TurboTim

iTrader: (9)

We had a great thread going a little while ago about turbine A/R's on track vehicles. https://www.miataturbo.net/diy-turbo-discussion-14/0-64-0-86-hotside-280whp-goal-1-8-a-52543/

I would now like to discuss the other end of the turbo. The ultimate question is: What is the most bestest compressor for the typical turbo, built motor track miata?

Of the "track" setups I've sold people, there is the following:
Three people with the GT2860RS, .86A/R
One guy with the GT2871R, 52trim, .86A/R
Three people with the GT3071R, two at .63A/R, one at .82A/R
One guy is considering switching from the GT3071R to the GTX3071R debuted at SEMA this week.

And finally one guy who doesn't know what he wants, hence this thread. I am no help.

Unfortunately I haven't heard from any of the 3071 guys about how the setups actually perform on the track. Those of you with a turbo (regardless of size) and actual track data and impressions, please post up. Why did you chose the turbo you did? How do you like it? Do you wish you went larger/smaller on the compressor?

Thanks!

hustler

iTrader: (6)

...paging Jkav.

TurboTim

iTrader: (9)

I want your impressions of your 2860rs Hustler as well. Basically anyone who tracks their car. I edited my first post to clear it up.

hustler

iTrader: (6)

I've only run this turbo in my car, but I used a log-manifold previously. The GT2860rs (.86 turbine) seems to be the little turbo of the bunch but it works for what I want and most likely helps the lowered static compression. I have usable torque at 3500rpm on the track and use a short-shift and all that torque on 2 corners to avoid shifting over a crest in a hill (turn 4 @ ECR, "The Diamond @ MSR-H). With the new suspension I'm hitting several corners in higher gears, and the low-rpm torque availability supports and makes driving easier. A good example of the torque is turn #2 at Hallett, I'm in 3rd gear throughout that corner and can lay stripes on exit...in 3rd gear on low boost at ~240whp (Mustang).

At 12psi, the turbo is under prime, and this is supported by the 30whp+ increase when upped to 15psi, or maybe its the lowered compression...whatever, zero complaints from me.

In short, with my 6-speed/3.63 I'm never in the wrong gear. If I were to do this all over again, I'd have a copy of the same set-up. 250whp is right for me because I need transmission reliability and it's still blisteringly fast.

bbundy

I originally went with a 3071 because I was also going to 2.0l displacement. It is a .50 A/R compressor .64 A/R turbine Internally waste gated

I have since run the same 3071 setup with a completely stock internal 1.8l and honestly I was surprised at how well it works. Been running it that way for most of the year. It even works good for my autocross applications with several overall FTD’s and trips near the top of the PAX list running with a SSM index in a region with many multi time national champions. And if it works good for that then spool and response is obviously not an issue for the big tracks.

I’m not a master at reading compressor and turbine maps but Wouldn’t the 3071R with the .64 A/R turbine tend to spool better than a 2871 with a .86 A/R turbine and yet have more top end capability from the compressor side? I would guess not a huge difference between the feel of these turbos but I have no back to back comparison.

Bob

Savington

iTrader: (31)

I haven't driven a 2860RS car on track, but I've driven a couple on the street and I don't think my 2871R car gives up anything in spool. Maybe a hundred RPM. For that minimal bump in spool, I have way more headroom in pressure ratio and flow capability. I don't think the 2860RS will do much more than like 320-330whp, whereas I think a GT2871 will flow 400+whp.

I didn't do a 3071 over the 2871 because I didn't think the 30R would respond like a 28-frame turbo would. I still want to drive a .64-equipped 3071 for comparison. I'm fairly happy with how the 28 drives, but it definitely drives like a turbo car (I consciously drive the 2871 much differently than I drove the 2554) and I wouldn't want anything larger. I've ridden in a 3076R'd STI and it drove like utter garbage.

What's really interesting to me (paging jkav) is why the 2871 is very close to a 2860RS in driveability (practically the same), but the 3076R is dramatically worse than a 3071R. The 3076 gets compared to T3 50trims, PTE5557s, really big turbos, where the 3071 is lumped in with the 28 - the only difference is the compressor housing, same as with the 60RS/71R.

The new billet wheel GTX3071 is super, super interesting to me, though. I've had my eye on that turbo for quite a while.

thesnowboarder

iTrader: (15)

I really love the low end torque of my setup. Which for anyone who doesn't know is the GT2860RS, .86A/R. My main issue for loving it is not having to shift all the time when I want some power. I can leave it in a higher gear and concentrate on my driving and line rather than how fast the rpm climbs and forces me to shift.

I have alot to learn driving wise (have really only been doing track days for 2 years) so I think the power is still plenty for me. I also like the reliability it has given me lately. I finally have about 3 solid track days with out any mechanical issues what so ever. Solid 20 min sessions without lifting for over heating or any other mechanical issues. It's also nice to have some headroom on the turbo to support ~300-350whp if I ever have deep enough pockets to get there, and stay there.

Overall, great turbo, car is much faster than I am and I don't see myself over driving the car anytime soon.

Wouldn't you agree that w/ an intake mani/e85 ~18-20psi it could do 350? As far as spool goes, I cant tell a difference from riding in your car and driving mine. Had I rode in your car before buying mine I probably would have copied you for the additional 25 bucks it would have ran me.

Savington

iTrader: (31)

I don't think a 2860RS would, no. 350whp@18psi is ~40lbs/hr and a pressure ratio of 2.2. The 52-trim 71R is at ~71% efficiency there, but the 60RS isn't even on the map anymore - the edge of your map is ~69% efficiency making ~50whp less. This corresponds to what Trey sees, making ~300whp at around 18psi. The ethanol makes the power possible, but the turbo still has to flow the air.

The difference is fairly striking when you compare the maps side by side - the 2860RS is tapped out at 2.6:1 (~23psi) and 36lb/hr, whereas the 2871R will support nearly 30psi and 44lb/hr - huge gains for the virtually non-existent tradeoff in spool.

Faeflora

iTrader: (2)

In for interesting thread.

rharris19

iTrader: (41)

My old setup: 2.0L with BEGi S6 Kit 2860RS .64 housing. This fell on it's face and was a direct effect of me not knowing how to read a damn compressor map. I have driven a 2860RS .84 and a 2871R .84 and both felt like they had a smooth delivery with negligible difference in spool. The difference was that the 2871R didn't ever feel like it was out of it's efficiency range.

In my mind there is no trade off in going to the 2871R .84 and unless you want to make 375hp in your track car, that should be the turbo of choice. I am an N/A guy for now, so take my advice with a grain of salt.

hustler

iTrader: (6)

If there is no trade off in spool, is the only increase in performance on the GT2860rs from slightly superior efficiency in the 230-260whp range? Again, I'm to the left of the prime currently, but when I put in that extra 2psi, you can really feel the motor "come up on the turbo."

If we had a transmission available that didn't puke on the track at <300whp after extended use, I would easily suggest the 2871. However, it looks like the GT2860rs is the optimum turbo for goals of 230-260whp but only by a small margin in comparison at roughly 3-5% which translates to maybe a 10whp gain if your target boost is set within that range.

I agree with Nick...we have a lot to learn and with only 2-3 years of experience; I'm growing tired of chasing you bastards that grew up with Karts while I was fighting for our freedom in the Balkans.

jacob300zx

I also had the 2871R .84 and really liked the way it spooled for a track car. The smaller turbo's are more fun for goofing around on the street (2554), but I feel the GT28 and larger spool more linear for track use. I only ran 10psi about 230whp and it was fun. I don't know what Spoolin2bars has but it seemed to spool earlier and more violently. Its that on off modulation when at the edge of traction in a long corner that I liked better with the larger turbo.

bbundy

If you look closely at the maps for the GT3071R with the .64 AR turbine and the .50 AR compressor housing it sort of seems to me that it could both spool quicker and make more top end than the GT2871R with the .86 AR turbine and the .60 AR compressor. Its just a matter of which one maches flow charicteristics between the two sides of the turbo better I would think. It would be interesting to compare them back to back. probably require driving impressions more than dyno data.

Bob

hustler

iTrader: (6)

I should note that on my turbo the target boost engages with an "oomph" rather than a "wham" if that makes sense. Pretty easy to drive and easy to anticipate on the track with a very slight "lag."

TurboTim

iTrader: (9)

Ok. GT30 .83A/R & GT28 .86A/R turbine maps look the same.

Compressor maps: Damn they look pretty close to me




Great info guys, keep it coming!

hustler

iTrader: (6)

The best part about this, which sometimes fails me when I have to make important decisions, is that either turbo will make him smile every time he drives the car. As long has he makes his target power or close to it, he can't go wrong. No one in here has a negative perspective on any of the 4-turbos we're considering.

BTW, its also funny to think back to all those people who told me 4-years ago that my GT2860RS was "too big" and I wouldn't like it. The times have changed around here.

Faeflora

iTrader: (2)

Has anyone seen compressor maps for the new gtx30 or 35? Link?

JasonC SBB

Do you have a dyno plot of it?

rharris19

iTrader: (41)

I need to ask Steph if she still has that. I think it is up on here somewhere, but it alludes me.

Savington

iTrader: (31)

Having owned and tracked both setups extensively, I disagree. The 2554 is an easier car to drive because the power comes on far more quickly when you move your right foot. I could practice fairly standard throttle application with the 2554 (pick it up at apex and roll into it slowly) and the car was fast (for 200whp). With the 2871, I have to consciously pre-apply throttle ASAP - even if it's just 10 or 15% worth, I feel like I need to get the turbine spinning a little to improve the response once I do actually want to apply throttle at the apex. If I wait until the apex to pick up the throttle, I never feel like I've got the throttle response I want on exit - it's always that split second behind me, whereas picking up early just to get everything started allows me the control I want on exit.

It also makes sweepers and transitions much more difficult, since I can't make minute throttle adjustments and have them quickly correlate to attitude changes - it takes a split second for the 2871 to wind up, but because it takes those few hundred milliseconds, I can't roll in and out to adjust the car's attitude as finely as I was able to with the 2554.

Once boost actually comes on it's a very smooth application, but it is delayed ever so slightly with the 28 frame turbo. This is the primary reason why I've wanted to stay with a 28-frame - the delayed spool RPM doesn't bug me, but transitional response does. I don't think I would want to have anything worse than what I have now. That's also why the new GTX turbos are so interesting - a lighter billet compressor wheel means less inertia to overcome when I am trying to alter turbine RPM rapidly, and improved aero on the wheels may mean that the turbos flow better at lower RPMs, giving the tip-in response I want. I'd pay a lot of money for a 500whp-capable turbo with the same transitional response as my 400whp-capable 2871R.