bzyq2001

I read that gt35r with divided 1.06 a/r T4 housing has better spool than with T3 0.82a/r housing - is it true?
I'm courius witch one housing will be better for DD, fully built b18c1 with 9.5:1 (stock bore, maybe 82mm) with mild ported head and pro1 cams and no more than 22psi pump gas
Only options are divided t3 0.78a/r or divided t4 1.06.
Is't 0.78 a/r to small for pro1 cams?

polarbear111

There are too many factors to determine what spool is better. If you think the scroll wall can occupy .24 A/R - I dunno about that. I'd say go with the 0.82, twin-scroll turbos are over-rated...

Evans-Tuning.com

The ts 1.06 t4 housing is night and day better than the .78 a/r t3 housing. There is a huge difference in power potential. There is an additional 500 rpms quicker spool on the dyno with the 1.06 ts t4 housing on the gt35r compared to the .82 a/r t3 housing. The transient response on the street with the divided housing makes it feel like a 30r.

polarbear111

Having tested multiple twin scroll housings before, I simply don't believe on a 4cyl motor you will have any real noticeable differences, especially not enough to make 500rpms quicker spool AND more top end power. The exhaust pulse collision of most 4-bangers just simply isn't that extreme and neither is the scavenging benefits of going with a divided wall. Furthermore the GT30 turbine wheel doesn't have the surface area to really benefit from a twin scroll setup.

Minor benefits? Maybe.

500rpm spool + more top end power? Sorry I just don't buy it...

Evans-Tuning.com

I have done back to back testing with the gt4088r with the .85, .95, 1.06 and 1.19 a/r turbine housings on a 84 x 89mm honda b-series engine. The 1.06 a/r is the happy medium between all the housings. It spools faster than the .85 and .95 a/r housings, as well as having 50-75whp difference in power. This testing was done 3-4 years ago on Full Race Geoff's civic, before anyone really believe that twin scroll worked on 4 cylinders.

The 35r is no exception. There is 400-500 rpms faster spool on the 1.06 a/r t4 turbine housing compared to the .82 a/r t3 undivided turbine housing. I dont have back to back results on the same car, but full race does:



I really have to ask, if you are so skeptical of the differences in a/r housings on twin scroll applications have you ever measured backpressure between different housings on the same engine? If you think that there are no differences, the backpressure results speak for themselves.

BTW, I said nothing about a 30r turbine wheel. I was simply referring to that the 35r with the 1.06 ts housing has the same transient response/feel of the .82 a/r 3076r.

SD_Lurker

iTrader: (4)

Don't argue with evans, he has tested and tuned more cars than you could imagine.. If he says he tested something you can bet your *** he's test results are about as close to dead nutz as possible.♦

EARLdaSQUIRREL

that t4 divided housing would have to have a divided t4 manifold to get those results or no? if not i might be upgrading my t4 35r to the divided housing on my non divided full race t4 manifold

SD_Lurker

iTrader: (4)

Yes, of course it would have to have a matching divided manifold.

bzyq2001

so t3 .78 is making to much backpressure to work effective?

bzyq2001

Why on that dyno is the same top end power on both 1.06 t4TS and 0.82 t3 housing?

HiProfile

I always wondered that too, I think they used less boost to keep max HP the same. I think what Mr Evans is saying is the .78ar housing is about maximizing power, rather than spool/response. I'd guess the response time and spool are more similar than the HP gains. In other words, XXX rpm faster spool gives less overall than performance than an extra XXX whp. But that's only a guess, I'd like to hear his explaination.

Evans-Tuning.com

Twin scroll is not going to give more power than a undivided housing of similar size, its going to increase the transient response (cannot be measured on dyno) and spool/midrange (you can measure on the dyno). When comparing 2 different size a/r housings in divided configurations, there is a difference in spool and power. With a divided manifold going from a .78 a/r to a 1.06 a/r, the spool is going to virtually identical or will spool faster due to the lower backpressure if the housing is very restrictive to that particular size turbine wheel. The power difference going from a smaller to larger a/r divided housing will increase due to the decrease in backpressure. Its the same thing when comparing a .63a/r to a .82 a/r undivided housing on a t3 gt35r when you are talking about making more power, the .82a/r will give at least 30whp+ at higher boost levels compared to the .63a/r.

blinx9900

lol, my buddies 2.3 evo which is a 4cyl as you know starts seeing positive manifold pressure with 4094r at 3100rpm!! Its a divided housing with a shearer divided manifold. Divided housing turbo/manifold combo's can make a HUGE difference, cylinder count is not going to stop that, i can easily believe 500rpm.