VF28 without engine management

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just-rust
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VF28 without engine management

Post by just-rust »

A question for you turbo gurus. If I was to put on a VF28 without any engine management at 11 psi boost would I have any problems? Blew the seals on a recently installed TD04 and was just wondering. Rob Tune will go in this spring. Figured I could just save a step and install the 28 if my injectors would play nice with it.

Problem is I already picked up another TD04 and wish I had asked this beforehand. The good news is that I am covered either way.
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

mike-tracy
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Re: VF28 without engine management

Post by mike-tracy »

I'd encourage you to run the td04 on stock ecu/injectors and wait for the robtune to install the bigger stuff.

A member on here did extensive data logging with an otherwise stock car and a td05. His car ran really lean under boost.

I have experience with the 440s on the stock ecu - you loose crisp throttle response and your fuel economy goes to crap!

Tldr;

be patient and install the goodies when you have the ecu for it.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote:
Mon Jan 14, 2002 10:23 am
Wait....I'm confused now.

just-rust
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Re: VF28 without engine management

Post by just-rust »

Great info! Thank you for posting up. I was definitely being hopeful it seems. Read a lot of comparisons between turbos and the 28 was always the "little" guy. I guess I started thinking it didn't have as much punch as it really does. I will wait and do it right. Thanks for talking me down!
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

wtdash
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Re: VF28 without engine management

Post by wtdash »

I 100% agree w/Mike.

My only suggestion - so you're not swapping turbos again in a few months....turn DOWN the boost to stock and run the VF28.

The VF28, as you probably know, is the older cousin to the VF39/43/48 in the USDM STi. It's big step above both the VF11 and TD04, but IMHO is "OK" if you turn it down.

I have the VF28 on my WRX and it seems like a decent balance between spool and top-end.

GL,
Td
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just-rust
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Re: VF28 without engine management

Post by just-rust »

Good news to hear about where the 28 performance sits. Glad you got it in the WRX and it is running well!

I don't need any substantial power at any point from now until spring and saving another swap would be great. With that said, even if I turned boost down to 6 psi, would this be a good balance where it would be hard for the 28 to max out my injectors? I don't know how the AFR and cfm would come into play with a set-up like this but I would think with boost at 6 psi, the turbo wouldn't have a chance to really max out the stock parameters. Sorry to be layman but I would definitely be interested to hear some thoughts on this.
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

wtdash
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Re: VF28 without engine management

Post by wtdash »

See if Mike replies - or another w/more knowledge than me - but I'm looking @ the fact that the stock setup can be turned up to 12 PSI - just under fuel cut - on the VF11 w/out issue. Which tells me there is some 'overhead'.

Plus, your TMIC will work on the VF28, which helps keep your intake Temps lower than the stock setup ever could.

And you're in the snow belt, so your weather is also conducive to keeping the heat down 'til Spring.

TD
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'87 GL-10 Turbo 4WD Wagon (pre-Loyale) - SOLD
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just-rust
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Re: VF28 without engine management

Post by just-rust »

That is what I was thinking without being able to express it very well. And to piggyback on what you are saying, just because it is a bigger turbo is there a certain boost level that will match a stock turbos performance or will the 28 still churn out 415 cfm even at 6 psi?

I would think the TD04 does exactly this at a lower rate than the 28 but the car still responds positively to the extra air without starving the fuel. Again, layman expression but I hope it makes sense.
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

just-rust
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Re: VF28 without engine management

Post by just-rust »

I guess the question is: Can a larger turbo be run on stock settings/internals and if so what is the formula?

I am very interested in this subject now and did a little searching. I have posted some quotes from one person below as a conversation starter here. I don't know if what was said makes logical sense because people on here running the TD05 have experienced problems on stock settings. Can simply turning down the boost solve the problem? Can running a wideband and testing different boost levels solve this? Would be interested in thoughts. If this has been covered here please post a link.

Here is the stats of both turbos:

Mitsubishi TD04L-13T
(390cfm at 14.7psi, 200-275whp, Bolt-On)

IHI VF28
(425cfm at 18psi, 250-325whp, Bolt-On)

Here are the comments mentioned above:

It seems that the cfm is dependent soley on the volume of the engine and the RPM of the engine. And lbs/min depends on the pressure (which is the same on the big turbo and little turbo), the cfm (which is the same on big turbo and little turbo at a given PSI) and temperature (which is the only factor that changes due to turbo size).

Next statement:

CFM is only the product of the amount of air being moved in one rotation of the turbine by the SPEED of that turbine. At a given and non-changing PSI, a larger turbo spins slower because it pushes more air PER spin than a smaller turbo at the same PSI. CFM at a given PSI is CFM as a given PSI, no matter the turbo.

I'm convinced that CFM ratings on turbos are only meant to be MAXIMUM CFM ratings, because smaller turbos will eventually reach a point where they can no longer spin any faster and push any more air. But if the given PSI is low enough that it can be reached by both turbos, the only thing that enables a bigger turbo to push more lbs/min is the fact that it operates at a lower temperature due to its slower spin speed.

Like this: Let's say for the sake of the example that the CFM rating of a t-25 is 375 cubic feet per minute. Let's suppose that a 16g has a CFM rating of 500. If i subjected both turbos to a pressure of 12 PSI, both turbos would be pushing the same amount of cubic feet per minute of air. I don't know what that CFM would be, but it would be THE SAME NUMBER for both turbos.

Now, if I raised the boost of both turbos to 18 PSI (theoretically speaking), the t-25 would now be outflowed by the 16g, because it's maximum CFM has been reached and surpassed, while the 16g still pushes more air per revolution of the turbo and therefore has a higher maximum CFM.

Taken from here: http://www.dsmtalk.com/forums/showthread.php?t=169722
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

mike-tracy
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Re: VF28 without engine management

Post by mike-tracy »

Any formula that is applicable to turbos on our cars would rely on everyone having the same exact equipment in the same exact condition.

I think if you ran the VF28 at wastegate pressure only it'd be fine.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote:
Mon Jan 14, 2002 10:23 am
Wait....I'm confused now.

just-rust
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Re: VF28 without engine management

Post by just-rust »

I didn't realize how much variable there was concerning the volume of air in the cylinder. It should have been blaring after reading that the thickness on the head gasket can change the compression ratio. Thanks for making that point. I read it but it obviously didn't sink in.

The 28 runs wastegate pressure at just over 10 psi (.7 bar). Is this where you were thinking it would be at? Seems higher than what would be a good idea. I figured running it at 5 psi with the MBC would keep it tamed and not risk leaning me out.
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

mike-tracy
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Re: VF28 without engine management

Post by mike-tracy »

Yeah I was thinking 7-8psi, which is what my td05 runs at IIRC.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote:
Mon Jan 14, 2002 10:23 am
Wait....I'm confused now.

just-rust
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Re: VF28 without engine management

Post by just-rust »

Thanks for offering up insight guys! I will turn down the boost and try it out. After this I should be pretty quick at swapping so putting the 04 in quickly shouldn't be a problem if it doesn't work out. I will report back results after it is installed and have run it for a while.
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

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Re: VF28 without engine management

Post by Legacy777 »

I wanted to add some additional insight to comments you posted above.

The compressor of a turbocharger has an operating envelope or map that it operates on. Certain areas are more efficient than others, but the map is typically comprised of volumetric flow rate on one axis and pressure ratio on the other with efficiency and speed lines running through the map. Pressure ratio is calculated used the turbo discharge pressure divided by the turbo inlet pressure. Both pressures need to be absolute pressure. So if you're running 10 psig, your pressure ratio would be (10+14.17) / 14.17 = 1.68 (assuming you are at sea level).

Efficiency lines throughout the map are essentially showing how well the compressor is compressing the air. The lower the efficiency the hotter the discharge air will be at the same pressure ratio.

Below is a link to the vf11 turbo map, you can see the various items I mention on that map, unfortunately flow is in metric terms.

http://main.experiencetherave.com/subar ... or_Map.pdf

Regardless, running a slightly larger turbocharger at lower boost on the stock ej22t engine should be alright. I don't know where the VF28 falls in comparison to the TD05-16G, but I ran the TD05-16G at stock boost levels on the stock engine/ECU.
Josh

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just-rust
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Re: VF28 without engine management

Post by just-rust »

Thanks for the info Josh! It will take me a bit to wrap my head around it but that is nothing new for me. Can't wait to get back on the road.
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

robertpaige
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Re: VF28 without engine management

Post by robertpaige »

I ran a TD05 16G on stock setup at 11/12psi and my AFR's were always good. If you're worried, just cruise wastegate pressure, that turbo should be fine.
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just-rust
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Re: VF28 without engine management

Post by just-rust »

The 28 is in! Instead of a day and a half it took less than 4 hours this time which is pretty awesome. This turbo is excellent. Kicks in hard right around 3500-3600 rpm and holds boost right to redline. Turned the MBC down to 7 for the inaugural run but apparently it really likes to stay in the 10-11 range. No fueling issues at all. This turbo pulls hard through all the gears which is nice on the stock settings.

Quick question. I have had two blown turbos now in the same amount of months. Should I get my cat changed out before driving it or will I be fine cruising around for a while. I imagine it is quite restricted from all of this oil and gunk blowing through.
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

Alphius
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Re: VF28 without engine management

Post by Alphius »

The reason why your car still runs at 10-11 even with the MBC in...

You can't force the wastegate to open at lower than wastegate spring pressure, so the lowest boost you can run with that turbo is the 10-11 psi. That being said, I personally think it will be perfectly fine at wastegate boost.

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Re: VF28 without engine management

Post by just-rust »

Why I didn't put that together... Thanks for pointing that out! It seems I am good at missing the obvious.
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

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Re: VF28 without engine management

Post by Legacy777 »

You will likely feel if the cat is plugged up. If everything feels ok, I probably would just keep an eye on it and see.
Josh

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2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm

just-rust
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Re: VF28 without engine management

Post by just-rust »

Just drove it for 3.5 hours this morning and there was no hesitation or lag through any portion of the spool or speed range. I should be good to go with this cat!

Thanks for all of the comments and advice!
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

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Re: VF28 without engine management

Post by cj91legss »

If you have gone thru turbos, I would look at other reasons besides the cat. Especially with the response you gave above. How do your banjo bolts look? did you look to see if there was anything clogging the holes?
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Re: VF28 without engine management

Post by just-rust »

I have thought about this as well. I know I am getting oil through the feed line because the banjo piece wasn't tightened into the line properly when I installed the 04 and I pissed oil all over. This was a brand new line from a kit as well. I have one new coolant pipe/bolt on the 28 and inspected the swapped pipe before using it. I did reroute my pcv line from where the F pipe usually came straight up as it looked like the 3/4" hose I was using was restricted from the bend I had to make.

Besides for that I assumed the VF11 went because of age and the TD04 had been sitting in the trunk of the car and in my basement for at least 4 or 5 years and blamed it on the fact it had sat for so long. I have been told that a turbo sitting for a long time isn't good after removal and assumed it was because seals dry out and weaken.

I also changed my plugs. My idle issues are gone this time around as well so I am hoping my changes have been done for the better. Will replace wires soon as well.

If you can think of anything else that might be a cause I am all ears. I would scratch a hole through my head if this turbo went!
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

just-rust
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Re: VF28 without engine management

Post by just-rust »

Another damn turbo oil seal blown. The 28 didn't even make it two weeks... It looks like my problems can't be blamed on bad seals anymore. I am at a loss.

Vacuum and idle were all normal. Boost reacted as it should have. No noises coming from the engine. Acceleration didn't feel restricted. I am very frustrated at this point.

I will start reading up on the topic and find a rebuild shop for this turbo. I still have a back-up TD04 to try once I feel the problem might be sorted out.

I am not sure what to look for. Any ideas would be greatly appreciated.
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

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Re: VF28 without engine management

Post by cj91legss »

Clogged oil feed line or banjo bolt.
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
98 LGT 4EAT
98 LGT Wagon 4EAT

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Re: VF28 without engine management

Post by just-rust »

I will pull it and check tomorrow. I just wonder about the amount of oil in the intake, wouldn't that rule out this possibility?
Rusty 1991 EJ22T - VF28 - '07 wrx TMIC - MBC - Invidia DP - Walbro 255 SOLD
1992 Legacy SS 5mt, with some neat stuff on it

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