Twin HX35's using the twin scroll or not?

[RedPhoenix]

As we all know, the engine bay is pretty tight in an SC400. I picked up 2 hx35's for a sick price. http://img.photobucket.com/albums/v499/redphoenix/Lexus SC400/Turbo/IMG_1208.jpg


I am starting to order my piping now and I was originally wanting to do the twin scroll idea, using cyl 1/3 and 2/4 together. Well, since there is little room on the driver side and I wanted to keep the AC compressor, what do you think about giving up on the idea of using the twin scroll and just have all 4 cyl on each bank dump into the turbos normally?

Do you think I would hit peak boost way too high in my RPM range? Or you think its still salvagable?

 

[JustenGT8]

Hmmm they look big either way? What's the turbine a/r. I can't recall the firirng order off the top of my head but you group the cyls (so on a 4 cyl it's 1&4 and 2&3 together). It would take a lot of pipework and room to manage that for twins?

If not run as a proper twin scroll then yes, it will hurt spool...by 500rpm at least. There's a flap valve system out there you could try but a bit pricey...or scrounge a couple off a pair of Series IV RX7's....that would help but will be tricky to fabricate.

My advice, sell turbos and save yourself the pain and anguish of it not working. looks cheap now, but will just cost you more when it doesn't work well.

OR source small a/r single entry turbine housing for those turbos? I have no idea how easy they are to find though?

 

[XR8tt]

Whats the turbine wheel size and A.R ???
I think your worrying too much about exhaust system...
KISS usually works better and far less complicated..
Plenty of quick turbo conversions with basic log style headers make good power..
So a half decent 4 into 1 each side would work very well.. Even if you fab collector a few inches away from turbine.. The cylinder pulses are still there...
Those turbo's seem to have large housings with moderate sized wheels so external appearances are hard to tell...

 

[dean]

you can see the pulse separator in the exhaust hosing it looks pretty massive in the hot-side

 

[xenith]

mate one of those turbos would do the job . notice that the nut on the compressor wheel is only a single hex these turbos had a habit of coming off when fitted to petrol motors and needed to be replaced as for the split pulse thing it is not a huge thing yes you will lose some spool rpm have built them both ways and made good power with good response

 

[ruishy1]

twin hx35's will be a bit laggy, you wont see boost till about 3500 even using the twin scroll

 

[XR8tt]

http://www.holset.co.uk/mainsite/files/2_1_1_3-Holset%20HX35.php

One would spool well.. These numbers are for diesel engines...
Which makes them more efficient at higher boost levels...

 

[eurokevin]

They should be .63AR.

I figured out how to make it twin scroll with some work. However, 3500rpms to start seeing boost? I know its a guess, but 3000rpms would be where I would like it.

How can these small 2L engines take a HX35 on so easily (see DSM) but a 4L would not do both?

Justen how big were your turbo's, when did you see boost?


My future plans are a 2uz/1uz hybrid to give a 4.5L displacement, but who knows when that will happen...

 

[RedPhoenix]

They should be .63AR.

I figured out how to make it twin scroll with some work. However, 3500rpms to start seeing boost? I know its a guess, but 3000rpms would be where I would like it.

How can these small 2L engines take a HX35 on so easily (see DSM) but a 4L would not do both?

Justen how big were your turbo's, when did you see boost?


My future plans are a 2uz/1uz hybrid to give a 4.5L displacement, but who knows when that will happen...

And I posted this... whoops

 

[XR8tt]

Twin scroll has nothing to do with manifolds.. Its the divider in the turbine housing..The theory of split pulse is for big turbo's on small engines to get them to spool.. There's not an issue on these motors...On this size turbo at least..
Sheesh they spool a T88 with ease..
If this turbo was off a Cummins diesel?? It would be a larger housing than .63...
More like 1.23 etc..
Ideally if its T04 sized between .84 and .96 1.06 on a 4.0 .. But as said the turbine wheel size etc has just as much to with spool than A.R...

 

[RedPhoenix]

Okay I found better info (holset hides some info) but they are 0.89 A/R not the 0.63, my bad.

Im still learning about A/R vs size vs the engine capacity, etc.

I also thought to USE the twin scroll you need to separate the engine pulses? which has everything to do with the manifolds..?

 

[RedPhoenix]

Also the BEP housing is single entry but makes it a .63 AR! talk about fast spool then.... Those are $170 each, which isnt bad.

 

[RedPhoenix]

and more bad information, its 0.55 AR, probably. I read both, but more 0.55 AR on the BEP housing.

 

[XR8tt]

Yes .63 would be great with twins...As a single .63 would have too much exhaust back pressure ...

 

[XR8tt]

Going by this turbo calculator..
If turbo is the same??
At 12Lb and expected 550 h.p the map is in its sweet spot...
http://www.squirrelpf.com/site/?page_id=7/

With HX35..
http://www.squirrelpf.com/turbocalc...=623&airflow6=766&airflow7=865&product_id=113

With twins...
http://www.squirrelpf.com/turbocalc...=405&airflow6=435&airflow7=444&product_id=113
It doesn't make too much difference if you fab a collector or have pipes entering straight into turbine..
I find better having a collector for compactness so 4 into turbine works better.. Yes with 2 cylinders to each tang...
Headers here for single..
http://www.lextreme.com/forums/showthread.php?t=11055&page=2

 

[RedPhoenix]

So twin HX35's with the BEP housings would be perfect. Thanks for the help man, I really appreciate it!

 

[XR8tt]

So twin HX35's with the BEP housings would be perfect. Thanks for the help man, I really appreciate it!

Yea just make sure you have what is spec ed above...
They made turbo's for each application.. So they varied from each application..