Racintweek

i read that when it was posted a little while back.

you wouldnt get simultaneous pulses either way you paired them (1+4 & 2+3 or 1+2 & 3+4). the pulses would be alternating between the 2 cyls paired, so why would that effect anything??

Racintweek

there is a lot of good info on holsets on some DSM forum. but there are no definative a/r numbers for any holset(along with KKK turbos) is there any way to really measure the wheel size and housing a/r??

Tom-Guy

Look at exhaust valve overlap. 1+4, 2+3 doesn't have any. I really do suggest you look for my writeup on pgmfi.org - hate to direct ppl off forum, and even then not provide a link, but it's hard to access my account there from a non-cleared IP address without the password trying to reset itself for security reasons. The joys of wardriving *sigh*

As for wheel sizes, they are published figures, and AR can be calculated. Permatex makes a curable latex you can fill the turbine with if you are that curious, then pull the mold out and it pops right back into shape. Easy to calc AR from there...

... sadly, I'm not that curious. Are you? :P

Racintweek

aaahhh, valve over lap makes sense. is the benefit in spool time worth the effort on a street car making under 300hp??
i wouldnt think so.

on holset's site it says the WH1C only came with a 12cm^2 housing, teh h1c varies based on original applicatio. the only way to tell on the H1c's is teh serial/model number.

gt350

I didn't think the wh1c came with a wastegate? pretty sure they didn't. what does the tag say on the compressor side? my hx35 flows 53lb/min of air. and i've read on a site that 7cm is close to a .48a/r, 9cm is close to a .63a/r, and 12cm is close to a .82a/r one thing you'll want to do before installing if your not going to make a paired manifold is to mill(or grind) out the divider to alittle below the wastegat hole and port out the wastegate hole then clean up the short side radius of the wastegate hole. if you don't your run a very big chance of creep. us turboford guys use these turbos quite frequently only for there intended purpose 25psi+ these turbo's loooove high pressure ratios.

Racintweek

on any holset turbo teh W indicates ionternal gate. the H1C is actually a litle bigger on teh turbine side compared to the WH1C.


so, what is this magical calculation to figure out a/r from cm^2 i think J davis's idea of filling the ex housing with latex is out the window.
i've heard the 12cm^2 housing was around .58 A/R

Racintweek

i just recieved the turbo


my god this thing is MASSIVE


its bigger than my ------- head, but the turbine wheel looks kinda small so spool shouldnt be too bad.

ThingyNess

There is no direct conversion between A/R and nozzle area in cm^2, because A/R is just a ratio which includes the nozzle area as one component.

A/R = Nozzle Area (A)
----------------------
Radius of turbine inlet scroll (R)

In my opinion, the nozzle area in cm^2 is much more important in determining spoolup than the A/R, and I wish all manufacturers used that spec. We're used to seeing A/R though, because that's what Garrett uses and they're the most common turbos out there. Mitsu and Holset both use the Nozzle Area when specing their turbos.

I like nozzle area much better because it gives you at least a rough way of comparing spool characteristics across turbo frame sizes. For example, a T25 with a 0.60 A/R turbine housing and a T3 with a 0.60 A/R housing will have wildly different spool characteristics, despite the same A/R. Reason being is that the R is smaller on the T25 than the T3, which makes the A (nozzle area) smaller as well, which speeds spoolup. Just as an example, the T25 could be 6cm^2/10cm = 0.60 where the T3 could be 9cm^2/15cm = 0.60. The T25 would build boost much quicker due to its smaller nozzle area, which is really what we're looking for.

As the guys here have said, that Holset with the 12cm^2 housing is pretty big, but that's typical of a turbo for a large diesel engine. On the plus side, the twin scroll inlet does help you a fair bit, provided you design your manifold properly. As has been said, you want to pair cylinders 1-4 and 2-3.

To give you an idea of spool time, a 14b from a DSM will have a 6cm^2 housing and an EVOIII 16g will have a 7cm^2 housing. However, on the EVO8, they went to a 9.8cm^2 and on the '05 a 10.5cm^2 housing without sacrificing much in the way of boost threshold (with the basic engine - same displacement at leaset) since the EVO8 turbo is a twin scroll design and the others aren't.

Anyway, if you want to calculate the A/R, just pull the turbine housing, pick a point inside the scroll (usually where it just starts its characteristic "snail" shape) and measure the area. Easiest way would be to mold a piece of modeling clay in there, then push it back out and measure it. If you have access to a set of telescoping gauges you could try to measure it that way and estimate the area. Then just measure the distance from the center of that area you measured to the middle of the shaft - this will be an estimate as well, but you'll at least be in the ballpark.

Divide the A you measured by the R you measured to get the A/R. Make sure to use the same units for both.

Racintweek

lots of good info, although it would be a small project in it self to stuff the turbine housing with clay/latex

how much will running a log mani hurt spool-up? and if it hurts that bad who can make me a manifold without killing my wallet??

Racintweek

i found something i can hack up to make a 4-2 split manifold



i have the mani that is on the right(except no EGR crap) the spacing on the outer sets of runners is almost perfect. i just need to cut the runners in the bottom of the pic to make the gap in the middle smaller, get a b-series flange. and then get an adapter for a t3,