524td build, minus the d

[turbodan]

The subject:







A 1985 524td with 89k on the odometer, seems to be in good overall condition. Alpine white like my first e28 dating back to 2003ish.

The motor is pissed off and I'm not interested in becoming a diesel specialist so I will be converting it to gas and installing this M20:



Today I ordered a turbo, a bit larger than the other build. It's a GT2971R with the 90 trim turbine and .86 AR housing on the hot side. It's in between the GT2871R I used at one point in the past and a little shy of the GT35R I ended up with on the old build. Theoretically it should be capable of 400+ RWHP, though the turbine side is about 10% smaller than the 35R that I previously achieved those power levels with.

300 rear wheel would be perfectly fine, and if need be I can push it up from there.

[gadget73]

are you going to name it Ken ?

[turbodan]

I have not seen the Barbie movie, that may be a prerequisite for that joke.

Perhaps I'll substitute Dan for Diesel. Keep the original badging.

[gadget73]

I haven't seen it either but my slightly older cousin was a Barbie fanatic when we were kids, and at some point I became aware that Ken was not exactly anatomically correct.

[turbodan]

The name would be appropriate, this 524td is not going to be anatomically correct for long.





This is the previously mentioned GT2971R fresh off the FedEx truck. This is the absolute largest turbine and compressor combo available in this T25 frame. Very compact with plenty of flow.

[turbodan]

A clutchmasters segmented kevlar clutch. On sale at Bimmerworld, which is a place I have never heard of or bought from. They had it on the shelf for a very good price. I highly recommend giving them a call.

[turbodan]

This project is finally getting some progress. Since the engine that was destined for this swap ended up being needed for the other car, I've been trying to figure out a course of action. The block I have, the original engine that came out of the other one, is substantially scored in multiple cylinders. I did harvest the super ETA pistons, rods and crank. These all should be usable with some cleaning up.

That motor was definitely beat, as the rod bearings show:



All things considered it is a pretty poor candidate for a build, so I eventually sourced a spare M20B25 bottom end. I could either swap the super ETA stuff into this B25 block or just refresh the B25 and use it as is. Displacement really isn't a big factor with forced induction, especially a difference of 200cc's. The B25 actually revs better than a super ETA based stroker too, which is just a matter of engine dynamics when only changing displacement. Same intake, same valves, better breathing at high revs. I tested a B25 back in the old days and it ran very well as far as I can remember. The only thing that gives me pause about making any changes is the amount of effort that went into the current tune and the truly excellent result of that. Some time will be required to adjust the fuel tables but it certainly could be done.

Currently I'm stripping the B25 down for a thorough cleaning, honing and inspection. I still need to pull the M21 out of this diesel but there's no reason not to get the M20 fully situated before proceeding.

[turbodan]

I spent a few hours yesterday moving this car closer to the house, right up behind the garage where I can get started.

Today I pulled the turbo and manifold off. I was somewhat intrigued by this stock turbo, specs have always been hard to come by. Now I know that it is a T3 50 trim compressor mated to a 47mm turbine wheel inside of a very small A/R turbine. Of all of these specs, the turbine A/R is definitely the main issue for anyone considering using one of these on a gas engine. A much larger A/R housing would uncork the hot side and allow this thing to reach the potential of the compressor, which looks like it should be good to at least 250rwhp. Suitable for a low boost system on a 2.7 or smaller engine. 250 rear wheel is nothing to sneeze at, that's almost 300 at the crank.

The external wastegate is interesting as well, being vacuum operated. I actually might try this thing out to improve efficiency during cruising. It would be open at idle and part throttle and close as soon as you put your foot into it, at which point the entire volume of exhaust gas would be routed through the turbine until the main wastegate opens. I'll have to determine exactly what vacuum level this thing opens and closes at. It would be useful if it stays open until about 60 or 70 kpa.

[Punnzzells]

Start of another great build thread.... will be following this one.

[turbodan]

Updates. Not much though.

I recently backed into this thing with a case 280 while doing some dirt work in the yard. This thing then bounced backward and into the west facing wall of my house. Did a number on the master bathroom. Car sustained only a little damage to the front bumper. The house was worse. Sure didn't take much to push that wall in.

I have been working, going to school and remodeling the master bath over the last few months. Garage time has been expended on two wheeled projects. This car needs to get going though. I have two M20B25 short blocks, three heads, a couple of these td manifolds and a couple of turbos laying around. All of the ingredients are on hand, I need to cook.

Next semester will be organic chemistry, which is expected to suck, but I won't be working so I should be able to get some shit done. It would be very nice to at least get the engine and transmission out.

[tig]

Love this!

[turbodan]

About time to get a motor ready.





In my free time I've been looking at these blocks I've got on hand, looking for a candidate for this 524td. The block that came out of the 88 has substantial cylinder wall scoring. The B25 block I picked up over the summer has less substantial but still significant scoring. The B25 I picked up complete for $100 a couple months back also has some cylinder wall damage. The only good block I seem to have is in the 88. 

The solution is a set of .50 over M20B25 pistons. If I could have found a set of oversized super eta pistons I would have used those. It's all good though. The B25 makes good power and torque, and better top end than the super eta stroker. The 8.8:1 CR is still good for boost and probably a little better for off boost drivability. 

[Notae30]

About time to get a motor ready.





In my free time I've been looking at these blocks I've got on hand, looking for a candidate for this 524td. The block that came out of the 88 has substantial cylinder wall scoring. The B25 block I picked up over the summer has less substantial but still significant scoring. The B25 I picked up complete for $100 a couple months back also has some cylinder wall damage. The only good block I seem to have is in the 88. 

The solution is a set of .50 over M20B25 pistons. If I could have found a set of oversized super eta pistons I would have used those. It's all good though. The B25 makes good power and torque, and better top end than the super eta stroker. The 8.8:1 CR is still good for boost and probably a little better for off boost drivability. 

Looking good

[turbodan]

Been getting a lot done lately with this thing. Pulled the tranny today, along with the driveshaft, starter, ac compressor and power steering pump. Head came off the other day. All the diesel that's left in the car is the short block.

The only casualty was inflicted by the crank pulley while removing power steering bolts. It's always something. 

[turbodan]

It is a 524 no more:



I have a block stripped down and ready for the machine shop. I can still lift these. The old back is hanging in there. 

Got a new cam too. The Febi 03068 seems to be discontinued and completely sold out. Germany is too busy building shit to blow people up in Ukraine I guess. I did find some Febi M20B25 cams overseas, likely the non-cat variant. Apparently that's what it's going to get:




Probably not a big difference between that and what Ive run in the past. It should work just fine. I thought about a schrick 272 but didn't take the jump. No need to change the recipe, it makes more than enough as is. I also dont want more lift, which means more stress on the valvetrain. No need for this sort of compromise with boost. We're not relying merely on the atmosphere to fill these cylinders.

[turbodan]

Fresh from the machine shop. Bored, honed, deck resurfaced to ensure flatness. Its time to get it on.

This bottom end was actually in pretty nice condition. The main bearing shells were perfect, zero wear. They will be reused. I need to clean up the crank, rods, and various other components that reside within the sump. Then it will be assembled.

I will almost certainly use the existing head I have built, with the catcams turbo cam. I'll build another head with this euro b25 cam and keep it on the shelf.

 

[marc79euro645]

lookin good!  better ride that kx before it gets too hot
sports cars and dirt bikes are my favorite toys
oh yeah boats too

[turbodan]

The KX is a ripper. Next to that is the '75 RD350, which is next to the '02 FZ1.  Too many toys...

[turbodan]

 

 

Found an interesting factory defect whole preparing these B25 rods. That bushing was installed 90 degrees out, obstructing the lube hole.

I suppose it's possible that it rotated in the rod at some point, but it seems very unlikely. 

[jdb]

Well that sure pissed off the piston pin I am sure!
Dan looks like the rod might have slightly turned color (hot) at that area from the looks in the picture??

Jeff

[turbodan]

That is possible. It sure looks blued in the pics. I have another rod on the way to replace it, so whatever it's condition it's a wall hanger at this point.

[turbodan]

Block is about done



I had to do something different with this one, something I've never tried before. I was considering a short runner intake of some kind, the M20 likes to make a bunch of power in the midrange with the B25 manifold. Lots of torque and cylinder pressure, hard on clutches and head gaskets. A shorter runner manifold would likely mitigate this midrange blast, so I figure let's give it shot.

Upon research, I find that there are few options available in 2025. There is a cnc machined dual injector manifold for about 2k. There are a few cheap and poorly designed Chinese manifolds. Option number three was an e21 323i manifold, which I've never had my hands on and know very little about. It does have significantly shorter runners than the B25 manifold though.



As these are exceptionally rare, I had no choice but to buy one just to examine the feasibility of using this with a motronic fuel rail. Originally they used k-jetronic and was never designed to fit efi components.




Interestingly enough, these manifolds use a much larger plenum than the Motronic manifolds. It is wedge shaped with the larger portion on the throttle body side. The plenum and runner shape definitely preclude the usage of standard EV1 injectors, but I believe the DEKA V short body injectors will fit. I have ordered a couple to see how it works. The distance between the lower edge of the injector sockets and the manifold is about 35mm. I can grind and clearance the manifold significantly if needed. The k-jet injector holes in the manifold are about 1mm larger than the standard injector holes but Im fairly certain that I can make this work with a small sleeve.



These runners are about 14.5" to the flange at the cylinder head. Figure another 1.5 or 2 inches to the valve seat for a total length of about 16.5". Should be optimized for about 6000 RPM. The B25 manifold is about 18", plus the distance through the intake port. Optimized for about 5000 RPM. It'll make a difference but it is hard to predict exactly what it will run like.

Hopefully I can get it sorted out and we will see soon enough.

[turbodan]

They fit. These are 30mm shorter than the standard injectors and the fuel rail goes right in. They are very small. I presume there are functioning electrical components and a compact injection valve in there. Seems hard to believe these are real parts though.

[turbodan]

Port matching the e21 intake to the 885 intake ports. These intake ports were 33mm in diameter, seems small but even on a 2.5 liter engine that's only 416cc per cylinder. Doesn't rev exceptionally high either, even if I'm spinning it up to 7k.

The B25 runners are longer and larger in diameter. I suspect this e21 intake will roll over relatively quickly after peak power. No way to know for sure until it's running though.

[turbodan]

 

Another item checked off the list. This turbo uses the largest turbine wheel that could fit the T25 housing, which requires substantial machining of the five bolt GT discharge flange to match the diameter of the turbine housing outlet. Perhaps someone makes one that has already been hogged out but I didn't find one. Now I can make a downpipe.

I decided to use two wastegates on this build. I have a hypothesis that the fouling effect the internal wastegate has on the turbine outlet is significant at high RPM. I will be using a 38mm tial external wastegate for initial spoolup, which will determine the boost pressure through the 4-5k range. I will dial in the onset of boost creep by limiting the travel of the wastegate valve. Boost will begin to climb toward higher RPM until it hits whatever maximum I'm looking for, at which point the internal wastegate will open to regulate boost.

In addition to the double wastegate setup Im going to build a divider into the downpipe to extend the turbine outlet further before it has to join the flow from the internal gate. This will help straighten out the flow from the internal gate and reduce turbulence and interference at the turbine outlet. By the time the flow merges downstream the two sides will both be moving in the same direction.

With the external gate handling the majority of the flow I think this will maximize turbine efficiency. If it works just right I might even be able to go with a non-wastegated turbo and ride the creep like I did with the original build.

Off the bat I'm thinking I'll run 1 bar on spoolup and shoot for 1.3 at maximum. Garrett does make a 1.5 bar internal actuator that will probably be right on the money for 1.3 at my altitude.

[turbodan]

It took quite a while to get this sorted out. A few more welds are required to finish but all of the fabrication is done.




I had a segment of pipe that fit right over the initial piece immediately after the turbine outlet. This extended the isolated segment of the turbine outlet to about four inches. This piece flares outward to a final inner diameter of 2.5" before opening into the 3" section where it merges with the wastegate flow.



Hopefully it makes a difference. As far as internal wastegates go I think it's pretty ideal.