I am in the process of my first turbo build, converting a 1.6 Spec Miata into a low boost 8-9psi, race car. I was surprised at the inefficient manner in which I had to dial down the boost and how much later the torque and HP came on. It would be nice to see the boost come on earlier and just not build as much instead of it getting all dumped out the wastegate after lengthening the actuating rod.

I was seeing tons of torque at 4200 RPM's with a max boost of 13psi but when I dropped the boost to 9psi it moved the boost (and the torque) way up the rpm band to overcome the open wastegate.

I am using a T28 turbo. Any suggestions would be much appreciated.

Jeff

 

best solution: ewg + mbc/ebc
cost effective solution: low boost wga can + mbc

 

Vlad, thanks for the quick response but I have no idea what all of those tla (three letter acronyms) mean.

Jeff

 

EWG = external wastegate
MBC = manual boost controller
EBC = electronic boost controller

What specific T28 are you using. Knowing it is a "T28" does not actually tell us anything overly useful about the turbo.

 

*edit: he beat me to it.

wga - wastegate actuator

 

Garrett T28-2, that is as much as I know about the unit.

So there are alternative wastegate/boost controller solutions. Interesting, how do they work?

Jeff

 

Run a huge exhaust with no backpressure:

2.25" v 3" on the same setup and boost level.

use a MBC or EBC even at the low boost pressure.

get a wastegate can with a huge diaphram.

Size the turbo to the task at hand:


my 50 trim T3 vs. a 60trim T3, same boost, same setup

 

You will have to take a closer look at the turbo and try to find the tag on the CHRA and give us a good picture of it or all the numbers off it.

 

Here is a pic of the turbo.

 

take pics of any markings and stampings.

 

looks like ebay special.
meaning you won't know any of the specs unless you actually take it apart and measure. also if that thing is unported you will get tons of boost creep in upper gears.

 

HKS makes an 8psi actuator for the SR20 motors. I used it on my turbo setup and it works great. The thing costs over $100 though.

 

also, im a little confused by the OP's post. are you using a MBC or something to increase boost from 9 to 13psi? or are you just tightening/loosening the rod.

that's an issue right there.

the proper way would be with an MBC and you'd get result like my setup:



The only change in low-end torque is where you start making more boost above that where the lower boost threshold is. The spooling characteristics should remain identical.

 

I'm pretty sure his actuator spring is factory set to 13psi or something, and he's extended the arm to lower the boost (Because you can't use a MBC or EBC to lower the boost beyond the actuator spring level). This has resulted in the wastegate flap being open partially, which would make the turbo totally inefficient because it would be bypassing most of the exhaust. What he really needs is a wastegate actuator that runs the PSI he wants or less then what he wants, and then use a MBC to reach the proper level.

 

yeah, that's an issue. get a 7psi actuator and increase boost from there with a MBC.

 

they make 7psi actuators for those chinabay turbos.
pick one up, slap it on, bump up the boost to 8-9 with an mbc and you're set.
and if that wastegate port is untouched, be sure to port it as much as possible or prepare for some nasty boost creep in the upper gears.

 

here's mine:






dual port IGW. I only use the single port, it's a 7psi can, but holds 10psi strong on my setup.

 

I've always wondered, what does the dual port do?

 

works sorta like a ewg, where you can control the pressure differential to control boost a little better. I found it worked well the traditional way, so i didnt bother.