will rise, there is no avoiding that. Keeping it within reason (and preventing it from destroying engines) is what we're all trying to do.
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In terms of power I've heard there are minute differences, which are proportional to the supposed increase in efficiency, which I'm guessing is what someone running additional boost and just that would be concerned with. For instance, there's someone on the vwdieselparts forum claiming significant improvements to mpg can be had by retarding timing with a turbocharged vw diesel while running NA fueling. The downside is a big spike in NOx emissions, so CI combustion, especially in passenger cars, has to walk a fine line between power, economy, and emissions.
Otoh, large pickup truck manufacturers can put out diesels pickups that are 4 times bigger than diesel passenger cars, but can still get 15-20mpg, probably because they have NOx emissions regulations that allow roughly 4-5 times that of passenger cars. Supposedly, these can do even better with aftermarket chips... Which don't have the emissions limitations of the manufacturer, and can further lean out the engine.
Of course this is purely speculative since I haven't had time to tinker, but I'm hoping it's possible.
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i had a garrett from an 86 td
and it worked nicely with my shop air regulator for a boost controller
now the kkk im runnin from an 84 td,its wastegate doesnt really function the same
all the boost controller seems to control is how fast itll get to peak boost
to adjust peak boost ya gotta adjust the wastegate screw
i miss my garrett it was a way better turbo for these cars than the kkk junk :cry: and it gave more power too :cry:
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So was that T2 or a T3 Garrett - I notice the wastegate design and aneroid design is quite different on my T2 than the equivalent KKK
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I use a boost controller..on my K14. A glorified ball bearing and spring in a t fitting. I works well though. factory wastegate is around 12 psi. I mistakingly forgot to tighten the boost fittings when I added the boost controller and the k14 easily pinned my VDO 25 psi boost gauge. With the controller it maxes out @ 22 psi. So it's definitely a good way to run higher boost in order to burn the extra fuel, but still have some safety factor built in
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i dont know,,it was a stock garrett from an 86 td
not an eco either..........
there must be pics of the blown up one around here........
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I mistakingly forgot to tighten the boost fittings when I added the boost controller and the k14 easily pinned my VDO 25 psi boost gauge. With the controller it maxes out @ 22 psi.
I run the k14 too, are you saying you regularly hit 22 psi with no issues? I have always been afraid to go past 15psi for fear of wreaking havoc....
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lol turn in the screw all the way for some real fun,like 40 psi of fun :D
driven daily like this....... :D
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Will you build me an engine that will stand 40 psi and send it over to good old Blightie please mate...
Promise to send the packing crate back full of real English beer - by return - a fair deal? :roll:
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I created a topic that addresses max boost so that we arent thread jacking...
I don't want to be that guy..
here's the link..
http://vwdiesel.net/phpBB/viewtopic.php?p=41618#41618