Turbo ETA build

Discussion pertaining to positive pressure E28s.
turbodan
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Turbo ETA build

Post by turbodan »

I have been dicking around for months with this, not wanting to spend the money and putting it off. Now the money has been spent and this party is officially started. As per the original plan, this is a reprisal of the original build from 2006. GT2560R, 524td manifold. Unlike last time, this build will be running Megasquirt from the beginning and the motor will be 100% stock super ETA.

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One shortcoming I discovered along the way was intercooling. The original intercooler was too small to effectively control IAT. The new build is utilizing a 23x11x2.5 core which is about twice as large as what I started with last time.

Between the increased intercooler size and the standalone injection this thing may be able to put down 240-250 rwhp on 7 psi. The ETA top end is a wildcard, I don't know what to expect. If it is down on power I'll go ahead and install the 2.5 cam and intake. I have come to appreciate the outstanding low end torque of the ETA. It will be interesting to see what it does with forced induction.
Last edited by turbodan on Feb 14, 2023 4:57 PM, edited 1 time in total.
Galahad
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Re: Turbo ETA build

Post by Galahad »

very cool, looking forward to seeing how this goes
turbodan
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Re: Turbo ETA build

Post by turbodan »

With the stock injectors, megasquirt was hitting about 60 percent duty cycle. Perfectly fine for a stock engine, no good for adding boost. The first injectors I came across were on an M30B35 at the local junkyard, in an utterly demolished e34 535i. These are 18 lb injectors, still marginal even for modest boost with a low rev limit. Then I found some Saab injectors on ebay for a good price, so I ordered them up. These were 22.5 lb/hr which should be more than enough for 7 psi under 5500 RPM. When they arrived I was a little disappointed by their condition, but these injectors are usually pretty bulletproof so I cleaned them up and slapped them in.

I ordered eight, used the best six. This one didn't make the cut, though the rest didn't look much better:

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With these in I dropped my req fuel from 20.3 down to 13.2 and now I'm under 40% duty cycle. Ready for boost. These are the later four hole variety and they seem to run a little better than the original injectors, though I wonder if the shorter pulsewidths help keep more of the fuel atomized. I suspect the longer pulse from the smaller injectors just results in a lot of the fuel hitting the port walls and pooling up.
Nebraska_e28
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Re: Turbo ETA build

Post by Nebraska_e28 »

Subscribed!
I recently yanked the motor in my 82 528e & planned to swap in an m106 w/turbo.
Recently, I contemplated a super eta motor on boost. Fun play toy but decent mpg for DD status I'd hope.

Your top post pictures aren't showing.
I've never seen a 524td manifold. Pretty restrictive or decent flowing for what it is?
turbodan
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Re: Turbo ETA build

Post by turbodan »

Shit. Google may have noticed that I was using a backdoor for public hosting. I may look into a plan B for that.

The US spec td manifold is not bad. First one I used back in 2007 was the european non-AGR manifold. No wastegate provisions, T25 flange. That thing was pretty small inside and I hogged it out quite a bit. This time around I'm using the far more common version you find in the US, T3 flange with the wastegate flange on the side. This manifold is much larger in the collector where the two banks converge in the middle and turn upward. No hogging out required, though the same notching and port matching at the head are still necessary. I wouldn't hesitate to dunk the GT35R on this thing if it comes to that, I expect it will flow just fine. As long as it's larger in cross section than the A/R of the turbine I imagine it won't present a major restriction. With the GT2560R, the smallest area of the td manifold is about twice the size of the turbine. That's not accounting for the wastegate area either.

All I really need to do at this point is fab up the charge plumbing and mount the intercooler then build and exhaust. Can't do much with the exhaust until the rest of the stuff is bolted in. There is a reasonable chance this thing is making boost by April, though I haven't ordered pipe yet. Still looking at options. The plumbing on the intake side will be 2", same size as the compressor outlet flange. I expect it will be easier to route that through the body than the 2.5" I used last time.
Last edited by turbodan on Feb 14, 2023 5:12 PM, edited 1 time in total.
turbodan
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Re: Turbo ETA build

Post by turbodan »

Rehosted the original pics, and here's some more of that manifold.

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Shows some of the details regarding the notching. I have yet to test fit it to a real live cylinder head but it is matched to a gasket and should be pretty close. May only require minor fitting to slide over the studs. Reliefs must be cut in certain spots to get a nut threaded in addition to the notches.

I will probably install an external wastegate in addition to the internal wastegate on the GT2560R. Would be interesting to experiment with keeping a wastegate open while running at low to moderate loads instead of running all of the exhaust flow through the turbine. I suspect the OEM's are doing that with their electronically controlled wastegates. Seems like it might improve efficiency off boost. Doing it electronically is cheating though, I would rather see if it can be done entirely off of manifold vacuum.
Nebraska_e28
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Re: Turbo ETA build

Post by Nebraska_e28 »

Unsure if it's been asked before, or if I asked and forgot...
What made you choose the m20 platform over m30?
Also, with your previous build did you ever test what you could achieve for max mpg? If so what were those numbers?
turbodan
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Re: Turbo ETA build

Post by turbodan »

I've always liked the M20. The M30 is heavier and less fuel efficient. The M20 with the 2.5 top end makes great high rpm power too, whereas the M30 requires more extensive modification for that 6000 RPM+ power. My 2.7i with the GT35R was making peak power at 6400 and it was hanging onto something like 90% of that until 7000. Full boost at 4000 and nothing but fun from there on up. That was probably my favorite aspect of the small six.

As it turns out it's a great motor for boost in terms of durability too. The smaller bore diameter helps avoid detonation and I think the super ETA/2.5 combustion chambers seem to help a little more. I may be mistaken but I think the M30 head gaskets are more delicate. I was doing very well at 21 psi with a stock gasket and head studs. I believe the M30 needs an MLS to approach those boost levels and then you have the usual MLS stuff to deal with. I've had hit and miss results with those, including one that failed only after a buyer had flown in from goddamn Michigan to buy the car and drive it back.

MPG was in the 20s. Best I ever saw was 27. Surely could be better with a more careful tune. This time around I will be using a narrowband 02 sensor for closed loop operation. Easy MPG there.
turbodan
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Re: Turbo ETA build

Post by turbodan »

Made a block off plate for now to cover the AGR flange. May use it to adapt a tial wastegate later on. Bonus feature includes a third leg sticking down that allows the whole assembly to stand up properly on the bench.

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Intercooler is mounted:

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Plumbing is mostly finished and I have the first portion of the downpipe made:

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jacobthegoat
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Re: Turbo ETA build

Post by jacobthegoat »

That Intercooler looks like it fits perfectly. Curious how you’re going to plumb up to the intake. Relocating the battery?
turbodan
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Re: Turbo ETA build

Post by turbodan »

It is routed under the battery tray and comes up right next to the power steering pump. The 2" piping fits nicely.

The oil drain tube required some improvisation. Wouldn't feel right not to use JB Weld here:

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The oil feed will replace the oil pressure switch:

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This part has a restrictor built in. I felt better about locating the restriction at the other end of the oil line so I drilled this one out. I was concerned about cold winter starts with 20w50 taking a little while to get oil all the way through the oil line.
jacobthegoat
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Re: Turbo ETA build

Post by jacobthegoat »

Definitely following this build. I’ve been picking up parts to turbo my 528 next year and you’re one of the few that has done it the way I want to do it. My biggest questions were downpipe and intercooling so I’m excited to see how this goes. Are you keeping your A/C? I can’t tell if it’s smushed between the Intercooler and radiator or not.
turbodan
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Re: Turbo ETA build

Post by turbodan »

AC was sacrificed to the boost gods. It could certainly be retained if you work around it. Water to air intercooling is one way to do it, compromised placement of air to air coolers can work as well. I have had surprisingly good results with them leaned over almost horizontally. They can be run in series too, despite all the internet people poopooing on it. Low IAT is the most important thing, whatever it takes.
tschultz
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Re: Turbo ETA build

Post by tschultz »

Thanks for sharing, nice placement of the IC.

I have a similarly sized IC but in the same location for my 535i. Did you remove the power steering cooler loop in front here? It inhibits a bit of clearance in the nose area.

I am trying to fit my piping without cutting a euro valance and it is looking really tight if I try to keep euro fog lights and not cut the sheetmetal. Slow progress before I finish building M30B35 and swap it in...

I have wondered about IC's in series and it seems like it would work. Glad to hear you have tried it with some success. You could theoretically remove the battery or charcoal cannister and put one there behind the headlights for an additional cooling function.
turbodan
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Re: Turbo ETA build

Post by turbodan »

I did not know the M30 cars had a power steering cooler up there. The M20 does not. Must be on account of the vacuum brake booster. All the PS pump runs on the small six is the steering box.

I also wanted to fit the plumbing underneath the valance, so I had to mount the cooler high enough to route the pipes above the tow loops. I haven't tested the fit yet but I'm pretty confident that it'll clear without modification once I beat the big-ass dents out of it.

In a perfect situation you would mount the intercooler up front with lots of flow through the core. Even with compromised placement though they can still soak up a lot of heat before your IAT starts to climb. Depending on how long you want to hold the throttle open on a top end pull, might not be an issue at all. Last time around, when I mounted one up front like this I thought it would be sufficient by itself to control IAT with the core mounted directly perpendicular to the air flow, up front with minimal obstruction. I ended up reinstalling the intercooler in series that I had located under the charcoal canister, which was nearly laid down flat with only slight inclination toward the airflow. Even though the second cooler was smaller than the main cooler and exposed to very little flow through the core, it completely resolved my IAT issue. It went from climbing steadily while under boost to staying within ten degrees of ambient at all times, even on the dyno. I think I was seeing 130+ with just the single cooler in place of the condenser. That's a substantial and worthwhile reduction.

That was also running 21 psi, so there was quite a bit of hot air mass to take care of. At lower boost I'm thinking this single cooler in front should get the job done.
turbodan
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Re: Turbo ETA build

Post by turbodan »

Plumbing is almost entirely finished. I added provisions for idle air control and the recirculating diverter valve. The oil drain fitting has been installed and there is really nothing holding the project up. I may pull the exhaust off and do the installation this weekend.

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All I'm waiting for is a big box of 3 inch mandrel bends from FedEx. Delayed inexplicably and currently unaccounted for. I have that roughly ten inch section of downpipe already so that may have to do for now.
turbodan
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Re: Turbo ETA build

Post by turbodan »

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This is where I leave off for tonight. Apparently I will need to order a wastegate actuator bracket to reclock the compressor housing. Clearly the outlet is too close to the inner fender. No other issues though once I got that god damn manifold to slide over all 12 studs.

While fitting the manifold I discovered a neat trick with a carbide cutter. Turned up to 20000 rpm it cuts flesh effortlessly and cauterizes at the same time. Should be interesting to see how this hole in my finger heals up.
Nebraska_e28
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Re: Turbo ETA build

Post by Nebraska_e28 »

:oops:
turbodan
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Re: Turbo ETA build

Post by turbodan »

https://youtu.be/gjIuUB9XMJU

https://youtu.be/VeT1uNJ6VPo

It is running. I have a few minor things to button up before the test drive. The ignition coil needs to move, along with the coolant reservoir. It is alive though and nothing is leaking. Sounds healthy, and that little turbo is blowing some serious air even just revving in neutral. You can hear it in underhood video, apparently the plumbing was was aimed at the phone. I like to do that first startup with the coupler off just in case there are any loose bits of debris that can blow themselves out, rather than into the intake.

I am excited to see how low it spools up. I can't remember exactly what the 2560R did on the 2.7i back in 2007. It is entirely possible that it makes full boost by 2000 RPM.

All in all it's looking great. I am stoked.
turbodan
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Re: Turbo ETA build

Post by turbodan »

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It is done. Makes boost at very low revs, below 1500. I think I should have gone bigger on the turbo but it's certainly not bad. GT2860R with one of the larger AR turbines looks good. If I ever put a B25 cam and intake on this thing, that will be done in conjunction.
M. Holtmeier
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Re: Turbo ETA build

Post by M. Holtmeier »

Sub'd for more videos! :haul: Full Boost by 2k rpm would make for a nice street car.
turbodan
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Re: Turbo ETA build

Post by turbodan »

In the next week it will be getting an exhaust system and then I can begin tuning. I have no idea what the AFR looks like, should be pretty rich. I'm seeing surprisingly high duty cycle numbers so larger injectors may be needed. If anybody has some laying around I'd love to take them off of your hands. 30lb/hr would be plenty, 42lb would work as well. I need some breathing room on that duty cycle, one way or another.

Looking at datalogs, its making 4 psi by 1500 RPM, 6 by 1700. The wastegate starts to open at about 6 psi but boost creeps upward with revs. By 3600 RPM, which is as high as I've run it, it's up to 9 psi. Here I find myself wondering, was it doing this last time and I just didn't know it? I was running Motronic with the original system until the point where I could not make it work. Couldn't datalog anything until Megasquirt came along. Once I get the exhaust done and I can work on tuning I'll explore the limits a bit more. Can't tell if it's detonating, open downpipe is just too damn loud.

It hasn't purged any coolant yet so that head gasket is hanging in there. Seems like it should be very hard to pop anything at these boost pressures.
turbodan
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Re: Turbo ETA build

Post by turbodan »

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Exhaust in progress.

I found some 30lb injectors out of a Buick that should be here today. Bosch 0 280 150 934. I'm still trying to figure out why my duty cycle was hitting 96 percent at 3600 RPM and less than 10 psi. That should have been pig rich but it felt good.

I found an old post from TCD stating that 24 lb injectors supported 265rwhp in his B25 test car. 30 lb should be good for in excess of 300 rear wheel, and I should be nowhere near that with a turbo super ETA at current boost pressure.

I did notice something interesting looking at datalogs for the NA super ETA. Manifold absolute pressure reaches a minimum at 5100 RPM. From 5100 to 5300 it begins to slightly climb. This indicates peak airflow and thus peak horsepower occurs at 5100 RPM. This is much higher than the 4250 BMW claims and it does change the calculations for peak hp at a given boost pressure and required injector size. My original 2.7i motor with this turbo made peak power only a little higher than that so this super E might not be too far off the mark.
turbodan
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Re: Turbo ETA build

Post by turbodan »

The exhaust is done and I got some tuning in today. Boost is definitely creeping up. The wastegate opens at .5 bar and by 4700 RPM it's up to .79 bar. Pulls pretty good though.

Injectors have become a real pain in my ass. I popped the 30lb set in, had a dead cylinder on startup. While I let it run to see if it smoothed out, I noticed fuel leaking from the injector body on at least three of these. Number six had an actual stream of fuel shooting out of it. The original rusty, crusty Saab injectors went back in. With the wideband hooked up, I was able to pull quite a bit of fuel back out, it was running very rich. This got my duty cycle back down to a somewhat acceptable range. Next move will be some legitimate, brand new injectors. Seems like it is damn near impossible to get good, used stuff on ebay anymore. Nothing like it used to be.

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Next stop is the gas station. It's running on 87 octane and I had to take a bunch of timing out to control det. Hopefully 91 improves this.
Dagamus_NM
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Re: Turbo ETA build

Post by Dagamus_NM »

Subbed, glad to see this going down.
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