Hello! Im starting a new engine build and am planning on adding a twin turbo set up to it. I am reading through your newbie section so I wont ask any questions besides "what do you think?".

To get to it, the engine in question is a 1989 Ford Thunderbird SC 3.8 V6. Block and heads have been machined for use with MLS gaskets, bowls have been worked to smooth out its transitions, and ring gaps have been opened and matched to .027 top (factory is .025). Not a huge difference but I went with .007 per inch of bore due to my planned boost levels. If this should be adjusted please let me know. Lower ring is .023.

The stock M90 Eaton has been removed and sold. Though I like the sound I cant get past the parasitic draw over them. So I am planning, an honestly weird, set up.

The plan is to place the turbos ontop of the engine. Not hang them off the side. I am still using the blower intake manifold, which is flat with an opening in the rear for its air intake.

There is no benefit to me sticking them here. Infact it raises the center of gravity and will give me a head ache fabbing out the hot and cold sides. But I think itll look killer.

I after reading your thread on how to read maps, I believe Im looking for a turbo thats happy in the 2.6pr 40lb/min area. But Im still reading and trying to understand that. And then see about converting from a single to a twin, if there even is. Hoping to not have a lot of spool, plus the placement I want dictates small turbos anyway.

Im hoping to achive 400bhp.

So like I said early, I wont ask any questions besides... What do you think?

Here are some photos of the engine as it is currently during assembly and car its going into.
Also adding how I want the turbos positioning to look.

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I think skip the funny turbo placement. The engine you pictured is an AMG Mercedes, they come with the turbos in that location from the factory, its the only choice on that engine. Instead focus on a good, clean install, and making sure everything works well, heat is in check, and it is serviceable. The first build is tough, make it as easy on yourself as possible. As far as your turbo selection, single s256 or s362.

You will need a standard intake manifold, or a custom hat to go over your SC manifold. The SC manifold is a poor choice, very short runners are going to want to be at an RPM you won't achieve, without a blower it is going to be a dog at the low RPM ranges.

 

Can someone more knowledgeable comment on the 0.023" second ring gap - I thought it should be bigger?

I thing the Mercedes is a "hot vee" engine with exhaust ports in the vee. It looks killer but you want the turbines close to the headers if possible.

 

the smaller gap on the bottom is old school and most likely isnt a problem up to XX hp.
The new common is same gaps or slightly bigger lower gap. Reason is so cylinder pressure doesnt get trapped between the rings and cause problems.

 

Put them up top if you want. Its really no different than other setups in terms of hot side length. Duramax, and Powerstroke engines have been doing it for years.

 

Placement could be an issue though as I do agree with the others about wanting a longer runner intake. Maybe compound the turbos and blower? That would be different.

 

Thank you all for the replies.
Yes, the engine I have pictured is an AMG m176/7/8 series Hot V v8. So the turbos on that engine are purposely designed to be there so its as compact as possible.

I understand the issues Ben has brought up. The SC intake manifold doesnt really have any runners period. So itll want to run extremely high rpms if not under boost. The intake inlet I have already solved, cutting apart the supercharger inlet plenum and welding a flange to fit the intake inlet.

And I know I am making this a lot more complicated than it has to be, especially for my first turbo build.

But, I love challenges. This specific car the engine is planned for originally started as a cheap car challenge, with a chassis rebuild, 302 EFI swap, and manual swap within the month of July 2019 for less than $1000. So now I want to further it. And be a bit radical.

I have it stuck in my head to build this engine with the turbos placed over the SC intake. Admittedly, this is not an original idea of mine. I saw someone do it with a big single, and it was a dog, not spooling till 4200rpm with an engine redline at 5000. But, if Im remembering it correctly, it was off a diesel truck. So that might be another reason. I have included a photo of that car.

I essentially want to take that idea, and make it more practical. With smaller parallel twins. Im thinking the lines of TDO4s but I have yet to find their compressor maps.

And thats true about the diesels, I had forgotten about them somehow.

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Well I might have to change my game plan after all.

From my calculations, which may be wrong since Im learning as I go, I actually need a 3.7pr, 40lb/min single and a 3.7pr 20lb/min with twins.

My original 2.6 pr was still taking into account the blowers 12psi.

From what I see, there are no turbos that can get to that 3.7 pr 20lb/min for twins. And very few that can do the 40lb/min thatll actually spool at a reasonable rpm.

The compound boost idea with the blower is a good one, very similar to the Hellion Hellraiser kit, and one I might have to do. Only issue with that is Ive already sold the M90. So Ill either have to find another one, or try to convert another blower. I had thoughts of taking a Jag M122 and converting it. Might have to do that sooner than later.

As I move forward I will try to update. I dont want to be another new guy who just shows up and disappears.

 

I'm guessing your math could be wrong, 3.7 is roughly 40psi

 

Yeah Im definitely off then lol. I think Ill need about 26psi to get to my power goal of 400crank.
So 1.8PR then? Thats more doable.

These motors made 210bhp at 12psi with the Eaton. Granted Eaton M90s require (if I remember correctly) 60 horse just to turn them at boost.

 

26psi is roughly 2.7 pr which is about right with a 3.8 that makes 150ish hp na. Some mods to get na hp up would help a lot. A cam, and/or porting would go a long way.

 

1. Wherever you put the turbochargers, make sure you can easily fit a large intercooler, if this is a street / traffic setup especially.

2. You have to account for pipe length inefficiency, which include intercooler volume and sharp turns. So for example if you have a 40lb/min turbo and a largeish intercooler, the turbo as a pump produces what engineers call pump head, and the intercooler will take a chunk off that. So 40lb/min quickly becomes 38lb/min or so. Then any inefficiency in the pipe length, diameter, corners etc.. will take additional from that, quickly you are down to 35lb/min worth of pump flow rate, for example, which will put lets say 280~rwhp to the tire give or take if we are being cautious with our estimate of flow. Furthermore, running a 40lb/min turbo off the map at 40lb/min is going to produce some very hot air at peak power, which is counter productive to gasoline fuel, and race gas style fuels, which lack the cooling benefits of Alcohol such as E85 type fuel. So it becomes a dangerous situation when using gasoline style fuels, running the turbo all the way to the edge of the map like that.

What I recommend is, if you want to make 40lb/min of flow rate from the turbo (approx 320rwhp~) you will want a turbo that can support 46 to 48lb/min perhaps 50lb/min minimum. This will account for intercooler pump head pressure drop, pipe inefficiency, and it will also help keep the turbo from running near the absolute edge of the map.

 

I have done bowl work to the heads to smooth out their rough transitions, and have done the same through out the head though I wouldnt say I ported them. I was very cautious because I didnt want to burn through the aluminum.

A cam would be very useful. And is a plan, but later down the line. Ive had the engine for the last year, and was planning on using it in another project (89 SC for auto cross) which planned to use the M90 at 10% over drive, with a front mount IC, the stock SC cam advanced 4°, and water meth injection. That project ended up getting scrapped, literally, so the engine has been sitting in pieces since September. Decided about a month ago to finally do something with it.

Speaking of intercoolers, the one I have is a 3in core, 16in high and 30in wide. In/out on both sides as the plan was to originally use it with the blower.

 

Hello again! Just an update on the engine itself. Short block is together. Will be assembling the heads next.

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looks good. I had a 90 SC myself. Not to take the wind outta your sails , if this is your first turbo project why not just do a single turbo over a hot v . That engine bay has plenty of room especially without the supercharger stuff in the way like the double belt setup ,the intercooler, boost pipes. Keep it simple so you can finish and enjoy your hard work. IMO id get rid of or move the ac compressor to the other side and mount the turbo right there.

 

Im still battling with the overhead turbo idea. More though that proper sized turbos wouldnt look right proportionally in that location, and that running the down pipes would be a royal PITA with the intake elbow also being right there.

Just finished assembling the final head. Will install them over the week end. #ad

 

Looks < performance

 

I like both.

 

Two big issues I can think of:
1) you are trying to copy engines that have the exhaust where traditional intakes are. You will have to run exhaust piping out up and in to the turbo, which will result in a giant web of exhaust pipes on top of the engine.

2) having the turbo that close to the intake opening just means it's harder to run the discharge piping from the compressor to the intercooler then back to the intake. Now you have additional piping on top of the engine.

I think all of that extra piping will defeat the clean aesthetic look you are going after

 

Engine is pretty much together. Have to get new rocker bolts and get the intake, timing cover, and oil pan on. #ad