One of the first things I did to upgrade my GReddy turbo when I was playing with it was to change out the actuator.
GReddy intentionally undersized it to limit the maximum boost.

 

it's too peaky too, the powerband below 6000 rpm is in the gutter

 

Thats brilliant! Thanks for sharing that. I've been having trouble trying to nail down what RPM my boost reaches certain levels in the different gears.

 

/\ I have a really hard time rubbing my tummy and patting my head at the same time


let us know what results you get

 

Your power curve looks very nice on that dyno chart, Brett!

The reason mine falls off so much at the top is I was still spraying too much meth, running 10.5 AFR and had timing pulled in the interested of safety. Not trying to make excuses, it is what it is. I am going to go back once my transmission is sorted, tho.

Also I had my boost controller set up all kinds of wrong thanks to the guy helping us on the dyno LOL. He told me to set the Start Boost and Gain to 0. Now after retuning it on the street I have my start boost at 13.8psi. Before my transmission peaced out I hit 13.5-14psi before 4,000 rpm and the car feels all kinds of brutal. I also had horrible boost drop-off so by redline I was only pushing 9psi or so.

I am going to preload the actuator arm more and keep working on the bc once a working transmission is back in the car, and more dyno time. I'm trying not to get too caught up in the numbers tho, but it's nice to see something quantified.

 

I did wonder why your low rpm power was not as good as it should be - start boost setting of 0 was not helping you there at all .
As for your boost tapering off - I think it is all to do with the actuator so preloading the arm should definately help with that .
Mine was only 9psi towards the end as well and I put that down to the intercooler . I think the turbo has enough puff to boost about 11psi to redline once i get that sorted . By my reckoning i make about 13whp per 1psi so I'm confident that double baller is within reach for both of us .

As for getting a gearbox to take 300lbft of torque - I'm not sure I want to go there . 280 is enough to spin the wheels in 3rd on dry seal which is not really ideal for the street .

 

Either that's pretty good. Just get some nice thick and sticky 275's on the back and you are set.


All this stuff is interesting, im learning something about turbo's everyday.

 

You get some sticky 275s on the rear and then you have more shock on your driveline....tire spin can actually get good for a transmission/diff since it lowers initial shock

 

I don't usually elaborate on this kind of stuff, but here are my experiences with clipping. Certain turbine wheels with many blades gain the most out of clipping. Radial Grinding (clipping) is done so that the exiting window of the turbine wheel is opened up to reduce back pressure. When you change the clip, it makes the wheel like different RPM and in some cases, makes the turbine wheel more efficient. But its a happy median between turbine RPM and compressor RPM. If you match that correctly and also match flow charactoristics, you will have a well balanced turbocharger. From there you size the housings accordingly for your application.

On a HT18 T2 turbo a unclipped turbine wheel max HP is 300 WHP. Same compressor wheel with a 10 degree clip 332 RWHP. So with the stock turbine wheel gain of 32 WHP just with a clip... The stage 3 will make 360 RWHP which is a 15 degree clip but with a 60-1 compressor wheel.

Some turbines you don't want to clip. Turbines with lesser blades will have a negative affect on performance.

 

excellent info Bryan

Brettus; I haven't had the chance to try your experiment yet. I have not forgotten!

 

Good info . How do you tell if clipping the turbine will make a difference up top ?
What would you look for ?

 

The TD06H is a good turbine wheel and the only reason I clip or replace the turbine wheel is for better boost control. That turbine wheel on a piston engine is good for 475-500 whp in unclipped form. Since the turbine housing is so small, it needs to be as minimally restrictive as possible. What you look for is how broad your power band is. When you start turning up the boost and no changes are happening in power or perhaps the power is falling off, either your turbine housing is too small, turbine wheel is the restriction, or compressor side is maxed out. There are other factors as well like exhaust system, cam/head or port restrictions that can keep you from improving power.

 

Nice info in this thread... keep it up all. I'm still waiting on further upgrades to my tune before I go redyno. I'm going to try and redyno in the fall with some tweaks to my BC to hang out around 11 psi. I'll let the crazy people push the limits.

 

/\ it is only by pushing the limits and posting our learnings that we will make progress . But yeah - with that comes an element of risk .

 

but 14psi feels so...right!

 

@Chickenwafer I do know that. But I'd get it so I wouldnt be spinning out in first gear for god sakes when I go WOT.

 

that's the fun part tho!

Drive a turbo 8 and I think you may change your mind.

 

when are you going to re-dyno 05rex8 ?

 

Possibly sometime next month. I would do it sooner, but my wife is probably going to give birth to our daughter any day. I will have to make sure all that stuff is out of the way first.

 

So- no dyno from you then LOL

Good luck with your new baby .

 

I don't know, I'm not sure if I'm ready for 14 psi lol. I'm loving the 9-11 lbs I'm pushing now though. RX-8 + turbocharger = perfect.

 

You will get used to the 9-11psi soon enough tho, LOL. I know I did and I got anxious to turn the boost up. Kudos to you for exercising self restraint, trust me I know it's difficult.

Now that I've experience 14psi and tire spin thru 3rd gear I'm not sure I can go back to 9 haha.

You're dead right about RX-8 + Turbo = Perfect. It really does transform this car into what it should have been from Mazda.

 

LMAO

Thanks man

 

lol it would get boring quick. Changing tires every 5k isnt something that I would like to do :P

I really should drive one, too bad I dont know any rx8 drivers in montreal with a turbo kit. There are some, but they are mostly the pos greddy.

 

***paging Brettus***