Modern ECUs and Turbos...Need real input.

[CobraSix]

The following is a thread I created on a volvo forum, since I own one (had two but down to one now). Basically, my current car is a GLT model, which is a low pressure turbo, stock ECU runs to 5psi with a Garret 13G compressor. It's a 2.4L 5 cylinder, with a stock CR of 9.0:1. The T5 is a high pressure turbo (either Garret 15G or a6T), 10 psi stock, 2.3L 5 cylinder, and stock CR of 8.5:1. The blocks are identical. The only change is the T5 has different pistons to drop CR down, and slightly larger injectors. So with that in mind, see if you can make sense of my ramblings below. The GLT makes 190BHP and the T5 is at 236BHP.

To me, the T5 ECU swap seems pretty straight forward. What confuses me is the people who say the power won't be the same as a T5. My questions revolve around that.

1) Some people mention that a 13G at 10psi and a 16T at 10 psi will not have the same power on the same engine. Now, let's neglect the temperature part of the issue. I understand that a 13G may impart some more heat since it's a smaller turbo, but I haven't looked at the compressor maps yet to see where a 2.4L engine will fall in the efficiency curves of the 13G. Let's also neglect the increased CR of the LPT engine for this argument. If we follow those assumptions...isn't 10 PSI 10 PSI? Doesn't the ECU get the reading from the MAP sensor and adjust the wastegate on the turbine side accordingly to maintain the appropriate pressure? without factoring in temperature,10PSI of air should have the same charge density, no matter the turbo compressor size, correct?

2) Now, I understand the need to upgrade the injectors. Without getting into injector sizing math, I'm sure when you add 50% more boost (6.5 to 10) you may push the continuos duty rating of the GLT injectors. Cheap insurance. But some say that without the T5 turbo, the white injectors will cause you to run rich. Again, I don't see how this is true, but maybe motronic doesn't work like Megasquirt which is the reason I ask. On MS, you program target AFRs based on a number of parameters. Mostly, RPM and either MAP or MAF. Based on those inputs, the computer looks up in the table what the target AFR is and using engine presets guesses what it should be. If it's off slightly, it reads that from the O2 sensor and makes adjustments. I can see when under WOT you will run rich, but most ECUs default to rich in WOT anyways. So, if I install white injectors with a T5 ECU, it shouldn't have any problems since the MAF and MAP are still going to report pressures and flows to the ECU which will fire the injectors that it was designed for (white). If we agree that 10PSI is 10PSI (assuming same charge temp) then the MAP and MAF readings should be identical for 13g versus 15g or 16T. Am I missing something?

When I look at it, it seems that the LPT engine with a T5 ECU, 13G, and white injectors should perform better than, or at least on par with a stock T5 car. With a faster spooling turbo, the area under the power curve should be larger. And with the .5 higher CR, you end up with a little more power.

The reason I ask this is for two reasons. I like to understand everything about my cars. I love working and building cars. I owned a 98 S70T5 from 2001-2010. In 2009, I picked up a V70 GLT to temporarily replace my wife's mustang. However, I just can't seem to get rid of this car. I love the color and I just love the 98-00 styles. Runs great and love having no car payments. But...I do long for that extra 45 HP. I like the smooth delivery of power from the GLT's 13g, but want more of it. However, since I do use this for my daily driver during the winter and some during the summer I want to keep it relitively reliable. I do have an 04 Silverado that i drive some, but the mileage for my daily commute is rough. Seems like the T5 ECU and injectors would do great. I would likely eventually upgrade to the T5 turbo to complete the swap, but just curious about the true impact of not doing it, with all the information I've read.

Now, here are the compressor maps.

http://www.stealth316.com/images/td04-13g-jlspec.gif

http://www.stealth316.com/images/td04-15g-jlspec.gif

Ignore the VE lines, since that's for a different engine, just that was the only place I could easily find the compressor maps.

What I found with the 13G was this:

For 190BHP, I end up with a CFM of about 238.

At 5psi, you are around the 65% efficient mark, with making 190BHP with a compressor speed slightly under 120kRPM.

Assuming you get to 240HP with the 13G, you are actually around the 68-70% efficient mark (max is around 73%) with a compressor speed around 130kRPM, which is an increase of around 8%.

Now, with the 15G making the same power will be around 73% efficient with a compressor speed of around 115kRPM, which is about 12% less than the 13G at the same power.

The 13G was no where close to the upper operating edge of the compressor curve when operating at 240HP.

Seems to me that there should be minimal problems with the turbo. Sure, there will be slightly more heat, which will decrease the charge density some, but doesn't seem like that much.

Now, most people comment with this swap (without any dyno's) that they don't feel the power. I wonder if this is due to the nature of the smaller turbo. The T5 ECU in stock form limits the boost to 5 psi in 1st and 2nd to protect the transmission and limit wheel spin. The GLT obviously doesn't need to do this (same transmission). I wonder if it feels like less power only due to the fact the 13G turbo spools up almost instantly instead of the 15G which does have a lag and this it's like "OMGWTF going PLAID" power.

Problem is, the performance oriented volvo sites are populated by too many kids that watch F&F as reference material. The older volvo websites are full of people with no clue about cars. So I come here, to people I trust.

Also, I don't see any problems running 10psi with 9:1CR on an AL head, do you? Seems a fairly conservative thing number.

Regards

 

[Beemer+ford6lover]

well i would say with the aluminum head and premium fuel you should be fine. I do beleive that you are correct with the 13g operating more effeciently thats why they seem to feel less ommph. It spool up is more linearly. Now since I'm not sure about volvos since i have never worked with them, but your reasoning does seem very sound and an engine and how it operates is always very similar regarless of what kind of engine it is ( not including opposed piston 2-strokes and rotary engines). If i would do it i would install a AFR gauge just to check parameters and if you can possibly upgrade the raidiator just incase there is alot of extra heat produce. I mean your looking at 50hp increase possibly therefore higher heat. Now as for if just doing those things will get you to that same 240hp its hard to say even if the turbo is in a better effciency range the flow of the air will be different and the head design maybe different that'll cause discrepancies. But all things being equal i think your perfectly right.

By the way i couldn't get your link to work.

 

[CobraSix]

Odd.

http://www.stealth316.com/2-turboguide.htm

if you scroll down the page, it has the compressor maps.

The responses from the other website just remind me why I don't visit them for performance guidance. Got the generic "It doesn't flow enough" type responses when the maps clearly show that it does. Sure, it won't flow enough for 320-350 BHP, But I'm shooting for a modest 40HP increase.

Heat can be a minor issue, but the engine is already intercooled by one of the best stock intercoolers out there (in fact, many sites tell you to search out for volvo intercoolers for aftermarket turbo additions to any car), so can't imagine it would take too much away.

Guess I should just suck it up and set up a before and after dyno run.

But other temperature, I can't see how 10psi from a 13G (at 68% effecient zone) is much different from 10 psi from a 16G turbo (74%) other than the 16G will lag more though it would give more room for upgrades in the future. isn't 10psi = 10psi regardless of the source (within reason).

 

[Beemer+ford6lover]

looking at the turbo maps, the 13G is definately more than capable of pushing the 10psi that your looking for through out the rpm range. All its going to do is ramp up the pressure a bit faster with less lag. The only real thing i can see being a problem besides the before mentioned heat is how the pressure is developed, but The computer should be able to read the MAF sensors flow and be able to compensate for fuel and timing issues. I think honestly you could get 280hp out of it pushing it, maybe more with the the extra displacement you have. but not much more and would max out really at 15psi when fully pushed. I'm trying to pull all of my knowledge of turbos and things out of my head, my main experience is with turbo rotary's, but the principle are all the same. But the computer is designed for that 10psi so it should easily be feasible. I would love to see your results when your done. I sorry if i'm being repetitve, but this is pulling from old unused knowledge and it kinda goes stale at times if not used. whats the reline? I'm assuming between 6500-7500?

 

[thesameguy]

I don't know much about modern Volvos, but is the *only* difference between the GLT and the T5 the injectors, pistons and turbo? No cams or anything like that? (I've got a '98 V70 GLT, but never looked into more power short of a chip ).

Based on a lot of turbo swapping with Saab turbos, I'd wager the reason people don't feel the seat-of-the-pants boost with the smaller turbo combined with other T5 parts is that it spools quicker, so the increase in power feels more linear than with a big turbo that hits you harder, later. My 900T has completely different character switching between the stock Mitsubishi TE05 vs. the T3 stock on other 900Ts vs. the Turbonetics Super 60 vs. the T3/T4 hybrid on it now. The TE05 feels like not running a turbo at all compared to the hybrid. Actual performance at a moderate boost level is very comparable between them all (14psi = 190hp pretty much across the board), but of course that falls apart with more extreme tuning.

The reason I asked about the cams is that swapping between stock Saab non-turbo cams, stock turbo cams, and aftermarket cams also changes the feeling, even though the ultimate numbers (at moderate boost pressures) are very similar. Shifting the power band around on the rev range combined with turbo lag leads to some interesting seat of the pants results, however.

IME, if you aren't actually gunning for maximum performance you will have a much better driving experience from a smaller turbo that's just about maxxed out at WOT/redline versus a larger turbo that isn't. Although the hybrid on my Saab is fantastic on the track, delivering big numbers at high rpm, it's not nearly as much fun in town as the Mitsubishi, which was able to deliver full boost at 3000rpm. The hybrid is just thinking about doing something useful about then. You need to look at the driving you'll be doing and choose the turbo that is best suited for that range of operation. You're going to make some sort of sacrifice (e.g. mid range torque for top end power), so make the compromise that makes your car the most fun most of the time.

10psi and 9:1 isn't inherently a problem, but the rest of your tune will dictate whether it is or not. Cams, ignition timing, fuel, flow, intercooling all figure into that equation and you need to look at it as a system and not just collection of numbers. Like with choosing a turbo in the first place, I think your end goal will largely dictate other features about the engine. For example, you may want to run less boost in exchange for more timing, or a bigger turbo in exchange for a smaller (or no!) intercooler... Those decisions will also be based on your engine management, since there is less freedom in an ancient static distributor and a carburetor versus a modern computer with infinitely variable everything. The Saab is all '80s vintage electronics, so I have to fight a constant battle between too much boost and too little timing - I just don't have good enough control over either to give me exactly what I want. The Saab is peaky and finicky and sometimes feels like a bit of a chore to drive - my Solstice GXP on the other hand has virtually exactly the same components but pulls it all together with painless finesse. Assuming you're running this engine on older stuff, like the Saab you will have to tune more conservatively - less boost, less compression, less timing, etc. than is technically possible, simply because you don't have granular enough control to account for every environmental variable (ambient temp, fuel quality, etc.).

If you are looking for pretty solid info on turbos that may really be helpful, I would go hang out on turboford or one of the XR4Ti forums (merkursport is great). Lots of very knowledgeable people there who are positively not into keeping things stock, with an added bonus of good, fordsix-relevant Ford tech. Those guys have helped me build up my XR4Ti pretty effortlessly, and it's a daily temptation to put a 2.3T into my Falcon because that tech is so well sorted out these days. As much as I like turbo cars (have an Audi 1.8T too, heh) I sincerely plan on keeping the Falcon with its I6.

 

[thesameguy]

Man, I just reread your post and realized it *was* about Volvos, and not about some obscene fordsix swap.

There is zero reason why "T5 stuff" minus a T5 turbo would yield any different results than a full T5 conversion, given the turbo isn't operating out of its range. Ford fitted all sorts of different turbos to the 2.3T cars to get the feeling just right, and they all deliver identical numbers. Saab did the same. VW/Audi does the same.

T5 stuff on a non T5 car should yield better than T5 performance... whatever slight mismatch in turbo efficiency exists should be easily made up for by the increase in compression. Chances are you'll have a much nicer to drive car, since off-boost performance will be improved by the increase in compression ratio with no sacrifice in on-boost performance (unless you get knock, in which case use better gas ).

This does lead me to ask: Why do this? Why not just chip the Ovlov, throw on some water injection, and call it a day?

 

[CobraSix]

Well, a few reasons, biggest being price. Even a chip ECU reflash is around $400 for the brick. I can get a T5 ECU for $50. Both are tuned for 10 psi. In my uneducated modern ECU mind, should be fine. I know the ECU is more concerned about Mass flow than MAP, and watching the A/F ratio, so in my mind, it will compensate based on the maps. the ECU is also controlling the wastegate based on its programming and pressures. Just, to me, air compressed to 10 psi has the same density, no matter the turbo that compressed it. Granted, heat is a factor, along with the turbo's ability to handle it. But, if some of the ECU reflashes push boost on the GLT to 12 psi, how is that any different than running a T5 ECU that goes to 10? Maybe there is, I don't know. Sure, timing and more aggressive fuel maps will usually accompany a reflash.

I had a 98 S70 T5. Loved it. You definitely felt the turbo spool up. The GLT has much smoother power delivery. Basically don't ever feel the turbo spool. Just one smooth power delivery, which I must admit, I actually like better than the T5's delivery. I like predictable power, especially when having a little fun on the twisties (as much as you can in a turbo brick).

From what I've gathered, the only difference in the T5 and GLT engines is the pistons and turbos (and ECU). Cams are the same. I remember at some point they said the T5 block wasn't bored out as much (2.3L vs 2.4L) but can't find that reference. Oh well, worth a try. Worst case, I'm out $50.

 

[thesameguy]

Just, to me, air compressed to 10 psi has the same density, no matter the turbo that compressed it.

I understand what you're saying, but obviously this isn't true. Otherwise, you'd have the same turbo on a Chevy Sprint Turbo as on a Kenworth. A given compressor has a range of efficiency, and operating outside of that range yields diminishing returns. Whether it's a compressor that isn't moving enough air at low speed (lag) or a compressor that's not moving air efficiently enough at high speed (heat), you'll have an undesirable reult. On the Volvo, I *highly* doubt there is a real difference in maps between a 6psi GLT and a 10psi T5 - whatever actual turbo differences exist are the result of Volvo getting the driver feel "just so" rather than true technical limitations. It's certainly not something I would worry about.

From what I've gathered, the only difference in the T5 and GLT engines is the pistons and turbos (and ECU). Cams are the same. I remember at some point they said the T5 block wasn't bored out as much (2.3L vs 2.4L) but can't find that reference. Oh well, worth a try. Worst case, I'm out $50.

I don't know about the guts, but the T5 is 2319cc @ 8.5:1 and the GLT is 2435cc @ 9:1. At the same boost level - given everything else (cams, intercooler, fueling, etc.) is equal - a GLT is going to be quicker - especially off the line - than a T5. Bigger displacement and higher compression! Personally I would move the entire fuel injection system over - MAP, AMM, injectors, ECU - to ensure the ECU has the components it's designed to work with. ECUs are invariably calibrated to these components, and if they don't match you will get some combination of bad performance, check engine lights, or total destruction. A little extra displacement and compression and a slightly wrong turbo should be well within the ECU's ability to compensate if everything else is ok.

10psi & 9:1 was nothing special even in 1998... Saabs were running 15psi & 9.25:1 in 1991 on the 2.3l fours! I think you'll be totally fine. And fast.