Need help deciding on turbo and a/r ratio plz...

[Mahonroy]

Hello, I have been doing some research on different turbos, a/r ratios, reading up on compressor maps through maximum boost, etc. but there was still some things I am having a hard time figuring out...

So right now I am under the impression that I am using a mitsubishi TD04 15t turbo, I have no clue what the a/r ratio is, but its maximum efficiency is around 15psi supposedly, which nets about 240whp or so.

With that turbo the boost comes on really quick, and it seems to pull the hardest between 3000 to 4000 rpm's then the acceleration rate kind of dies down a bit.

So anyways what I want is a turbo that can support 400whp or so, but has most of the pull in the higher rpm's, which generally meens a higher a/r ratio. How high of an a/r ratio is what I am confused about. Basically I need help desiding how big of a turbo I need (how much it can flow PSI wise), and then what kind of a/r ratio I would need as well.

I know that a small turbo with a high a/r ratio will net the same hp as a larger turbo with a smaller a/r ratio.

I also know that generally for daily driving, a lower a/r ratio is best, and a larger a/r ratio is best for racing, but I deffinetly would personally enjoy a higher a/r ratio I believe.

So originally I was thinking a Garrett GT2871r turbo, I believe that if I weant with an a/r ratio such as .64 then it would perform around the same as my current turbo, only it can support more flow (and more psi of pressure), and the ovious part that its ball berring as well so...

I believe the limit on the a/r ratio is .81 and .86 for that turbo, but I don't know if that would be too high....

Also, lets say you have a GT2871r, one with a .64, and another with a .86, if I have my boost controller set to 17psi, the .86 will spool slower but yield higher HP than the .64 right? Does the higher a/r allow it to boost more than the a lower a/r or do they both boost the same its just a different shaped graph?

Also I was reading people having problems with getting the GT2871r to boost more than 17psi for some reason, wasn't sure whats up with that.

So basically I was originally planning on going with the GT2871r and going with an a/r ratio of around .75 or .81 and running like 25psi. The internals of the engine will be built so it should be fine, and yield around the power that I want, but would like to be able to figure out a more definitive answer on exactly what I need...

Also one last question, so an engine can only handle so much power before it breaks. Is this directly proportional on the amount of HP it dyno's? Basically my question is that if I am running 17psi on a .64 a/r ratio, compared to 17psi on a .86 ratio, the .86 ratio is going to dyno much more horsepower than the .64. Does that meen that the .86 is also putting more stress on the engine compared to the .64 ?

Thanks for reading all of my questions! If anyone can give me some help/advice on all these questions I would be very appreaciative!

-Matt

[thewilson]

I have a friend with an evo VIII and he is going to be going up to a GT28 i am thinking its the same turbo as GT2871r? Anyhoo I was asking why go up so high wouldn't the lag kill you well the t28 spools up at 3k rpm and then will keep going as the stock spools up faster but tops out so yeah more power less off the line power Thats my .02cents on that. far as a/r i found on a saab forum that after the TD04-15T if there is a xxcm2 the cm2 converted over is

6 cm2 = 0.41 A/R
7 cm2 = 0.49 A/R
8 cm2 = 0.57 A/R
9 cm2 = 0.65 A/R
10 cm2 = 0.73 A/R
11 cm2 = 0.81 A/R
12 cm2 = 0.89 A/R

thanks to the saab thread i read (http://saabnet.com/tsn/bb/performance/index.html?bID=96429)

[mayollo072R]

T-25 and T-28 will not work for you This two are intended for quick aceleration. You must use Must use A/R .48 (spools fast) or A/R .63 (spools at 2800rpm or so) with stage stage 3 wheel. Those A/R mentioned are for the hot side (turbine). Trim level must not exceed .57 or lower than .51. If you want from 175 to 250 whp use T.25 or t-28 (a ball bearing GT-28 will work for a lot of power but it is very $$$$$) For this cars you can use a floating bearing turbo T3 or T3/T4. This two will give you the more power by PSI compared to the small turbos on which you will need to increase your psi to risky ones to obtain the desired amount of power plus you will be loosing traction very fast.

My recomendation for you

T3 with AR.50 cold and AR .48 (.63 is acceptable too) hot. The trim must be around 50 or more wheel must be stage 2 or 3.

T3/ T4 are good also with this specs A/R .60 cold and A/r .63 or .48 hot with stage 3 wheel and from 54. to 57 trim. but this setup need s an external wg to be perfect.

Just remember the bigger the A/R, the more load you will need to spool the turbine and viceversa. Same goes for the wheel stage, the higher the stage the bigger load you need.

Never exceed the a/r in this cars for more than .63 on the turbine side or you will meet lag city. The same goes for the whell stage no more than stage 3.

[Mahonroy]

Ok here is what I came up with so far, let me know what you guys think:

So basically I did some calculations, here are my goals first:

* 350 wheel horsepower (approx. 407 at the crank) at 6400rpm's
* After everything is working properly then upping it to 400 wheel horsepower (approx. 465 at the crank) at 6400rpm's

First, calculate the flow of the engine at naturally asperated state (no turbo):

N/A Airflow rate (cfm) = (engineCID * RPM * 0.5 * volumetricefficiency) / 1728
N/A Airflow rate (cfm) = (122 * 6400 * 0.5 * 0.85) / 1728
N/A Airflow rate (cfm) = 192.037

So the stock engine is 120 at the wheels (138 at the crank), so to get approx. 350 at the wheels:

Power gain ratio = desired power / original power
Power gain ratio = 350 / 120
Power gain ratio = 2.91667

So the required airflow I am going to need is this:

Required Airflow (cfm) = N/A Airflow rate (cfm) * Power gain ratio
Turbo Required Airflow (cfm) = 560.109


So now the approx. amount of boost I am going to need:

Pressure ratio = (14.7 + boost) / (14.7)
2.91667 = (14.7 + boost) / (14.7)
Boost (psi) = 28

And here is the calculations done for every RPM at 200rpm intervals:

rpm cfm lbs/min
6400 560.11 40.79
6200 542.61 39.52
6000 525.10 38.24
5800 507.60 36.97
5600 490.09 35.70
5400 472.59 34.42
5200 455.09 33.15
5000 437.58 31.87
4800 420.08 30.60
4600 402.58 29.32
4400 385.07 28.05
4200 367.57 26.77
4000 350.07 25.50
3800 332.56 24.22
3600 315.06 22.95
3400 297.56 21.67
3200 280.05 20.40
3000 262.55 19.12
2800 245.05 17.85
2600 227.54 16.57
2400 210.04 15.30
2200 192.54 14.02
2000 175.03 12.75
1800 157.53 11.47
1600 140.02 10.20
1400 122.52 8.92
1200 105.02 7.65
1000 87.51 6.37
800 70.01 5.10
600 52.51 3.82
400 35.00 2.55
200 17.50 1.27
0 0.00 0.00

From looking at a graph for determining approx. turbine size from Maximum Boost, I get that the Bore(in.) should be between 2.25" and 2.75" (57mm to 70mm) and that he always chooses the larger of the 2.

So now what I was doing was looking these numbers up on compressor maps, take this one for example: GT2871R - 743347 - 2 (http://www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT28/GT2871R_743347_2.htm)

http://www.jattus.com/dump/gt2871rcmap1.jpg

You can see that its off the chart. I had done one earlier with 20psi, which is 453.311 cfm, or 33.02 lbs/min that it lies right in the efficiency range and is a good choice for that amount of boost, though that nets 288 whp (325 at the crank).

So here is the other graph they have:

http://www.jattus.com/dump/gt2871rcmap2.jpg

I am a little confused how you are supposed to use this correction. Because one of the versions has a higher A/R ratio, it should allow the ability to flow more at the same psi's. So basically I could get the desired power with less psi on the higher A/R ratio, but I am a little confused on how to figure this graph into the compressor map graph, to see where it would lay on the graph...

But anyways, so yeah before I figured the a/r ratio, it seems the 0.64 a/r ratio wouldn't be enough to support what I need (though I don't even know if a larger turbo would fit...?) so take this turbo for example, GT3071R - 700382 - 20 (http://www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT30/GT3071R_700382_20.htm):

http://www.jattus.com/dump/gt3071rcmap1.jpg

It seems like it has enough to flow the desired CFM's, this one for example only comes with a .86 a/r ratio. But then again, I would need a different exhaust manifold flange assuming that it would fit in the engine bay right?

So anyways...what do you guys think about all this?

[TSmooth8403]

i'll take t3/t4 for the win!! LOL

[Munky]

That made absolutely no sense to me.

God thing I don't plan on getting a turbo.

[BColeman]

You are asking for suggestions so here goes:

Order up one of 2 things like Mayollo said:

1) Garrett T3 Super 60-1 (.60/.48)

OR

2) Garrett T3/T4 TD04E, make sure it's the E (.60/.63)


1) Full boost by about 2800 RPM's and it pulls till Red Line, though you need to be prepared to add quite a bit of fuel.

2) Full boost by 3300 RPM, though fuel tuning is still required, not as much in the higher RPM's for some reason.

The only difference between these 2 turbo's besides A/R is the Compressor side of the turbo, it's larger on the T3/T4. Both turbos are rated for 350-400 whp and both turbos operating range are between 15 and 25 psi.

Both turbos would be great for your application. Both have been tested on the CVVT XD2, and both yielded great results. The only problem we've run into is with the fuel tuning. The 290cc injectors are too small, and anything bigger without a fuel pressure regulator and a return line would be pointless. We've hit the "brick wall" in testing so far. We are having to add the fuel pressure regulator, return line, and 440cc injectors to properly tune the AFR to 11.5 to reach maximum HP in the upper RPM band.

[Mahonroy]

I have everything w/ the fuel taken care of. I have a fuelpressure regulator and running a return line back to the gas tank, as well as a walbro 190. Also either using 4x 290cc's and 4x 440cc's(sub injectors). Or going to go with just the 4x 440cc's and a 5th and 6th injector (so 2x 650cc's). Either way should be plenty of fuel.

Did you have both of those turbos on your elantra? What kind of turbo exhaust manifold were you using? I don't think either of those will bolt up to mine (I am pretty sure mine is a T25 flange?) so if I wanted to go with those I would have to buy a new manifold...?

[BColeman]

The testing is being done on struck1181's XD2.

As far as manifolds, we are actually switching to an Evolution VIII turbo manifold that Frank at Xtreme Boost was using on his EVO VIII. It's tubular, with longer runners and has a T3 flange.

If you have a T25 flange, there shouldn't be any problem. Just have a shop cut the flange off and re-weld on a T3 flange. You can find the flanges on eBay. Sometimes, when you order the turbo's, the flanges come with them. I can get you a T3 Super 60-1 here in Orlando for less than $500, if you are interested.

Next, your fuel. 4x290cc and 4x440cc would be overkill. You won't even need a 5th injector if you do the following.

1) 4 x 440cc injectors, NGM has them for $575, or you can shop around.
2) RRFPR (rising rate fuel pressure regulator) at 1:1, for every 1 psi of boost, the fuel will increase 1 psi of pressure.
3) Return line, self explainatory
4) SAFC, or Greddy e-Manage for fuel tuning. I'd pick the S-AFC becase it's easier to tune, you don't need a laptop and all that. You'll be able to fine tune the fuel at WOT, under boost, and for idle.

In the next couple of weeks, I'll have more information.

[evan938]

and i have found on ebay you can find adapter plates to go from a small flange to large turbo for pretty cheap. i want to say under 30$

[Mahonroy]

hmmm, maybe I will just cut off the flange and weld on whatever I want. Also I have some exhaust manifold flanges on the way, maybe I will experiment with making a top mount turbo manifold w/ a new smaller radiator...

I already have a fuel setup (and already have NGM's 440 injectors), the fuel pressure regulator is basically a RRFPR set to 1:1, just to keep the fuel pressure constant instead of it dropping 1 psi for every psi of boost. I am using the unichip with 290cc's and a 5th 650cc at the moment, I am just upping the fuel a bit more is all.

So how are you using an Evo 8 manifold? Are you drilling new holes in the manifold so it will bolt up to the beta engine?