Precision Turbo compressor maps
 

Hey guys, I know like myself some of you are probably looking for compressor maps for the new precision billet turbos. In my search I found this post on evolotionm.net from Michael at ETS (extreme turbo systems).
just thought I would share this as I'm sure I'm not the only one that has been frustrated by the lack of compressor maps.

here's the thread
http://forums.evolutionm.net/extreme...bo-kits-4.html

Smart business move (why publish real info when internet hype will sell anything?) but horrible engineering decision. How can you design a pump without lab grade empirical testing? There's another incentive to wait for more Garrett gtxr turbos.

i also dont believe hta has any compressor maps either. both the billets from precision and hta perform great so its not terrible. would we all like to see a compressor map yes. what has been done is lots of estimating. between the supra forum and the buick gn forum here are the 2 estimates i found people had listed.

6265 68lbs
6765 77-80lbs.

but pressures are all unknown so thats where the map would come in handy. from all the searching i have done they seem to be the same as a cast wheel up until 20-22psi of boost. once you hit above that they really start to move air. to get the best results you need to run above 22psi.

That's what I've heard as well, it only shines in the higher PR's. But, when I was speaking with the tech department at Precision, he told me the 6768 (HPQ) will do closer to 90 lbs/min, although it may not be until ~40+ psi.

I think proper testing on a rotary will be the only way for us to see what these turbos' limits are at lower pressures.

arghx, you really are skeptical about these turbos aren't you? What do you have against them?

I'll say this: I've relented a little bit on them--on my criticisms of the turbos themselves. That was only after looking at PEER REVIEWED research from REAL ENGINEERS about all the variables involved in compressor wheel design, especially things like clearances of the compressor wheel tips etc. I went so far as to actually pay money for one SAE paper off their website. I won't claim to understand every little factor involved in centrifugal pump design (and that's all a turbo is) or all the differential equations used to model them, but some of the design features I'm seeing in these Precision wheels do make sense and they agree with the literature.

What really bothers me is that they are marketed based on internet hype over Evo 4G63 and Supra 2JZ chassis dyno sheets, two engines that take very well to super high boost levels. People hype them up so much, call them revolutionary (they're still based on older garrett designs) and we can't even get compressor maps for them. They may still be some kind of improvement on a rotary application though.

All that being said, I'm sure they're better at least in some applications and they aren't that expensive... but it bothers me when a producted is marketed on viral internet forum hype rather than data of controlled testing of the part itself. I am helping a friend plan a single turbo conversion on his FD and I may tell him to try one of the new Precision wheels if Garrett doesn't come out with anything in the next few months.

^ very true there is no data for these billet turbos that are around right now. there is a good amount of real world testing but most are "i made 800whp at 40+psi". this here is a great link from the supra forums as the guy starts tuning from 18 psi all the way to 31. its a 6265 billet and you can see the big jump from 18-22psi then from 22-24 it gains 34whp which is a good jump and you can see the turbo starting to move air. he ended with 700whp at 31psi and in the supra 2j world that number will usually only be made by a old t67 turbo at the same 30psi of boost. so the billets do perform it just needs 20+ psi, any less then that they do nothing different.

link to thread.
http://www.supraforums.com/forum/sho...d.php?t=597012

+1

They may have a good product, but what I do know for sure is that these guys are full of crap when it comes to their excuse for not providing compressor maps to their customers. I like how they act like they can't build a compressor map with "real world testing and airflow in lbs/min", LOL.

However, I will give them credit in two areas:
1) Excellent use of internet hype to sell their products.
2) Effectively making the word "precision" an oxymoron.

If/when Garrett comes out with more GTX redesigns of the smaller turbos in their existing GT line we'll have a better idea of what we're dealing with.

Here's the thing: if the new precision wheels aren't much better until 20+ psi, well that doesn't matter much in most of these rotary applications. Most people stop at 15-16psi on a single turbo build because, well, 400-450rwhp in a 2800lb or lighter car is fast enough on the street. A basic streetport and sometimes stock ports can flow enough air to achieve that on a 13B. On most 4 cylinder engines you can't make that kind of power at that boost level without major headwork at least. And Rx-7 owners tend to care less about big numbers than Supra owners.

Most of us who do crank the boost higher with some kind of knock suppressant still stop around 20-21psi, which is supposedly where the Precision wheels just start to pick up steam. At that boost level on a single turbo rotary the car is usually so fast it's difficult to drive safely on street tires, especially in cold weather. I know with my pitiful tires my car was uncontrollable at 21psi on a relatively small 60-1 T04S turbo.

They're a smallish company trying to save money, that's all. Garrett is a big OEM supplier which provides a lot of information to the aftermarket as part of its marketing strategy. So making a compressor map isn't that big of a deal for them. Whether or not they make the best products, Garrett seems to release more info about their GT series turbos (turbine maps etc) than any of their competitors. If I had an Evo IX or a JZA80 Supra I'd be more inclined to jump on the bandwagon because those dyno sheets would mean more.

Still, if my Garrett T67 turbo blew tomorrow (still running fine even with oil cooled CHRA and no BOV) and I had the money I would very seriously consider the 6765 just to try it out.

very true most do stay at 15-16 psi. thats why spending more money for a billet turbo is pointless unless you plan on surpassing 20psi. i have an a-spec kit on order its the 6765 billet with a divided turbine housing. i am going to run 25-28psi and see what happens. i run c16 full time just to keep my 35r happy with lower egt's at 22psi. the t3 starts to get hot when you up the boost.

Sounds good, that's equivalent to a 500R or T04Z/T04R in terms of its nominal measurements. Can you do some testing at around 15-16psi though, just to contribute to the discussion?

yea i will have a pump gas tune at 15psi since thats what i run in the winter months. i try and take the car out at least once every 2-3 weeks to keep it from carboning.

I'm also ordering a precision turbo from a-spec, the 6265, but since I'm in need of a rebuild, it'll be march or april before I can get any idea of the power level. My results may be skewed a tad also because I'll probably end up running e85. The real selling point for me with the precision units is the price, a-spec quoted me 800 plus shipping for the billet 6265 with the divided hotside that I can't seem to find anywhere.

I have a 6765bb turbo. Old setup was a t3 35r, made 435 at 22 psi with water inj. Same setup with the 6765 made 470 at 22 psi with water inj. The only changes were the turbo, mani and downpipe. In my case the 67 spools faster, makes more tq, and has a wider tq band over the 35. Very glad I made the switch.

ryan what type of dyno are you making those numbers on? sounds like you made a good choice with the 6765bb thats what i picked up as well just waiting for it to come in.

435 was on a superflow, 470 was on a dynojet

ryan only reason i ask is that the numbers seem low for 22psi but then again your running only water inj so i am figuring your timing is very low. must make some serious torque though.

here is a great comparison picture of a cast 67mm and the billet 67mm wheel. they are basicly the same design but the billet seems to have 2-3mm more blade surface area. now why we only notice the extra flow of the larger blade area above 20psi?

It's good to hear you are satisfied with the turbo. Unfortunately, it's hard to make a direct comparison because even if you had gone with a traditional T04Z setup (as opposed to the Precision wheel which has the same nominal dimensions) there would have been a different powerband etc. The 35R is closer to a 6262.

We'd need expensive modeling software or lab-grade equipment to fully know that answer.

I have actually started tuning on the RX7 and have made some big progress this passed week. I look to start tuning the boost side of things as soon as I source some 10's for spark plugs.

(T4 BB PT6265 .96)

Same dyno, same day another 67 made 514 at 25 psi on meth. I don't know the tq #, because the dyno wasn't calculating it correctly, said I made 765 ft/lbs.

ryan was that another billet 67 or just a reg 67 setup?

billet

I would absolutely love an update or a pm to an active thread with some real world data and results for the Precision line. ive been following Howard Colemans posts and arghx posts and have been talking to my local dealer about the 6265 for a few months now. The manifold is done. waste gate is ready... i need a good turbo for the large street port 13b (pineapple templates) to go along with my water injection (homebuilt kit/rice racing type)... Not scared of 20+ psi :)

Mine is running, and it runs its ass off. Hoping for some dyno time next month, haven't made it too big of a priority, my butthole gets pretty tight!

sounds like you'll be about a month ahead of me, hoping mine will be running in a month and dyno time the month afterwards