TURBO SIZING for us noobys..

77amc · Post by **77amc** » Fri Oct 10, 2008 7:58 am

I've been really trying to understand all this new terminology since getting into turbos but this is really getting me cornfused..

Could someone print up or tell how the heck one looks up the size for a turbo and can adapt it toward an application??
I mean, I have a couple IHI turbos that are tiny in intake and exhaust ports compared to the quest/talon ones that I have but when I read that XX is too small, you should be running a ZXZ..

NOW I'm not talking of trim. Just the size of them. Is a T-3 bigger or smaller than a T-4?It there a T-2 or a T5/6? A t25 smaller than a gt28r?? (Sorry if i get them mixed up)

How can I just look at a model name ( and be able to tell if it's bigger than a Holeset or what..
Even if I call up some place like Turbo City. I'd still like to know what to what the heck they're talking about.
It's like telling me "Oh, you have a 4.1L.. Not a 6.6L.. C'mon man!.. Don't you know?" Without seeing it and it's differences, it's just a number to me.

I think this would be a good sticky to. Maybe take a poll on it for other Nooby's

Errol

peregrine · Post by **peregrine** » Sat Oct 11, 2008 11:14 am

just get a gt35r for 800 wheel horsepower

77amc · Post by **77amc** » Sun Oct 12, 2008 2:55 am

HELL YEAH!! GIT R DONE!!

Not to jack myown thread but would you guys think that an Eclipse turbo for each bank of a cheby 327 oldschool be too quick to spool for just street driving?
I've always wanted to build a 327 or a 300 (bored out 283) for thier high revs, and since I have a couple of turbos...

Thanks for the link also

Errol

peregrine · Post by **peregrine** » Sun Oct 12, 2008 12:32 pm

i think twin 20gs would be the minimum size on a small block. might be able to get away with 16gs but not 14bs.

jeffball610 · Post by **jeffball610** » Sun Oct 12, 2008 9:03 pm

When choosing a turbo setup for any engine, you need to know its air flow requirements. You would think twin 16g's could put down almost 800hp since one can make nearly 400hp on the 2.0L 4G63. But then you have to consider the flow characteristics of the other engine, etc. etc. etc.

You can get a rough idea of how much "turbo" you'll need by looking at similar setups and reading compressor maps and stuff. It's all really confusing to me and I just stick to what others are using or something very similar. I always thought the Greddy twin turbo setup for the 350Z had way too big of turbos. I think they run twin 18g's and only puts out like 400-450hp. I don't get it.

You might also consider things like what purpose these turbos will have (drag, road race, street etc) and how quickly you need them to spool. Packaging and price might also come into consideration when choosing a turbo.

My advice is to contact a good shop that works with your motor or application and see what they recommend. A lot of shops will give free advice. You can also visit some forums to see what successful guys are using on there cars. But whatever you do, please educate yourself on your turbo selections as much as you can. Matt's link is a good source for Garrett turbos, but there are a thousand different turbo combinations. Each one with different flow characteristics and power potential.

Just for reference I'm running a SBR (Slowboy Racing) GT11. The numbers mean almost nothing in this case. It's a Mitsu TD05H turbine housing with a Garrett ball bearing center section. (the GT part) It then has a 52 trim compressor wheel that's good for about 50 lbs/min. However, due to the more restrictive Mitsu housing the turbo has only put down about 425hp on a DSM. (not mine) Hope that helps confuse you.

peregrine · Post by **peregrine** » Mon Oct 13, 2008 10:51 am

mattmartindrift wrote:
77amc wrote:HELL YEAH!! GIT R DONE!!

Not to jack myown thread but would you guys think that an Eclipse turbo for each bank of a cheby 327 oldschool be too quick to spool for just street driving?
I've always wanted to build a 327 or a 300 (bored out 283) for thier high revs, and since I have a couple of turbos...

Thanks for the link also

Errol

I'd prefer a ball-bearing setup almost always.

GT28R comes on S15 Nissan Silvias and is a great turbo for that size engine.

Also, a GT2871R would do well too.

It all depends on the power you'd like to make at what boost level.

Small turbos will generally give better lower-end response; response would also be improved by adding a ball-bearing turbo(s) to that equation.

However, with a V8, I think the simplest, cheapest method is to go with one large turbo and a cross-over/up pipe style exhaust plumbing.

Somthing like a GT35R or GT40R would fit the bill nicely and make an easy 550- +600hp.

t67 is usually the smllest youd want to go on a single v8 setup. so a gt40 would be just about right.

peregrine · Post by **peregrine** » Tue Oct 14, 2008 12:07 pm

mattmartindrift wrote:haha, you and I race in different worlds.

I think a GT35R would be a great low-boost turbo for a road-race-style application.

yeah when i think racing its always drag. a gt 35 would run out of steam quick even on a 4.6.

Robert Venable · Post by **Robert Venable** » Wed Oct 22, 2008 12:34 am

I guess this is as good a place as any to ask this question.

Is there any special formulas for twin turbo set ups?? Do you simply divide the air requirements by two?? What about compound, sequential, etc. turbo setups?? Any special formulas? Anyone know or know how I can find out??

Post by **DJpowerHaus** » Fri Oct 24, 2008 9:22 pm

I've been looking at some of the maps in some of the compounding / sequential / etc. setups that Holset / Cummins does, and I've yet to figure out how it works.

In my opinion, the cost of a 2nd turbo and a custom manifold would be more than the cost of getting one nice turbo and a good tune to spool it faster.

Robert Venable · Post by **Robert Venable** » Sat Oct 25, 2008 3:00 am

Can you provide any links to the maps you found?? While you are looking at those-- have you (or anyone) found any maps on Variable turbos like Honeywell's VNT series??

I'm just looking into this because I'm trying to make a 2.4L 4 cyl, with about 8-9:1 compression, have a TORQUE curve similar to BMW's N54 (which is a Direct injection, 3.0L 6cyl Twin turbo with 10.2:1 that uses less than 10psi of boost at sea level). The N54 is able to have almost instant peak torque (300 ft lbs at 1400-5000 rpms) threw the use of it's high compression, direct injection, and (of course) very small twin turbo setup.

Now I know that it would be almost impossible for my to realistically duplicate this kind of power, but I would like to have at least 250-300 ft lbs of torque at 3-3500 rpms. From what I have calculated, this would require 171 hp at 3000 rpm to 200 hp at 3500 rpms for 300 ft lbs. From the formula's I've found on the net(which vary widely so I'm not sure how much I trust them) 200hp/300ft.lbs at 3500 would require 22 lb/min and even 143hp/250 ftlbs at 3000 would require 15.7 lb/min.

Considering I'd like to stay bellow 20 psi (would prefer between 10-15 psi actually), this would be a very tall order for a single turbo to operate efficiently in, even if only rev to 6500 rpm, thats still around 34.1 lb.min if I'm still making about 250 ft lbs and 310 hp.

Not many turbos that I'm finding are able to efficently stay in this range-- this is why I was considering twins.