Dudemaaanownsanrx7

iTrader: (23)

I have a masterpower t70 with a .96 undivided P-trim housing. My manifold is divided so I'm thinking of switching to a divided exhaust housing. I would like to get spool a little quicker while still flowing plenty on top. I'm currently running 20 psi and will probably go to 23-25 psi. I'm trying to decide between a 1.00 and a 1.15 divided. What kind of differences do you think I would have between the 2, and compared to the undivided .96 that's on there now? I definitely don't want more lag, I can live with what I have now, but If I could reduce it by 500 rpm that would be great. In 3rd I get 5 psi around 4k 10 psi around 4500 and 20 around 4800 something like that anyways. 1st gear will only make around 10 psi I think. So..... opinions?

Chaotic_FC

It depends on what kind of porting on your engine.
a bridge port will have stronger response with a 1.15, but i think a street or stock port would probably prefer the 1.00. It also depends on how high RPM of an engine you have. If you are looking to have your power climb straight to 9500rpm, then mabey the 1.15 is better.
If you are really looking for an optimal setup however, you need to use backpressure sensors to test it out until it is as close as you can get it.

Dudemaaanownsanrx7

iTrader: (23)

I have a large street port. I'm guessing both will have better peak flow then the .96, now whether the 1.15 will be laggier then what i have now is what i'm curious about. It is a larger housing but it's also divided which helps spool. I'm thinking going with the 1.00 is a safe bet as i should get a little better flow and less lag but i'm wondering with the higher boost if i'll be leaving a large amount of power on the table.

G's 3rd Gen

iTrader: (11)

I would go w/ a 1.0. a 1.15 is going to be more laggy than you want . G

ScorpionT

iTrader: (3)

I agree, 1.00 is the way to go.

arghx

iTrader: (3)

I just switched from a .96 undivided to a 1.00 divided but I still have to break the engine in

GoodfellaFD3S

iTrader: (213)

I agree with what's been said up above about the 1.0 hotside a/r.

What kind of portwork is on your engine? That is bigtime laggy.....on my 500R setup I am seeing 20 psi by about 3800 rpm in 3rd gear if I punch it at 3000.

Also, I am running a 4 inch full exhaust with ceramic coating and a heat blanket. May want to consider that as well to help spool.

classicauto

iTrader: (3)

Are you running a cast divided mani. or an SS?

I think the un-equal runners in the cast hold back a bit of potential, and if thats what you're running I'd stick with the 1.00......if its not, you might get away with the 1.15A/R but being a P-trim I'd think a larger exhaust might be needed to re-gain some lost spool from the larger housing.

A larger exhaust *should* help either size housing out though.

Dudemaaanownsanrx7

iTrader: (23)

I have a large street port. And ss divided manifold, The turbo is much larger then my old turbo which would spool to 15 psi by 3600. It was some kind of t61 combination. Although the old turbo also had a .82 exhaust housing. Neither turbos were ball bearing so its hard to compare to the 500r. I have been considering a larger exhaust, especially the downpipe. It's all 3" right now. Arghx let me know what difference you have between the 2 housings, and i'm guessing your manifold is divided too?

classicauto

iTrader: (3)

May not be much help, but in moving from a greddy collected mani, with GT3574, 0.84 A/R to a divided SS, divided 1.00 T04-R I kept the same (save for transient response) resposne as the much smaller turbo and housing on the open (mismatched to turbine housing) manifold.

This was done on the same engine, which was a basically unported stock S5 engine, and both were on 3" exhausts.

Turblown

iTrader: (12)

I recently built a car in where the only thing I changed was a 1.0 divided to a 1.15 and it made zero difference. Boost seemed to come on maybe a few hundred rpms faster, and peak boost was maybe 100rpms slower. That was a Gt35R P trim large SP 3.5 exhaust. I have done a 1.24 divided down to a .96 open volute on a divided manifold and that made a big difference on small streetport, probably 800rpms peak boost( 1 bar 57 trim To4E 3.5" exhaust). There are a lot of factors. However going from a .96 to 1.0 isn't going to add any " lag".

Dudemaaanownsanrx7

iTrader: (23)

Alright i'll keep an eye out for a 1.00 p trim housing.

Turblown

iTrader: (12)

Personally I would check your exhaust back-pressure first and that will give you a good indication of what a/r you need. Its really easy to do.

Dudemaaanownsanrx7

iTrader: (23)

Yeah I have been planning on checking that anyways. I was going to check it after the turbo, just to see how much my exhaust was restricting everything, but I imagine you're suggesting I check it before the turbo which is going to be more difficult to get fittings in that area. I'm really leaning towards the 1.00 cause with the divided housing it should help spool, and it should also flow a little better on top then the .96, really the top end feels fine but the lag is the most notable drawback to my setup. It is tolerable though cause when that power hits it pulls HARD.

Turblown

iTrader: (12)

I would move up to a 4" exhaust with minimal bends first then start playing with the turbine housing. Doing the turbo back exhaust will help with pre turbine pressure too, not just the " lag". You have a mismatched turbine to compressor wheel ratio. You should have a Q trim in there with a 1.0. I'm going to bet at 20psi you have pretty high pre-turbine back pressure.

Dudemaaanownsanrx7

iTrader: (23)

Here are the specs on my turbo wheels. A Q trim would have even more lag, but regardless, the turbo was a re manufactured unit that I got for 450 so there wasn't really a choice in wheel trim. I'll probably do both the exhaust and turbine housing at the same time, I see no reason for me to run an open volute housing when my manifold is divided. But It's good to know that a 4" exhaust will probably help things even more. What would be the difference between a q trim in a 1.00 and a p trim in a 1.15? wouldn't both add lag while increasing peak flow and reduce pre-turbine backpressure? It's easier to change housings then wheels out. I don't want more lag in any case. In fact reducing it is a preference.

Turbine Wheel:

-Exducer Diameter: 2.53"
-Mayor Diameter : 2.91"

Compressor Wheel:
-Exducer Diameter: 2.72"
-Mayor Diameter : 3.58"

ChrisRX8PR

I would say that the P-trim 1.15A/R would be laggier than the Q-trim 1.00A/R

The housings loose a little bit of efficiency as the A/R get bigger. It becomes harder and harder to accelerate the air and spool the turbine at the nozzle. that is the reason why they rarely go above 1.32A/R. Ideally you would want an A/R between .8-.9 and something like an S Trim.

At least in my experience, once you reach 1.00 if you want more flow you should jump up a wheel. But that is my experience.

Either way, switching from the open volute .96 to the twin scroll 1.00 should increase flow while reducing lag....I would stay away from the 1.15 A/R.

Chris