924Board.org

[-nick]

This is all hypothetical of course...

If one were to look outside the KKK turbos, where to start?

All I know so far is that the split exhaust inlet housings add some efficiency for our little 4-bangers (when combined with a 4-2 manifold that keeps the split).

Where to go from here?

nick

[Lizard]

if going after market turbo for th 931,
I would create a custom exhaust manifold that would feed into a turbo (I would use a BB turbo w/ water cooling) that had a built in wastegate so that I could eliminate the factory double pipe and that way exhaust work would be easier, I would also isolate the turbo unit on its own coolent system and oil system (seperate elect pump w/ own resevior)

this will really increase the simplicity, the life, and will decrease the spool up times depending on turbo chosen.
_________________
3 928s,

[-nick]

Yep, I think that list is pretty obvious. Although, sticking with a plain old oil-cooled turbo simplifies matters greatly. I think life expectancy can be pretty reasonable with the proper care (synth oil and a turbo timer) without going to a water cooled body, or separate reservoirs (what a headache).

My biggest concern at the moment, is just sizing. Let's take a look at the k26 compressor map-



At the 70% efficiency mark, our old turbos can produce .5-.9 bar (boost) with about 9-16 lbs/min of incoming air.

The old Garrett T3 in "45" trim is doing the same at 74% efficiency. At 70% efficiency it can produce .9-sky's the limit boost given 9-16lbs/min of air.



Wow, pretty amazing difference?

I'm new to reading compressor maps, am I overlooking something? I had to convert the 1/(kg/sec) into lbs/min, maybe I missed something?

Well, in this case, it looks like the "50" trim would be the best selection for running 1 bar boost (the mark I'm looking at)-



Not to check into ball bearing options...

Any thoughts?

nick

[Raceboy]

If turbo change comes in, I would go for something much bigger, like K27, K28 (like me ) or GT30R. Since, if I'm not mistaken, you're going to throw the VW pistons in, your engine will have some good potential and why not give her a chance to perform really well?

Oh, and of course, hotside would be the same: just hybrid.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[-nick]

A little more digging...

I got a _very_ rough quoate of $4-500 for a custom 4 cylinder tube header from a shop that's been making headers for about 50 years. Interesting...

It looks like the Garrett "GT" turbos are those that use ball bearing centers- with greatly increased spool-up times. Although, they go for about double (or more) what a typical T3 goes for. Not sure I want that much insanity.

I'm envisioning some trouble with the turbine out - to exhaust, for an internal wastegate turbo. The flange would have to be a decent size to collect into the downpipe, and there isn't really too much room back there.

Fun stuff

nick

[-nick]

^^ You know the maps for a k28 or gt30 are waaay out range for our little 2 liter's? There simple isn't enough exhaust output to drive them anywhere near effeciency. Not sure about the k27, I haven't looked at the map.

Considering you can run 25psi and pull well over 300hp out of a gt25r, why in the world would you need the gt30? It would just introduce significantly more lag with no gains.

Speaking of, Garrett's GT25R looks like the huffer of choice. Though it is water jacketed which adds a little more plumbing into the mix.

nick

[Lizard]

I would personally say that the added plumbing is worth it.
_________________
3 928s,

[Raceboy]

nick: These maps are given included hotsides respectavely. But with hotside of original K26/6, lag wont be much of a problem. Only problem will be surging in low rpms and high loads, but after doing some mathematics, the K26 hotside and K28 compressor would work just fine on 2.0

Anyways, where did you get the map for K28? Could you send it to me or give a link? 'Cause there's a couple of variations of K28 available.....
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[-nick]

ah ok, didn't know you had already done the math. I know 951 guys get quite a bit of lag using the GT30 and figured it would be even worse with us. I forgot that there are a bizzillion combinations of housings & wheels.

I'll try to dig up the k28 map again. I came across while hunting around yesterday...

Do I gather that you can swap the k28 compressor side onto our stock k26's? Can you give me a better idea of the performance of such a beast? I'm looking for a primarily street running car; maybe you're going in a track direction?

nick

[Raceboy]

I'm going for a streetable drag-car Anyways, I'm aiming to the 2 Bar area, god knows when and if I suceed. It probably needs stand-alone EMS with this turbo.

I did some measurements. My K28 compressor wheel diameter is 83 mm compared to 931 ROW stock K26's 62mm. Quite an improvement.
BTW, the K29 compressor used on the Pikes Peak Audi Quattro measures 86,4mm! But tey used it app. 12 000 feet above sea level. I read it in some board, that this turbo would surge like hell at sea level. My K28 with K26/6 hot side would be just on the surge limit on low rpms.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[Racing]

Nick.
Greeting n all a that,long time no see aso.
That said...
This turbo thing doesn´t quite work as you think i believe...
Here;



Close friends running a K29 on a 16 valve 2.3 liter Volvo engine in an Opel streeter.Car is setup for streetracing.Period.
Maximum boost through those twin 40mm dellortos(who´ll suffice what it seems forever btw) is set to 2.5 bars.
Snail is a twin entry unit,and as a result they run dual wastegates as well.
Most of it as you can see is home brew.
Output?
No friggin idea,and these guys(who as you can gather)are talented enough to "be all in" as far as what the engine wants.
Puts out power from the basement up tho,and rev limit is 8 grand(at least thats what KG and Jonas told me)
Nother friend runs a similar huffer on his UR quattro with good results(inxs of 650 honest ones)
GT40s are becoming the standard for souped up Volvos and what have you around here.
Not that long ago one of the boyz dynoed inxs of 750 out of his "schwedishes panzar" engine-albeit also transfered into an Opel of early vintage.
Some are even running Holset HX40 up to 55 units with good results.

Nick.
It´s all in the ign and fuel maping.
Trust me.
A "trim 50L" will level out around the 360 mark-and that´s it.

You´re correct in that ball bearing units have shorter spool up time.
CAN be an advantage dependant on your application,but DO NOT take that to the bank.
However...
360 axials are a good thing if higher boost levels are foreseen(1,5 bar up),and an adequate blow off valve isn´t within the system.(which will render extreme rpm changes for the turbo and make the whole deal "float" within the unit putting tremendous forces on axial play)

[Racing]

Speaking of which....
One of the "hot" names on the turbo scene since a while back is the these days fabled Swedish engine builder "Dr Ernie"(Ernlund-last name)
Couple of other friend run a drag team by the name of DTE racing(they´re on the net if you´re up to it)
Ernie put together a twin huffed 482 chebby BB for the boyz.
Sporting two Holset HX55s on 0,9 bars and alcohol.
Guess what.
1982 horses and 2100Nm.
Dynoed and ready to go.
So..yeah well...