The turbine wheel and the wastegate flapper valve are about as large as you can fit in the OEM footprint. The wastegate flapper has an anti-rotation feature, it’s the triangular-shaped nub on the valve itself. It has been found that if allowed to spin, wastegate flappers, can actually saw themselves off the arm and fall off! Another cool thing about the stainless exhaust housing is it won’t turn into a rusty mess when installed!
The Precision turbo comes with a ball-bearing center section. Ball bearings greatly reduce friction in the center section over plain bearings and reduce spool time by as much as 20%. They also have a long service life and reduce oil heating. The turbo comes with the proper oil feed restrictor installed as the ball-bearing center section needs a lot less oil flow than plain bearings. Precision uses ceramic ball bearings which have a durability advantage over standard ball bearings used by some other turbo manufacturers. The Precision turbo also has a water-cooled center section like OEM which is also a good feature to improve turbo reliability.
We ordered our turbo with the optional 20 psi actuator, the standard actuator is a 15 psi unit. If you have a built engine and want to run higher boost levels, this is essential. However, the minimum boost possible is around 14-15 psi so you want to make sure your engine can take this on pump gas. It is probably pushing it for the stock engine.
The Precision turbo on the left is obviously a lot bigger than the stock IHI VF39 turbo on the right. The stock turbo compressor inlet is only 46mm or 12 mm smaller than the Precision turbo. The compressor housing is much bigger than stock and has a clearance flat spot machined in it for block clearance. The engine case also has to be ground slightly for clearance but it’s not that big of a deal.
The Precision Turbo turbine discharge diameter is 56mm vs the stock 48mm, a huge difference! Precision does not list the specs of this turbo but externally it seems about like what a Garrett G30-770 is like. Note how much bigger the Precision Turbo’s wastegate valve is than the stock turbo.
15 comments
Great artilce, but it would be helpful fo provide id’sfor the 3 different curves for the two dyno runs. The legend on the left side of the graph was clipped of in the window. Based on text, the left side was @ 25 psi, and 17 on the right ?
Good Garret article on A/R’s, with differences shown on track performance.
https://www.garrettmotion.com/news/newsroom/article/turbo-tech-how-to-turbo-and-the-difference-an-a-r-makes-for-optimizing-your-turbo-system/
The traces on the dyno chart are 25 psi, 17 psi, and a full bolt-on VA STI. The point was that the power falls as the IAT climbs drastically. Conversely, on our time attack cars, we have been going to smaller turbos and A/R and turning faster lap times even with sometimes hundreds less HP. For instance, the ENEOS 86 went from around 1000 whp to 750 and we went many seconds a lap faster due to better driveability and not being so solid on the traction control. Most of the time in Time Attack mid range helps quite a bit for reducing lap times.
Thanks for the reply Mike. Your faster TimeAttack laps with the smaller upgraded turbo & A/R are similar to how a smaller A/R turbo was better for circuits with more corners, and the larger A/R was better at fast tracks, as discussed in the Garret link I provided.
But my question about the Dyno runs was related to the 3 pulls for each boost pressure. I figure the segmented green curve is stock, the dark maroon is 1st upgrade, and the light maroon the bigger Precision Turbo upgrade.
“The traces on the dyno chart are 25 psi, 17 psi, and a full bolt-on VA STI.”
I get it. I should have looked at the graphs more carefully.
I should have explained it better.
Can’t wait to see the results! Thanks for being so transparent with all the teething problems. I can’t imagine the dyno bills being too pleasant on your wallet, but even if money is no object, Church must have a looong wait list as well.
The results we currently have are decent, we are just looking to optimize things and make them efficient as possible.
What size injectors are you moving up to? I’m excited to see this turbo do work. The results from that 55mm version are impressive.
Thank you for pointing out that I stupidly forgot to put the injector size in the story, I edited that! They are 1700cc/min.
All good. I just got my IAG-700 block installed, so I don’t have the same long rod setup you have. I’m thinking that the ID1300’s and precision turbo setup you’re currently rocking is about the right setup for my car. I’ve got a lot of the same mods with a dual radium hanger, single W450, XClutch twin disk, etc. I need to replace my ID1050x’s with some ID1300’s and grab a delicious tuning flex kit. To say I’m watching this build closely is an understatement.
A lot of those decisions were made based on these stories. Appreciate all of the work you put into this. Hopefully the word gets back to your suppliers so they know that your publication works. 🙂
I am currently running at 95% duty cycle on E85 so maybe you might want to consider the bigger injectors. They just run something like 13:1 at idle to get a decent idle. The 1300’s idle at about 13.5:1. The X disc is awesome, once it breaks in, it’s nearly as smooth as stock. Before settling on a fuel pump check out what iWire says about a big single. I would have probably done a brushless pump but there was none of the right size available when I was piecing things out. Deatchwerks just came out with some cool smaller brushless offerings.
Hi Mike,
Any updates on latest Dyno / test results ?
Did it resolve the issue up the top end ?
Looking at the same turbo for a high revving built EJ207.
Cheers
Starting to work on the car again now. It’s sort of an aversion to tearing into a wonderfully running car, hahaha.
How did this project turn out? I’m very interested in the gen 2 555 and 585 turbos, but there just isn’t any feedback out there. I have a 19 STI with all supporting mods for the set up. I just need to decide on the turbo and I’ll run ID 1300’s. I want an easy 400whp on 93 pump. But I want fast spool and a flat torque line. The FP Green HTZ leads the pack for me right now, but this turbo really grabs my interest, mostly because of the exhaust housing. If you could point me to other users of this turbo, that would be great too!
https://motoiq.com/project-gd-sti-we-dont-need-a-damn-rotated-mount-turbo/3/