86 951 Driver

Apparently this is real popular around the DSM crowd. They say it gives the turbo quicker spool and a few more HP. Anyone done this to a KKK26?

JohnKoaWood

ported or trimmed?

Please expand as I know ths DSM crowd loves trimming the compressor wheels, but porting? What exactly are they porting?

Fabio421

A ported housing is supposed to help eliminate comp. surge but I don't see how it could improve spool times.

JDS968

I think you've got it mixed up. As far as I know, porting slows down spool time and reduces peak output a bit, in order to move the surge line to the left - that is, make able to achieve lower flow rates at a given RPM without surging.

I don't really see the point of porting the turbo as long as you have a diverter valve.

86 951 Driver

Not sure what they mean. Thats part of my post too. I keep reading about people selling these ported turbos for sale. I ask what it does and they say a few more HP and quicker spool up. I thought maybe we could port the inlet of the K26 a bit to get some more power maybe.

JohnKoaWood

I know what porting the compressor housing is and what it does, I have also heard of porting the turbine housing, but this only serves to reduce backpressure (improves spool time, but reduces the maximum turbine speed atainable...)

which is why I asked for more details.. IMHO porting the turbine housing on the K26-6 wont provide a real world benefit, as it is not backpressure limitted in my oppinion... it is size and terminal speed limited..

porting an oversized turbo may reduce spool time, but again, only if the limiting factor on the rubo is backpressure... I.E. a small turbine with a larger compressor wheel... which just isn't the case on our older turbos.. now if it were a DBB center section, -6 turbine section with a 27 or larger compressor wheel porting the turbine housing may yield some spool gains at the cost of turbine efficiency..

Lots to considder, especially when there are more modern turbos available to provide much better efficiency curves... but those come at a financial cost intollerable to many of the users of our little old cars (talking about turbos costing well above 1K each)..

JohnKoaWood

Porting the turbine housing yes (moves the surge line to the left).. porting the compressor housing makes the turbine more resistant to surge (moves the surge line up).. both have some affect on efficiency... at the end of the day both make the compressor map much more flat!

neither has much to do with the diverter valve...

HP claims on a ported turbo are much like HP claims of a chip set... they are bench racing numbers.. as the seat of the pants "feel" is different from the actuall demonstrated performance on a dyno...

pettybird

Stock 14B Mitsu turbos have internal wastegates and an appalling line-of-flow from the turbine wheel out. You hog the crap out of the outlet and cut back to the wastegate divider wall so it can breathe. If you try to push a stock one too hard it overworks the wastegate--the flow past it on the turbine side pushes it shut! A couple hours' worth with the Dremel and you'll have a Talon in the 12's. It's crazy easy to make power with one.

Since we don't have an internal wastegate it's not a problem.

JDS968

Does that apply to the 14B as well?

pettybird

fixed...got my 14B and my 4G63 backwards.

JDS968

Ah okay.

Hm.

Got any links with details on how to do that work? I think I've got more dremeling in my near future...

gt37vgt

porting or extrude honing housings is only worth doin if you have bigger wheels and realy cant fit bigger housings or don't want to as your cheating trying to look stock...
and anyone who would do a mod to "reduce surge" simply doesn't understand what surge is...

give me an example of surge on a road car

pettybird

your posts reference the compressor side...the 14B needs a ton more help on the turbine side.

here are a pair of links so you can see the brilliant mitsu design for yourself:

http://www.vfaq.com/mods/porting-turbo.html

http://www.vfaq.com/mods/porting-O2.html

you can see how they go together to make a real clusterF of the exhaust flow. Also, the wastegate BARELY opens, so boost creep is a major problem.

JFreeman

If your looking for a few cheap horses like i was, you can try just polishing the inside of the compressor housing. I did this on my K26-8 and it made a world of difference, especially through the upper rpm. If you look on the inside of your comp housing outlet, you will see a ridge that looks to be a stop for maybe a boost pipe that slides inside the housing instead of clamping on the outside like the 951, thats something i also sanded out. Just my 2 cents

gt37vgt

i think the thread was about the anti surge slot/groove/ports... i herd they can effectively fatten the map and it makes sense as they feed the secondary blades better . i still say surge is almost never on most thing perhaps ina an on/off throttle drive ...
i am all for polishing stuff you can get to as it cost nothing and probably does a little