69-chvl

iTrader: (11)

Thinking about another turbine housing for the street and another for race day. Current turbine housing is a t4 1.1, BW offers a .9 also. Is there enough difference in spool to justify the $180.00? Wondering if anybody ever tried this. Alot of the PT and TC turbos have smaller a/r's - wonder if this is why they come online faster than mine.

3 window

iTrader: (1)

Might end up being counter productive and become a choke point limit higher rpms. As I understand, it's a balancing act between wheel size and AR sizing.

forcd ind

iTrader: (7)

I was thinking the same thing, more a smaller turbine for the street

rotary1307cc

iTrader: (5)

I'd be looking why what you have isn't up to what you want. That turbo on that engine should make boost about anywhere, like a light switch

69-chvl

iTrader: (11)

Boost gauge zeros out at around 32-3400 whether rolling into the throttle, maybe 31-3200 flooring it from a stand still. On the 2 step it will light up much earlier, but I'm looking for better transient response.

This turbo spooled the same with an LS6 cam, 216/220 113lsa cam, then a 6.0 with the LS6 cam, then a PTC converter - no change at all in spool with all those changes.

Seems like some people have full boost by the time mine is starting. Any suggestions??

GMCtrk

iTrader: (23)

And that sounds like BS to me. I want them to provide data logs showing boost in relation to RPM.

My experience with the 475 was closer to yours.

Fat Jesus 808

iTrader: (5)

I had an S472 on a car, and tried a .90 and a 1.10. spool difference on the dyno was 200rpm, and the 1.10 made much more up top and rolled over less

stevieturbo

I've only tested a couple of cars with turbine housings. Just like Jesus says, it really did make very little difference to spool, if at all.
But smaller housings did affect performance by a noticeable amount, and not for any good.

I'd stick with the larger housing.

forcd ind

iTrader: (7)

My data logs show boost starting around 3500 RPM's, and with 3.25 rear gears puts you at a higher speed playing around on the street
I didn't get any paper work from FI, but I think mine was an S475 with a
92 turbine-if I can fit a 4L80E (now 400) in it, I will switch rear gears to 3.70's, still spool same RPM's, but cut the speed I am in boost earlier
If I stay with the 400, then I might look at a smaller housing also
I wont get the feel I had from Prochargers down low, but get closer, lol

69-chvl

iTrader: (11)

It pretty amazing that spool was only marginally better yet top end was drastically(?) affected. My application is unfortunately back roads with no real open stretches, so transient response is becoming more important than sustained WOT.

stevieturbo

Here's how it seemed to me, on the engines it was tried on.

Off boost...if there still isnt enough energy to help drive the turbo...all the smaller housing does is choke the engine's normal breathing.

So it wont help anywhere.

And likewise on boost, it simply restricts the engines breathing further at the top end

Transient response, off/on throttle there was no measurable change between the two housings even at over 30 psi boost ( 4cyl car )

Obviously not every application will be the same, but that was what I found testing with 2 different turbos, and 2 turbine housings on each on the same car.
I'll be trying another larger housing soon to see how that responds. Hopefully it'll be as good low down, and even better up top.

69-chvl

iTrader: (11)

Thanks Steve for the insight.

rotary1307cc

iTrader: (5)

Looking at rpm vs boost is for the most part pointless on an unlocked auto, especially a PTC 9.5

The converter stall speed moves directly with TQ input. And in the case of a 9.5 is is nice loose down low so the stall rises easily without much TQ rise

You can't make say 15lbs at 3500rpm on that converter, it is impossible, doesn't matter what turbo you put on or even if you spray it with nitrous. Because as the boost comes in and so does the TQ from it, rpm rises in direct relation to this

Let's say your motor makes 750ftlbs on 15lbs.... And sitting against the converter in stall it rides at 5000rpm...... You will never see rpm lower than that ever at that boost/TQ level

If you want more (more and useable) boost at a lower rpm aa you need a different converter, something more traditional like a normal companies 10"..... But then again you would be missing out on the whole point of the PTC 9.5


If you put a manual behind your combo you could make 15psi by 3200rpm.. Guaranteed


It is pointless to look at rpm vs boost on your combo though. Post a log rolling 2500 rpm and flat foot it in high gear

69-chvl

iTrader: (11)

I think I follow you rotary - its a "design" issue that wont lend itself to spooling no matter what. I'd like to try the WOT in high gear but she'll kick-down into 3rd. I changed out the "tight-ish" PTC for another 10" Trans Spec converter and it spools a little easier when flooring it and surprisingly its still a little tight up top! But better than before. Just not making power for the PTC but that's another story.

So really what is one to do to bring boost on sooner for a street ride - supercharger lol!!!!