Twin turbo configuration questions: Theory & Application

[ohecht]

I am also thinking about small twin turbos mounted to the rear of my SSIs on my 3.0 with 9.3 compression.

I am not looking for high HP, but smooth delivery of slightly more power that will not harm the stock engine. More of a fabrication challenge, really, and I would love the symmetry of the design and the "unique" factor. Maybe a 2-in, 1-out IC, too, once I lose the CIS equipment for EFI.

Are there even turbos small enough to deliver only 8-10 psi in total when used in pairs?

I would like to keep costs down, as this is an experiment, really, and find turbos used in stock applications in a yard somewhere.

Olivier

[tsuter]

The Twin T concept with SSI is developed here:

Understanding Turbo Compressor Maps

[ohecht]

I like the "smaller is better" idea for a quick-spooling, low-pressure twin setup on a 3.0 SC to build more torque than total HP.

I saw the GT17 recommendation, but what about the GT15?

It seems to be one of the ones on many VWs for availability.

Do any of the experts reading a plotting the compressor maps have insight to share on that setup?

Olivier

[ohecht]

I am also looking at T3's for my low (7 psi) boost application, but I have found a potential source for new T25s cheap. The problem is, I cannot find a map for them anywhere.

Does anyone have a map for a Garrett T25 turbo with 48 trim? Or any T25 map? The turbine A/R ratio on these is .49 and the part number is 465749-5001 if that matters.

If no maps are available, does anyone have experience with these in terms of general size and characterstics for a low-boost TT 3.0 setup? I would like to rule them in or out before I let the opportunity to get them cheap go.

Thanks,

Olivier

[ohecht]

I found this diagram, but I don't know how to read this type (yet).

http://www.gcg.com.au/technical/garrett%20t2-25%20flow%20map.jpg

Olivier

[beepbeep]

Originally posted by ohecht
I am also looking at T3's for my low (7 psi) boost application, but I have found a potential source for new T25s cheap. The problem is, I cannot find a map for them anywhere.

Does anyone have a map for a Garrett T25 turbo with 48 trim? Or any T25 map? The turbine A/R ratio on these is .49 and the part number is 465749-5001 if that matters.

If no maps are available, does anyone have experience with these in terms of general size and characterstics for a low-boost TT 3.0 setup? I would like to rule them in or out before I let the opportunity to get them cheap go.

Thanks,

Olivier

Ello!

T25 in it's biggest trim is producing 200hp with ~2200RPM boost treshold on 2.3L four-cylinder engine. Chippable to approx. 240 but then you are really just pumping hot air.

...so two of those could easily produce around 400hp. My guesstimate is that two T25's on 3.0 would have approx 3200 RPM boost treshold and could pump 400hp worth of air w/o problems.

Want low-boost and driveability? Go for GT17 or 15 instead...

You basically need two turbos that are usually fitted to a 1.6L engine... I'm unfortunately not so good when it comes to so small snails, most of them are watercooled as well...

[ohecht]

That's what I'm finding, all of the small turbos seem to have small shafts and potential reliability problems.

I also worry that a 6500 rpm redline would overspin many of these smaller ones pushed to their limits.

Are the maps for the smaller turbos harder to come by?

Olivier

[ohecht]

PS, I appreciate everyone's great advice and input. This will be a long project, but I am going to Hershey on Friday and I need to have a few things to look for. I would hate to take a chance on a "good deal" that is totally wrong for my project.

Thanks again,

Olivier

[Natchamp]

Oliver, you don't need to worry about the reliability of the smaller turbos or them over spinning at 6500 rpms. As BeepBeep pointed out, just think of each turbo working with a 1.6L motor.

[RarlyL8]

What about turbos designed for motorcycles?
With engines up to 1500cc (1.5L) and redlines upward of 9000RPM there ought to be something out there we can use.

[ohecht]

Thanks, Mark, just too many choices out there. I even found two sets of T3 maps that were totally different, so that didn't help! Maybe we should make a post of just compressor maps to give people going down this path in the future a single source of some basic information.

Rarly, I have actually been looking at motorcycle turbos, or at least ones that small. The Aerochargers that Corky Bell recommends (and sells), seem tempting (since they are self-lubricated and have variable turbine VATN technologies), but they are way too expensive and it seems reliability is an issue. Not too much out there on them recently.

Back to the maps, does anyone have the way to convert lbs of air to the cubic meters I see on some of these maps?

Olivier

[ohecht]

Rarly,

I forgot to mention I found a source with many new T25 turbos with wastegates for $200 each, if I can only convince myself they will work that seems like the best deal I can find.

They are ".48 compressor A/R ratio" but I am not sure what trim that equates to.

Olivier

[ohecht]

Update from the seller, he thinks the T25 turbos he has are 45 trim compressor and 61 trim on the turbine side.

Olivier

[ohecht]

I found a source with almost every compressor map I have seen in one place, and I will also post it on a separate thread for easier reference. It even contains supercharger maps and is appropriately called the "Big Collection of Compressor Maps".

http://not2fast.wryday.com/turbo/maps/all.html#t

Olivier

[RarlyL8]

$200?
Even if they are not a perfect fit I would bite. This is a fun project only. Cost is critical. Please let me know if they might work.

[Lukesportsman]

Oliver,

I would definitely be interested also. I have bought 1 T3 .48/.60 so far, but for this price new, might switch ideas. Too bad Rarly, your not still in this neck of the woods.

[ohecht]

I am in the same boat. $200 each for new turbos is great, as long as they are close to a good fit, but I am having trouble even finding that out.

Rarly, I am the same in terms of fun vs. cost. My car runs too well to spend big $$ just for something "neat". I am worried about getting turbos that would damage something by not being sized correctly, though.

He seems to have plenty, so I can send you his contact info if you are interested in checking them out or giving them a try.

These are of course watercooled, but I have heard several people say you could run them without water cooling, and I think a coolant setup would not be too hard and might be a more fun part of the project.

Here is a link to an even cheaper twin setup, but I am having trouble confirming the fit since the flow is in cubic meters:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&category=33742&item=2474142589&sspagename=STRK%3AMEBWA%3AIT

Olivier

[RickM]

Curious as to what Protomotive uses in their twin setup. That would be an excellent starting point to say the least.

[RickM]

Has anyone tried this turbo selection calculator? Don't recall seing it... http://www.turbofast.com.au/TFmatch.html

[ohecht]

That calculator is indicating GT25 with a .63 turbine AR for a TT SC setup, which I assume is similar to the T25 just with ball bearings.

The ones for $200 are .61 AR. Hmmm...

Olivier