Honda D Series Forum banner

1 - 5 of 5 Posts

·
Registered
88 hatch
Joined
·
789 Posts
Discussion Starter #1
I've been wanting to smooth out my tq ever since the car got off the dyno. I don't need more power it's plenty fast and a tire shredder as is but I'm wondering if a smoother curve would help with traction. So on ebay I have found the evo 9 10.5cm hotside which I feel isn't a very big increase and a aftermarket 11.5cm hotside. I don't know which one to get. I don't want to increase spool time too much but I want to see my tq actually hold.



That's my graph. 9:1 cr, rocket regrind cam, performer x intake, and a twin scroll manifold. 14 psi is low and 20psi is high. It chokes really bad on the higher boost. Rocket said the cam might be part of it too but if I get a bigger cam wouldn't I need the 11.5 hotside even more? I seriously don't want more power just a better looking graph.
 

·
Registered
94 Integra
Joined
·
1,225 Posts
If I'm reading that graph correctly (hard to see numbers), you're hitting 200whp at ~4300 rpm. That is a VERY fast spool for a 1.6L that's making >300whp peak. Most b-series don't even get power that early. To give you an idea, a ~300whp GSR w/GT28RS hits 200whp around 500 rpm later.

Speaking of the GT28, your turbo isn't that much different from the GT2871R in terms of wheel sizes - the compressor is a bit smaller but turbine is a bit larger. The 9.5cm housing is probably as big or bigger than the T25 .86AR hosing.

My guess is the cam is not helping. You need a much larger turbine housing for that cam, or a smaller cam for that turbine housing (less peak but flatter torque). The larger housing will help, but to flatten the torque you'll need a boost controller that increases boost with RPM.


Honestly the only real solution to having a flat torque curve in boost is to get a GT30 or smaller turbo and a modded 1.8-2.0L b-series. Very few d-series, nor any other import motor, will hold torque to redline. That's not to say they're junk, you'll just be "stuck" with a lot more mid-range torque. That's only a bad thing if your parts can't take the stress.

Edit: one more thing I forgot about your setup - a divided manifold effectively reduces the housing's AR. When I spoke to Jeff Evans about it, he stated a 0.78ar divided T3 will flow a bit less than an undivided 0.63 housing. The 11.5 housing will flow more like a 0.63 housing and the 10.5 will be more like a .57 housing. The 9.5 flows a bit more than a T3 0.48 housing. Divided turbos spool like mad but make much less peak power than an undivided turbo with the same housing/turbine size.
 

·
Registered
88 hatch
Joined
·
789 Posts
Discussion Starter #5
Thanks for the input guys. I'll definitely pick up the 11.5 hotside this winter while I'm making some other changes.
 
1 - 5 of 5 Posts
Top