Twin turbo configuration questions: Theory & Application

[WydRyd]

A good pair of twins would be Garret T3 Super 60's with 0.63 A/R Hot Housing. Good for up to 650HP with proper tuning

Aren't the GT series of Turbochargers water-cooled only? I didn't think you can get these in oil cooled only coinfigs???

[Natchamp]

Well, I got my new little baby snails today, here is a pic. They are GT28RS's. It will be interesting to see how they compare to the K16/24 hybrids.

[ohecht]

I can't wait to "see" it running in the car, Mark. I am a little surprised you did not just make your own custom ones from scratch, though!

Olivier

[ohecht]

Well,

I caved to the pressure to have 2 identical, brand new, cheap turbos for this project, and got the $200 T-25s:



I took the muffler off yesterday to just see about fitting and orientation options, and it is going to be a tight fit. I thought the IC part of the project would be the hardest, but I think fitting everything high enough to drain oil, in a half-decent orientation, and with any room for some kind of muffler, will be the challenge.

It seems really hard to get the center housing high enough to even be even with the bottoms of the timing chain covers to properly drain oil. I am curious how high other have gotten the turbos and what their drain angle for the oil return is.

I also found out one of the reasons they were cheap...they have a less-common 5-bolt turbine exit flange. There are flanges and parts out there, but not as many off-the-shelf options in terms of O2 housings, etc., like for the T-25s common on Eclipses, Lasers, Talons, etc. I think these are actually Nissan's version of the T-25, used on the Nissan Skyline in Japan and possibly 300 ZXs. They should be a decent fit if they worked on a 3.0 liter, 6 cylinder 300ZX as a pair.

PS, to help fitting, I can easily clock the turbine sides by loosening a few bolts. However, I need to also rotate the compressor housing around the center assembly in order to keep the wastegate actuators aligned. There is only a giant snap-ring on the compressor side. Can anyone confirm that just removing this ring will allow me to rotate both sides around the center housing? I don't want to mess up brand new turbos by taking the wrong thing apart.

PPS, I just had to start the engine with no muffler after the SSIs. Wow! Sounds like something in between a NASCAR and a top-fuel dragster! I was almost tempted to leave it that way for a few days.

Olivier

[raceman]

there`s a guy in Utah selling new T-25`s for $200.00 each..same guy? l my buy a couple myself,have you sourced the exhaust flange yet?

[ohecht]

That is the same guy. The turbos were delivered within a week, new in the box in perfect condition.

Here is a place with some of the 5-bolt flanges and adapters, everything from a flange only to an adapter to a v-band connection that would make disconnecting the rest of the exhaust really quick and easy:

http://www.atpturbo.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=tp&Category_Code=FLS

Olivier

[ohecht]

Does anyone know the make, model, and trim of the turbos Volvo uses on their twin-turbo 3.0? My father-in-law has that engine in the XC90, and they look much smaller than the T-25s I have. That would be great for fitting them back there, and I think the Volvo is also a low-boost TT of the same size. They look like they were no more than 4-5 inches in diameter, and I am having a hard time seeing how to fit 2 T-25s, mufflers, etc.

I could not see any markings at all on the turbos, and I am hoping someone here familiar with Volvos might know what they are and maybe where to find some.

No one in the on-line Volvo community seems to know what kind of turbos are used.

Thanks,

Olivier

[RarlyL8]

It would stand to reason that turbos used in a stock application would not be optimal for the same displacement high performance use.

Don't know about the Cross Country Volvos. Find out from your dad-in-law what the HP and redline is on that engine. Probably not what you are after.

Also - I have repeatedly contacted your tt source via e-mail for specific information of those "value engineered" turbos. He sent me the payment address and nothing else. Can you e-mail me or post this info?
I'm actually thinking of using a pair of stock 3LDZs for my mock-up. They are huge so if they can fit anything will.
I was in Indy this weekend for the F1 and other business. Stopped by my p-mechanic's and picked up all the other engine stuff I needed for the conversion (I think). So I hope to be starting this project by late summer.

[ohecht]

Rarly,

Good point about the redline, etc. I had not considered that.

All I ever had from the T-25 seller was the e-mail address where I sent the payment via PayPal.

I think the package did have some information from the turbo business that I think his father owned and for which the turbos were originally purchased. It was a diesel-focused turbo shop. I can try to find that when I get home from work if you think that will help, but I bought them only knowing his e-mail address through PayPal.

It sounds like you will progress faster than me, I look forward to hearing how you solve some of the issues. I took the family for a drive in the country yesterday, and the engine was powerful and flawless with CIS and everything. Not a pop, stumble, etc., just smooth available power in mostly 3rd gear curves. Makes me wonder again why I should mess with something performing so well! I will do it eventually, but I am not in any rush to make changes! It's been fun practicing stick welding exhaust tubes, though!

Olivier

[beepbeep]

Originally posted by ohecht
Does anyone know the make, model, and trim of the turbos Volvo uses on their twin-turbo 3.0? My father-in-law has that engine in the XC90, and they look much smaller than the T-25s I have. That would be great for fitting them back there, and I think the Volvo is also a low-boost TT of the same size. They look like they were no more than 4-5 inches in diameter, and I am having a hard time seeing how to fit 2 T-25s, mufflers, etc.

I could not see any markings at all on the turbos, and I am hoping someone here familiar with Volvos might know what they are and maybe where to find some.

No one in the on-line Volvo community seems to know what kind of turbos are used.

Thanks,

Olivier

It's pair of Mitsubishi TD03's...engine is 2.8L and turbochargers are watercooled. Engine has 272HP and redline won't tell you anything interesting.

[RarlyL8]

In the absense of a dyno chart or turbo map all you (I) have to draw on are the parameters of the "donor" turbo engine.
An extreme example would be a diesel vs a high strung gas engine. The former would redline much sooner than the latter. If this is a street engine optimized for low end use then the turbo would/should run out of breath way too early if used on the high strung engine of similar displacement.
Not knowing anything else other than the redline and HP numbers, the Mitsubishi tubos an the other hand seem like a very good match for a street turbo SC.
This is why we need the help of you seasoned turbo guys - there is so much more to optimizing these systems.

[KobaltBlau]

Originally posted by beepbeep
It's pair of Mitsubishi TD03's...engine is 2.8L and turbochargers are watercooled. Engine has 272HP and redline won't tell you anything interesting.

Goran can correct me if I'm wrong, but the TD03s on the T6 are not viewed by the volvo community as having a lot of potential for power increase. What I'm saying is another twin turbo engine with similar horsepower might have turbos capable of significantly more, but this engine doesn't really.

I have not seen compressor maps for these... have you, Goran?

[beepbeep]

Originally posted by KobaltBlau
Goran can correct me if I'm wrong, but the TD03s on the T6 are not viewed by the volvo community as having a lot of potential for power increase. What I'm saying is another twin turbo engine with similar horsepower might have turbos capable of significantly more, but this engine doesn't really.

I have not seen compressor maps for these... have you, Goran?

I only have maps for TD04 and bigger. I don't know much about that Volvo engine but more power can be obtained by switching to single bigger turbo (as with most other twin-turbo engines).

As I said before, redline doesn't mean a squat. It is just a number where rev-limiter engages. I believe Volvo B6294 (which this engine is called) delivers 272hp at 5500 RPM.

What matters the most when choosing turbo is mass flow. Turbo doesn't know if it's connected to 4L engine turning 2000RPM or 2L engine turning 4000L...it will spin equally fast (as far as VA and boost is the same).

You have to understand the basics of choosing turbochargers:

1. Find out if you want to go twin or single (twin for somewhat better response and simpler tubing, single for more power)

2. Decide how much boost you want and at what revs (if you can program your ECU to custom boost curve, the better)

3. Find out your mass flows at different RPM's.

4. See what turbos are available in your particular configuration. Chances are there won't be more than two three at most. Big companies can approach turbo-manufacturers (and there are less then six of them) and let them develop exactly what they want, knowing they will need millions of them. You cannot do that and have finite amount of pieces to choose from (in this case, those that aren't watercooled).

5. Plot your mass-flow onto it's compressor map and decide what character you want. Most manufacturers let middle-range boost go trough efficiency island for shortest lag and good torque, and let ECU taper boost at higher revs to keep turbo from overrevving, knowing that few will run their engines at high revs. This is the point that most DIY-ers miss. Many have choosen turbos a number too big, so they hit efficiency island at high revs...it will give you best power but spoolup and torque curve will suffer, actually giving you slower accelleration (as long as you don't use Variator tranny). Also, most DIY-ers use ordinary mechanical wastegates so they cannot program boost taper at higher revs. This forces them to choose a tad bigger turbo. Where you want it is up to you. I prefere good torque, fast spoolup and moderate boost. It will keep stuff from grenading and give you nice push in the back. (OK, I'm actually mating GT40 to 2.3L engine but that's pure track machine )

[ohecht]

I thought you guys would know the model of turbos those were...I was surprised at how small they are, looks like they could fit on a motorcycle.

I am not looking for massive power gains, just a little more power and torque that is gentle on the engine and available at the lowest rpms possible.

Do you think those are a possibility? Or would their very small size choke the engine at higher rpms?

I think I saw some maps for them, let me check...

Here is the link to all the maps I have ever found, and it has TD04s and 05s, but no 03s. I assume the 04s are physically larger than the tiny TD03s.

compressor maps

Olivier

[ohecht]

Originally posted by beepbeep
I prefere good torque, fast spoolup and moderate boost. It will keep stuff from grenading and give you nice push in the back.

Goran,

That is what I am looking for, too, but I have pretty much resigned myself to water-cooling the bearings.

I am worried now that my T-25s are too big to warrant the trouble fitting two such large turbos high enough behind the engine to drain the oil properly, and I would prefer smaller, "gentler" turbos that I could more easily fit.

Thanks for your continued insights.

Olivier

[beepbeep]

Well you can have them low, but then you need to fabricate small "oil-sumps" underneath every one and have it scavenged with (electric?) pump into the valve-covers or oil tank.

[ohecht]

Goran,

I am also interested in your comments about the WG controller. I plan to use Megasquirt to keep the A/F ratio as close to optimal at all times to protect the engine, and I have looked into electronic boost controllers, too.

My understanding was that they can only increase boost from the "stock" WG setting, and my internal WGs are set at 7 psi, I am told. I would like more control over when the WGs begin to open, etc., since testing the true boost levels by risking my engine detonating is one of my big concerns about this project.

Olivier

[beepbeep]

Yes, boost controllers work by letting out air from wastegate bell trough a solenoid-controlled pulse-width-modulated valve. So they can only control boost above mechanical setting of wastegate (called "base boost"). They are often built in into more advanced EFI-systems.

It's wisest to select wastegate that has it's boost pre-set at say, 7psi and work upwards depending on knock/boost/compression.

[RarlyL8]

So what would be the absolute best oil cooled twins to use for a street 911 engine from 3.0L to 3.3L displacement? (Boost level 0.7bar able to support an expected power output of ~350 to 400HP with good low end)
There can't be many to choose from.

[ohecht]

My earlier calculations made me think the TD04-13G or TD04H-15G would both be good fits, but they were hard to find cheap and I don't know about their physical dimensions.

I think they are more expensive since they are popular "Stage 1" and "Stage 2" upgrades on 3000GT twin turbos and possibly other PEM TT applications like 300ZXs, etc.

Olivier