In a kinda follow-up to my last thread, here's what I came up with:

I know next to nothing about what this means, but by the maps, it looks like with 85% VE, a good sized turbo to run ~.8 bar (12 lbs) is the GT37 76mm, 52 trim, 0.54 A/R. It looks like it just fits the surge limit on the left side at 12 lbs at 3000 RPM flowing about 16 lb/min (a good number for the street I think) and leaves a little bit off to the right so that it's still in a good efficiency range at 12 lbs at 7000 RPM. At even 8000 RPM it's still got some more left to the right of the graph so it's not overspinning.

It's about 74% efficient at 3800 RPM (not bad..), doesn't really hit it's peak efficiency (77%) when only running 12 lbs, but that's a SMALL portion of the graph anyhow (take a look at it at www.turbosbygarrett.com on page 15). But it stays about 74% efficient right up until about 35 lbs/min @ 12 psi, which is about 6500 RPM. Then at 7000 RPM it's still fairly efficient. It doesn't hit 60% efficiency until about 8500 RPM (which I'll never hit with this motor).

Taking it up to 2 bar (14.7 psi) puts me in this situation:
At 3000 RPM it's away from the surge limit. Again, 3800 RPM makes for 74% efficiency, stays there until about 6200 RPM which is 37 lbs/min. And at redline has just left the 74% efficiency range.

As for the GT40 82mm 50 trim 0.58 A/R, it just BARELY misses the surge limit at 12 lbs at 3000 RPM, and at 4500 RPM it enters its peak efficiency range, and doesn't leave it until about 6100 RPM, so that by redline (7000 RPM) it's still over 76% efficient.

Help me out here.. Everyone says the GT40 is HUGE, but it doesn't seem THAT huge to me. It looks though like the first one I mentioned (GT37 76mm, 52 trim, 0.54 A/R) is a good choice.

 

Carx7, 87GTR, BDC, And I all came to the same conclusion, BUT when BDC/87GTR tried a Switzer S300(said to be the same size as a GT40, but un-divided) they found they could not spool it even with a Bridgeport. They have since switched to a T66 .96 ar(I am trying a T66 .81 on a street port, uninstalled). I think for 450-550+ the T66 is a good way to go. Go to www.moreboost.org, and you can compare all the wheel sizes and trims. These turbos are all very close in size, but they are totally different in the way that they behave. Another worth taking a look at is a PT67GTQ. See the website for info on that as well.
Carl Byck

 

Carl,

Eliminating the GT40R as an option because a Switzer S300 doesn't work is pretty poor logic. The T66 you mention has an even larger wheel that the GT40R, but you've practically stated the GT40R won't spool while the larger T66 will. I don't follow.

According to Garrett there are people using a ball-bearing GT40R now. GM NHRA Import

 

I was only repeating what BDC stated with regard to the size of a gt40, and a S300(the same). I do not know the specs on the S300, so I believed Brian to be accurate. I wonder what a GT40R is? Does the R denote BB? The previous GT40s were not available as a BB CHRA so far as I know.The GT40bb has been in an AU market Falcon for a year, but that does not mean I can buy one. Perhaps if I run a $1,000,000 race team garrett will just give me some Why don't you try one my freind? I was an advocate of this turbo until I was told that the S300, and the GT40 were the ssame size, and that a BP motor could not spool it til he top of second gear. If this is false, then I am still an advocate of the GT40.
As for the T66, we shall see. I have a .81 Qtrim in my possesion, but I need a different manifold, and I have to modify my DP first. I think it will be a nice combo. anyway, some one will get one someday, and then we will know

 

Bdc and 87GTR were having problems getting a smaller exhaust side, the s300 compressor side is perfect for a big HP 13b, in fact flow is similar to T66, maybe just a tad more, and the map is alot wider range than any Garrett based turbo..
I have taken up the s300 challenge, I am waiting for a 1.0 a/r housing to arrive any day now for my s300, the housing 87GTR had was a 1.15 a/r from a cummins with a big extended leg that had kick in it to get around the block of a 10 litre cummins which greatly increased the volume of the housing.. Also 87GTR's engine was a half bridge, I am going to try it on a full bridge, when you get deep down into the s300 family, you find that it is actually a cross for the TA45/Ta51 trubo's, which have been installed on all kinds of 13b's..(Marcell Burkett)...Max

 

I already have a GT series turbo! Trying the 40 would mean all new manifold and piping.

I don't think it's for big race teams only. Volkswagen Jetta from the Garrett site. ATP Turbo also lists it as a part of the GT-R lineup. I'm thinking the "R" means it uses the larger of the 2 compressor wheels?

 

I can find out, I actually know someone who has a GT40R sitting on his shelf. He said he didn't know anyone else withone, and also that he wasn't exacty sure what he wanted to do with it.

He did mention that the compressor wheel blades had been machined to a very sharp point along the leading edge, that it was easy to cut yourself on, and that it "looked" really mean... who knows how it works.

-Chris

 

This is a note I sent to precision regarding what I feel would be the proper sizing on the GT40. Basicly you can size a GT40 to be the ~same as a T66 which is proven. The advantage would be the new wheel, BB(maybe), all for far less than anyone sells a dual BB T66. Chris what are the specs on the GT40 your associate has? Tyson, are you saying ATP has a BB GT40 CHRA available?(I know I was supposed to call, but never did)? Here we go again GT40 GT40 GT40 GT40 GT40 GT40 GT40 GT40 GT40RRRRRRRRRRRRRRRRRRRRR

"Harry, the more research I do the more I think I'd like to put a T66 in my car.(The car is a fully built 13brew rotary road race car with a goal of 550rwhp) At the same time I'd like to take advantage of the relatively low cost, and great performance of the Garrett GTBB series Turbos. With this in mind I've been comparing the specs on various GT turbos to the Turbonetics Q trim T66. I am basing this on a 1.00 ar T66 since I know of a couple of guys who are using it on a T66 with good results. A GT40 comes the closest, although the compressor turbine pairing in the Garrett catalog seems to use a larger turbine than the T66 with a comparable compressor.
Turbonetics T66 specs(assuming I am reading their catalog correctly)
compressor;
90mm wheel,2.58minor,3.584 major=52 trim
turbine;
78mm, 2.693 minor, 3.111 major=75 trim, 1.00ar

Garrett GT40 Ball bearing standard specs;

(1.) 82mm 50 trim compressor, 77mm 73 trim .94 ar turbine
or
(2.) 88mm 54 trim compressor 77mm 84 trim 1.34ar turbine
QUESTIONS;
How will the first Garrett option(your initial suggestion) spool compared to the T66, and how will the ultimate HP compare? or should I(can I) try to get the larger Garrett compressor with the smaller Garrett turbine (almost the same as a T66 Qtrim) ie
T66-- 90mm 52 trim compressor, 78mm 75 trim 1.00ar turbine
GT40-88mm 54 trim compressor, 77mm 73 trim .94ar turbine
Do you know if the dispacement recomendations in the Garrett catalog are based more heavily on compressor or turbine sizing?
Garrett lists the suggested displacement for a GT35 @ 2.5L-3.2L, and a GT40 @ 3.5L-5.0L, and since a GT35/40 uses a GT40 compressor(?), I am guessing the displacement recommendation relates more to turbine size(yes?)
I'm convinced the 35/40 is a bit small for 550rwhp, Comments? (am I completely lost?)
Thanks, I will call this afternoon to discuss, Carl Byck 707-696-2705"

 

ADP (master distributor) sez not available.

ATP (engineering house) sez a couple trickle in every couple months and are already pre-sold for $1950. 0.96 or 1.06 A/R exhaust.

 

A couple of notes off ATPs site, "R" does denote BB, A 3540 is now rated for 600(I assume based on practical experience), not 700 (that is on a piston engine). Question,(true?) it seems that Tangential is an orientation, not as is popularly stated, a divided housing(this is obvious if you speak english, but I managed to screw it up. So, is it true that there are divided, and un-divided tangential turbos? Are all Garrett turbos divided as they come from Garrett? I wonder why a Gt3540 is 1200.00, and a GT40R is 1950.00? Well I guess I will stick with a plain Jane T66 for now, the 40 is out of my range for now. Carl

 

The 35/40 everyone talks about here is undivided tangential and $1750 @ ATP

 

Thought it was divided?

 

GT35R vs T78



Plus Baddog's foot

 

you guys lost me back at the second reply.

 

Sorry, Carl and I have discussed this before.

The 37 looks like a nice size, but I'm not sure it's available. The only place it's mentioned is the turbobygarrett catalogue, and a lot of those turbos aren't available. I've spent some time on the phone with ADP discussing 35's & 40's and they didn't mention the 37 at all.

 

so basically there's no experience with this turbo? It seems odd that they would put it in their catalog. I have a buddy who works (or worked? I dunno) for Garrett, he might be able to do something.

But are my assumptions correct? Would that be good for about 350 to the rear wheels at 10-12 lbs with a FMIC, standalone, and the rest of the fuel setup? Is that the sort of thing I should be looking at in the map, at 3000 RPM under boost it should be just right of the surge limit, and leave a good amount to the right of redline?

 

Yes, I belive your assumptions to be correct. But, I don't belive that the GT37 is available. Myself and several others have talked to numerous garrett distributos and the same thing comes from even the distributors "Garrett is really dumb for putting things in their catalog that aren't available."

I do belive that the 40R is a BB CHRA GT40, but I have no idea what the turbine section looks like. The Gt35/40 as everyone complains has a T3, tangential undivided manifold as seen in the pics posted by Tyson.

Now, I have been digging for a year, and seriously looking for 6 months now. I have a Gt35/40 with the 54trim compressor and the 84 trim turbine.

I will say that I am running a custom turbine housing which is very different from the norm, and that the total cost of the turbo to me was actually *less* than a normal 35/40. I am not yet ready to reveal my sources nor what the rest of my system will consist of. I will however have the system available at SS6 for all to see, and I should have a healthy dyno chart to go with it

-Chris

 

It also looks like the TO4 Housing 76 mm 52 trim, .70 A/R is a good match too. Same page as the GT37

 

Lol. Actually it's 12.5inchs!

 

Chris,

Which 84 trim turbine?

GMTA!

Tony

 

I've been playing with a Performance Calculator and can't seem to get it to settle down on efficiency. What is everyone using in their calcs?

 

the gt40 is actually pretty small, smaller than a t66. it probably has a 62 or 64mm inducer. the gt40r will make more power than a t66 due to it's increased efficiency from the new wheel and housing designs from garrett. you're looking at probably 50 more hp at higher boost. if you're going road racing get the larger of the 2 compressor and a step down from the larger turbine a/r, you'll be less laggy. as for compressor maps, down follow what they say too strictly. if you're whole setup is efficient enough, motor, int./ex. manifolds, you can boost a lot more, and make a lot more power than what the maps indicate.

 

woah. where did u get that program perforamnce calculator?

 

pm'ed you

 

yeah shoot me a PM about that program, looks pretty nice