"Space GhoST"- single turbo ST build

[TMac]

I'll cover all that over the next week or so, but I'm going for a street car. So primarily trying to emphasize a 93 octane gasoline build with enough headspace for e85 and over 850hp. I'll go over the math (try to keep it simple), and explain everything including the technical reasons I made the choices I did. Should be informative. It will also cover intake, exhaust, hot/cold side piping, sizing, and integration with the vacuum wastegates. I'm sure three or four people will read it.

 

[TMac]

BTW, @MattJ716 is going to do us all a big favor and handle editing upcoming graphs. Thanks Matt.

 

[Dale5403]

A big thank you @MattJ716 for helping @TMac with this project.

 

[Cruising68]

Definitely following the build thread!!

 

[Cruising68]

Never in my life have I ever posted a build thread. I never was interested in sharing information. Some of it is in my early days of street racing. My cars were always sleepers- and I enjoyed having them perceived that way. I also enjoy the engineering aspect- nothing wrong with a bolt-on, but I start with looking at the vehicle as a system and then figuring out exactly what to change. I'm sure it'll be controversial and informative!

A custom build with hand chosen components, assuming chosen properly, should always outperform a "bolt on" kit IMO. If you do the math right and can get the tune right it should be awesome.

 

[Dale5403]

So your looking for over 850HP (WOW). What rear cross member are you working with? Or differential brace?

 

[Blown F-150]

I'll cover all that over the next week or so, but I'm going for a street car. So primarily trying to emphasize a 93 octane gasoline build with enough headspace for e85 and over 850hp. I'll go over the math (try to keep it simple), and explain everything including the technical reasons I made the choices I did. Should be informative. It will also cover intake, exhaust, hot/cold side piping, sizing, and integration with the vacuum wastegates. I'm sure three or four people will read it.

I’ll definitely be one that’s reading it, should be good stuff.

I know what I’m putting together to get my 3.5 eco to 700whp (currently just around 530whp) and that’s with chosen turbos that I’m purposely going to smaller A/R turbine housings to spool earlier than they originally would. There are other install and application benefits to the turbine housings.

But being in a truck that tows and goes off-road, it’s a different approach.


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[TMac]

So your looking for over 850HP (WOW). What rear cross member are you working with? Or differential brace?

I'm not looking for 850 hp, that would take a lot more pump and injection than you can probably find currently. I'm looking to show how to get there with all the right airflow mods to make it possible. This isn't some 1000 hp dream build with no budget. I have very clear goals and will post where the limits are. I have a 2020 with the 4 bolt diff, and I'm going to talk about limiting torque at low RPM to save the driveline.

 

[TMac]

I’ll definitely be one that’s reading it, should be good stuff.

I know what I’m putting together to get my 3.5 eco to 700whp (currently just around 530whp) and that’s with chosen turbos that I’m purposely going to smaller A/R turbine housings to spool earlier than they originally would. There are other install and application benefits to the turbine housings.

But being in a truck that tows and goes off-road, it’s a different approach.


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I'll be discussing A/R and turbine housings. After all, there isn't any reason to go a custom turbo route if you're not considering various A/R housings. I hope you take this the right way, but remember that load (like towing) increases turbine energy. Which means you might not want as small an A/R as some might believe for that type of application.

 

[TMac]

So this is outside the realm of the build thread information, but since this is for questions, let me follow up my last post to @Blown F-150 on A/R as regards load. Almost anyone with a boost gauge has figured out that when sitting at idle (low load), you can rev the engine up with almost no boost, right? In fact, to build boost, you may have to brake torque the engine (increase load). Why is this? It isn't about the turbo, that's a fixed mechanical device. It's about cam timing as it relates to cylinder pressure.

We'll leave the actual math out, but we'll just simulate it. The cylinder injests 14.5 psi (1 bar) of air assuming 100% VE. We then compress it at 10:1 compression ratio. This gives us (not actual math, just simulation to make it easy to visualize) 145 psi. Now we ignite it on the power stroke. This gives us 1200 psi (not actual math, just an approximation). Let's say the exhaust valve opens at 35 degrees BBDC (before bottom dead center) while the pressure has dropped to 100 psi since there is no load (nothing inhibiting pressure dissipation on the downstroke) and out it goes past the turbine.

Now let's increase the load by going uphill, or towing, or brake torquing the engine. In this case, the pressure when the exhaust valve opens is not 100 psi, it's higher due to the resistance (load) of the downstroke of the piston. Depending on that load, we may now have 200 psi when the valve opens- in effect, doubling the amount of energy driving the turbine.

This increases the speed of the turbine and compressor- and thus the boost pressure. And what does this actually mean to you? Despite a dyno chart at some particular load that you think might advise you of the A/R required to reach boost at a particular RPM, you might actually need a larger turbine A/R ratio on an application is that under a higher load.

 

[Blown F-150]

I'll be discussing A/R and turbine housings. After all, there isn't any reason to go a custom turbo route if you're not considering various A/R housings. I hope you take this the right way, but remember that load (like towing) increases turbine energy. Which means you might not want as small an A/R as some might believe for that type of application.

Yup, totally get what you’re saying. There are a bunch of factors though, tuning specifically for towing included and I’m working directly with a well known engineer in the industry for F150 ecos in the aftermarket. He is very familiar with my specific truck and goals which help determine the approach.

Anyway, I’m pulling your thread in an un-intended direction, I’ll catch up on you recent posts soon.


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[twin001]

Badass! This is going to be awesome to follow!

 

[UNBROKEN]

I'm going to talk about limiting torque at low RPM to save the driveline.

In the early high performance diesel days when we started cracking the 1000hp mark we were killing transmissions on a weekly basis…then along came some real tuning capabilities and we learned fast to limit the low end torque to keep things alive. I do NOT miss driveway input shaft swaps. lol
One of my first 4 figure trucks would make almost 2000 ft lbs at like 1500rpm. It was just constant driveline destruction.

 

[TMac]

Thanks again to @MattJ716 I have finally finished post #3.

For anyone following, we have abandoned the dual thread (questions). Feel free to remark on this thread.

 

[Dale5403]

Still following. I've been wondering how it's going.

 

[TMac]

Due to RSV and a resulting complicating factor, I've been down for a bit. Still not 100%, but getting better!

 

[TMac]

For those who posted content on the now defunct "questions" thread, I've asked the admin to move those to this thread so as to not lose any content.

As you'll see from post #3 (just completed), it's a pretty technical subject so has taken a bit longer than I expected.

 

[Dale5403]

Due to RSV and a resulting complicating factor, I've been down for a bit. Still not 100%, but getting better!

Get well soon. I've heard that RSV can be pretty rough and it's been spreading.

 

[UNBROKEN]

Just because I may have missed it…or forgotten…have you considered finding a pair of smaller chargers that fit the bill and having some adapters machined to bolt to the head? Seems like it would cut way down on fab work if the exhaust was largely unchanged as well as the lay-out of the intake tubing.

 

[TMac]

Looked at the idea, and you're right, it'll play...however, you still have to fab up the downpipes, charge pipes, intake pipes, and build head adapters to a T25 or V-Band inlet. The turbo centerlines would definitely have to be offset, so there would to need to be some fab work put into applying that to the piping. And wastegates? A whole 'nother kettle of fish.

Part of the fun is also to post something instructional- like a deep dive into the potential and how to achieve it. Costwise? The turbo that fits this engine perfectly (in my mind) is under $2200 . Let's say we went with two G25-550s- around $2500 each. That's before all of the other fab work- it gets pricey in a hurry still leaving everything else on the intake and exhaust side.

If one considers the existing bolt-on stuff: exhaust, intake, charge pipes, downpipes, etc, etc with no access to a compressor map, turbine chart, or turbo RPM this is a more disciplined approach.

But I get it, if someone offered a bolt-on setup with known chargers and the accompanying parts for some type of reasonable price, it'd make perfect sense.