For those still following my project, I have crossed the Rubicon. Not the famous trail in the Sierras, but in choosing which fork in the road to take in resuming my turbo project. I think it will be helpful to detail the issues one faces in adapting a turbo to a 196 mounted in a Scout II. Here are the good and the bad, summarized from all that has gone before in my build:
First, the good. I ended up with a turbo that worked quite well. In the runs I made, I discovered, through the datalogging feature in the Megajolt/EDIS crank fire ignition system I was using, that I could get boost as low as 1,800 rpm, and could pull a minimum of 8 lbs. I say minimum because at that particular measurement, I had "run out of road" and it was still pulling, and at that using a restrictive Carter sidedraft carb. With my fresh rebuild, I was only able to crest that grade at 45 mph, in third gear (T19 narrow). I think that calculated out to around 3,200 rpm with my 3.73 gearing. With 8 lbs. boost I hit that same point at 65 mph, in high gear. That is a substantial improvement by any standard. In short, performance met my expectations. Also through datalogging, I determined I was running an A/F of 11.4:1 under boost, so that was also where it needed to be. This all tells me that the turbo was properly sized and that with minimal tinkering, good A/F could be had under boost.
Second, the less than optimum. Scout II's don't have large engine bays and airflow through them isn't really all that great. In running the 152T manifolding, the airflow through the passenger's side was pretty much gone. The turbo was very close to the underside of the hood and had I kept that arrangement, I was planning on cutting out a section of that under hood reinforcing web, and seriously considering cutting a hole in the hood and grafting in a "blister". The fit of the turbo's outlet pipe was also quite tight, and put a tremendous amount of heat into the passenger's side firewall and foot well even though it was wrapped. So much so in fact that the dynamat style pads I had installed had melted. That was unacceptable. I was imagining solutions that would have involved clearancing the inner fender, etc. That would potentially reduce clearance with the front tire in a hard right turn. Running the larger (2 1/2") exhaust pipe under the bell housing and maneuvering around the clutch linkage was also problematic. I did it but wasn't happy with it. Since I put in a D300, another possibility would have been to simply run the pipe straight back on the passenger's side but that wouldn't fix the tremendous heat load on the passenger's side firewall, etc.
This all brings me to considering mounting the turbo on the driver's side of the engine. Two examples, with a few pictures and a short video, of this approach have been seen recently on BP. I reached out to one of the parties and have learned additional details of how they did theirs. They were both "blow through" systems that now run EFI. One runs a generic T4/T3 turbo, the other I haven't been able to learn more about. I have no idea what trim levels or A/R ratios are involved with either turbo. What I do know are that these are Model 800 196 engines mounted in either Model 80 or 800 Scouts. Those engine compartments are markedly different than that of the Scout II and also have major differences in ancillary equipment, or lack of (power steering, power brakes, for example). The Scout II "double sump" oil pan is also a major difference from the front-sump 80/800 pan. As the pipe that feeds the turbo must come under the oil pan, this difference is significant. Their pipes cross under in the relatively shallow portion of their pans and pose no clearance issues with the front axle. A pipe coming under a Scout II pan must pass through the "notch" placed there to accommodate the motion of the front axle. A solution to this I've puzzled through is to clearance the rear of this notch ("notching the notch") so that the pipe will clear the axle, which would articulate forward under extreme flex, assuming stock shackle location. The turbo itself is mounted to a simple bracket bolted across the large boss that the now-unneeded mechanical fuel pump previously bolted to. Easy-peasy!
Turbos have successfully used cross-under (and cross-over!) pipes to feed turbos for years, so this approach isn't unique here. So what about the intake side? Those two conversions both had their turbo intakes facing forward, with large intake tubes and air filters mounted either to the driver's side inner fender where the Scout II battery was located, or somewhat free-standing in the area where the Scout II P/S pump is located. There were variations on getting the compressor outlets coupled to the carb or throttle body "hats". It is a very busy, comgested piece of real estate, complicated by the 196 T-stat bypass hose. Moving my battery isn't an option and I don't care for the other solutions. After giving this a lot of thought it occurred to me that I was coming at the problem backwards. I asked myself: Why do I assume that the turbo must have its compressor section mounted forward? And the answer was easy:
Turbos don't have a front or back! So for the past few weeks I have been taking measurements and trial-fitting up a left over TRW center section and turbine housing and believe that this is the best solution for me. The space I have to work with goes from the rear outrigger of the Scout II 196 motor mount, to the rear of that horizontal "shelf" protruding forward from the back of the block (has numbers cast onto it). If I cut off the mount outrigger, and weld it to the forward edge of the bolt tab it was cut from, I can gain about another 1 1/2". From this new surface to the rear of that "shelf" I have 17 1/2" to work with. Within that distance will be the forward edge of the turbo outlet pipe, and the rearward edge of whatever vertical compressor inlet piping I come up with. There should be much more room available for a carb or throttle body in the area to the right of the P/B booster (between the booster and engine) and the firewall rear of this.
The turbo itself will need to be quite compact. In a recent discussion with a friend who trafficked extensively in turbos, I laid out these issues. He said that since I once had a TRW turbo that performed exactly as desired, why reinvent the wheel? (disclaimer: he no longer runs old turbos and has gone "modern"), but kept coming back to simplicity and going with what you know works. What kind of nailed it for me was the fact that I started looking at the physical dimensions of a variety of turbos, and the distance between the TRW turbine outlet face and compressor inlet face was tough to beat - 6 3/4". In contrast, a GT2252 is 10.6". Those are precious inches lost. Add the plate to the turbine to which to mate the exhaust pipe, and I'm already running out of room. I got tired of chasing my tail on this and after a search, turned up two Rayjay F flow turbos that had been rebuilt years ago, put in storage and forgotten. I had the B flow turbine needed to give me the quicker spooling, so after the Rayjays arrive next week, I can swap turbines. Easy. This solves the problem of sizing a turbo (what's old is new?). The only thing I will need to figure out is the compressor inlet boss. I earlier had machined off a Corvair F compressor inlet (triangle shape) to bolt an aluminum disc to to serve as a mounting surface. This one is circular and I don't know if there is enough wall width to serve as a mounting flange if I likewise machine it down.
I've put a good deal of thought on fuel management but this is as far as I can go today. Discussion will have to wait until next time. Hamilton EFI is a wish-list item, but a carb is still on the table. Projects must sometimes bend to the demands on resources, time, and other priorities.
Robert -
My hope is that you will still be available to give valuable guidance when needed. 2021 will have to be the year that one of our projects comes in for some sort of landing! This point was poignantly made clear this weekend when I was at a Saturday "wrench-a-thon" for the Gulf Coast Binders. A couple of older members noted that for some of us, time is
not on our side to do the things we want to do.
