turbo upgrade between t04e and gt35r?

[Gollum]

the gtX35r will spool about as early as the gt30r, but with the flow more like the gt35r. The gtX30r will spool more like a gt28/5r.

 

Each generation of turbo generally spools faster for a given flow amount. Obviously that's a large generalization, but when you compare a turbo from the 70's as found on some turbo production cars from the era, the difference is quite obvious. Today's modern ball bearing turbos share very little in common from their older brethren. Different turbine designs with better exit flow paths, better compressor wheels with computer modeled wheels, anti-surge porting, etc.

 

The down side is mainly that the newest turbos cost more. Also consider that just because a newer turbo might be "better" that doesn't make it "right" for any application in it's power range. It's always about a properly designed system.

 

I plan to run something more like a T72, but that's because I'm cheap and I also don't exactly want it to spool instantly at lower RPM.

[Koryu]

I understand that I I think maybe you wanna say the gtx30r spools like a gt30r and flows like a gt35r?. I saw that big phil was experiencing surge problems with that turbo and some would say it was his intercooling piping or his wastegate setup, but I have seen the compressor map against the flow of l28et and that shows surging would occur also. That's why I was looking at the gtx3076r because it looked better on the compressor map and would still get me to power I'm looking for. If someone could post the 2 compressor maps against the l28et, then you guys would see what I mean. The t04e 50 trim plots perfectly but I just wanted alittle more room to grow which is why I was thinking gtx3076r.

[Tony D]

Big Phil had issues from mismatching components, and running the "Maximum Boost Mentality"

Had that system been more thought out and not pay as you go and see what happens many of those issues would not have been present.

 

He had a stock head an slapped a high flow turbo on it...you're gonna have issues!

[Koryu]

I agree with you Tony and that's what I'm saying about that turbo on a stock l28. The gtx30r map seems less likely to surge while getting close to the same flow as a gt35r. The gtx35r is on another level and the compressor map shifts a little to the right verses the gt35r so seems a little more surge prone then the gt35r. I know there is data for airflow for a stock l28et vs gt turbos and I'm going of that data. The hard part for me is I don't know how far to the right I will shift on the map by a port and polish and a matching can upgrade. But I can guess a little and with the gtx30r I can safely assume I would be safe. I would have loved to seen dyno numbers after big Phil swapped to his ported head and can change and see if the surging went away...

[240Z Turbo]

Here is a back to back of the GTX3076r(green) vs the GTX3576r(red) on my EVO IX, which is a 2L.  The turbine housing used for this data is the ATP 1.06 a/r T4 TS units and these results are on 93octane.  You can see the larger turbine wheel resulted in no lose in spool and an increase in hp at the top.

 

Edited November 5, 2013 by 240Z Turbo

[Koryu]

I've actually read that thread and others like it in my research. I see your point in this instance about the 2 turbos although I have heard the response was better on the gtx30r. It remains to be seen in this instance however. My main point again is flow characteristics against the l28et and the maps show the 35r to be more demanding and more prone to surge than the 30r. That's why I'm matching the turbo to the output I want without mismatching it. The 4g63 has completely different flow characteristics than a l28et hands down but I do understand the turbos spool the same but the 35r makes more power however I don't see why the gtx3076r can't get me 400-450 whp while matching the l28et better.

[Tony D]

Read the "What is Surge" thread?

 

Surge is ALWAYS a manifestation of too little flow at a given pressure.

 

If the head can not flow what the turbo puts out at minimum rpms (waste gate open fully) then pressure rises and you surge.

 

As discussed in that thread a PID controller on a valve dumping to atmosphere with an RPM-Based function could release flow, keeping the compressor out of surge.

 

Combine with a flat shift / prespool scenario along with a proper surge map and you could run the turbo at maximum pressure offset 1 or 2% from the surge line all the way up through the entire rpm range.

[Koryu]

True... or I could also run a turbo that fits my power needs that has a compressor map that better matches the flow of a l28et and shows no signs of surge. I like that idea tony, and I like how you gave an example of how to run this turbo without surging but I like to keep things simple. Simple is best.

[Chris83zxt]

True... or I could also run a turbo that fits my power needs that has a compressor map that better matches the flow of a l28et and shows no signs of surge. I like that idea tony, and I like how you gave an example of how to run this turbo without surging but I like to keep things simple. Simple is best.

 

I defer to the more experienced people but it seems logical to me to choose a turbo with efficiency islands that you know will fit your motor well instead of living mostly on the edge and then maybe coming into an efficient area at high rpm/boost levels.  I can't see any reason to get a ridiculously large turbo unless you're just building a dyno queen and shooting for the largest number attainable.

[Koryu]

That's my thought on it as well ..

[Gollum]

I can't see any reason to get a ridiculously large turbo unless you're just building a dyno queen and shooting for the largest number attainable.

 

Ridiculously large is a relative statement though. Is a T72 small? Some diesel applications will use a T72 as a SMALL turbo to spool a larger one...

 

Now, if we want to talk about engine displacement that still doesn't exactly hold true. A ford 5.0 (more like 4.9 in all reality) won't handle twin T3 turbos very well without some mild flow modifications. Half that 5 liter and we're looking at each turbo having roughly 2.4/5 liters to work with. Put a T3 on a Honda K20A (civic type R 07+) and it's going to run out of breath. So displacement can't really tell us what turbo to run either.

 

If we go by just HP in NA trim, we won't be far off from most guess when picking a turbo. In the above example, the ford engine makes a conservative 225hp, and let's just ASSuME that it's making 250. Heck, maybe someone put a cam in it. That's still a whopping 125hp worth of air per turbo. That's not even a stock B16... Hell, many honda D engines do better... The K20A in question makes well over 200hp stock, 222 to be exact. So here's an engine that's about the same overall airflow as the 302 is stock. Hmm... So in that light putting two T3's on a stock ford 302 is kind of like putting two T3's on a stock Honda Civic Type R. People would call that stupid on a honda, yet nobody is going to ask the mustang owner with two T3's "hey, what mods do you have to support the added airflow of those turbos?"

 

See where I'm going with this?

 

A stock L28 isn't going to handle a GT40xxR

A stock L28 might not even like a GT35xxR much

A stock L28ET longblock tends to make peak HP between 5,000 and 5,500

Most people won't push their L28ET past 7500rpm

 

Now, a stock L28E, which is basically a turbo motor, minus the turbo, with added compression makes a whopping 143hp. That's not much air.

Now, how many here have 200+ hp NA L engines?

How many here make 250+?

How many make 300+?

 

If you're running a 300 crank HP NA L engine, you can effectively be running TWICE the turbo as a stock L28ET.... hmmmmm

 

All of the sudden even a GT45 doesn't seem that big...

[Koryu]

Interesting..... I see that, but to get to said 300hp na engine would require lots of money and high compression which would likely be detenation prone. I'm talking about actually data of l28et airflow against given turbo compressor maps to find a matching turbo for your goals. Yes I can run a gt35r or a gt40r or bigger with the right mods and money. However I will be running a stock shortblock just looking for 400 whp or so and using tools like compressor maps and airflow data to match a turbo to my needs while maintaining efficiency. I know about the gt35r, great turbo, not denying that. Just looking at a t3/t4 50 trim and a gt35r and wondering if the gtx3076r would be a great turbo between the 2. It looks good on paper to me, but was looking for examples of someone who ran it or if they researched it to and have came to the conclusions I have is all. The gtx3076r seems like a good match for the l28et in the 400whp range with some room to grow.

[Gollum]

Which shows that you're already way ahead of the game compared to some others.

 

I have a feeling trying to reach 400whp with that turbo on a stock longblock will be a real challenge. I think it's much more realistic to expect 300-350whp on a stock head, and then shoot for 400 after some mild headwork.

 

This is why I say this:

 

If you're in the typical 130-150 wheel torque @ peak HP of 5000-5500 without the turbo then you're asking for a BIG increase. You're asking to go from 130ish whp to 400whp. That's THREE TIMES the stock HP level. In a perfect world that means shoot for 3 BAR (pressure ratio, 2 BAR boost), but you'll likely need more like 3.4 BAR (again, P/R) due to heat management power losses.

 

That GTX won't like running that high, period. Let me put up the GT versus GTX map for reference:

 

 

The map goes up to 3.5 BAR just fine, but it's area starts to get pretty thin, and efficiency will be out the window. This is NOT a turbo to use to reach 35+ psi. But if you do the supporting mods to bring off-turbo power up to around 170whp @ 6,000 RPM, your expected pressure ratio goes down to about 2.8-9 or around 29psi. Now that's MUCH more manageable with this turbo, and doesn't really take THAT much work. We're talking a decent intake (which you have planned), along with mild port work, a cam, and low restriction exhaust. 

 

By contrast, if you look at a turbo like the T61, it has a much more vertical map that's intended for high boost applications, as it's PEAK efficiency goes way up to 3 bar pressure ratio, and the map i shows the turbo will reach 3.8 bar just fine. But that turbo also doesn't want to flow past 55 lb/min, while there are other turbos of similar size that will reach much higher flow numbers at lower pressure ratios.

 

 

All that to say that turbo choice is never an easy subject if you only look into what is in a catalog or what other big box companies use. 

 

Also, last note of mine: 300hp for a L engine isn't THAT high. 400hp is attainable for the extremists out there, and the main thing even those 300hp engines have that most of us don't is called RPMs. You'd be amazed how easy detonation can be to control on some of these 250+ hp beasts when built and managed correctly. Detonation is most prominent at high load and lower RPMs, which is hardly a concern if your redline is 10k... Does it cost money? yes, of course. But my point in bringing that up is that getting to 200+ whp NA isn't THAT hard to do and would go a LONG way to reaching your 400whp goal on boost, and likely REDUCE how prone to detonation the engine is...

[Koryu]

I see the maps for the gtx3071r and I am looking at the gtx3076r. Looks a lot better than that. I plan on a good port and polish and custom turbo grind camshaft with a 3" exhaust all the way back. Combined with my new intake and a gtx3076r I would like to see 400whp. Especially on e85 if not 450 whp. Thank you for all your input, I like my eyes being opened up to other setups and getting more insight. The gtx3076r looks like it would flow close to what a regular gt35r would flow.

[Gollum]

For the sake of record, here's the CORRECT overlay:

 

 

There's certainly more flow area way up there at the 3.5 pressure ratio range, but if you look at the efficiency it's maximum at that pressure ratio is 71%, versus it's peak island area of 78% that only goes as high as about 2.45 pressure ratio.

 

Again, I hope you see that my goal is ONLY to educate, not tell you what to do or how to do it. I just like to make sure that people are thinking for themselves which tends to lead to more correct choices. And when you DO make a bad choice, you know what happened and how to fix it.

[Koryu]

I see that and I appreciate it that's why I ask these questions, to better educate myself. I learn something everyday. So what turbo are you thinking for my goal then gollum?? You don't think the gtx3076r will do it? Please share your turbo of choice for what I'm looking for.

[Koryu]

Here is a reg gt3076r with l28et flow. Looks good at the 2.5 bar. Now if I could only overlay the gtx map.

[Koryu]

I forgot to attach

[Gollum]

I'd look into the BorgWarner turbos. They tend to be VERY high boost application turbos. I'd consider the S256, which though maxing out around 550hp doesn't give up much efficiency in that HP range when running high boost levels. It's NOT a low boost 550hp turbo like you'd put on a V8, it's much happier on a smaller displacement Honda, or mid-efficiency mid-displacement engine like our 2.8.

 

Here's my projected overlay of what you'd most likely end up with, provided it spools as slow as I hope it would, which is a tough thing to predict from my chair here.

 

http://www.squirrelpf.com/turbocalc/index.php?version=4&target_peak_power=500&pr_ref=14.696&engine_disp=2.8&engine_disp_factor=0&target_af=12&bfsc=0.55&max_ic_loss=1.7&rpm_redline=7000&rpm_peak_power=6500&rpm_max_boost=3500&rpm_min_boost=2500&vol_1=74&vol_2=80&vol_3=81&vol_4=79&vol_1=74&vol_2=80&vol_3=81&vol_4=79&intake_temp_1=90&intake_temp_2=120&intake_temp_3=135&intake_temp_4=140&turbo_n=1&map_sel0=178

 

And that's assuming you've got about a 200 crank HP engine that peaks around 6500RPM, which I think is relatively accurate for what you say you're building. And that's also based on an assumption of having about 80% NA torque available by 2,000 RPM. For my calculations I've got VE of 82% at peak HP, 86% at peak TQ, and 72% at min boost. Oh, and the other vital data is assuming BSFC of around .55

 

That calculator is set to graph for 450 crank hp, but my gut tells me you'd make more crank HP then that at those PSI levels. I say that just from experience and from what I've see others achieve. I could be wrong, but I'm at least being honest.

[Tony D]

Wow, and to think a GT35 R makes a non-surging 400HP at under 10 psi with a cam and properly flowed head and no sign of surge...

 

Pressure is a manifestation of restriction to flow. If you decide you want to make a turd non-flowing engine make 400 HP, then yes, you will play around with turbos that likely won't work well at all.

 

If, on the other hand you choose to do the same thing you do to make power N/A.....that is, increase the FLOW CAPABILITY of the engine through porting and a cam, you are rewarded with picking properly sized turbos in the fat middle of their operational island, never going anywhere near the flow stagnation point pushing 3 - 4 bar of boost to "Make Corky Bell Power"...

 

The thing is, crank up that boost over 1 bar and your ignition starts getting problematic.

 

Personally, I like 400HP at 15-17psi. Look at the flow map of the turbo at that range.... nowhere near the surge line. And easy on the ignition system too... As I recall, I glanced at the dyno and saw 380 ft-lbs of torque at 4500 at 8.39psi of boost (wheels, on a Dynapack.)

 

You can force it in there---have at it. I'm not in that camp. I'm not from Texas and I'm not a Bell Engineering Groupie (save for their bypass valve, which is damn nice...)

 

I'll take mine from FLOW, thankyou very much. Compressors tolerate Stonewall FAR better than they tolerate Surge!