T25 Turbo Map for 3B. (1 Viewer)

[Dougal]

Here you all go. It's currently hosted on my little slice of the internet, it may pay for one of the mods to upload it to somewhere more permanent.

As you can see, I consider this to be close to the perfect fit. The red line is roughly the expected boost path on full load. This of course will depend on fueling, exhaust design and turbine size.
The slanting vertical lines are air consumption at fixed rpm but differing boost. The marks on these lines correspond to 0,5,10 and 15psi boost.
0 psi is the lowest end of the line, 15 is the top.

Questions and comments?

 

[PressOn]

Dougal,
Very nice piece of work.

Questions:

P2c/P1c is the pressure exiting the compressor/pressure entering compressor (atmospheric)? If so, I can expect to double boost pressure at rpm's higher than roughly 2000 rpm. (That's 14.7 psi of boost). Little to no boost at rpm's less than 1500.

I haven't figured out what the units are on the semi horizontal curves are with the numbers 65853, 91977, etc.

Thank you for taking the time to work it out and post.

Jeff

 

[Dougal]

Dougal,
Very nice piece of work.

Questions:

P2c/P1c is the pressure exiting the compressor/pressure entering compressor (atmospheric)? If so, I can expect to double boost pressure at rpm's higher than roughly 2000 rpm. (That's 14.7 psi of boost). Little to no boost at rpm's less than 1500.

I haven't figured out what the units are on the semi horizontal curves are with the numbers 65853, 91977, etc.

Thank you for taking the time to work it out and post.

Jeff

Yes I've put the red line roughly where I think it'll work out on a 3B. If you wind up the fuel then you'll get boost sooner, if you have conservative fuel settings and/or a more restrictive exhaust then you'd get boost later.

Those arcs are rpm of the compressor wheel. 65,000 - 170,000rpm. Pretty quick really.

 

[Diesel42]

Hey Dougal you pulled through, thanks. O'kay, so is this to say that any T-25 A/R=.60/.46 will perform within this mapping? So if us novices were to call up a turbo spec. shop with this mapp they would know which turbo to sell us? You mentioned turbine size. What turbine size is right for the 3B application? Well done, this post should be sticky'ed.

 

[Dougal]

Hey Dougal you pulled through, thanks. O'kay, so is this to say that any T-25 A/R=.60/.46 will perform within this mapping? So if us novices were to call up a turbo spec. shop with this mapp they would know which turbo to sell us? You mentioned turbine size. What turbine size is right for the 3B application? Well done, this post should be sticky'ed.

This compressor comes paired with a housing A/R of 0.48.
The compressor wheel comes in two "trims". The trim refers to the ratio of wheel diameters (small^2/big^2).
The 60 trim wheel is 51.3mm od and steps down to 40mm at the intake.
The 55 trim wheel is also 51.3mm but steps down to 38mm at the inlet.
But the differences in the maps are minor for this application, either will do.

The turbine can vary, some will be 0.49 A/R and this is the one you want. Others will be 0.64 A/R which will still work but won't boost as soon as the 0.49.
These numbers are cast into the turbine housing (hot side) by the neck which bolts to the exhaust manifold.

I think the closest turbo in the current garrett GT range would be the GT2052.
TurboByGarrett.com - Catalog

 

[Diesel42]

O'kay this turbo says it's wastegated. Does this mean that it has a cetrain amount of boost? As i've read, it seems popular opinion is to stick around 8-9lbs., not to exceed 12-14 for short periods. What is your view? I feel you've armed us with enough information to shop with some degree of scientific data. I can't tell you how many turbo places i've found on the net that have said,"well this one should do!" When i ask why they feel it would work i don't get any reasonable explaination other than i will be happy with it.

 

[Dougal]

O'kay this turbo says it's wastegated. Does this mean that it has a cetrain amount of boost? As i've read, it seems popular opinion is to stick around 8-9lbs., not to exceed 12-14 for short periods. What is your view? I feel you've armed us with enough information to shop with some degree of scientific data. I can't tell you how many turbo places i've found on the net that have said,"well this one should do!" When i ask why they feel it would work i don't get any reasonable explaination other than i will be happy with it.

Yes the wastegate sets the boost. What the wastegate is set to will depend on what it was originally fitted to, but 9psi comes up surprisingly often.
If the wastegate arm is threaded, then it can be adjusted to change the boost level. I cut the arm on mine and welded in an adjustable section which works very well.

My view is that boost in itself isn't a big problem for engines, the problem is the combination of boost, fuel and injection timing. A combination producing a big power increase with the timing retarded further won't stress the engine as much as the same power level produced from further advanced timing.
Basically it's a complex relationship in which you pay your money and take your chances.
Personally I wouldn't be taking a 3B (esp one with a lot of km) past about 10-12psi boost depending on how long the potential walk home is.

 

[Tapage]

Interesting post thanks dude ..

I saw in the map, that you get aprox 24lb/min flow rate .. how this match with your engine requirements at 3500 rpm .. ( sure you are like me that never considere running your engine at that range for much time )

 

[Dougal]

Interesting post thanks dude ..

I saw in the map, that you get aprox 24lb/min flow rate .. how this match with your engine requirements at 3500 rpm .. ( sure you are like me that never considere running your engine at that range for much time )

I can't imagine anyone running a 3B at that rpm for long. Without earmuffs at least.
But I've plotted that at 100% VE, at that rpm the actual VE could be down below 70% (17lb/min). The reason I plot at 100% is that everyone uses different numbers for VE and 100 is the easiest place to scale from.

 

[Diesel42]

Thanks for the work,Dougal. I spoke with one Garrett dealer today. They wanted $800.00 USD, for the GT2052. Another turbo spec shop wanted $650.00USD to build a turbo based on your map. Spendy yes, but, cost of 13BT manifold($400.00 delievered)and turbo(say800.00)=$1200.00. Still a far cry from the $3000.00 plus that ATX and powerglide wants. Q: This Garrett turbo has a round intake(where it bolt up to the exhaust manifold), and the 13BT manifold has a rectangular port. I realize a adapter will have to be fabricated but is there a problem with the two shapes not matching properly? And when i machine a adapter, which shape do i machine too?

 

[Dougal]

Thanks for the work,Dougal. I spoke with one Garrett dealer today. They wanted $800.00 USD, for the GT2052. Another turbo spec shop wanted $650.00USD to build a turbo based on your map. Spendy yes, but, cost of 13BT manifold($400.00 delievered)and turbo(say800.00)=$1200.00. Still a far cry from the $3000.00 plus that ATX and powerglide wants. Q: This Garrett turbo has a round intake(where it bolt up to the exhaust manifold), and the 13BT manifold has a rectangular port. I realize a adapter will have to be fabricated but is there a problem with the two shapes not matching properly? And when i machine a adapter, which shape do i machine too?

This T25 does have a rectangular exhaust inlet port. Will AXT or Turboglide sell their manifolds seperately? I can't remember which but one of the aftermarket guys do use a T25 turbo.
I will post up a drawing shortly.

My T25 is from a nissan CA18DET. It may be worth calling up a few turbo shops frequented by ricers and asking for a CA18DET turbo. They're very cheap here ($200 gets you a good second hand one), but we have a lot of japanese turbo cars on the road.

 

[Dougal]

Here's a link to a drawing of the T25 inlet flange.

http://users.actrix.co.nz/dougal.ellen/forums/T25_Flange.PDFhttp://users.actrix.co.nz/dougal.ellen/forums/T25_Flange.PDF

right click, hit "save as". It's 500kB.

 

[NStimac]

Have you seen Ray Hall Turbocharging - Java turbocharger flow map calculator

They have a nice calculator on there website

I tossed some comparable numbers at the T3 45 trim (I think this is in the .42/.48 T3's) map. If you choose a more moderate (I don;t know if 80% is even realistic) VE value it starts to look really nice.

Happy web boosting

-Noah

 

[Dougal]

Have you seen Ray Hall Turbocharging - Java turbocharger flow map calculator

They have a nice calculator on there website

I tossed some comparable numbers at the T3 45 trim (I think this is in the .42/.48 T3's) map. If you choose a more moderate (I don;t know if 80% is even realistic) VE value it starts to look really nice.

Happy web boosting

-Noah

Yes that is a nice match. But where can we find them?
I have trolled through Ray Hall's site before, it's another wealth of info. I bought a turbocalculator program because it promised T25 maps, holset maps etc. But I was quite disappointed with the quality of the included maps.

IHI made an RHB6 turbo fitted to the early 3.8L 4BD1T's which is basically a T3 with a 0.42 A/R turbine. Unfortunately they are rare and parts for them are only available secondhand. I have one with an eroded compressor wheel which started me on the turbo search about 4 years ago.

 

[NStimac]

Yes that is a nice match. But where can we find them?

The small T3 is common in Volvo 740's and 240's (some are the large .60/.48). I believe also maybe Saab 900's too. There pretty common on 2.3-2.5 Liter turbo motors here in the states. Not sure about what you guy got down there in NZ besides sheep.

I was looking at your map this morning and wondering where your numbers would plot with a lower VE. I don't know a 3B-T's VE but I bet its not 100%. Lower VE is going to shift every thing to the left, maybe close to the surge limit not sure though. Just a thought. Someone once told me "Junk in, Junk out" so watch what numbers you choose.

Both the T25 and T3 have similar AR's. If it plots within the surge limit with a more reasonable VE sounds like a great choice. Probably spool a bit quicker than the T3.

Cheers
-Noah

 

[Dougal]

The small T3 is common in Volvo 740's and 240's (some are the large .60/.48). I believe also maybe Saab 900's too. There pretty common on 2.3-2.5 Liter turbo motors here in the states. Not sure about what you guy got down there in NZ besides sheep.

I was looking at your map this morning and wondering where your numbers would plot with a lower VE. I don't know a 3B-T's VE but I bet its not 100%. Lower VE is going to shift every thing to the left, maybe close to the surge limit not sure though. Just a thought. Someone once told me "Junk in, Junk out" so watch what numbers you choose.

Both the T25 and T3 have similar AR's. If it plots within the surge limit with a more reasonable VE sounds like a great choice. Probably spool a bit quicker than the T3.

Cheers
-Noah

Yes a lower VE shifts everything left. But VE changes over the rev range, at very low RPM a VE close to 100 could be realistic, but approaching the rev limit I'd expect it to drop like a stone.
That's why I plot at 100%, I leave the fudge factors up to the reader and keep them out of the calcs.

The T3's have 60mm exhaust and compressor wheels, where the T25 has a 51.3mm compressor wheel and 53mm exhaust wheel.
To get the same tip speed on the 60mm T3 wheel requires a smaller exhaust scroll.
You need a 0.42 on a T3 to equal a 0.49 on a T25.

Multiply the exhaust A/R by the R of the wheel and you get what I call an effective flow area. Bigger number means more airflow is needed to get it spinning.
Basically the exhaust scroll creates a free vortex, the exhaust wheel converts that to torque on the shaft by interrupting it at the wheel tips.
The smaller the wheel, the faster the air is moving when it hits the tips.

 

[Tapage]

I'm running smaller .38 AR turbine side .. with pretty nice low end boost .. but also a item to keep in mind it's the restriction and backpressude that make the turbo in the exhaust flow rate .. when the AR it's to tight ..

 

[wesintl]

I've got a t3. .42/.48 (off a volvo 760) installed with no wastegate and 2 1/2" exhaust. I can make 15psi like it's nothing and I've had it over 25 psi. I played with the fuel a bit but to get it low enough to only make 15psi it was back to being a slow slug. I don't know if I need to put the wastegate back on so I can limit it my boost or what. On my trial run I kept popping off that one hose on the venturi and I didn't have hose clamp on my trial run, even so I'd probably be boosting 20 with a lower fuel setting. I'm not sure what i'm going to do.

 

[Dougal]

I've got a t3. .42/.48 (off a volvo 760) installed with no wastegate and 2 1/2" exhaust. I can make 15psi like it's nothing and I've had it over 25 psi. I played with the fuel a bit but to get it low enough to only make 15psi it was back to being a slow slug. I don't know if I need to put the wastegate back on so I can limit it my boost or what. On my trial run I kept popping off that one hose on the venturi and I didn't have hose clamp on my trial run, even so I'd probably be boosting 20 with a lower fuel setting. I'm not sure what i'm going to do.

Do you have a wastegate that's blocked off? If not you could use an external wastegate like the ricers use. It'll need some exhaust replumbing though.
Do you have a pyro? With a wastegate you can seperate the boost levels from the fuelling to some degree, by limiting boost to what is necessary for smoke and EGT control you'll get more power due to less backpressure.

 

[Diesel42]

Dougal, check your PM's