Help me pick a turbo

[AkursedX]

I have begun planning for my turbo-3800 that I hope to get done next fall/winter.

To put it plain and simple, I am turbo-retarded. Compressor maps make no sense to me no matter how much I study them, so I need help for a proper turbo for my project.

I know I want to go with a Garrett GT-ball bearing Turbo.

Here's some info for to help with proper sizing:
-Goal of 350rwhp that's streetable (94 octane and no rediculous turbo lag)
-I think I will go with these cam specs: Duration @ .050" is 212/212. Lift is .520/.520 with 1.6 rockers. Lobe separation is 113 degrees with around a 6300rpm shift points
-The rest of the engine will be built as well ARP bolts and studs, ported heads, upgraded valvetrain, etc.
-I will also keep the shortstack intercooler I have (just use a gutted M90 with a blockoff plate)

From what I can tell, it seems to me that a properly tuned GT35r will be able to meet my goals, but I'm not sure what kind of a/r I should be looking to get.

Any help would be greatly appreciated.

[Shaun41178(2)]

if your goal is 350 whp then a 35R would work. Don't know why you are set at only 350whp though

37R might be a bit better.

If you don't want much lag then a .63 exh housing would work well, but it will spool up hella fast on a 3800. Might make low rpm take offs even challenging without breaking the tires loose at wot. .63 exh housing should be good for about 500 hp or so.

Lag is highly overrated though man. Its not as bad as everyone else makes it out to be. The car will still be faster then a non turbo even when you aren't making any boost yet. Its just when the boost kicks in when the fun begins. Going super huge of course is not good, but with a 3800, almost anything under a gt45 will have minimum lag.

My setup makes 7 psi by 2600 rpm running on about 5 cylinders through intercooler pipes and intercooler itself with a .63 exh, 3 inch downpipe with a 35R turbo sans ballbearings. If that helps at all.

[AkursedX]

if your goal is 350 whp then a 35R would work. Don't know why you are set at only 350whp though

37R might be a bit better.

If you don't want much lag then a .63 exh housing would work well, but it will spool up hella fast on a 3800. Might make low rpm take offs even challenging without breaking the tires loose at wot. .63 exh housing should be good for about 500 hp or so.

Lag is highly overrated though man. Its not as bad as everyone else makes it out to be. The car will still be faster then a non turbo even when you aren't making any boost yet. Its just when the boost kicks in when the fun begins. Going super huge of course is not good, but with a 3800, almost anything under a gt45 will have minimum lag.

My setup makes 7 psi by 2600 rpm running on about 5 cylinders through intercooler pipes and intercooler itself with a .63 exh, 3 inch downpipe with a 35R turbo sans ballbearings. If that helps at all.

350whp is pretty much my goal because I feel it's a output level that is high enough to smoke the majority of cars out there, but is low enough that I won't be breaking things like axles, trannies etc.....My goal for this car isn't an allout racer, I'm big on driveability, reliability, and overall performance.

I really don't expect a lot of lag with a 3800, nor do I want instant boost. I would like to be well into boost by 2500-3000rpm and be able to carry is effieicently to about 6300.

As for a .63a/r, that does seem to me like it would spool up fast with a 3800, I believe they make a GT35r with a.82a/r housing. Would this take longer to spool? Would it take too long to spool?

Most of the info that I this off of is what I found on garrett's turbo comparison page http://www.turbobygarrett.com/turbobyga ... _sheet.htm

[Shaun41178(2)]

Give me a day or two, and I will plot some compressor maps for you.

[Kohburn]

http://www.squirrelpf.com/~turbocalc/beta/

http://www.turboneticsinc.com/downloads ... Matrix.pdf

[txf]

Fierox runs a t-66 on his.

[eHoward]

You could plug 3800 data into this thing: http://www.howard.saturnet.net/turboInf ... rkbook.xls

[AkursedX]

Here's a couple of maps that I plotted thatnks to the link Kohburn provided:

Here's the data that I entered:
Target Power-450hp
Engine size-3.8 litres
Target a/f- 11.5:1 (I would like to be a tad on the rich side)
BSFC- .45 (This should probably be higher....)
Max I/C loss- 1.0 psi (???)

Engine redline-6300 RPM v/e-80% (???) Intake temp-130
Peak power-5700rpm v/e-85%(???) Intake temp-120
Max Boost-3200rpm v/e-88% (???) Intake temp-110
Min Boost-2200rpm (not sure about that one) v/e-86% (???) Intake temp-85

Here's a GT3582R Map with those specs:


http://www.squirrelpf.com/~turbocalc/be ... duct_id=42

Here's a GT3782R Map

http://www.squirrelpf.com/~turbocalc/be ... duct_id=44

Seems like both would work. From what I know (Which isn't much) the GT37 map looks better[/url]

[Aaron]

Here's a couple of maps that I plotted thatnks to the link Kohburn provided:

Here's the data that I entered:
Target Power-450hp
Engine size-3.8 litres
Target a/f- 11.5:1 (I would like to be a tad on the rich side)
BSFC- .45 (This should probably be higher....)
Max I/C loss- 1.0 psi (???)

Engine redline-6300 RPM v/e-80% (???) Intake temp-130
Peak power-5700rpm v/e-85%(???) Intake temp-120
Max Boost-3200rpm v/e-88% (???) Intake temp-110
Min Boost-2200rpm (not sure about that one) v/e-86% (???) Intake temp-85

If those maps/inputs are correct, I like the GT35r better.

Your I/C loss hopefully won't be anywhere near 1psi, that isn't very good. Mine loses .1psi at 15psi, but it is an A/W so it is much smaller than an A/A. If I understand your setup correctly, you are using a sandwich type A:W intercooler that fits between the blower housing and LIM. If this be the case, lower your intercooler pressure loss to .1psi (Even that's optimistic).

Your V/E should be highest at peak power, and I'd say on a 3800 you won't see more than 85% without heads/cam. So I'd plugin 85% at peak power RPM, and 80% at max boost rpm, and 70% at minimum boost rpm. At those lower RPMs, the engine's VE is truly pathetic (Any engine). I'd be shocked if they even hit 70.

As for the intake temps, I think you are also aiming a bit high. A good, well designed and implemented intercooler should be able to get the air back to ambient. Unfortunately, with the very low pressure loss of this IC, comes a disadvantage to the adiabatic properties, and you'll probably see higher than ambient IATs, even with that amazing turbo. With a properly sized DBB turbocharger, you should see near maximum A/E throughout a good majority of the rev range, dare I say 4000-6000. Even with the less than ideal intercooler, I'd guess IATs at the following (Assuming 80* ambient):

redline: 100*
peak power: 90*
max boost: 95*
min boost: 85*

I could be off on some of these, it is merely educated guessing. If I had to blindly suggest a unit, I'd say GT35r all the way.

[The Dark Side of Will]

You'll see max VE at peak TORQUE RPM, not peak power.

I think Aaron's VE estimates (and those of your program) are high.

I think your intake temp estimates are a good starting point.

The only intercooler that will be able to get the intake air temp back to ambient is one with 100% or greater efficiency (read: AWIC with water below ambient air temp... ice).

[AkursedX]

Ok, I lowered the V/E's
72%@6300
76%@5700
80%@3200 (closest to peak torque)
78%@2200

I also changed intercooler loss to .2.

Here's the GT3582R
http://www.squirrelpf.com/~turbocalc/be ... duct_id=42

Here's the GT3782R
http://www.squirrelpf.com/~turbocalc/be ... duct_id=42

[Aaron]

Thanks for the corrections Will, it's been a while.

Looking at the new graphs, I still like the 35r better. It is plenty big enough for your power goals, and will still provide quick spool and great response.

[AkursedX]

Resurrecting this from the dead:

Ok, I want this turbo:
http://www.atpturbo.com/Merchant2/merch ... y_Code=GRT

Now, what a/r should I get? And what kind of housing would be optimal for a 3800 install? I know I want an external w/g, so that cuts out a couple of housings.

Goal is ~400whp.

[Aaron]

That's really weird, the GT35r has mainly T3 tubines now. I thought it was T4 only. I have the same basic turbo (GT35r) and am using a T4 turbine with a 3" V-band discharge, I'm not sure on the A/R, but I want to say .82. My goal is about 420whp.

I'd go with the .82 T04 turbine, with a 3" V-band discharge. Your's will naturally spool the same turbo faster than my engine will, and I'm expecting full boost at 3500rpm. With your low end flow advantage, I'd expect you to spool 500-1000rpm quicker, and the 35r will be more than capable of 400whp whilst still staying efficient.

Even if you don't go with the T4 style turbine, you want the V-band discharge for sure. It makes it really easy to work with.

[Shaun41178(2)]

I agree with aaron to4 .82 housing would work good for a 3800. Still spool quick, but won't choke off up top.

Either that or the T3 with a 1.06 or whatever the largest one is.

I am glad to see this link to ATP. I have sort of forgotten about them and I plan to upgrade the turbo on my new setup with the DOHC motor and I would need a internally gated 35R option. Its good to see ATP has that option for me.

I really think the T4 exh is best in case you want to go larger one day to like a 4088 or a 42R or something, it will just be a bolt on affair.

[Aaron]

I have sort of forgotten about them and I plan to upgrade the turbo on my new setup with the DOHC motor and I would need a internally gated 35R option. Its good to see ATP has that option for me.

Why would you buy such an amazing turbo just to use a very inferior wastegate option?

[Shaun41178(2)]

Because if I am not mistaken the current setup is internally gated. its much easier for me to stay internally gated because then I can keep the same DP and whole exhaust system. Not to mention I wouldnt' have to cut the crossover, and weld up flanges and buy an external wastegate and route the dumptube.

Its just convenience more then anything else.

[Kohburn]

ps. shaun i'm still selling that polished turbonetics T-62 (t3/t4 internal wastegate hybrid) that i bought to bolt in place of the old t04e

its properly sized for a goal of 400-500hp.