Track-use turbo compressor discussion
 

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!

...paging Jkav.

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.

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.

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

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.

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.

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.

http://img.photobucket.com/albums/v3...48-1comp_e.jpg

Attachment 193135

In for interesting thread.

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.

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.

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.

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

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."

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

Compressor maps: Damn they look pretty close to me
http://www.turbobygarrett.com/turbob...0-15comp_e.jpg

http://www.turbobygarrett.com/turbob...71R_comp_e.jpg

Great info guys, keep it coming!

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.

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

Do you have a dyno plot of it?

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

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.

Look closer at the map for the 2871 56trim and the 3071 56trim - it's the same. The maps look different, but when you start comparing RPM lines vs. flow rate and pressure ratio they are virtually identical.

2871 56trim: http://www.turbobygarrett.com/turbob...-1&2comp_e.jpg

3071 56trim: http://www.turbobygarrett.com/turbob...3&20comp_e.jpg

What is interesting is the turbine maps. From what little info I've been able to find, I know two things:

1) turbine maps can fairly accurately predict how much boost will be produced at a certain RPM
2) the maps that Garrett publishes aren't enough to actually do the calculations.

Hopefully they are good enough to compare in-kind, though, so let's do that (and if they aren't I'm sure jkav or JasonC will be along shortly to embarass me).

Here's the 2871R turbine map, pay attention to the red .86 line. Peaks at around 21lb/min. http://www.turbobygarrett.com/turbob...47-1turb_e.jpg

Here's the 3071R turbine map, pay attention to the red .64 line. peaks at around 19lb/min. http://www.turbobygarrett.com/turbob...3&20turb_e.jpg

So it would appear that the 2871R .86 will spool a little slower than the 3071R .64. The question is this: If the 2871 has the same compressor, and a less restrictive (slower spooling) turbine, will it ultimately make more power?

I disagree, it seems with the smaller turbo's a 10% push on the go pedal gives 70% power. I feel its just too touchy. Which is what your describing. I prefer the more linear response from the larger frame turbo.

That's a problem with your boost control, not with the turbo. Proper TPS-referenced EBC control will totally eliminate partial-throttle full boost conditions.

What I was specifically referring to was the TIME it takes for the change in throttle to result in a change in power - it takes longer with a larger turbo due to less restrictive hotside, larger/heavier wheels, etc.

Actual driving may prove you might be correct about transitional response and lower RPM but the GTX map I've seen does not support those suppositions. See this one for reference:

http://www.realstreetperformance.com...PRESSORMAP.gif

And the GTX compressor map by itself.

http://www.realstreetperformance.com...RESSORMAP2.gif

And the GT compressor map:

http://www.turbobygarrett.com/turbob...88-9comp_e.jpg

This is may just one of the turbos though but it looks like the GTX flows more at the top end, not the bottom.

tell me about it. when my buddy first put this begi/fm prototype kit on my car (formerly his car) the consensus among all miatadom (circa 2000) was that you were "pushing it" if you made over 170whp on a stock block 1.8L! lol... as a matter of fact he built this motor in my car so he could make 200whp "safely". crazy huh.

+1. I've been preaching TPS-controlled boost targeting since like 2002.

An improvement for those with a standalone EBC is to place its sense point in the ic pipe before the TB and not on the intake mani. It will help some for those with wee turbos, because it doesn't try to make the mani hit full boost when the throttle is partially closed.

yay

http://www.boostedmiata.com/gallery2...argets_ms3.jpg

MS3 FTW again.

I was referring to turbine RPM, not motor RPM, and the charts you posted actually support my theory. :)

Also, since the 2871 has smaller wheels and uses the A/R to make up the flow, will the lower inertia of the wheel provide better transitional response than a 30R turbine wheel while still out-flowing it?

Also, since I've hijacked the shit out of this thread to blab more about turbine flow and wheel inertia and transitional response, the answer to the original question (IMO) is that the 71mm compressor gives up nothing to the 60mm compressor, and therefore you should use the 2871R over the 2860RS. The 3071 and the 2871 have the same compressor. The new GTX wheels change the game a bit but as of today, IMO, the best compressor for a 275whp+ track miata is the 71mm.

1) what kind of a huge ****** quotes himself?
2) why does the GT2860rs exist if the 2871 surpasses it in all considerations

1) oops I preemptively forgot to buy your flameguard. :giggle:

2) Because it existed first? I don't know, it's pretty clear that the 2871 performs the same as the 2860 except for where it will flow 80whp more up top for basically no spool loss.

sav, i dunno if i would call that a jack. you could spend a lifetime searching other forums without ever finding an analysis like your posts on this thread. mad props sir.

i wonder if we have ourselves a little 2 horse race going on. BW has some new stuff with a similar sounding cold side to GTX and an interesting sounding turbine wheel too.

http://www.full-race.com/articles/bo...fr-turbos.html
http://www.motoiq.com/magazine_artic...ature-set.aspx

everybody is telling me to ditch my 2860 for just this reason. compressor runs out of lb/hr just when things were getting interesting.

I'm still thinking about this and wouldn't a more interesting comparison be: can the 2871 0.86 beat the 3071R 0.63? (actually, tie goes to 2871 because angular momentum advantage).

http://www.atpturbo.com/root/maps/gt3071rturbine.htm

I'm surprised nobody has spoken up for the 2871R 0.64 housing. I've heard really good things about this combo if you can overcome the problems caused by the lousy internal wastegate (boost control).

EDIT: i'm stupid. 0.64 housing covered in the other thread.

Somebody has to wash the dishes when the master has finished eating.
I think this is the real reason. When they came out with the GT2860RS it was just an experimental hybrid that happened to perform better than initially expected. It led to more experimentation.

This.
I've been hearing that the leader in technology is definitely not Garrett anymore. Others, including BW are really making a name for themselves on some of the other forums. It sucks that they are so secretive with their compressor maps. I'd love to be able to compare them overlaid.

I really like where Borg Warner is going. It's nice to see some new (and some recycled) tech with turbos that basically haven't been updated since the 60's. I'm curious to see results once they start getting adopted.

I think they haven't released maps yet because they were just announced officially at SEMA two or three days ago. You sure are impatient. ;)

Edit: Leave it up to the Evo guys to track down all the BW EFR maps...

http://www.turbodriven.com/en/perfor...Reference.aspx

Yah what is up with turbo manufacturers not posting their compressor maps? I just called precision and the guy who answered was very knowledgeable and helpful but he said that they don't do compressor maps, they "test their products on real cars". :|

I called up ATP to get more info on the GT-X series.

The new GT-X3071 flows 60lbs
The new GT-X35 flows 80lbs.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!

Full Vband turbine inlet and outlet is scheduled to be available early next year as well. :o GT-X2 frame series is in the works. GT-X2 might be the real shiznit. Could run an efficient street friendly 250hp with lottttts of headroom.

I am excited to see these GTX turbos come out and get more smaller sizes.

the billet wheels are amazing.

ps there are tons of companies out there doing them... garrett just has their rep.

lol, rather than test their products on real cars, they most likely wait for TiAL to post it on their behalf. That piece of shit company somehow manages to stay in business.

I’m not so sure about that. On the exhaust side the 3071 has a bigger paddle wheel in housing with more throttling of the exhaust flow impacting the paddle wheel blades. More dynamic pressure acting on a larger surface area at a larger radius. Seems like it would be more responsive to sudden changes in exhaust gas flow rates with higher velocity gas impacting blades with a larger surface amd a larger radius making more torque to the spinning objects as it accelerates from the mid range in rpm. Inertia effects may not be primary to the difference in response.

Bob

Above boost threshold in my 3071- about 4000rpm, throttle response is near instantaneous.

Do you know for a fact that the 2871 has the same or better transitional response than the 2860RS?

Having driven both, I can pretty much say that, yeah. If you drove both turbos back to back at 12psi I honestly doubt you would be able to tell a difference.

Check out the compressor maps for both of those turbos - the 2871 outflows the 2860 by a solid 5lb/hr even at 50,000-80,000rpm. It's a larger wheel but it still feels good because it flows so well at low shaft speeds.

This thread makes me want a turbo speed sensor really badly.

ahmen brotha

i was looking at repurposing this and putting a splotch of ink with a silver sharpie on the compressor wheel.

http://www.salvatoreaiello.com/image...rSchematic.jpg

then i was looking at the LM2907 and wondering if the curcuit could be simplified. i dunno the switching speed of a LM2907. seems like it should work, we're only talking 2khz. otoh, you maybe could use an I/O channel on MS3 and just use a frequency divider down to some reasonable interrupt rate and leave off the voltage conversion piece entirely.

http://www.national.com/mpf/LM/LM2907.html

I'd be interested in making one of these, but i'm not sure how hard it would be to drive a laser diode/photodiode. they are a bit finicky...

You may have a point. Everything I've read has said that once you are above boost threshold, shaft inertia is king, but there's not a lot out there on that topic. It will DEFINITELY spin down faster. The 30R turbine wheel has about 10% more rotational inertial than the 28R wheel.

a datalog of shaft speed vs throttle position vs rpm vs intake pressure would be interesting. if you only look at the 71mm stuff you would only need to instrument one compressor housing and then pass it around to folks with t2/t3/tial <dot product> t28/t30

pm me if you would be willing help me with the photo side of the circuit above. i'll try to build something (should be < $20).

Track-only 275 rwhp Miata = GT2871R. A 2860RS will work well too, though it'll make a bit more heat and backpressure. In the T25 housing, I like the 28 turbine better than the cutdown 30.

2871R and 2860RS coexist peacefully. 60 has better transient response and lower boost threshold and while it doesn't support as much power as 71, it won't surge in the apps that a 71 will.

Billet comp wheels offer no inherent performance advantage over cast for aftermarket use. They're simply a way to make wheels in low volume without needing to create a casting tool. They're blingy, but that's about it.

GTX has higher flow and PR potential but they shift the map to the right so there's the potential for surge operation.

B-W EFR looking promising. Feature rich. Very well thought out approach. Curious about turb aero performance on them.

Jay, can you comment on whether turbine A/R, wheel size, or mass moment of inertia has the greatest effect on transitional response? (Transitional response defined as the time it takes for a change in throttle application to correlate to a similar change in boost pressure.)

I noticed something similar to this comparing my T3 Super 60 (pretty much same wheel as the 2860) with a 2871 at a dyno.

I would spool much faster than him, however, at lower boost levels he was actually making the same torque as me during spool up.

https://www.miataturbo.net/attachmen...1&d=1288962392

Real Americans™ use 2871Rs.

In the case of 2860 and 2871, the larger comp wheel has a touch more inertia but, overall, inertia is dominated by the turbine side.

The factor at play here is the turb/comp wheel speed match. The 2871's larger comp whl is forcing the turb whl to rotate slower than it really "wants" to, which adversely affects its efficiency (it wants its blade tip speed to be closer to the exhaust gas velocity that is impinging on the turb inducer).

Efficiency -- whether you get it on the turb or comp side -- is one of the most key ingredients to transient response, boost threshold and backpressure.

Same here. I’ve had co drivers autocrossing my car this year and the comments are that throttle response is a non issue, what lag? If it is not an issue for autocross then it is definatly not an issue on the track. The car makes somewhat silly power around 300hp with 17 lbs of boost. Peak torque around 4500 rpm which dosn’t seem much different than the 2871 plots. I’m guessing some because I haven’t dyno tuned it since going from a built 2.0L to a stock internal 9.0:1 1.8l protégé bottom end with a stock 99 head. The 2.0L was closer to 370hp and made 320 ft lbs by 4500 rpm. At ~ $9,000 less for the stock motor it sure doesn’t feel like it gives up that much performance with the same turbo setup.

I also have a long runner equal length manifold which everyone says is not suppose to spool as well as a short manifold with a good collector.

Bob

So a 3071 with a larger turbine wheel might be better matched to the 71 compressor?

What about the housing size AR effects? it looks like you can get the Turbine map to look the same or similar for different size wheels by changing the AR of the housing. I assume there is a matching effect going on there as well where some combos work better than others at optomizing some charicteristic of the behavior.

Bob

The 30 turbine is 56.5mm (if I recall) and the 28 is 54.9mm. Pretty small potatoes, esp compared to going from 60mm to 71mm in the 2860/2871 situation.

A/R does soften transient response, if you're well above boost threshold you can feel it a bit during a gearchange but that's about it. The bigger effect of a/r is what it does to threshold and backpressure.

It is really hard to look at any one of these factors in isolation. There are many interactions. Even a detailed spreadsheet match involves a lot of assumptions and hand waving esp when it comes to transient effects. You really have to model the system to analyze those effects, and who has the money/resources to do that aside from OEMs.

The new GTX3071R turbo looks great from SEMA show!

I wonder the same thing..which turbo is best fit for 1.9L built motor for over 300HP.

I once read this article 10 years ago about a guy building a turbo fox body to run some flying mile competition in Nevada? Anyways he was pushing say 600whp on say 8psi. He explained that he prefered to build the motor as efficient as possible to be able to run the lowest boost to achieve his power goal. He made an example of a stock motor would gain 20whp per psi and he had a delta of 400whp to gain so boost would be 20psi. He then compared that to the built motor making 400whp and boost gain per psi was say 25whp. The delta was now 200whp or 8psi. He spoke about the cost to build the motor was more than just running 20psi on a stock motor but that his low psi combo created less heat and had far superior reliablility. Does anyone have any graphs with built vs stock motors running the same psi? It would probably need higher comp, cams, head work, and intake to be a good comparision.

I believe this needs some sticky hustler/jessica alba nutting action.

lol, at the Xida thread. I also had a delicious sandwhich today made by a chick that looked just like Alba.

I'll scan GTX charts that I got from SEMA when I get home.