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What boost do you run?

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barks944

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Just wondering what boost pressure all you turbo owners out there are running? I guess a lot of you will be at stock or 1-1.2 bar. Typically 944 Turbo owners have not be able to play with boost due to DME restrictions. But anyway good to know what people are running reliably and what the general consensus on a maximum boost pressure for a stock engine is. Mines a 1986 with forged rod running at 1BAR boost at the moment. Intend to go up to 1.4, but maybe higher.

Tom
 
Stock 0.8 bar but looking 2 change that. Need 2 work out why my new dump valve preventing full boost 1st
 
ORIGINAL: T3rra

Stock 0.8 bar but looking 2 change that. Need 2 work out why my new dump valve preventing full boost 1st
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Which one have you fitted? Did you check that the vacuum line to the top port is connected to manifold pressure and not pinched or blocked as otherwise the top port is always at 1BAR so as soon as you generate any kind of boost pressure the dump valve will open.
 
Mine runs at 1.3 bar perfectly happily along side all the various mods of course. I would say she is reasonably swift ! Am hoping to finalise the engine mods soon with an improved intercooler and then that will be that (probably !)
 
I am running a low boost setup with plenty of headroom: 1.05 bar.

Tom, what turbo are you running, and what intercooler and exhaust? I am far from expert in these matters but suspect that if those three items are all standard, attempting to boost to 1.4 bar might generate more waste heat and pumping losses than actual power, along with getting you an old-school turbo-diesel style power curve. You have freed up the inlet tract with your MAF but above around 1.2 bar I reckon you will see significant restrictions leading to diminishing returns from the rest of the system. High manifold pressure does not necessarily flow through to power output, especially if it makes the charge hotter.
 
Excellent! Have you ever measure the pressure drop over the stock intercooler? I had the end tank on mine modified but I can't say I ever did any proper research. I am measuring the intake air temperature right in the intake manifold now so I can see how the charger is heating up the intake air. Will be logging it as I up the boost pressure so quite interested to see how good a job the intercooler does of keeping the charge temps low. Just blasting around on the road at 1BAR only seems to knock it up a couple of degrees if that.
 
ORIGINAL: Lowtimer

I am running a low boost setup with plenty of headroom: 1.05 bar.

Tom, what turbo are you running, and what intercooler and exhaust? I am far from expert in these matters but suspect that if those three items are all standard, attempting to boost to 1.4 bar might generate more waste heat and pumping losses than actual power, along with getting you an old-school turbo-diesel style power curve. You have freed up the inlet tract with your MAF but above around 1.2 bar I reckon you will see significant restrictions leading to diminishing returns from the rest of the system. High manifold pressure does not necessarily flow through to power output, especially if it makes the charge hotter.
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Agreed, it's only a K26/6 based turbo so it has a small hot housing. Its a standard bore exhaust to 2.5"? I'm booked in on the dyno with Bob Watson engineering on Thursday so it will be interesting to see how it copes with a freed up inlet but standard exhaust and small turbine. I will be logging the intake charge temperatures so I will keep a tab on that one. Should also have my EGT kit installed so I can monitor that too which I think will be interesting.
 
ORIGINAL: Lowtimer
Tom, what turbo are you running, and what intercooler and exhaust? I am far from expert in these matters but suspect that if those three items are all standard, attempting to boost to 1.4 bar might generate more waste heat and pumping losses than actual power, along with getting you an old-school turbo-diesel style power curve. You have freed up the inlet tract with your MAF but above around 1.2 bar I reckon you will see significant restrictions leading to diminishing returns from the rest of the system. High manifold pressure does not necessarily flow through to power output, especially if it makes the charge hotter.
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Seconded.
The standard intercooler is efficient at the costly price of being a significant flow restriction. Increasing air flow and pressure going through it will get it heat soaked, though I think it should still do ok with a KKK turbine coupled with a not-too-large compressor.
It's not easy to get both a relatively constant intake air temperature and a flow-permissive intercooler that does not soak heat from the compressor "too quickly".
 
ORIGINAL: Suffolk944
Mine runs at 1.3 bar perfectly happily along side all the various mods of course. I would say she is reasonably swift ! Am hoping to finalise the engine mods soon with an improved intercooler and then that will be that (probably !)
Click to expand...

If you haven't already I would suggest increasing exhaust size past the turbine, when fitting an improved intercooler. If the compressor can be made to flow more air thanks to a less restrictive intercooler then the turbine should be given more room along to propel the compressor accordingly.
 
To reply the original question, I am running 1.2 bar of boost. With the previous engine featuring (choco)late rods, the previous owner used to run 1.4 bar without issues on a engine with 100% of the standard mechanical components, air box and all.
 
Cheers Thom, totally agree with all the boost != power comments. I hope though with this management system including monitoring of AFR, EGT, IAT, knock and MAP I will get some good insight into how the system is performing as we climb up the boost levels. I can also setup compensations for fuel and ignition for IAT, CT and EGT on 3D maps against load so there are many means of building in protection and compensations to deal with these issues in terms of risk to the engine (I hope :D).

I suspect that exhaust restriction would be evident in EGT's? Any thoughts?
 
I think you should spot more difference in EGT (as measured in the cross pipe) by varying ignition timing than by increasing exhaust size, and it's probably going to be even easier to observe on an engine using all standard components, as it is necessarily going to feel more "restricted" overall and won't be as efficient, as a "closed-loop pump" (because this what a turbocharged engine is), as a well-derestricted engine such as mine.

Using compensation tables can be convenient, but this should be done after pretty much all restrictions have been removed, or at least balanced against each other, otherwise you may waste time chasing your tail by using more tables than necessary.
 
I am envious of all this knowledge guys. I take my hat off! I am running 1.2 bar safely (I hope!) on Promax L2 set up with the mods listed below.

Stuart
 
A standard intercooler will limit output to 320/375. According the Jon Mitchell, an intercooler with modified end tanks will solve this.
 
My red turbo road car runs to 1.5 bar max boost, with Big LR Turbo, Free flow full exhaust,Injectors,Fuel pump,P and P head, EBC,MAP,Stage 3 intercooler, Custom intake,LR inlet manifold..
Driven it long distances in summer heat to Spa and Ring.Doing a track day in her tommorow.So far so good.
But on my Ex turbo S race car that was flat out for 40 mins plus a couple of hour races we went for a conservative 1.1 bar boost.EBC,Injectors,slightly modded intercooler.Kept standard airbox with a K and N.We also installed a ram air system with a huge front fed scoop feeding the airbox.Tried it on SONOCO turbo race fuel during a summer race to keep temps down,memories[:D]
Promax did great tuning on both.
 
Thanks guys keep it coming, so the highest we have is MarkK at 1.5Bar. Any high bidders?

I went out and stuck a few more degrees advance onto the ignition map, creeping up towards the factory settings. It's nice to feel the difference in the car, its got a nice note and edge to it when the advance is right. At the moment its very strong until about 300mBar boost but then I have curbed the advance a bit while it runs in so it kind of droops out as the boost comes on and the revs climb.

Writing some code for closed loop wideband AFR and a knock driven ignition trim. I have found a nice way to do this without any additional knock sensing kit installed in the car. Sweeeet :D.
 
Thanks Tom 4 your help today.


Sounds good. Be intersting 2 see it fully exploited. Look follward 2 the dyno results

Be nice 2 know what rmp full boost is reached as well guys
 
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