CT26 VNT upgrade/ modification

[Winch]

You're going to lose all torque below about 2,500rpm with this turbo.

You need 15 psi below 2000rpm or drivability is going to be poor and I don't see any GT28 delivering boost that soon on a 3 litre engine and the map you've shown is very close to surge at 15lb/min and PR 2.

So in a few replies earlier on, including this post from Dougal, the thought was that the Garrett 2860R (707160-5) would not boost at low end, however, it ended up being the opposite. It certainly is boosting very nicely below 2500 RPM, but then stagnates and the boost doesnt go any higher as the RPM goes up. So, If we look at this from this opposite angle, why is that? Was the initial thinking that the turbo is too big and would take forever to spool and make boost? If so, does this development mean the turbo is too small? Boost comes on very nicely and steady from around 1000 RPM and then reach max boost at 2500 RPM, but then stagnates and just stays there even with the RPM climing steady. Thanks.

 

[Dougal]

So in a few replies earlier on, including this post from Dougal, the thought was that the Garrett 2860R (707160-5) would not boost at low end, however, it ended up being the opposite. It certainly is boosting very nicely below 2500 RPM, but then stagnates and the boost doesnt go any higher as the RPM goes up. So, If we look at this from this opposite angle, why is that? Was the initial thinking that the turbo is too big and would take forever to spool and make boost? If so, does this development mean the turbo is too small? Boost comes on very nicely and steady from around 1000 RPM and then reach max boost at 2500 RPM, but then stagnates and just stays there even with the RPM climing steady. Thanks.

How many rpm until you get 20psi with this turbo? "Boost coming in" doesn't tell us much.

 

[gerg]

Clamp the wastegate shut and see what boost it can build. You might have a leaky gate or a weak spring. A granger valve will help with low end boost as well. Pressurize your piping and check for leaks. Most systems have leaks and folks have no clue. It can easily cost you 3-4lbs boost. Fix all this and then you will know how good or bad your turbo performs. Link a video of it under hard acceleration from low rpms to see the boost build and it will also help alot.

 

[Winch]

How many rpm until you get 20psi with this turbo? "Boost coming in" doesn't tell us much.

Thanks for the reply. The max boost I'm getting which is 19 is reached around the 2500 RPM mark and it stays there.

Clamp the wastegate shut and see what boost it can build. You might have a leaky gate or a weak spring. A granger valve will help with low end boost as well. Pressurize your piping and check for leaks. Most systems have leaks and folks have no clue. It can easily cost you 3-4lbs boost. Fix all this and then you will know how good or bad your turbo performs. Link a video of it under hard acceleration from low rpms to see the boost build and it will also help alot.

Thanks for the reply. Jip I already clamped the wastegate and did a leak test. Both were good. Good idea about a video. Will try and shoot one.

 

[Dougal]

Thanks for the reply. The max boost I'm getting which is 19 is reached around the 2500 RPM mark and it stays there.

That's why that turbo is far too big. Max torque on these engines originally is around 1400rpm: http://www.toyota.co.nz/NewVehicles...r+Double+Cab/3.0L/Manual/Tech+Spec/Engine.htm
Yours is around 2,500rpm and I notice a lot of smoke in your videos.

You need a smaller turbine to produce more shaft power from the same exhaust flow. The turbo you have is intended for high rpm and high EGT petrol applications with lower boost.

 

[Winch]

That's why that turbo is far too big. Max torque on these engines originally is around 1400rpm:

Hmmmmm ok, that makes sense. This may not matter, but I should have been a bit more clear in my response above as well. The only way that I have to measure torque is what it feels like when I drive the truck and my body is being pushed back in the seat, all the way from around 1000 - 2500 RPM, but then the torque tapers off. So, I would say that I have max torque in that RPM range. I can however measure the boost and that shoots up from 1000 RPM to max at 2500 RPM.

 

[Dougal]

Hmmmmm ok, that makes sense. This may not matter, but I should have been a bit more clear in my response above as well. The only way that I have to measure torque is what it feels like when I drive the truck and my body is being pushed back in the seat, all the way from around 1000 - 2500 RPM, but then the torque tapers off. So, I would say that I have max torque in that RPM range. I can however measure the boost and that shoots up from 1000 RPM to max at 2500 RPM.

Max boost is normally max torque. Butt dyno's are notoriously inaccurate.

If you want an improvement, you're going to have to get a better turbo. It is completely unsuitable.

 

[Winch]

Ok thanks. Do you perhaps know if there is a suitable interchangeable cartridge/ turbine for this turbo, or do I actually have to get a complete new one?

 

[Dougal]

Ok thanks. Do you perhaps know if there is a suitable interchangeable cartridge/ turbine for this turbo, or do I actually have to get a complete new one?

A completely new one. The turbine and turbine housing are too big.

 

[Dougal]

OK, thanks Graeme. I appreciate the advice, but others have said that the GT2860R - 707160-5 would work for what I need it for, so now I don't know. Maybe I just haven't provided enough info here to look at this turbo from my perspective, so I will do that and I hope that you and others can confirm that this turbo won't work. I really need to get this sorted out in the next couple weeks before I start fabricating adapter plates etc. I already have this turbo and got a smoking deal on it.

So here's the background and the math that I did and it seems as if this turbo fits really well on the compressor map.

I'm working on a fairly ambitious project. I have a Toyota Tacoma, but are swapping the V6 engine out with a 3.0 litre Toyota Turbo diesel. It is the 1KD-FTV (D-4D).

This intercooled motor makes 170 Hp at 3600 rpm (red line is 4400 rpm) and 260 ft/ lbs at 1600 - 3600 rpm (all the way through). To make this work for me, I am swapping out the electronic fuel injectors with mechanical injectors from a 4.2 litre Toyota turbo diesel 1HD-T (which would provide plenty of fuel) and the electronic fuel pump with a mechanical fuel pump from this motor's pre-decessor (1KZ-T). I will end up removing most of the other electronics as well and the motor will not be electronically controlled at all by an ECU. All the tuning will be done mechanically (old school). It has a 5 speed tranny.

As such, I also need to get rid of the electronic turbo and swap in a mechanical turbo, and while I'm at it, was thinking that I would also like to upgrade that turbo for more power. I am aiming for about a 25% increase in power (roughly 170 hp to 212 and 260 ft/lbs to 325) which is nothing extreme because guys are easily getting these figures with chips and other upgrades.

I've done the math on the Garrett website and came up with the following:
TurboByGarrett.com - Turbo Tech103

Airflow:
Wa=HP*A/F*BSFC/60
= 212*20*0.4/60
= 28.3 lbs/ min

Target Hp is 170*25% = 212
A/F Air/fuel ratio for this diesel is about 20:1
BSFC Brake specific fuel consumption is about 0.4

Manifold pressure:
Map= Wa*R*(460+T)/VE*N/2*Vd
= 28.3*639.6*560/0.97*4400/2*183
= 26.0 psi

R is the gas constant
T is the average intercooled air intake
VE Volumetric efficiency for the 4 valve engine
N is red line
Vd engine displacement in cu inches

Compressor discharge pressure:
P2c= Map+Ploss
= 26+2
= 28

Assume 2psi pressure loss between compressor and manifold (due to intercooler, etc)

P1C= Pamb- Ploss
= 14.7- 1.2
= 13.5

Pamb Average Air pressure in Calgary
Ploss Pressure loss due to eir filter, piping

Pressure ratio:
IIc = 28/13.5
= 2:1

I then looked at the compressor maps and found that the Pressure (28) and ratio (2) fit very well for the GT2860R - 707160-5. Map:
TurboByGarrett.com - Catalog

Looking at the maps for the GT25, it doesn't fit as well as the GT28.

I will likely just keep the stock air-to-air intercooler, or maybe go larger because I have lots of room in front of the radiator. My main goals are to have some good highway power for cruising around 120 km/h (75 mph) and my RPM would be around 2750 at this speed and also have some good low end torque plus good fuel economy. My truck runs on 37" tires, have a 10" lift on it and alot of extra weight, which is why the V6 was no good anymore, so I need lots of torgue at highway speeds. Not so much at lower speeds or for off roading and definately not for racing or speed.

Thank you very much for your help

Found your major mistake (in bold red quote). You forgot to add 14.7psi atmospheric to the 28psi boost required. Your PR is 3.2, not 2.1.

 

[Dougal]

I've just run the numbers on compressor and turbine matching for a 3 litre tdi with the 707160-5 turbo.

Using 17:1 A/F ratio and 750C EGT it can't do anything useful. 15psi boost by about 3,500rpm.
To hit 19psi by 2,500rpm you are massively overfuelling. Your EGT must be incredibly high.

 

[DX5539]

Any recomended turbo for 1HDT...i need low rev have high torque...coz i run with 35" cooper stt ,when i take off the car time will lag...now i up boost ady but also useless...now i run 0.9bar...

 

[DX5539]

Any recomended turbo for 1HDT...i need low rev have high torque...coz i run with 35" cooper stt ,when i take off the car time will lag...now i up boost ady but also useless...now i run 0.9bar...i use stock CT26 with intercooler..

 

[Winch]

Found your major mistake (in bold red quote). You forgot to add 14.7psi atmospheric to the 28psi boost required. Your PR is 3.2, not 2.1.

Thank you for the replies. I'm not so sure that atmospheric pressure needs to be added to the boost when deciding on a turbo. In fact it states on the Garrett website to use absolute pressure and not gauge pressure: http://www.turbobygarrett.com/turbobygarrett/sites/default/files/PDF/Turbo Tech 103.pdf

Either way, I think I might be onto something else. As I was going through my calculations again (that you thankfully prompted me to do), I realized that I picked a pretty lean and optimal air/fuel ratio of 20:1 I know that I am not even near that, because I have this thing overfuelled to the hilt. I've even made certain internal adjustments to the pump to try and keep the idling down due to the fuel supply. When the truck is idling there is black pieces of solid soot coming out the exhaust and under throttle an enormous amount of black smoke. When I stand near the exhaust it causes my eyes to water.

So, I'm thinking that my air/fuel ratio could be closer to 10:1 which changes the airflow calculation dramatically. Instead of 212 hp x 20 A/F ratio x 0.4/60 = 28.3 lbs/ min it is now half that: 212 x 10 x 0.4/60 = 14.1

So, plotting this on the compression map, is obviously wayyyyyyy off for that turbo. So, if I'm grasping this whole thing correctly, it would appear to me as if this particular turbo, simply can't provide the amount of airflow that I need without massive amounts of fuel. So, I should have listened to you from the start. I thought bigger turbo = more boost = more power.
http://www.turbobygarrett.com/turbobygarrett/turbocharger

I've just run the numbers on compressor and turbine matching for a 3 litre tdi with the 707160-5 turbo.

Using 17:1 A/F ratio and 750C EGT it can't do anything useful. 15psi boost by about 3,500rpm.
To hit 19psi by 2,500rpm you are massively overfuelling. Your EGT must be incredibly high.

Yes, you're right - it is massively overfuelling. Cruising at highway speed at say 120 km/h in fifth, the EGT's are at around 8500C on level ground but the smallest of hills require me to back off the throttle cause it would quickly go to 1200. Same when I'm taking off and going through the gears. And turning the fuel down = loosing boost.

Either way, I think you are right that the turbo is not suitable, so I will start looking into options. Thanks

 

[Dougal]

Thank you for the replies. I'm not so sure that atmospheric pressure needs to be added to the boost when deciding on a turbo. In fact it states on the Garrett website to use absolute pressure and not gauge pressure: http://www.turbobygarrett.com/turbobygarrett/sites/default/files/PDF/Turbo Tech 103.pdf

Absolute pressure is guage pressure plus atmospheric pressure.
Your gauge pressure is 28psi, atmospheric is ~14.7.
The pressure ratio that your turbo works at is absolute pressure (gauge plus atmospheric) divided by atmospheric.

The pressure ratio of 3.2 is the correct one for that boost pressure.

Either way, I think I might be onto something else. As I was going through my calculations again (that you thankfully prompted me to do), I realized that I picked a pretty lean and optimal air/fuel ratio of 20:1 I know that I am not even near that, because I have this thing overfuelled to the hilt. I've even made certain internal adjustments to the pump to try and keep the idling down due to the fuel supply. When the truck is idling there is black pieces of solid soot coming out the exhaust and under throttle an enormous amount of black smoke. When I stand near the exhaust it causes my eyes to water.

So, I'm thinking that my air/fuel ratio could be closer to 10:1 which changes the airflow calculation dramatically. Instead of 212 hp x 20 A/F ratio x 0.4/60 = 28.3 lbs/ min it is now half that: 212 x 10 x 0.4/60 = 14.1

You will kill your engine attempting to run 10:1. 17:1 is the lowest you ever want to run under power. 20:1 is roughly stock.

Yes, you're right - it is massively overfuelling. Cruising at highway speed at say 120 km/h in fifth, the EGT's are at around 8500C on level ground but the smallest of hills require me to back off the throttle cause it would quickly go to 1200. Same when I'm taking off and going through the gears. And turning the fuel down = loosing boost.

Either way, I think you are right that the turbo is not suitable, so I will start looking into options. Thanks

The right turbo will boost at cruise and with the right tune will keep your EGT's always safe and your exhaust clean.
200hp clean and safe should be no problem, but it will take a lot of work to find the best turbo.