Max safe boost?

[psilosin]

Boost controller showed up in the mail today. Its sexy anodized purple like Prince!!!

My stock boost is showing up as 12psi on my gauge which is higher than I was expecting so I am thinking I will take it easy on any extra boosting or might just stick it in teh Surf instead. Seen a few posts across the interwebs (UK and Australia forums) that seems to point to 15psi being about the upper limit for safe long term mod free boosting on the L400. Is that the general concensus around here as well? Is there a documented fueling cutoff protection psi point on the boost ramp pin?...I couldn't find any info on that for the L400. On my old Surf with the mech boost compensator like the L400 has this was ultra tweakable and fun to mess with.

I rememeber posts on the L300 that it has some kind of secondary over boost protection valve seperate from the wastegate that you have to block shut if upping the boost. I haven't noticed anything like this along the intake path of the L400 so I am assuming it does not have this.

If 15psi is the limit I'm thinking of shooting for 14psi at most for starters. Maybe after a bigger exhaust down the road and some tweaking to the boost ramp I'll go for more (as long as my wife doesn't find out).

[FalcoColumbarius]

According to my mate, the ex-military turbo-tech, the optimum turbo boost is 8-9 PSI. The faster it spins after that, the less air is collected. "If you want 16 PSI boost... get a twin turbo (2x8)".

Falco.

[fexlboi]

According to my mate, the ex-military turbo-tech, the optimum turbo boost is 8-9 PSI. The faster it spins after that, the less air is collected.

Might be true, but you still get a way better performance (Delica is pulling harder) with a boost over 10psi.
I wouldn't go too often over 15psi, unless you don't care that much about longevity of your engine.

[psilosin]

lol Falco. Excellent example of misinformation.

[FalcoColumbarius]

How so?

Mine runs just under 9 PSI and I have yet to find an L300 that can pull away from me, including ones with inter-coolers. I would think the military knows something about turbochargers and I have no reason to doubt my friend. Besides, why do you think Mitsubishi tunes them thus in the first place?

Take air screws on aeroplanes, such as high performance single engine machines. Even on variable pitch screws, which readjust the screw pitch based on velocity & altitude (air pressure) ~ there comes a point when the pitch is so steep that it works against thrust by creating more drag and the reason it is variable in the first place is because the initial pitch is no longer optimal as the screw turns faster.

Perhaps a variable pitch turbocharger.

Falco.

[Fishtank]

Besides, why do you think Mitsubishi tunes them thus in the first place?

I have yet to see a vehicle maker tune a stock vehicle to it's maximum potential, especially a van like the Delica. Most likely they set the pressure for longevity.

Take air screws on aeroplanes, such as high performance single engine machines. Even on variable pitch screws, which readjust the screw pitch based on velocity & altitude (air pressure) ~ there comes a point when the pitch is so steep that it works against thrust by creating more drag and the reason it is variable in the first place is because the initial pitch is no longer optimal as the screw turns faster.

Perhaps a variable pitch turbocharger.

Falco.

Now you're involving variable pitch and large altitude changes which changes everything. These turbos are all operating between sea level and 5000' at ISA temperatures and at a fixed pitch, turbos have very little to do with variable pitch propellors on airplanes. If you want to make a reference to aviation, you should reference to the compressor section on a turbine engine. Compressors and the turbos operate on the exact same principle which means neither one looses efficiency with an increase in speed, quite the opposite.

[deli1733]

My van turbo max's out at 13 or 14 psi, and I have a noticeable increase in power.

[psilosin]

Falco. I do appreciate the comments but please accept that I am not looking for 3rd hand accounts on different turbos from different vehicles or 3rd party opinions on turbocharger theory 1 style . That isn't what the question was and that just clutters this thread. I have been messing with boost levels, boost ramps and fueling for some time and know the subject quite well. Since I am new to the L400 I was inquiring what experimenting people here may have already done for tips and pitfalls. I have already gleaned much info from the AU and UK sites but was looking for some accounts from the hometown crowd for fun and commradery. Also it is as someone commented in a recent thread on L400 speaker sizes...it seems that every post gives different specifications so the more posts the merrier in the law of averages! lol.

There is no magic psi number of 8-9 for all turbos. Every turbo has an optimum of course after which the heat generated becomes a detriment but it is not the same on every turbo. A number of newer Tdi diesels run from the factory in the 20-30psi range and they are not using 4 turbos to do so. Racing car applications have turbos set well above that. Using your own argument Mitisuibishi factory set my L400 turbo pressure to 12psi...why do you think Mitsubishi tunes them thus?

By all accounts running 15psi is not a big stretch at all for this turbo and is the least of my concerns/interests in the turbo-engine-compensator-fueling-exhaust-egt-oomph-fuel ecconomy equation.

I'm looking for more comments on things like already mentioned in the op like if the factory L400 has an overboost fuel cutoff setpoint to contend with on the boost ramp or if anyone has opened up the boost compensator to see if the factory pin in there is cut with mutiple selectible boost ramps etc etc....the fun stuff that is done on a saturday afternoon with a wrench in one hand and a beer in the other!

[Fishtank]

psilosin, if I bring my van over and put a beer in one of your hands... will that put a wrench in your other hand?

[psilosin]

lol I think it would.

[FalcoColumbarius]

Psilosin, no worries, mate ~ I'm sorry you feel I am cluttering your thread, I was just sharing my experience and a little bit of that fun and camaraderie you speak of. Do which you please... smiles.

Fishtank, I would think that longevity is a fundamental part of the performance of a turbo. As far as variable pitch screws are concerned: I wasn't comparing a VP screw with an impeller, per se, I was using it as a model to demonstrate optimum collection at any given pitch. It was the first thing to come to mind. I am quite aware that a Delica diesel driving up the cut doing three grand and a variable pitch air screw on the end of a 27 litre V12, cruising at 250 knots at 30,000 feet are not the same ~ but thanks for setting the record straight, anyway.

There is information on this in the 4M40 shop manual on page 11A-9-4 in L400 Delica Downloads if that helps...

Falco.

[psilosin]

Thanks Falco. 11A-9-4 gives a maximum psi that the turbo wastegate can withstand before it takes some damage...16.6psi for teh L400. Not applicable in my application but this number is good to know if you are upping your boost by shimming the wastegate.

Shimming the wastegate is the simpest and cheapest (<$1.00 for some washers) way to up boost (*). Usually just involves removing the actuator, then adding a couple washers to the bolts and bolting it back on. Shimming the wastegate actuator effectively puts more tension on it thus a higher psi acting against it is needed to open the wastegate. This method can cause damage if overdone as the diaphram inside the wastegate can be damaged from excessive psi.

The alternative, and better way to increase boost is with a boost controller (*). The boost controllers job is essentially to fool the wastegate into seeing a lower psi than the turbo is actually putting out. In a simple mechanical boost controller this can be done with a bleed valve or a gate. Bleed valves bleed some of the boost pressure off before it reaches the wastegate so if the wastegate sees a lower than actual psi letting the rest of the system run at a higher than normal psi. A gate type usually uses a ball & spring type setup to apply a counter force to the boost heading towards the wastegate pretty much with the same end result. The different types are said to have pros and cons but for the low psi application of the Delica either should be fine. The gate type may give you a slightly faster spool up as they are supposed to prevent wastegate creep so you miiiight notice full boost at a lower rpm than normal but it would likely be minimal.

There are also electronic boost controllers that can get quite complex but they are much more expensive and totally overkill for a Delica imo.

* Don't do any boost manipulations without a boost gauge installed.

[jessef]

14 psi was my max/safe sweet spot on the L400's

Also make sure you have a good calibrated gauge. Mine right now reads approx 2 psi more than was is in reality after trying three separate gauges. Just a small point

[pajerry]

From reading up on the UK and AUS forums the general consensus is max 15psi max if you wanna keep your truck a while..

How many much shimming of the wastegate would you consider too much? I have it shimmed about 4mm from 2mm as of todays maintenance. The wastegate was quite tight, but it seemed to have more play, I was more concerned about the bolts getting too short but it all looked good. Drives much nicer as the boost comes on much quicker. I also installed a K&N filter for city and hwy and it really likes all the extra air.

I have yet to put it under real load but it seems to get to 13-14 easily enough in traffic Im sure it will be 14-15 strong under load. It also seems like its running out of fuel too quickly. We'll see over the next bit.

Im also looking into putting in a free flow exhaust and cutting out some bits for better flow.

Anybody know if plumbing up a new 3" from the top down is worth the money? Its either that or propane injection

[psilosin]

Im also looking into putting in a free flow exhaust and cutting out some bits for better flow.

Anybody know if plumbing up a new 3" from the top down is worth the money? Its either that or propane injection

I would definately do the exhaust before PI since the exhaust will give you benefit with many mods you do to the engine/fueling. It is the next thing on my mod list, before I start playing with the fuel delivery.

Not sure what the sizing concensus is for teh L400 but I would think that 2.5" should be big enough...though a 3" dump pipe would be great if it can fit.